Auxiliary power supply and photovoltaic inverter

Abstract

The utility model relates to the technical field of photovoltaic power generation, and discloses an auxiliary power supply and a photovoltaic inverter. In the prior art, the short circuit detection of an auxiliary power supply depends on the current change of the primary side of a transformer during short circuit, and then whether protection is started or not is judged through the voltage change of a sampling resistor, which is limited by the resistance value of the sampling resistor, so that the detection of the voltage change is not obvious and the protection is not timely. According to the technical scheme, the detection capability of the control chip is improved by increasing the voltage detected by the control chip by adding the short-circuit protection circuit, the input end of the short-circuit protection circuit is connected with the feedback pin of the control chip, and the short-circuit condition of the auxiliary power supply is judged by detecting the voltage change of the feedback pin. And when the short circuit is detected, the voltage source circuit is turned on to increase the voltage change detected by the detection pin. According to the technical scheme, the detection capability of the control chip is improved by enhancing the voltage detection magnitude of the control chip when the auxiliary power supply is short-circuited, and more timely protection of the auxiliary power supply is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic power generation, in particular to an auxiliary power supply and a photovoltaic inverter. Background Art

[0002] The auxiliary power supply of the photovoltaic inverter is usually composed of a flyback topology structure plus a pulse width modulation (PWM) control chip. The PWM control chip controls the output voltage of the auxiliary power supply back end by adjusting the driving duty cycle through the feedback pin level value. When any load fault occurs in the back end of the auxiliary power supply and a short circuit occurs, the auxiliary power supply will first be treated as an output with a heavy load and continue to output a large current. If it is not protected in time, the primary side of the auxiliary power supply will be damaged by excessive current, causing the field effect tube to be damaged or the current detection resistor to burn out.

[0003] In current technology, the detection and protection of auxiliary power supply short circuit is to raise the voltage value on the sampling resistor through the large current on the primary side of the transformer after the short circuit. The PWM control chip uses the voltage rise value on the sampling resistor to perform wave blocking protection in each cycle. However, due to the wide input range of the auxiliary power supply, the primary side current is large when the input voltage is low, resulting in obvious voltage changes, so protection can be achieved. When the input voltage is high, the primary side current itself is small, so the voltage change value on the sampling resistor is also small, resulting in untimely detection and protection of the PWM control chip.

[0004] It can be seen that how to achieve more timely and accurate short-circuit protection for the auxiliary power supply is an urgent problem to be solved by those skilled in the art. Utility Model Content

[0005] The purpose of the utility model is to provide an auxiliary power supply and a photovoltaic inverter, so as to solve the problem that the short-circuit detection of the auxiliary power supply in the current technology relies on the current change on the primary side of the transformer during the short circuit and then determines whether to start the protection through the voltage change of the sampling resistor, but is limited by the resistance value of the sampling resistor, resulting in unclear detection of the voltage change and thus untimely protection.

[0006] In order to solve the above technical problems, the utility model provides an auxiliary power supply, including a transformer, a control chip, and a sampling resistor, wherein the feedback pin of the control chip is connected to the output main winding of the transformer through a feedback circuit; the detection pin of the control chip is grounded through the sampling resistor, the output pin of the control chip is connected to the input end of the transformer through a field effect transistor, and the source of the field effect transistor is grounded through the sampling resistor; and further includes:

[0007] Short circuit protection circuit;

[0008] The input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the output end is connected to the detection pin of the control chip;

[0009] The short-circuit protection circuit includes a detection circuit and a voltage source circuit;

[0010] The detection circuit is connected to the feedback pin as the input end of the short-circuit protection circuit, and is used to detect the level change of the feedback pin, and cut off or conduct the connection line between the voltage source circuit and the detection pin according to the level change.

[0011] Preferably, the detection circuit comprises: a sampling circuit and a switch component;

[0012] The input end of the sampling circuit is connected to the feedback pin, the output end is connected to the control end of the switch component, the first end of the switch component is connected to the voltage source circuit, and the second end of the switch component is grounded.

[0013] Preferably, the sampling circuit comprises a first resistor and a second resistor;

[0014] The first end of the first resistor is connected to the feedback pin as the input end of the sampling circuit, the second end of the first resistor and the first end of the second resistor are commonly connected to the control end of the switch component, and the second end of the switch component and the second end of the second resistor are grounded.

[0015] Preferably, the voltage source circuit comprises: a third resistor, a fourth resistor, a fifth resistor, a first transistor, and a voltage stabilizing source;

[0016] The first ends of the third resistor and the fourth resistor are commonly connected to the voltage stabilizing source, the second end of the third resistor and the first end of the fifth resistor are connected to the first end of the switch component, the second end of the fourth resistor is connected to the emitter of the first transistor, the second end of the fifth resistor is connected to the base of the first transistor, and the collector of the first transistor is connected to the detection pin.

[0017] Preferably, the switch component is TL431, the cathode of the TL431 serves as the first end of the switch component, the anode of the TL431 serves as the second end of the switch component, and the reference end of the TL431 serves as the control end of the switch component.

[0018] Preferably, the switch component is a second transistor; the base of the second transistor serves as the control end of the switch component, the emitter of the second transistor serves as the second end of the switch component, and the collector of the second transistor serves as the first end of the switch component.

[0019] Preferably, the sampling circuit is a comparator;

[0020] The non-inverting input terminal of the comparator is connected to the feedback pin, the inverting input terminal of the comparator is connected to a reference voltage, and the output terminal of the comparator is connected to the switch component.

[0021] Preferably, it also includes: a capacitor;

[0022] A first end of the capacitor is connected to the second end of the first resistor and the first end of the second resistor, and a second end of the capacitor is grounded.

[0023] Preferably, it further comprises: a sixth resistor;

[0024] The emitter of the second transistor is grounded through the sixth resistor.

[0025] In order to solve the above technical problems, the utility model also provides a photovoltaic inverter, including the above auxiliary power supply.

[0026] The auxiliary power supply provided by the utility model comprises a transformer, a control chip, and a sampling resistor. The feedback pin of the control chip is connected to the output main winding of the transformer through a feedback circuit; the detection pin of the control chip is grounded through a sampling resistor, and the output pin of the control chip is connected to the input end of the transformer through a field effect transistor; and also comprises: a short-circuit protection circuit; the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the output end is connected to the detection pin of the control chip; the short-circuit protection circuit comprises a detection circuit and a voltage source circuit; the detection circuit is connected to the feedback pin as the input end of the short-circuit protection circuit, and is used to detect the level change of the feedback pin, and cut off or conduct the connection line between the voltage source circuit and the detection pin according to the level change. Compared with the current technology that relies on the current change on the primary side of the transformer when the short circuit occurs, and then determines whether to start the protection through the voltage change of the sampling resistor, which is limited by the resistance of the sampling resistor, resulting in unclear detection of the voltage change and untimely protection, the present technical solution is adopted to increase the voltage detected by the control chip by adding a short-circuit protection circuit to improve the detection capability of the control chip. In the present technical solution, the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the short circuit of the auxiliary power supply is determined by detecting the voltage change of the feedback pin, and the voltage source circuit is turned on when the short circuit is detected to increase the voltage change detected by the detection pin. The present technical solution improves the detection capability of the control chip by strengthening the voltage detection of the control chip when the auxiliary power supply is short-circuited, thereby achieving more timely auxiliary power supply protection.

[0027] In addition, the photovoltaic inverter provided by the utility model includes the above-mentioned auxiliary power supply, and the effect is the same as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present utility model, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A structural diagram of an auxiliary power supply provided by an embodiment of the utility model;

[0030] The reference numerals are as follows: 1 is a short-circuit protection circuit. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0032] The core of the utility model is to provide an auxiliary power supply and a photovoltaic inverter, so as to realize more timely and accurate short-circuit protection for the auxiliary power supply.

[0033] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] Figure 1 A structural diagram of an auxiliary power supply provided by an embodiment of the utility model, such as Figure 1 As shown, the auxiliary power supply includes a transformer, a control chip, a sampling resistor R, a feedback pin COMP of the control chip is connected to the output main winding of the transformer through a feedback circuit; a detection pin CS of the control chip is grounded through the sampling resistor R, an output pin OUT of the control chip is connected to the input end of the transformer through a field effect transistor Q, and the source of the field effect transistor Q is grounded through the sampling resistor R; and also includes:

[0035] Short circuit protection circuit 1;

[0036] The input end of the short-circuit protection circuit 1 is connected to the feedback pin COMP of the control chip, and the output end is connected to the detection pin CS of the control chip;

[0037] The short circuit protection circuit 1 includes a detection circuit and a voltage source circuit;

[0038] The detection circuit is connected to the feedback pin COMP as the input end of the short-circuit protection circuit 1, and is used to detect the level change of the feedback pin COMP, and cut off or turn on the connection line between the voltage source circuit and the detection pin CS according to the level change.

[0039] Photovoltaic inverters are crucial equipment in photovoltaic power generation, and they are responsible for controlling the power of solar panels and converting DC to AC. Each photovoltaic inverter has one or more sets of auxiliary power supplies to participate in the control and drive circuits, such as lighting equipment and signal display in the power station.

[0040] like Figure 1 In the auxiliary power supply shown, the secondary of the transformer may have multiple output windings. Due to the magnetic attraction between the windings, when a winding is short-circuited and the voltage becomes smaller, the voltage of other windings will also become smaller. Therefore, an output main winding can be selected from the output windings, and the feedback pin COMP of the control chip is connected to the output main winding of the transformer through the feedback circuit. By detecting the voltage change of the output main winding, the output voltage change of the auxiliary power supply can be detected. Among them, the switch component Q3 can be TL431, and the feedback circuit mainly detects the voltage change through the optocoupler U. When the auxiliary power supply operates normally, the output main winding can output a stable 12V voltage. After the relevant resistor voltage is divided, the light-emitting side of the optocoupler U is turned on to generate current, and then the light-receiving side is turned on to pull down the voltage of the feedback pin COMP of the control chip to maintain a voltage value of about 2-3V. The output pin OUT of the control chip normally generates waves to control the field effect tube Q to work.

[0041] When one of the windings at the output end of the transformer is short-circuited, due to the principle of magnetic induction, the output winding voltage will be pulled down, making the 12V voltage of the output main winding lower, and then the feedback circuit is connected and after the resistor voltage is divided, the switch component Q3 cannot work, and then the optocoupler U is not turned on, and the voltage of the feedback pin COMP changes from the original low voltage to high. At this time, the feedback voltage received by the control chip suddenly rises to a voltage value of about 5V. The short-circuit protection circuit 1 in this application collects the feedback voltage increase through the detection circuit, thereby turning on the voltage source circuit, thereby adding the output voltage of the voltage source to the detection pin CS of the control chip, specifically the current detection pin CS, so that the control chip detects CS overcurrent and quickly blocks the wave protection, turning off the field effect tube Q, if it is a momentary short circuit, the control chip continues to generate waves after the short circuit is released. If it is a long-term short circuit, the entire output is reduced to 0, the output power is turned off, until the output short circuit protection is released, and the control chip starts to work again. CS is the current detection pin of the control chip. When the current passing through the sampling resistor R increases, the voltage increases synchronously. When it exceeds the upper line voltage of the control chip (for example, 1V), the control chip stops emitting waves.

[0042] In this embodiment, the function of the detection circuit is to detect the level change of the feedback pin COMP. When the auxiliary power supply is short-circuited, it is necessary to control the voltage source circuit to be turned on according to the increase in the level of the feedback pin COMP, thereby improving the current detection of the detection pin CS. Therefore, the detection circuit can be combined with a resistor divider and a switch such as a transistor, a field effect transistor, etc. to realize the detection of the high level and low level of the feedback pin COMP.

[0043] The auxiliary power supply provided by the embodiment of the utility model includes a transformer, a control chip, and a sampling resistor. The feedback pin of the control chip is connected to the output main winding of the transformer through a feedback circuit; the detection pin of the control chip is grounded through a sampling resistor, and the output pin of the control chip is connected to the input end of the transformer through a field effect transistor; it also includes: a short-circuit protection circuit; the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the output end is connected to the detection pin of the control chip; the short-circuit protection circuit includes a detection circuit and a voltage source circuit; the detection circuit is connected to the feedback pin as the input end of the short-circuit protection circuit, and is used to detect the level change of the feedback pin, and cut off or conduct the connection line between the voltage source circuit and the detection pin according to the level change. Compared with the current technology that relies on the current change on the primary side of the transformer when the short circuit occurs, and then determines whether to start the protection through the voltage change of the sampling resistor, which is limited by the resistance of the sampling resistor, resulting in unclear detection of the voltage change and untimely protection, the present technical solution is adopted to increase the voltage detected by the control chip by adding a short-circuit protection circuit to improve the detection capability of the control chip. In the present technical solution, the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the short circuit of the auxiliary power supply is determined by detecting the voltage change of the feedback pin, and the voltage source circuit is turned on when the short circuit is detected to increase the voltage change detected by the detection pin. The present technical solution improves the detection capability of the control chip by strengthening the voltage detection of the control chip when the auxiliary power supply is short-circuited, thereby achieving more timely auxiliary power supply protection.

[0044] On the basis of the above embodiments, this embodiment provides a specific detection circuit structure, including: a sampling circuit and a switch component Q2; the input end of the sampling circuit is connected to the feedback pin COMP, the output end is connected to the control end of the switch component Q2, the first end of the switch component Q2 is connected to the voltage source circuit, and the second end of the switch component Q2 is grounded.

[0045] Among them, the sampling circuit mainly functions to set the conduction range of the switch component Q2 so as to control the voltage source circuit to be turned on when the feedback pin COMP is at a high level. Therefore, the sampling circuit may include a first resistor R1 and a second resistor R2; the first end of the first resistor R1 is connected to the feedback pin COMP as the input end of the sampling circuit, the second end of the first resistor R1 and the first end of the second resistor R2 are commonly connected to the control end of the switch component Q2, and the second end of the switch component Q2 and the second end of the second resistor R2 are grounded.

[0046] In addition, the sampling circuit can also be a comparator; the non-inverting input terminal of the comparator is connected to the feedback pin COMP, the inverting input terminal of the comparator is connected to the reference voltage, and the output terminal of the comparator is connected to the switch component Q2.

[0047] The switch component Q2 in this embodiment is used to realize the switch control of the voltage source circuit. As a specific implementation method, Figure 1 As shown, the switch component Q2 can be TL431, the cathode of TL431 serves as the first end of the switch component Q2, the anode of TL431 serves as the second end of the switch component Q2, and the reference end of TL431 serves as the control end of the switch component Q2. In other embodiments, the switch component Q2 can also be a second triode; the base of the second triode serves as the control end of the switch component Q2, the emitter of the second triode serves as the second end of the switch component Q2, and the collector of the second triode serves as the first end of the switch component Q2. In order to achieve more accurate control, the auxiliary power supply can also include: a sixth resistor; the emitter of the second triode is grounded through the sixth resistor.

[0048] Correspondingly, based on the above embodiments, a voltage source circuit is further provided in the present embodiment, including: a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first transistor Q1, and a voltage stabilizing source; the first ends of the third resistor R3 and the fourth resistor R4 are commonly connected to the voltage stabilizing source, the second end of the third resistor R3 and the first end of the fifth resistor R5 are connected to the first end of the switch component Q2, the second end of the fourth resistor R4 is connected to the emitter of the first transistor Q1, the second end of the fifth resistor R5 is connected to the base of the first transistor Q1, and the collector of the first transistor Q1 is connected to the detection pin CS.

[0049] It can be understood that, due to the circuit structure in this embodiment, the first transistor Q1 is turned on at a low voltage, so the first transistor Q1 should be a PNP transistor.

[0050] In this embodiment, TL431 is a parallel voltage-stabilizing integrated circuit. When the voltage at the reference end reaches the reference 2.5V, the cathode and the anode conduct current. When the circuit is working normally without short circuit, the voltage division value between the first resistor R1 and the second resistor R2 cannot reach 2.5V, and TL431 does not work. When a short circuit occurs, the voltage on the feedback pin COMP is raised so that the voltage division value between the first resistor R1 and the second resistor R2 reaches 2.5V (TL431 internal reference), and TL431 is turned on to work, and the voltage at the connection point between the third resistor R3 and the fifth resistor R5 is pulled down to 0, so that the first transistor Q1 is turned on to work, and the voltage source VREF (5V) is added to CS, so that CS detects a signal greater than 1V and then controls the chip to block the wave.

[0051] On the basis of the above embodiment, in order to avoid interference and achieve more accurate voltage detection, the auxiliary power supply may further include: a capacitor C; a first end of the capacitor C is connected to the second end of the first resistor R1 and the first end of the second resistor R2, and the second end of the capacitor C is grounded.

[0052] Among them, the function of capacitor C is to filter and adjust the protection delay time. If there is an impact voltage at the moment of auxiliary power startup and an interference voltage during operation connected to the sampling circuit, it will be absorbed by capacitor C, so as not to trigger the short-circuit protection by mistake. When short-circuit protection occurs, it takes time for capacitor C to charge after the feedback pin COMP level becomes high. Since the second resistor R2 is connected in parallel with capacitor C, the time for the second resistor R2 to become high is determined by capacitor C. Therefore, selecting a suitable capacitance value for capacitor C can increase the stability of the circuit.

[0053] Finally, the utility model also provides a photovoltaic inverter, including the auxiliary power supply mentioned above.

[0054] The photovoltaic inverter provided by the utility model comprises an auxiliary power supply, which comprises a transformer, a control chip, and a sampling resistor. The feedback pin of the control chip is connected to the output main winding of the transformer through a feedback circuit; the detection pin of the control chip is grounded through a sampling resistor, and the output pin of the control chip is connected to the input end of the transformer through a field effect transistor; and further comprises: a short-circuit protection circuit; the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the output end is connected to the detection pin of the control chip; the short-circuit protection circuit comprises a detection circuit and a voltage source circuit; the detection circuit is connected to the feedback pin as the input end of the short-circuit protection circuit, and is used to detect the level change of the feedback pin, and cut off or conduct the connection line between the voltage source circuit and the detection pin according to the level change. Compared with the current technology that relies on the current change on the primary side of the transformer when the short circuit occurs, and then determines whether to start the protection through the voltage change of the sampling resistor, which is limited by the resistance of the sampling resistor, resulting in unclear detection of the voltage change and untimely protection, the present technical solution is adopted to increase the voltage detected by the control chip by adding a short-circuit protection circuit to improve the detection capability of the control chip. In the present technical solution, the input end of the short-circuit protection circuit is connected to the feedback pin of the control chip, and the short circuit of the auxiliary power supply is determined by detecting the voltage change of the feedback pin, and the voltage source circuit is turned on when the short circuit is detected to increase the voltage change detected by the detection pin. The present technical solution improves the detection capability of the control chip by strengthening the voltage detection of the control chip when the auxiliary power supply is short-circuited, thereby achieving more timely auxiliary power supply protection.

[0055] The auxiliary power supply and photovoltaic inverter provided by the utility model are introduced in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

[0056] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. An auxiliary power supply, comprising a transformer, a control chip, and a sampling resistor, wherein a feedback pin of the control chip is connected to an output main winding of the transformer through a feedback circuit; a detection pin of the control chip is grounded through the sampling resistor, an output pin of the control chip is connected to an input end of the transformer through a field effect transistor, and a source of the field effect transistor is grounded through the sampling resistor; characterized in that: Also includes: Short circuit protection circuit (1); The input end of the short-circuit protection circuit (1) is connected to the feedback pin of the control chip, and the output end is connected to the detection pin of the control chip; The short-circuit protection circuit (1) comprises a detection circuit and a voltage source circuit; The detection circuit is connected to the feedback pin as an input end of the short-circuit protection circuit (1) and is used to detect a level change of the feedback pin and cut off or conduct a connection line between the voltage source circuit and the detection pin according to the level change.

2. The auxiliary power supply according to claim 1, characterized in that: The detection circuit comprises: a sampling circuit and a switch component; The input end of the sampling circuit is connected to the feedback pin, the output end is connected to the control end of the switch component, the first end of the switch component is connected to the voltage source circuit, and the second end of the switch component is grounded.

3. The auxiliary power supply according to claim 2, characterized in that: The sampling circuit includes a first resistor and a second resistor; The first end of the first resistor is connected to the feedback pin as the input end of the sampling circuit, the second end of the first resistor and the first end of the second resistor are commonly connected to the control end of the switch component, and the second end of the switch component and the second end of the second resistor are grounded.

4. The auxiliary power supply according to claim 3, characterized in that: The voltage source circuit comprises: a third resistor, a fourth resistor, a fifth resistor, a first triode, and a voltage stabilizing source; The first ends of the third resistor and the fourth resistor are commonly connected to the voltage stabilizing source, the second end of the third resistor and the first end of the fifth resistor are connected to the first end of the switch component, the second end of the fourth resistor is connected to the emitter of the first transistor, the second end of the fifth resistor is connected to the base of the first transistor, and the collector of the first transistor is connected to the detection pin.

5. The auxiliary power supply according to claim 4, characterized in that: The switch component is TL431, the cathode of the TL431 serves as the first end of the switch component, the anode of the TL431 serves as the second end of the switch component, and the reference end of the TL431 serves as the control end of the switch component.

6. The auxiliary power supply according to claim 4, characterized in that: The switch component is a second transistor; the base of the second transistor serves as the control end of the switch component, the emitter of the second transistor serves as the second end of the switch component, and the collector of the second transistor serves as the first end of the switch component.

7. The auxiliary power supply according to claim 2, characterized in that: The sampling circuit is a comparator; The non-inverting input terminal of the comparator is connected to the feedback pin, the inverting input terminal of the comparator is connected to a reference voltage, and the output terminal of the comparator is connected to the switch component.

8. The auxiliary power supply according to claim 5, characterized in that: Also includes: capacitance; A first end of the capacitor is connected to the second end of the first resistor and the first end of the second resistor, and a second end of the capacitor is grounded.

9. The auxiliary power supply according to claim 6, characterized in that: Also includes: a sixth resistor; The emitter of the second transistor is grounded through the sixth resistor.

10. A photovoltaic inverter, characterized in that: An auxiliary power supply comprising any one of claims 1 to 9.

Images