CN102594124B - Switching power circuit - Google Patents

Switching power circuit Download PDF

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Publication number
CN102594124B
CN102594124B CN201210047494.XA CN201210047494A CN102594124B CN 102594124 B CN102594124 B CN 102594124B CN 201210047494 A CN201210047494 A CN 201210047494A CN 102594124 B CN102594124 B CN 102594124B
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circuit
output
resistance
connects
voltage
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CN201210047494.XA
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CN102594124A (en
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吴清平
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深圳麦格米特电气股份有限公司
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a switching power circuit and a control method. A secondary circuit of the switching power circuit comprises a main output circuit and an auxiliary output circuit, and the control circuit comprises a microcontroller, a main output switching circuit, a standby voltage control circuit and a working state sampling circuit. Under a standby working state, the main output circuit is switched off by the microcontroller; and a PWM (pulse-width modulation) controller of the switching power supply works under an energy-saving mode with low frequency and/or low duty cycle, and a standby voltage output by the auxiliary output circuit is lower than an auxiliary power voltage under the normal working state, so that a converter can work in an energy-saving state, and low standby power consumption is realized. According to the invention, only one converter is needed, circuit structure is simple and the realizing cost is low.

Description

A kind of switching power circuit
[technical field]
The present invention relates to Switching Power Supply, relate in particular to a kind of switching power circuit and control method.
[background technology]
For energy savings, countries in the world are more and more stricter to the energy consumption standard of various electronic products, set up enforceable " green power supply " standard-required, famous in European Energy Star a lot of electronic products, are often in standby waiting state, and standby amount need continue to consume grid power, although absolute power when single power standby is little, because the quantity of product is very huge, it is also very huge causing total consumed power.For reducing these useless consumption, according to dissimilar product, power supply is proposed to strict stand-by power consumption requirement, typical requirement is less than 0.5W as stand-by power consumption, and the stand-by power consumption that even requires having is less than 0.3W.
For meeting low-power consumption requirement, at present a lot of power supply chip manufacturer Development and Production various types of green model PDM keyer (Green-Mode PWM Controller), as single-chip FAN6756, it is exactly the integrated green model PWM controller of a height.The common feature of these chips is in the time that circuit enters holding state, chip also enters energy-conservation mode of operation, such as adopting the method for frequency conversion, reduce operating frequency along with the minimizing of power output or adopt the methods such as mode of operation intermittently to reduce switching loss, reach energy-conservation object.
When electronic product stand-by operation, boost voltage is generally output 5V left and right, and main output may be exported on Shi Yi road, may be also multichannel output.Although PWM chip can be realized " green " mode of operation, but because various electronic products are had nothing in common with each other to operating voltage and power requirement, there is high voltage, have low-voltage, there is single channel, have multichannel, have high-power, also have power little, so require and want can meet standby low-power consumption requirement with the multiple output that a green model PWM chip is realized power supply, be difficult to make the best of both worlds simultaneously.
As shown in Figure 1, for meeting stand-by power consumption requirement, conventional power source design is the mode that adopts two converters at present: do standby and low tension loop output for one; Another power stage of deciding is used.When in holding state, only stand-by circuit work, main output translator is closed, and only, receiving after normal work order signal, just starts main converter.
Although adopt the mode of two converters easily to realize low standby power loss requirement, major defect is that cost is high, circuit complexity, if PCB layout processing obtains badly in addition, is easy to cause two converters to interfere with each other, and causes work undesired.
[summary of the invention]
The technical problem to be solved in the present invention is to provide that a kind of circuit structure is simple, to realize cost lower, the control method of the Switching Power Supply that stand-by power consumption is little.
Another technical problem that will solve of the present invention be to provide a kind of simple in structure, cost is lower, the switching power circuit that stand-by power consumption is little.
In order to solve the problems of the technologies described above, the technical solution used in the present invention is, a kind of control method of Switching Power Supply, under stand-by operation state, close main output circuit, the PWM controller of Switching Power Supply is worked under the energy saver mode of low frequency and/or low duty ratio, and the standby voltage of auxiliary output circuit output is lower than the accessory power supply voltage under normal operating conditions.
Realize a technical scheme for above-mentioned control method switching power circuit, comprise former limit circuit, secondary circuit, transformer and control circuit, former limit circuit and secondary circuit are by transformer coupled; Former limit circuit comprises the inverter circuit being driven by described PWM controller, described secondary circuit comprises main output circuit and auxiliary output circuit, and described control circuit comprises microcontroller, main output switch circuit, standby voltage control circuit and operating state sample circuit; The output termination microcontroller of operating state sample circuit, the signal input part of main output switch circuit connects the main output switch control signal output of microcontroller; The signal input part of standby voltage control circuit connects the standby voltage control signal output of microcontroller, the output termination PWM controller control signal input of standby voltage control circuit.
Above-described switching power circuit, described main output circuit comprises the first secondary winding, the first current rectifying and wave filtering circuit and the output port of transformer, the output of the first secondary winding connects output port through the first current rectifying and wave filtering circuit; Described main output switch circuit comprises switching tube, the first bleeder circuit, the second bleeder circuit and a NPN triode; The cathode output end of first termination the first current rectifying and wave filtering circuit of described switching tube, the second termination output port positive pole; The first bleeder circuit comprises the first resistance and second resistance of series connection, the first end of a termination switching tube of the first bleeder circuit, and the collector electrode of another termination the one NPN triode, the tie point between the first resistance and the second resistance connects the control utmost point of switching tube; The second bleeder circuit comprises the 3rd resistance and the 4th resistance of series connection, the main output switch control signal output of a termination microcontroller of the second bleeder circuit, other end ground connection; Tie point between the 3rd resistance and the 4th resistance connects the base stage of a NPN triode, the grounded emitter of a NPN triode; The cathode output end ground connection of the first current rectifying and wave filtering circuit.
Above-described switching power circuit, comprises constant-voltage control circuit and optocoupler, and described auxiliary output circuit comprises the second secondary winding and second current rectifying and wave filtering circuit of transformer, output termination second current rectifying and wave filtering circuit of the second secondary winding; The cathode output end of the second current rectifying and wave filtering circuit is as the cathode output end of auxiliary output circuit, the cathode output end ground connection of the second current rectifying and wave filtering circuit; Constant-voltage control circuit comprises the 3rd bleeder circuit, offset resistance and the first parallel regulator, and the 3rd bleeder circuit comprises the 5th resistance and the 6th resistance of series connection, the cathode output end of termination first current rectifying and wave filtering circuit of the 3rd bleeder circuit, other end ground connection; Tie point between the 5th resistance and the 6th resistance connects the reference voltage end of the first parallel regulator, the plus earth of the first parallel regulator, and negative electrode connects the cathode output end of the second current rectifying and wave filtering circuit by offset resistance; The anode of optocoupler light-emitting diode connects the cathode output end of the second current rectifying and wave filtering circuit, and negative electrode connects the negative electrode of the first parallel regulator; The collector electrode of optocoupler phototriode connects PWM controller control signal input, grounded emitter.
Above-described switching power circuit, described standby voltage control circuit comprises voltage-stabiliser tube and the 2nd NPN triode, the negative electrode of voltage-stabiliser tube connects the negative electrode of optocoupler light-emitting diode; The base stage of the 2nd NPN triode connects the standby voltage control signal output of microcontroller, grounded emitter, and collector electrode connects the anode of voltage-stabiliser tube.
Above-described switching power circuit, described operating state sample circuit comprises current sampling circuit, described current sampling circuit comprises sampling resistor and amplifying circuit, the negative pole of the input termination output port of amplifying circuit, the negative pole of output port is by sampling resistor ground connection, the output termination microcontroller current sampling circuit input of amplifying circuit.
Above-described switching power circuit, comprise linear voltage-stabilizing circuit, described linear voltage-stabilizing circuit comprises the 3rd NPN triode, the 4th bleeder circuit, base resistance and the second parallel regulator, the emitter of a termination the 3rd NPN triode of the 4th bleeder circuit, other end ground connection; The 4th bleeder circuit comprises the 7th resistance and the 8th resistance of series connection, and the tie point between the 7th resistance and the 8th resistance connects the reference voltage end of the second parallel regulator; The negative electrode of the second parallel regulator connects the base stage of the 3rd NPN triode, plus earth; The collector electrode of the 3rd NPN triode connects the cathode output end of the second current rectifying and wave filtering circuit, and emitter connects the power input of microcontroller; The base stage of the 3rd NPN triode connects the collector electrode of the 3rd NPN triode by base resistance.
Above-described switching power circuit, described operating state sample circuit comprises load access test circuit, and described load access test circuit comprises the 4th bleeder circuit, and the 4th bleeder circuit comprises the 7th resistance and the 8th resistance of series connection; The power input of one termination microcontroller of the 4th bleeder circuit, the load access signal testing end of another termination microcontroller, the tie point between the 7th resistance and the 8th resistance is as the sampled point of load access.
Above-described switching power circuit, is characterized in that, described transformer T1 is flyback transformer.Described switching power circuit is battery charger.
The all Voltage-output of switching power circuit of the present invention is all from same converter, and circuit structure is simple, it is lower to realize cost.When in stand-by operation state, main output circuit cuts out; When in holding state, it is lower that the output voltage PWM chip that only needs to ensure stable stand-by circuit can be operated in frequency, or under longer energy saver mode of intermittent time, make converter can work in the state of more power saving, realizes lower stand-by power consumption.
[brief description of the drawings]
Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.
Fig. 1 is the theory diagram of prior art switching power circuit.
Fig. 2 is the theory diagram of embodiment of the present invention switching power circuit.
Fig. 3 is the schematic diagram of embodiment of the present invention switching power circuit main circuit part.
Fig. 4 is the schematic diagram of embodiment of the present invention switching power circuit control circuit part.
[embodiment]
In the embodiment of the switching power circuit of the present invention shown in Fig. 2 to Fig. 4, switching power circuit is battery charger, and battery charger comprises former limit circuit, secondary circuit, transformer T1 and control circuit; Former limit circuit and secondary circuit are coupled by transformer T1, and transformer T1 is flyback transformer; Control circuit comprises microcontroller U2 (Samsung single-chip microcomputer S3F9454).
Flyback transformer English is called " FLY-BACK Transformer ".In the course of the work, in the time of the input main switch conducting of control transformer, the namely primary inductance conducting of primary winding, transformer energy storage, secondary winding does not have energy output, and output energy is provided by the energy being stored in secondary capacitance; In the time of the cut-off of input main switch, transformer input winding stops energy storage, between the off period, the energy that is stored in transformer discharges by secondary winding, energy is transferred in secondary storage capacitor and load, the feature of flyback transformer is: energy storage when armature winding conducting, exoergic when cut-off, just as an energy storage inductor.
Relative with anti exciting converter is forward converter, and normal shock transformer output will connect energy storage inductor and fly-wheel diode, but flyback transformer does not need energy storage inductor and fly-wheel diode, and circuit is simple, easily realizes multichannel output.
Former limit circuit comprises switching tube Q5, the primary coil T1H of transformer T1 and PWM controller IC 1.Rectifier bridge BG1 and electric capacity EC1 form input rectifying filter circuit, and the series circuit of the primary coil T1H of switching tube Q5 and transformer T1 connects the output of input rectifying filter circuit; PWM controller IC 1 (green model PWM chip LD7576), pwm signal output (5 pin of IC1) connect the control utmost point of switching tube Q5, form the inverter circuit being driven by PWM controller.
Secondary circuit comprises main output circuit and auxiliary output circuit; Control circuit comprises microcontroller, main output switch circuit, standby voltage control circuit, constant-voltage control circuit and operating state sample circuit.
Main output circuit comprises output port VB+, the VB-of the first secondary winding T1Y, the first current rectifying and wave filtering circuit and the battery charger of transformer T1.The first current rectifying and wave filtering circuit comprises rectifier diode D1, electric capacity EC4, C24, the cathode output end ground connection of the first current rectifying and wave filtering circuit.
Main output switch circuit comprises main switch Q1, NPN triode Q3, voltage-stabiliser tube Z1, diode D7, D8, isolating diode D2, capacitor C 5, resistance R 10, R11, R18, R20.
The first end (number of pins 3) of main switch Q1 meets the cathode output end Vout-1 of the first current rectifying and wave filtering circuit through isolating diode D2, the second end (number of pins 2) meets the anodal VB+ of output port; Resistance R 10, R11 are composed in series the first bleeder circuit, the first end of one termination main switch Q1 of resistance R 10, one end of resistance R 11 connects the collector electrode of NPN triode Q3 by diode D8, the tie point between resistance R 10, R11 connects the control utmost point of main switch Q1.The negative electrode of voltage-stabiliser tube Z1 connects the first end of main switch Q1, and anode connects the control utmost point of main switch Q1; Capacitor C 5 and voltage-stabiliser tube Z1 also connect.
Resistance R 18, R20 the second bleeder circuit in series, one end ON/OFF-2 of resistance R 20 is as the main output switch control signal output ON/OFF-2 of the control signal input termination microcontroller U2 of main output switch circuit, one end ground connection of resistance R 18; Tie point between resistance R 18, R20 connects the base stage of NPN triode Q3, the grounded emitter of NPN triode Q3.The negative electrode of diode D7 connects the base stage of NPN triode Q3, and anode connects the emitter of NPN triode Q3.
In the time that the signal of ON/OFF-2 is high level, main switch Q1 conducting, main output circuit can be exported; In the time that the signal of ON/OFF-2 is low level, main switch Q1 cut-offs, and main output circuit cuts out.
Auxiliary output circuit comprises the second secondary winding T1X, resistance R 16, rectifier diode D5, capacitor C 4, the EC6 of transformer T1.The output of the second secondary winding T1X connects the second current rectifying and wave filtering circuit of rectifier diode D5, capacitor C 4, EC6 composition by resistance R 16; The cathode output end VAUX of the second current rectifying and wave filtering circuit is as the cathode output end of auxiliary output circuit, the cathode output end ground connection of the second current rectifying and wave filtering circuit.
The constant-voltage control circuit of main output (Vout-1) comprises resistance R 28, R29, R30, R31, R32, R82, RW1, capacitor C 10, offset resistance R 27 and parallel regulator U1 (TL431).
Resistance R 28, R29, R30, R31, R32, R82, RW1 form the 3rd bleeder circuit, obtain the voltage sampling signal of main output Vout-1 end.One end of the 3rd bleeder circuit R30, R32 connects the cathode output end Vout-1 (42V/2A) of the first current rectifying and wave filtering circuit, one end ground connection of the 3rd bleeder circuit R28, R31 as the signal input part Vout-1 of constant-voltage control circuit; Tie point between the 3rd bleeder circuit R30, R32 and R28, R31 meets the Voltage Reference end R (shunting adjuster signal input R) of parallel regulator U1, the plus earth of parallel regulator U1, negative electrode meets the cathode output end VAUX of the second current rectifying and wave filtering circuit by offset resistance offset resistance R 27; After resistance R 29 and capacitor C 10 series connection, the reference voltage end of a termination parallel regulator U1, the negative electrode of another termination parallel regulator U1; The anode of optocoupler P1 light-emitting diode meets the cathode output end VAUX of the second current rectifying and wave filtering circuit by resistance R 26, negative electrode connects the negative electrode of parallel regulator U1; The collector electrode of optocoupler P1 phototriode connects the control signal input (the 2nd pin of IC1) of PWM controller IC 1, grounded emitter.
In the time that the voltage of the cathode output end Vout-1 of the first current rectifying and wave filtering circuit changes, through the 3rd bleeder circuit voltage sampling, reference edge (R) magnitude of voltage of constant-voltage control circuit parallel regulator U1 (TL431) changes, carry out after signal relatively amplifies through parallel regulator inside, feed back to the control signal input of PWM controller IC 1 by optocoupler, make the voltage of the cathode output end Vout-1 of the first current rectifying and wave filtering circuit remain constant.
Standby voltage control circuit comprises voltage-stabiliser tube Z4, resistance R 62, R63 and NPN triode Q9, and the negative electrode of voltage-stabiliser tube Z4 connects the negative electrode of optocoupler P1 light-emitting diode through common electrical node VP; The base stage of NPN triode Q9 meets the standby voltage control signal output STB of microcontroller U2 by resistance R 63, grounded emitter, and collector electrode connects the anode of voltage-stabiliser tube Z4; Resistance R 62 is connected between the base stage and emitter of NPN triode Q9.
In the time of battery charger standby, the standby voltage control signal output STB of microcontroller U2 sends high level, Q9 is open-minded for NPN triode, by the plus earth of voltage-stabiliser tube Z4, the voltage-stabiliser tube Z4 of 5.1V is linked in constant-voltage control circuit, make the constant-voltage control circuit of principal voltage output (Vout-1 end) ineffective, and feed back to the control signal input of PWM controller IC 1 by optocoupler, make the output voltage V AUX of auxiliary output circuit drop to 7.5V by 25V simultaneously.
The output voltage V AUX of auxiliary output circuit supplies with by linear voltage-stabilizing circuit the standby voltage (VR=5V) that the microcontroller U2 precision of voltage regulation is high, voltage is 5V.Linear voltage-stabilizing circuit comprises NPN triode Q6, parallel regulator IC2, capacitor C 11, resistance R 38, R39, R40 and R48.
Resistance R 39, R40 the 4th bleeder circuit in series, the emitter of a termination NPN triode Q6 of the 4th bleeder circuit R39, one end ground connection of the 4th bleeder circuit R40; Tie point between resistance R 39, R40 connects the reference voltage end of parallel regulator IC2; The negative electrode of parallel regulator IC2 connects the base stage of NPN triode Q6, plus earth; The collector electrode of NPN triode Q6 meets the cathode output end VAUX of the second current rectifying and wave filtering circuit, and emitter meets the power input Vdd of microcontroller U2; The base resistance that the base stage of NPN triode Q6 composes in parallel by resistance R 38, R48 connects the collector electrode of NPN triode Q6; Capacitor C 11 is connected between the reference voltage end and negative electrode of parallel regulator I C2.
Operating state sample circuit comprises current sampling circuit, current sampling circuit comprises sampling resistor R19 and the amplifying circuit taking amplifier IC3B as main body, the cathode output end mouth VB-of the input termination battery charger of amplifying circuit, cathode output end mouth VB-is by sampling resistor R19 ground connection, the output IS of amplifying circuit meets microcontroller U2 current sampling circuit input IS, and microcontroller U2 determines the operating state of main output circuit by current sampling signal.
Operating state sample circuit also comprises load access test circuit, load access test circuit comprises the 4th bleeder circuit being composed in series by resistance R 45 and R46, the power input Vdd of one termination microcontroller U2 of the 4th bleeder circuit, the load access signal testing end (the 19th pin of U2) of another termination microcontroller U2, the tie point NTC between resistance R 45 and R46 is as the sampled point of external loading access.
The NTC port of load access test circuit is power brick access signal input part, and signal is delivered to microcontroller U2 single-chip microcomputer and detected, and to differentiate the access state of battery pack, sends " standby/work " signal.
When battery does not access or when battery has been full of, charging circuit stops charging, enters holding state.When entering after holding state, microcontroller U2 sends ON/OFF-2 low level signal, close main output switch Q1, output port VB+, VB-no-output voltage, microcontroller U2 sends STB high level Opportunity awaiting control for linear signal (5V) simultaneously, triode Q9 conducting, 5.1V voltage-stabiliser tube Z4 is linked in constant-voltage control circuit, makes the constant-voltage control circuit effect out of hand of main output Vout-1, changes by standby voltage control loop and carries out constant voltage control.
When battery access having been detected, need to charge normal time, microcontroller U2 sends STB low level signal, triode Q9 cut-offs, and voltage-stabiliser tube Z4 is ineffective, and standby voltage control circuit is replaced by the constant-voltage control circuit of main output, main output 42V, boost voltage Vaux output reaches 25V.Meanwhile, microcontroller U2 sends ON/OFF-2 high level signal (5V), and main output switch Q1 conducting allows to batteries charging.
When charging circuit is during in standby, standby voltage control circuit only need maintain the stable of accessory power supply (Vaux) 7.5V, ensure that single-chip microcomputer has the stable operating voltage of 5V, main output loop switch Q1 disconnects, do not need to consider the magnitude of voltage of principal voltage output, so main output voltage is less than 42V.At this moment, green voltage pwm chip LD7576 works under the energy saver mode of low frequency and low duty ratio, operating frequency is very low, about 16---20K left and right, and in discontinuous operation state, make all switching devices (as Q5, D1, D5) switching loss, conduction loss, dummy load (R17) loss has all dropped to minimum.
The above embodiment of the present invention has following beneficial effect:
1. all Voltage-outputs are all from same converter, and the course of work of converter is controlled by " green model PWM chip ", and circuit structure is simple, and cost is low.
2. output circuit has two independently output voltage control loops, at synchronization, only has a voltage control loop to work.When in stand-by operation state, standby output voltage control loop works, and main output voltage control loop is not worked, and main output is closed; When in normal operating conditions, main output voltage control loop works, and standby voltage output control loop is not worked.Two voltage control loops are controlled by standby/working control signal, and standby or normal operating conditions are detected automatically by control circuit, and automatic switchover completes.
3. when in standby, because standby voltage control loop only works, only need to ensure to stablize the output voltage (low pressure) of stand-by circuit, main circuit is closed, can not consider the output situation of principal voltage, green model " PWM chip can work under the energy saver mode of the frequency than lower under normal running conditions, lower duty ratio, makes converter can work in the state of more power saving, realizes low standby power loss energy conservation object.

Claims (8)

1. a switching power circuit, comprises former limit circuit, secondary circuit, transformer and control circuit, and former limit circuit and secondary circuit are by transformer coupled; Former limit circuit comprises the inverter circuit being driven by PWM controller, it is characterized in that, described secondary circuit comprises main output circuit and auxiliary output circuit, and described control circuit comprises microcontroller, main output switch circuit, standby voltage control circuit and operating state sample circuit; The output termination microcontroller of operating state sample circuit, the signal input part of main output switch circuit connects the main output switch control signal output of microcontroller; The signal input part of standby voltage control circuit connects the standby voltage control signal output of microcontroller, the output termination PWM controller control signal input of standby voltage control circuit; Described operating state sample circuit comprises current sampling circuit, described current sampling circuit comprises sampling resistor and amplifying circuit, the negative pole of the input termination output port of amplifying circuit, the negative pole of output port is by sampling resistor ground connection, the output termination microcontroller current sampling circuit input of amplifying circuit; Under stand-by operation state, close main output circuit, the PWM controller of Switching Power Supply is worked under the energy saver mode of low frequency and/or low duty ratio, and the standby voltage of auxiliary output circuit output is lower than the accessory power supply voltage under normal operating conditions.
2. switching power circuit according to claim 1, it is characterized in that, described main output circuit comprises the first secondary winding, the first current rectifying and wave filtering circuit and the output port of transformer, and the output of the first secondary winding connects output port through the first current rectifying and wave filtering circuit; Described main output switch circuit comprises switching tube, the first bleeder circuit, the second bleeder circuit and a NPN triode; The cathode output end of first termination the first current rectifying and wave filtering circuit of described switching tube, the second termination output port positive pole; The first bleeder circuit comprises the first resistance and second resistance of series connection, the first end of a termination switching tube of the first bleeder circuit, and the collector electrode of another termination the one NPN triode, the tie point between the first resistance and the second resistance connects the control utmost point of switching tube; The second bleeder circuit comprises the 3rd resistance and the 4th resistance of series connection, the main output switch control signal output of a termination microcontroller of the second bleeder circuit, other end ground connection; Tie point between the 3rd resistance and the 4th resistance connects the base stage of a NPN triode, the grounded emitter of a NPN triode; The cathode output end ground connection of the first current rectifying and wave filtering circuit.
3. switching power circuit according to claim 2, it is characterized in that, comprise constant-voltage control circuit and optocoupler, described auxiliary output circuit comprises the second secondary winding and second current rectifying and wave filtering circuit of transformer, output termination second current rectifying and wave filtering circuit of the second secondary winding; The cathode output end of the second current rectifying and wave filtering circuit is as the cathode output end of auxiliary output circuit, the cathode output end ground connection of the second current rectifying and wave filtering circuit; Constant-voltage control circuit comprises the 3rd bleeder circuit, offset resistance and the first parallel regulator, and the 3rd bleeder circuit comprises the 5th resistance and the 6th resistance of series connection, the cathode output end of termination first current rectifying and wave filtering circuit of the 3rd bleeder circuit, other end ground connection; Tie point between the 5th resistance and the 6th resistance connects the reference voltage end of the first parallel regulator, the plus earth of the first parallel regulator, and negative electrode connects the cathode output end of the second current rectifying and wave filtering circuit by offset resistance; The anode of optocoupler light-emitting diode connects the cathode output end of the second current rectifying and wave filtering circuit, and negative electrode connects the negative electrode of the first parallel regulator; The collector electrode of optocoupler phototriode connects PWM controller control signal input, grounded emitter.
4. switching power circuit according to claim 3, is characterized in that, described standby voltage control circuit comprises voltage-stabiliser tube and the 2nd NPN triode, and the negative electrode of voltage-stabiliser tube connects the negative electrode of optocoupler light-emitting diode; The base stage of the 2nd NPN triode connects the standby voltage control signal output of microcontroller, grounded emitter, and collector electrode connects the anode of voltage-stabiliser tube.
5. switching power circuit according to claim 1, it is characterized in that, comprise linear voltage-stabilizing circuit, described linear voltage-stabilizing circuit comprises the 3rd NPN triode, the 4th bleeder circuit, base resistance and the second parallel regulator, the emitter of one termination the 3rd NPN triode of the 4th bleeder circuit, other end ground connection; The 4th bleeder circuit comprises the 7th resistance and the 8th resistance of series connection, and the tie point between the 7th resistance and the 8th resistance connects the reference voltage end of the second parallel regulator; The negative electrode of the second parallel regulator connects the base stage of the 3rd NPN triode, plus earth; The collector electrode of the 3rd NPN triode connects the cathode output end of the second current rectifying and wave filtering circuit, and emitter connects the power input of microcontroller; The base stage of the 3rd NPN triode connects the collector electrode of the 3rd NPN triode by base resistance.
6. switching power circuit according to claim 1, it is characterized in that, described operating state sample circuit comprises load access test circuit, and described load access test circuit comprises the 4th bleeder circuit, and the 4th bleeder circuit comprises the 7th resistance and the 8th resistance of series connection; The power input of one termination microcontroller of the 4th bleeder circuit, the load access signal testing end of another termination microcontroller, the tie point between the 7th resistance and the 8th resistance is as the sampled point of load access.
7. switching power circuit according to claim 1, is characterized in that, described transformer T1 is flyback transformer.
8. switching power circuit according to claim 1, is characterized in that, described switching power circuit is battery charger.
CN201210047494.XA 2012-02-28 2012-02-28 Switching power circuit CN102594124B (en)

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