Double-transistor forward circuit output positive and negative voltage cross load device

Abstract

The utility model discloses a double-transistor forward circuit output positive and negative voltage cross load device, and relates to the technical field of switching power supplies. Comprising a switching power supply circuit and a voltage cross-load circuit. According to the utility model, a single-inductor double-wire parallel winding mode is adopted, so that the consistency of magnetic ring materials is ensured, double-wire parallel winding is realized, the consistency of the current trend and the generated magnetic field direction is ensured, the mutual interference is small, and the + / -10% output voltage range of a power supply during cross load can be met; for a multi-path output positive and negative voltage power supply, in order to reduce the inductance coupling interference between the output end follow current inductor and the output end follow current inductor, each path of energy storage inductor originally needing to be independently wound is uniformly wound on the same inductor body, and double-wire parallel winding is carried out, so that the current direction and the magnetic field direction are consistent, the mutual interference is relatively small, and the power supply output voltage is relatively stable; and when a cross load is output, the output voltage range of each path of power supply meets + / -10%.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, and particularly to a dual-switch forward circuit output positive and negative voltage cross-load device. Background Technique

[0002] A switching power supply, also known as a switched-mode power supply or a switching converter, is a type of high-frequency power conversion device and a kind of power supply unit. The function of a switching power supply is to convert a voltage level into the voltage or current required by the user through different forms of architectures; a dual-switch forward switching power supply is a switching power supply that uses two switching tubes to control the power output. In addition to a main switching tube (usually a MOSFET or a BJT), it also includes a synchronous switching tube, and these two switching tubes work together to achieve the switching control of the power supply.

[0003] In the existing technology, for a dual-switch forward power supply with an output of ±75V, the original design was to place energy storage inductors on these two paths respectively, and each energy storage inductor was made separately, resulting in a power output voltage range of 20% when the output cross-loads, and the output voltage range is too large. Content of the Utility Model

[0004] The purpose of the utility model is to provide a dual-switch forward circuit output positive and negative voltage cross-load device to solve the problems raised in the above background technique.

[0005] To solve the above technical problems, the utility model provides the following technical solutions:

[0006] A dual-switch forward circuit output positive and negative voltage cross-load device includes a switching power supply circuit and a voltage cross-load circuit. The output end of the switching power supply circuit is connected to the input end of the voltage cross-load circuit;

[0007] The voltage cross-load circuit includes an energy storage inductor FL1, an energy storage inductor FL2, a high-frequency transformer TR2, and a connector 6P. The energy storage inductor FL1 and the energy storage inductor FL2 are wound on the same inductor body in a double-wire parallel winding form.

[0008] Preferably, the 12 interface of the high-frequency transformer TR2, the 1 interface of the Schottky diode D16, the 3 interface of the Schottky diode D16, the energy storage inductor FL1, the capacitor C13, the capacitor C14, and the 10 interface of the high-frequency transformer TR2 are connected in series in sequence;

[0009] The 9 interface of the high-frequency transformer TR2, the 1 interface of the Schottky diode D20, the 3 interface of the Schottky diode D20, the 2 interface of the Schottky diode D20, and the 7 interface of the high-frequency transformer TR2 are connected in series in sequence;

[0010] The 3 interface of the Schottky diode D20 is electrically connected between the capacitor C14 and the 10 interface of the high-frequency transformer TR2 through the energy storage inductor FL2;

[0011] The connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the +75V terminal, and the connection line between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2 is externally connected to the -75V terminal.

[0012] Preferably, the connection line between the energy storage inductor FL2 and the capacitor C14 is externally connected to the capacitors C37 and C38. The capacitors C37 and C38 are in parallel, and both the capacitors C37 and C38 are respectively electrically connected between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2;

[0013] The connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the capacitors C35, C36 and the resistor R67. The capacitors C35, C36 and the resistor R67 are in parallel. Both the capacitors C35 and C36 are respectively electrically connected between the capacitor C14 and the 10 interface of the high-frequency transformer TR2, and the resistor R67 is grounded through the resistor R65;

[0014] The capacitors C15 and C16 are connected in parallel outside the capacitor C38, and the capacitors C15 and C16 are in series;

[0015] The connection line between the 7 interface of the high-frequency transformer TR2 and the -75V terminal is externally connected to the resistor R68, and the resistor R68 is grounded through the resistor R66.

[0016] Preferably, the connection line between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16 is connected in parallel with the capacitor C34. The connection line between the 10 interface of the high-frequency transformer TR2 and the 2 interface of the Schottky diode D16 is externally connected to the resistors R56, R59 and R60. The resistors R56, R59 and R60 are in parallel, and the resistors R56, R59 and R60 are electrically connected between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16;

[0017] The connection line between the 9 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D20 is externally connected to the capacitor C39, and the capacitor C39 is electrically connected between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2; The connection line between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2 is connected in parallel with the resistors R75, R73 and R84.

[0018] Preferably, the 3 interface of the high-frequency transformer TR2 is externally connected to the OUT1_L terminal, and the 1 interface of the high-frequency transformer TR2 is externally connected to the OUT2_L terminal;

[0019] A resistor R58, a MOS transistor Q7, and a diode D18 are externally connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal, and the resistor R58, the MOS transistor Q7, and the diode D18 are connected in parallel;

[0020] The resistor R58, the diode D10, the resistor R20, and the OUT1_H terminal are connected in series in sequence. The G interface of the MOS transistor Q7 is electrically connected between the resistor R20 and the OUT1_H terminal through a resistor R53. The D interface of the MOS transistor Q7 is externally connected to the +400V terminal. The S interface of the MOS transistor Q7 is electrically connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal. The diode D18 is electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal;

[0021] A resistor R70, a MOS transistor Q9, a diode D13, a resistor R28, a resistor R27, a resistor R26, a resistor R17, a resistor R77, a resistor R78, a resistor R79, and a resistor R80 are externally connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal;

[0022] The resistor R70, the MOS transistor Q9, the diode D13, the resistor R28, the resistor R27, the resistor R26, the resistor R17, the resistor R77, the resistor R78, the resistor R79, and the resistor R80 are connected in parallel, and the resistor R28, the resistor R27, the resistor R26, the resistor R17, the resistor R77, the resistor R78, the resistor R79, and the resistor R80 are grounded;

[0023] The resistor R70, the diode D11, the resistor R18, and the OUT2_H terminal are connected in series in sequence. The G interface of the MOS transistor Q9 is electrically connected between the resistor R18 and the OUT2_H terminal through a resistor R69. The D interface and the S interface of the MOS transistor Q9 are respectively electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal. The diode D13 is electrically connected between the D interface of the MOS transistor Q7 and the +400V terminal.

[0024] Preferably, the switching power supply circuit includes a switching power supply chip U8 and a high-frequency transformer TR3;

[0025] The FB interface of the switching power supply chip U8, the capacitor C51, the capacitor C53, and the CS interface of the switching power supply chip U8 are connected in series in sequence. The OB interface of the switching power supply chip U8, the resistor R100, the resistor R96, the resistor R91, and the +400V terminal are connected in series in sequence. An external capacitor C52 and a resistor R106 are connected between the capacitor C51 and the capacitor C53. The capacitor C52 and the resistor R106 are in parallel, and both the capacitor C52 and the resistor R106 are electrically connected between the OB interface of the switching power supply chip U8 and the resistor R100. The connection line between the capacitor C51 and the capacitor C53 is grounded;

[0026] The VCC interface of the switching power supply chip U8, the 3 interface of the MOS transistor Q13, the 1 interface of the MOS transistor Q13, the resistor R105, and the DRV interface of the switching power supply chip U8 are connected in series in sequence. An external VCC terminal and a capacitor C55 are connected between the VCC interface of the switching power supply chip U8 and the 3 interface of the MOS transistor Q13. The 1 interface of the MOS transistor Q14 is externally connected between the 1 interface of the MOS transistor Q13 and the resistor R105. The 2 interface of the MOS transistor Q14 is connected to the 2 interface of the MOS transistor Q13. The SS interface of the switching power supply chip U8 is externally connected to a capacitor C54, and the capacitor C55, the capacitor C54, and the 3 interface of the MOS transistor Q14 are all grounded respectively.

[0027] Preferably, the 1 interface of the N3 coil of the high-frequency transformer TR3 is electrically connected through a diode D2 between the 2 interface of the MOS transistor Q14 and the 2 interface of the MOS transistor Q13. A diode D4 and a capacitor C50 are connected in parallel outside the diode D2. The diode D4 and the capacitor C50 are in parallel. The capacitor C50 is connected to the 1 interface of the N3 coil of the high-frequency transformer TR3, and the diode D4 is connected to the 4 interface of the N3 coil of the high-frequency transformer TR3. The connection line between the diode D4 and the 4 interface of the N3 coil of the high-frequency transformer TR3 is grounded;

[0028] The 10 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_H terminal, the 9 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_L terminal, the 7 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_H terminal, and the 6 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_L terminal;

[0029] The 9 interface of the N1 coil of the high-frequency transformer TR3 is electrically connected through a resistor R107 between the capacitor C53 and the CS interface of the switching power supply chip U8.

[0030] Compared with the prior art, the beneficial effects achieved by the present utility model are:

[0031] In the present utility model, a single inductor is wound with two wires in parallel to ensure the consistency of the magnetic ring material. The two-wire parallel winding ensures that the current direction and the magnetic field direction generated thereby are the same, with less interference between each other, and can meet the output voltage range of + / - 10% of the power supply under cross-load; for the multi-output positive and negative voltage power supply, in order to reduce the inductive coupling interference between the freewheeling inductors at each output terminal during their operation, the energy storage inductors that originally needed to be independently wound for each path are now uniformly wound on the same inductor body with two wires in parallel, so that the current direction and the magnetic field direction are the same, with less mutual interference, and the power supply output voltage is relatively stable, and can meet the requirements that the output voltage ranges of each path of power supply meet + / - 10% when there is cross-load at the output. Description of the Drawings

[0032] The drawings are used to provide a further understanding of the present utility model, and constitute a part of the specification. Together with the embodiments of the present utility model, they are used to explain the present utility model, but do not constitute a limitation to the present utility model. In the drawings:

[0033] Figure 1 is a winding schematic diagram of the energy storage inductor in the present utility model;

[0034] Figure 2 is a circuit schematic diagram of the switching power supply circuit in the present utility model;

[0035] Figure 3 is a circuit schematic diagram of the voltage cross-load circuit in the present utility model. Detailed Embodiment

[0036] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0037] Refer to Figures 1 - 3 , the present utility model provides a technical solution: a dual-switch forward circuit output positive and negative voltage cross-load device, including a switching power supply circuit and a voltage cross-load circuit. The output end of the switching power supply circuit is connected to the input end of the voltage cross-load circuit; the voltage cross-load circuit includes an energy storage inductor FL1, an energy storage inductor FL2, a high-frequency transformer TR2, and a connector 6P. The energy storage inductor FL1 and the energy storage inductor FL2 are wound on the same inductor body in a form of two-wire parallel winding.

[0038] The 12 interface of the high-frequency transformer TR2, the 1 interface of the Schottky diode D16, the 3 interface of the Schottky diode D16, the energy storage inductor FL1, the capacitor C13, the capacitor C14, and the 10 interface of the high-frequency transformer TR2 are connected in series in sequence; the 9 interface of the high-frequency transformer TR2, the 1 interface of the Schottky diode D20, the 3 interface of the Schottky diode D20, the 2 interface of the Schottky diode D20, and the 7 interface of the high-frequency transformer TR2 are connected in series in sequence; the 3 interface of the Schottky diode D20 is electrically connected between the capacitor C14 and the 10 interface of the high-frequency transformer TR2 through the energy storage inductor FL2; the connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the +75V terminal, and the connection line between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2 is externally connected to the -75V terminal.

[0039] The connection line between the energy storage inductor FL2 and the capacitor C14 is externally connected to the capacitors C37 and C38, the capacitors C37 and C38 are connected in parallel, and the capacitors C37 and C38 are respectively and electrically connected between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2; the connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the capacitors C35, C36, and the resistor R67, the capacitors C35, C36, and the resistor R67 are connected in parallel, the capacitors C35 and C36 are respectively and electrically connected between the capacitor C14 and the 10 interface of the high-frequency transformer TR2, and the resistor R67 is grounded through the resistor R65; the capacitors C15 and C16 are connected in parallel outside the capacitor C38, and the capacitors C15 and C16 are connected in series; the connection line between the 7 interface of the high-frequency transformer TR2 and the -75V terminal is externally connected to the resistor R68, and the resistor R68 is grounded through the resistor R66.

[0040] The connection line between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16 is connected in parallel with the capacitor C34, the connection line between the 10 interface of the high-frequency transformer TR2 and the 2 interface of the Schottky diode D16 is externally connected to the resistors R56, R59, and R60, the resistors R56, R59, and R60 are connected in parallel, and the resistors R56, R59, and R60 are electrically connected between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16; the connection line between the 9 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D20 is externally connected to the capacitor C39, and the capacitor C39 is electrically connected between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2; the connection line between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2 is connected in parallel with the resistors R75, R73, and R84.

[0041] The 3 interface of the high-frequency transformer TR2 is externally connected to the OUT1_L terminal, and the 1 interface of the high-frequency transformer TR2 is externally connected to the OUT2_L terminal; a resistor R58, a MOS transistor Q7, and a diode D18 are externally connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal, and the resistor R58, the MOS transistor Q7, and the diode D18 are connected in parallel; the resistor R58, the diode D10, the resistor R20, and the OUT1_H terminal are connected in series in sequence, the G interface of the MOS transistor Q7 is electrically connected between the resistor R20 and the OUT1_H terminal through the resistor R53, the D interface of the MOS transistor Q7 is externally connected to the +400V terminal, the S interface of the MOS transistor Q7 is electrically connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal, and the diode D18 is electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal; a resistor R70, a MOS transistor Q9, a diode D13, a resistor R28, a resistor R27, a resistor R26, a resistor R17, a resistor R77, a resistor R78, a resistor R79, and a resistor R80 are externally connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal; the resistor R70, the MOS transistor Q9, the diode D13, the resistor R28, the resistor R27, the resistor R26, the resistor R17, the resistor R77, the resistor R78, the resistor R79, and the resistor R80 are connected in parallel, and the resistor R28, the resistor R27, the resistor R26, the resistor R17, the resistor R77, the resistor R78, the resistor R79, and the resistor R80 are grounded; the resistor R70, the diode D11, the resistor R18, and the OUT2_H terminal are connected in series in sequence, the G interface of the MOS transistor Q9 is electrically connected between the resistor R18 and the OUT2_H terminal through the resistor R69, the D interface and the S interface of the MOS transistor Q9 are respectively electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal, and the diode D13 is electrically connected between the D interface of the MOS transistor Q7 and the +400V terminal.

[0042] The switching power supply circuit includes a switching power supply chip U8 and a high-frequency transformer TR3; the FB interface of the switching power supply chip U8, capacitor C51, capacitor C53, and the CS interface of the switching power supply chip U8 are connected in series in sequence. The OB interface of the switching power supply chip U8, resistor R100, resistor R96, resistor R91, and the +400V terminal are connected in series in sequence. An external capacitor C52 and resistor R106 are connected between capacitor C51 and capacitor C53. Capacitor C52 and resistor R106 are in parallel, and both capacitor C52 and resistor R106 are electrically connected between the OB interface of the switching power supply chip U8 and resistor R100. The connection line between capacitor C51 and capacitor C53 is grounded; the VCC interface of the switching power supply chip U8, the 3 interface of MOS transistor Q13, the 1 interface of MOS transistor Q13, resistor R105, and the DRV interface of the switching power supply chip U8 are connected in series in sequence. An external VCC terminal and capacitor C55 are connected between the VCC interface of the switching power supply chip U8 and the 3 interface of MOS transistor Q13. The 1 interface of MOS transistor Q14 is externally connected between the 1 interface of MOS transistor Q13 and resistor R105. The 2 interface of MOS transistor Q14 is connected to the 2 interface of MOS transistor Q13. The SS interface of the switching power supply chip U8 is externally connected to capacitor C54. Capacitor C55, capacitor C54, and the 3 interface of MOS transistor Q14 are all grounded respectively.

[0043] The 1 interface of the N3 coil of the high-frequency transformer TR3 is electrically connected through diode D2 between the 2 interface of MOS transistor Q14 and the 2 interface of MOS transistor Q13. Diode D4 and capacitor C50 are connected in parallel outside diode D2. Diode D4 and capacitor C50 are in parallel. Capacitor C50 is connected to the 1 interface of the N3 coil of the high-frequency transformer TR3. Diode D4 is connected to the 4 interface of the N3 coil of the high-frequency transformer TR3. The connection line between diode D4 and the 4 interface of the N3 coil of the high-frequency transformer TR3 is grounded; the 10 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_H terminal. The 9 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_L terminal. The 7 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_H terminal. The 6 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_L terminal; the 9 interface of the N1 coil of the high-frequency transformer TR3 is electrically connected through resistor R107 between capacitor C53 and the CS interface of the switching power supply chip U8.

[0044] Specific working principle:

[0045] The dual-switch forward power supply has dual-channel (±75V) output with a voltage of ±75V / 6.7A. When there is a cross-load, the output voltage range is too large. This is because for the energy storage inductors (flyback inductors) at the ±75V output terminals, when they work, the magnitudes of the currents passing through them are inconsistent, and the magnetic fields generated around the inductors, if placed separately for each channel, will cause significant interference between them. The problem to be solved in this case is to reduce such mutual interference, and the two-channel outputs share a single energy storage inductor;

[0046] To reduce the mutual interference between the two energy storage inductors (flyback inductors) at the output terminals of the dual-switch forward, the characteristics of the inductor are the key to solving the problem. The method of using a single inductor with double-wire parallel winding is adopted to ensure that the magnetic core materials are the same and the double-wire parallel winding ensures that the current directions and the magnetic field directions generated thereby are the same, with relatively small mutual interference, and it can meet the output voltage range of + / -10% of the power supply under cross-load; for the multi-channel output positive and negative voltage power supply, in order to reduce the inductive coupling interference between the flyback inductors at each output terminal during their operation, the energy storage inductors that originally needed to be independently wound for each channel are now uniformly wound on the same inductor body with double-wire parallel winding, so that the current directions and the magnetic field directions are the same, and the mutual interference is relatively small;

[0047] For the multi-channel output positive and negative voltage power supply, in order to reduce the inductive coupling interference between the flyback inductors at each output terminal during their operation, the energy storage inductors that originally needed to be independently wound for each channel are now uniformly wound on the same inductor body with double-wire parallel winding, so that the current directions and the magnetic field directions are the same, and the mutual interference is relatively small. The output voltage of the power supply is relatively stable and can meet the requirement that the output voltage range of each power supply is + / -10% under cross-load; when each channel is wound independently, it can only meet the output voltage range of + / -20%.

[0048] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-tube forward circuit outputs positive and negative voltage cross-load device, comprising a switching power supply circuit and a voltage cross-load circuit, characterized in that: The output end of the switching power supply circuit is connected to the input end of the voltage cross load circuit; The voltage cross load circuit includes an energy storage inductor FL1, an energy storage inductor FL2, a high-frequency transformer TR2 and a connector 6P. The energy storage inductor FL1 and the energy storage inductor FL2 are wound on the same inductor body in a bilinear parallel winding form.

2. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 1, characterized in that: The interface 12 of the high-frequency transformer TR2, the interface 1 of the Schottky diode D16, the interface 3 of the Schottky diode D16, the energy storage inductor FL1, the capacitor C13, the capacitor C14 and the interface 10 of the high-frequency transformer TR2 are connected in series in sequence; The interface 9 of the high-frequency transformer TR2, the interface 1 of the Schottky diode D20, the interface 3 of the Schottky diode D20, the interface 2 of the Schottky diode D20 and the interface 7 of the high-frequency transformer TR2 are connected in series in sequence; Interface 3 of the Schottky diode D20 is electrically connected between the capacitor C14 and interface 10 of the high-frequency transformer TR2 through the energy storage inductor FL2; The connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the +75V terminal, and the connection line between the 2 interface of the Schottky diode D20 and the 7 interface of the high-frequency transformer TR2 is externally connected to the -75V terminal.

3. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 2, characterized in that: The connection line between the energy storage inductor FL2 and the capacitor C14 is externally connected to the capacitor C37 and the capacitor C38, the capacitor C37 and the capacitor C38 are connected in parallel, and the capacitor C37 and the capacitor C38 are electrically connected between the interface 2 of the Schottky diode D20 and the interface 7 of the high-frequency transformer TR2 respectively; The connection line between the energy storage inductor FL1 and the capacitor C13 is externally connected to the capacitor C35, the capacitor C36 and the resistor R67. The capacitor C35, the capacitor C36 and the resistor R67 are connected in parallel. The capacitor C35 and the capacitor C36 are electrically connected between the capacitor C14 and the 10 interface of the high-frequency transformer TR2, respectively. The resistor R67 is grounded through the resistor R65. The capacitor C15 and the capacitor C16 are connected in parallel to the outside of the capacitor C38, and the capacitor C15 and the capacitor C16 are connected in series; The connection line between the 7 interface and the -75V terminal of the high-frequency transformer TR2 is externally connected to a resistor R68, and the resistor R68 is grounded through a resistor R66.

4. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 3, characterized in that: The connection between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16 is connected in parallel with a capacitor C34, and the connection between the 10 interface of the high-frequency transformer TR2 and the 2 interface of the Schottky diode D16 is externally connected with a resistor R56, a resistor R59 and a resistor R60, and the resistor R56, the resistor R59 and the resistor R60 are connected in parallel, and the resistor R56, the resistor R59 and the resistor R60 are electrically connected between the 12 interface of the high-frequency transformer TR2 and the 1 interface of the Schottky diode D16; The connection between interface 9 of the high-frequency transformer TR2 and interface 1 of the Schottky diode D20 is connected to an external capacitor C39, and the capacitor C39 is electrically connected between interface 2 of the Schottky diode D20 and interface 7 of the high-frequency transformer TR2; the connection between interface 2 of the Schottky diode D20 and interface 7 of the high-frequency transformer TR2 is connected in parallel with resistors R75, R73 and R84.

5. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 4, characterized in that: The 3 interface of the high-frequency transformer TR2 is externally connected to the OUT1_L terminal, and the 1 interface of the high-frequency transformer TR2 is externally connected to the OUT2_L terminal; An external resistor R58, a MOS tube Q7 and a diode D18 are connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal, and the resistor R58, the MOS tube Q7 and the diode D18 are connected in parallel; The resistor R58, the diode D10, the resistor R20 and the OUT1_H terminal are connected in series in sequence, the G interface of the MOS tube Q7 is electrically connected between the resistor R20 and the OUT1_H terminal through the resistor R53, the D interface of the MOS tube Q7 is externally connected to the +400V terminal, the S interface of the MOS tube Q7 is electrically connected between the 3 interface of the high-frequency transformer TR2 and the OUT1_L terminal, and the diode D18 is electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal; An external resistor R70, a MOS tube Q9, a diode D13, a resistor R28, a resistor R27, a resistor R26, a resistor R17, a resistor R77, a resistor R78, a resistor R79 and a resistor R80 are connected between the 1 interface and the OUT2_L end of the high-frequency transformer TR2; The resistor R70, MOS tube Q9, diode D13, resistor R28, resistor R27, resistor R26, resistor R17, resistor R77, resistor R78, resistor R79 and resistor R80 are connected in parallel, and the resistor R28, resistor R27, resistor R26, resistor R17, resistor R77, resistor R78, resistor R79 and resistor R80 are grounded. The resistor R70, the diode D11, the resistor R18 and the OUT2_H terminal are connected in series in sequence, the G interface of the MOS tube Q9 is electrically connected between the resistor R18 and the OUT2_H terminal through the resistor R69, the D interface and the S interface of the MOS tube Q9 are electrically connected between the 1 interface of the high-frequency transformer TR2 and the OUT2_L terminal, respectively, and the diode D13 is electrically connected between the D interface of the MOS tube Q7 and the +400V terminal.

6. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 5, characterized in that: The switching power supply circuit includes a switching power supply chip U8 and a high-frequency transformer TR3; The FB interface of the switching power chip U8, the capacitor C51, the capacitor C53 and the CS interface of the switching power chip U8 are connected in series in sequence, the OB interface of the switching power chip U8, the resistor R100, the resistor R96, the resistor R91 and the +400V end are connected in series in sequence, the capacitor C51 and the capacitor C53 are externally connected with a capacitor C52 and a resistor R106, the capacitor C52 and the resistor R106 are connected in parallel, the capacitor C52 and the resistor R106 are electrically connected between the OB interface of the switching power chip U8 and the resistor R100, and the connection between the capacitor C51 and the capacitor C53 is grounded; The VCC interface of the switching power chip U8, the 3 interface of the MOS tube Q13, the 1 interface of the MOS tube Q13, the resistor R105 and the DRV interface of the switching power chip U8 are connected in series in sequence; the VCC interface of the switching power chip U8 and the 3 interface of the MOS tube Q13 are externally connected to the VCC end and the capacitor C55, the 1 interface of the MOS tube Q14 is externally connected between the 1 interface of the MOS tube Q13 and the resistor R105, the 2 interface of the MOS tube Q14 is connected to the 2 interface of the MOS tube Q13, the SS interface of the switching power chip U8 is externally connected to the capacitor C54, and the capacitor C55, the capacitor C54 and the 3 interface of the MOS tube Q14 are grounded respectively.

7. A dual-transistor forward circuit outputting positive and negative voltage cross-load device according to claim 6, characterized in that: Interface 1 of the N3 coil of the high-frequency transformer TR3 is electrically connected between interface 2 of the MOS tube Q14 and interface 2 of the MOS tube Q13 through a diode D2, a diode D4 and a capacitor C50 are connected in parallel to the outside of the diode D2, the diode D4 and the capacitor C50 are connected in parallel, the capacitor C50 is connected to interface 1 of the N3 coil of the high-frequency transformer TR3, the diode D4 is connected to interface 4 of the N3 coil of the high-frequency transformer TR3, and the connection between the diode D4 and interface 4 of the N3 coil of the high-frequency transformer TR3 is grounded; The 10 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_H terminal, the 9 interface of the N1 coil of the high-frequency transformer TR3 is externally connected to the OUT2_L terminal, the 7 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_H terminal, and the 6 interface of the N2 coil of the high-frequency transformer TR3 is externally connected to the OUT1_L terminal; The 9 interface of the N1 coil of the high-frequency transformer TR3 is electrically connected between the capacitor C53 and the CS interface of the switching power supply chip U8 through the resistor R107.

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