A constant voltage clamped unipolar fast frequency ultrasonic welding power supply

Abstract

The application provides a constant voltage clamping unipolar fast frequency ultrasonic welding power supply, which comprises a three-phase rectifier bridge circuit, a filter and voltage stabilizing circuit, a full-bridge inverter circuit, a high-frequency transformer, a secondary rectifier circuit, a fast frequency pulse switching circuit and a constant voltage clamping circuit; the fast frequency pulse switching circuit comprises switch tubes Q5 and Q6; the constant voltage clamping circuit comprises freewheeling diodes D10 and D11; the secondary rectifier circuit is connected with the center tap of the high-frequency transformer through a filter inductor and the switch tube Q5; an output load and the switch tube Q6 are connected in series, and then are connected in parallel with the switch tube Q5; the switch tubes Q5 and Q6 are connected with the positive end of the filter and voltage stabilizing circuit through the freewheeling diodes D11 and D10 respectively; and the connection position of the switch tubes Q5 and Q6 is also connected with the negative end of the filter and voltage stabilizing circuit. The fast frequency welding power supply can realize voltage peak absorption, solve the heat absorption problem, has high power supply efficiency, and has a good output waveform.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding power supply, more particularly to a single polarity fast frequency ultrasonic welding power supply with constant voltage clamping. BACKGROUND

[0002] Fast frequency welding is a processing technology using high frequency pulse current for welding, the pulse current frequency of which is greater than 20 kHz. The stability of the welding process can be improved based on the electric ultrasonic effect and arc magnetic self-confinement effect generated by fast frequency pulse modulation, the molten pool is stirred and the performance of the welded joint is improved. This process method is being intensively studied. With the emergence of the third generation of wide band gap semiconductors and the development of power device manufacturing process and digital control technology, fast frequency welding power supply has been greatly developed.

[0003] The fast frequency ultrasonic welding power supply is composed of a constant current source and a fast frequency pulse switching circuit. The constant current source part is relatively simple, mostly composed of a rectifier filter circuit, a full-bridge inverter circuit, a high frequency transformer, a secondary rectifier circuit and a power inductor. The fast frequency pulse switching circuit is the core part of the fast frequency welding power supply, and its working principle is that two switching tubes in series and parallel with the output load are complementary on and off at high frequency to generate high frequency pulse current. Foreign countries started early in high frequency pulse welding power supply. Osaka high frequency transformer company developed TR-800 power supply which can output 10 kHz pulse frequency. In 2002, IGBT was used by Akita Prefectural University to develop a peak value of 500A and a pulse frequency of 20 kHz, but the current rise rate is only 8A / us, and the current waveform is approximately triangular. The team of Qipeng of Beijing University of Aeronautics and Astronautics developed a high frequency pulse arc welding power supply, built a supersonic pulse power supply with a peak value of 100A and a frequency of 100 kHz, and a current rise rate of 50A / us, but an additional complex active absorption device is needed, which increases the complexity of the system design; the transformer ratio of the absorption circuit is adjusted to control the voltage of the absorption capacitor, which introduces additional electromagnetic interference during the operation of the power supply. The SiCMOSFET is used as a switching device in the fast frequency welding power supply developed by the team of Wang Zhenmin of South China University of Technology, and the fast frequency pulse power supply with a peak value of 200A and a maximum pulse frequency of 50 kHz is built. Its current waveform is approximately trapezoidal. In order to absorb the voltage spike of the fast frequency pulse switching circuit, a passive RC absorption device is used, but the existence of the absorption resistor causes serious heating and low efficiency. Since the output end of the fast frequency welding power supply is connected to the output load through the output cable, the inductance effect on the output cable needs to be considered in high frequency conditions. The inductance effect will slow down the current rise rate and the current fall rate, resulting in deformation of the fast frequency welding power supply output waveform. Therefore, while solving the voltage spike absorption of the fast frequency pulse switching circuit, it is necessary to ensure that the fast frequency welding power supply output waveform cannot be severely deformed. SUMMARY

[0004] In order to overcome the defects and deficiencies in the prior art, the purpose of the present application is to provide a constant voltage clamping unipolar fast frequency ultrasonic welding power supply; the fast frequency ultrasonic welding power supply can realize voltage peak absorption and solve the problem of heat absorption, has high power supply efficiency, and has good output waveform.

[0005] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme: a constant voltage clamping unipolar fast frequency ultrasonic welding power supply, comprising a three-phase rectifier bridge circuit, a filter and voltage stabilizing circuit, a full-bridge inverter circuit, a high-frequency transformer, a secondary rectifier circuit and a fast frequency pulse switching circuit connected in sequence, and a constant voltage clamping circuit.

[0006] The fast frequency pulse switching circuit comprises a switching tube Q5 and a switching tube Q6; the constant voltage clamping circuit comprises a freewheeling diode D10 and a freewheeling diode D11; the output end of the secondary rectifier circuit is connected with the center tap of the high-frequency transformer through a filter inductor Lr and the switching tube Q5; an output load and the switching tube Q6 are connected in series, and then are connected in parallel with the switching tube Q5.

[0007] The switching tube Q5 is connected with the positive end of the filter and voltage stabilizing circuit through the freewheeling diode D11, the switching tube Q6 is connected with the positive end of the filter and voltage stabilizing circuit through the freewheeling diode D10, and the connection position of the switching tube Q5 and the switching tube Q6 is also connected with the negative end of the filter and voltage stabilizing circuit; in the moment when the switching tube Q5 is turned off and the switching tube Q6 is turned on, the voltage of the switching tube Q5 is clamped at the output voltage of the filter and voltage stabilizing circuit after the freewheeling diode D11 is turned on, so as to realize the voltage peak absorption when the switching tube Q5 is turned off, and load the output voltage of the filter and voltage stabilizing circuit on the output load and the switching tube Q6 to improve the current rising rate of the fast frequency welding power supply; or in the moment when the switching tube Q6 is turned off and the switching tube Q5 is turned on, the voltage of the switching tube Q6 is clamped at the output voltage of the filter and voltage stabilizing circuit after the freewheeling diode D10 is turned on, so as to realize the voltage peak absorption when the switching tube Q6 is turned off, and load the output voltage of the filter and voltage stabilizing circuit on the output load to improve the current falling rate of the fast frequency welding power supply.

[0008] Preferably, the connection mode of the switching tube Q5, the switching tube Q6, the freewheeling diode D10 and the freewheeling diode D11 is that the positive end of the filter and voltage stabilizing circuit is connected with the cathode of the freewheeling diode D10 and the cathode of the freewheeling diode D11 respectively; the anode of the freewheeling diode D11 is connected with the secondary rectifier circuit through the filter inductor Lr, and is also connected with the drain of the switching tube Q5; the anode of the freewheeling diode D10 is connected with the drain of the switching tube Q6; the source of the switching tube Q5 and the source of the switching tube Q6 are connected with the center tap of the high-frequency transformer, and are connected with the negative end of the filter and voltage stabilizing circuit; the output load is connected between the anode of the freewheeling diode D11 and the anode of the freewheeling diode D10.

[0009] Preferably, the switch tube Q5 is connected in parallel with a diode D7, and the switch tube Q6 is connected in parallel with a diode D8.

[0010] Preferably, the anode of the diode D7 is connected with the source of the switch tube Q5, and the cathode of the diode D7 is connected with the drain of the switch tube Q5; the anode of the diode D8 is connected with the source of the switch tube Q6, and the cathode of the diode D8 is connected with the drain of the switch tube Q6.

[0011] Preferably, the filter voltage stabilizing circuit refers to a filter capacitor C1.

[0012] Preferably, the full-bridge inverter circuit adopts a full-bridge topology structure composed of four switch tubes Q1-Q4; the full-bridge inverter circuit is connected with the primary side of the high-frequency transformer; and the four switch tubes Q1-Q4 are respectively connected in parallel with capacitors.

[0013] Preferably, the secondary rectifier circuit comprises a rectifier diode D5, an absorption resistor R1, an absorption capacitor C7, a pressure resistor VDR1, a rectifier diode D6, an absorption resistor R2, an absorption capacitor C8 and a pressure resistor VDR2.

[0014] The rectifier diode D5 and the rectifier diode D6 are connected in reverse series, and then connected with the secondary side of the high-frequency transformer; the absorption resistor R1 and the absorption capacitor C7 are connected in series and then connected in parallel with the rectifier diode D5, and the rectifier diode D5 is further connected in parallel with the pressure resistor VDR1; the absorption resistor R2 and the absorption capacitor C8 are connected in series and then connected in parallel with the rectifier diode D6, and the rectifier diode D6 is further connected in parallel with the pressure resistor VDR2.

[0015] Preferably, the output load comprises a load body and an output cable; the load body is connected between the anode of the freewheeling diode D11 and the anode of the freewheeling diode D10 through the output cable.

[0016] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0017] 1. The present application can improve the power efficiency and optimize the output current waveform: the constant voltage clamping circuit directly utilizes the voltage of the primary filter voltage stabilizing circuit to perform voltage peak clamping and recovery of the energy stored in the output load inductor in the switch tube in the fast-frequency pulse switching circuit; the constant voltage clamping circuit is a lossless absorption circuit, which can greatly reduce the heating problem in the power working process compared with the passive RC absorption, and improve the power efficiency; at the same time, the current rise rate and the current drop rate of the fast-frequency welding power output can be improved, so that the fast-frequency welding power has a good output waveform.

[0018] 2、The present application simplifies the fast frequency welding power supply topology, and can realize greater rated current value output: the constant voltage clamping circuit structure is simple, and simplifies the design of the fast frequency welding power supply; compared with using an external complex active absorption device, the present application can alleviate the electromagnetic interference problem in the power supply working process on the basis of simplifying the system design, and can realize pulse current output with an output frequency of 20 kHz and an output current of 200 A. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the circuit principle diagram of the single-polarity fast frequency ultrasonic welding power supply of the present application;

[0020] Figure 2 is the full-bridge inverter working timing diagram of the single-polarity fast frequency ultrasonic welding power supply of the present application;

[0021] Figure 3 is the working mode analysis diagram of the single-polarity fast frequency ultrasonic welding power supply at the pulse current rising moment;

[0022] Figure 4 is the working mode analysis diagram of the single-polarity fast frequency ultrasonic welding power supply when the pulse current rises to a stable value;

[0023] Figure 5 is the working mode analysis diagram of the single-polarity fast frequency ultrasonic welding power supply at the pulse current falling moment;

[0024] Figure 6 is the working mode analysis diagram of the single-polarity fast frequency ultrasonic welding power supply when the pulse current falls to 0. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] EMBODIMENT

[0027] The single-polarity fast frequency ultrasonic welding power supply with constant voltage clamping of the present embodiment comprises a three-phase rectifier bridge circuit, a filter and voltage stabilizing circuit, a full-bridge inverter circuit, a high-frequency transformer, a secondary rectifier circuit and a fast frequency pulse switching circuit connected in sequence, and a constant voltage clamping circuit.

[0028] The circuit principle diagram of the single-polarity fast frequency ultrasonic welding power supply with constant voltage clamping is shown in Figure 1 The filter and voltage stabilizing circuit refers to a filter capacitor C1 (bus capacitor). The full-bridge inverter circuit adopts a full-bridge topology structure composed of four switching tubes Q1-Q4; the full-bridge inverter circuit is connected with the primary side of the high-frequency transformer; the four switching tubes Q1-Q4 are respectively connected in parallel with capacitors.

[0029] The secondary rectifier circuit comprises rectifier diode D5, absorption resistor R1, absorption capacitor C7, voltage-dependent resistor VDR1, rectifier diode D6, absorption resistor R2, absorption capacitor C8 and voltage-dependent resistor VDR2; rectifier diode D5 and rectifier diode D6 are connected in reverse series and then connected to the secondary side of the high-frequency transformer; absorption resistor R1 and absorption capacitor C7 are connected in series and then connected in parallel with rectifier diode D5, and rectifier diode D5 is further connected in parallel with voltage-dependent resistor VDR1; absorption resistor R2 and absorption capacitor C8 are connected in series and then connected in parallel with rectifier diode D6, and rectifier diode D6 is further connected in parallel with voltage-dependent resistor VDR2.

[0030] The fast-frequency pulse switching circuit comprises switch tube Q5 and switch tube Q6; the constant-voltage clamping circuit comprises freewheeling diode D10 and freewheeling diode D11. The output end of the secondary rectifier circuit is connected to the center tap of the high-frequency transformer through filter inductor Lr and switch tube Q5; the output load and switch tube Q6 are connected in series and then connected in parallel with switch tube Q5; switch tube Q5 is connected to the positive end of the filter and voltage stabilizing circuit through freewheeling diode D11, and switch tube Q6 is connected to the positive end of the filter and voltage stabilizing circuit through freewheeling diode D10, and the connection point of switch tube Q5 and switch tube Q6 is further connected to the negative end of the filter and voltage stabilizing circuit.

[0031] Specifically, the positive end of the filter and voltage stabilizing circuit is connected to the cathode of freewheeling diode D10 and the cathode of freewheeling diode D11 respectively; the anode of freewheeling diode D11 is connected to the secondary rectifier circuit through filter inductor Lr and further connected to the drain of switch tube Q5; the anode of freewheeling diode D10 is connected to the drain of switch tube Q6; the source of switch tube Q5 and the source of switch tube Q6 are connected to the center tap of the high-frequency transformer and further connected to the negative end of the filter and voltage stabilizing circuit. Switch tube Q5 is preferably connected in parallel with diode D7; switch tube Q6 is preferably connected in parallel with diode D8. The anode of diode D7 is connected to the source of switch tube Q5, and the cathode of diode D7 is connected to the drain of switch tube Q5; the anode of diode D8 is connected to the source of switch tube Q6, and the cathode of diode D8 is connected to the drain of switch tube Q6. The output load comprises a load body and an output cable; the load body is connected between the anode of freewheeling diode D11 and the anode of freewheeling diode D10 through the output cable. The equivalent inductance of the output load is Lo, and the equivalent resistance is Ro.

[0032] The three-phase rectifier bridge circuit rectifies the three-phase alternating current input from the power grid into 540V direct current with high ripple; the high-order ripple is eliminated by the filter and voltage stabilizing circuit to obtain smooth 540V direct current bus; the 540V direct current bus is converted into high-frequency alternating current by the full-bridge inverter circuit; the high-frequency alternating current is isolated and stepped down by the high-frequency transformer and then rectified into stable direct current by the secondary rectifier circuit; the direct current is converted into high-frequency pulse current output by the fast-frequency pulse switching circuit. The constant-voltage clamping circuit is used to absorb the voltage spike generated by the fast-frequency pulse switching circuit at the instant of turning off, so as to realize the rapid rise and fall of the output current.

[0033] The commonly used control strategies of full-bridge inverter circuit are limited bipolar and shift control strategy. Taking the shift control strategy as an example (the resonant inductance is the leakage inductance Lk of the transformer, which is not marked in the figure) for analysis. The working time sequence diagram of the single-pole pulse current power supply full-bridge inverter is as shown in the figure: Figure 2

[0034] Switching mode one (t0-t1 time): switch tube Q1 and switch tube Q4 are turned on together. At this time, the energy is provided to the rear stage circuit by the grid voltage after rectification and filtering, ignoring the on-voltage drop of the switch tube, the voltage across the high-frequency transformer is the bus voltage 540V, and the direction is positive down and negative. The high-frequency transformer primary current Ip rises at a certain slope through the switch tube Q1, the blocking capacitor Cb, the high-frequency transformer T1, and the switch tube Q4. The high-frequency transformer secondary current Is = Ip / n, n is the turn ratio of the high-frequency transformer, which flows through the rectifier diode D5 and the filter inductance Lr to provide energy to the output load.

[0035] Switching mode two (t1-t2 time): at t1 time, the switch tube Q1 is turned off, at this time, the output load is provided with energy by the capacitors C3 and C5 connected in parallel with the switch tube Q1 and the switch tube Q3. Capacitor C3 is charged and capacitor C5 is discharged. In this time period, the leakage inductance of the high-frequency transformer and the filter inductance Lr are in series, and the filter inductance Lr is very large, so the primary current can be considered approximately constant; similarly, the secondary current is also approximately constant. Due to the existence of capacitors C3 and C5, the switch tube Q1 is turned off with zero voltage. The flow direction of the primary current and the secondary current is the same as the previous time period.

[0036] Switching mode three (t2-t3 time): at t2 time, the voltage across capacitor C5 drops to zero, and the switch tube Q3 parallel diode D3 naturally conducts current. After that, the switch tube Q3 is turned on, and the Q3 is turned on with zero voltage. At this time, the primary current Ip flows through the switch tube Q3 parallel diode D3, the blocking capacitor Cb, the high-frequency transformer T1, and the switch tube Q4, and slowly decreases. At this time, the voltage across the high-frequency transformer and the current flowing through the high-frequency transformer are reversed, the high-frequency transformer is short-circuited, and no longer performs energy transfer, the current flowing through the rectifier diode D5 decreases slowly along the original direction, and the rectifier diode D6 conducts current.

[0037] ​Switching mode four (t3-t4 time): t3 time switch tube Q4 is off, because switch tube Q2, switch tube Q4 parallel capacitor C4, C6 exists, switch tube Q4 is zero voltage off; At this time, the original side current freewheeling circuit is transferred to capacitor C4, C6 parallel with switch tube Q2, switch tube Q4 by switch tube Q4, capacitor C4 is discharged, capacitor C6 is charged. Because the high frequency transformer is short-circuited, only the high frequency transformer leakage inductance participates in the charging and discharging process of capacitor C4, C6, so the original side current drops greatly. At this time, rectifier diode D5 and D6 are turned on simultaneously, the high frequency transformer is short-circuited, no energy transfer, the current in the filter inductor Lr flows through the rectifier diode D5 and D6 for freewheeling.

[0038] Switching mode five (t4-t5 time): t4 time capacitor C4 both ends voltage drops to zero, switch tube Q2 parallel diode D2 natural conduction freewheeling, at this time open switch tube Q2, Q2 is zero voltage open. Although the switch tube Q2 has been opened at this time, but switch tube Q2 does not flow through the current, the original side current Ip still flows through Q2 parallel diode D2, linearly under the action of bus voltage; When the original side current Ip drops to zero, the original side current Ip begins to flow through the switch tube Q2 and reversely rises, the current of rectifier diode D5 linearly decreases, and the current of rectifier diode D6 linearly increases; This stage does not still transfer energy due to the simultaneous conduction of rectifier diode D5 and D6.

[0039] The above is the working condition of half cycle, the other half condition is similar.

[0040] The working principle of the pulse switching circuit and the constant voltage clamping circuit will be introduced below.

[0041] As shown in Figure 3 , the fast frequency welding power pulse current rising moment can be considered as charging the equivalent inductance Lo of the output load, and the current rising rate is determined by the voltage U loaded on the output load. That is:

[0042]

[0043] Where, L is the output equivalent inductance of the fast frequency welding power; d i Is the current change amount of t time; d t Is the current rising time;

[0044] At this time, the switch tube Q6 is turned on, and the switch tube Q5 is turned off. It is worth noting that the filter inductor Lr is large enough, so that the current flowing through the filter inductor Lr is considered to be constant in the steady state, that is, it is approximately a constant current source. At the moment when the switch tube Q5 is turned off, the current flowing through the switch tube Q5 drops to 0 (the turn-off speed of the IGBT is very fast) instantaneously; due to the existence of the equivalent inductance Lo of the output load, the current flowing through the switch tube Q6 has a certain rising speed, that is, it rises from 0 relatively slowly; according to the KCL node equation, at this time, the freewheeling diode D11 is naturally turned on to freewheel. After the freewheeling diode D11 is turned on, the CE voltage of the switch tube Q5 is clamped at the bus voltage value 540 V, thereby realizing the voltage spike absorption when the switch tube Q5 is turned off. Ignoring the turn-on voltage drop of the switch tube Q6, at this time, the bus capacitor voltage 540 V is also loaded on the output load, providing a large current rising rate for the equivalent inductance of the output load.

[0045] As shown in Figure 4 , when the pulse current rises to a constant current value, the freewheeling diode D11 is naturally turned off with zero current, and then the constant current is supplied by the front-end circuit through the filter inductor Lr and the switch tube Q6.

[0046] As shown in Figure 5 , the pulse current drop moment can be considered as discharging the equivalent inductance Lo of the output load, and the current drop rate is determined by the voltage loaded on the output load.

[0047] At this time, the switch tube Q6 is turned off, and the switch tube Q5 is turned on. At the moment when the switch tube Q6 is turned off, the current flowing through the switch tube Q6 drops to 0 (the turn-off speed of the IGBT is very fast) instantaneously; but due to the existence of the equivalent inductance Lo of the output load, the current flowing through the output load has a certain falling speed, that is, it falls from the rated output current relatively slowly; according to the KCL node equation, at this time, the freewheeling diode D10 is naturally turned on to freewheel, and after the freewheeling diode D10 is turned on, the CE voltage of the switch tube Q6 is clamped at the bus voltage value 540 V, thereby realizing the voltage spike absorption when the switch tube Q6 is turned off. At the same time, the bus capacitor voltage 540 V is reversely loaded on the output load, providing a large current falling rate for the equivalent inductance of the output load.

[0048] As shown in Figure 6 , when the pulse current falls to zero, the freewheeling diode D10 is naturally turned off with zero current, and then the freewheeling is performed by the front-end circuit through the filter inductor Lr and the switch tube Q5.

[0049] The above embodiment is a preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the present application should be an equivalent replacement mode, and all are included in the protection scope of the present application.

Claims

1. A constant voltage clamped unipolar fast frequency ultrasonic welding power supply characterized by: The fast frequency pulse switching circuit comprises a switch tube Q5 and a switch tube Q6; the constant voltage clamping circuit comprises a freewheeling diode D10 and a freewheeling diode D11; the output end of the secondary rectifier circuit is connected with the center tap of the high-frequency transformer through a filter inductor Lr and the switch tube Q5; an output load and the switch tube Q6 are connected in series, and then are connected in parallel with the switch tube Q5. The switch tube Q5 is connected with the positive end of the filter voltage stabilizing circuit through the freewheeling diode D11, the switch tube Q6 is connected with the positive end of the filter voltage stabilizing circuit through the freewheeling diode D10, and the connection position of the switch tube Q5 and the switch tube Q6 is also connected with the negative end of the filter voltage stabilizing circuit; in the moment when the switch tube Q5 is turned off and the switch tube Q6 is turned on, the voltage of the switch tube Q5 is clamped at the output voltage of the filter voltage stabilizing circuit after the freewheeling diode D11 is turned on, so that the voltage peak when the switch tube Q5 is turned off is absorbed, and the output voltage of the filter voltage stabilizing circuit is loaded on the output load and the switch tube Q6 to improve the current rising rate of the fast frequency welding power supply; or in the moment when the switch tube Q6 is turned off and the switch tube Q5 is turned on, the voltage of the switch tube Q6 is clamped at the output voltage of the filter voltage stabilizing circuit after the freewheeling diode D10 is turned on, so that the voltage peak when the switch tube Q6 is turned off is absorbed, and the output voltage of the filter voltage stabilizing circuit is loaded on the output load to improve the current falling rate of the fast frequency welding power supply. The connection mode of the switch tube Q5, the switch tube Q6, the freewheeling diode D10 and the freewheeling diode D11 is that the positive end of the filter voltage stabilizing circuit is connected with the cathode of the freewheeling diode D10 and the cathode of the freewheeling diode D11 respectively; the anode of the freewheeling diode D11 is connected with the secondary rectifier circuit through the filter inductor Lr, and is also connected with the drain of the switch tube Q5; the anode of the freewheeling diode D10 is connected with the drain of the switch tube Q6; the source of the switch tube Q5 and the source of the switch tube Q6 are connected with the center tap of the high-frequency transformer respectively, and are connected with the negative end of the filter voltage stabilizing circuit; the output load is connected between the anode of the freewheeling diode D11 and the anode of the freewheeling diode D10.

2. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: The switch tube Q5 is connected in parallel with a diode D7; the switch tube Q6 is connected in parallel with a diode D8.

3. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: The anode of the diode D7 is connected with the source of the switch tube Q5, and the cathode of the diode D7 is connected with the drain of the switch tube Q5; the anode of the diode D8 is connected with the source of the switch tube Q6, and the cathode of the diode D8 is connected with the drain of the switch tube Q6.

4. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 3, wherein: The filter voltage stabilizing circuit refers to a filter capacitor C1.

5. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: The full-bridge inverter circuit adopts a full-bridge topology structure composed of four switch tubes Q1-Q4; the full-bridge inverter circuit is connected with the primary side of the high-frequency transformer; the four switch tubes Q1-Q4 are connected in parallel with capacitors respectively.

6. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: The secondary rectifier circuit comprises a rectifier diode D5, an absorption resistor R1, an absorption capacitor C7, a pressure-sensitive resistor VDR1, a rectifier diode D6, an absorption resistor R2, an absorption capacitor C8 and a pressure-sensitive resistor VDR2.

7. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: ​ Rectifier diode D5 and rectifier diode D6 are connected in reverse series, and then connected with the secondary side of the high-frequency transformer; the absorbing resistor R1 and the absorbing capacitor C7 are connected in series, and then connected in parallel with the rectifier diode D5, and the rectifier diode D5 is also connected in parallel with the voltage-dependent resistor VDR1; the absorbing resistor R2 and the absorbing capacitor C8 are connected in series, and then connected in parallel with the rectifier diode D6, and the rectifier diode D6 is also connected in parallel with the voltage-dependent resistor VDR2.

8. The constant voltage clamped unipolar fast frequency ultrasonic welding power supply of claim 1, wherein: The output load comprises a load body and an output cable; the load body is connected between the anode of the freewheeling diode D11 and the anode of the freewheeling diode D10 through the output cable.

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