An isolated PWM voltage conversion circuit

Abstract

The present invention discloses an isolated PWM voltage conversion circuit, which relates to the field of voltage conversion. The isolated PWM voltage conversion circuit comprises: a voltage conversion module, which is used to output stable direct current after the electric energy generated by solar power generation passes through an LLC circuit or a flyback circuit to supply a load; compared with the prior art, the beneficial effects of the present invention are: the voltage conversion module of the present invention is powered by the LLC circuit or the flyback circuit; it is ensured that when the light is strong, the flyback circuit works, and a wide voltage input can be achieved; when the light is dim, the LLC circuit works, and high-efficiency soft switching is performed to reduce losses, ensuring that sufficient electric energy is still output to maintain the operation of the load when the light is dim; a voltage detection module is provided, which needs to reach an upper threshold value before triggering when the output of a high level is triggered, and needs to be below a lower threshold value before triggering when the output of the high level stops, thereby avoiding frequent switching of the LLC circuit and the flyback circuit and increasing the service life of the circuit.

Description

Technical Field

[0001] The present invention relates to the field of voltage conversion, in particular to an isolated PWM voltage conversion circuit. Background Art

[0002] With the development of society, solar power supply is becoming more and more common. Solar power generation can reduce the air pollution caused by coal-fired and oil-fired power generation, and improve human health and living environment.

[0003] It should be noted that solar power generation is affected by sunlight, resulting in unstable power generation. If solar power generation is selected to be powered by an LLC circuit, although the LLC circuit can achieve efficient soft switching and reduce losses, it has high requirements for the input voltage range and its applicability is limited. If solar power generation is selected to be powered by a flyback circuit, although the flyback circuit can achieve a wide input voltage range, it will lose more energy when the sunlight is weak, making it difficult to ensure the normal operation of the load.

[0004] In summary, the existing LLC circuit and flyback circuit are not practical enough when applied to solar power generation and need to be improved. Summary of the Invention

[0005] The object of the present invention is to provide an isolated PWM voltage conversion circuit to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An isolated PWM voltage conversion circuit, comprising:

[0008] The voltage conversion module is used to convert the solar-generated electricity into stable DC power after passing through the LLC circuit or flyback circuit to supply the load.

[0009] The voltage detection module is used to determine whether the voltage of the solar power generation has reached an upper threshold value, and output a control signal to the conversion control module when the upper threshold value is reached, and stop outputting the control signal to the conversion control module when the voltage of the solar power generation is lower than the lower threshold value;

[0010] A conversion control module, configured to control the flyback circuit of the voltage conversion module to operate when a control signal is received, and to control the LLC circuit of the voltage conversion module to operate when no control signal is received;

[0011] The first output end of the voltage conversion module is connected to the first input end of the conversion control module (common point A1), the second output end of the voltage conversion module is connected to the input end of the voltage detection module (common point A3), the first output end of the voltage detection module is connected to the second input end of the conversion control module (common point A2), and the output end of the conversion control module is connected to the input ends (PWM1, PWM2, PWM3) of the voltage conversion module.

[0012] As a further solution of the present invention: the voltage conversion module includes:

[0013] The two-in-one output unit is used to output the electric energy generated by solar power generation to the rectification and filtering unit after passing through the LLC circuit or the flyback circuit;

[0014] The voltage detection unit is used to detect the voltage generated by solar power generation and output it to the voltage detection module;

[0015] The rectifier and filter unit is used to convert the input unstable current into stable direct current to supply the load;

[0016] The voltage feedback unit is used to sample the voltage output to the load and feed it back to the conversion control module;

[0017] The first output end of the two-in-one output unit is connected to the input end of the voltage detection unit, the output end of the voltage detection unit is connected to the input end of the voltage detection module (common point A3), the second output end of the two-in-one output unit is connected to the input end of the rectification and filtering unit, the output end of the rectification and filtering unit is connected to the input end of the voltage feedback unit, and the output end of the voltage feedback unit is connected to the first input end of the conversion control module (common point A1).

[0018] As a further solution of the present invention: the two-in-one output unit includes a solar cell, a first MOS transistor, a second MOS transistor, a third MOS transistor, a first inductor, a second inductor, a first capacitor, and a transformer. The negative electrode of the solar cell is grounded, the positive electrode of the solar cell is connected to the D electrode of the second MOS transistor and the input end of the voltage detection unit, the S electrode of the second MOS transistor is connected to the D electrode of the third MOS transistor and one end of the first inductor, the S electrode of the third MOS transistor is grounded, the other end of the first inductor is connected to one end of the second inductor and one end of the input end of the transformer, the other end of the input end of the transformer is connected to the other end of the second inductor, one end of the first capacitor, and the D electrode of the first MOS transistor, the S electrode of the first MOS transistor is grounded, the other end of the first capacitor is grounded, the G electrode of the first MOS transistor is connected to the output end of the conversion control module, the G electrode of the second MOS transistor is connected to the output end of the conversion control module, the G electrode of the third MOS transistor is connected to the output end of the conversion control module, and the output end of the transformer is connected to the input end of the rectifier and filter unit.

[0019] As a further solution of the present invention: the voltage detection unit includes a first resistor and a first potentiometer, one end of the first resistor is connected to the first output end of the two-in-one output unit, the other end of the first resistor is connected to one end of the first potentiometer and the input end of the voltage detection module, and the other end of the first potentiometer is grounded.

[0020] As a further solution of the present invention: the rectifier and filtering unit includes a first diode, a second diode, a second capacitor, and a second resistor. The positive pole of the first diode is connected to the first end of the output end of the transformer, the positive pole of the second diode is connected to the second end of the output end of the transformer, one end of the second capacitor is connected to one end of the second resistor and the third end of the output end of the transformer, and the negative pole of the first diode is connected to the negative pole of the second diode, the other end of the second capacitor, the other end of the second resistor, and the input end of the voltage feedback unit.

[0021] As a further solution of the present invention: the voltage feedback unit includes a third resistor, a second potentiometer, a third capacitor, and a voltmeter, one end of the third resistor is connected to the output end of the rectifier and filter unit, the other end of the third resistor is connected to one end of the second potentiometer, one end of the third capacitor, one end of the voltmeter, and the first input end of the conversion control module, the other end of the second potentiometer is grounded, the other end of the third capacitor is grounded, and the other end of the voltmeter is grounded.

[0022] As a further solution of the present invention: the voltage detection module includes a second voltage regulator, a fourth resistor, a fourth capacitor, a fifth resistor, a sixth resistor, a fourth MOS transistor, a fifth MOS transistor, a third amplifier, and a seventh resistor. The input end of the second voltage regulator is connected to the supply voltage, the ground end of the second voltage regulator is grounded, the output end of the second voltage regulator is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to one end of the fourth capacitor, the S pole of the fourth MOS transistor, the D pole of the fifth MOS transistor, and the inverting end of the third amplifier, the other end of the fourth capacitor is grounded, the non-inverting end of the third amplifier is connected to the second output end of the voltage conversion module, the output end of the third amplifier is connected to the G pole of the fourth MOS transistor, the G pole of the fifth MOS transistor, and one end of the seventh resistor, the other end of the seventh resistor is connected to the second input end of the conversion control module, the D pole of the fourth MOS transistor is connected to one end of the fifth resistor, the other end of the fifth resistor is grounded, the S pole of the fifth MOS transistor is connected to one end of the sixth resistor, and the other end of the sixth resistor is grounded.

[0023] As a further solution of the present invention: the conversion control module includes a single-chip microcomputer, the IO1 port of the single-chip microcomputer outputs a PWM1 signal, the IO2 port of the single-chip microcomputer outputs a PWM2 signal, the IO3 port of the single-chip microcomputer outputs a PWM3 signal, the IO4 port of the single-chip microcomputer receives a signal from a common point A1, and the IO5 port of the single-chip microcomputer receives a signal from a common point A2.

[0024] As a further solution of the present invention: the isolated PWM voltage conversion circuit further includes an abnormality prompt module, which includes:

[0025] The abnormality detection unit is used to detect whether the voltage detection module is working abnormally (the voltage at the common point A4 changes frequently). If it is working abnormally, the alarm prompt unit is driven to work;

[0026] Alarm prompt unit, used for alarm prompt during work;

[0027] The input end of the abnormality detection unit is connected to the second output end of the voltage detection module, and the output end of the abnormality detection unit is connected to the input end of the alarm prompt unit.

[0028] As a further solution of the present invention: the abnormality detection unit includes an eighth resistor, a third diode, a fifth capacitor, a ninth resistor, a sixth transistor, a sixth capacitor, a fourth diode, and a fifth diode, one end of the eighth resistor is connected to the second output end of the voltage detection module, the other end of the eighth resistor is connected to the positive electrode of the third diode, one end of the fifth capacitor, and the input end of the alarm prompt unit, the other end of the fifth capacitor is grounded, the negative electrode of the third diode is grounded, one end of the ninth resistor is connected to the power supply voltage, the other end of the ninth resistor is connected to the collector of the sixth transistor, the emitter of the sixth transistor is connected to one end of the sixth capacitor and the negative electrode of the fourth diode, the other end of the sixth capacitor is grounded, the positive electrode of the fourth diode is connected to the positive electrode of the fifth diode and the input end of the alarm prompt unit, the negative electrode of the fifth diode is grounded, the third diode and the fifth diode are light-emitting diodes, the sixth transistor is a photosensitive transistor, and the base of the sixth transistor is only controlled by the light of the third diode.

[0029] As a further solution of the present invention: the alarm prompt unit includes an XOR gate, a tenth resistor, a buzzer, and a sixth diode, one input end of the XOR gate is connected to the anode of the third diode, the other input end of the XOR gate is connected to the anode of the fifth diode, the output end of the XOR gate is connected to one end of the tenth resistor, the other end of the tenth resistor is connected to one end of the buzzer, the other end of the buzzer is connected to the anode of the sixth diode, and the negative pole of the sixth diode is grounded.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention sets a voltage detection module to detect the voltage of solar power generation, and feeds back to the conversion control module, thereby controlling the voltage conversion module to supply power through the LLC circuit or the flyback circuit; it ensures that when the light is strong, the flyback circuit works and can achieve wide voltage input; when the light is dim, the LLC circuit works, efficient soft switching, reduces losses, and ensures that sufficient power is still output to maintain the load operation when the light is dim; the set voltage detection module needs to reach the upper limit threshold when triggering the output of high level, and needs to be lower than the lower limit threshold when stopping the output of high level, thereby avoiding frequent switching of LLC circuit and flyback circuit and increasing the service life of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of an isolated PWM voltage conversion circuit.

[0032] Figure 2 This is the schematic diagram of the voltage conversion module.

[0033] Figure 3 This is the schematic diagram of the abnormal prompt module.

[0034] Figure 4 This is the circuit diagram of the voltage conversion module.

[0035] Figure 5 This is the circuit diagram of the voltage detection module.

[0036] Figure 6 Schematic diagram of the conversion control module.

[0037] Figure 7 This is the circuit diagram of the abnormal prompt module. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] See also Figure 1 , an isolated PWM voltage conversion circuit, comprising:

[0040] Voltage conversion module 1, used to convert the solar-generated electricity into stable DC power after passing it through an LLC circuit or a flyback circuit to supply the load;

[0041] The voltage detection module 2 is used to determine whether the voltage of the solar power generation has reached an upper threshold value, and output a control signal to the conversion control module 3 when the voltage reaches the upper threshold value. When the voltage of the solar power generation is lower than the lower threshold value, the control signal is stopped from being output to the conversion control module 3;

[0042] The conversion control module 3 is used to control the flyback circuit of the voltage conversion module 1 to operate when a control signal is received, and to control the LLC circuit of the voltage conversion module 1 to operate when no control signal is received;

[0043] The first output end of the voltage conversion module 1 is connected to the first input end (common point A1) of the conversion control module 3, the second output end of the voltage conversion module 1 is connected to the input end (common point A3) of the voltage detection module 2, the first output end of the voltage detection module 2 is connected to the second input end (common point A2) of the conversion control module 3, and the output end of the conversion control module 3 is connected to the input ends (PWM1, PWM2, PWM3) of the voltage conversion module 1.

[0044] In this example: See Figure 2 , the voltage conversion module 1 includes:

[0045] The two-in-one output unit 11 is used to output the electric energy generated by solar power generation to the rectification and filtering unit 13 after passing through the LLC circuit or the flyback circuit;

[0046] The voltage detection unit 12 is used to detect the voltage generated by solar power generation and output it to the voltage detection module 2;

[0047] The rectifier and filter unit 13 is used to convert the input unstable current into stable direct current to supply the load;

[0048] The voltage feedback unit 14 is used to sample the voltage output to the load and feed it back to the conversion control module 3;

[0049] The first output end of the two-in-one output unit 11 is connected to the input end of the voltage detection unit 12, the output end of the voltage detection unit 12 is connected to the input end of the voltage detection module 2 (common point A3), the second output end of the two-in-one output unit 11 is connected to the input end of the rectification and filtering unit 13, the output end of the rectification and filtering unit 13 is connected to the input end of the voltage feedback unit 14, and the output end of the voltage feedback unit 14 is connected to the first input end (common point A1) of the conversion control module 3.

[0050] In this example: See Figure 4The two-in-one output unit 11 includes a solar cell E1, a first MOS transistor V1, a second MOS transistor V2, a third MOS transistor V3, a first inductor L1, a second inductor L2, a first capacitor C1, and a transformer W. The negative electrode of the solar cell E1 is grounded, the positive electrode of the solar cell E1 is connected to the D electrode of the second MOS transistor V2 and the input end of the voltage detection unit 12, the S electrode of the second MOS transistor V2 is connected to the D electrode of the third MOS transistor V3 and one end of the first inductor L1, the S electrode of the third MOS transistor V3 is grounded, and the other end of the first inductor L1 is connected to the second inductor L 2 and one end of the input end of the transformer W. The other end of the input end of the transformer W is connected to the other end of the second inductor L2, one end of the first capacitor C1, and the D pole of the first MOS transistor V1. The S pole of the first MOS transistor V1 is grounded. The other end of the first capacitor C1 is grounded. The G pole of the first MOS transistor V1 is connected to the output end of the conversion control module 3. The G pole of the second MOS transistor V2 is connected to the output end of the conversion control module 3. The G pole of the third MOS transistor V3 is connected to the output end of the conversion control module 3. The output end of the transformer W is connected to the input end of the rectifier and filter unit 13.

[0051] When the PWM1 signal (a square wave signal) and the PWM2 signal (which can be a fixed voltage signal) are input, the circuit functions as a flyback circuit. The first and second MOS transistors V1 and V2 are turned on, and the solar cell E1, the second MOS transistor V2, the first inductor L1, the transformer W, and the first MOS transistor V1 form a loop. By controlling the conduction frequency of the first MOS transistor V1, electrical energy at the input of the transformer W is transmitted to the output of the transformer W and supplied to the rectifier and filter unit 13. The flyback circuit allows for a wide input voltage range, so there is no need to worry about the high output voltage of the solar cell E1 damaging the circuit when exposed to strong sunlight.

[0052] When the PWM2 and PWM3 signals are input, the PWM2 and PWM3 signals serve as complementary square wave signals, and the circuit functions as an LLC circuit. The second MOS transistor V2 and the third MOS transistor V3 alternately conduct, forming a square wave signal at the S-pole of the second MOS transistor V2. The square wave signal's harmonics are eliminated by the first inductor L1, the second inductor L2, and the first capacitor C1, and a fundamental frequency sine wave is output for supply to the rectifier and filter unit 13. The LLC circuit achieves efficient soft switching, reduces losses, and can provide more power to the load when the light is dim, compared to a flyback circuit.

[0053] In another embodiment, a plurality of solar cells E1 may be provided.

[0054] In this example: See Figure 4The voltage detection unit 12 includes a first resistor R1 and a first potentiometer RP1. One end of the first resistor R1 is connected to the first output end of the two-in-one output unit 11. The other end of the first resistor R1 is connected to one end of the first potentiometer RP1 and the input end of the voltage detection module 2. The other end of the first potentiometer RP1 is grounded.

[0055] The sum of the voltages across the first resistor R1 and the first potentiometer RP1 is the output voltage of the solar cell E1 . The voltage across the first potentiometer RP1 reflects the output voltage of the solar cell E1 and is fed back to the voltage detection module 2 .

[0056] In another embodiment, the first resistor R1 can be replaced with a Zener diode, and the voltage on the first potentiometer RP1 is the output voltage of the solar cell E1 minus the rated voltage of the Zener diode, which can also reflect the output voltage of the solar cell E1.

[0057] In this example: See Figure 4 The rectifier and filter unit 13 includes a first diode D1, a second diode D2, a second capacitor C2, and a second resistor R2. The positive electrode of the first diode D1 is connected to the first end of the output end of the transformer W, the positive electrode of the second diode D2 is connected to the second end of the output end of the transformer W, one end of the second capacitor C2 is connected to one end of the second resistor R2 and the third end of the output end of the transformer W, and the negative electrode of the first diode D1 is connected to the negative electrode of the second diode D2, the other end of the second capacitor C2, the other end of the second resistor R2, and the input end of the voltage feedback unit 14.

[0058] In the flyback circuit, the output current through the output end of the transformer W is in the form of pulses, with high-frequency components and large ripples, so it needs to be rectified and filtered to become a smooth DC power to supply the load;

[0059] In the LLC circuit, the output current through the output end of the transformer W is AC, which needs to be rectified and filtered to become a smooth DC power to supply the load.

[0060] After being rectified by the first diode D1 and the second diode D2 and filtered by the second capacitor C2, a stable direct current VOUT is formed and output to the load.

[0061] In another embodiment, a rectifier may be directly provided to replace the first diode D1 and the second diode D2 for rectification.

[0062] In this example: See Figure 4The voltage feedback unit 14 includes a third resistor R3, a second potentiometer RP2, a third capacitor C3, and a voltmeter V. One end of the third resistor R3 is connected to the output end of the rectifier and filter unit 13, and the other end of the third resistor R3 is connected to one end of the second potentiometer RP2, one end of the third capacitor C3, one end of the voltmeter V, and the first input end of the conversion control module 3. The other end of the second potentiometer RP2 is grounded, the other end of the third capacitor C3 is grounded, and the other end of the voltmeter V is grounded.

[0063] The sum of the voltages across the third resistor R3 and the second potentiometer RP2 is the output voltage VOUT. The voltage across the second potentiometer RP2 is fed back to the conversion control module 3. By adjusting the resistance value of the second potentiometer RP2, the voltage fed back to the conversion control module 3 is changed, so that the duty cycles of the PWM1, PWM2, and PWM3 signals output by the conversion control module 3 are adjusted, thereby changing the output voltage VOUT.

[0064] In another embodiment, the voltmeter V may be omitted. Here, the voltmeter V is provided, and the value of the output voltage VOUT can be determined by reading the value of the voltmeter V.

[0065] In this example: See Figure 5 The voltage detection module 2 includes a second voltage regulator U2, a fourth resistor R4, a fourth capacitor C4, a fifth resistor R5, a sixth resistor R6, a fourth MOS transistor V4, a fifth MOS transistor V5, a third amplifier U3, and a seventh resistor R7. The input end of the second voltage regulator U2 is connected to the power supply voltage VCC, the ground end of the second voltage regulator U2 is grounded, the output end of the second voltage regulator U2 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected to one end of the fourth capacitor C4, the S pole of the fourth MOS transistor V4, the D pole of the fifth MOS transistor V5, and the third amplifier U3. The inverting end of the fourth capacitor C4 is connected to the inverting end of the fourth MOS tube V4, the other end of the fourth capacitor C4 is grounded, the non-inverting end of the third amplifier U3 is connected to the second output end of the voltage conversion module 1, the output end of the third amplifier U3 is connected to the G pole of the fourth MOS tube V4, the G pole of the fifth MOS tube V5, and one end of the seventh resistor R7, the other end of the seventh resistor R7 is connected to the second input end of the conversion control module 3, the D pole of the fourth MOS tube V4 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is grounded, the S pole of the fifth MOS tube V5 is connected to one end of the sixth resistor R6, and the other end of the sixth resistor R6 is grounded.

[0066] The second voltage regulator U2 outputs a fixed voltage. Initially, the fourth MOS tube V4 is turned on and the fifth MOS tube V5 is turned off. The fourth resistor R4 is connected in series through the third MOS tube V3 and the fifth resistor R5. At this time, the voltage at the inverting terminal of the third amplifier U3 is the upper threshold, and the voltage at the non-inverting terminal of the third amplifier U3 is fixed (common point A3, reflecting the output voltage of the solar cell E1). As the light intensity increases, the voltage at the non-inverting terminal of the third amplifier U3 is higher than the upper threshold, and the third amplifier U3 outputs a high level, triggering the fourth MOS tube V4 to turn off and the fifth MOS tube V5 to turn on. The common point A2 becomes a high level. At this time, the fourth resistor R4 is connected in series through the fifth MOS tube V5 and the sixth resistor R6. The sixth resistor R6 is smaller than the fifth resistor R5, so that the voltage at the inverting terminal of the third amplifier U3 decreases and becomes the lower threshold. The light intensity that triggers the third amplifier U3 to turn on needs to decrease slightly before the third amplifier U3 is turned off. For example, the third amplifier U3 is turned on at a light intensity of 80,000 lux (lux is the unit of light intensity, which corresponds to the upper threshold) and is turned off only when the light intensity drops to 70,000 lux (which corresponds to the lower threshold). Frequent high-level and low-level switching of the common point A2 is avoided, and frequent switching of the flyback circuit and the LLC circuit controlled by the conversion control module 3 is avoided, thereby increasing the service life of the circuit.

[0067] In another embodiment, the supply voltage VCC can be obtained by the output voltage of the solar cell E1.

[0068] In this example: See Figure 6 The conversion control module 3 includes a single-chip microcomputer U1, the IO1 port of the single-chip microcomputer U1 outputs a PWM1 signal, the IO2 port of the single-chip microcomputer U1 outputs a PWM2 signal, the IO3 port of the single-chip microcomputer U1 outputs a PWM3 signal, the IO4 port of the single-chip microcomputer U1 receives a signal from a common point A1, and the IO5 port of the single-chip microcomputer U1 receives a signal from a common point A2.

[0069] The single-chip microcomputer U1 adjusts the output square wave duty cycle of the PWM1, PWM2, and PWM3 signals according to the voltage received at the common point A1. When the common point A2 is at a high level, the single-chip microcomputer U1 determines that the light intensity is high and the output voltage of the solar cell E1 is high, requiring a flyback circuit with a wide voltage input range. When the common point A2 is at a low level, the single-chip microcomputer U1 determines that the light intensity is low and requiring an LLC circuit with lower loss.

[0070] In another embodiment, the single chip microcomputer U1 can be replaced by other chips or circuits capable of adjusting the output square wave signal.

[0071] In this example: See Figure 1 and 3The isolated PWM voltage conversion circuit further includes an abnormality prompt module 4, which includes:

[0072] The abnormality detection unit 41 is used to detect whether the voltage detection module 2 is working abnormally (the voltage at the common point A4 changes frequently). If the working is abnormal, the alarm prompt unit 42 is driven to work;

[0073] An alarm prompt unit 42 is used for alarm prompting during operation;

[0074] An input end of the abnormality detection unit 41 is connected to the second output end of the voltage detection module 2 , and an output end of the abnormality detection unit 41 is connected to an input end of the alarm prompt unit 42 .

[0075] In this example: See Figure 7 The abnormality detection unit 41 includes an eighth resistor R8, a third diode D3, a fifth capacitor C5, a ninth resistor R9, a sixth transistor V6, a sixth capacitor C6, a fourth diode D4, and a fifth diode D5. One end of the eighth resistor R8 is connected to the second output end of the voltage detection module 2, the other end of the eighth resistor R8 is connected to the positive electrode of the third diode D3, one end of the fifth capacitor C5, and the input end of the alarm prompt unit 42, the other end of the fifth capacitor C5 is grounded, the cathode of the third diode D3 is grounded, and one end of the ninth resistor R9 is connected to the power supply voltage V CC, the other end of the ninth resistor R9 is connected to the collector of the sixth transistor V6, the emitter of the sixth transistor V6 is connected to one end of the sixth capacitor C6 and the cathode of the fourth diode D4, the other end of the sixth capacitor C6 is grounded, the anode of the fourth diode D4 is connected to the anode of the fifth diode D5 and the input end of the alarm prompt unit 42, the cathode of the fifth diode D5 is grounded, the third diode D3 and the fifth diode D5 are light-emitting diodes, the sixth transistor V6 is a photosensitive transistor, and the base of the sixth transistor V6 is only controlled by the light of the third diode D3.

[0076] Based on the configuration of the fourth MOS transistor V4 and the fifth MOS transistor V5, the voltage at the inverting terminal of the third amplifier U3 switches back and forth between the upper threshold and the lower threshold, thereby avoiding frequent switching of the voltage at the common point A2 (if only one threshold is set, the third amplifier U3 would be turned on and off multiple times when the light intensity fluctuates above and below the corresponding voltage threshold). Initially, the distance between the third diode D3 and the sixth triode V6 is adjusted so that only when the third amplifier U3 is continuously turned on does the voltage after the third diode D3 emits light and triggers the sixth triode V6 to turn on, which is sufficient to turn on the fourth diode D4 and trigger the fifth diode D5 to turn on.

[0077] If the voltage detection module 2 fails, the third amplifier U3 will be turned on and off multiple times. At this time, the voltage of the common point A4 after passing through the eighth resistor R8 and the fifth capacitor C5 is smaller than the voltage of the common point A4 when the third amplifier U3 is normally turned on. The voltage on the third diode D3 is smaller, the luminous intensity of the third diode D3 is reduced, and the voltage after passing through the sixth transistor V6 is insufficient to turn on the fourth diode D4, so the fifth diode D5 does not emit light.

[0078] In another embodiment, the third diode D3 and the sixth transistor V6 may be replaced by an optocoupler.

[0079] In this example: See Figure 7 The alarm prompt unit 42 includes an XOR gate U4, a tenth resistor R10, a buzzer BUZZ, and a sixth diode D6. One input end of the XOR gate U4 is connected to the anode of the third diode D3, the other input end of the XOR gate U4 is connected to the anode of the fifth diode D5, the output end of the XOR gate U4 is connected to one end of the tenth resistor R10, the other end of the tenth resistor R10 is connected to one end of the buzzer BUZZ, the other end of the buzzer BUZZ is connected to the anode of the sixth diode D6, and the cathode of the sixth diode D6 is grounded.

[0080] The third amplifier U3 is working normally. When the third amplifier U3 is turned on, the third diode D3 and the fifth diode D5 emit light, the two input terminals of the XOR gate U4 are both high, and the XOR gate U4 outputs a low level. When the third amplifier U3 is turned off, there is no voltage at the common point A4, the third diode D3 and the fifth diode D5 do not emit light, the two input terminals of the XOR gate U4 are both low, and the XOR gate U4 outputs a low level.

[0081] The third amplifier U3 works abnormally, causing it to switch on and off multiple times. At this time, the third diode D3 is illuminated and the fifth diode D5 is not illuminated. The input end of the XOR gate U4 has one high level and one low level. The XOR gate U4 outputs a high level, triggering the buzzer BUZZ alarm prompt and the sixth diode D6 lights up for indication.

[0082] In another embodiment, other logic gate combinations may be used to replace the XOR gate U4.

[0083] The working principle of the present invention is as follows: the voltage conversion module 1 is used to output stable direct current after the electric energy generated by solar power generation passes through the LLC circuit or the flyback circuit to supply the load; the voltage detection module 2 is used to determine whether the voltage of the solar power generation reaches the upper limit threshold, and when the upper limit threshold is reached, the control signal is output to the conversion control module 3, and when the voltage of the solar power generation is lower than the lower limit threshold, the control signal is stopped from being output to the conversion control module 3; the conversion control module 3 is used to control the flyback circuit of the voltage conversion module 1 to work when receiving the control signal, and control the LLC circuit of the voltage conversion module 1 to work when no control signal is received.

[0084] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive.

[0085] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An isolated PWM voltage conversion circuit, characterized in that: The isolated PWM voltage conversion circuit includes: The voltage conversion module is used to convert the solar-generated electricity into stable DC power after passing through the LLC circuit or flyback circuit to supply the load. The voltage detection module is used to determine whether the voltage of the solar power generation has reached an upper threshold value, and output a control signal to the conversion control module when the upper threshold value is reached, and stop outputting the control signal to the conversion control module when the voltage of the solar power generation is lower than the lower threshold value; A conversion control module, configured to control the flyback circuit of the voltage conversion module to operate when a control signal is received, and to control the LLC circuit of the voltage conversion module to operate when no control signal is received; The first output end of the voltage conversion module is connected to the first input end of the conversion control module, the second output end of the voltage conversion module is connected to the input end of the voltage detection module, the first output end of the voltage detection module is connected to the second input end of the conversion control module, and the output end of the conversion control module is connected to the input end of the voltage conversion module.

2. The isolated PWM voltage conversion circuit according to claim 1, characterized in that: The voltage conversion module includes: The two-in-one output unit is used to output the electric energy generated by solar power generation to the rectification and filtering unit after passing through the LLC circuit or the flyback circuit; The voltage detection unit is used to detect the voltage generated by solar power generation and output it to the voltage detection module; The rectifier and filter unit is used to convert the input unstable current into stable direct current to supply the load; The voltage feedback unit is used to sample the voltage output to the load and feed it back to the conversion control module; The first output end of the two-in-one output unit is connected to the input end of the voltage detection unit, the output end of the voltage detection unit is connected to the input end of the voltage detection module, the second output end of the two-in-one output unit is connected to the input end of the rectifier and filter unit, the output end of the rectifier and filter unit is connected to the input end of the voltage feedback unit, and the output end of the voltage feedback unit is connected to the first input end of the conversion control module.

3. The isolated PWM voltage conversion circuit according to claim 2, characterized in that: The two-in-one output unit includes a solar cell, a first MOS transistor, a second MOS transistor, a third MOS transistor, a first inductor, a second inductor, a first capacitor, and a transformer. The negative electrode of the solar cell is grounded, the positive electrode of the solar cell is connected to the D electrode of the second MOS transistor and the input end of the voltage detection unit, the S electrode of the second MOS transistor is connected to the D electrode of the third MOS transistor and one end of the first inductor, the S electrode of the third MOS transistor is grounded, the other end of the first inductor is connected to one end of the second inductor and one end of the input end of the transformer, the other end of the input end of the transformer is connected to the other end of the second inductor, one end of the first capacitor, and the D electrode of the first MOS transistor, the S electrode of the first MOS transistor is grounded, the other end of the first capacitor is grounded, the G electrode of the first MOS transistor is connected to the output end of the conversion control module, the G electrode of the second MOS transistor is connected to the output end of the conversion control module, the G electrode of the third MOS transistor is connected to the output end of the conversion control module, and the output end of the transformer is connected to the input end of the rectifier and filter unit.

4. The isolated PWM voltage conversion circuit according to claim 2, characterized in that: The voltage detection unit includes a first resistor and a first potentiometer. One end of the first resistor is connected to the first output end of the two-in-one output unit, the other end of the first resistor is connected to one end of the first potentiometer and the input end of the voltage detection module, and the other end of the first potentiometer is grounded.

5. The isolated PWM voltage conversion circuit according to claim 3, characterized in that: The rectifier and filter unit includes a first diode, a second diode, a second capacitor, and a second resistor. The positive electrode of the first diode is connected to the first end of the output end of the transformer, the positive electrode of the second diode is connected to the second end of the output end of the transformer, one end of the second capacitor is connected to one end of the second resistor and the third end of the output end of the transformer, and the negative electrode of the first diode is connected to the negative electrode of the second diode, the other end of the second capacitor, the other end of the second resistor, and the input end of the voltage feedback unit.

6. The isolated PWM voltage conversion circuit according to claim 2, characterized in that: The voltage feedback unit includes a third resistor, a second potentiometer, a third capacitor, and a voltmeter. One end of the third resistor is connected to the output end of the rectifier and filter unit, the other end of the third resistor is connected to one end of the second potentiometer, one end of the third capacitor, one end of the voltmeter, and the first input end of the conversion control module, the other end of the second potentiometer is grounded, the other end of the third capacitor is grounded, and the other end of the voltmeter is grounded.

7. The isolated PWM voltage conversion circuit according to any one of claims 1 to 6, characterized in that: The voltage detection module includes a second voltage regulator, a fourth resistor, a fourth capacitor, a fifth resistor, a sixth resistor, a fourth MOS transistor, a fifth MOS transistor, a third amplifier, and a seventh resistor. The input end of the second voltage regulator is connected to the supply voltage, the ground end of the second voltage regulator is grounded, the output end of the second voltage regulator is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to one end of the fourth capacitor, the S pole of the fourth MOS transistor, the D pole of the fifth MOS transistor, and the inverting end of the third amplifier, the other end of the fourth capacitor is grounded, the non-inverting end of the third amplifier is connected to the second output end of the voltage conversion module, the output end of the third amplifier is connected to the G pole of the fourth MOS transistor, the G pole of the fifth MOS transistor, and one end of the seventh resistor, the other end of the seventh resistor is connected to the second input end of the conversion control module, the D pole of the fourth MOS transistor is connected to one end of the fifth resistor, the other end of the fifth resistor is grounded, the S pole of the fifth MOS transistor is connected to one end of the sixth resistor, and the other end of the sixth resistor is grounded.

8. The isolated PWM voltage conversion circuit according to claim 1, characterized in that: The isolated PWM voltage conversion circuit further includes an abnormality prompt module, which includes: The abnormality detection unit is used to detect whether the voltage detection module is working abnormally. If it is working abnormally, the alarm prompt unit is driven to work; Alarm prompt unit, used for alarm prompt during work; The input end of the abnormality detection unit is connected to the second output end of the voltage detection module, and the output end of the abnormality detection unit is connected to the input end of the alarm prompt unit.

9. The isolated PWM voltage conversion circuit according to claim 8, characterized in that: The abnormality detection unit includes an eighth resistor, a third diode, a fifth capacitor, a ninth resistor, a sixth transistor, a sixth capacitor, a fourth diode, and a fifth diode. One end of the eighth resistor is connected to the second output end of the voltage detection module, the other end of the eighth resistor is connected to the positive electrode of the third diode, one end of the fifth capacitor, and the input end of the alarm prompt unit, the other end of the fifth capacitor is grounded, the negative electrode of the third diode is grounded, one end of the ninth resistor is connected to the power supply voltage, the other end of the ninth resistor is connected to the collector of the sixth transistor, the emitter of the sixth transistor is connected to one end of the sixth capacitor and the negative electrode of the fourth diode, the other end of the sixth capacitor is grounded, the positive electrode of the fourth diode is connected to the positive electrode of the fifth diode and the input end of the alarm prompt unit, the negative electrode of the fifth diode is grounded, the third diode and the fifth diode are light-emitting diodes, the sixth transistor is a photosensitive transistor, and the base of the sixth transistor is only controlled by the light of the third diode.

10. The isolated PWM voltage conversion circuit according to claim 9, characterized in that: The alarm prompt unit includes an XOR gate, a tenth resistor, a buzzer, and a sixth diode. One input end of the XOR gate is connected to the anode of the third diode, the other input end of the XOR gate is connected to the anode of the fifth diode, the output end of the XOR gate is connected to one end of the tenth resistor, the other end of the tenth resistor is connected to one end of the buzzer, the other end of the buzzer is connected to the anode of the sixth diode, and the negative pole of the sixth diode is grounded.

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