APPARATUS FOR PHASE-CUTTING CONTROL
Backaround of the Invention This invention relates to an apparatus for phase-cutting voltage control comprising a rectifier connectable to an AC voltage and a circuit means for controlling maximum voltage.
Sanders, U.S. Patent No. 4,685,046 discloses an apparatus of this type for phase-cutting control, which is supplied by a line voltage of, for example, 115 volts AC at 60 Hz. A bridge rectifier is provided for conversion to direct current, whereby the unsmoothed AC voltage is fed to semiconductors in the form of transistors and diodes. A
switching transistor in series with a load is operated such that a current can flow through the load only when the rectified AC voltage does not exceed a given threshold. By smoothing with a condenser parallel to the load, a comparatively low voltage of, for example, 11.3 volts DC is realized at the load. All of the components must be designed for the comparatively high input voltage, and in general this circuit requires a relatively bulky construction.
Furthermore, Klug, Published German Patent Application No. DE 3,704,467 discloses a miniature incandescent bulb which is designed for operation on 220 volt alternating current. Incandescent bulbs are regularly referred to as miniature incandescent bulbs if their diameter is substantially in the range between 7 and 20 mm. Such miniature incandescent bulbs regularly comprise metal bases 20~0~7 in standardized configurations designated as BA7s, BA9s, B15d, E10, E14, or in comparable configurations. Miniature incandescent bulbs are designed for powers up to about 2.5 W, which at 220 volts corresponds to a maximum current of approximately 12 mA. Since a miniature incandescent bulb contains a very thin filament in the form of a coil, such miniature bulbs have a life of about 5000 hours, even when the requirements of extended-service design are followed.
Miniature bulbs with the aforementioned metal bases, for example of type E10 or BA9s, have maximum dimensions of 11 x 29 mm (diameter x length), have typical characteristics due to their manufacturing process, and must comply with the standards, especially VDE0710. Furthermore, attention must be paid to manufacturing problems, especially in regard to the comparatively short air gaps and leakage paths that arise in practice where a minimum distance of 3 mm between voltage-carrying parts of opposite polarity frequently is not maintained. As a result, leakage currents occur in the case of applied voltages of more than 42 volts AC or DC, and electrical discharges can occur. Lastly, it is to be noted that, in order to operate such miniature incandescent bulbs on 230 volts AC or DC, external components in series, such as a resistor, condenser or the like, can be provided in order to reduce the voltage applied to the miniature bulb to a magnitude of about 100 to 130 volts. Such external circuitry involves considerable expense, and due to their considerable bulk problems are often encountered in arranging them in meters, control units, and the like.
Multiple LEDs containing two or more light emitting diodes (LEDs) in series or parallel are widely used today as a substitute for miniature incandescent bulbs or panel lights. Such multiple LEDs are characterized primarily by a long service life on the order of 100,000 hours, while miniature incandescent lamps have a life of about 5,000 hours. Also the absolute mechanical shock resistance of such multiple LEDs or multiple liyht emitting diodes plus 2~9~587 their low power consumption and resultant eooler operation eontribute to their widespread use. Today only voltage ranges between 5 and 60 V DC/AC can be eovered with multiple LEDs eontaining integrated series resistors or Zener diodes.
Due to the higher power requirement, higher voltage ranges require larger components which in no way ean be housed together with a multiple LED. It is to be noted that what is involved is housing dimensions on the order of 10 mm and a length of about 15 mm to 30 mm. Therefore in the eonventional voltage ranges of 110 to 230 volts, it has only been possible to operate sueh multiple LEDs in eonjunetion with external eireuitry, such as resistors or condenser eireuits.
Summary of the Invention It is t~e objeet of the invention to provide a power supply apparatus which has a small size and requires few eomponents.
It is also an objeet of the invention to provide a power supply apparatus in whieh the eircuit ean be integrated into the housing or base of a light souree.
Another objeet of the invention is to provide an apparatus whieh can make use of an LED display.
A further object of the invention is to provide an apparatus which has a structure which delivers reliable operation over a long service life.
These and other objects of the invention are achieved by providing an apparatus for phase-cutting control comprising a rectifier with input terminals connectable to an AC voltage source for outputting a pulsating DC voltage, a light source operable at a voltage less than a predetermined limit value, circuit means connected between the rectifier and the light source for eondueting eleetrieity from the reetifier to the light souree, the eireuit means blockir.g current flow when the DC voltage outputted by said rectifier exeeeds the predetermined limit 20~05~7 value, and a housing having front and rear portions and enclosing the rectifier, the circuit means and the light source with the light source disposed in the front portion of the housing. The light source preferably may be an LED
or a multiple LED.
The apparatus according to the invention is characterized by a compact construction and, with a small number of components, assures the achievement of phase-cutting control. The electronic circuit of the phase-cutting power supply apparatus is disposed within a housingat whose front end the light source is disposed. The light source preferably takes the form of an LED or multiple LED.
The housing may be formed of plastic and may have a substantially cylindrical shape. The light source is fastened in the front part of the housing, while the phase-cutting power supply circuitry occupies a substantial portion of the interior of the housing. The housing forms a secure protection both for the light source and for the circuitry. A plastic housing also readily satisfies safety requirements. The light source and the electronics reliably mounted and secured in the housing and together constitute a preassembled component group which can be readily inserted into the required standard socket. The proposed apparatus includes the plastic housing, the base, the connected electronics integrated into the plastic housing, and the LED
or multiple LED, so that together with the integrated electronics, a substitute or replacement for conventional miniature incandescent bulbs is created for direct connection to conventional line voltages.
The circuit can be reliably manufactured by surface-mounted component techniques. Furthermore, the circuitry according to the invention can be constructed by means of conventional semiconductors, as ASICs, as ICs or as hybrid circuits by the thick film or thin film techniques. Direct connection to the power line is made possible without a transformer. Regardless of the particular concrete 209~87 configuration, the circuit is equally suitable as a part of a switching network and as a series device for light sources, especially light emitting diodes, LED indicator lights, multiple LEDs or incandescent b~lbs, and direct use in voltage ranges from 110 to 250 volts AC is made possible.
Multiple LEDs or LED indicator lights can be connected to 110 to 250 volt AC power lines without external circuitry, and can easily be used for the replacement of existing light sources such as incandescent bulbs or glow-discharge lamps.
Because of the considerably longer service life of multiple LED or LED panel lights compared to incandescent bulbs or glow-discharge lamps, appreciable cost savings with respect to replacement and maintenance are achieved.
Additional cost advantages accrue from the lower power consumption and lower heat generation compared to an incandescent. Finally, it is expressly emphasi~ed that the multiple LED or LED with integrated circuitry connected before it in accordance with the invention does not result in any loss of brightness, and thus assures the reliable illumination of pushbuttons, warning lights or other indicators, with a low manufacturing cost and with a high operating reliability over a long service life. The circuit can be constructed in accord with the invention on a board with dimensions on the order of 8.3 x 14 mm or less. It is desirable to mount the parts on the front and back of the board, thereby achieving optimum use of available space, especially when the board is disposed substantially in an axial plane of the cylindrical housing. The proposed LED or multiple LED apparatus with integrated electronics connected in accordance with the invention, is a substitute for miniature incandescent lights for direct connection to power lines. Further features and preferred embodiments are explained in the following detailed description.
2~905~7 Brief Description of the Drawinas The invention will be described in further detail with reference to the accompanying drawings in which:
Fig. 1 is a schematic circuit diayram of the apparatus according to the invention;
Figs. 2 and 3 are axial longitudinal sectional views taken in planes at 90 from one another through a multiple LED display; and Fig. 4 is a sectional view taken along line IV-IV in Fig. Z.
~etailed DescriPtion of Preferred Embodiments The circuit shown in Fig. 1 can be assembled on a circuit board 42 having very small dimensions on the order of especially 8.3 x 1~ mm. There are two inputs 1 and 2 for direct connection to 220 volts AC. A transformer is unnecessary, according to the invention. To protect against voltage surges a surge protector diode 6 is placed at the input. With respect to a neutral conductor 8, the bridge rectifier 3 delivers to its outputs 4 and 5 a pulsating voltage whose amplitude at point 10 rises to a peak of 320 volts at an input voltage of 220 volts. Two terminals 12 and 13 are provided, terminal 12 being connected to the aforementloned point 10. ~erminal 13, on the other hand, is connected through a transistor 14 and a resistor 15 to the neutral conductor 8. Transistor 14 is preferably a field effect transistor. A light source 16, which preferably is a multiple LED, is connected to the two terminals 12 and 13.
If a single LED has a conducting voltage of, for example, 16 volts DC, then for a multiple LED an increased voltage depending on the number of LEDs is provided at terminals 12 and 13. Within the scope of the invention, at least one LED
is present, and optionally several LEDs, particularly in the form of a multiple LED, can be connected in parallel or in series.
2~90~7 A second point 20 is connected to the first point 10 through a resistor 22. In the illustrated embodiment resistor has a value of 200K ohms. By means of this common resistor 22, the voltage applied to the circuit part described below is substantially reduced compared to the voltage at point 10, preferably to a voltage on the order of half of the voltage at polnt 10. If the pulsating, rectified voltage at point 10 reaches a peak level of 320 volts, for example, then as a result of the subsequently connected common resistor 22 the voltage at point 20 will be substantially halved to 160 volts. In this way the cost and above all the volume occupied by the circuit components provided for controlling the transistor 14, which advantageously takes the form of a field effect transistor, are reduced to a minimum. The subsequent electronic components do not have to be designed for the high maximum voltage, but only for a considerably reduced part of it. A
voltage divider with two resistors 24 and 25, having values of 300K ohms and 91K ohms, respectively, is connected to 20 point 20. A junction 26 between the two resistors 24 and 25 is connected by a Zener diode 28 to the base of a transistor 30. Furthermore, point 20 is connected by a 300K ohm resistor 30 and another Zener diode 34 to the neutral conductor 8. The common point 35 between the resistor 32 and the cathode of the zener diode 34 is connected on the one hand to the base of transistor 14 and on the other to the collector of transistor 30. As a result of the Zener diode 34 point 35 is at 10 volts when transistor 30 is blocked. Transistor 14 is constructed as a type 30 ZVNO545A/BS3934 field effect transistor, while transistor 30 is a type BC847C transistor. The invention makes it possible at minimum manufacturing cost to use components of small dimensions and ultimately to install them in the housing of a display.
The circuit is preferably constructed from components of the aforementioned type numbers or values, but a ~09~8~
corresponding circuit within the scope of the invention can also be designed using other comparable components, in particular for another input voltage such as 110 volts AC.
It results in a self-acting phase-cutting control and constitutes a circuit component which can be appropriately dimensioned and used both for the aforementioned LED and also for other purposPs.
The manner of operation will now be explained.
Starting from the null point of the pulsating DC vol-tage at point 10, then, as the voltage increases the field effect transistor 14 becomes conductive~ Voltage is thus present at the terminals 12 and 13 and thus a-t the multiple LED 16, and consequently a substantially constant current flows, amounting, for example, to 90 mA. Initially, the transistor is not yet conductive. If the voltage at point 10 continues to increase and reaches a predetermined value, then transistor 30 becomes conductive as a result of the voltage divider composed of resistors 22 and 32, and 24 and 25. In a preferred embodiment, the voltage divider and the transistor 30 are so dimensioned and matched to each other, that transistor 30 becomes conductive when the voltage at point 10 is 94 volts. Thus point 35, and consequently the base of transistor 14, drop to zero potential, with the result that transistor 14 is blocked and current can no longer flow through the LED 16. The voltage at point 10 continues to rise to its maximum of 320 V and again reaches the aforementioned switching threshold of 94 volts. The voltage drop at resistor 25 then becomes so small that it is no longer sufficient to keep transistor 30 open, and transistor 30 blocks again. Consequently the transistor 14 is again activated, and voltage is again present at terminals 12 and 13 and thus at the multiple LED 16, producing the constant current of approximately 90 mA. It is important that transistor 14 is conductive as long as the voltage present at the outputs 4 and 5 is below a predetermined limit, while in accordance with the invention 2~587 th~ transistor 14 is blocked after the predetermined limit is exceeded.
A voltage is periodically applied to the multiple LED
16, or in general a load and/or ~ight source connected to ; the terminals 12 and 13, and when a predetermined limit is exceeded, it is disconnected, and when the voltage falls below the limit, it is applied again. Thus, current pulses of a defined magnitude are fed to the light source 16, and its light output is increased without any danger of damage 0 due to the effects of heat or loss of output.
The decrease in output when the voltage applied to the inputs 1 and 2 increases is particularly significant. If, for example, as a result of disturbances of the electrical power distribution network substantially elevated voltage peaks or longer-lasting elevated voltages of, for example, 250 volts instead of 220 volts AC, reach the inputs 1 and 2, the predetermined limit will be reached at point 10 sooner in time, and the current flow will thus be briefer.
Correspondingly, after the predetermined limit has been o exceeded, the limit value will again be reached later in time, and a shorter period of time will be required until the voltage attains the 0 value, so that once again the duration of current flow will be shorter. The ratio of the length of the current pulses to the phase duration becomes smaller, and the power consumption decreases, and any damage or risk of damage due to excessive voltage is reliably prevented. These special advantages are likewise important in the case of other applications, especially in the case of use as a self-cycled component of a network.
;0 Fig. 2 shows, as an illustrative embodiment of the invention, an axial longitudinal section of an LED display with a multiple LED 16 which is installed in a plastic housing 36. The multiple LED lies with its rear surface 37, especially the outer margin thereof, abutting associated axial end faces which are provided inside housing 36 on ledges, radially inwardly extending projections, or the _ g 2~90~87 like. This assures a secure support and fastening of LED 16 in the front end of the housing 36. Housing 36 is injection molded from plastic and has in its front end 38 a substantially cylindrical inside surface 40. The multiple LED 16, the outer surface of which is also cylindrical, is inserted in this front end 38 and preferably tightly held therein. The front of LED lG preferably is substantially flush with the front edge 39 of housing 36, and the convex front surface of LED 16 protrudes only slightly outside the housing 38. The multiple LED 16 is thus reliably protected against external effects.
A circuit board 42 bearing the above-described circuit for phase-cutting control is integrated into the housing 36.
In the illustrated preferred embodiment this board 42 has a 1~ width 44 of 8.3 mm and a height 16 of 14 mm. The width 44 preferably corresponds substantially to the inside diameter of the housing 36. The height 46 is, in accordance with the invention, substantially greater than half the axial length 47 of housing 36 and amounts preferably to about 3/4 of the axial length. The miniaturized circuit described above is arranged on th:is board, with its input terminals 1 and 2 shown in the drawing in the form of connecting wires. The circuit components are arranged both on the front side of board 42 shown in this figure of the drawings as well as on the back side thereof. The board 42 is disposed substantially in an axial plane containing the longitudinal axis 45 of the housing 36. The individual components of the circuit, such as, for example the surge protector diode 6, are only shown schematically. Also shown is the lead 17 from the multiple LED 16 and the connection to the terminal 12, while the other lead 18 is attached to the opposite or back side of board 42.
The rear end 48 of housing 36 containing the integrated multiple LED 16 and similarly integrated circuitry can be inserted in a sleeve 49, shown here by broken lines. In a particularly preferred embodiment, the rear end 48 of the 2~9as87 housing 36 has ~ smaller wall thickness than the front part of housing 36, and the end face of the sleeve 49 abuts a shoulder 50 formed where the wall thickness of the housing 36 changes. The circuit and/or the board 42 extends nearly to the rear end of the end portion 48, and as can be seen in the drawing, a considerable portion of the board 42 is received in the interior of the sleeve or base 49. At the end portion 48, therefore, the base 49 surrounds both the end portion 48 and that part of the circuit or board 42 disposed within it. This sleeve 49 i5 advantageously configured as a base having the usual dimensions of miniature incandescent bulbs, so that a multiple LED display with base and integrated circuit constructed in this manner can be substitul_ed without any difficulty for a conventional incandescent bulb or miniature bulb. The terminal leads 1 and 2 or corresponding connecting wires provided as power connections are affixed, as in the case of incandescent bulbs, to the metal base and center contact at the end of the base, respectively.
Fig. 3 likewise is a longitudinal section of the LED
display, but in a position rotated 90 about its longitudinal axis. Among other things, this figure shows the connection of the lead 18 of the multiple LED 16 to the board 42. The housing 36 has a rear end portion 48 having a smaller wall thickness than the front part. The components of the electronic circuitry arranged on the back 51 of the board 42 can also easily be seen. Since the board 42 is disposed in the center of the housing in the plane of the axis and the components are disposed both on the back and on the front of the board 42, the integration of the circuit is facilitated with optimum utilization of the very small interior space of the housing 36.
Fig. 4 shows a transverse sectional view of the housing in which multiple LED is not illustrated. The circuit board 42 which is provided on both sides with the electronic components can here easily be seen. The board 42 is in the 2~9~87 center of the plastic housing 36, substantially in the plane of the axis. In the vicinity of the longitudinal edges 52, 53 of the circuit board 42, the housing 36 is provided with radial extensions 54 and 55. The width 44 of board 42 is substantially equal to the inside diameter 56 of housing 36, which on the one hand has sufficient stability, but on the other hand has sufficient space in its interior for the board with the phase-cutting control circuit. In the area of the section plane the housing 36 has radially inwardly positioned axial abutment surfaces 57 and 58. These abutment surfaces constitute parts of radially inwardly extending projections and form the support for the light source, which preferably is configured as a multiple LED.
A stable and functional support is thus created for the light source, and any possibility of damage to the circuit integrated into housing 36 is prevented.
The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations falling within the scope of the appended claims and equivalents thereof.