TWI527357B - Inverter and power supply method thereof and application using the same - Google Patents

Description

Inverter and its power supply method and application

The invention relates to a power conversion technology, and in particular to an inverter and a power supply method and application thereof.

In the design of the inverter, its auxiliary circuit (such as control part, drive part or communication part) usually needs different isolation voltage (such as 12V, 5V) as the power supply, so design a reliable and simple structure. The power supply to provide the auxiliary power required for the auxiliary circuit is important to ensure the high efficiency and stable operation of the inverter.

In the prior art, a flyback converter is often used as a power supply circuit for providing an auxiliary power source. However, in some inverter applications, the use of a flyback converter to provide auxiliary power to the inverter can in turn generate unintended power waste. For example, when the inverter is applied to a photovoltaic grid-connected system (referred to herein as a photovoltaic inverter), since the DC input voltage of the photovoltaic inverter is a photovoltaic module (photovoltaic module) ), and the output of the photovoltaic module will be followed by sunlight The strength of the relationship is related. Therefore, the magnitude of the DC input voltage actually received by the PV inverter will vary over time, so that the PV inverter will not remain operating at rated power. More specifically, at this time, the photovoltaic inverter is operated at a light load for most of the time, so the conversion efficiency of the photovoltaic inverter cannot be fully measured by the conversion efficiency at the rated power, and the European efficiency is also required (ie, , according to different weights to accumulate the conversion efficiency under different load conditions).

However, due to its high voltage stress and hard switching characteristics, the flyback converter has low conversion efficiency when operating at light loads, making the photovoltaic inverter using the flyback converter as the auxiliary power supply circuit. European efficiency cannot be improved.

The present invention provides an inverter that can improve conversion efficiency when operating at light loads.

The inverter of the present invention includes a DC-to-DC conversion circuit, an inverter circuit, and an auxiliary power supply circuit. The DC-to-DC converter circuit receives the DC input voltage from the DC input side and converts the DC input voltage to a DC bus voltage. The inverter circuit is coupled to a DC-to-DC converter circuit for converting the DC bus voltage into an AC output voltage. The auxiliary power supply circuit is coupled to the DC to DC conversion circuit and receives the DC input voltage from the DC input side. Wherein, the auxiliary power supply circuit is activated in response to the DC input voltage, and the auxiliary power supply circuit generates a first auxiliary power source required for controlling the operation of the DC-to-DC conversion circuit after startup. Among them, DC to DC conversion circuit Reacting in response to the first auxiliary power source, and generating a second auxiliary power source for controlling the operation of the inverter circuit after the DC-to-DC conversion circuit is started, so that the inverter circuit is activated and generated in response to the second auxiliary power source AC output voltage.

In an embodiment of the invention, the DC-to-DC conversion circuit includes a first switching circuit, an isolation transformer, a rectifying and filtering circuit, and a first auxiliary circuit. The first switching circuit receives a DC input voltage from a DC input side. The isolation transformer has a primary side winding, a first secondary side winding, and a second secondary side winding, wherein the primary side winding is coupled to the first switching circuit. The rectifying and filtering circuit is coupled between the isolation transformer and the inverter circuit for rectifying and filtering the output of the first and second secondary windings, wherein the rectifying and filtering circuit generates the DC bus voltage according to the output of the first secondary winding And generating a second auxiliary power source according to the output of the second secondary winding. The first auxiliary circuit is coupled to the auxiliary power supply circuit, wherein the first auxiliary circuit operates under the first auxiliary power supply to provide a first auxiliary function of the DC-to-DC conversion circuit.

In an embodiment of the invention, the inverter circuit includes a second switching circuit and a second auxiliary circuit. The second switching circuit is coupled to the first secondary winding via a rectifying and filtering circuit to receive the DC bus voltage. The second auxiliary circuit is coupled to the second secondary winding via the rectifying filter circuit, wherein the second auxiliary circuit operates under the second auxiliary power supply to provide the second auxiliary function of the inverter circuit.

In an embodiment of the invention, the first auxiliary circuit includes a first control circuit for controlling the operation of the first switching circuit, and the second auxiliary circuit includes a second control circuit for controlling the operation of the second switching circuit.

In an embodiment of the invention, the first auxiliary circuit and the second auxiliary circuit are One of the less includes at least one of an overvoltage protection circuit, an overload protection circuit, and an overcurrent protection circuit.

In an embodiment of the invention, the DC-to-DC conversion circuit is an isolated DC-to-DC converter.

In an embodiment of the invention, the auxiliary power supply circuit is a non-isolated DC-to-DC converter.

The photovoltaic grid-connected system of the present invention has an inverter as described above.

The power supply method of the inverter of the present invention comprises the steps of: receiving a DC input voltage from a DC input side of a DC-to-DC converter circuit to activate an auxiliary power circuit; and generating an auxiliary power supply circuit for controlling DC-DC An auxiliary power source required for the operation of the conversion circuit to start the DC-to-DC conversion circuit; the DC-to-DC conversion circuit after the startup converts the DC input voltage into a DC bus voltage, and generates an operation for controlling the inverter circuit A second auxiliary power source is required to start the inverter circuit; and the DC bus voltage is converted into an AC output voltage by the inverter circuit after startup.

Based on the above, an embodiment of the present invention provides an inverter and a power supply method and application thereof. The inverter can utilize the DC-to-DC conversion circuit of the preceding stage to generate the auxiliary power required by the inverter circuit of the latter stage, so that the auxiliary power supply circuit only needs to provide the auxiliary power required by the DC-to-DC conversion circuit. Therefore, since the auxiliary power supply circuit does not need to supply power to the inverter circuit, the auxiliary power supply circuit can be realized by using a non-isolated DC-to-DC converter, thereby reducing the power loss of the auxiliary power supply circuit.

In order to make the above features and advantages of the present invention more apparent, the following is a special The embodiments are described in detail below in conjunction with the drawings.

10‧‧‧Photovoltaic grid-connected system

100, 300, 400‧‧‧ inverter

110, 310, 410‧‧‧DC to DC conversion circuit

120, 320, 420‧‧‧ inverter circuit

130, 330, 430‧‧‧Auxiliary power circuit

312, 412‧‧‧ first switch circuit

314, 414‧‧‧Isolation transformer

316, 416‧‧ ‧ Rectifier filter circuit

318‧‧‧First auxiliary circuit

322, 422‧‧‧ second switch circuit

324‧‧‧Second auxiliary circuit

418‧‧‧First control circuit

424‧‧‧Second control circuit

C1, C2‧‧‧ filter capacitor

C3~C6, Cr‧‧‧ resonant capacitor

Ci‧‧‧ input capacitor

Cout‧‧‧ output capacitor

EG‧‧‧ grid

GND‧‧‧ ground terminal

Lr, Lm, Lin‧‧‧ resonant inductor

NP‧‧‧ primary winding

NS1, NS2‧‧‧ secondary winding

PVm‧‧‧PV modules

Q1~Q8‧‧‧Switching transistor

S1~S8‧‧‧ control signal

S610~S640‧‧‧Steps

Tin‧‧‧DC input side

T1, t2, t3‧‧‧ time

Vbus‧‧‧ DC bus voltage

VCC1, VCC2‧‧‧Auxiliary power supply

Vin‧‧‧DC input voltage

Vout‧‧‧AC output voltage

FIG. 1 is a schematic diagram of an inverter according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the startup sequence of the inverter according to the embodiment of FIG. 1. FIG.

FIG. 3 is a schematic diagram of an inverter according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of a circuit structure of an inverter according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a photovoltaic grid-connected system of an inverter to which an embodiment of the present invention is applied.

FIG. 6 is a flow chart showing the steps of a power supply method of an inverter according to an embodiment of the present invention.

The embodiment of the invention provides an inverter and a power supply method and application thereof. In the embodiment of the present invention, the inverter can utilize the pre-stage circuit to generate the auxiliary power required by the subsequent stage circuit, so that the auxiliary power supply circuit in the inverter only needs to provide the auxiliary power required by the pre-stage circuit. Accordingly, since the auxiliary power supply circuit does not need to supply power to the subsequent stage circuit, the auxiliary power supply circuit can be implemented by using a non-isolated DC-to-DC converter, thereby reducing the power loss of the auxiliary power supply circuit. In order to make the disclosure of the present disclosure easier to understand, the following specific embodiments are examples of the disclosure that can be implemented. In addition, wherever possible, the same elements, components, and steps in the drawings and embodiments are used to represent the same or similar components.

FIG. 1 is a schematic diagram of an inverter according to an embodiment of the present invention. Referring to FIG. 1 , the inverter 100 includes a DC-DC conversion circuit 110 , an inverter circuit 120 , and an auxiliary power supply circuit 130 .

The DC-to-DC conversion circuit 110 receives the DC input voltage Vin from the DC input side Tin, and accordingly converts the DC input voltage Vin into the DC bus voltage Vbus. The inverter circuit 120 is coupled to the DC-to-DC converter circuit 110 to receive the DC bus voltage Vbus and converts the DC bus voltage into an AC output voltage Vout. The DC-DC conversion circuit 110 and the inverter circuit 120 form a two-stage inverter circuit architecture. The auxiliary power supply circuit 130 is coupled to the DC-DC conversion circuit 110, and receives the DC input voltage Vin from the DC input side Tin to supply power to the DC-DC conversion circuit 110 of the preceding stage, and the power supply required by the inverter circuit 120 of the subsequent stage. It is provided by the DC-to-DC converter circuit 110.

More specifically, in the embodiment, when the DC input side Tin receives the DC input voltage Vin, the auxiliary power supply circuit 130 is activated in response to the received DC input voltage Vin, and is generated to control the DC after startup. The auxiliary power source VCC1 required for the operation of the DC converter circuit 110 is used by the DC-to-DC converter circuit 110.

After the DC-DC conversion circuit 110 is activated in response to the auxiliary power supply VCC1, it starts a power conversion operation of boosting or stepping down the DC input voltage Vin, thereby generating a DC bus voltage Vbus and controlling the inverter circuit 120, respectively. The auxiliary power source VCC2 required for operation is used by the inverter circuit 120, so that the inverter circuit 120 can convert the DC bus voltage Vbus into the AC output voltage Vout.

Based on the circuit operation described above, the inverter 100 will have a startup sequence as shown in FIG. 2 is a schematic diagram of the startup sequence of the inverter according to the embodiment of FIG. 1.

Referring to FIG. 1 and FIG. 2 simultaneously, first, when the DC input side Tin receives the DC input voltage Vin at time t1, the auxiliary power supply circuit 130 is powered on from the DC input side Tin, and is activated in the auxiliary power supply circuit 130. After the time t2 of the operating state, the auxiliary power source VCC1 is supplied to the DC-to-DC converter circuit 110. Next, the DC-DC conversion circuit 110 is started when the auxiliary power supply VCC1 is obtained, and the auxiliary power supply VCC2 is supplied to the inverter circuit 120 after the time t3 when the DC-DC conversion circuit 110 enters the stable operation state.

In detail, under the architecture of the inverter 100, since the auxiliary power supply VCC2 required by the inverter circuit 120 of the subsequent stage is provided by the DC-DC conversion circuit 110, the auxiliary power supply circuit 130 only needs to convert DC-to-DC. The circuit 110 can be powered. Furthermore, since the design of the auxiliary power supply circuit 130 does not require further consideration of the power supply to the inverter circuit 120 of the subsequent stage, the auxiliary power supply circuit 130 does not need to use an isolated DC-to-DC converter as in the conventional auxiliary power supply circuit. This can be achieved, for example, by a flyback converter, but only with a non-isolated DC-to-DC converter.

More specifically, since the auxiliary power supply circuit 130 of the embodiment of the present invention has a non-isolated type of architecture, the auxiliary power supply circuit 130 can have higher conversion efficiency than the conventional auxiliary power supply circuit, and the circuit design The complexity is also low. On the other hand, since the auxiliary power supply circuit 130 only needs to supply power to the front stage circuit, Therefore, the required power is also smaller than the conventional auxiliary power supply circuit. All of the above characteristics can greatly reduce the power loss of the auxiliary power supply circuit 130 of the embodiment of the present invention, thereby improving the conversion efficiency of the overall inverter 100, particularly the conversion efficiency under light load.

It is worth mentioning that the present invention does not limit the specific circuit configuration of the DC-DC conversion circuit 110 and the inverter circuit 120 to which the inverter 100 is applied. In other words, the DC-DC conversion circuit 110 can have a half-bridge asymmetry, a half-bridge symmetry, a full-bridge or other feasible circuit configuration, and the inverter circuit 120 is the same, and the present invention does not limit this.

In order to more clearly illustrate an embodiment of the present invention, FIG. 3 is a schematic diagram of an inverter according to another embodiment of the present invention. Referring to FIG. 3, the inverter 300 includes a DC-to-DC conversion circuit 310, an inverter circuit 320, and an auxiliary power supply circuit 330.

In the present embodiment, the DC-DC conversion circuit 310 includes a first switch circuit 312, an isolation transformer 314, a rectification filter circuit 316, and a first auxiliary circuit 318. The first switching circuit 312 receives the DC input voltage Vin from the DC input side Tin. The isolation transformer 314 has a primary side winding NP and secondary side windings NS1 and NS2, wherein the primary side winding NP is coupled to the first switching circuit 312. The rectifying and filtering circuit 316 is coupled between the isolation transformer 314 and the inverter circuit 320 for rectifying and filtering the output of the secondary windings NS1 and NS2, wherein the rectifying and filtering circuit 316 generates a DC bus according to the output of the secondary winding NS1. The voltage Vbus, and the auxiliary power source VCC2 is generated according to the output of the secondary side winding NS2. The first auxiliary circuit 318 is coupled to the auxiliary power circuit 330, wherein the first auxiliary circuit 318 operates under the auxiliary power source VCC1 to provide a specific auxiliary function.

The inverter circuit 320 includes a second switching circuit 322 and a second auxiliary circuit 324. The second switching circuit 322 is coupled to the secondary side winding NS1 via the rectifying and filtering circuit 310 to receive the DC bus voltage Vbus. The second auxiliary circuit 324 is coupled to the secondary side winding NS2 via the rectifying and filtering circuit 310, wherein the second auxiliary circuit 324 operates under the auxiliary power source VCC2 to provide an auxiliary function specific to the inverter circuit 320.

In the present embodiment, the DC-DC conversion circuit 310 is implemented using an isolated DC-to-DC converter, and the auxiliary power supply circuit 330 is implemented using a non-isolated DC-DC converter. More specifically, the DC-DC conversion circuit 310 of the present embodiment utilizes an isolation transformer 314 architecture having a plurality of secondary side windings NS1 and NS2 to provide the auxiliary power supply VCC2. The size of the auxiliary power source VCC2 can be adjusted based on the turns ratio of the primary side winding NP and the secondary side winding NS2.

The first auxiliary circuit 318 described in this embodiment may include a first control circuit (not shown) for controlling the first switch circuit 312, and the second auxiliary circuit 324 may include a second control circuit 322 for controlling the second switch circuit 322. Two control circuits (not shown). The first and second control circuits start to operate after receiving the corresponding auxiliary power sources VCC1 and VCC2, and respectively generate control signals to control switching of the corresponding switch circuits 312 and 322, thereby adjusting the DC-to-DC conversion circuit. 310 and power conversion of the inverter circuit 320.

On the other hand, according to the designer's circuit design requirements, the first auxiliary circuit 310 and the second auxiliary circuit 320 may further include different types of protection circuits, such as over voltage protection (OVP) circuits, overload protection (over load) Protection, OLP) circuit or over current protection (over current protection, OCP) and so on. The power supply of the control circuit and/or the protection circuit in the first auxiliary circuit 318 is provided by the auxiliary power supply VCC1 outputted by the auxiliary power supply circuit 330, and the control circuit and/or the protection circuit of the second auxiliary circuit 324 are provided. The power supply is provided by the auxiliary power source VCC2 output from the DC-to-DC converter circuit 310.

Further, although the present embodiment is an embodiment in which the isolation transformer 314 having the two secondary side windings NS1 and NS2 is taken as an example, the present invention is not limited thereto. In other embodiments, the isolation transformer 314 can also be implemented by using an isolation transformer having three or more secondary windings according to the design of the inverter circuit 320 of the subsequent stage, thereby providing the auxiliary power supply VCC2 having different voltage levels. Used by the inverter circuit 320.

The power supply and operation mechanism of the inverter of the embodiment of the present invention is illustrated by a specific inverter circuit architecture, as shown in FIG. 4 . 4 is a schematic diagram of a circuit structure of an inverter according to an embodiment of the present invention.

Referring to FIG. 4, the inverter 400 includes a DC-to-DC conversion circuit 410, an inverter circuit 420, and an auxiliary power supply circuit 430. In the present embodiment, the DC-DC conversion circuit 410 of the front stage is a full-bridge series-type resonant converter (one type of isolated DC-to-DC power converter), and the inverter circuit 420 of the latter stage is The bridge inverter is taken as an example, but the present invention is not limited to this. In addition, the auxiliary power supply circuit 430 can be implemented in the present embodiment by using a buck conversion chip (BUCK IC), which is a wafer in which a buck converter and its control circuit are integrated together. However, the present invention is not limited to this.

Specifically, the DC input voltage Vin is coupled to the input capacitor Ci and coupled to the DC-DC conversion circuit 410. The DC-to-DC conversion circuit 410 includes a A switch circuit 412, an isolation transformer 414, a rectification filter circuit 416, and a first control circuit 418. The first switching circuit 412 is composed of switching transistors Q1 to Q4, a resonant capacitor Cr, and resonant inductors Lr and Lm. The switching transistors Q1~Q4 are coupled between the DC input voltage Vin and the ground GND. The switching transistors Q1 and Q2 are connected in series to form a bridge arm, and the switching transistors Q3 and Q4 are connected in series to form another bridge arm.

In the present embodiment, the auxiliary power supply circuit 430 is activated in response to the DC input voltage Vin and generates an auxiliary power source VCC1 (for example, a voltage of 5V, 12V). After the auxiliary power supply circuit 430 is activated, the first control circuit 418 generates control signals S1 to S4 for controlling the switching transistors Q1 to Q4 in response to the auxiliary power supply VCC1 provided by the auxiliary power supply circuit 430. The switching transistors Q1~Q4 are respectively controlled by the control signals S1~S4 and alternately turned on or off in a complementary/switching manner, thereby outputting the DC input voltage Vin to a resonance composed of the resonant capacitor Cr and the resonant inductors Lr and Lm. Circuit.

The resonant circuit reacts to the switching of the switching transistors Q1~Q4 to charge/discharge, so that the isolation transformer 414 reacts with the voltage change on the primary winding NP and respectively generates corresponding values on the secondary windings NS1 and NS2. Output voltage.

The rectifying and filtering circuit 416 is exemplified by a circuit architecture including diodes D1 to D4 and filter capacitors C1 and C2. Among them, the diodes D1 and D2 constitute a half-bridge rectifier and rectify the output of the secondary winding NS1 to generate a DC bus voltage Vbus. The diodes D3 and D4 form another half bridge rectifier and rectify the output of the secondary winding NS2 to generate an auxiliary power supply. VCC2. The filter capacitors C1 and C2 are respectively connected between the common-polarity terminal (the hit-end end) and the center-tapped terminal of the secondary windings NS1 and NS2 to respectively filter the DC bus voltage Vbus and The non-DC component of the auxiliary power source VCC2 is supplied to the inverter circuit 420 with the DC bus voltage Vbus and the auxiliary power source VCC2, respectively.

The inverter circuit 420 includes a second switch circuit 422 and a second control circuit 424. The second switching circuit 422 is composed of switching transistors Q5~Q8, resonant capacitors C3~C6 and resonant inductor Lin. The switching transistors Q5~Q8 are coupled between the DC bus voltage Vbus and the ground GND. The switching transistors Q5 and Q6 are connected in series to form a bridge arm, and the switching transistors Q7 and Q8 are connected in series to form another bridge arm.

After the DC-DC conversion circuit 410 is activated in response to the auxiliary power supply VCC1 and the auxiliary power supply VCC2 is generated, the second control circuit 424 is generated in response to the auxiliary power supply VCC2 provided by the DC-DC conversion circuit 410 to control the switching transistor Q5. ~Q8 control signal S5~S8. The switching transistors Q5~Q8 are respectively controlled to be alternately turned on or off in a complementary/switching manner by the control signals S5~S8, thereby converting the DC bus voltage Vbus into an AC output voltage Vout.

Similar to the foregoing embodiment, since the auxiliary power supply VCC2 required by the inverter circuit 420 of the present embodiment is provided by the DC-DC conversion circuit 410 of the preceding stage, the auxiliary power supply circuit 430 only needs to be the DC-DC of the front stage. The conversion circuit 410 supplies the auxiliary power source VCC1, so the required power is small, and the corresponding power loss is also small. Therefore, the inverter 400 can have a high conversion efficiency even when operating at a light load.

FIG. 5 is a schematic diagram of a photovoltaic grid-connected system to which the inverter 100 of the foregoing embodiment is applied. Referring to FIG. 5, in the architecture of the embodiment, the inverter 100 uses the output of the PV module PVm as the DC input voltage Vin, and the AC output voltage Vout generated by the inverter 100 is provided to the back end of the grid EG. use. In this case, since the inverter 100 can effectively improve the conversion efficiency under light load conditions, the system efficiency of the overall photovoltaic grid-connected system 10 is not greatly increased even when the sunlight intensity is weakened by the influence of weather. Impact.

FIG. 6 is a flow chart showing the steps of a power supply method of an inverter according to an embodiment of the present invention. The power supply method described in this embodiment can be applied to the inverter 100, 300 or 400 as in the foregoing embodiment. Referring to FIG. 6, the power supply method includes the steps of: receiving a DC input voltage from a DC input side of a DC-to-DC conversion circuit (eg, 110, 310, 410) to activate an auxiliary power circuit (eg, 130, 330, 430) ( Step S610): The auxiliary power supply circuit after the startup generates the first auxiliary power required for the operation of the DC-DC conversion circuit to start the DC-DC conversion circuit (step S620); and the DC-to-DC conversion circuit after the startup is the DC input voltage Converting to a DC bus voltage, and generating a second auxiliary power required for operation of the inverter circuit (eg, 120, 320, 420) to start the inverter circuit (step S630); and converting the DC bus voltage by the inverter circuit after startup The output voltage is AC (step S640).

The power supply method described in the embodiment of FIG. 6 can obtain sufficient support and teaching according to the foregoing description of FIG. 1 to FIG. 5, and thus similarities or repetitions are not described herein again.

In summary, the embodiment of the present invention provides an inverter and a power supply method thereof. And application. The inverter can utilize the DC-to-DC conversion circuit of the preceding stage to generate the auxiliary power required by the inverter circuit of the latter stage, so that the auxiliary power supply circuit only needs to provide the auxiliary power required by the DC-to-DC conversion circuit. Therefore, since the auxiliary power supply circuit does not need to supply power to the inverter circuit, the auxiliary power supply circuit can be realized by using a non-isolated DC-to-DC converter, thereby reducing the power loss of the auxiliary power supply circuit.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Inverter

110‧‧‧DC to DC converter circuit

120‧‧‧Inverter circuit

130‧‧‧Auxiliary power circuit

Tin‧‧‧DC input side

Vbus‧‧‧ DC bus voltage

VCC1, VCC2‧‧‧Auxiliary power supply

Vin‧‧‧DC input voltage

Vout‧‧‧AC output voltage

Claims (13)

An inverter includes: a DC-to-DC conversion circuit that receives a DC input voltage from a DC input side, and converts the DC input voltage into a DC bus voltage; an inverter circuit coupled to the DC pair a DC conversion circuit for converting the DC bus voltage into an AC output voltage; and an auxiliary power supply circuit coupled to the DC to DC conversion circuit and receiving the DC input voltage from the DC input side, wherein the auxiliary power supply The circuit is activated in response to the DC input voltage, and the auxiliary power supply circuit generates a first auxiliary power source for controlling operation of the DC-to-DC conversion circuit after startup, wherein the first auxiliary power source is only used to The DC-to-DC conversion circuit supplies power, wherein the DC-to-DC conversion circuit is activated in response to the first auxiliary power supply, and the DC-to-DC conversion circuit generates a first required to control the operation of the inverter circuit after startup And an auxiliary power source for causing the inverter circuit to start and generate the AC output voltage in response to the second auxiliary power source. The inverter of claim 1, wherein the DC-to-DC conversion circuit comprises: a first switching circuit receiving the DC input voltage from the DC input side; and an isolation transformer having a primary winding a first secondary winding and a second secondary winding, wherein the primary winding is coupled to the first switching circuit; a rectifying and filtering circuit coupled between the isolation transformer and the inverter circuit for rectifying and filtering the output of the first and second secondary windings, wherein the rectifying and filtering circuit is based on the first secondary side The output of the winding generates the DC bus voltage, and generates the second auxiliary power according to the output of the second secondary winding; and a first auxiliary circuit coupled to the auxiliary power circuit, wherein the first auxiliary circuit operates A first auxiliary function is provided under the first auxiliary power supply to provide the DC-to-DC conversion circuit. The inverter of claim 2, wherein the inverter circuit comprises: a second switch circuit, coupled to the first secondary winding via the rectifying filter circuit to receive the DC bus voltage; and a The second auxiliary circuit is coupled to the second secondary winding via the rectifying and filtering circuit, wherein the second auxiliary circuit operates under the second auxiliary power to provide a second auxiliary function of the inverter circuit. The inverter of claim 3, wherein the first auxiliary circuit includes a first control circuit for controlling operation of the first switching circuit, and the second auxiliary circuit includes A second control circuit for the operation of the two switching circuits. The inverter of claim 3, wherein at least one of the first auxiliary circuit and the second auxiliary circuit comprises an overvoltage protection circuit, an overload protection circuit, and an overcurrent protection circuit. One. The inverter of claim 1, wherein the DC-to-DC conversion circuit is an isolated DC-to-DC converter. The inverter of claim 1, wherein the auxiliary power supply circuit is a non-isolated DC-to-DC converter. A photovoltaic grid-connected system, comprising: the inverter according to claim 1; a photovoltaic module coupled to the DC input side and configured to react to The DC input voltage is generated by the intensity of a light source; and a power grid coupled to the inverter to receive and use the AC output voltage. The photovoltaic grid-connected system of claim 8, wherein the DC-to-DC converter circuit comprises: a first switch circuit, receiving the DC input voltage from the DC input side; and an isolation transformer having a primary side a winding, a first secondary winding, and a second secondary winding, wherein the primary winding is coupled to the first switching circuit, and the first secondary winding is coupled to the inverter circuit to provide the DC bus a voltage rectifying circuit coupled to the second secondary winding and the inverter circuit for rectifying and filtering the output of the secondary winding, and generating the second auxiliary power source; and a first An auxiliary circuit coupled to the auxiliary power supply circuit, wherein the first auxiliary circuit operates under the first auxiliary power supply to provide the first DC-to-DC conversion circuit Accessibility. The photovoltaic grid-connected system of claim 9, wherein the inverter circuit comprises: a second switch circuit coupled to the first secondary winding via the rectifier filter circuit to receive the DC bus voltage; And a second auxiliary circuit coupled to the second secondary winding via the rectifying and filtering circuit, wherein the second auxiliary circuit operates under the second auxiliary power to provide a second auxiliary function of the inverter circuit. The photovoltaic grid-connected system of claim 10, wherein the first auxiliary circuit includes a first control circuit for controlling operation of the first switch circuit, and the second auxiliary circuit includes A second control circuit that operates the second switching circuit. The photovoltaic grid-connected system of claim 10, wherein at least one of the first auxiliary circuit and the second auxiliary circuit comprises an overvoltage protection circuit, an overload protection circuit, and an overcurrent protection circuit. one. A power supply method for an inverter, wherein the inverter includes a DC-to-DC conversion circuit, an inverter circuit, and an auxiliary power supply circuit, the power supply method includes: receiving from the DC input side of the DC-DC conversion circuit Flowing an input voltage to activate the auxiliary power supply circuit; and the auxiliary power supply circuit after startup generates a first auxiliary power source for controlling operation of the DC-to-DC conversion circuit to start the DC-to-DC conversion power The first auxiliary power source is only used to supply the DC-to-DC conversion circuit; the DC-to-DC conversion circuit after the startup converts the DC input voltage into a DC bus voltage, and is generated to control the inverter. A second auxiliary power source required for operation of the circuit to activate the inverter circuit; and the DC bus voltage converted to an AC output voltage by the activated inverter circuit.