Isolation PWM voltage conversion circuit

Abstract

The invention discloses an isolation PWM voltage conversion circuit, and relates to the field of voltage conversion, and the isolation PWM voltage conversion circuit comprises a voltage conversion module which is used for enabling electric energy generated by solar power generation to pass through an LLC circuit or a flyback circuit, then outputting stable direct current, and supplying the direct current to a load; compared with the prior art, the invention has the following beneficial effects: the voltage conversion module supplies power through the LLC circuit or the flyback circuit; when strong illumination is ensured, the flyback circuit works, and wide voltage input can be realized; when illumination is dim, the LLC circuit works, efficient soft switching is achieved, loss is reduced, and it is guaranteed that enough electric energy is still output to maintain the load to work when illumination is dim. The voltage detection module is triggered only when a high level is triggered and output and is triggered only when the voltage detection module is lower than a lower threshold value when the high level is stopped being output, so that frequent switching of the LLC circuit and the flyback circuit is avoided, and the service life of the circuit is prolonged.

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: An isolated PWM voltage conversion circuit, comprising: 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 (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.

[0007] As a further solution of the present invention: the voltage conversion module includes: A two-in-one output unit for outputting the electric energy generated by solar power generation to a rectifying and filtering unit after passing through an LLC circuit or a flyback circuit; A voltage detection unit for detecting the magnitude of the voltage generated by solar power generation and outputting it to a voltage detection module; A rectifying and filtering unit for converting the input unsteady current into a steady direct current to supply the load; A voltage feedback unit for sampling the magnitude of the voltage output to the load and feeding it back to a 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 (common point A3), the second output end of the two-in-one output unit is connected to the input end of the rectifying and filtering unit, the output end of the rectifying 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).

[0008] 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, and the positive electrode of the solar cell is connected to the D pole of the second MOS transistor and the input end of the voltage detection unit. The S pole of the second MOS transistor is connected to the D pole of the third MOS transistor and one end of the first inductor. The S pole 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 of the transformer. The other end of the input of the transformer is connected to the other end of the second inductor, one end of the first capacitor, and the D pole of the first MOS transistor. The S pole of the first MOS transistor is grounded. The other end of the first capacitor is grounded. The G pole of the first MOS transistor is connected to the output end of the conversion control module. The G pole of the second MOS transistor is connected to the output end of the conversion control module. The G pole of the third MOS transistor is connected to the output end of the conversion control module. The output end of the transformer is connected to the input end of the rectifying and filtering unit.

[0009] 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.

[0010] As a further aspect of the present invention: The rectifying and filtering 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 terminal of the transformer. The positive electrode of the second diode is connected to the second end of the output terminal 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 terminal of the transformer. 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 terminal of the voltage feedback unit.

[0011] As a further aspect 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 terminal of the rectifying and filtering 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 terminal of the conversion control module. The other end of the second potentiometer is grounded. The other end of the third capacitor is grounded. The other end of the voltmeter is grounded.

[0012] As a further aspect 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 terminal of the second voltage regulator is connected to the supply voltage. The ground terminal of the second voltage regulator is grounded. The output terminal 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 terminal of the third amplifier. The other end of the fourth capacitor is grounded. The non-inverting terminal of the third amplifier is connected to the second output terminal of the voltage conversion module. The output terminal 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 terminal 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. The other end of the sixth resistor is grounded.

[0013] As a further aspect 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 the signal of the common point A1. The IO5 port of the single-chip microcomputer receives the signal of the common point A2.

[0014] As a further aspect of the present invention: The isolated PWM voltage conversion circuit further includes an abnormal prompt module, and the abnormal prompt module includes: An abnormal detection unit for detecting whether the voltage detection module is operating abnormally (the voltage at the common point A4 changes frequently). When operating abnormally, it drives the alarm prompt unit to work; An alarm prompt unit for giving an alarm prompt during operation; The input end of the anomaly detection unit is connected to the second output end of the voltage detection module, and the output end of the anomaly detection unit is connected to the input end of the alarm and prompt unit.

[0015] As a further solution of the present invention: The anomaly detection unit includes an eighth resistor, a third diode, a fifth capacitor, a ninth resistor, a sixth triode, 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, and 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 and prompt unit. The other end of the fifth capacitor is grounded, and the negative electrode of the third diode is grounded. One end of the ninth resistor is connected to the supply voltage, and the other end of the ninth resistor is connected to the collector of the sixth triode. The emitter of the sixth triode 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 and prompt unit. The negative electrode of the fifth diode is grounded. The third diode and the fifth diode are light-emitting diodes, and the sixth triode is a photosensitive triode. The base of the sixth triode is only controlled by the light of the third diode.

[0016] As a further solution of the present invention: The alarm and prompt unit includes an exclusive OR gate, a tenth resistor, a buzzer, and a sixth diode. One input end of the exclusive OR gate is connected to the positive electrode of the third diode, and the other input end of the exclusive OR gate is connected to the positive electrode of the fifth diode. The output end of the exclusive OR 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, and the other end of the buzzer is connected to the positive electrode of the sixth diode. The negative electrode of the sixth diode is grounded.

[0017] 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 feedback it to the conversion control module, and then controls 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 input voltage; when the light is dim, the LLC circuit works, with high-efficiency soft switching and reduced losses, ensuring that sufficient electric energy is still output to maintain the operation of the load when the light is dim; the set voltage detection module triggers when reaching the upper limit threshold when triggering the output of a high level, and triggers when being lower than the lower limit threshold when stopping the output of a high level, avoiding frequent switching of the LLC circuit and the flyback circuit and increasing the service life of the circuit. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of an isolated PWM voltage conversion circuit.

[0019] Figure 2 It is a schematic diagram of the voltage conversion module.

[0020] Figure 3 It is a schematic diagram of the anomaly prompt module.

[0021] Figure 4 It is a circuit diagram of a voltage conversion module.

[0022] Figure 5 It is a circuit diagram of a voltage detection module.

[0023] Figure 6 It is a schematic diagram of a conversion control module.

[0024] Figure 7 It is a circuit diagram of an abnormal prompt module. Specific implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Please refer to Figure 1 , an isolated PWM voltage conversion circuit, including: A voltage conversion module 1, configured to output stable direct current after passing the electric energy generated by solar power generation through an LLC circuit or a flyback circuit, and supply it to a load; A voltage detection module 2, configured to determine whether the voltage of solar power generation reaches an upper threshold value, and output a control signal to the conversion control module 3 when reaching the upper threshold value, and stop outputting the control signal to the conversion control module 3 when the voltage of solar power generation is lower than the lower threshold value; A conversion control module 3, configured to control the flyback circuit of the voltage conversion module 1 to work when receiving a control signal, and control the LLC circuit of the voltage conversion module 1 to work when not receiving a control signal; 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 end (PWM1, PWM2, PWM3) of the voltage conversion module 1.

[0027] In this embodiment: Please refer to Figure 2 , the voltage conversion module 1 includes: A two-in-one output unit 11, configured to output the electric energy generated by solar power generation to a rectification and filtering unit 13 after passing through an LLC circuit or a flyback circuit; The voltage detection unit 12 is used to detect the magnitude of the voltage generated by solar power generation and output it to the voltage detection module 2; The rectification and filtering unit 13 is used to convert the input unsteady current into steady direct current and supply it to the load; The voltage feedback unit 14 is used to sample the magnitude of the voltage output to the load and feedback it to the conversion control module 3; The first output terminal of the two-in-one output unit 11 is connected to the input terminal of the voltage detection unit 12, the output terminal of the voltage detection unit 12 is connected to the input terminal of the voltage detection module 2 (common point A3), the second output terminal of the two-in-one output unit 11 is connected to the input terminal of the rectification and filtering unit 13, the output terminal of the rectification and filtering unit 13 is connected to the input terminal of the voltage feedback unit 14, and the output terminal of the voltage feedback unit 14 is connected to the first input terminal of the conversion control module 3 (common point A1).

[0028] In this embodiment: Please refer to Figure 4 , the 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 pole of the second MOS transistor V2 and the input terminal of the voltage detection unit 12. The S pole of the second MOS transistor V2 is connected to the D pole of the third MOS transistor V3 and one end of the first inductor L1. The S pole of the third MOS transistor V3 is grounded. The other end of the first inductor L1 is connected to one end of the second inductor L2 and one end of the input terminal of the transformer W. The other end of the input terminal 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 terminal of the conversion control module 3. The G pole of the second MOS transistor V2 is connected to the output terminal of the conversion control module 3. The G pole of the third MOS transistor V3 is connected to the output terminal of the conversion control module 3. The output terminal of the transformer W is connected to the input terminal of the rectification and filtering unit 13.

[0029] When the PWM1 signal (square wave signal) and the PWM2 signal (which can be a fixed voltage signal at this time) are input, the circuit acts as a flyback circuit. The first MOS transistor V1 and the second MOS transistor V2 are turned on. 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, the electric energy at the input terminal of the transformer W is transmitted to the output terminal of the transformer W and supplied to the rectification and filtering unit 13. The flyback circuit allows a wide input voltage range and does not worry about damaging the circuit due to the large voltage output by the solar cell E1 when the light is strong.

[0030] When the PWM2 signal and the PWM3 signal are input, at this time, the PWM2 and PWM3 signals are complementary square wave signals, the circuit is an LLC circuit, the second MOS transistor V2 and the third MOS transistor V3 conduct alternately, so that a square wave signal is formed at the S pole of the second MOS transistor V2. After passing through the first inductor L1, the second inductor L2, and the first capacitor C1, the harmonics of the square wave signal are eliminated and a sine wave of the fundamental frequency is output, which is supplied to the rectification and filtering unit 13. The LLC circuit can achieve efficient soft switching, reduce losses, and supply more power to the load than the flyback circuit when the light is dim.

[0031] In another embodiment: Multiple solar cells E1 can be provided.

[0032] In this embodiment: Please refer to Figure 4 , the 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, and 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, and the other end of the first potentiometer RP1 is grounded.

[0033] The sum of the voltages on the first resistor R1 and the first potentiometer RP1 is the output voltage of the solar cell E1, and the voltage on the first potentiometer RP1 reflects the magnitude of the output voltage of the solar cell E1 and is fed back to the voltage detection module 2.

[0034] In another embodiment: The first resistor R1 can be replaced with a zener diode. 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 magnitude of the output voltage of the solar cell E1.

[0035] In this embodiment: Please refer to Figure 4 , the rectification and filtering 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.

[0036] In the flyback circuit, the current output through the output end of the transformer W is in the form of a pulse, with high-frequency components and large ripples. Therefore, it needs to be rectified and filtered into a stable direct current to supply the load; In the LLC circuit, the current output through the output end of the transformer W is an alternating current, which needs to be rectified and filtered into a stable direct current to supply the load.

[0037] 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.

[0038] In another embodiment: A rectifier can be directly set to replace the first diode D1 and the second diode D2 for rectification.

[0039] In this embodiment: Please refer to Figure 4 , the 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 rectification and filtering 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.

[0040] The sum of the voltages on the third resistor R3 and the second potentiometer RP2 is the output voltage VOUT. The voltage on the second potentiometer RP2 is fed back to the conversion control module 3. By adjusting the resistance value on the second potentiometer RP2, the magnitude of 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, and the magnitude of the output voltage VOUT is changed.

[0041] In another embodiment: The voltmeter V can be omitted. Here, the voltmeter V is provided to facilitate determining the magnitude of the output voltage VOUT by reading the value of the voltmeter V.

[0042] In this embodiment: Please refer to 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 terminal of the second voltage regulator U2 is connected to the supply voltage VCC, the ground terminal of the second voltage regulator U2 is grounded, the output terminal 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 inverting terminal of the third amplifier U3. The other end of the fourth capacitor C4 is grounded. The non-inverting terminal of the third amplifier U3 is connected to the second output terminal of the voltage conversion module 1. The output terminal of the third amplifier U3 is connected to the G pole of the fourth MOS transistor V4, the G pole of the fifth MOS transistor V5, and one end of the seventh resistor R7. The other end of the seventh resistor R7 is connected to the second input terminal of the conversion control module 3. The D pole of the fourth MOS transistor V4 is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is grounded. The S pole of the fifth MOS transistor V5 is connected to one end of the sixth resistor R6, and the other end of the sixth resistor R6 is grounded.

[0043] The second voltage regulator U2 outputs a fixed voltage. Initially, the fourth MOS transistor V4 is conducting and the fifth MOS transistor V5 is cut off. The fourth resistor R4 is connected in series with the third MOS transistor V3 and the fifth resistor R5. At this time, the voltage at the inverting terminal of the third amplifier U3 is the upper threshold value, and the voltage at the non-inverting terminal of the third amplifier U3 is fixed (the common point A3, which reflects 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 value. The third amplifier U3 outputs a high level, triggering the fourth MOS transistor V4 to cut off and the fifth MOS transistor V5 to conduct. The common point A2 becomes high level. At this time, the fourth resistor R4 is connected in series with the fifth MOS transistor V5 and the sixth resistor R6. The sixth resistor R6 is smaller than the fifth resistor R5, making the voltage at the inverting terminal of the third amplifier U3 decrease to the lower threshold value. The light intensity required to trigger the third amplifier U3 to cut off needs to drop by a certain amount after it conducts. For example, the third amplifier U3 conducts at a light intensity of 80,000 lux (lux is the unit of light intensity, and this light intensity corresponds to the upper threshold value), and the third amplifier U3 will cut off when the light intensity drops to 70,000 lux (this light intensity corresponds to the lower threshold value); this avoids frequent switching of the high and low levels of the common point A2 and frequent switching of the conversion control module 3 controlling the flyback circuit and the LLC circuit, increasing the service life of the circuit.

[0044] In another embodiment: the supply voltage VCC can be obtained from the output voltage of the solar cell E1.

[0045] In this embodiment: Please refer to 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 outputs a PWM2 signal, the IO3 port outputs a PWM3 signal, the IO4 port receives the signal of the common point A1, and the IO5 port receives the signal of the common point A2.

[0046] The single-chip microcomputer U1 adjusts the duty cycle of the output square wave 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 at this time, the output voltage of the solar cell E1 is large, and a flyback circuit with a wide voltage input range is required. When the common point A2 is at a low level, the single-chip microcomputer U1 determines that the light intensity is relatively small at this time, and an LLC circuit with less loss is required.

[0047] In another embodiment: The single-chip microcomputer U1 can be replaced by other chips or circuits that can adjust the output square wave signal.

[0048] In this embodiment: Please refer to Figure 1 and 3 , the isolated PWM voltage conversion circuit further includes an abnormal prompt module 4, and the abnormal prompt module 4 includes: An abnormal detection unit 41, which is used to detect whether the voltage detection module 2 is working abnormally (the voltage at the common point A4 changes frequently). When working abnormally, it drives the alarm prompt unit 42 to work; An alarm prompt unit 42, which is used to give an alarm prompt when working; The input end of the abnormal detection unit 41 is connected to the second output end of the voltage detection module 2, and the output end of the abnormal detection unit 41 is connected to the input end of the alarm prompt unit 42.

[0049] In this embodiment: Please refer to Figure 7, the anomaly detection unit 41 includes an eighth resistor R8, a third diode D3, a fifth capacitor C5, a ninth resistor R9, a sixth triode 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 terminal of the voltage detection module 2, and 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 terminal of the alarm and prompt unit 42. The other end of the fifth capacitor C5 is grounded, the negative electrode of the third diode D3 is grounded, one end of the ninth resistor R9 is connected to the supply voltage VCC, and the other end of the ninth resistor R9 is connected to the collector of the sixth triode V6. The emitter of the sixth triode V6 is connected to one end of the sixth capacitor C6 and the negative electrode of the fourth diode D4. The other end of the sixth capacitor C6 is grounded, the positive electrode of the fourth diode D4 is connected to the positive electrode of the fifth diode D5 and the input terminal of the alarm and prompt unit 42, and the negative electrode of the fifth diode D5 is grounded. The third diode D3 and the fifth diode D5 are light-emitting diodes, and the sixth triode V6 is a photosensitive triode. The base of the sixth triode V6 is only controlled by the light of the third diode D3.

[0050] Based on the set fourth MOS transistor V4 and fifth MOS transistor V5, the voltage at the inverting terminal of the third amplifier U3 will switch back and forth between the upper limit threshold and the lower limit threshold, avoiding frequent switching of the voltage at the common point A2 (if only one threshold is set, when the light intensity changes above and below the corresponding voltage threshold, it will cause the third amplifier U3 to conduct and cut off multiple times). At the beginning, the distance between the third diode D3 and the sixth triode V6 is adjusted so that only when the third amplifier U3 is continuously conducting, the voltage after the third diode D3 emits light and triggers the sixth triode V6 to conduct is sufficient to conduct the fourth diode D4 and trigger the fifth diode D5 to conduct; If the voltage detection module 2 fails, there will be multiple on-off switches of the third amplifier U3 at this time. At this time, the voltage at the common point A4 passes through the eighth resistor R8 and the fifth capacitor C5 and is smaller than the voltage at the common point A4 when the third amplifier U3 is normally conducting. The voltage across the third diode D3 is smaller, the light intensity of the third diode D3 decreases, and the voltage after passing through the sixth triode V6 is not sufficient to conduct the fourth diode D4, and the fifth diode D5 does not emit light.

[0051] In another embodiment: The third diode D3 and the sixth triode V6 can be replaced by an optocoupler.

[0052] In this embodiment: Please refer to Figure 7, the alarm prompt unit 42 includes an exclusive-OR gate U4, a tenth resistor R10, a buzzer BUZZ, and a sixth diode D6. One input terminal of the exclusive-OR gate U4 is connected to the positive electrode of the third diode D3, and the other input terminal of the exclusive-OR gate U4 is connected to the positive electrode of the fifth diode D5. The output terminal of the exclusive-OR 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 positive electrode of the sixth diode D6, and the negative electrode of the sixth diode D6 is grounded.

[0053] When the third amplifier U3 works normally and is turned on, the third diode D3 and the fifth diode D5 emit light. Both input terminals of the exclusive-OR gate U4 are at high level, and the exclusive-OR gate U4 outputs a low level. When the third amplifier U3 is cut off, there is no voltage at the common point A4, the third diode D3 and the fifth diode D5 do not emit light, both input terminals of the exclusive-OR gate U4 are at low level, and the exclusive-OR gate U4 outputs a low level. When the third amplifier U3 works abnormally, resulting in multiple on-off switches of the third amplifier U3, at this time, there is a situation where the third diode D3 emits light and the fifth diode D5 does not emit light. One input terminal of the exclusive-OR gate U4 is at high level and the other is at low level. The exclusive-OR gate U4 outputs a high level, triggering the buzzer BUZZ for alarm prompt, and the sixth diode D6 emits light for indication.

[0054] In another embodiment: other combinations of logic gates can be used to replace the exclusive-OR gate U4.

[0055] The working principle of the present invention is as follows: The voltage conversion module 1 is used to convert the electric energy generated by solar power generation into stable direct current after passing through the LLC circuit or the flyback circuit and supply it to the load. The voltage detection module 2 is used to judge whether the voltage of solar power generation reaches the upper limit threshold. When it reaches the upper limit threshold, it outputs a control signal to the conversion control module 3. When the voltage of solar power generation is lower than the lower limit threshold, it stops outputting the control signal 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 not receiving the control signal.

[0056] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting.

[0057] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments 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: A voltage conversion module for outputting stable direct current power after passing the electric energy generated by solar power generation through an LLC circuit or a flyback circuit to supply the load; A voltage detection module for determining whether the voltage of solar power generation reaches the upper threshold value, and outputting a control signal to the conversion control module when the upper threshold value is reached, and stopping outputting the control signal to the conversion control module when the voltage of solar power generation is lower than the lower threshold value; A conversion control module for controlling the operation of the flyback circuit of the voltage conversion module when receiving the control signal, and controlling the operation of the LLC circuit of the voltage conversion module when not receiving the control signal; 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: A two-in-one output unit for outputting the electric energy generated by solar power generation to the rectification and filtering unit after passing through an LLC circuit or a flyback circuit; A voltage detection unit for detecting the magnitude of the voltage generated by solar power generation and outputting it to the voltage detection module; A rectification and filtering unit for converting the input unsteady current into steady direct current power to supply the load; A voltage feedback unit for sampling the magnitude of the voltage output to the load and feeding 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 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.

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 pole of the second MOS transistor and the input end of the voltage detection unit, the S pole of the second MOS transistor is connected to the D pole of the third MOS transistor and one end of the first inductor, the S pole 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 pole of the first MOS transistor, the S pole of the first MOS transistor is grounded, the other end of the first capacitor is grounded, the G pole of the first MOS transistor is connected to the output end of the conversion control module, the G pole of the second MOS transistor is connected to the output end of the conversion control module, the G pole 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 rectification and filtering unit.

4. The isolated PWM voltage conversion circuit according to claim 2, wherein, 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, wherein, The rectifying and filtering 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 terminal of the transformer. The positive electrode of the second diode is connected to the second end of the output terminal 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 terminal of the transformer. 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 terminal 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 terminal of the rectifying and filtering 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 terminal of the conversion control module. The other end of the second potentiometer is grounded. The other end of the third capacitor is grounded. 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 terminal of the second voltage regulator is connected to the supply voltage. The ground terminal of the second voltage regulator is grounded. The output terminal 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 terminal of the third amplifier. The other end of the fourth capacitor is grounded. The non-inverting terminal of the third amplifier is connected to the second output terminal of the voltage conversion module. The output terminal 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 terminal 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. 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 prompting module, and the abnormality prompting module includes: An abnormality detection unit, configured to detect whether the voltage detection module is operating abnormally. When operating abnormally, it drives the alarm prompting unit to operate; An alarm prompting unit, configured to give an alarm prompt during operation; The input terminal of the abnormality detection unit is connected to the second output terminal of the voltage detection module. The output terminal of the abnormality detection unit is connected to the input terminal of the alarm prompting unit.

9. The isolated PWM voltage conversion circuit according to claim 8, wherein, The anomaly detection unit includes an eighth resistor, a third diode, a fifth capacitor, a ninth resistor, a sixth triode, a sixth capacitor, a fourth diode, and a fifth diode. One end of the eighth resistor is connected to the second output terminal of the voltage detection module, and 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 terminal 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 supply voltage, and the other end of the ninth resistor is connected to the collector of the sixth triode. The emitter of the sixth triode 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 terminal of the alarm prompt unit, and the negative electrode of the fifth diode is grounded. The third diode and the fifth diode are light-emitting diodes, and the sixth triode is a photosensitive triode. The base of the sixth triode is controlled only 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 exclusive-OR gate, a tenth resistor, a buzzer, and a sixth diode. One input terminal of the exclusive-OR gate is connected to the positive electrode of the third diode, the other input terminal of the exclusive-OR gate is connected to the positive electrode of the fifth diode, the output terminal of the exclusive-OR 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 positive electrode of the sixth diode, and the negative electrode of the sixth diode is grounded.

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