Isolation power supply circuit with multiplexed output and inverter system

Abstract

The utility model discloses a multi-output isolation power supply circuit and an inverter system, and belongs to the technical field of power electronics, and the isolation power supply circuit comprises a plurality of groups of transformers which are isolated from one another; the capacitor unit is connected in parallel with the primary windings of the plurality of groups of transformers; a switching tube connected in series with the capacitor unit; and the control chip is connected with the capacitor unit and the switching tube, and is used for outputting PWM (Pulse Width Modulation) adaptive to the resonant frequency generated by the plurality of groups of transformers and the capacitor unit, so that the whole circuit works in a soft switching state. Through the arrangement structure, not only can the design cost required by the isolation power supply circuit be greatly reduced, but also the space volume occupied by the isolation power supply circuit can be reduced. Moreover, the isolation power supply circuit adopts a soft switching mode to generate the driving voltage, so that the working efficiency of the isolation power supply circuit can be further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to an isolated power supply circuit with multiple outputs and an inverter system. Background Art

[0002] Since the multi-channel output isolated power supply circuit can provide multiple driving voltages to the multi-phase half-bridge switch tubes, the multi-channel output isolated power supply circuit has been widely used in practical applications. In the prior art, the following three methods are usually used to build a multi-channel output isolated power supply circuit. The first is to use a flyback structure to build a multi-channel output isolated power supply circuit; the second is to use multiple PWM (Pulse Width Modulation) control chips, and combine push-pull structure and full-bridge hard switch to build a multi-channel output isolated power supply circuit; the third is to use multiple LLC (a power supply topology, including a resonant capacitor, a resonant inductor and a transformer) control chips to build a multi-channel output isolated power supply circuit.

[0003] However, in the first construction method, multiple sets of transformer windings will be wound on the same magnetic core, which not only causes the transformer to be larger in size and have more layers, but also, in this construction method, the distance between the transformer and the switch tube is far, and multiple sets of connecting wires need to be pulled out from the transformer end to different switch tubes. At the same time, the insulation withstand voltage problem between multiple sets of connecting wires needs to be considered, resulting in the multi-output isolated power supply circuit built by the flyback structure to occupy a very large space volume. In the second and third construction methods, multiple control chips are required to drive multiple transformers, which undoubtedly increases the cost of the device. In addition, the use of hard switching will result in large losses in the multi-output isolated power supply circuit. At present, there is no more effective solution to this technical problem. Utility Model Content

[0004] In view of this, the purpose of the utility model is to provide a multi-channel output isolated power supply circuit and an inverter system to solve the technical problems of large space occupation, high no-load loss and high construction cost in the prior art when building a multi-channel output isolated power supply circuit. The specific scheme is as follows:

[0005] In order to solve the above technical problems, the utility model provides a multi-channel output isolation power supply circuit, comprising:

[0006] Multiple sets of transformers isolated from each other;

[0007] A capacitor unit connected in parallel with the primary windings of multiple sets of transformers;

[0008] A switch tube connected in series with the capacitor unit;

[0009] A control chip connected to both the capacitor unit and the switch tube, used to output PWM adapted to the resonant frequency generated by the multiple sets of transformers and the capacitor unit, so that the entire circuit works in a soft switching state.

[0010] Preferably, it further comprises: a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, a second capacitor and a third capacitor;

[0011] Among them, the second end of the control chip is connected to the first end of the second resistor, the third end of the control chip is connected to the first end of the third resistor, the fourth end of the control chip is respectively connected to the second end of the first resistor and the first end of the first capacitor, the fifth end of the control chip is connected to the first end of the fifth resistor, the sixth end of the control chip is connected to the first end of the fourth resistor, the second end of the fourth resistor is respectively connected to the control end of the switch tube and the second end of the fifth resistor, the seventh end of the control chip is connected to the power supply, the eighth end of the control chip is respectively connected to the second end of the third capacitor and the first end of the first resistor, the first end of the third capacitor is connected to the second end of the second capacitor, the first end of the second capacitor is connected to the first end of the capacitor unit, the second end of the capacitor unit is connected to the first end of the switch tube, the second end of the switch tube is respectively connected to the first end of the sixth resistor and the first end of the seventh resistor, the second end of the sixth resistor, the second end of the seventh resistor, the second end of the third resistor, the second end of the second resistor, the second end of the first capacitor and the second end of the second capacitor are all grounded.

[0012] Preferably, the switch tube is specifically an NMOS tube;

[0013] The gate of the NMOS tube is the control end of the switch tube, the drain of the NMOS tube is the first end of the switch tube, and the source of the NMOS tube is the second end of the switch tube.

[0014] Preferably, it also includes: a parasitic diode;

[0015] Wherein, the anode of the parasitic diode is connected to the source of the NMOS tube, and the cathode of the parasitic diode is connected to the drain of the NMOS tube.

[0016] Preferably, the primary sides of the multiple groups of transformers are wound with a retaining wall structure or triple insulated wires.

[0017] Preferably, the secondary winding of each transformer in the plurality of groups of transformers is provided with a tap.

[0018] Preferably, it further comprises: a first diode, a second diode, an eighth resistor, a ninth resistor, a fourth capacitor and a fifth capacitor;

[0019] Among them, the positive electrode of the first diode is connected to the first end of the secondary side of the target transformer, the negative electrode of the first diode is connected to the first end of the eighth resistor, the second end of the eighth resistor is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the tap of the secondary winding of the target transformer, the second end of the secondary winding of the target transformer is connected to the negative electrode of the second diode, the positive electrode of the second diode is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to the second end of the fifth capacitor, the first end of the fifth capacitor is connected to the second end of the fourth capacitor, and the second end of the fourth capacitor is grounded; the target transformer is any one of the multiple groups of transformers.

[0020] Preferably, the secondary sides of the multiple groups of transformers supply power to a half-bridge, a full-bridge, a three-phase bridge or multiple half-bridges.

[0021] In order to solve the above technical problems, the utility model also provides an inverter system, including a multi-output isolation power supply circuit as disclosed above.

[0022] It can be seen that in the isolated power supply circuit provided by the present invention, multiple sets of transformers isolated from each other are provided, capacitor units are connected in parallel with the primary sides of the multiple sets of transformers; a switch tube is connected in series with the capacitor unit, and a control chip is provided which is connected to both the capacitor unit and the switch tube and is used to output PWM that matches the resonant frequency generated by the multiple sets of transformers and the capacitor unit, so that the entire circuit works in a soft switching state. In the present invention, because the capacitor unit and the primary windings of the multiple sets of transformers can produce parallel resonance, then, by setting the frequency of the PWM generated by the control chip to match the resonant frequency of the resonant voltage, the entire circuit can work in a soft switching state. Compared with the prior art, since the primary sides of the multiple sets of transformers are all connected in parallel, and a single control chip can be used to build an isolated power supply circuit with multiple outputs, the design cost required for the isolated power supply circuit with multiple outputs can be greatly reduced. Moreover, in the isolated power supply circuit, the output windings of multiple groups of transformers do not need to be wound on the same magnetic core, and multiple small-volume transformers are used to replace the large-volume transformers with multiple windings, thereby significantly reducing the space volume occupied by the multi-channel output isolated power supply circuit. Moreover, the multi-channel output isolated power supply circuit provided by the utility model adopts a soft switching mode to generate the driving voltage, thereby improving the efficiency of the circuit under no-load and full-load conditions, that is, it can also avoid the problem of high no-load loss, and further improve the working efficiency of the multi-channel output isolated power supply circuit. In addition, by setting the transformation ratio of the transformer, the isolated power supply circuit can also achieve the output required by any voltage. Correspondingly, an inverter system provided by the utility model also has the above-mentioned beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 A structural diagram of a multi-output isolated power supply circuit provided by an embodiment of the utility model;

[0025] Figure 2 for Figure 1 A schematic diagram of waveforms of a switch tube and a driving switch tube in the isolated power supply circuit shown;

[0026] Figure 3 This is a structural diagram of another multi-output isolated power supply circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0027] 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 the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0028] See also Figure 1 , Figure 1 A structural diagram of a multi-output isolated power supply circuit provided by an embodiment of the utility model, the isolated power supply circuit comprises:

[0029] Multiple groups of transformers 11 isolated from each other;

[0030] A capacitor unit 12 connected in parallel with the primary windings of the plurality of transformers 11;

[0031] A switch tube 13 connected in series with the capacitor unit 12;

[0032] A control chip 14 is connected to both the capacitor unit 12 and the switch tube 13 and is used to output PWM that matches the resonant frequency generated by the multiple sets of transformers 11 and the capacitor unit 12 so that the entire circuit works in a soft switching state.

[0033] In this embodiment, a multi-channel output isolated power supply circuit is provided, which can not only greatly reduce the design cost required for the multi-channel output isolated power supply circuit, but also reduce the space occupied by the multi-channel output isolated power supply circuit. In addition, the circuit adopts a soft switching mode to generate a driving voltage, which can further improve the working efficiency of the entire circuit.

[0034] In the isolated power supply circuit, multiple sets of transformers 11, capacitor units 12, switch tubes 13 and control chips 14 are provided, wherein the primary sides of the multiple sets of transformers 11 are connected in parallel with capacitor units 12, and the switch tubes 13 are connected in series with the capacitor units 12. During the process of switching on the switch tubes 13, the excitation currents and the currents in the leakage inductances of the multiple sets of transformers 11 cannot be transmitted from the primary sides of the multiple sets of transformers to the secondary sides. After the switch tubes 13 are turned off, this part of the energy will generate parallel resonance on the primary windings of the multiple sets of transformers 11 and the parallel capacitor units 12. The DS voltage of the switch tube 13 reaches the maximum value when this part of the energy is completely transferred to the parallel capacitor units 12 through the primary windings of the multiple sets of transformers 11. During the process of the parallel capacitor units 12 releasing energy to the primary windings of the multiple sets of transformers 11 in reverse, when the voltage of the parallel capacitor units 12 is positive at the top and negative at the bottom and equal to the VCC voltage, the DS voltage of the switch tube 13 reaches 0V. At this moment, a PWM control signal is sent to realize the soft opening of the switch tube.

[0035] See also Figure 2 , Figure 2 for Figure 1 The waveform diagram of the switch tube and the driving switch tube in the isolated power supply circuit is shown. Figure 2 In the figure, the steamed bun wave is the DS waveform of the switch tube 13, and PWM is the waveform output when the control chip 14 drives the switch tube 13. When the voltage across the switch tube 13 is zero, the control chip 14 outputs a high-level signal to the switch tube 13, and when the voltage across the switch tube 13 is greater than zero, the control chip 14 outputs a low-level signal to the switch tube 13. In this case, by adjusting the operating frequency and duty cycle of the PWM output by the control chip 14, and making the operating frequency and duty cycle of the PWM output by the control chip 14 compatible with the resonant frequency generated by the multiple groups of transformers 11 and capacitor units 12, the entire circuit can be operated in a soft switching state. That is, the switch tube 13 operates in a zero-voltage turn-on state, which can reduce the loss of the entire circuit and improve the working efficiency of the circuit.

[0036] It should be noted that in this embodiment, in order to improve the safety and reliability of the multiple sets of transformers 11 during operation, a retaining wall structure or triple insulated wire winding can be used on the primary side of the multiple sets of transformers 11 to improve the insulation level of the multiple sets of transformers 11.

[0037] Obviously, since the primary sides of multiple groups of transformers 11 are all connected in parallel, a single control chip 14 can be used to build a multi-channel output isolation power supply circuit, which can not only greatly reduce the design cost required for the multi-channel output isolation power supply circuit, but also use multiple small-volume transformers to replace multi-winding large-volume transformers to reduce the space occupied. In addition, the isolation power supply circuit uses a soft switching mode to generate the drive voltage, which can further reduce the loss of the isolation power supply circuit. In addition, the use of multiple discrete small-volume transformers to achieve the output of multiple drive voltages can also facilitate the layout of the circuit on a PCB (Printed Circuit Board).

[0038] It can be seen that in the isolated power supply circuit provided in the present embodiment, multiple sets of transformers isolated from each other are provided, capacitor units are connected in parallel with the primary sides of the multiple sets of transformers; the switch tube is connected in series with the capacitor unit, and a control chip is provided which is connected to both the capacitor unit and the switch tube, and is used to output PWM adapted to the resonant frequency generated by the multiple sets of transformers and the capacitor unit, so that the entire circuit works in a soft switching state. In the present embodiment, because the capacitor unit and the primary windings of the multiple sets of transformers can generate parallel resonance, then, by setting the frequency of the PWM generated by the control chip to be adapted to the resonant frequency of the resonant voltage, the entire circuit can be operated in a soft switching state. Compared with the prior art, since the primary sides of the multiple sets of transformers are all connected in parallel, and a single control chip can be used to build a multi-channel output isolated power supply circuit, the design cost required for the multi-channel output isolated power supply circuit can be greatly reduced. In addition, in the isolated power supply circuit, the output windings of the multiple sets of transformers do not need to be wound on the same magnetic core, and multiple small-volume transformers are used to replace the multi-winding large-volume transformer, thereby significantly reducing the space volume occupied by the multi-channel output isolated power supply circuit. Furthermore, the multi-channel output isolation power supply circuit provided in this embodiment adopts a soft switching mode to generate a driving voltage, thereby improving the efficiency of the circuit under no-load and full-load conditions, that is, it can also avoid the problem of high no-load loss, and further improve the working efficiency of the multi-channel output isolation power supply circuit. In addition, by setting the transformation ratio of the transformer, the isolation power supply circuit can also achieve the output required by any voltage.

[0039] Based on the above embodiments, this embodiment further explains and optimizes the technical solution. Figure 3 , Figure 3A structural diagram of a multi-output isolated power supply circuit provided by an embodiment of the utility model. As a preferred embodiment, the above-mentioned isolated power supply circuit also includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first capacitor C1, a second capacitor C2 and a third capacitor C3;

[0040] Among them, the second end of the control chip 14 is connected to the first end of the second resistor R2, the third end of the control chip 14 is connected to the first end of the third resistor R3, the fourth end of the control chip 14 is respectively connected to the second end of the first resistor R1 and the first end of the first capacitor C1, the fifth end of the control chip 14 is connected to the first end of the fifth resistor R5, the sixth end of the control chip 14 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is respectively connected to the control end of the switch tube N and the second end of the fifth resistor R5, the seventh end of the control chip 14 is connected to the power supply, and the eighth end of the control chip 14 is respectively connected to the power supply. The first end of the third capacitor C3 is connected to the second end of the first resistor R1, the first end of the third capacitor C3 is connected to the second end of the second capacitor C2, the first end of the second capacitor C2 is connected to the first end of the capacitor unit C0, the second end of the capacitor unit C0 is connected to the first end of the switch tube N, the second end of the switch tube N is respectively connected to the first end of the sixth resistor R6 and the first end of the seventh resistor R7, the second end of the sixth resistor R6, the second end of the seventh resistor R7, the second end of the third resistor R3, the second end of the second resistor R2, the second end of the first capacitor C1 and the second end of the second capacitor C2 are all grounded.

[0041] In this embodiment, the peripheral circuit of the control chip 14 is specifically described. Figure 3 In FIG. 1 , C0 represents the capacitor unit 12, and N represents the switch tube 13. Figure 3 In the circuit shown, the frequency and duty cycle of the PWM output by the control chip 14 can be adjusted by adjusting the setting values ​​of the first resistor R1 and the first capacitor C1.

[0042] It should be noted that, in this embodiment, the output voltage of the power supply is 12 V. Moreover, in practical applications, the soft start of the entire circuit can be achieved by adjusting the pin voltage of the first terminal COMP of the control chip 14 and controlling the pin voltage of COMP to increase slowly. Under this setting mode, the current spike phenomenon caused by the capacitor unit C0 voltage being zero when the control chip 14 is powered on for the first time can also be reduced.

[0043] Obviously, through the technical solution provided in this embodiment, the PWM output by the control chip can be adapted to the resonant frequency generated by multiple groups of transformers and capacitor units.

[0044] Based on the above embodiments, this embodiment further explains and optimizes the technical solution. Figure 3 , Figure 3 This is a structural diagram of a multi-output isolated power supply circuit provided by an embodiment of the utility model. As a preferred implementation, the switch tube N is specifically an NMOS tube;

[0045] The gate of the NMOS tube is the control end of the switch tube N, the drain of the NMOS tube is the first end of the switch tube N, and the source of the NMOS tube is the second end of the switch tube N.

[0046] Specifically, in practical applications, the switch tube N can be set to an NMOS tube, because the NMOS tube not only has lower power consumption, but also has a high resolution. Therefore, when the switch tube N is set to an NMOS tube, the control efficiency and control accuracy of the isolated power supply circuit can be further improved.

[0047] In addition, it should be noted that the circuit adopts the working principle of a single-tube forward open loop. Therefore, the control chip 14 needs to adjust the PWM on-time so that the energy in the primary excitation inductance of the multiple sets of transformers 11 can be completely transferred to the capacitor unit C0. Then, the energy is reversely stored in the primary inductance of the multiple sets of transformers 11, thereby realizing reverse excitation of the excitation inductance, and thereby ensuring that the multiple sets of transformers 11 will not be saturated due to incomplete discharge of the excitation inductance.

[0048] As a preferred implementation, the above-mentioned isolation power supply circuit further includes: a parasitic diode;

[0049] The anode of the parasitic diode is connected to the source of the NMOS tube, and the cathode of the parasitic diode is connected to the drain of the NMOS tube.

[0050] In this embodiment, a parasitic diode may be provided between the source and the drain of the NMOS tube, and the parasitic diode may be used to prevent the reverse flow of current, thereby avoiding the problem of the reverse current burning the NMOS tube.

[0051] Based on the above embodiments, this embodiment further illustrates and optimizes the technical solution. As a preferred implementation mode, the secondary winding of each transformer in the plurality of transformer groups is provided with a tap.

[0052] In this embodiment, taps can also be set on the secondary windings of each transformer in the multiple groups of transformers 11, and the taps can be grounded. Then, the primary windings and secondary windings of the transformers can be set according to a certain ratio, so that the transformers can output positive and negative voltages of different values.

[0053] See also Figure 3 , Figure 3A structural diagram of a multi-output isolated power supply circuit provided by an embodiment of the utility model. As a preferred embodiment, the above-mentioned isolated power supply circuit also includes: a first diode D1, a second diode D2, an eighth resistor R8, a ninth resistor R9, a fourth capacitor C4 and a fifth capacitor C5;

[0054] Among them, the positive electrode of the first diode D1 is connected to the first end of the secondary side of the target transformer, the negative electrode of the first diode D1 is connected to the first end of the eighth resistor R8, the second end of the eighth resistor R8 is connected to the first end of the fourth capacitor C4, the second end of the fourth capacitor C4 is connected to the tap of the secondary winding of the target transformer, the second end of the secondary winding of the target transformer is connected to the negative electrode of the second diode D2, the positive electrode of the second diode D2 is connected to the first end of the ninth resistor R9, the second end of the ninth resistor R9 is connected to the second end of the fifth capacitor C5, the first end of the fifth capacitor C5 is connected to the second end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded; the target transformer is any one of the multiple groups of transformers.

[0055] In this embodiment, a specific implementation method is provided to enable the target transformer to output positive and negative voltages. That is, in order to enable the target transformer to output positive and negative voltages of different values, the tap of the secondary winding of the target transformer can be grounded, and the value of the secondary winding of the target transformer can be set according to the value of the primary winding of the target transformer, and Figure 3 By connecting the secondary winding of the target transformer in the manner shown, the target transformer can output positive and negative voltages of different values.

[0056] For example, in practical applications, by setting the primary winding and the secondary winding of the target transformer according to the number of windings on the target transformer, the target transformer can output a positive voltage of 12V and a negative voltage of -5V.

[0057] As a preferred implementation, the secondary sides of multiple groups of transformers 11 supply power to a half-bridge, a full-bridge, a three-phase bridge or multiple half-bridges.

[0058] It is understandable that, since both switch tubes in the half-bridge require positive and negative voltages to drive, in practical applications, the multiple sets of transformers 11 in the isolation power supply circuit can be set to two transformers, and two transformers are used to generate two mutually isolated positive and negative voltages. In this setting, the half-bridge can use two independent power supply voltages and ensure the stable operation of the half-bridge. Based on the same principle, in practical applications, the secondary sides of multiple sets of transformers 11 can also be used to power multiple half-bridges.

[0059] Since the full bridge also requires positive and negative voltages to drive, in practical applications, the full bridge can also be connected to the secondary side of multiple sets of transformers, and four transformers in the multiple sets of transformers can be used to generate four mutually isolated positive and negative voltages. In this setting, the two upper bridge arms and the two lower bridge arms in the full bridge can each use an independent power supply voltage, thereby ensuring the stable and reliable operation of the full bridge.

[0060] In addition, since the six switch tubes in the three-phase bridge need to be driven by positive and negative voltages, in actual operation, the multiple sets of transformers 11 in the isolation power supply circuit can also be set to six transformers, and six transformers are used to generate six mutually isolated positive and negative voltages. Obviously, under this setting, the three upper bridge arms and the three lower bridge arms in the three-phase bridge can each use an independent power supply voltage, thereby ensuring the stable operation of the three-phase bridge.

[0061] Obviously, through the technical solution provided in this embodiment, the universality of the multi-output isolated power supply circuit provided in this application in practical applications can be further improved.

[0062] Correspondingly, an embodiment of the utility model further provides an inverter system, including a multi-output isolated power supply circuit as disclosed above.

[0063] An inverter system provided by an embodiment of the utility model has the beneficial effects of the aforementioned multi-output isolated power supply circuit.

[0064] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-channel output isolated power supply circuit, characterized in that: include: Multiple sets of transformers isolated from each other; A capacitor unit connected in parallel with the primary windings of multiple sets of transformers; A switch tube connected in series with the capacitor unit; A control chip connected to both the capacitor unit and the switch tube, used to output PWM adapted to the resonant frequency generated by the multiple sets of transformers and the capacitor unit, so that the entire circuit works in a soft switching state.

2. The multi-output isolated power supply circuit according to claim 1, characterized in that: Also includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a first capacitor, a second capacitor and a third capacitor; Among them, the second end of the control chip is connected to the first end of the second resistor, the third end of the control chip is connected to the first end of the third resistor, the fourth end of the control chip is respectively connected to the second end of the first resistor and the first end of the first capacitor, the fifth end of the control chip is connected to the first end of the fifth resistor, the sixth end of the control chip is connected to the first end of the fourth resistor, the second end of the fourth resistor is respectively connected to the control end of the switch tube and the second end of the fifth resistor, the seventh end of the control chip is connected to the power supply, the eighth end of the control chip is respectively connected to the second end of the third capacitor and the first end of the first resistor, the first end of the third capacitor is connected to the second end of the second capacitor, the first end of the second capacitor is connected to the first end of the capacitor unit, the second end of the capacitor unit is connected to the first end of the switch tube, the second end of the switch tube is respectively connected to the first end of the sixth resistor and the first end of the seventh resistor, the second end of the sixth resistor, the second end of the seventh resistor, the second end of the third resistor, the second end of the second resistor, the second end of the first capacitor and the second end of the second capacitor are all grounded.

3. The multi-output isolated power supply circuit according to claim 1, characterized in that: The switch tube is specifically an NMOS tube; The gate of the NMOS tube is the control end of the switch tube, the drain of the NMOS tube is the first end of the switch tube, and the source of the NMOS tube is the second end of the switch tube.

4. The multi-output isolated power supply circuit according to claim 3, characterized in that: Also includes: Parasitic diode; Wherein, the anode of the parasitic diode is connected to the source of the NMOS tube, and the cathode of the parasitic diode is connected to the drain of the NMOS tube.

5. The multi-output isolated power supply circuit according to claim 1, characterized in that: The primary sides of the multiple transformers are wound with a retaining wall structure or triple insulation wires.

6. A multi-output isolated power supply circuit according to any one of claims 1 to 5, characterized in that: The secondary winding of each transformer in the plurality of transformer groups is provided with a tap.

7. The multi-output isolated power supply circuit according to claim 6, characterized in that: Also includes: A first diode, a second diode, an eighth resistor, a ninth resistor, a fourth capacitor and a fifth capacitor; Among them, the positive electrode of the first diode is connected to the first end of the secondary side of the target transformer, the negative electrode of the first diode is connected to the first end of the eighth resistor, the second end of the eighth resistor is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the tap of the secondary winding of the target transformer, the second end of the secondary winding of the target transformer is connected to the negative electrode of the second diode, the positive electrode of the second diode is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to the second end of the fifth capacitor, the first end of the fifth capacitor is connected to the second end of the fourth capacitor, and the second end of the fourth capacitor is grounded; the target transformer is any one of the multiple groups of transformers.

8. The multi-output isolated power supply circuit according to claim 6, characterized in that: The secondary sides of the multiple groups of transformers supply power to a half-bridge, a full-bridge, a three-phase bridge or multiple half-bridges.

9. An inverter system, characterized in that: The invention comprises a multi-output isolated power supply circuit as claimed in any one of claims 1 to 8.

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