US20090196073A1 - Switching power supply unit - Google Patents

Abstract

A switching power supply unit capable of simplifying its structure by reducing the number of parts for wiring is provided. A rectifier circuit has a diode inserted between a first secondary winding and a second secondary winding to form a series circuit therewith, and a diode inserted between a third secondary winding and a fourth secondary winding to form a series circuit therewith. A smoothing circuit has a first choke coil inserted between an input section connected to a center tap and an output terminal, and a second choke coil inserted between an input part connected to a junction point and an output terminal. A first path and a second path are formed of a wiring member made of a single sheet metal, and a third path and a fourth path are formed of a wiring member made of another sheet metal.

Description

• This is a Division of application Ser. No. 11/512,100 filed Aug. 30, 2006. The disclosure of the prior application is hereby incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to a switching power supply unit in which an input AC voltage obtained by switching operation of an input direct current voltage is transformed by a transformer, then the transformed output AC voltage is rectified and smoothed to be outputted as an output direct current voltage.
• 2. Description of the Related Art
• Hitherto, various types of switching power supply units have been proposed and provided for practical use. As disclosed in Japanese Laid-Open Patent Publication No. 2002-369528 and Japanese Laid-Open Patent Publication No. 2001-314080, one of them is of a type in which an input direct current voltage from a high voltage battery is switched to an input AC voltage by switching operations of a switching circuit connected to an input winding of a transformer, the obtained input AC voltage then being input into an input winding of the transformer to be converted into an output AC voltage, then the converted output AC voltage being taken out from an output winding of the transformer. The voltage appearing in the output winding in association with such switching operation of the switching circuit is then rectified by a rectifier circuit, the rectified voltage then being converted into an output direct current voltage by a smoothing circuit to be output.
SUMMARY OF THE INVENTION
• In a switching power supply unit of this kind, a rectifier circuit is configured of two rectifier devices arranged between a secondary winding of the transformer and wiring of the smoothing circuit, for example, so as to separately rectify each of the half wave periods of the output AC voltages supplied from the transformer. That is, the secondary winding of the transformer and the wiring of the smoothing circuit are formed of a separate wiring, respectively, and large number of parts is needed for wiring. Thereby, there is such a problem that the structure is intricate.
• In addition, this kind of switching power supply unit has another problem of being easily influenced by the noise from the outside because of a long wiring of the secondary side of the transformer, or of being hardly accommodated compactly within an electronic equipment if the rectifier circuit and the smoothing circuit connected to the secondary side of the transformer are arranged vaguely without any particular vision.
• In view of the drawbacks of the invention, it is desirable to provide a switching power supply unit capable of simplifying its configuration by reducing the number of parts of wiring. Further, it is desirable to provide a switching power supply unit that is hardly influenced by the noise from outside. Furthermore, it is desirable to provide a switching power supply unit capable of being accommodated compactly within electronic equipment.
• According to a first embodiment of the present invention, there is provided a switching power supply unit including a switching circuit, a transformer, a rectifier circuit, and a smoothing circuit. The switching circuit is an inverter circuit which converts a DC input voltage into an AC voltage. The transformer has a primary winding connected to the switching circuit, and a first secondary winding, a second secondary winding, a third secondary winding and a fourth secondary winding. The rectifier circuit has a first rectifier device and a second rectifier device. The first rectifier device is inserted between the first secondary winding and the second secondary winding to form a series circuit therewith, and the second rectifier device is inserted between the third secondary winding and the fourth secondary winding to form a series circuit therewith. The smoothing circuit has a first input end, a second input end, a first output end, and a second output end. The first input end is connected to a junction between the second secondary winding and the third secondary winding. The second input end is commonly connected to a first end portion which is an end portion of the fourth secondary winding on a side opposite to the second rectifier device, and to a second end portion which is an end portion of the first secondary winding on a side opposite to the first rectifier device. The first output end and the second output end are provided corresponding to the first input end and the second input end, respectively.
• In the first embodiment, a direct current voltage inputted into the switching circuit is converted into an AC voltage in the switching circuit, then the converted AC voltage is transformed by the transformer and is outputted to the rectifier circuit. Here, since the rectifier circuit is equivalent to a rectifier circuit which is configured by connecting a first rectifier device between a second secondary winding and a junction and by connecting a second rectifier device between a third secondary winding and the junction, the AC voltage transformed by the transformer is rectified in the same operation as the equivalent circuit, and then smoothed in the smoothing circuit to be outputted from the first output end and the second output end.
• Here, in the above-mentioned equivalent circuit, the secondary winding of the transformer and wiring of the smoothing circuit are connected via the rectifier device. That is, the secondary winding of the transformer and wiring of the smoothing circuit are formed of a separate wiring, respectively. On the other hand, in the first embodiment, the secondary winding of the transformer and wiring of the smoothing circuit are connected in such a way that they are not divided by the rectifier device while maintaining the rectification function held by the above-mentioned equivalent circuit. With such a configuration, it is possible to form the secondary winding of the transformer and wiring of the smoothing circuit with a common wiring.
• For example, a first wiring member in a shape of plate constitutes a first path and a second path. Here, the first path is a path from an end portion of the second secondary winding on a side of the first rectifier device to the first output end via the junction between the second secondary winding and the third secondary winding and via the first input end, and a second path is a path from an end portion of the third secondary winding on a side of the second rectifier device to the first output end via the junction between the second secondary winding and the third secondary winding and via the first input end. On the other hand, a second wiring member in a shape of plate constitutes a third path and a fourth path. Here, the third path is a path from an end portion of the first secondary winding on a side of the first rectifier device to the second output end via the second end portion and via the second input end, while the fourth path is a path from an end portion of the fourth secondary winding on a side of the second rectifier device to the second output end via the first end portion and via the second input end to the second output end.
• According to a second embodiment of the present invention, there is provided a switching power supply unit including a switching circuit, a transformer, a rectifier circuit, and a smoothing circuit. The switching circuit is an inverter circuit which converts a DC input voltage into an AC voltage. The transformer has a primary winding connected to the switching circuit, and a first secondary winding and a second secondary winding. The rectifier circuit has a first rectifier device and a second rectifier device. The first rectifier device is inserted between the first secondary winding and the second secondary winding, and one end of the second rectifier device is connected to a first end portion which is an end portion of the second secondary winding on a side opposite to the first rectifier, while the other end of the second rectifier device is connected to a second end portion which is an end portion of the first secondary winding on a side opposite to the first rectifier. The smoothing circuit has a first input end, a second input end, a first output end, and a second output end. The first input end is connected to a junction between the first secondary winding and the first rectifier device. The second input end is commonly connected to the first end portion and one end of the second rectifier device. The first output end and the second output end are provided corresponding to the first input end and the second input end, respectively.
• In the second embodiment, a direct current voltage inputted into the switching circuit is converted into an AC voltage in the switching circuit, then the converted AC voltage is transformed by the transformer and is outputted to the rectifier circuit. Here, since the rectifier circuit is equivalent to a rectifier circuit that is configured by connecting a second rectifier device between a first secondary winding and a junction, the AC voltage transformed by the transformer is rectified in the same operation as the equivalent circuit, and then smoothed in the smoothing circuit to be outputted from the first output end and the second output end.
• Here, in the above-mentioned equivalent circuit, the secondary winding of the transformer and wiring of the smoothing circuit are connected via the rectifier device. That is, the secondary winding of the transformer and wiring of the smoothing circuit are formed of a separate wiring, respectively. On the other hand, in the second embodiment, the secondary winding of the transformer and wiring of the smoothing circuit are connected in such a way that they are not divided by the rectifier device while maintaining the rectification function held by the above-mentioned equivalent circuit. With such a configuration, it is possible to form the secondary winding of the transformer and wiring of the smoothing circuit with a common wiring.
• For example, a path from the second end portion via the junction and the first input end to the first output end may be formed of a first wiring member in a shape of plate, while the second secondary winding may be formed of a second wiring member in a shape of plate.
• According to a third embodiment of the present invention, there is provided a switching power supply unit including a switching circuit, a transformer, a rectifier circuit, and a smoothing circuit. The switching circuit is an inverter circuit which converts a DC input voltage into an AC voltage. The transformer has a primary winding connected to the switching circuit, and a first secondary winding and a second secondary winding connected to each other. The rectifier circuit has a first rectifier device and a second rectifier device. The first rectifier device is inserted between the ground and a first end portion which is an end portion of the second secondary winding on a side opposite to the first secondary winding, and the second rectifier device is inserted between the ground and a second end portion which is an end portion of the first secondary winding on a side opposite to the second secondary winding. The smoothing circuit has a first input end, a second input end, a first output end, and a second output end. The first input end is connected to a junction between the first secondary winding and the second secondary winding. The second input end is commonly connected to the first rectifier device, the second rectifier device and the ground. The first output end and the second output end are provided corresponding to the first input end and the second input end, respectively.
• In the third embodiment, a direct current voltage inputted into the switching circuit is converted into an AC voltage in the switching circuit, then the converted AC voltage is transformed by the transformer and is outputted to the rectifier circuit. Here, since the rectifier circuit is equivalent to a rectifier circuit that is configured by connecting a first rectifier device between a second secondary winding and a junction, and by connecting a second rectifier device between a first secondary winding and a junction, the AC voltage transformed by the transformer is rectified in the same operation as the equivalent circuit, and then smoothed in the smoothing circuit to be outputted from the first output end and the second output end.
• Here, in the above-mentioned equivalent circuit, the secondary winding of the transformer and wiring of the smoothing circuit are connected via the rectifier device. That is, the secondary winding of the transformer and wiring of the smoothing circuit are formed of a separate wiring, respectively. On the other hand, in the third embodiment, the secondary winding of the transformer and wiring of the smoothing circuit are connected in such a way that they are not divided by the rectifier device while maintaining the rectification function held by the above-mentioned equivalent circuit. With such a configuration, it is possible to form the secondary winding of the transformer and wiring of the smoothing circuit with a common wiring.
• For example, a first wiring member in a shape of plate constitutes a path from the secondary end portion to the first output end via the junction between the first secondary winding and the second secondary winding and via the first input end, and a second wiring member in a shape of plate constitutes a second secondary winding. Or, the first wiring member in a shape of plate constitutes a path from the first end portion to the first output end via the junction between the first secondary winding and the second secondary winding and via the first input end, and the second wiring member in a shape of plate constitutes the first secondary winding.
• According to a fourth embodiment of the present invention, there is provided a switching power supply unit including, on a substrate: a transformer transforming and outputting an AC voltage; a rectifier circuit rectifying the AC voltage supplied from the transformer; and a smoothing circuit smoothing and outputting the voltage rectified by the rectifier circuit. The transformer is disposed adjacent to both of the rectifier circuit and the smoothing circuit. The rectifier circuit is mounted on the substrate with an intermediate base in between in a manner of bare chip mounting.
• In the fourth embodiment, since the transformer is disposed adjacent to both of the rectifier circuit and the smoothing circuit and the rectifier circuit is mounted on the substrate with an intermediate base in between in a manner of bare chip mounting, it is possible to shorten wiring connected to the secondary side of the transformer.
• Here, in a case where the switching power supply unit is provided with a switching circuit which converts a DC input voltage into an AC voltage to output the converted AC voltage to the transformer, it is possible to mount the switching circuit on the substrate with an intermediate base in between in a manner of bare chip mounting. Further, it is also possible to mount the switching circuit and the rectifier circuit integrally on the substrate using with an intermediate base in between in a manner of bare chip mounting.
• According to a fifth embodiment of the present invention, there is provided a switching power supply unit including, on a substrate: a transformer transforming and outputting an AC voltage; a rectifier circuit rectifying the AC voltage supplied from the transformer; and a smoothing circuit smoothing and outputting the voltage rectified by the rectifier circuit. The rectifier circuit, the transformer, and the smoothing circuit are arranged in a line in this order.
• In the fifth embodiment, since the rectifier circuit, the transformer, and the smoothing circuit are arranged in a line in this order, the overall configuration becomes elongated.
• According to the first, second and third embodiment, since the secondary winding of the transformer and wiring of the smoothing circuit are formed of a common wiring, it is possible to reduce the number of parts thereof, and the structure can be simplified.
• According to the fourth embodiment, the transformer is disposed adjacent to both of the rectifier circuit and the smoothing circuit and the rectifier circuit is mounted on the substrate with an intermediate base in between in a manner of bare chip mounting. Thereby, it is possible to shorten wiring connected to the secondary side of the transformer. Thereby, wiring resistance and an inductance component can be reduced while influence of noise from the outside can become less. As a result, ringing, surge, and power loss can be reduced.
• According to the fifth embodiment, since the rectifier circuit, the transformer, and the smoothing circuit are arranged in a line in this order, the overall configuration can be made elongated. Thereby, even in a case where a free space in the electronic equipment is limited, it is possible to accommodate the switching power supply unit compactly in electronic equipment.
• Other and further objects, features and advantages of the invention will appear more fully from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a circuit diagram of a switching power supply unit according to a first embodiment of the present invention.
• FIG. 2 shows a configuration of the switching power supply unit shown inFIG. 1.
• FIG. 3 is a circuit diagram of a switching power supply unit according to a comparative example.
• FIG. 4 shows a configuration of the switching power supply unit shown inFIG. 3.
• FIG. 5 is a circuit diagram of a switching power supply unit according to a modification.
• FIG. 6 shows a configuration of the switching power supply unit shown inFIG. 5.
• FIG. 7 is a circuit diagram of a switching power supply unit according to another modification.
• FIG. 8 shows a configuration of the switching power supply unit shown inFIG. 7.
• FIG. 9 is a circuit diagram of a switching power supply unit according to still another modification.
• FIG. 10 shows a configuration of the switching power supply unit shown inFIG. 9.
• FIG. 11 is a circuit diagram of a switching power supply unit according to still another modification.
• FIG. 12 shows a configuration of the switching power supply unit shown inFIG. 11.
• FIG. 13 is a circuit diagram of a switching power supply unit according to a second embodiment of the present invention.
• FIG. 14 shows a configuration of the switching power supply unit shown inFIG. 13.
• FIG. 15 is a circuit diagram of a switching power supply unit according to a modification.
• FIG. 16 shows a configuration of the switching power supply unit shown inFIG. 15.
• FIG. 17 is a circuit diagram of a switching power supply unit according to another modification.
• FIG. 18 shows a configuration of the switching power supply unit shown inFIG. 17.
• FIG. 19 is a circuit diagram of a switching power supply unit according to sill another modification.
• FIG. 20 shows a configuration of the switching power supply unit shown inFIG. 19.
• FIG. 21 is a circuit diagram of a switching power supply unit according to still another modification.
• FIG. 22 shows a configuration of the switching power supply unit shown inFIG. 21.
• FIG. 23 is a circuit diagram of a switching power supply unit according to a third embodiment of the present invention.
• FIG. 24 shows a configuration of the switching power supply unit shown inFIG. 23.
• FIG. 25 is a circuit diagram of a switching power supply unit according to a comparative example.
• FIG. 26 shows a configuration of the switching power supply unit shown inFIG. 25.
• FIG. 27 shows a configuration of a switching power supply unit according to another modification.
• FIG. 28 shows a configuration of a switching power supply unit according to still another modification.
• FIGS. 29A and 29B are circuit diagrams about various modifications of an inverter circuit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The present invention will be more fully understood from the following description of preferred embodiments when reference is made to the accompanying drawings.
First Embodiment
• FIG. 1 is a circuit diagram of a switching power supply unit according to a first embodiment of the present invention, andFIG. 2 shows a configuration of the switching power supply unit ofFIG. 1. The switching power supply unit functions as a DC-DC converter for converting a high DC input voltage Vin supplied from a high-voltage battery (not shown) to a lower DC output voltage Vout, and the converted DC output voltage Vout is supplied to a load (not shown). As mentioned later, the secondary side of the switching power supply unit is of a center tap type.
• The switching power supply unit includes: an inverter circuit1 (a switching circuit) and a smoothingcapacitor2 provided between a primary-side high voltage line L1H and a primary-side low voltage line L1L; a three windingtransformer4 including a primary winding42 andsecondary windings43 and44; and aninductor3 for resonance provided between theinverter circuit1 and thetransformer4. An input terminal T1 is provided on the primary-side high voltage line L1H and an input terminal T2 is provided on the primary-side low voltage line L1L, respectively, and the input terminals T1 and T2 are connected to the output terminal of the high voltage battery.
• The switching power supply unit further includes arectifier circuit5 and a smoothingcircuit6 located on the secondary side of thetransformer4. An output terminal T3 (a first output end) is provided in an output line LO, which is a line on the high voltage side of the smoothingcircuit6, and an output terminal T4 (a second output end) is provided in a ground line LG, which is a line on the low voltage side of the smoothingcircuit6, respectively. And the output terminals T3 and T4 are connected to the input terminal of the load.
• Theinverter circuit1 is a single phase inverter circuit which converts a DC input voltage Vin outputted from the high voltage battery into a single phase AC voltage of rectangular wave. Theinverter circuit1 is a switching circuit of a full bridge type configured by making a full bridge connection of four switchingelements11,12,13, and14 which are driven with switching signals transmitted from a control circuit (not shown) respectively. Examples of the switching elements to be used are MOS-FETs (Metal Oxide Semiconductor-Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), or the like.
• The switchingelement11 is disposed between one end of the primary winding42 of thetransformer4 and the primary-side high voltage line L1H, and the switchingelement12 is disposed between one end of the primary winding42 and the primary-side low voltage line L1L. The switchingelement13 is disposed between one end of theinductor3 for resonance which is connected to the other end of the primary winding42 and the primary-side high voltage line L1H, and the switchingelement14 is disposed between one end of theinductor3 for resonance and the primary-side low voltage line L1L.
• With the foregoing configuration, current in theinverter circuit1, current flows into a first current path, which is from the primary-side high voltage line L1H through the switchingelement11, the primary winding42, theinductor3 for resonance, the switchingelement14 and then to the primary-side low voltage line L1L in this order, when the switchingelements11 and14 are turned ON. On the other hand, current flows into a second current path, which is from the primary-side high voltage line L1H through the switchingelement13, theinductor3 for resonance, the primary winding42, the switchingelement12 and then to the primary-side low voltage line L1L in this order, when the switchingelements12 and13 are turned ON.
• Theinductor3 for resonance forms a resonance circuit with at least one of parasitic capacitances of the switchingelements11,12,13, and14 so as to be able to reduce the power loss due to ON/OFF operation of the switching elements by use of the resonance characteristics. Theinductor3 for resonance may be configured by arranging an actual coil component. Or, in substitution for that (or in addition to that), theinductor3 may be configured using a series inductance including a leakage inductance (not shown), a wiring, etc. of thetransformer4.
• Thetransformer4 is a magnetic device in which a primary winding42 andsecondary windings43 and44 mutually connected in series are magnetically coupled each other by winding around amagnetic core41 in such a way that all the windings have a polarity of the same direction each other. Thetransformer4 is a step-down transformer, in which each of the number of turns of the secondary winding43 and the secondary winding44 are set to be less than that of the primary winding42. The degree of voltage drop is determined by the turn ratio between the primary winding42 and thesecondary windings43 and44.
• Themagnetic core41 has a magnetic path of a figure of “8”, and is configured of, for example, amagnetic core41A and amagnetic core41B, each of which has a figure of “E”, in which themagnetic core41A is mounted on a substrate S with conductive patterns (not shown) while themagnetic core41B is mounted on themagnetic core41A.
• The primary winding42 is disposed on the primary side of thetransformer4 and is connected to theinverter circuit1 so that the direction of current flowing into the primary winding42 itself changes in accordance with the operation of theinverter circuit1. Specifically, one end of the primary winding42 is connected to the junction between the switchingelement13 and the switchingelement14 via theinductor3 for resonance. The other end of the primary winding42 is connected to the junction point of the switchingelement11 and the switchingelement12.
• The secondary winding43 is configured of a first secondary winding43A and a second secondary winding43B respectively connected to the ends of a below-mentioneddiode51 in series. The secondary winding43 is formed in such a way that the first secondary winding43A is wound around themagnetic core41 by half a turn while the second secondary winding43B is wound around themagnetic core41 by half a turn so that they can be cooperatively wound around themagnetic core41 just by one turn as a whole.
• The secondary winding44 is configured of a third secondary winding44A and a fourth secondary winding44B respectively connected to the ends of a below-mentioneddiode52 in series. The secondary winding44 is formed in such a way that the third secondary winding44A is wound around themagnetic core41 by half a turn while the fourth secondary winding44B is wound around themagnetic core41 by half a turn so that they can be cooperatively wound around themagnetic core41 just by one turn as a whole.
• An end portion of the second secondary winding43B on a side opposite to thediode51, and an end portion of the third secondary winding44A on a side opposite to thediode52, are mutually connected at a center tap C (a junction), and the center tap C is connected to an input end In1 (a first input end) via the output line LO. On the other hand, an end portion A (a first end portion) of the fourth secondary winding44B on a side opposite to thediode52, and an end portion B (a second end portion) of the first secondary winding43A on a side opposite to thediode51, are mutually connected at a junction point D, and the junction point D is connected to an input end In2 (a second input end) via the ground line LG. That is, the secondary side of thetransformer4 is of a center tap connection type.
• The substrate S is made of an aluminum die-casting, for example, and may be electrically connected to the ground or may be electrically isolated from the ground.
• Therectifier circuit5 is a single-phase full-wave rectifier including a pair of rectifier diodes51 (a first rectifier device) and52 (a second rectifier device). The anode of therectifier diode51 is connected to one end of the first secondary winding43A of thetransformer4, and the cathode of therectifier diode51 is connected to one end of the second secondary winding43B of thetransformer4. The anode of therectifier diode52 is connected to one end of the fourth secondary winding44B of thetransformer4, and the cathode of therectifier diode52 is connected to one end of the third secondary winding43A of thetransformer4.
• Therectifier circuit5 is equivalent to arectifier circuit105 of cathode common connection type which is configured by inserting adiode51 between a secondary winding43 and a center tap C, and inserting adiode52 between a secondary winding44 and the center tap C, as shown inFIG. 3. Therefore, similarly to therectifier circuit105 shown inFIG. 3, the circuit including therectifier circuit5 rectifies the separate half wave periods of the AC output voltages VO1 and VO2 of thetransformer4 by thediodes51 and52 respectively to output the rectified voltages from the center tap C and the junction point D.
• The smoothingcircuit6 includes amagnetic core61, achoke coil62 and a smoothingcapacitor63, and smoothes the rectified voltage inputted into the first input end In1 and the second input end In2 to generate a DC output voltage Vout. Then, the DC output voltage Vout is supplied from the output terminals T3 and T4 to a load L.
• Themagnetic core61 has a magnetic path formed into a figure of “8” whose center leg is provided with a gap at the midpoint thereof. For example, themagnetic core61 includes amagnetic core61A and amagnetic core61B, each of which is formed into a figure of “E” and is configured by mounting themagnetic core61A on the substrate S and then mounting themagnetic core61B on themagnetic core61A.
• Thechoke coil62 includes afirst choke coil62A and asecond choke coil62B. Thechoke coil62A is formed in such a way that the wiring provided between the first input end In1 and the output terminal T3 is wound around themagnetic core61 by half a turn, while thechoke coil62B is formed in such a way that the wiring provided between the second input end In2 and the output terminal T4 is wound around themagnetic core61 by half a turn, so that thechoke coil62 is wound around themagnetic core61 just by one turn as a whole.
• The smoothingcircuit6 is equivalent to asmoothing circuit106 which is configured by connecting achoke coil62 to an output terminal T3 in series, as shown inFIG. 3. Like in the case of the smoothingcircuit106, the rectified voltage outputted from therectifier circuit5 is smoothed to produce a DC output voltage Vout, then the DC output voltage Vout is outputted to the output terminals T3 and T4.
• Next, the operation of the switching power supply unit having the foregoing configuration will be described. Although a case where theinverter circuit1 is driven by a general switching operation is explained below, it is also possible to drive theinverter circuit1 by zero volt switching operation for example.
• If the switchingelements11 and14 of theinverter circuit1 are turned ON, current flows in the direction from the switchingelement11 to the switchingelement14, thereby a voltage appearing across thesecondary windings43 and44 of thetransformer4 is applied in the opposite direction with respect to thediode52, and in the forward direction with respect to thediode51. For this reason, current flows into the output line LO through the secondary winding43 and thediode51.
• If the switchingelements11 and14 are turned OFF from ON, the voltage appearing across the secondary winding44 of thetransformer4 is applied in the forward direction with respect to thediode52. For this reason, current flows into the output line LO through the secondary winding44 and thediode52.
• Next, if the switchingelements12 and13 are turned ON, current flows in the direction from the switchingelement13 to the switchingelement12, thereby the voltage appearing across thesecondary windings43 and44 of thetransformer4 is applied in the forward direction with respect to thediode52 while applied in the opposite direction with respect to thediode51. For this reason, current flows into the output line LO through the secondary winding44 and thediode52.
• Finally, if the switchingelements12 and13 are turned OFF from ON, the voltage appearing across the secondary winding43 of thetransformer4 is applied in the forward direction with respect to thediode51. For this reason, current flows into the output line LO through the secondary winding43 and thediode51.
• In this manner, the switching power supply unit transforms (step down) a DC input voltage Vin supplied from a high voltage battery to a DC output voltage Vout to supply the transformed DC output voltage Vout to a low voltage battery.
• Next, effects of the switching power supply unit of the present embodiment will be explained as compared with a comparative example.
• In the comparative example, as shown inFIG. 4, the secondary windings (thesecondary windings43 and44) of thetransformer4 and wiring of the smoothingcircuit106 are divided by thediodes51 and52 of therectifier circuit105. That is, the secondary winding of thetransformer4 and the wiring of the smoothingcircuit106 are formed of a separate wiring, respectively, thereby large number of parts is needed for wiring and the structure is intricate. In order to electrically connect such wiring as divided in this way, mutual electrical connection by means of screw fastening, solder or welding, etc. is needed between the wirings extended from each of thediodes51 and52, thesecondary windings43 and44, thechoke coil62 and the output terminals T3 and T4, and the smoothingcapacitor63.
• On the other hand, in the present embodiment, as shown inFIG. 2, afirst path7A from an end portion of the second secondary winding43B on a side connected to thediode51 to the output terminal T3 via the center tap C, and asecond path7B from an end portion of the third secondary winding44A on a side connected to thediode52 to the output terminal T3 via the center tap C, are integrally formed of a wiring member7 (a first wiring member) made of a single sheet metal. Moreover, athird path8A from an end portion of the first secondary winding43A on a side connected to thediode51 to the output terminal T4 via the end portion B, and afourth path8B from an end portion of the fourth winding44B on a side connected to thediode52 to the output terminal T4 via the end portion A, are integrally formed of a wiring member8 (a second wiring member) made of a single sheet metal. That is, the secondary windings (thesecondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of the two sheet metals (thewiring members7 and8). At this time, thediodes51 and52 of therectifier circuit5 are disposed in the vicinity of the end portions of thesewiring members7 and8.
• As described above, according to the present embodiment, since the secondary windings (thesecondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of two sheet metals (wiring members7 and8), the number of parts for wiring can be reduced from four parts to two parts compared with the configuration of the comparative example, and the structure can be simplified.
• In this manner, according to the present embodiment, what is necessary is just to electrically connect thediodes51 and52, thewiring members7 and8, and the smoothingcapacitor63 each other by means of screw fastening, solder or welding, etc. Thereby man-hour requirement for the connecting operation can be reduced. In addition, since the number of junction points of wiring is decreased, generation of heat and power loss caused by the contact resistance in the junction point of wiring can be reduced. Moreover, since occurrence possibility of loosened screw or solder crack is reduced, reliability can be raised.
• In addition, according to the present embodiment, therectifier circuit5, thetransformer4, and the smoothingcircuit6 are arranged in a line in this order while thetransformer4 and the smoothingcircuit6 are disposed adjacent to each other. Further, therectifier circuit5 is mounted on the substrate S with an intermediate base in between in a manner of bare chip mounting. Thereby, since wiring connected to the secondary side of thetransformer4 can be shortened compared with the configuration of the comparative example, wiring resistance and an inductance component can be reduced while influence of the noise from the outside can be reduced. As a result, ringing, surge, and power loss can be reduced.
• It is to be noted that the intermediate base T is made of an insulating material, such as a ceramic, a plastic, or a film. Or, an insulating layer may be provided on the surface of the substrate S instead of the intermediate base T so that bare chip mounting can be carried out via the insulating layer. In this manner of mounting therectifier5 on the substrate S with an intermediate base in between in a manner of bare chip mounting, heat generated in therectifier circuit5 can be efficiently transmitted to the substrate S so that heat dissipation characteristics can be improved. In particular, in a case where the intermediate base T is formed of an insulating film or an insulating layer is provided on the surface of the substrate S instead of the intermediate base T, thermal conductivity to the substrate S is high, and heat dissipation characteristics can be more improved.
• According to the present embodiment, although therectifier circuit5, thetransformer4, and the smoothingcircuit6 are disposed in this order in a line, they may be disposed in such a way that the arrangement direction of thetransformer4 and therectifier circuit5 and the arrangement direction of thetransformer4 and smoothingcircuit6 may cross at right angles, for example. Even in such configuration, thetransformer4 and the smoothingcircuit6 can be disposed adjacent to each other. Therefore, it becomes possible to shorten the wiring connected to the secondary side of thetransformer4. Thereby, wiring resistance and an inductance component can be reduced while influence of the noise from the outside can be reduced. As a result, ringing, surge, and power loss can be reduced.
• In addition, in the present embodiment, since therectifier circuit5, thetransformer4, and the smoothingcircuit6 are arranged in a line in this order, the overall configuration of the switching power supply unit can be made elongated. Thereby, even in a case where a free space in the electronic equipment is limited, it becomes possible to accommodate the switching power supply unit compactly in electronic equipment.
Modification of First Embodiment
• In the above-mentioned first embodiment, thechoke coil62 of the smoothingcircuit6 is formed in such a way that the wiring on the output terminal T3 (the wiring member7) side is wound around themagnetic core61 by half a turn while the wiring on the output terminal T4 (the wiring member8) side is wound around themagnetic core61 by half a turn so that they can be cooperatively wound around themagnetic core61 just by one turn as a whole. However, as shown inFIGS. 5 and 6, the choke coil may be formed in such a way that themagnetic core61 is wound by the wiring only on the output terminal T3 (the wiring member7) side by one turn as a whole.
• In a case where a sufficient magnitude of inductor of thechoke coil62 is hardly obtainable just by one turned winding, as shown inFIGS. 7 and 8, there may be provided a two-turnedchoke coil162 instead of thechoke coil62. Thechoke coil162 includes afirst choke coil162A formed by winding around themagnetic core61 with the wiring on the output terminal T3 (wiring member7) side by one turn, and asecond choke coil162B formed by winding around themagnetic core61 with the wiring on the output terminal T4 (wiring member8) side by one turn. As described above, even in the case where the winding number of thechoke coil162 is two turns, it is possible to form each of thewiring members7 and8 by a single sheet metal, respectively. In this manner, as compared with the configurations in the past, the number of parts for wiring can be reduced from four parts to two parts similarly to the above-mentioned embodiment so that the structure can be simplified.
• In addition, according to the above-mentioned first embodiment, an equivalent circuit on the secondary side of thetransformer4 is configured of an anode common connection type. However, as shown inFIGS. 9 and 10 orFIGS. 11 and 12, equivalent circuits on the secondary side of thetransformer4 may be configured of a cathode common connection type.
Second Embodiment
• FIG. 13 is a circuit diagram of a switching power supply unit according to a second embodiment of the present invention, andFIG. 14 shows a configuration of the switching power supply unit ofFIG. 13. The switching power supply unit is different in the configuration of the secondary winding of thetransformer4 and in the configuration of therectifier circuit5 as compared with the above-mentioned first embodiment. Then, hereinafter, points different from the above-mentioned first embodiment will be mainly explained, and description of the configuration, operation, and effect which are common to the above-mentioned first embodiment will be suitably omitted.
• Atransformer4 is a magnetic device in which a primary winding42 and secondary windings43 (a first secondary winding) and44 (a second secondary winding) mutually connected in series are magnetically coupled each other by winding around amagnetic core41 in such a way that all the windings have a polarity of the same direction each other.
• The secondary winding43 is formed by winding around themagnetic core41 by one turn. One end of the secondary winding43 is connected to a cathode of a below-mentioneddiode52 at a center tap C (a junction), and the center tap C is connected to an output terminal T3 (a first output end) via an output line LO. An end portion B of the secondary winding43 (a second end portion) is connected to the cathode of a below-mentioneddiode51. The secondary winding44 is formed by winding around themagnetic core41 by one turn. One end portion of the secondary winding44 is connected to the anode of thediode52, and the end portion A of the secondary winding44 (the first end portion) is connected to the anode of thediode51 and further connected to an output terminal T4 (a second output end) via a ground line LG. That is, the secondary side of thetransformer4 is of a center tap connection type.
• Therectifier circuit5 is a single-phase full-wave rectifier composed of a pair of diodes51 (a second rectifier device) and52 (a first rectifier device). Therectifier circuit5 is equivalent to therectifier circuit105 of a cathode common connection type which is configured by inserting thediode51 between the secondary winding43 and the center tap C, as shown inFIG. 3. Therefore, similarly to therectifier circuit105 shown inFIG. 3, the circuit configuration of therectifier circuit5 rectifies the separate half wave periods of the AC output voltages VO1 and VO2 of thetransformer4 by thediodes51 and52 respectively to output the rectified voltages from the center tap C and the junction point D.
• Next, effects of the switching power supply unit of the second embodiment will be explained as compared with a comparative example.
• In the comparative example, as shown inFIG. 4, the secondary windings (thesecondary windings43 and44) of thetransformer4 and wiring of the smoothingcircuit106 are divided by thediodes51 and52 of therectifier circuit105. That is, the secondary winding of thetransformer4 and the wiring of the smoothingcircuit106 are formed of a separate wiring, respectively, thereby large number of parts is needed for wiring and the structure is intricate. In addition, in order to electrically connect the wiring divided in this way, electrical connection by means of screw fastening, solder or welding, etc. is necessary between the wirings which are respectively extended from thediodes51 and52, thesecondary windings43 and44, thechoke coil62 and the output terminals T3 and T4, and the smoothingcapacitor63 each other.
• On the other hand, according to the second embodiment, as shown inFIG. 14, a path from the end portion B of the secondary winding43 to the output terminal T3 via the center tap C is formed of a wiring member17 (a first wiring member) made of a single sheet metal. A path from one of the ends of the secondary winding44 connected to thediode52 to the output terminal T4 via the end portion A is formed of a wiring member18 (a second wiring member) made of a single sheet metal. That is, the secondary windings (thesecondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of two sheet metals (wiring members17 and18). At this time, thediodes51 and52 of therectifier circuit5 are disposed in the vicinity of the end portions of thewiring members17 and18.
• According to the second embodiment, as described above, since the secondary winding (secondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of two sheet metals (thewiring members17 and18), the number of parts for wiring can be reduced from four parts to two parts. As a result, the structure can be simplified compared with configurations in the past.
• In this manner, according to the second embodiment, what is necessary is just to electrically connect thediodes51 and52, thewiring members17 and18 and the smoothingcapacitor63 each other by means of screw fastening, solder or welding, etc. Thereby man-hour requirement for the connecting operation can be reduced. In addition, since the number of junction points of wiring is decreased, generation of heat and power loss caused by the contact resistance in the junction point of wiring can be reduced. Moreover, since occurrence possibility of loosened screw or solder crack is reduced, reliability can be raised.
Modification of Second Embodiment
• In thechoke coil62 of the smoothingcircuit6, according to the second embodiment, the wiring on output terminal T3 (the wiring member17) side is wound around themagnetic core61 by half a turn and the wiring on the output terminal T4 (the wiring member18) side is wound around themagnetic core61 by half a turn so that both may be cooperatively wound around themagnetic core61 by just one turn as a whole. However, as shown inFIGS. 15 and 16, thechoke coil62 may be formed in such a way that the wiring only on the output terminal T3 (the wiring member17) side is wound around themagnetic core61 by one turn as a whole.
• In a case where a sufficient magnitude of inductor of thechoke coil62 is hardly obtainable just by one turn winding, as shown inFIGS. 17 and 18, there may be provided a two-turnedchoke coil162 instead of thechoke coil62. Thechoke coil162 includes afirst choke coil162A formed by winding around themagnetic core61 with the wiring on the output terminal T3 (wiring member17) side by one turn, and asecond choke coil162B formed by winding around themagnetic core61 with the wiring on the output terminal T4 (wiring member18) side by one turn. As described above, even in the case where the winding number of thechoke coil62 is two turns, it is possible to form each of thewiring members17 and18 by a single sheet metal, respectively. In this manner, as compared with configurations in the past, the number of parts for wiring can be reduced from four parts to two parts similarly to the above-mentioned second embodiment so that the structure can be simplified.
• According to the above-mentioned second embodiment, an equivalent circuit on the secondary side of thetransformer4 is configured of an anode common connection type, but as shown inFIGS. 19 and 20, orFIGS. 21 and 22, equivalent circuit on the secondary side of thetransformer4 may be configured of a cathode common connection type.
Third Embodiment
• FIG. 23 is a circuit diagram of a switching power supply unit according to a third embodiment of the present invention, andFIG. 24 shows a configuration of the switching power supply unit ofFIG. 23. The switching power supply unit is different in the configuration of the secondary winding of thetransformer4 and in the configuration of therectifier circuit5 as compared with the above-mentioned first embodiment. Then, hereinafter, points different from the above-mentioned first embodiment will be mainly explained, and description of the configuration, operation, and effect that are common to the above-mentioned first embodiment will be suitably omitted. It is to be noted, as a premise, that a substrate S is electrically connected to the ground.
• Atransformer4 is a magnetic device in which a primary winding42 and secondary windings43 (a first secondary winding) and44 (a second secondary winding) mutually connected in series are magnetically coupled each other by winding around amagnetic core41 in such a way that all the windings have a polarity of the same direction each other.
• The secondary winding43 is formed by winding around themagnetic core41 by one turn. One end of the secondary winding43 is connected to one end of the secondary winding44 at a center tap C (a junction), and the center tap C is connected to an output terminal T3 (a first output end) via an output line LO. An end portion B of the secondary winding43 (a second end portion) is connected to the cathode of a below-mentioneddiode51. The secondary winding44 is formed by winding around themagnetic core41 by one turn. One end of the secondary winding44 is connected to one end of the secondary winding43 at the center tap C, and the end portion A (a first end portion) of the secondary winding44 is connected to the cathode of adiode52. That is, the secondary side of thetransformer4 is of a center tap connection type.
• Therectifier circuit5 is a single-phase full-wave rectifier composed of a pair of diodes51 (a second rectifier device) and52 (a first rectifier device). The anode of thediode51 is connected to the anode of thediode52 at a junction point D, and further connected to an output terminal T4 (a second output end) via a ground line LG. The ground line LG is electrically connected to a substrate S.
• Therectifier circuit5 is equivalent to arectifier circuit105 of anode common connection type which is configured by inserting adiode51 between a secondary winding43 and a center tap C, and inserting adiode52 between a secondary winding44 and the center tap C, as shown inFIG. 25. Therefore, similarly to therectifier circuit105 shown inFIG. 25, the circuit configured of therectifier circuit5 rectifies the separate half wave periods of the AC output voltages VO1 and VO2 of thetransformer4 by thediodes51 and52 respectively to output the rectified voltages from the center tap C and the junction point D.
• The smoothingcircuit6 includes amagnetic core61, achoke coil62 and a smoothingcapacitor63. With such a configuration, the smoothingcircuit6 smoothes the rectified voltage inputted into a first input end In1 and a second input end In2 so as to generate a DC output voltage Vout. The DC output voltage Vout is then supplied through the output terminals T3 and T4 to a load L. Thechoke coil62 is formed in such a way that the wiring provided between the first input end In1 and the output terminal T3 is wound around themagnetic core61 by one turn as a whole.
• Next, effects of the switching power supply unit of the third embodiment will be explained as compared with a comparative example.
• In the comparative example, as shown inFIG. 26, the secondary windings (thesecondary windings43 and44) of thetransformer4 and wiring of the smoothingcircuit106 are divided by thediodes51 and52 of therectifier circuit105. That is, the secondary winding of thetransformer4 and the wiring of the smoothingcircuit106 are formed of a separate wiring, respectively, thereby large number of parts is used for wiring and the structure is intricate. In addition, in order to electrically connect the wiring divided in this way, electrical connection by means of screw fastening, solder or welding, etc. is necessary between the wirings which are respectively extended from thediodes51 and52, thesecondary windings43 and44, thechoke coil62 and the output terminal T3, the smoothingcapacitor63, and the substrate each other.
• On the other hand, according to the third embodiment, as shown inFIG. 24, a path from the end portion B of the secondary winding43 to the output terminal T3 via the center tap C is formed of a wiring member27 (a first wiring member) made of a single sheet metal. On the other hand, the secondary winding44 is formed of a wiring member28 (a second wiring member) made of a single sheet metal. The substrate S which is electrically connected to the ground is used as wiring of the ground line LG, and no other wiring is provided therein. Thereby, the output terminal T4 is formed as a pillar-shaped terminal that is electrically connected to the substrate S. With such configuration, the secondary windings (secondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of two separate sheet metals (thewiring members27 and28), respectively. At this time, thediodes51 and52 of therectifier circuit5 are disposed in the vicinity of the end portions of thewiring members27 and28.
• According to the third embodiment, as described above, since the secondary windings (thesecondary windings43 and44) of thetransformer4 and the wiring of the smoothingcircuit6 are formed of two sheet metals (thewiring members27 and28), the number of parts for wiring can be reduced from four parts to two parts. As a result, the structure can be simplified compared with configurations in the past.
• Thereby, according to the third embodiment, since what is necessary is just to electrically connect thediode51 and52, thewiring members27 and28, the smoothingcapacitor63 and the substrate S by means of screw fastening, solder or welding, etc., the man-hour requirement for the foregoing operations can be reduced. In addition, since the number of junction points of wiring is decreased, generation of heat and power loss caused by the contact resistance in the junction point of wiring can be reduced. Moreover, since occurrence possibility of loosened screw thread or solder crack etc. is decreased, reliability can be raised.
Modification of Third Embodiment
• According to the third embodiment, the path from the end portion B of the secondary winding43 to the output terminal T3 via the center tap C is formed of the wiring member27 (the first wiring member) made of a single sheet metal while the secondary winding44 is formed of the wiring member28 (the second wiring member) made of a single sheet metal. However, as shown inFIG. 27, a path from the end portion A of the secondary winding44 to the output terminal T3 via the center tap C may be formed of a wiring member37 (a first wiring member) made of a single sheet metal while the secondary winding43 may be formed of a wiring member38 (a second wiring member) made of a single sheet metal.
• As mentioned above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above-mentioned embodiments and many other modifications are obtainable.
• For example, in the foregoing embodiments, only therectifier circuit5 provided on the secondary side of thetransformer4 is mounted on the surface of the substrate S with an intermediate base T in between in a manner of bare chip mounting. However, as shown inFIG. 28, aninverter circuit1 and arectifier circuit5 may be mounted on an intermediate base M to form an integral module, and then the integral module may be mounted on the substrate S by means of bare chip mounting. In this manner, a switching power supply unit can be manufactured simply.
• It is to be noted that the intermediate base M is made of an insulating material, such as a ceramic, a plastic, or a film. Or, an insulating layer may be provided on the surface of the substrate S instead of the intermediate base M so that bare chip mounting can be carried out via the insulating layer. In this manner of mounting therectifier circuit5 on the substrate S with an intermediate base M in between in a manner of bare chip mounting, heat generated in therectifier circuit5 can be efficiently transmitted to the substrate S so that heat dissipation characteristics can be improved more. In particular, in a case where the intermediate base M is made of an insulating film or when an insulating layer is provided on the surface of the substrate S instead of the intermediate base M, higher thermal conductivity to the substrate S is obtainable, and heat dissipation can be more improved.
• In addition, in the switching power supply unit of the above-mentioned embodiments, although theinverter circuit1 is of a full-bridge type, it may be of a push pull type1-1, of a half-bridge type1-2 and the like as illustrated inFIGS. 29A and 29B.
• It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

Claims (4)

1. A switching power supply unit comprising, on a substrate:

a transformer transforming and outputting an AC voltage;

a rectifier circuit rectifying the AC voltage supplied from the transformer; and

a smoothing circuit smoothing and outputting the voltage rectified by the rectifier circuit,

wherein the transformer is disposed adjacent to both of the rectifier circuit and the smoothing circuit, and

the rectifier circuit is mounted on the substrate with an intermediate base in between.

2. A switching power supply unit according toclaim 1 comprising a switching circuit converting a DC input voltage into an AC voltage and outputting the converted AC voltage to the transformer,

wherein the switching circuit is mounted on the substrate with the intermediate base in between.

3. A switching power supply unit according toclaim 2,

wherein the switching circuit and the rectifier circuit are integrally mounted on the substrate with the intermediate base in between.

4. A switching power supply unit comprising, on a substrate:

a transformer transforming and outputting an AC voltage;

a rectifier circuit rectifying the AC voltage supplied from the transformer; and

a smoothing circuit smoothing and outputting the voltage rectified by the rectifier circuit,

wherein the rectifier circuit, the transformer, and the smoothing circuit are arranged in a line in this order.

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