Low-voltage, high-power pulse power supply and control method

Abstract

The present invention discloses a low-voltage, high-power pulse power supply comprising n chopper circuits, each comprising a branch circuit consisting of a power switch tube, a power diode, and an inductor. The DC input and DC output sides of the n branches of the chopper circuits are connected in parallel, with the DC input side connected to the same DC input voltage, and the DC output side connected in parallel to a filter capacitor and a load resistor. The present invention also discloses a control method for a low-voltage, high-power pulse power supply. This low-voltage, high-power pulse power supply and control method address the problems of low power supply efficiency and limited output current found in conventional pulse power supplies.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic control, and in particular relates to a low-voltage high-power pulse power supply, and also relates to a low-voltage high-power pulse power supply control method. Background Art

[0002] In order to improve the processing quality of machine tools, the technology of using pulse power supply to generate electric sparks for processing has attracted widespread attention. As the core technology of electric spark processing technology, the current control method of pulse power supply is crucial. Traditional pulse power supplies usually use a power switch tube in series with a current limiting resistor to form a branch. After multiple branches are connected in parallel, pulse current is provided to the common load. The driving pulse signal of the power switch tube in each branch is the same, and different processing currents are selected by the on-off combination of different power switch tubes. Since the current limiting resistor only plays a current limiting role and consumes a lot of energy, the efficiency of the pulse power supply is very low. At the same time, the circuit structure can only output a small current, and the instantaneous output energy is not high. It is impossible to process large workpieces. It is only suitable for ultra-high frequency low-power electrical processing pulse power supply. In addition, it is not applicable to current pulse power supply with medium and low frequencies of several kHz and below. Therefore, the present invention proposes a low-voltage and high-current pulse power supply control method based on the parallel connection of multiple choppers to solve the problems existing in traditional pulse power supply. Summary of the Invention

[0003] The first purpose of the present invention is to provide a low-voltage, high-power pulse power supply to solve the problems of low power efficiency and only small current output of traditional pulse power supplies.

[0004] In order to achieve the above-mentioned first purpose, the technical solution adopted by the present invention is: a low-voltage, high-power pulse power supply, including n chopper circuits, each chopper circuit is composed of a branch consisting of a power switch tube, a power diode and an inductor, the DC input side and the DC output side of the chopper circuit of the n branches are respectively connected in parallel, the DC input side is connected to the same DC input voltage, and the DC output side is connected in parallel to the filter capacitor and the load resistor.

[0005] As a preferred technical solution of the present invention, the nth chopper circuit includes a power switch S n , power diode D n 、Inductor L n and current sensor, where n represents: 1, 2, 3..., n; where: power switch S n The drain of the power switch S is connected to the positive terminal of the DC input power supply. n The source of each of them is connected to the power diode D n The cathode and inductance L n One end of the inductor L n The other end is connected to one end of the current sensor, and its output sampling current is i LnThe other end of the current sensor is connected to the output filter capacitor C o The anode of the power diode D n The anode of the filter capacitor C is connected to the negative electrode of the DC input power supply; o The anode is also connected to one end of the output current sensor. The output sampling current of the output current sensor is i o The other end of the output current sensor is connected to one end of the load resistor R, and the other end of the load resistor R is connected to the negative electrode of the DC input power supply. The filter capacitor C o The cathode is also connected to the negative pole of the DC input power supply.

[0006] As a preferred technical solution of the present invention, the power switch tube is a power MOSFET.

[0007] The second object of the present invention is to provide a low-voltage, high-power pulse power supply control method to solve the problem that traditional pulse power supplies have low power efficiency and can only output small current.

[0008] In order to achieve the above-mentioned second purpose, the technical solution adopted by the present invention is: a low-voltage, high-power pulse power supply control method, based on an n-way parallel chopper circuit, combines output current feedback control, output voltage feedforward control and inductor current equalization control to perform pulse current control.

[0009] As a preferred technical solution of the present invention, it is specifically implemented according to the following steps:

[0010] Step 1: Set the output current reference value i oref and the actual output current feedback value i o The difference is controlled by the proportional integral (PI) regulator to obtain the feedback modulation coefficient d fk , the actual DC output voltage u o Divide by the DC input voltage u in Get the feedforward modulation coefficient d fw , the feedback modulation coefficient d fk and the feedforward modulation coefficient d fw The sum of the added values ​​is represented by C1; the output current of one-nth is used as the reference value, represented by C2; C2 minus the inductor current value i of the nth chopper circuit Ln The difference is multiplied by the proportional coefficient K n , and obtain the current sharing modulation coefficient d mn , so the modulation coefficient d of the nth chopper circuit power switch can be obtained n =C1+d mn =d fk +d fw +d mn ;

[0011] Step 2: For n chopper circuits, use carrier phase shifting technology to generate PWM waves with sawtooth waves and carrier periods of T. s ; Carrier signal cf of the nth chopper circuit n It lags behind the carrier signal cf1 of the first chopper circuit by (n-1)Ts / n;

[0012] The desired output current pulse waveform is: In one output current pulse period T o Internal, 0~t on The output current reference value during the time period is I o , t on ~T o The output current reference value is 0 during the time period; the following T o Repeat the above desired output current pulse waveform over and over again; change I o You can change the output pulse current size and change T o The pulse current frequency can be output by changing t on The output pulse current width can be changed;

[0013] Therefore, the modulation signal d of the nth chopper circuit is n The corresponding carrier signal cf n Compare and get the PWM signal pwm n ; The expected output current pulse period is T o , T o Much larger than T s , the output current pulse width is t on , and 2T s ≤t on ≤T o , convert the expected output current pulse into a logic level signal. The expected output current pulse amplitude is I o When the output current pulse amplitude is zero, it corresponds to a high level. The high and low level signals T o with pwm n Perform a "logical AND" operation to obtain the nth chopper circuit power switch S n The control signal g n , thereby controlling the nth chopper circuit power switch to operate.

[0014] The beneficial effects of the present invention are: a low-voltage, high-power pulse power supply and control method of the present invention, based on an n-way parallel chopper circuit, combines output current feedback control, output voltage feedforward control and inductor current equalization control to obtain a new pulse current control method. The control method is simple, reliable and easy to implement. It can realize medium and low frequency current pulses, output large current and resist load current disturbances, has excellent dynamic and static performance, is conducive to the fine processing of large workpieces, and can also greatly improve the efficiency of the pulse power supply. The modular design facilitates the expansion of power supply capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0016] Figure 1 is a circuit topology diagram of n chopper circuits connected in parallel in the present invention;

[0017] Figure 2 This is a schematic diagram of a control method for connecting n chopper circuits in parallel in the present invention;

[0018] Figure 3 Schematic diagram of carrier signals of n chopper circuits in the present invention;

[0019] Figure 4 This is the reference current pulse waveform diagram in the present invention. DETAILED DESCRIPTION

[0020] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0021] In the description of the present invention, if there is a description of first and second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0022] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0023] Example 1

[0024] like Figure 1As shown, a low-voltage high-power pulse power supply of the present invention adopts n chopper circuits in parallel, wherein the power switches S1, S2, and ┄S n Use power MOSFET.

[0025] Specifically:

[0026] The drain of the power switch S1 is connected to the positive electrode of the DC input power supply, and the source of the power switch S1 is connected to the cathode of the power diode D1 and one end of the inductor L1. The other end of the inductor L1 is connected to one end of the current sensor, whose output sampling current is i L1 The other end of the current sensor is connected to the output filter capacitor C o The anode of the power diode D1 is connected to the negative electrode of the DC input power supply, and the above connection circuit constitutes a first chopper circuit;

[0027] The drain of the power switch S2 is connected to the positive electrode of the DC input power supply. The source of the power switch S2 is connected to the cathode of the power diode D2 and one end of the inductor L2. The other end of the inductor L2 is connected to one end of the current sensor, whose output sampling current is i L2 The other end of the current sensor is connected to the output filter capacitor C o The anode of the power diode D2 is connected to the negative electrode of the DC input power supply, and the above connection circuit constitutes a second chopper circuit;

[0028] Similarly, the power switch S n The drain of the power switch S is connected to the positive terminal of the DC input power supply. n The source of each of the power diodes D n The cathode and inductance L n One end of the inductor L n The other end is connected to one end of the current sensor, and its output sampling current is i Ln The other end of the current sensor is connected to the output filter capacitor C o The anode of the power diode D n The anode of is connected to the negative electrode of the DC input power supply, and the above connection circuit constitutes the nth chopper circuit;

[0029] Filter capacitor C o The anode is also connected to one end of the output current sensor, and its output sampling current is i o The other end of the output current sensor is connected to one end of the load resistor R, and the other end of the load resistor R is connected to the negative electrode of the DC input power supply. The filter capacitor C o The cathode is also connected to the negative pole of the DC input power supply.

[0030] Example 2

[0031] A low-voltage, high-power pulse power supply control method of the present invention is specifically implemented according to the following steps:

[0032] Step 1, such as Figure 2 As shown, the output current reference value i oref and the actual output current feedback value i o The difference is controlled by the proportional integral (PI) regulator to obtain the feedback modulation coefficient d fk , the actual DC output voltage u o Divide by the DC input voltage u in Get the feedforward modulation coefficient d fw , the feedback modulation coefficient d fk and the feedforward modulation coefficient d fw The sum is represented by C1; the output current of one-nth is used as the reference value, which is represented by C2.

[0033] C2 minus the inductor current value i of the first chopper circuit L1 The difference is multiplied by the proportional coefficient K1 to obtain the current sharing modulation coefficient d m1 ; So the modulation coefficient of the first chopper circuit power switch is d1=C1+d m1 =d fk +d fw +d m1 ;

[0034] C2 minus the inductor current value i of the second chopper circuit L2 The difference is multiplied by the proportional coefficient K2 to obtain the current sharing modulation coefficient d m2 ; So the modulation coefficient of the second chopper circuit power switch is d2=C1+d m2 =d fk +d fw +d m2 ;

[0035] C2 minus the inductor current value i of the third chopper circuit L3 The difference is multiplied by the proportional coefficient K3 to obtain the current sharing modulation coefficient d m3 ; So the modulation coefficient of the power switch of the third chopper circuit is d3=C1+d m3 =d fk +d fw +d m3 ;

[0036] Similarly, C2 minus the inductor current value i of the nth chopper circuit Ln The difference is multiplied by the proportional coefficient K n , and obtain the current sharing modulation coefficient d mn ; So we can get the modulation coefficient d of the second chopper circuit power switch n =C1+d mn=d fk +d fw +d mn Among them, K1=K2=┄=K n .

[0037] Step 2, such as Figure 3 As shown, for n chopper circuits, the carrier phase shift technology is used, and the carrier signals for generating PWM waves are all sawtooth waves, and the carrier period is T s The carrier signal cf2 of the second chopper circuit lags behind the carrier signal cf1 of the first chopper circuit by T s / n, the carrier signal cf3 of the third chopper circuit lags behind the carrier signal cf1 of the first chopper circuit by 2Ts / n, the carrier signal cf4 of the fourth chopper circuit lags behind the carrier signal cf1 of the first chopper circuit by 3Ts / n, and so on. The carrier signal cf n It lags behind the carrier signal cf1 of the first chopper circuit by (n-1)Ts / n;

[0038] like Figure 4 As shown, the desired output current pulse waveform is: in one output current pulse period T o Internal, 0~t on The output current reference value during the time period is I o , t on ~T o The output current reference value is 0 during the time period; the following T o Repeat the above desired output current pulse waveform over and over again; change I o You can change the output pulse current size and change T o The pulse current frequency can be output by changing t on The output pulse current width can be changed;

[0039] Therefore, the modulation signal d1 of the first chopper circuit is compared with the corresponding carrier signal cf1 to obtain the PWM signal pwm1; the expected output current pulse period is T o , T o Much larger than T s , the output current pulse width is t on , and 2T s ≤t on ≤T o , convert the expected output current pulse into a logic level signal. The expected output current pulse amplitude is I o When the output current pulse amplitude is expected to be zero, it corresponds to a high level. oPerform a "logical AND" operation with pwm1 to obtain the control signal g1 of the first chopper circuit power switch S1, thereby controlling the first chopper circuit power switch to operate;

[0040] The modulation signal d2 of the second chopper circuit is compared with the corresponding carrier signal cf2 to obtain the PWM signal pwm2; similarly, the high and low level signals T o Perform a "logical AND" operation with pwm2 to obtain the control signal g2 of the second chopper circuit power switch S2, thereby controlling the second chopper circuit power switch to operate;

[0041] Similarly, the modulation signal d of the nth chopper circuit n The corresponding carrier signal cf n Compare and get the PWM signal pwm n ; Similarly, the high and low level signals T o with pwm n Perform a "logical AND" operation to obtain the nth chopper circuit power switch S n The control signal g n , thereby controlling the nth chopper circuit power switch to operate.

[0042] Therefore, compared with the existing technology, a low-voltage, high-power pulse power supply and control method are invented. Based on an n-way parallel chopper circuit, the output current feedback control, output voltage feedforward control and inductor current equalization control are combined to obtain a new pulse current control method. This control method is simple, reliable and easy to implement. It can realize medium and low frequency current pulses, output large current and resist load current disturbances. It has excellent dynamic and static performance, is conducive to the fine processing of large workpieces, and can also greatly improve the efficiency of the pulse power supply. The modular design facilitates the expansion of power supply capacity.

[0043] The foregoing description shows and describes several preferred embodiments of the invention. However, as previously stated, it should be understood that the invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the invention is applicable to various other combinations, modifications, and environments and is capable of modification within the scope of the inventive concept described herein, through the teachings above, or through techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims

1. A low-voltage, high-power pulse power supply control method, characterized in that: It is realized based on a low-voltage high-power pulse power supply, and the low-voltage high-power pulse power supply includes n A chopper circuit, n The DC input side and the DC output side of the chopper circuit of each branch are respectively connected in parallel, the DC input side is connected to the same DC input voltage, and the DC output side is connected in parallel to the filter capacitor and the load resistor; No. n A chopper circuit includes a power switch S n , power diode D n 、Inductor L n and current sensors, where n Means: 1, 2, 3..., n ; Among them: power switch S n The drain of the power switch S is connected to the positive terminal of the DC input power supply. n The source of each of them is connected to the power diode D n The cathode and inductance L n One end of the inductor L n The other end is connected to one end of the current sensor, and its output sampling current is i Ln The other end of the current sensor is connected to the output filter capacitor C o The anode of the power diode D n The anode of the filter capacitor C is connected to the negative electrode of the DC input power supply; o The anode of is also connected to one end of the output current sensor. The output sampling current of the output current sensor is i o , the other end of the output current sensor is connected to the load resistor R One end is connected to the load resistor R The other end is connected to the negative pole of the DC input power supply, and the filter capacitor C o The cathode is also connected to the negative pole of the DC input power supply; Please follow the steps below to implement: Step 1: Output current reference value i oref and actual output current feedback value i o The difference is controlled by the proportional integral regulator to obtain the feedback modulation coefficient d fk , by the actual DC output voltage u o Divide by the DC input voltage u in Get the feedforward modulation coefficient d fw , the feedback modulation coefficient d fk and the feedforward modulation coefficient d fw The sum is represented by C1; n One-third of the output current is taken as the reference value, represented by C2; C2 minus the n The inductor current value of a chopper circuit i Ln The difference is multiplied by the proportional coefficient K n , and obtain the current sharing modulation coefficient d mn , so the modulation coefficient of the nth chopper circuit power switch can be obtained d n = C1+ d mn = d fk + d fw + d mn ; Step 2, for n A chopper circuit uses carrier phase shift technology to generate PWM waves with sawtooth signals and a carrier period of T s ;No. n The carrier signal cf of the chopper circuit n lags behind the carrier signal cf1 of the first chopper circuit ( n -1)Ts / n ; The desired output current pulse waveform is: In one output current pulse period T o Inner, 0~t on The output current reference value during the time period is I o , t on ~T o The output current reference value is 0 during the time period; the following T o Repeat the above desired output current pulse waveform over and over again; change I o You can change the output pulse current size and change T o The pulse current frequency can be output by changing t on The output pulse current width can be changed; No. n The modulation signal of a chopper circuit d n The corresponding carrier signal cf n Compare and get the PWM signal pwm n ; The expected output current pulse period is T o , T o Much larger than T s , the output current pulse width is t on , and 2T s ≤t on ≤T o , convert the expected output current pulse into a logic level signal. The expected output current pulse amplitude is I o When the output current pulse amplitude is zero, it corresponds to a high level. The high and low level signals T o with pwm n Perform "logical AND" operation to get n A chopper circuit power switch S n The control signal g n , thereby controlling the n A chopper circuit power switch operates.

2. The low-voltage, high-power pulse power supply control method according to claim 1, characterized in that: The power switch is a power MOSFET.

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