CN217282741U

CN217282741U - Switching power supply circuit

Info

Publication number: CN217282741U
Application number: CN202220911987.2U
Authority: CN
Inventors: 朱钦柳
Original assignee: Gospower Digital Technology Shenzhen Co ltd
Current assignee: Gospower Digital Technology Shenzhen Co ltd
Priority date: 2022-04-20
Filing date: 2022-04-20
Publication date: 2022-08-23
Anticipated expiration: 2032-04-20

Abstract

The utility model discloses a switching power supply circuit, which comprises a main circuit and a control circuit, wherein the control circuit comprises a microcontroller, the control circuit comprises two monitoring modules, and each monitoring module comprises a first voltage division circuit, a first resistor and an output terminal matched with a plug terminal; the first end of the first voltage division circuit is connected with the anode of the low-voltage direct-current power supply, and the second end of the first voltage division circuit is grounded; the first end of the first resistor is connected with the output end of the first voltage division circuit, the second end of the first resistor is connected with the first pin of the output terminal, and the second pin of the output terminal is grounded; the first end of the first resistor is connected with an output pin of the monitoring module; the output pin of the first monitoring module is connected with the first input pin of the microcontroller, and the output pin of the second monitoring module is connected with the second input pin of the microcontroller; and a first control signal output pin of the microcontroller is connected with a control end of the feedback circuit, and a feedback signal output end of the feedback circuit is connected with a feedback signal input pin of the pulse width modulation chip. The utility model discloses intelligent degree is high, be difficult for appearing voltage mistake output.

Description

Switching power supply circuit

Technical Field

The utility model relates to a switching power supply especially relates to a switching power supply circuit.

Background

A switching power supply is a high-frequency power conversion device, and functions to convert one form of electric energy (AC/DC) into a required direct current. Wherein, the output voltage switching mainly relates to the situation that different output voltages are needed,

for example, in some application scenarios, two different output voltages need to be used for the same device, and the two output voltages are only used for one of the two different output voltages in a certain period of time, so that the resource idleness is reduced based on cost and optimized resource configuration, and the same switching power supply can be sampled to realize different output voltages. The traditional voltage switching mode realizes the switching of voltage by adopting the dial switch, and the realization mode has the main problems that not only the dial switch is easy to damage, but also the voltage is output by mistake, and the voltage is not fool-proof, is not intelligent and the like. That is, the dial switch voltage switching circuit cannot identify which way the dial switch is connected to, and cannot display the output voltage.

Disclosure of Invention

The to-be-solved technical problem of the utility model is to provide a switching power supply circuit that voltage mistake output is difficult for appearing.

In order to solve the technical problem, the utility model discloses a technical scheme be, a switching power supply circuit, including main circuit and control circuit, control circuit includes microcontroller, the main circuit includes AC input rectification filter circuit, power conversion circuit, output rectification filter circuit and feedback circuit, power conversion circuit includes PWM pulse generation circuit and contravariant power switch circuit, PWM pulse generation circuit includes the pulse width modulation chip, control circuit includes two monitoring module and at least one plug terminal, monitoring module includes first divider circuit, first resistance and the output terminal who matches with plug terminal; the first end of the first voltage division circuit is connected with the anode of the low-voltage direct-current power supply, and the second end of the first voltage division circuit is grounded; the first end of the first resistor is connected with the output end of the first voltage division circuit, the second end of the first resistor is connected with the first pin of the output terminal, and the second pin of the output terminal is grounded; the first end of the first resistor is connected with an output pin of the monitoring module; the output pin of the first monitoring module is connected with the first input pin of the microcontroller, and the output pin of the second monitoring module is connected with the second input pin of the microcontroller; and a first control signal output pin of the microcontroller is connected with a control end of the feedback circuit, and a feedback signal output end of the feedback circuit is connected with a feedback signal input pin of the pulse width modulation chip.

In the switching power supply circuit, the feedback circuit comprises the first optocoupler, the second voltage division circuit and the controllable precise voltage stabilizing source. The second voltage division circuit is connected between the anode and the cathode of the direct current output end of the output rectification filter circuit; the anode of the first optocoupler light-emitting diode is connected with the anode of the direct current output end of the output rectifying and filtering circuit, the cathode of the first optocoupler light-emitting diode is connected with the cathode of the controllable precise voltage stabilizing source, the anode of the controllable precise voltage stabilizing source is connected with the cathode of the direct current output end of the output rectifying and filtering circuit, the reference electrode of the controllable precise voltage stabilizing source is connected with the output end of the second voltage dividing circuit, and the collector of the second optocoupler phototriode is connected with the output end of the second voltage dividing circuit through a second resistor; an emitter of the second optical coupling phototriode is connected with a negative electrode of a direct current output end of the output rectifying and filtering circuit, an anode of the second optical coupling light-emitting diode serving as a control end of the feedback circuit is connected with a first control signal output pin of the microcontroller, and a cathode of the second optical coupling light-emitting diode is grounded; and the collector of the first optocoupler phototriode is connected with a feedback signal input pin of the pulse width modulation chip, and the emitter is grounded.

In the switching power supply circuit, the monitoring module includes a double-series-connection switching diode, a first capacitor and a second capacitor, an anode of the double-series-connection switching diode is grounded, a cathode of the double-series-connection switching diode is connected to the first end of the first voltage-dividing circuit, a middle pin of the double-series-connection switching diode is connected to the output end of the first voltage-dividing circuit, the first capacitor is connected between the first end of the first resistor and the ground, and the second capacitor is connected between the second end of the first resistor and the ground.

In the switching power supply circuit, the control circuit comprises two indicator light modules, each indicator light module comprises an LED lamp, an NPN triode and a first current-limiting resistor, the anode of the LED lamp is connected with the anode of the LED power supply through the first current-limiting resistor, the cathode of the LED lamp is connected with the collector of the NPN triode, and the emitter of the NPN triode is grounded; the base electrode of the NPN triode is connected with the control pin of the indicator light module; the control pin of the first indicator light module is connected with the first indicator signal output pin of the microcontroller, and the control pin of the second indicator light module is connected with the second indicator signal output pin of the microcontroller.

In the switching power supply circuit, the inversion power switching circuit comprises the transformer and the MOS tube, and the first end of the primary winding of the transformer is connected with the anode of the output end of the AC input rectification filter circuit; the drain electrode of the MOS tube is connected with the second end of the primary winding of the transformer, the source electrode of the MOS tube is grounded, and the grid electrode of the MOS tube is connected with a PWM signal output pin of the pulse width modulation chip; the input end of the output rectifying filter circuit is connected with the secondary winding of the transformer.

In the switching power supply circuit, the output rectifying and filtering circuit comprises a rectifying diode and a filtering capacitor, the second end of the primary winding of the transformer is a homonymy end, the homonymy end of the secondary winding of the transformer is connected with the anode of the rectifying diode, the synonym end of the secondary winding of the transformer is connected with the cathode of the direct-current output end of the output rectifying and filtering circuit, and the cathode of the rectifying diode is connected with the anode of the direct-current output end of the output rectifying and filtering circuit; the filter capacitor is connected between the positive electrode and the negative electrode of the direct current output end of the output rectifying filter circuit.

In the switching power supply circuit, the control circuit comprises the third optocoupler, the diode and the two plug-in terminals, the transformer comprises the auxiliary winding, and the second end of the primary winding of the transformer is the dotted terminal; the anode of the third optical coupler light-emitting diode is connected with the second control signal output end of the microcontroller, and the cathode of the third optical coupler light-emitting diode is grounded; the dotted terminal of the auxiliary winding is connected with the anode of the diode, the cathode of the diode is connected with the collector of the third optocoupler phototriode, and the emitter of the phototriode is connected with the power input pin of the pulse width modulation chip.

In the switching power supply circuit, the control circuit comprises a second current-limiting resistor, a third capacitor and a voltage regulator tube, and the second current-limiting resistor is connected between the cathode of the diode and the collector of the third optocoupler phototriode; the cathode of the voltage-stabilizing tube is connected with the collector of the third optocoupler phototriode, and the anode is grounded; the third capacitor is connected in parallel with the voltage regulator tube.

The utility model discloses voltage error output is difficult for appearing.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a schematic block diagram of a switching power supply circuit according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of the main circuit of the switching power supply circuit according to the embodiment of the present invention.

Fig. 3 is a circuit diagram of a first monitoring module according to an embodiment of the present invention.

Fig. 4 is a circuit diagram of a second monitoring module according to an embodiment of the present invention.

Fig. 5 is a circuit diagram of two indicator light modules according to an embodiment of the present invention.

Fig. 6 is a circuit diagram of a first mating terminal according to an embodiment of the present invention.

Fig. 7 is a circuit diagram of a second connection terminal according to an embodiment of the present invention.

Fig. 8 is a partial wiring diagram of a microcontroller according to an embodiment of the present invention.

Detailed Description

The embodiment of the utility model provides a switching power supply circuit's structure and principle are shown as figure 1 to figure 8, including main circuit and control circuit. The main circuit comprises an AC input rectifying and filtering circuit, a power conversion circuit, an output rectifying and filtering circuit and a feedback circuit.

The control circuit comprises a microcontroller MCU (STM 32F334R8T 6), two monitoring modules, two indicator light modules, a third optocoupler, a diode D6, a second current-limiting resistor R7, a voltage regulator tube Z7 and two plug-in terminals (not shown in the figure).

An AC input rectifying and filtering circuit (not shown) passes 220V AC through a bridge rectifying and filtering circuit to obtain a dc high voltage VDC + of about + 300V.

The power conversion circuit comprises a PWM pulse generation circuit and an inversion power switch circuit. The PWM pulse generating circuit includes a pulse width modulation chip U20 (OB 2276A), and the inverter power switching circuit includes a transformer T1 and a MOS transistor Q1. The high direct current voltage is chopped by an MOS transistor Q1 and is reduced by a high-frequency transformer T1 to become rectangular wave voltage with the frequency of 65kHz, and stable direct current output voltage is obtained through output rectification and filtering.

The first end (different name end) of the primary winding T1B of the transformer T1 is connected with the anode of the output end of the AC input rectifying and filtering circuit. The drain of the MOS transistor Q1 is connected to the second terminal (end of the same name) of the primary winding T1B of the transformer T1, the source is connected to the negative (ground) of the output terminal of the AC input rectifying and filtering circuit, and the GATE is connected to the PWM signal output pin GATE of the pulse width modulation chip U20. The input end of the output rectifying and filtering circuit is connected with the secondary winding T1C of the transformer T1.

The output rectifying and filtering circuit comprises rectifying diodes D1 and D3 and a filter capacitor C22, the same name of a secondary winding T1C of a transformer T1 is connected with the anodes of the rectifying diodes D1 and D3, the different name of the secondary winding T1C of the transformer T1 is connected with the cathode of the direct-current output end of the output rectifying and filtering circuit, the cathodes of the rectifying diodes D1 and D3 are connected with the anode of the direct-current output end of the output rectifying and filtering circuit, and the filter capacitor C22 is connected between the anode and the cathode of the direct-current output end of the rectifying and filtering circuit.

As shown in fig. 3 and 6, the first monitoring module includes a voltage dividing circuit composed of resistors R351 and R352, a resistor R355, a double series-connected switching diode D42(BAV 99), a capacitor C175, a capacitor C173, and an output terminal J1. One end of the voltage dividing circuit resistor R351 is connected to the low-voltage dc power supply positive electrode SMCU _3.3V, and one end of the voltage dividing circuit resistor R352 is grounded. The first terminal of the resistor R355 is connected to the output terminal of the voltage divider circuit (the connection point of the resistors R351 and R352), the second terminal of the resistor R355 is connected to the first pin 12VDET of the output terminal J1, and the second pin of the output terminal J1 is grounded. A first terminal of the resistor R355 is connected to the output pin 12DET of the monitoring module. The output pin 12DET of the first monitoring module is connected to a first input pin (pin 41) of the microcontroller. The anode of the double-series switch diode D42 is grounded, the cathode is connected to one end of the voltage divider circuit R351, namely, the low-voltage dc power supply anode SMCU _3.3V, the middle pin of the double-series switch diode D42 is connected to the output end of the voltage divider circuit (the connection point of the resistors R351 and R352), the capacitor C175 is connected between the first end of the resistor R355 and the ground, and the capacitor C173 is connected between the second end of the resistor R355 and the ground.

As shown in fig. 4 and 7, the second monitoring module includes a voltage dividing circuit composed of resistors R353 and R354, a resistor R356, a double series switching diode D41(BAV 99), a capacitor C176, a capacitor C174, and an output terminal J2. One end of the voltage division circuit resistor R353 is connected with the anode of the low-voltage direct-current power supply SMCU _3.3V, and one end of the voltage division circuit resistor R354 is grounded. The first terminal of the resistor R356 is connected to the output terminal of the voltage divider circuit (the connection point of the resistors R353 and R354), the second terminal of the resistor R356 is connected to the first pin 24VDET of the output terminal J2, and the second pin of the output terminal J2 is grounded. A first terminal of the resistor R356 is connected to the output pin 24DET of the monitoring module. The output pin 24DET of the second monitoring module is connected to a second input pin (pin 42) of the microcontroller. The anode of the double-series switch diode D41 is grounded, the cathode is connected to one end of the voltage divider circuit R353, i.e., the low-voltage dc power supply positive electrode SMCU _3.3V, the middle pin of the double-series switch diode D41 is connected to the output end of the voltage divider circuit (the connection point of the resistor R353 and the resistor R354), the capacitor C176 is connected between the first end of the resistor R356 and ground, and the capacitor C174 is connected between the second end of the resistor R356 and ground.

The SMCU — 3.3V is the supply voltage for the microcontroller, which can be powered by VDD through a linear regulation.

The 12DET is connected with a pin 41 of the microcontroller, the 24VDET is connected with a pin 42 of the microcontroller, the two pins are input pins of the microcontroller, the input is 1 when the high level is high, and the input is 0 when the low level is low; 12VDET and 24VDET are input pins, the 12VDET is connected with the 2 end of a J1 terminal, the 24VDET is connected with the 2 end of a J2 terminal, when a plug terminal is connected, the 12VDET and the 24VDET are in short circuit with AGND, the input is 0 level, and when no plug terminal is connected, the 12VDET and the 24VDET are in a high-impedance state.

The ECU + is a connection network which is connected to the anode of the filter capacitor C22 in FIG. 2, and the AGD is connected to the cathode of the filter capacitor C22. The dual series switching diodes D41, D42 clamp the microcontroller, and when the microcontroller has a back voltage, the dual series switching diodes D41, D42 can force the clamping at two diode levels to prevent burning out the microcontroller.

The feedback circuit comprises a first optical coupler OT1, a second optical coupler OT4, a controllable precision voltage-stabilizing source U2 (AZ 431) and a second voltage-dividing circuit consisting of resistors R6, R8 and R11. The second voltage division circuit is connected between the positive electrode and the negative electrode of the direct current output end of the output rectifying and filtering circuit. The anode of a first optical coupler OT1 light emitting diode OT1-B is connected with the anode of the direct current output end of the output rectifying and filtering circuit, the cathode of a first optical coupler OT1 light emitting diode OT1-B is connected with the cathode of a controllable precision voltage-stabilizing source U2, the anode of a controllable precision voltage-stabilizing source U2 is connected with the cathode of the direct current output end of the output rectifying and filtering circuit, the reference electrode of a controllable precision voltage-stabilizing source U2 is connected with the output end of a second voltage-dividing circuit (the connection point of a resistor R6 and resistors R8 and R11), and the collector of a second optical coupler OT4 phototriode OT4-A is connected with the reference electrode of a controllable precision voltage-stabilizing source U2 and the output end of the second voltage-dividing circuit through resistors R43 and R97 which are connected in parallel. An emitter of a phototransistor OT4-A of a second optocoupler OT4 is connected with a negative electrode of a direct current output end of the output rectifying and filtering circuit, an anode of a second optocoupler OT4 light-emitting diode OT4-B serving as a control end of a feedback circuit is connected with a first control signal output pin (pin 51) of the microcontroller, and a cathode of the second optocoupler OT4 light-emitting diode OT4-B is grounded. The collector of a first optical coupler OT1 phototriode OT1-A is connected with a feedback signal input pin FB of a pulse width modulation chip U20, and the emitter of the first optical coupler OT1 phototriode OT1-A is grounded. The principle of the feedback circuit voltage stabilization is that the output direct current voltage of the rectifying and filtering circuit is output, a sampling feedback circuit consisting of a first optical coupler OT1 light emitting diode OT1-B and a controllable precise voltage stabilization source U2 feeds back the sampling value of the output voltage to a pin 7 of OB2276, namely a pin FB, the sampling voltage is compared with the internal sawtooth wave voltage in the pin FB through a comparator, a PWM driving signal with adjustable pulse width is generated, the PWM driving signal is used for controlling the on-off time of a switching power tube Q1, the on-off state of a high-frequency transformer is determined, and therefore the purpose of outputting and stabilizing the voltage is achieved.

When OT4-A is in a floating state, the output voltage Vo = [1+ R6/(R8// R11) ] Vref, Vref is the reference voltage of the controllable precision voltage regulator U2 (AZ 431), and when OT4-A is in a conducting state, Vo = [1+ R6/(R8// R11// R43// R97) ] Vref. Choosing different values for R6, R8, R11, R43, and R97 can result in any voltage output ranging from 2.5V to 36V.

As shown in fig. 5, the first indicator light module includes an indicator light LED5, an NPN transistor Q35, and a current limiting resistor R366, an anode of the indicator light LED5 is connected to the anode VDD of the LED power supply via the current limiting resistor R366, a cathode of the indicator light LED5 is connected to the collector of the NPN transistor Q35, and an emitter of the NPN transistor Q35 is grounded. The base of the NPN transistor Q35 is connected to the control pin eciled 12 of the first indicator light module. The control pin eclled 12 of the first indicator light module is connected to a first indicator signal output pin (not shown) of the microcontroller,

as shown in fig. 5, the second indicator light module includes an indicator light LED6, an NPN transistor Q36, and a current limiting resistor R369, an anode of the indicator light LED6 is connected to the anode VDD of the LED power supply via the current limiting resistor R369, a cathode of the indicator light LED6 is connected to the collector of the NPN transistor Q36, and an emitter of the NPN transistor Q36 is grounded. The base of the NPN transistor Q36 is connected to the control pin eciled 24 of the second indicator light module. Control pin ECULED24 of the second indicator light module is connected to a second indicator signal output pin (not shown) of the microcontroller.

VDD is the supply voltage for the indicator light LED5, LED6 light, available from the auxiliary winding T1-A of T1, or from a separate auxiliary power supply.

The anode of the third light-emitting diode OT6-B is connected with a second control signal output pin (pin 54) of the microcontroller, and the cathode of the third light-emitting diode OT6 OT6-B is grounded. The dotted terminal of the auxiliary winding T1A is connected with the anode of a diode D6, the cathode of a diode D6 is connected with the collector of a third opto-coupler OT6 phototriode OT6-A through a current-limiting resistor R7, and the emitter of the phototriode OT6-A is connected with a power input pin VCC of a pulse width modulation chip U20. The cathode of the voltage regulator tube Z7 is connected with the collector of a third opto-coupler OT6 phototriode OT6-A, and the anode is grounded. A third capacitor C4 is connected in parallel with the zener diode Z7.

The utility model discloses above embodiment switching power supply circuit's working process as follows:

when the first plug terminal is connected to the output terminal J1 manually, the 2-terminal of the output terminal J1 is connected to 12VDET in the first monitoring module, the 1-terminal of the output terminal J1 is connected to AGND in the module 1 (the output terminal J1 has fool-proof function and is a terminal of 3PIN, and is 1-3 terminals respectively), the MCU outputs a voltage V1 according to the 12DET level change of the first monitoring module, and the indicator light LED5 is lit:

when only the output terminal J1 of the first monitoring module is connected to the plug terminal, one end of the R355 of the first monitoring module is short-circuited to ground, the other end is connected to the voltage dividing resistor R352, the voltage across the voltage dividing resistor R352 is 3.3 × R352/(R351+ R352// R355) V (the power supply of the microcontroller is 3.3V), the voltage across the voltage dividing resistor R352 of the first monitoring module is at a low level, the voltage across the voltage dividing resistor R354 of the second monitoring module is 3.3 × R354/(R353+ R354) V, and the voltage across the voltage dividing resistor R354 of the second monitoring module is at a high level. The microcontroller judges that a plug terminal is connected to the first monitoring module, a first control signal output pin (51 pin) of the microcontroller outputs a low level, the second optical coupler OT4 is in an off state, the output voltage of the output rectifying and filtering circuit is output voltage V1, the voltage output of V1 is 2.5 x [1 xR 6/(R8// R11) ], and only an indicator light LED5 of the first LED module is highlighted at the moment.

When the second plug terminal is connected to the output terminal J2 manually, the 2-terminal of the output terminal J2 is connected to 24VDET in the second monitoring module, the 4-terminal of the output terminal J2 is connected to AGND in the module 2 (the output terminal 2 has fool-proof function, and is a 4PIN terminal, and is 1-4 terminals respectively), the MCU outputs a voltage V2 according to the level change of the second monitoring module, and the indicator light LED6 lights up:

when only the output terminal J2 of the second monitoring module is connected to the plug terminal, one end of the R356 of the second monitoring module is shorted to ground, the other end is connected to the voltage dividing resistor R354, the voltage across the voltage dividing resistor R354 is 3.3 × R354/(R353+ R352// R356) V (the power supply of the microcontroller is 3.3V), the voltage across the voltage dividing resistor R354 of the second monitoring module is at a low level, the voltage across the voltage dividing resistor R352 of the first monitoring module is 3.3 × R352/(R351+ R352) V, and the voltage across the voltage dividing resistor R352 of the first monitoring module is at a high level. The microcontroller judges that a plug terminal is connected into the second monitoring module, a first control signal output pin (51 pin) of the microcontroller outputs a high level, a second optical coupler OT4 is in a conducting state, the output voltage of the output rectifying and filtering circuit is output voltage V2, the voltage output of V2 is 2.5 x [1 xR 6/(R8// R11// R43// R97) ], and only an indicator light LED6 of the second LED module is highlighted at the moment.

When the first plug terminal 1 is connected to the output terminal J1 and the second plug terminal is connected to the output terminal J2 manually, the levels of 12DET and 24DET in the first monitoring module and the second monitoring module jump, the MCU closes the output according to the level changes of the first monitoring module and the second monitoring module, and the indicator lights LED5 and LED6 are turned off:

when the output terminal J1 of the first monitoring module and the output terminal J2 of the second monitoring module both have access plug terminals, one end of the resistor R355 of the first monitoring module is short-circuited to the ground, the other end is connected with a voltage dividing resistor R352, and the voltage on the voltage dividing resistor R352 is 3.3 multiplied by R352/(R351+ R352// R355) V (the power supply of the microcontroller is 3.3V); one end of the R356 of the second monitoring module is shorted to ground, the other end is connected to the voltage dividing resistor R354, the voltage across the voltage dividing resistor R354 is 3.3 × R354/(R353+ R354// R356) V, at this time, the voltage dividing resistor R352 of the first monitoring module and the voltage across the voltage dividing resistor R354 of the second monitoring module are both at low level, when the microcontroller monitors that the voltage dividing resistor R352 and the voltage dividing resistor R354 are both at low level, the output terminal J1 of the first monitoring module and the output terminal J2 of the second monitoring module are both connected to the plug terminal by default, at this time, the second control signal output pin (pin 54) of the controller outputs low level, the third opto-coupled OT6 phototransistor OT6-a turns off the auxiliary power supply of the U20, turns off the output of the output rectifying and filtering circuit, and simultaneously, the indicator lights LED5 and LED6 are both turned off.

When the output terminals J1 and J2 connected with the first monitoring module and the second monitoring module are not connected with the plug terminals, the default output voltage V1 and the indicator light LED5 and LED6 are extinguished:

when the plug terminals are not connected to the output terminals J1 and J2, the normal voltage of the voltage dividing resistor R352 of the first monitoring module is 3.3 × R352/(R351+ R352) V (the power supply of the microcontroller is 3.3V), the normal voltage of the voltage dividing resistor R354 of the second monitoring module is 3.3 × R354/(R353+ R354) V, the normal voltage is high level of the microcontroller, when the microcontroller monitors that the voltage dividing resistor R352 and the voltage dividing resistor R354 are both high level, the default plug terminals are not connected to the output terminals J1 and J2, the first control signal output pin of the microcontroller is low level, the second optical coupler OT4 is in an off state by default, the output voltage of the output rectifying and filtering circuit is output voltage V1 by default, the voltage output of V1 is 2.5 × 1 × R6/(R8// R11) ], and the lights of the LED5 and the LED6 are both off.

The utility model discloses switching of switching power supply circuit output voltage of above embodiment is convenient and reliable, and control is accurate, is difficult for appearing voltage mistake output, and intelligent degree is high.

Claims

1. A switching power supply circuit comprises a main circuit and a control circuit, wherein the control circuit comprises a microcontroller, the main circuit comprises an AC input rectifying filter circuit, a power conversion circuit, an output rectifying filter circuit and a feedback circuit, the power conversion circuit comprises a PWM pulse generating circuit and an inversion power switching circuit, and the PWM pulse generating circuit comprises a pulse width modulation chip; the first end of the first voltage division circuit is connected with the anode of the low-voltage direct-current power supply, and the second end of the first voltage division circuit is grounded; the first end of the first resistor is connected with the output end of the first voltage division circuit, the second end of the first resistor is connected with the first pin of the output terminal, and the second pin of the output terminal is grounded; the first end of the first resistor is connected with an output pin of the monitoring module; the output pin of the first monitoring module is connected with the first input pin of the microcontroller, and the output pin of the second monitoring module is connected with the second input pin of the microcontroller; and a first control signal output pin of the microcontroller is connected with a control end of the feedback circuit, and a feedback signal output end of the feedback circuit is connected with a feedback signal input pin of the pulse width modulation chip.

2. The switching power supply circuit according to claim 1, wherein the feedback circuit comprises a first optical coupler, a second voltage division circuit and a controllable precise voltage-stabilizing power supply, and the second voltage division circuit is connected between a positive electrode and a negative electrode of the direct current output end of the output rectifying and filtering circuit; the anode of the first optical coupling light-emitting diode is connected with the anode of the direct current output end of the output rectifying and filtering circuit, the cathode of the first optical coupling light-emitting diode is connected with the cathode of the controllable precise voltage-stabilizing source, the anode of the controllable precise voltage-stabilizing source is connected with the cathode of the direct current output end of the output rectifying and filtering circuit, the reference electrode of the controllable precise voltage-stabilizing source is connected with the output end of the second voltage-dividing circuit, and the collector of the second optical coupling phototriode is connected with the output end of the second voltage-dividing circuit through a second resistor; an emitter of the second optical coupling phototriode is connected with a negative electrode of a direct current output end of the output rectifying and filtering circuit, an anode of the second optical coupling light-emitting diode serving as a control end of the feedback circuit is connected with a first control signal output pin of the microcontroller, and a cathode of the second optical coupling light-emitting diode is grounded; and the collector of the first optocoupler phototriode is connected with a feedback signal input pin of the pulse width modulation chip, and the emitter is grounded.

3. The switching power supply circuit according to claim 1, wherein the monitoring module comprises a dual series-connected switching diode, a first capacitor and a second capacitor, an anode of the dual series-connected switching diode is grounded, a cathode of the dual series-connected switching diode is connected to the first end of the first voltage divider circuit, a middle pin of the dual series-connected switching diode is connected to the output end of the first voltage divider circuit, the first capacitor is connected between the first end of the first resistor and the ground, and the second capacitor is connected between the second end of the first resistor and the ground.

4. The switching power supply circuit according to claim 1, wherein the control circuit comprises two indicator light modules, each indicator light module comprises an LED lamp, an NPN triode and a first current limiting resistor, an anode of the LED lamp is connected with an anode of the LED power supply through the first current limiting resistor, a cathode of the LED lamp is connected with a collector of the NPN triode, and an emitter of the NPN triode is grounded; the base electrode of the NPN triode is connected with the control pin of the indicator light module; the control pin of the first indicator light module is connected with the first indicator signal output pin of the microcontroller, and the control pin of the second indicator light module is connected with the second indicator signal output pin of the microcontroller.

5. The switching power supply circuit according to claim 1, wherein the inverter power switching circuit comprises a transformer and a MOS transistor, and a first end of a primary winding of the transformer is connected to a positive electrode of an output end of the AC input rectifying and filtering circuit; the drain electrode of the MOS tube is connected with the second end of the primary winding of the transformer, the source electrode of the MOS tube is grounded, and the grid electrode of the MOS tube is connected with a PWM signal output pin of the pulse width modulation chip; the input end of the output rectifying filter circuit is connected with the secondary winding of the transformer.

6. The switching power supply circuit according to claim 5, wherein the output rectifying and filtering circuit comprises a rectifying diode and a filtering capacitor, the second end of the primary winding of the transformer is a dotted terminal, the dotted terminal of the secondary winding of the transformer is connected with the anode of the rectifying diode, the dotted terminal of the secondary winding of the transformer is connected with the cathode of the DC output end of the output rectifying and filtering circuit, and the cathode of the rectifying diode is connected with the anode of the DC output end of the output rectifying and filtering circuit; the filter capacitor is connected between the positive electrode and the negative electrode of the direct current output end of the output rectifying filter circuit.

7. The switching power supply circuit according to claim 1, wherein the control circuit comprises a third optocoupler, a diode and two said plug terminals, the transformer comprises an auxiliary winding, and the second end of the primary winding of the transformer is a dotted terminal; the anode of the third optical coupler light-emitting diode is connected with the second control signal output end of the microcontroller, and the cathode of the third optical coupler light-emitting diode is grounded; the dotted terminal of the auxiliary winding is connected with the anode of the diode, the cathode of the diode is connected with the collector of the third optocoupler phototriode, and the emitter of the phototriode is connected with the power input pin of the pulse width modulation chip.

8. The switching power supply circuit according to claim 7, wherein the control circuit comprises a second current-limiting resistor, a third capacitor and a voltage regulator tube, the second current-limiting resistor is connected between the cathode of the diode and the collector of the third optocoupler phototransistor; the cathode of the voltage-stabilizing tube is connected with the collector of the third optocoupler phototriode, and the anode of the voltage-stabilizing tube is grounded; the third capacitor is connected in parallel with the voltage regulator tube.