High-reliability isolation power supply circuit

Abstract

The high-reliability isolation power supply circuit comprises a transformer, a primary side circuit and a secondary side circuit, wherein the primary side circuit and the secondary side circuit are arranged on the two sides of the transformer; the primary side circuit comprises a voltage stabilizing circuit and a self-excitation switching circuit, the self-excitation switching circuit comprises switching tubes Q2 and Q4, and the transformer comprises primary side windings N1 and N2, a feedback winding N5 and secondary side windings N3 and N4; the output end of the voltage stabilizing circuit is connected with a primary side center tap, the dotted terminal of a primary side winding N1 is connected with the collector electrode or the drain electrode of a switching tube Q2, and the synonym terminal of a primary side winding N2 is connected with the collector electrode or the drain electrode of a switching tube Q4; the two ends of the feedback winding N5 are connected with the control ends of the switching tubes Q2 and Q4 respectively, and the polarities of the two ends of the feedback winding N5 are turned over along with the primary winding so as to control one and only one of the switching tubes Q2 and Q4 to be switched on at the same time. The secondary power supply circuit can provide low voltage ripples for a system, obtains a good load regulation rate, abandons the use of a main control chip, reduces the cost of circuit components, and achieves the high-precision and high-reliability operation of the secondary power supply circuit at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic circuits, and in particular relates to a highly reliable isolated power supply circuit. Background Art

[0002] Against the backdrop of today's rapid advancements in space technology, the performance and reliability of satellite power systems are becoming increasingly critical. Satellite power systems (spacecraft power systems) are core subsystems of spacecraft, including satellites, space stations, and deep space probes. They are responsible for providing a continuous, stable, and reliable power supply to all payloads and equipment. Due to the unique characteristics of the space environment (such as extreme temperatures, vacuum, and radiation), satellite power systems must possess high reliability, long life, and lightweight characteristics.

[0003] The primary and secondary power supplies are two core components of a spacecraft's power supply system, working together to ensure stable power supply throughout the spacecraft's mission cycle. The primary power supply directly obtains and converts energy from the external environment. Energy sources include solar energy, nuclear energy, and other sources. It is the spacecraft's main power supply, providing continuous power during periods of illumination or long-term missions. It is typically unregulated direct current and requires a secondary power supply. The secondary power supply is a system that stores electrical energy for regulation and backup. It stabilizes, converts, or isolates the output of the primary power supply before providing power to the load equipment.

[0004] To effectively enhance product safety and stability, many satellite power systems typically utilize an isolated secondary power supply circuit to power the system chip. The single-ended flyback topology, due to its relatively simple structure and low cost, has become a popular choice. However, this topology has significant drawbacks. It utilizes a storage-before-transfer energy conversion method, which inevitably results in high circuit ripple. In practice, to optimize power quality, an LDO (low-dropout linear regulator) circuit must be added to the downstream stage. This inevitably increases system costs, contradicting the goal of low cost and significantly limiting the product's market competitiveness and widespread adoption. Furthermore, the voltage regulation technology employed in this circuit primarily utilizes pulse-width modulation, which requires a dedicated, radiation-resistant master control chip for precise control. However, due to limitations in process materials, such chips struggle to achieve high reliability in radiation environments. Satellite products place extremely complex power supply requirements, encompassing diverse voltage levels, stringent accuracy requirements, and varying power supply types. This requires the development of specific high-reliability, high-precision secondary power supplies to meet the requirements of spacecraft such as electronic reconnaissance subsystems.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a highly reliable isolated power supply circuit that utilizes a self-excited push-pull circuit structure to provide the system with lower voltage ripple. The transformers in this circuit structure operate in an interleaved manner, enabling the circuit to achieve better load regulation and reducing the need for output filter capacitors. The self-excited control method eliminates the need for a main control chip in the secondary power supply circuit, requiring only reinforced diodes and tertiary diodes to achieve radiation resistance. This reduces the cost of circuit components while achieving high-precision, highly reliable operation of the secondary power supply circuit.

[0007] The technical solution adopted in the present invention is:

[0008] The present application discloses a highly reliable isolated power supply circuit, which includes a transformer and a primary circuit and a secondary circuit located on both sides of the transformer; the primary circuit includes a voltage stabilizing circuit and a self-excited switching circuit, the self-excited switching circuit includes switching tubes Q2 and Q4, the transformer includes primary windings N1 and N2 located on both sides of the primary center tap, secondary windings N3 and N4 located on both sides of the secondary center tap, and a feedback winding N5 located on the primary side; the output end of the voltage stabilizing circuit is connected to the primary center tap, the same-name end of the primary winding N1 is connected to the collector or drain of the switching tube Q2, and the opposite-name end of the primary winding N2 is connected to the collector or drain of the switching tube Q4; the two ends of the feedback winding N5 are respectively connected to the control ends of the switching tubes Q2 and Q4. When the polarity of the primary winding is reversed, the polarity of the two ends of the feedback winding N5 is reversed accordingly, so as to control the switching tubes Q2 and Q4 to have only one tube turned on at the same time.

[0009] As an optional technical solution, the self-excited switching circuit further includes resistors R2, R3, R6, R7, R10, voltage-stabilizing tubes D3, D4, and capacitors C8, C9, and C11; one end of each of the resistors R2 and R3 is connected to the output end of the voltage-stabilizing circuit, and the other end is connected to the control end of the switch tubes Q2 and Q4, respectively; one end of the voltage-stabilizing tube D3 is connected to the control end of the switch tube Q2, and the other end is connected to the emitter or source of the switch tube Q2; one end of the voltage-stabilizing tube D4 is connected to the switch The control terminal of the gate tube Q4 is connected to the gate tube Q4, and the other end is connected to the emitter or source of the switch tube Q4. The emitters or sources of the switch tubes Q2 and Q4 are both grounded. The branch formed by resistors R6, R10, capacitors C8, and C11 is connected between the same-name terminal of the primary winding N1 and the opposite-name terminal of the primary winding N2, among which resistors R6 and R10 are connected in parallel and then connected in series with capacitors C11 and C8. Resistor R7 and capacitor C9 are connected in series between the opposite-name terminal of the feedback winding N5 and the control terminal of the switch tube Q2.

[0010] As an optional technical solution, the primary circuit further includes a first filtering circuit, which includes an inductor L1, capacitors C1, C4, C7, C10 and an inductor L3 connected in series between the input voltage and the input ground.

[0011] As an optional technical solution, the voltage stabilizing circuit includes transistors Q1, Q3, resistors R1, R4, R9, capacitors C2, C3 and a voltage stabilizing diode D2; wherein, the resistors R1, R4, and R9 are connected in series between the inductor L1 and the GND ground, the emitter and collector of the transistor Q1 are respectively connected to the two ends of the resistor R1, the base of the transistor Q1 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the connection point of R4 and R9, the emitter of the transistor Q3 is connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the GND ground, and the two ends of the voltage stabilizing diode D2 are respectively connected to the collector of the transistor Q1 and the emitter of the transistor Q3; the capacitors C2 and C3 are connected in parallel between the collector of the transistor Q1 and the GND ground.

[0012] As an optional technical solution, the secondary circuit includes a rectifier circuit and a second filter circuit, the rectifier circuit includes rectifier diodes D1 and D5, and the second filter circuit includes inductors L2 and L4 and capacitors C5 and C6; wherein, the anodes of the rectifier diodes D1 and D5 are respectively connected to the like-name end of the secondary winding N3 and the opposite-name end of the secondary winding N4, and the cathodes of the rectifier diodes D1 and D5 are connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the signal ground SGND; one end of the inductor L4 is connected to the connection point between the inductor L2 and the capacitor C5, and the other end is connected to one end of the capacitor C6, and the other end of the capacitor C6 is connected to the signal ground SGND; the secondary center tap is connected to the signal ground SGND.

[0013] As an optional technical solution, the rectifier diodes D1 and D5 in the rectifier circuit are replaced by rectifier MOS tubes Q5 and Q6 respectively.

[0014] As an optional technical solution, the switch tubes Q2 and Q4 are both bipolar transistors or field effect transistors.

[0015] The beneficial effects of the present invention are as follows: To address the large output voltage ripple problem of existing satellite power supplies, this application employs a push-pull circuit structure. The two sets of drive pulses for the switching tube are 180° out of phase, the two sets of transformer windings N1 and N2 operate in an interleaved manner, and the rectification frequency is twice the operating frequency, thereby reducing the output voltage ripple. Furthermore, to address the low reliability of the main control chip in the satellite secondary power isolation circuit, a self-excited switching circuit is employed. This circuit can operate without a main control chip, and radiation resistance can be achieved by simply reinforcing the diodes and tertiary diodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a circuit block diagram of a high-reliability isolated power supply circuit in an exemplary embodiment.

[0017] Figure 2 FIG. 1 is a circuit diagram of a high-reliability isolated power supply circuit in an exemplary embodiment.

[0018] Figure 3 It is a schematic diagram of the current flow when the switch tube Q2 is turned on.

[0019] Figure 4 This is a schematic diagram of the current flow when the switch tube Q4 is turned on.

[0020] Figure 5 FIG. 4 is a circuit diagram of a high-reliability isolated power supply circuit in another exemplary embodiment.

[0021] Figure 6 is a synchronous rectification driving circuit in another exemplary embodiment. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1

[0025] like Figure 1As shown, this embodiment discloses a highly reliable isolated power supply circuit, the power supply circuit includes a transformer 40, a primary circuit located on the primary side of the transformer 40, and a secondary circuit located on the secondary side of the transformer 40; the primary circuit includes a voltage stabilizing circuit 20 and a self-excited switching circuit 30, the self-excited switching circuit 30 includes switching tubes Q2 and Q4, the transformer 40 includes primary windings N1 and N2 located on both sides of the primary center tap, and secondary windings N3 and N4 located on both sides of the secondary center tap. 4 and a feedback winding N5 on the primary side; the output end of the voltage stabilizing circuit 20 is connected to the primary center tap, the same-name end of the primary winding N1 is connected to the collector of the switching tube Q2, and the opposite-name end of the primary winding N2 is connected to the collector of the switching tube Q4; the two ends of the feedback winding N5 are respectively connected to the control ends of the switching tubes Q2 and Q4. When the polarity of the primary winding is reversed, the polarity of the two ends of the feedback winding N5 is reversed accordingly, so as to control the switching tubes Q2 and Q4 to have only one tube turned on at the same time.

[0026] As an optional implementation, Figure 2 As shown, the self-excited switching circuit 30 also includes resistors R2, R3, R6, R7, R10, voltage-stabilizing diodes D3, D4, and capacitors C8, C9, and C11; one end of each resistor R2 and R3 is connected to the output end of the voltage-stabilizing circuit, and the other end is connected to the control end of the switching transistors Q2 and Q4, respectively; one end of the voltage-stabilizing diode D3 is connected to the control end of the switching transistor Q2, and the other end is connected to the emitter of the switching transistor Q2; one end of the voltage-stabilizing diode D4 is connected to the control end of the switching transistor Q4, and the other end is connected to the emitter of the switching transistors Q4; the emitters of the switching transistors Q2 and Q4 are both grounded; a branch formed by resistors R6, R10, and capacitors C8 and C11 is connected between the same-name terminal of the primary winding N1 and the opposite-name terminal of the primary winding N2, wherein resistors R6 and R10 are connected in parallel and then connected in series with capacitors C11 and C8; resistor R7 and capacitor C9 are connected in series between the opposite-name terminal of the feedback winding N5 and the control end of the switching transistor Q2.

[0027] As an optional implementation, the primary circuit further includes a first filter circuit 10, which includes an inductor L1, capacitors C1, C4, C7, C10, and an inductor L3 connected in series between the input voltage and the input ground.

[0028] As an optional embodiment, the voltage stabilizing circuit 20 includes transistors Q1, Q3, resistors R1, R4, R9, capacitors C2, C3 and a voltage stabilizing diode D2; wherein, the resistors R1, R4, and R9 are connected in series between the inductor L1 and the GND ground, the emitter and collector of the transistor Q1 are respectively connected to the two ends of the resistor R1, the base of the transistor Q1 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the connection point of R4 and R9, the emitter of the transistor Q3 is connected to one end of the resistor R8, and the other end of the resistor R8 is connected to the GND ground, and the two ends of the voltage stabilizing diode D2 are respectively connected to the collector of the transistor Q1 and the emitter of the transistor Q3; the capacitors C2 and C3 are connected in parallel between the collector of the transistor Q1 and the GND ground.

[0029] As an optional embodiment, the secondary circuit includes a rectifier circuit 50 and a second filter circuit 60, the rectifier circuit 50 includes rectifier diodes D1 and D5, and the second filter circuit 60 includes inductors L2 and L4 and capacitors C5 and C6; wherein, the anodes of the rectifier diodes D1 and D5 are respectively connected to the same-name end of the secondary winding N3 and the opposite-name end of the secondary winding N4, and the cathodes of the rectifier diodes D1 and D5 are connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the signal ground SGND; one end of the inductor L4 is connected to the connection point between the inductor L2 and the capacitor C5, and the other end is connected to one end of the capacitor C6, and the other end of the capacitor C6 is connected to the signal ground SGND; the secondary center tap is connected to the signal ground SGND.

[0030] In this embodiment, the switch tubes Q2 and Q4 are both bipolar transistors.

[0031] In order to better understand this embodiment, the working principle of the circuit of this embodiment is further analyzed below.

[0032] Since the switches Q2 and Q4 cannot be completely symmetrical in actual production, when the power supply voltage is turned on, one of the transistors will obtain a forward bias through the start-up resistor (R2 or R3), and then the collector current will begin to flow. Assuming that the transistor Q2 is turned on first, at the moment of conduction, the unmarked end of the primary winding N1 (i.e., the opposite end, such as Figure 1 The end without "·" in the figure is at a positive potential, and the end with the same name (i.e., the end with the same number) of the feedback winding N5 is at a positive potential. Figure 1 The end with "·" in the middle) is at a negative potential, which forces the base potential of the switch tube Q4 to be negative. At the same time, its emitter is grounded, which further deepens the cutoff degree of the switch tube Q4. At this time, the current flow direction can be referred to Figure 3 The arrows in the figure indicate the direction of current flow, and Q4 and D1 marked with “×” indicate that they are cut off.

[0033] Due to the inherent limitations of the base current and amplification factor of the transistor, the collector current will enter a saturation state after a certain period of time. At this time, the inductive polarity of the transformer winding is reversed, the labeled end of the primary winding N1 becomes a positive potential, and the labeled end of the feedback winding N5 is also a positive potential, which causes the transistor Q4 to turn on and Q2 to turn off. The current direction at this time is as follows Figure 4 As shown in the figure, the arrows indicate the direction of current flow, and the "×" Q2 and D5 indicate that they are cut off. The operating frequency of this circuit is determined by the number of turns of the feedback winding N5, as well as the resistor R7 and capacitor C9.

[0034] This circuit uses an alternating operating mode with a 180° phase shift, thus forming a complete operating cycle. In this mode, the voltage-stabilizing capacitors C2 and C3 do not first store charge and then discharge it. Instead, they operate in an interleaved two-phase power supply circuit, effectively reducing voltage ripple. To further meet the stringent requirements for reducing output ripple, the output stage uses a two-stage filter consisting of L2, C5, L4, and C6. The filter circuit transfer function is:

[0035] G(s)=1 / (L2L4C5C6S 4 +L2C5S 3 +L4C6S 2 +1)

[0036] Where S is the complex frequency, S=jω, j is the imaginary unit, and ω is the angular frequency.

[0037] In order to meet the voltage regulation requirement (voltage regulation is a measure of the ability of a power supply to maintain a stable output voltage when the input voltage changes), a buck circuit needs to be added at the input end to stabilize the input voltage. Figure 2 As shown, the voltage stabilizing circuit 20 includes resistors R1, R4, R8, R9, transistors Q1, Q3, a voltage stabilizing diode D2, and capacitors C2, C3. During design, the minimum value of the input voltage is set as the voltage stabilizing value. Its working principle is as follows: When the circuit is running, the input voltage is divided by the resistors R1, R4, and R9, so that the voltage at point N is higher than the voltage at point M. The transistor Q3 is then turned on, and at the same time, the transistor Q1 is also turned on, and the current flows through Q1. At this time, the output voltage value is equal to the sum of the voltage stabilizing value of the voltage stabilizing diode D2 and the potential at point M. The voltage stabilization process depends on the voltage difference between point N and point M (that is, the voltage drop u between the base and emitter of Q3). BE ), to change the output current of transistor Q3, so as to achieve the purpose of output voltage regulation. The specific process is as follows: R1, R4, and R9 are connected in series to divide the voltage. When the input voltage increases, the voltage drop on R9 increases, that is, the potential of point N increases, that is, the voltage drop u between the base and emitter of Q3 BEIncrease, resulting in an increase in the base current of Q3, which in turn increases the collector current of Q3, that is, the base current of Q1 increases, which in turn increases the collector current of Q1, and then increases the current flowing through R4, that is, the voltage drop on R4 increases, and the voltage drop on R4 is proportional to u BE The sum is a constant value, equal to the voltage drop on the Zener diode D2, so u BE The voltage drop across R8 is constant, and the sum of the voltage drop across R8 and the voltage drop across the voltage regulator D2 can be regarded as the output voltage of the voltage regulator circuit 20. Therefore, the output voltage of the voltage regulator circuit 20 tends to be constant.

[0038] In summary, this embodiment effectively addresses two key challenges facing isolated secondary power supplies for satellite applications: large output voltage ripple and poor main control chip stability. In terms of circuit architecture design, this embodiment employs a self-excited push-pull architecture. The two sets of drive pulses for switches Q2 and Q4 are 180° out of phase, enabling alternating operation of the rectifier circuit. Combined with optimized charging and discharging processes for stabilizing capacitors C2 and C3, this effectively reduces voltage fluctuations and significantly lowers output voltage ripple. Furthermore, a second-order filter consisting of L2, L4, C5, and C6 is introduced at the output to further optimize voltage signal quality, ensure output voltage stability, and further reduce output voltage ripple. To address voltage regulation, this embodiment optimizes the voltage stabilizing circuit 20 to precisely control the input voltage of the self-excited switching circuit 30, significantly enhancing the circuit's voltage regulation capability. Regarding circuit stability, the self-excited circuit structure of the self-excited switching circuit 30 completely eliminates reliance on the main control chip. By simply hardening the diodes and transistors to radiation resistance, the circuit ensures stable operation in complex radiation environments. This design not only reduces the cost of circuit components, but also greatly improves the reliability and accuracy of the secondary power supply circuit, achieving the goal of high-precision and high-reliability operation.

[0039] It should be noted that radiation hardening refers to technical measures that, through material selection, structural design, and process optimization, enable diodes or transistors to maintain normal operating performance in radiation environments, such as those found in space, nuclear reactors, and high-energy physics experiments. For example, existing hardening methods for total dose effects (TIDs) include selecting SOI (silicon-on-insulator) or SOS (silicon-on-sapphire) substrates to reduce parasitic effects; existing hardening methods for single event effects (SEEs) include using epitaxial layers or insulating substrates to suppress latch-up.

[0040] Example 2

[0041] This embodiment is basically the same as embodiment 1. Figure 5As shown, the difference is that the rectifier diodes D1 and D5 in the rectifier circuit 50 are replaced by rectifier MOS tubes Q5 and Q6 respectively, and the switch tubes Q2 and Q4 are both field effect transistors.

[0042] In this embodiment, in order to achieve high power voltage output, the switch tubes Q2 and Q4 are replaced by MOS tubes from triodes. At the same time, in order to reduce the output voltage loss caused by the rectifier diodes D1 and D5, synchronous rectifier MOS tubes Q5 and Q6 are used to replace the diodes D1 and D5 respectively. The specific circuit is as follows: Figure 5 As shown in Figure 1, this design can significantly reduce the power loss of the rectifier circuit. Since the MOS tube in this circuit is a high-side MOS, it needs to be controlled by a synchronous PWM signal. The control circuit is as follows: Figure 6 Its working principle is as follows: Figure 5 As shown in the figure, when Q2 is triggered to turn on by the bias signal, the opposite-name terminal of N1 is at a positive potential, the opposite-name terminal of N4 is positive, and the opposite-name terminal of N6 is also positive. At this time, the MOS tube Q6 is controlled to be turned on, and the forward working loop current is turned on; the conduction principle of the reverse working current loop is similar.

[0043] In this embodiment, in order to improve the output power, a synchronous rectification method and a corresponding control method are adopted to optimize the circuit structure, which significantly improves the overall output power and meets the demand for high-power power supply in fields such as aerospace.

[0044] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be included in the scope of protection of the present application. Any technical solutions that fall within the scope defined by the claims of the present invention fall within the scope of protection of the present invention.

Claims

1. A highly reliable isolated power supply circuit, characterized in that: The power supply circuit includes a transformer and a primary circuit and a secondary circuit located on both sides of the transformer; the primary circuit includes a voltage stabilizing circuit and a self-excited switching circuit, the self-excited switching circuit includes switching tubes Q2 and Q4, and the transformer includes primary windings N1 and N2 located on both sides of the primary center tap, secondary windings N3 and N4 located on both sides of the secondary center tap, and a feedback winding N5 located on the primary side; the output end of the voltage stabilizing circuit is connected to the primary center tap, the same-name end of the primary winding N1 is connected to the collector or drain of the switching tube Q2, and the opposite-name end of the primary winding N2 is connected to the collector or drain of the switching tube Q4; the two ends of the feedback winding N5 are respectively connected to the control ends of the switching tubes Q2 and Q4. When the polarity of the primary winding is reversed, the polarity of the two ends of the feedback winding N5 is reversed accordingly, so that only one of the switching tubes Q2 and Q4 is turned on at the same time.

2. The highly reliable isolated power supply circuit according to claim 1, wherein: The self-excited switching circuit also includes resistors R2, R3, R6, R7, R10, voltage-stabilizing tubes D3, D4, and capacitors C8, C9, and C11; one end of the resistors R2 and R3 are connected to the output end of the voltage-stabilizing circuit, and the other end is connected to the control end of the switch tubes Q2 and Q4 respectively; one end of the voltage-stabilizing tube D3 is connected to the control end of the switch tube Q2, and the other end is connected to the emitter or source of the switch tube Q2; one end of the voltage-stabilizing tube D4 is connected to the control end of the switch tube Q4. The control terminal of the primary winding N1 is connected to the resistor R6, R10, and the other end is connected to the emitter or source of the switch tube Q4. The emitters or sources of the switch tubes Q2 and Q4 are grounded. The branch formed by resistors R6, R10, and capacitors C8 and C11 is connected between the same-name terminal of the primary winding N1 and the opposite-name terminal of the primary winding N2. Among them, resistors R6 and R10 are connected in parallel and then connected in series with capacitors C11 and C8. Resistor R7 and capacitor C9 are connected in series between the opposite-name terminal of the feedback winding N5 and the control terminal of the switch tube Q2.

3. The highly reliable isolated power supply circuit according to claim 1, wherein: The primary circuit further includes a first filtering circuit, which includes an inductor L1, capacitors C1, C4, C7, C10, and an inductor L3, which are sequentially connected in series between the input voltage and the input ground.

4. The highly reliable isolated power supply circuit according to claim 3, wherein: The voltage stabilizing circuit includes transistors Q1, Q3, resistors R1, R4, R9, capacitors C2, C3 and a voltage stabilizing diode D2; wherein, the resistors R1, R4 and R9 are connected in series between the inductor L1 and the GND ground, the emitter and collector of the transistor Q1 are respectively connected to the two ends of the resistor R1, the base of the transistor Q1 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the connection point of R4 and R9, the emitter of the transistor Q3 is connected to one end of the resistor R8, the other end of the resistor R8 is connected to the GND ground, the two ends of the voltage stabilizing diode D2 are respectively connected to the collector of the transistor Q1 and the emitter of the transistor Q3; the capacitors C2 and C3 are connected in parallel between the collector of the transistor Q1 and the GND ground.

5. The highly reliable isolated power supply circuit according to claim 1, wherein: The secondary circuit includes a rectifier circuit and a second filter circuit. The rectifier circuit includes rectifier diodes D1 and D5. The second filter circuit includes inductors L2 and L4 and capacitors C5 and C6. The anodes of the rectifier diodes D1 and D5 are respectively connected to the same-name terminal of the secondary winding N3 and the opposite-name terminal of the secondary winding N4. The cathodes of the rectifier diodes D1 and D5 are connected to one end of the inductor L2. The other end of the inductor L2 is connected to one end of the capacitor C5. The other end of the capacitor C5 is connected to the signal ground SGND. One end of the inductor L4 is connected to the connection point between the inductor L2 and the capacitor C5, and the other end is connected to one end of the capacitor C6. The other end of the capacitor C6 is connected to the signal ground SGND. The secondary center tap is connected to the signal ground SGND.

6. The highly reliable isolated power supply circuit according to claim 5, wherein: The rectifier diodes D1 and D5 in the rectifier circuit are replaced by rectifier MOS tubes Q5 and Q6 respectively.

7. The high-reliability isolated power supply circuit according to any one of claims 1 to 6, characterized in that: The switch tubes Q2 and Q4 are both bipolar transistors or field effect transistors.

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