Background technique
Switching Power Supply has many advantages, such as that size is small, high conversion efficiency, and application field constantly expands, including charger, suitableOrchestration etc..In recent years, major country proposes increasingly higher demands for the transfer efficiency of Switching Power Supply in the world, to meetThe VI grades of efficiencies requirement of the newest class requirement of European Union's efficiency (second stage) and U.S. Department of Energy, Switching Power Supply generally use synchronize it is wholeFlow Technique raising efficiency.It is higher and higher for the required precision of charger output voltage for the requirement for meeting mobile phone quick charge,Require charger output voltage that can need to be adjusted according to load simultaneously.Meet the charger of the specification of USB PD 3.0,Output voltage variation range is 3V~21V, and voltage minimum interval is 20mV.
It is traditional primary side (or primary side) regulating switch mains charger system 100A schematic diagram shown in Figure 1A.This is openedClosing mains charger includes that (AC voltage range is generally 85V to ac input end mouthACTo 265VAC), rectifier bridge 101 (will exchangeVoltage VACBe converted to DC voltage VIN), input capacitance 102, transformer 120, the first controller 104, the first power switch 105,Primary side (or secondary side) synchronous rectifying power switch 122, output capacitance 121, synchronous rectifying controller 124, output capacitance121, output port (V0) etc..The output voltage of Switching Power Supply shown in Figure 1A is controlled by the controller 104 for being located at primary side, secondarySide controller 124 is only used for synchronous rectification control, is not necessarily to optocoupler, cost is relatively low.But output voltage precision is sampled defeated by primary sideThe error limitation of voltage out, is generally only able to satisfy +/- 5% volume production precision.
Switching Power Supply shown in Figure 1B is a kind of charger without optocoupler.The primary side controller of Switching Power Supply 100B andSecondary side synchronous rectifier controller is placed among the same encapsulation, secondary side controller by the parasitic inductance of packaging frame toThe working condition of primary side controller transmitting control signal control primary side power switch.The output voltage of Switching Power Supply 100B passes throughIt is secondary side controller reception by divider resistance 125 and 126, output voltage is adjusted by secondary side controller, therefore can be guaranteedHigher voltage accuracy reaches +/- 2.5% volume production level.It is needed although not needing optocoupler in Switching Power Supply 100B, 104Special encapsulation, thus system cost is higher.
In conclusion compeling to be essential to meet the requirement of Switching Power Supply higher output voltage precision, lower system costDevelop a kind of Switching Power Supply control method and circuit that output voltage and electric current are controlled without optocoupler, by primary side.This is exactlyTarget of the invention.
The purpose of the present invention is to overcome the shortcomings of the existing technology, proposes a kind of new primary side regulating switch power supply electricityPressure/current control method and circuit reduce the loss of prior art primary side power switch, adapt to the demand of quick charge.
According to an embodiment of the invention, proposing a kind of Switching Power Supply, comprising: input port, be coupled to alternating voltage orDC voltage；Input capacitor, being coupled to input port, (when input voltage is alternating current, input capacitance is coupled by rectifier bridgeTo alternating voltage)；Transformer, has primary (first) winding and secondary (second) winding, and armature winding is coupled to input capacitance；Primary (first) power switch, is coupled to primary winding, has two kinds of working conditions of on and off；First is (primarySide) controller, it is coupled to prime power switch and transformer, the working condition of control prime power switch；Output port, couplingIt is loaded to Switching Power Supply, provides voltage and current to load；Output capacitor, be coupled to output port and transformer secondary output aroundGroup；Second (primary side) power switch, is coupled to transformer secondary output winding, has two kinds of working conditions of on and off；Second(primary side) controller is coupled to the second power switch, output port and transformer secondary output winding.Second controller energy fromInput capacitance controls the second power switch when transmitting to output capacitance and synchronizes rectification；Second controller also detects load voltageAnd electric current, first control signal is generated according to the error of load voltage or current signal；Second controller will be by that will export electricityHold the mode that energy is transmitted to input capacitance and first control signal is transmitted to the first controller；First controller is according to obtainingFirst control signal changes the working condition of the first power switch, and load voltage or electric current is made to meet preset value；
Specific embodiment
Specific implementation of the invention described in detail below.The example of embodiment provides in the accompanying drawings.It should be noted that retouching hereThe example stated is used only to for example, being not intended to restrict the invention.For the ease of understanding thoroughly the present invention, elaborate to implementDetails.However, for persons skilled in the art it is readily apparent that this hair need not also can be implemented using these detailsIt is bright.In describing the embodiments of the present, in order to avoid obscuring the present invention, circuit well-known in the art, such as primary side are controlledTypical synchronous rectification module, constant pressure, constant flow module and drive module are not described specifically in device.
Throughout the specification, to " one embodiment ", " embodiment " refer to it is meant that in conjunction with the embodiment describeSpecial characteristic, structure or characteristic are comprised at least one embodiment of the invention.Therefore, the whole instruction eachlyThe phrase " in one embodiment " that just occurs is not necessarily all referring to the same embodiment " in embodiment ".Furthermore, it is possible to appointingWhat it is appropriate combination and (or) sub-portfolio by specific feature, structure or property combination in one or more embodiment.Therefore, it will be appreciated by one with ordinary skill in the art that attached drawing is provided to illustration purpose provided herein, and attached drawing is differentSurely it is drawn to scale.It should be pointed out that it may be coupled directly to another member when claiming element " to be coupled to " another elementPart, there may also be intermediary elements.On the contrary, intermediary element is not present when claiming element " to be directly coupled to " another element.It is identicalOr similar appended drawing reference indicates same or similar element or the element with same or like operation.
Fig. 2 is based on 200 schematic diagram of primary side regulating switch power supply of the invention.It is opened with existing shown in Figure 1A, Figure 1BPowered-down source 100A, 100B the difference is that, the output voltage/electric current of Switching Power Supply 200 and synchronous rectification are by primary sideController 224 is realized, optocoupler is not necessarily to, without special package form.
In primary side regulating switch power supply 200 of the present invention shown in Fig. 2, input voltage vin is DC voltage, Switching Power Supply200 be DC-to-dc converter；Input voltage vin can also be obtained by AC rectification, as shown in figure 3, Switching Power Supply 300For AC-DC converter.
The embodiment of the present invention and advantage are described in detail below in conjunction with Fig. 2, Fig. 3.
Present invention could apply to need to carry out in the DC-to-dc converter power supply of input and output electrical isolation.Such as Fig. 2Shown, Switching Power Supply 200 includes transformer 220, is made of armature winding, secondary windings and auxiliary (third) winding.Auxiliary aroundGroup can be normal shock relationship (phase is identical) with armature winding, and auxiliary winding is also possible to flyback relationship (phase with primary side windingPosition is opposite).It converts and applies in DC-DC, such as Power over Ethernet POE scheme 48V turns in 12V application, it is convenient to omit auxiliaryWinding couples armature winding by divider resistance for the control signal receiving end VS of controller 204.
Switching Power Supply 200 shown in Fig. 2 further includes input port (VIN), input (first) capacitor 202, primary side (first)Controller 204, the first power switch 205, the second power switch 222, primary side (second) controller 224, output (second) electricityHold 221, output port (V0), output voltage divider resistance 225 and 226, secondary windings waveforms detection resistance 223, primary side controlDevice storage capacitor 207 processed, primary side current detection resistance 208, auxiliary winding divider resistance 209 and 210, auxiliary winding rectification twoPole pipe 206, start-up resistor 203.For the charging current for limiting storage capacitor 207, the anode in rectifier diode 206 can chooseOne current-limiting resistance of (or cathode) series connection (Fig. 2 is not drawn).
It is different from existing switch power technology shown in Figure 1A and Figure 1B, the secondary based on Switching Power Supply 200 (Fig. 2) of the inventionPower switch 222 is not only used as secondary synchronization rectified power device, and it is primary to be used as the control for generating secondary controller 224The control signal of 205 working condition of power switch is transferred to Docket No 204.Second controller 224 detects load voltage, rootThe first control signal PD_SW for changing 205 working condition of the first power switch is generated according to the error of load voltage, and first is controlledSignal PD_SW processed is transferred to the first controller 204；Second controller 224 will by the conducting and shutdown of the second power switch 222The energy of second capacitor 221 is transmitted to first capacitor device 202, and first control signal PD_SW is transmitted to first by this methodController 204；After first controller 204 detects that first capacitor device 202 obtains the energy of the second capacitor 221 transmitting, controlFirst power switch 205 changes working condition, meets preset value to control load voltage；
Secondary controller 224 includes synchronous commutating control circuit, and output voltage regulation circuit also may include output electric currentAdjust circuit.Docket No 204 includes primary current detection circuit, controls signal receiving circuit and prime power switch 205Driving circuit.A kind of specific embodiment of 200 control loop of Switching Power Supply is as follows: when secondary windings is output capacitanceAfter 221 charging process, secondary power switch 222 is in off state, and prime power switch 205 is also at cut-off shapeState.When the work of Switching Power Supply 200 is in constant voltage mode, secondary controller 224 is generated according to the error of the output voltage detectedPrime power switch 205 opens control signal PD_SW constantly next time.For the control signal is transmitted by secondary controller 224To Docket No 204, secondary controller 224 makes the second power switch 222 open an of short duration period output capacitance221 portion of energy is transferred to input capacitance 202.The control signal receiving circuit of Docket No 204 detected energy fromWhen output capacitance 221 is transferred to input capacitance 202, that is, identify this be second controller 224 send need prime powerThe first control signal PD_SW that switch 205 is opened.Docket No 204 is with by prime power switch 205 being switched to conducting shapeState, when primary side current reaches the first peak point current IPPWhen, the current detection circuit in 204 switches the first power switch 205For off state, the constant pressure closed-loop control of a cycle is realized.
Current constant control can also be realized by secondary controller 224 based on Switching Power Supply of the invention.Specific implementation is shown inFig. 3.
Fig. 3 is based on AC-DC converter power source design of the invention.Input port VINIt is coupled by rectifier bridge 201To alternating voltage VAC, Switching Power Supply 300 works in discontinuous conduction mode (DCM), and primary side controller 204 connects including open signalCircuit 302 is received, auxiliary winding (tertiary winding) is coupled to by divider resistance 209 and 210, is responsible for receiving from secondary controllerThe 224 first control signal PD_SW that power switch 205 is switched to on state from off state.Controller 204 further includesPrimary side peak point current comparator 303, first, which compares end, is coupled to primary side current detection resistance 208, and second compares end couplingIt is bonded to reference voltage VREF1.When the primary side open signal receiving module 302 in the first controller 204 detects secondary side controllerAfter the 224 first control signal PD_SW for needing primary side power switch 205 to open generated, module 302 exports a positive pulse letterThe output OUT of rest-set flip-flop 301 is set 1 by number POW_ON, and power switch 205 enters on state, primary side winding electric current IPIt is opened from 0Begin linearly increasing, works as IPElectric current increases to IPP=VREF1/R208When, comparator 303 exports a positive pulse signal POW_OFF willThe output OUT clear 0 of rest-set flip-flop 301, power switch 205 enter off state.
Second controller 224 shown in Fig. 3 includes synchronous rectification control module 404, constant-current control module 401, constant pressure controlMolding block 402, with door 403 or door 405.Second controller 224 detects transformer secondary output winding by port DET and resistance 223To the charging time T of output capacitance 221ONS, controlled for synchronous rectification control and constant current/constant voltage.As mentioned in the previous paragraph, it flows through justThe electric current of grade power switch 205 reaches IPPWhen the first controller 204 prime power switch 205 is switched to cut-off by stateState.Export average current
I0=(1/2) * IPP*(NP/NS)*TONS/TSW
Wherein IPP=VREF1/R208For fixed value, TSWFor switch periods, TSW=TONS+TDIS+TONP, TDISBroken time, i.e.,From TONSTerminate to the period that the first power switch 205 is opened next time, TONPFor the first power switch turn-on time；NPTo becomeDepressor armature winding the number of turns, NSFor transformer secondary output umber of turn.Constant current function implementation is as follows: second controller 224 is controlledMake the broken time T of each switch periodsDIS, make TONS/TSWValue be no more than a fixed upper limit (such as 0.5).As the T of a cycleDISCurtailment is so that TONS/TSWWhen less than the fixed upper limit (such as 0.5), constant-current control module it is defeatedSignal (constant current is enabled) CC_EN=0 out, even if output signal (constant pressure is enabled) CV_EN=1 of Isobarically Control module, the first controlSignal PD_SW processed remains as 0.T at this timeDISIt can extend, until TONS/TSWLess than the upper limit (such as 0.5) CC_EN afterwards of set fixation=1, the output PD_SW=1 with door 403, first control signal PD_SW are transferred to the first controller from second controller, thusRealize the constant current operation of Switching Power Supply 300.
Further include third controller 227 in the embodiment of the present invention shown in Fig. 3, needs to change divider resistance according to load225 and 226 ratio realizes quick charge so that Switching Power Supply 300 be made to need to export different voltage according to load.
In Fig. 3 embodiment that output voltage is needed with load and is changed, the polarity and first of the tertiary winding can chooseThe same phase of winding (normal shock power supply), so that the supply voltage of the first controller and input voltage VINIt is directly proportional, it is unrelated with output voltage.This power supply mode can overcome the shortcomings that polarity and the first winding reverse phase (flyback power supply) connection of traditional tertiary winding: whenWhen output voltage is widely varied, the supply voltage of the first controller is also widely varied.
Fig. 4 is the key node waveform diagram of Fig. 2 and Fig. 3 of the embodiment of the present invention.ISPFor secondary winding current；DET is secondThe drain voltage waveform of power switch 222；TONSIt is secondary windings to the charging time of output capacitance 221；CV_EN (Gao Youxiao)It is to stabilize the output voltage the enable signal for needing prime power switch 205 to be connected for the output of Fig. 3 Isobarically Control module 402；CC_EN (Gao Youxiao) is the enable signal of the limitation output electric current of Fig. 3 constant-current control module 401；PD_SW is what second controller generatedThe control signal that the first power switch of primary side 205 is connected, by the of short duration conducting of the second power switch by output capacitance 221On the mode of energy transmission sub-fraction to input capacitance 202 first control signal PD_SW is transferred to primary side firstController 204；DRV is second controller 224 to the driving signal of the second power switch 222, including synchronous rectification driving (withTONSBe overlapped) and control prime power switch 205 first control signal PD_SW；IPPFor peak primary currents；VS is auxiliary (theThree) winding (polarity and armature winding reverse phase) waveform, is opened for receiving from the control prime power that second controller 224 is sentClose the first control signal PD_SW of 205 conductings；OUT is the signal that the first controller 204 drives the first power switch 205.WhenAfter the first control signal PD_SW that two controllers 224 generate is lower by height, the sub-fraction energy of output capacitance 221 is passedTo primary input capacitance 202, the parasitic body diode of the first power switch 205 is connected, the first controller 204 detect energy fromOutput capacitance 221 drives the first power switch 205 by the switching-on state of off state after transmitting to input capacitance 202；It adoptsWith method of the invention ----by the fraction energy of output capacitance 221 by the second power switch 222 and transformer to inputThe mode that capacitor 202 transmits realizes control of the second controller 224 to 205 working condition of the first power switch, may be implemented theOne power switch 205 enters on state when power port voltage is essentially 0V, i.e. 205 voltage zero-cross of the first power switch is openedIt is logical, switching loss is reduced, transfer efficiency is improved.
Although, exemplary embodiment describes the present invention according to above-mentioned, it should be appreciated that, term used is explanationWith illustrative, rather than restrictive term.Since the present invention can be embodied in a variety of forms without departing from the present inventionSpirit or essence, it should therefore be appreciated that above-described embodiment is not limited to any mentioned-above detail, and should weighWidely understand in spirit and scope defined by benefit requirement.Therefore, whole changes in claim or its equivalent scope are fallen intoChange and remodeling is all covered by claim.