A power supply device for a traveling wave tube

Abstract

The utility model provides a kind of power supply device for traveling wave tube power supply, the power supply device includes cathode power module, control electrode power module, collecting electrode power module, filament power module and titanium pump power module. Through the parallel power module of the utility model, the power supply of cathode, control electrode, collecting electrode, filament, titanium pump etc. of traveling wave tube is realized respectively, and the stable normal operation of traveling wave tube is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of high-voltage power supply technology, and more specifically, to a power supply device for powering traveling wave tubes. Background Technology

[0002] Traveling wave tube (TWT) high-voltage converters are key components in electronic equipment, used to transform the input voltage from the mains frequency grid into the required system voltage, providing a stable high-voltage power supply to the load. Traditional TWT high-voltage converters have several design shortcomings, such as complex structure, difficult maintenance, low reliability, and difficulty adapting to different operating environments. Furthermore, traditional high-voltage converters also need improvement in control accuracy and response speed, failing to meet the high-precision and fast-response requirements of modern electronic equipment for high-voltage power supplies. Summary of the Invention

[0003] This invention addresses the technical problems existing in the prior art by providing a power supply device for powering a traveling wave tube, which can provide a stable voltage to the traveling wave tube.

[0004] This utility model provides a power supply device for powering a traveling wave tube, including a cathode power supply module, a control electrode power supply module, a collector electrode power supply module, a filament power supply module, and a titanium pump power supply module.

[0005] The cathode power module converts the 750V DC input voltage into a -35kV high voltage output. The positive terminal of the output of the cathode power module is connected to the cathode, and the negative terminal is connected to the cathode of the traveling wave tube, providing a stable high voltage to the cathode of the traveling wave tube.

[0006] The control electrode power module converts the 750V DC input voltage into a high-frequency AC voltage. The positive terminal of the control electrode power module is connected to the cathode, and the negative terminal is connected to the control electrode of the traveling wave tube, providing voltage to the control electrode of the traveling wave tube.

[0007] The collector power module converts the DC input voltage into a high-voltage DC output. The negative terminal of the collector power module is connected to the cathode, and the positive terminal is connected to the collector of the traveling wave tube to supply power to the collector of the traveling wave tube.

[0008] The filament power supply module converts the 220V AC input voltage into a stable DC output current. The positive terminal of the output terminal of the filament power supply module is connected to the cathode, and the negative terminal is connected to the filament of the traveling wave tube, providing a stable heating current for the filament of the traveling wave tube.

[0009] The titanium pump power module converts the 220V AC input voltage into a 4kV high voltage. The negative terminal of the output of the titanium pump power module is connected to the cathode, and the positive terminal is connected to the titanium pump. The titanium pump is used to maintain the high vacuum environment required for the operation of the traveling wave tube.

[0010] This utility model provides a power supply device for powering a traveling wave tube. Through different power supply modules of this utility model, the cathode, control electrode, collector electrode, filament, titanium pump, etc. of the traveling wave tube are powered respectively, ensuring the stable and normal operation of the traveling wave tube. Attached Figure Description

[0011] Figure 1 The circuit diagram of a power supply device for powering a traveling wave tube provided by this utility model;

[0012] Figure 2 This is a circuit diagram illustrating the working principle of the cathode power supply module.

[0013] Figure 3 This is a schematic diagram of the circuit block of the control electrode power supply module;

[0014] Figure 4 This is a circuit diagram illustrating the working principle of the control electrode power supply module.

[0015] Figure 5 The circuit schematic for the collector power supply module;

[0016] Figure 6 This is a circuit block diagram of the filament power supply module;

[0017] Figure 7 This is the circuit schematic of the filament power supply module. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model. In addition, the technical features of the various embodiments or individual embodiments provided by this utility model can be arbitrarily combined to form feasible technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0019] Figure 1 The present invention provides a power supply device for powering a traveling wave tube, which includes a cathode power supply module, a control electrode power supply module, a collector electrode power supply module, a filament power supply module, and a titanium pump power supply module, which respectively provide stable voltages to the cathode, control electrode, collector electrode, filament, and titanium pump of the traveling wave tube.

[0020] The cathode power supply module converts the 750V DC input voltage into a -35kV high voltage output. The positive terminal of the output of the cathode power supply module is connected to the cathode, and the negative terminal is connected to the cathode of the traveling wave tube, providing a stable high voltage to the cathode of the traveling wave tube.

[0021] The control electrode power module converts the 750V DC input voltage into a high-frequency AC voltage. The positive terminal of the control electrode power module is connected to the cathode, and the negative terminal is connected to the control electrode of the traveling wave tube, providing voltage to the control electrode of the traveling wave tube.

[0022] The collector power module converts the DC input voltage into a high-voltage DC output. The negative terminal of the collector power module is connected to the cathode, and the positive terminal is connected to the collector of the traveling wave tube to supply power to the collector of the traveling wave tube.

[0023] The filament power supply module converts the 220V AC input voltage into a stable DC output current. The positive terminal of the output terminal of the filament power supply module is connected to the cathode, and the negative terminal is connected to the filament of the traveling wave tube, providing a stable heating current for the filament of the traveling wave tube.

[0024] The titanium pump power module converts the 220V AC input voltage into a 4kV high voltage. The negative terminal of the output of the titanium pump power module is connected to the cathode, and the positive terminal is connected to the titanium pump. The titanium pump is used to maintain the high vacuum environment required for the operation of the traveling wave tube.

[0025] See Figure 2 The diagram shows the circuit schematic of the cathode power supply module. The cathode power supply module includes a first full-bridge inverter circuit (composed of four MOS switches FETD1, FETD2, FETD3, and FETD4), a first LC resonant circuit, a first transformer Tr1, a first rectifier module (a full-bridge rectifier circuit composed of four diodes D1, D2, D3, and D4), a capacitor C0, and a resistor R1. The two input terminals of the first full-bridge inverter circuit are connected to the positive and negative terminals of the DC power supply, respectively. The two output terminals of the first full-bridge inverter circuit are connected to the primary side of the transformer Tr1 through the first LC resonant circuit. The secondary side of the transformer Tr1 is connected to the two input terminals of the first rectifier module. The capacitor C0 and the resistor R1 are connected in parallel between the positive and negative terminals of the output terminal of the first rectifier module, and the negative terminal of the output terminal of the first rectifier module is grounded.

[0026] The cathode power module converts the 750V DC input voltage to -35kV. Switching elements (FETs) alternately turn on and off to achieve voltage conversion. The resonant inductor (Lr) and resonant capacitor (Cr) form an LC resonant circuit. The rectifier diodes (D1-D4) convert the output AC power into DC power. The output capacitor C0 is used to smooth the output voltage and reduce output voltage ripple.

[0027] See Figure 3 The circuit diagram shows the control electrode power supply module. The control electrode power supply module includes a first AC-DC circuit, a first half-bridge switch and resonant circuit, a first transformer isolation circuit, a first high-frequency rectifier and filter circuit, a first BUCK circuit, and a load, all connected in sequence. The input AC voltage is converted to DC voltage by the first AC-DC circuit. The DC voltage is then converted to high-frequency AC voltage by the first half-bridge switch and resonant circuit. The DC voltage is then isolated, rectified, and stepped down by the first transformer isolation circuit and the first high-frequency rectifier and filter circuit. Finally, the first BUCK circuit reduces the voltage so that the output voltage meets the voltage range required by the control electrode of the traveling wave tube.

[0028] The control electrode power supply adopts a composite topology of a full-bridge series resonant converter combined with a BUCK buck circuit, which makes full use of the advantages of the two circuits and achieves efficient, stable and reliable power output.

[0029] Among them, see Figure 4 The first half-bridge switch and resonant circuit includes capacitor C1, full-bridge switch Q1, resonant inductor Lr1 and resonant capacitor Cr1. The first voltage isolation circuit is transformer Tr2. The first high-frequency rectifier and filter circuit includes high-frequency full-bridge rectifier module Q2 and filter capacitor C2. The first BUCK circuit includes switching device Q3, synchronous rectifier MOS switch Q4, energy storage inductor L1 and filter capacitor C3.

[0030] The two input terminals of the first ACDC circuit are connected to AC voltage. The two output terminals of the first ACDC circuit are respectively connected to the two input terminals of the full-bridge switch Q1. A capacitor C1 is connected in parallel between the two input terminals of the full-bridge switch Q1. The two output terminals of the full-bridge switch Q1 are respectively connected to the primary side of transformer T1 through resonant inductor Lr and resonant capacitor Cr1. The secondary side of transformer Tr2 is connected to the two input terminals of high-frequency full-bridge rectifier module Q2. One output terminal of high-frequency full-bridge rectifier module Q2 is connected to the first terminal of energy storage inductor L1 through the switching device Q3. The first terminal of energy storage inductor L1 is connected to the other output terminal of high-frequency full-bridge rectifier module Q2 through synchronous rectifier MOS switch Q4. A capacitor C2 is connected between the two output terminals of high-frequency full-bridge rectifier module Q2. The second terminal of energy storage inductor L1 is connected to the second terminal of high-frequency full-bridge rectifier module Q2 through filter capacitor C3 and load RL.

[0031] The full-bridge series resonant converter section is responsible for converting the input DC voltage into a high-frequency AC voltage using high-frequency inverter technology, and achieving efficient voltage and current conversion using a resonant circuit. The inductors and capacitors in the resonant circuit, through resonance, enable the switching elements to switch under zero-voltage or zero-current conditions, thereby significantly reducing switching losses and improving power supply efficiency.

[0032] However, the output voltage ripple of a full-bridge resonant converter is typically high and not directly applicable to the load. Therefore, a buck converter circuit is connected after the resonant converter. The buck circuit reduces the high output voltage of the resonant converter by adjusting the duty cycle of the switching elements. The buck circuit provides continuous current output and, combined with current limiting and overvoltage protection mechanisms, ensures that the power supply can respond quickly and protect the load from damage in abnormal conditions such as load short circuits or open circuits.

[0033] The control electrode power module design fully utilizes the advantages of the full-bridge series resonant converter and the BUCK step-down circuit to achieve efficient, stable, and reliable power output, and has a complete protection and monitoring mechanism to ensure the safe operation of the load.

[0034] See Figure 5 The circuit diagram shows the collector power module, which includes a second full-bridge inverter circuit (composed of MOS switches FET5, FET6, FET7, and FET8), a second LC resonant circuit (composed of resonant inductor Lr3 and resonant capacitor Cr3), a transformer Tr3, a second rectifier module (composed of diodes D5, D6, D7, and D8), a capacitor C4, and a resistor R2. The two input terminals of the second full-bridge inverter are connected to the positive and negative terminals of the DC power supply, respectively. The two output terminals of the second full-bridge inverter circuit are connected to the primary side of the transformer Tr3 through the second LC resonant circuit. The secondary side of the transformer Tr3 is connected to the two input terminals of the second rectifier module. The capacitor C4 and the resistor R2 are connected in parallel between the positive and negative output terminals of the second rectifier module.

[0035] The collector power module also includes a third full-bridge inverter circuit (composed of MOS switches FET9, FET10, FET11, and FET12), a third LC resonant circuit (composed of resonant inductor Lr4 and resonant capacitor Cr4), a transformer Tr4, and a third rectifier module (composed of diodes D9, D10, D11, and D12). The two input terminals of the third full-bridge inverter are respectively connected to the positive and negative terminals of the DC power supply. The two output terminals of the third full-bridge inverter circuit are connected to the primary side of the transformer Tr4 through the third LC resonant circuit. The secondary side of the transformer Tr4 is connected to the two input terminals of the third rectifier module. The positive output terminal of the third rectifier module is connected to the positive output terminal of the second rectifier module, and the negative output terminal of the third rectifier module is connected to the negative output terminal of the second rectifier module.

[0036] The collector power module adopts a full-bridge LC series resonant power topology (hereinafter referred to as series resonant topology) and an interleaved parallel control mode to improve the equivalent operating frequency, reduce output voltage ripple, and improve the stability of the output voltage.

[0037] See Figure 6 The diagram shows the circuit block diagram of the filament power supply module. The filament power supply module includes a second AC-DC circuit, a second half-bridge switch and resonant circuit, a second transformer isolation circuit, a second high-frequency rectifier and filter circuit, and a second BUCK circuit, which are connected in sequence.

[0038] The input AC voltage is converted into DC voltage by the second ACDC circuit, and then converted into high-frequency AC voltage by the second half-bridge switch and resonant circuit. It is then isolated, rectified, and stepped down by the second transformer isolation circuit and the second high-frequency rectifier filter circuit to provide a stable power supply for the filament of the traveling wave tube.

[0039] The filament power supply module uses a composite topology combining a half-bridge isolation circuit and a BUCK step-down circuit. This topology combines the efficiency of a half-bridge isolation circuit with the flexibility of a BUCK circuit, providing a stable and reliable power supply solution for the filament.

[0040] The filament power supply has an input voltage of 220±13%Vac. Through a half-bridge isolation circuit and a BUCK circuit, it ultimately outputs a constant DC current of 4A~8A with an output current stability of ≤±0.02A. It achieves stable constant current and voltage-limited output and can operate under both short-circuit and open-circuit conditions. The filament power supply mainly consists of an uncontrolled rectifier filter, a driver circuit, a half-bridge switching circuit, a resonant circuit, a transformer isolation circuit, a BUCK circuit, and a sampling circuit.

[0041] See Figure 7The diagram shows the circuit schematic of the filament power supply module. The second ACDC circuit is the third rectifier module (composed of diodes D13, D14, D15, and D16). The second half-bridge switch and resonant circuit includes electrolytic capacitors C5 and C6, MOS switches T1 and T2, and resonant inductor Lr4. The second high-frequency rectification and filtering circuit is the fourth rectifier module. The second BUCK circuit includes MOS switch T3, resonant inductor Lr5, diode D21, and capacitor C8. The two input terminals of the third rectifier module are connected to the positive and negative terminals of the power supply. The positive output terminal of the third rectifier module is connected to the negative output terminal of the third rectifier module through electrolytic capacitors C5 and C6, and the positive output terminal of the third rectifier module is connected to the MOS switch T3. Switch T1 and MOS switch T2 are connected to the negative output terminal of the third rectifier module. The common point of electrolytic capacitors C5 and C6 and the common point of MOS switches T1 and T2 are connected to the primary side of transformer Tr4 through resonant inductor Lr4. The secondary side of transformer Tr4 is connected to the two input terminals of the fourth rectifier module. Capacitor C7 is connected in parallel between the positive and negative output terminals of the fourth rectifier module. The positive output terminal of the fourth rectifier module is connected to the first terminal of resonant inductor Lr5 through MOS switch T3. The first terminal of resonant inductor Lr5 is connected to the negative output terminal of the fourth rectifier module through diode D21. The second terminal of resonant inductor Lr5 is connected to the negative output terminal of the fourth rectifier module through capacitor C8.

[0042] The filament power supply employs a composite topology combining a half-bridge isolation circuit and a BUCK step-down circuit, fully leveraging the advantages of both circuits to achieve efficient, stable, and reliable power output. Its advantages include:

[0043] (1) Uncontrolled rectifier circuit:

[0044] The filament power supply is first connected to a standard 220Vac AC voltage. The input AC power is rectified and filtered to convert the unstable AC power into a smoother DC power, providing a foundation for the stable operation of the subsequent circuit.

[0045] (2) Half-bridge circuit:

[0046] A half-bridge series resonant circuit is used. The half-bridge circuit consists of two MOSFETs, which are connected to the input power supply and output terminal via an inductor and capacitor, forming a basic power conversion topology. The half-bridge isolation circuit is responsible for converting the input DC voltage to a high-frequency AC voltage using high-frequency inverter technology, and achieving efficient voltage and current conversion using the resonant circuit. The inductor and capacitor in the resonant circuit, through resonance, allow the switching elements to switch under zero-voltage or zero-current conditions, thereby greatly reducing switching losses and improving power supply efficiency. Furthermore, fixed-frequency, fixed-width modulation technology is used to precisely control the frequency and width of the current, ensuring the stability and efficiency of the circuit operation.

[0047] (3) Buck circuit:

[0048] Because the output voltage ripple of a half-bridge resonant circuit is typically high, it is not directly suitable for filament loads. Therefore, a buck converter circuit is connected after the resonant circuit. The buck converter circuit reduces the high voltage output of the resonant circuit to the voltage required by the filament by adjusting the duty cycle of the switching elements. The buck converter circuit can provide continuous current output, and combined with current limiting and overvoltage protection mechanisms, it ensures that the power supply can respond quickly and protect the load from damage in abnormal conditions such as load short circuits or open circuits.

[0049] (4) Control aspects:

[0050] In terms of control, the controller is located on the low-voltage side, a layout that effectively ensures the safety of control operations. The controller precisely controls the BUCK circuit via fiber optic signals, leveraging the high speed and strong anti-interference capabilities of fiber optic signal transmission to ensure that control commands are transmitted quickly and accurately. Simultaneously, key parameters in the circuit are acquired in real time via fiber optics, providing accurate data feedback to the controller for timely adjustments to the control strategy.

[0051] This invention provides a power supply device for powering a traveling wave tube (TWT). The power supply device includes a cathode power supply module, a control electrode power supply module, a collector electrode power supply module, a filament power supply module, and a titanium pump power supply module. Through the parallel power supply modules of this invention, power is supplied to the cathode, control electrode, collector electrode, filament, titanium pump, etc., of the TWT, ensuring the stable and normal operation of the TWT.

[0052] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0053] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.

Claims

1. A power supply device for powering a traveling wave tube, characterized in that, The power supply device includes a cathode power supply module, a control electrode power supply module, a collector electrode power supply module, a filament power supply module, and a titanium pump power supply module. The cathode power module converts the 750V DC input voltage into a -35kV high voltage output. The positive terminal of the output of the cathode power module is connected to the cathode, and the negative terminal is connected to the cathode of the traveling wave tube, providing a stable high voltage to the cathode of the traveling wave tube. The control electrode power module converts the 750V DC input voltage into a high-frequency AC voltage. The positive terminal of the control electrode power module is connected to the cathode, and the negative terminal is connected to the control electrode of the traveling wave tube, providing voltage to the control electrode of the traveling wave tube. The collector power module converts the DC input voltage into a high-voltage DC output. The negative terminal of the collector power module is connected to the cathode, and the positive terminal is connected to the collector of the traveling wave tube to supply power to the collector of the traveling wave tube. The filament power supply module converts the 220V AC input voltage into a stable DC output current. The positive terminal of the output terminal of the filament power supply module is connected to the cathode, and the negative terminal is connected to the filament of the traveling wave tube, providing a stable heating current for the filament of the traveling wave tube. The titanium pump power module converts the 220V AC input voltage into a 4kV high voltage. The negative terminal of the output of the titanium pump power module is connected to the cathode, and the positive terminal is connected to the titanium pump. The titanium pump is used to maintain the high vacuum environment required for the operation of the traveling wave tube.

2. The power supply device according to claim 1, characterized in that, The cathode power supply module includes a first full-bridge inverter circuit, a first LC resonant circuit, a first transformer Tr1, a first rectifier module, a capacitor C0, and a resistor R1. The two input terminals of the first full-bridge inverter circuit are respectively connected to the positive and negative terminals of the DC power supply. The two output terminals of the first full-bridge inverter circuit are connected to the primary side of the transformer Tr1 through the first LC resonant circuit. The secondary side of the transformer Tr1 is connected to the two input terminals of the first rectifier module. The capacitor C0 and the resistor R1 are connected in parallel between the positive and negative output terminals of the first rectifier module, and the negative output terminal of the first rectifier module is grounded.

3. The power supply device according to claim 1, characterized in that, The control electrode power module includes a first ACCDC circuit, a first half-bridge switch and resonant circuit, a first transformer isolation circuit, a first high-frequency rectifier and filter circuit, a first BUCK circuit and a load, which are connected in sequence. The input AC voltage is converted into DC voltage by the first ACDC circuit, and then converted into high-frequency AC voltage by the first half-bridge switch and resonant circuit. It is then isolated, rectified and isolated by the first transformer isolation circuit and the first high-frequency rectifier filter circuit, and stepped down by the first BUCK circuit so that the output voltage meets the voltage range required by the control electrode of the traveling wave tube.

4. The power supply device according to claim 3, characterized in that, The first half-bridge switch and resonant circuit includes capacitor C1, full-bridge switch Q1, resonant inductor Lr1 and resonant capacitor Cr1; the first transformer isolation circuit is transformer Tr2; the first high-frequency rectifier and filter circuit includes high-frequency full-bridge rectifier module Q2 and filter capacitor C2; the first BUCK circuit includes switching device Q3, synchronous rectifier MOS switch Q4, energy storage inductor L1 and filter capacitor C3. The two input terminals of the first ACDC circuit are connected to AC voltage. The two output terminals of the first ACDC circuit are respectively connected to the two input terminals of the full-bridge switch Q1. A capacitor C1 is connected in parallel between the two input terminals of the full-bridge switch Q1. The two output terminals of the full-bridge switch Q1 are respectively connected to the primary side of transformer T1 through resonant inductor Lr and resonant capacitor Cr1. The secondary side of transformer Tr2 is connected to the two input terminals of high-frequency full-bridge rectifier module Q2. One output terminal of high-frequency full-bridge rectifier module Q2 is connected to the first terminal of energy storage inductor L1 through the switching device Q3. The first terminal of energy storage inductor L1 is connected to the other output terminal of high-frequency full-bridge rectifier module Q2 through synchronous rectifier MOS switch Q4. A capacitor C2 is connected between the two output terminals of high-frequency full-bridge rectifier module Q2. The second terminal of energy storage inductor L1 is connected to the second terminal of high-frequency full-bridge rectifier module Q2 through filter capacitor C3 and load RL.

5. The power supply device according to claim 1, characterized in that, The collector power module includes a second full-bridge inverter circuit, a second LC resonant circuit, a transformer Tr3, a second rectifier module, a capacitor C4, and a resistor R2. The two input terminals of the second full-bridge inverter circuit are respectively connected to the positive and negative terminals of the DC power supply. The two output terminals of the second full-bridge inverter circuit are connected to the primary side of the transformer Tr3 through the second LC resonant circuit. The secondary side of the transformer Tr3 is connected to the two input terminals of the second rectifier module. The capacitor C4 and the resistor R2 are connected in parallel between the positive and negative output terminals of the second rectifier module. The collector power module further includes a third full-bridge inverter circuit, a third LC resonant circuit, a transformer Tr4, and a third rectifier module. The two input terminals of the third full-bridge inverter circuit are respectively connected to the positive and negative terminals of the DC power supply. The two output terminals of the third full-bridge inverter circuit are connected to the primary side of the transformer Tr4 through the third LC resonant circuit. The secondary side of the transformer Tr4 is connected to the two input terminals of the third rectifier module. The positive output terminal of the third rectifier module is connected to the positive output terminal of the second rectifier module, and the negative output terminal of the third rectifier module is connected to the negative output terminal of the second rectifier module.

6. The power supply device according to claim 1, characterized in that, The filament power supply module includes a second ACCDC circuit, a second half-bridge switch and resonant circuit, a second transformer isolation circuit, a second high-frequency rectifier and filter circuit, and a second BUCK circuit that are connected in sequence. The input AC voltage is converted into DC voltage by the second ACDC circuit, and then converted into high-frequency AC voltage by the second half-bridge switch and resonant circuit. It is then isolated, rectified, and stepped down by the second transformer isolation circuit and the second high-frequency rectifier filter circuit to provide a stable power supply for the filament of the traveling wave tube.

7. The power supply device according to claim 6, characterized in that, The second ACDC circuit is a third rectifier module. The second half-bridge switch and resonant circuit includes electrolytic capacitor C5, electrolytic capacitor C6, MOS switch T1, MOS switch T2, and resonant inductor Lr4. The second high-frequency rectifier and filter circuit is a fourth rectifier module. The second BUCK circuit includes MOS switch T3, resonant inductor Lr5, diode D21, and capacitor C8. The two input terminals of the third rectifier module are connected to the positive and negative terminals of the power supply. The positive output terminal of the third rectifier module is connected to the negative output terminal of the third rectifier module through electrolytic capacitors C5 and C6. The positive output terminal of the third rectifier module is connected to the fourth rectifier module through MOS switch T1 and MOS switch T2. The negative terminal of the output of the third rectifier module is connected to the primary side of transformer Tr4 via the common point of electrolytic capacitors C5 and C6 and the common point of MOS switches T1 and T2. The secondary side of transformer Tr4 is connected to the two input terminals of the fourth rectifier module. A capacitor C7 is connected in parallel between the positive and negative terminals of the output of the fourth rectifier module. The positive terminal of the output of the fourth rectifier module is connected to the first terminal of the resonant inductor Lr5 via MOS switch T3. The first terminal of the resonant inductor Lr5 is connected to the negative terminal of the output of the fourth rectifier module via diode D21. The second terminal of the resonant inductor Lr5 is connected to the negative terminal of the output of the fourth rectifier module via capacitor C8.

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