Tandem type high-voltage pulse power supply for controlling switch transient trajectory to reduce electromagnetic interference

Abstract

The invention provides a tandem type high-voltage pulse power supply and a method for reducing electromagnetic interference through a control switch transient trajectory thereof, and belongs to the technical field of power electronic conversion. A tandem type high-voltage pulse power supply is commonly used in the field of industrial manufacturing and is high-power power electronic equipment. According to the invention, by controlling the switch conduction time of the series power device group, the function fitting of the switch transient trajectory is realized, and the traditional single-slope rising transient trajectory is fitted into the S-shaped transient trajectory, so that the amplitude spectrum of the switch waveform under high frequency is effectively reduced, and the electromagnetic anti-interference capability of the series high-voltage pulse power supply is improved. According to the invention, the electromagnetic interference of the tandem high-voltage pulse power supply is reduced through a low-cost switch transient trajectory control method, and the high-quality high-voltage pulse waveform with adjustable width can be output.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic conversion, and specifically relates to a series high-voltage pulse power supply, and proposes a method for controlling the transient trajectory of a switch to reduce electromagnetic interference generated during the switching process. Background Art

[0002] High-voltage pulse power supplies are widely used in the field of industrial manufacturing. For example, lasers, food sterilization, or environmental treatment applications all require high-voltage pulse power supplies to generate narrow pulse waveforms with fast voltage rise and fall. Common high-voltage pulse power supplies generally use a flyback topology to generate high voltage and control the pulse width output. The series-connected high-voltage pulse power supply uses power devices in series to output high-voltage pulses with adjustable width in a simple control method, and has a shorter voltage change time.

[0003] However, the rapid changes in voltage and current make power devices the source of high-frequency noise electromagnetic interference. In order to improve the electromagnetic anti-interference ability of high-voltage pulse power supplies and meet the electromagnetic compatibility standards of industrial equipment, there are usually two strategies to solve the problem of high-frequency electromagnetic interference. On the one hand, electromagnetic interference is suppressed by shielding the high-frequency noise in the propagation path, such as adding electromagnetic interference filters or electromagnetic shielding covers made of special materials. This means that additional devices need to be introduced for high-voltage pulse power supplies, which not only increases the cost but also reduces the power density of high-voltage pulse power supplies. On the other hand, the noise source of high-frequency electromagnetic interference is directly suppressed by controlling the switching process of power devices. The main noise sources of electromagnetic conduction interference of high-voltage pulse power supplies are switching frequency harmonics and switching transient noise, both of which can be characterized by switching waveforms. Therefore, the electromagnetic interference of high-voltage pulse power supplies can be suppressed from the source by changing the switching transient trajectory of power devices. The existing switching transient trajectory control strategy controls the switching waveform of a single power device, and requires an additional closed-loop control circuit to realize active control of the switching transient trajectory. Summary of the invention

[0004] In order to address the shortcomings in the background technology, the present invention proposes a series high-voltage pulse power supply that controls the transient trajectory of the switch to reduce electromagnetic interference. The proposed series high-voltage pulse power supply has a simple topology structure and can accurately output the high-voltage pulse waveform required by the load. The proposed method of controlling the transient trajectory of the switch to reduce electromagnetic interference does not require additional costs, and suppresses high-frequency electromagnetic interference from the source, which can effectively reduce the amplitude spectrum of the switching waveform in the high-frequency band, thereby ensuring the electromagnetic anti-interference capability of the high-voltage pulse power supply.

[0005] In order to achieve the above-mentioned object of the invention, the specific technical solution proposed by the present invention is as follows:

[0006] A series high-voltage pulse power supply for controlling the transient trajectory of a switch to reduce electromagnetic interference, characterized in that the series high-voltage pulse power supply comprises: a series power device group, a drive signal delay unit, N gate drive units, N voltage-equalizing buffer units, N-1 auxiliary diodes and a self-equalizing resistor R, where N is a natural number greater than or equal to 2;

[0007] The series power device group is formed by connecting N power devices of the same model in series;

[0008] The drive signal delay unit uses FPGA as the control core, executes the switch transient trajectory control strategy, delays the gate drive signal, and sends the gate drive signal to the gate drive unit to achieve the switch transient trajectory control of the series power device to reduce the electromagnetic interference during the switching process of the power device;

[0009] The N gate drive units are connected one by one to the gates of the N power devices in the series power device group, providing specific switch control signals to control the connected power devices to be turned on and off, so as to realize the pulse output of the series high-voltage pulse power supply;

[0010] The N voltage-sharing buffer units are connected in parallel with the drain-source of each power device, and are used to absorb the overvoltage generated by each power device during the switching process, so as to ensure that the operating voltage of each power device does not exceed the rated voltage; the voltage-sharing buffer unit includes a voltage-sharing diode and a voltage-sharing capacitor;

[0011] The N-1 auxiliary diodes are connected in parallel with the voltage-grading capacitors in the first N-1 voltage-grading buffer units to provide a current path for all the voltage-grading capacitors to achieve voltage balancing of the voltage-grading capacitors;

[0012] The self-voltage balancing resistor R is connected in parallel with the voltage balancing capacitor in the first voltage balancing buffer unit to consume the excess energy generated during the voltage balancing process;

[0013] Furthermore, the anode of the voltage-equalizing diode in the voltage-equalizing buffer unit is connected to the drain of the corresponding power device. When the power device is turned on with a delay to generate a high voltage, the voltage-equalizing diode is turned on and the excess charge is transferred to the voltage-equalizing capacitor connected to the cathode of the voltage-equalizing diode, thereby ensuring that the turn-off voltage of the power device remains at the desired voltage:

[0014]

[0015] Furthermore, the N auxiliary diodes work when the series power device group is turned on, so that the excess charge in each voltage balancing capacitor is transferred to the voltage balancing capacitor in the first voltage balancing buffer unit through the auxiliary diode, thereby realizing self-voltage balancing of the series power device group;

[0016] Furthermore, the self-equalizing resistor R and the equalizing capacitor in the first equalizing buffer unit form an RC absorption loop to prevent the voltage on the equalizing capacitor from exceeding the rated voltage;

[0017] Furthermore, the series high-voltage pulse input end is a DC high voltage, and by controlling the conduction and shutdown of the series power device group, a high-voltage pulse with adjustable pulse width, fast voltage change and low electromagnetic interference is sent to the load.

[0018] Another object of the present invention is to provide a method for controlling a switch transient trajectory to reduce electromagnetic interference, comprising the following steps:

[0019] 1) According to the switching transient trajectory control strategy, determine the specific switching time point t of the N power devices in the series power device group s1 ~t si ;

[0020] 2) Setting a specific switching time point of the series power device group in the driving signal delay unit, taking the switching time point of the first power device as a reference, generating a signal with different delay times t d The gate drive signal is sent to the gate drive unit;

[0021] 3) The gate drive unit receives signals with different delay times t d The gate drive signal controls the corresponding power device to turn on and off. The time point of each power device turning on and off is a specific time point calculated by the switch transient trajectory control strategy, so that the switch transient trajectory of the series power device group is controlled to be an "S" type transient trajectory waveform. The amplitude spectrum of the "S" transient trajectory waveform is effectively reduced in the high frequency range, thereby reducing electromagnetic interference;

[0022] Furthermore, in step 1), a specific switching time point t of the N power devices in the series power device group is determined. s1 ~t si The specific contents are as follows:

[0023] The switching waveform of the power device is an ideal trapezoidal wave, and the single slope function model expression in the voltage rising stage is:

[0024]

[0025] Where V DS is the drain-source voltage of the power device, V DC is the input voltage, Indicates the expected voltage after the power device is turned off, t r is the voltage rise time of the power device;

[0026] For N power devices, there are N specific switching time points ts1 ~t si , for a series power device group, N specific switching time points t s1 ~t si Corresponding to 2N key time points of the switching waveform t1~t i And 2N key switch waveform voltage nodes v1~v i , the function model expression of the switching transient trajectory is:

[0027]

[0028] t i , v i is the key time point and voltage node of the switching transient trajectory, and the specific switching time point t si And the voltage rise time t of the power device r There is also the shutdown voltage of the power device Jointly determine the key time point t of the first N switching transient trajectories i The specific switching time point t of the power device si Determine the critical time point t of the next N switching transient trajectories i is the corresponding specific switching time point t si Plus the voltage rise time t of the power device r ; Critical voltage node v i The superposition of the ideal trapezoidal wave for each shutdown;

[0029] The functional model expression of the “S” type transient trajectory is:

[0030]

[0031] Among them, σ t Represents the smoothness of the "S" type transient trajectory waveform. The “S” type transient trajectory keeps the voltage rise time of the series power device group within an acceptable range;

[0032] In order to control the switching transient trajectory to an "S"-shaped transient trajectory, it is necessary to approximate the key switching waveform voltage node with the function of the "S"-shaped transient trajectory, so that the switching transient trajectory waveform of the series power device group is similar to the "S"-shaped trajectory. The cost function of fitting the switching transient trajectory function v(i) of the series power device with the "S"-shaped transient trajectory is expressed as:

[0033]

[0034] The constraints are:

[0035] t si <t s(i+1) ;t sN -tsi <t r ; 1≤i≤N; t s1 =0

[0036] Solving the minimum value of the above constrained nonlinear function can obtain the N specific switching time points t that make the switching transient trajectory of the series power device group closest to the "S" type transient trajectory. s1 ~t si , where t s1 =0, that is, the switching time point of the first power device is used as the benchmark.

[0037] Furthermore, in step 2), the N driving signals generated by the driving signal delay unit have different delay times t d , the specific expression is:

[0038] t di =t si .

[0039] The series power device group is a voltage-driven device, including IGBT or MOSFET.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) Compared with the existing high-voltage pulse power supply, the present invention has a simpler series topology structure, significantly reduces the application cost, and can output a more accurate high-voltage pulse waveform.

[0042] (2) Compared with the existing power device series voltage balancing technology, the present invention can achieve voltage self-balancing based on voltage clamping without the need for complex series voltage balancing control methods.

[0043] (3) The present invention proposes a switching transient trajectory control method for reducing electromagnetic interference based on the series connection of power devices. No additional electromagnetic interference filter or shielding cover is required, the impact of electromagnetic interference is reduced from the noise source, and the electromagnetic anti-interference capability of the series high-voltage pulse power supply is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic topological diagram of a series high-voltage pulse power supply provided by the present invention.

[0045] Figure 2 A schematic diagram of the voltage clamping process of a power device of a series high-voltage pulse power supply provided by the present invention.

[0046] Figure 3 A schematic diagram of a self-balancing process of the voltage of a voltage-equalizing capacitor of a series high-voltage pulse power supply provided by the present invention.

[0047] Figure 4The present invention provides an RC absorption circuit composed of a self-equalizing resistor and an equalizing capacitor of a series high-voltage pulse power supply.

[0048] Figure 5 It is the ideal switching waveform of the power device.

[0049] Figure 6 Schematic diagram of the transient trajectory of the switching waveform of four power devices connected in series.

[0050] Figure 7 This is a comparison diagram between the “S” type transient trajectory and the single slope rising transient trajectory.

[0051] Figure 8 This is a comparison diagram of the amplitude spectra of the “S” type transient trajectory and the single slope rising transient trajectory. DETAILED DESCRIPTION

[0052] In order to describe the present invention in more detail and to present the purpose, technical solutions and advantages of the present invention more clearly, the present invention is further described in detail below with reference to the accompanying drawings.

[0053] like Figure 1 As shown, the present invention provides a series high-voltage pulse power supply, the power supply topology includes a series power device group, a drive signal delay unit, N gate drive units, N voltage balancing buffer units, N-1 auxiliary diodes and a self-voltage balancing resistor R, N is a natural number greater than or equal to 2. Wherein, V in is the high voltage power supply, R o For load.

[0054] The functions of the gate driving unit, the voltage balancing buffer unit, the auxiliary diode and the self-voltage balancing resistor are as follows:

[0055] The drive signal delay unit uses FPGA as the control core, executes the switch transient trajectory control strategy, delays the gate drive signal, and sends the gate drive signal to the gate drive unit to achieve switch transient trajectory control of the series power device to reduce electromagnetic interference during the switching process of the power device.

[0056] The gate drive unit provides a specific switch control signal for the corresponding power device, controls the connected power device to turn on and off, so as to realize the pulse output of the series high-voltage pulse power supply.

[0057] Each voltage balancing buffer unit includes a voltage balancing diode D i And a voltage balancing capacitor C i Used to absorb the overvoltage generated by each power device during the switching process to ensure that the operating voltage of each power device does not exceed the rated voltage.

[0058] Auxiliary diode D SiProvide a current path for all the grading capacitors to achieve voltage balance of the grading capacitors.

[0059] The self-equalizing resistor R is used to consume the excess energy generated during the voltage balancing process.

[0060] like Figure 2 The figure shows the voltage clamping process of the power device of the series high-voltage pulse power supply. In the most extreme case, only the first power device is turned on in advance, and the other power devices are in the off state. When the first power device is turned on in advance, the load current flows through the power device. At this time, the other power devices are not fully turned on. The load current passes through the voltage-equalizing diode to make the excess charge generated by the delayed turn-on of the power device flow into the corresponding voltage-equalizing capacitor, and the corresponding power device voltage is clamped to ensure that the working voltage of the power device does not exceed the rated voltage.

[0061] The voltage self-balancing process of the voltage balancing capacitor is as follows: Figure 3 As shown in the figure, when all power devices are fully turned on, the high voltage input power supply directly outputs pulses for the load. Since the series power devices are not turned on at the same time, the voltages of the corresponding voltage-equalizing capacitors are unbalanced, and the excess charge passes through the auxiliary diode D S1 ~D Si Flows into the first grading capacitor C1. Different grading capacitors have different grading circuits until the voltage of each grading capacitor Ci is balanced, completing the voltage self-balancing process of the grading capacitor.

[0062] like Figure 4 As shown, the first voltage-equalizing capacitor Ci and the self-equalizing resistor R form an RC loop, which consumes the excess charge accumulated on C1 in a passive consumption manner, thereby achieving voltage self-balancing of the series high-voltage pulse power supply.

[0063] like Figure 5 As shown, the switching waveform of the power device is an ideal trapezoidal wave, and the single slope function model expression in the voltage rising stage is:

[0064]

[0065] Where V DS is the drain-source voltage of the power device, V DC is the input voltage, It indicates the expected equilibrium voltage after the power device is turned off, t r is the voltage rise time of the power device.

[0066] To more clearly illustrate the method of controlling the transient state of the switch to suppress electromagnetic interference provided by the invention, four power devices are connected in series, such as Figure 6 For the four power devices, there are four specific switching time points t s1 ~t s4, for the series power device group, 4 specific switching time points t s1 ~t s4 Corresponding to the eight key time points t1 to t8 of the switching waveform and the eight key voltage nodes v1 to v8 of the switching waveform, the function model expression of the switching transient trajectory is:

[0067]

[0068] t i , v i is the key time point and voltage node of the switching transient trajectory, and the specific switching time point t si And the voltage rise time t of the power device r There is also the shutdown voltage of the power device Jointly determine the key time points t of the first four switching transient trajectories i The specific switching time point t of the power device si Determine the critical time point t of the last four switching transient trajectories i is the corresponding specific switching time point t si Plus the voltage rise time t of the power device r ; Critical voltage node v i The superposition of the ideal trapezoidal waveform for each shutdown.

[0069] In order to control the switching transient trajectory to an "S"-shaped transient trajectory, it is necessary to approximate the key switching waveform voltage node with the function of the "S"-shaped transient trajectory, so that the switching transient trajectory waveform of the series power device group is similar to the "S"-shaped trajectory. The cost function of fitting the switching transient trajectory function v(i) of the series power device with the "S"-shaped transient trajectory is expressed as:

[0070]

[0071] The constraints are:

[0072] t si <t s(i+1) ;t sN -t si <t r ; 1≤i≤N; t s1 =0

[0073] The function model expression of the "S" type transient trajectory is:

[0074]

[0075] σ t Represents the smoothness of the "S" type transient trajectory waveform. The "S"-shaped transient trajectory keeps the voltage rise time of the series power device group within an acceptable range.

[0076] By solving the minimum value of the above constrained nonlinear function, the specific switching time point t of the N power devices in the series power device group can be determined. s1 ~t s4 Taking the switching time point of the first power device as the reference, let t s1 =0, generate with different delay time t d The gate drive signal is sent to the gate drive unit.

[0077] like Figure 7 As shown, when the gate drive unit receives signals with different delay times t d The gate drive signal controls the corresponding power device to turn on and off. The time point when each power device is turned on and off is a specific time point calculated by the switch transient trajectory control strategy, so that the single slope rising switch transient trajectory of the series power device group is controlled to be an "S" type transient trajectory waveform.

[0078] like Figure 8 As shown, the amplitude spectrum of the "S"-shaped transient trajectory waveform is effectively reduced in the high-frequency range, achieving effective reduction of electromagnetic interference of the series high-voltage pulse power supply.

[0079] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A series high-voltage pulse power supply that controls the transient trajectory of the switch to reduce electromagnetic interference. It is characterized in that The series high-voltage pulse power supply comprises: a series power device group, a drive signal delay unit, N gate drive units, N voltage-equalizing buffer units, N-1 auxiliary diodes and a self-equalizing resistor R, where N is a natural number greater than or equal to 2; The series power device group is formed by connecting N power devices of the same model in series; The drive signal delay unit uses FPGA as the control core, executes the switch transient trajectory control strategy, delays the gate drive signal, and sends the gate drive signal to the gate drive unit to achieve the switch transient trajectory control of the series power device to reduce the electromagnetic interference during the switching process of the power device; The N gate drive units are connected one by one to the gates of the N power devices in the series power device group, providing specific switch control signals to control the connected power devices to be turned on and off, so as to realize the pulse output of the series high-voltage pulse power supply; The N voltage-sharing buffer units are connected in parallel with the drain-source of each power device, and are used to absorb the overvoltage generated by each power device during the switching process, so as to ensure that the operating voltage of each power device does not exceed the rated voltage; the voltage-sharing buffer unit includes a voltage-sharing diode and a voltage-sharing capacitor; The N-1 auxiliary diodes are connected in parallel with the voltage-grading capacitors in the first N-1 voltage-grading buffer units to provide a current path for all the voltage-grading capacitors to achieve voltage balancing of the voltage-grading capacitors; The self-voltage-equalizing resistor R is connected in parallel with the voltage-equalizing capacitor in the first voltage-equalizing buffer unit to consume the excess energy generated during the voltage-equalizing process.

2. A series high-voltage pulse power supply for controlling the transient trajectory of a switch to reduce electromagnetic interference according to claim 1, It is characterized in that The anode of the voltage-equalizing diode in the voltage-equalizing buffer unit is connected to the drain of the corresponding power device. When the power device is turned on with a delay to generate a high voltage, the voltage-equalizing diode is turned on and the excess charge is transferred to the voltage-equalizing capacitor connected to the cathode of the voltage-equalizing diode, thereby ensuring that the turn-off voltage of the power device remains at the desired voltage:

3. A series high-voltage pulse power supply for controlling the transient trajectory of switches to reduce electromagnetic interference according to claim 1, It is characterized in that The N auxiliary diodes work when the series power device group is turned on, so that the excess charge in each voltage balancing capacitor is transferred to the voltage balancing capacitor in the first voltage balancing buffer unit through the auxiliary diode, thereby realizing self-voltage balancing of the series power device group.

4. A series high-voltage pulse power supply for controlling the transient trajectory of switches to reduce electromagnetic interference according to claim 1, It is characterized in that The self-voltage-equalizing resistor R and the voltage-equalizing capacitor in the first voltage-equalizing buffer unit form an RC absorption loop to prevent the voltage on the voltage-equalizing capacitor from exceeding the rated voltage.

5. A series high-voltage pulse power supply for controlling the transient trajectory of switches to reduce electromagnetic interference according to claim 1, It is characterized in that The series high-voltage pulse input terminal is a DC high-voltage power supply. By controlling the on and off of the series power device group, a high-voltage pulse with adjustable pulse width, fast voltage change and low electromagnetic interference is sent to the load.

6. A series high-voltage pulse power supply for controlling the transient trajectory of switches to reduce electromagnetic interference according to claim 1, Features: The method for controlling the transient trajectory of a switch to reduce electromagnetic interference comprises the following steps: 1) According to the switching transient trajectory control strategy, determine the specific switching time point t of the N power devices in the series power device group s1 ~t si ; 2) Setting a specific switching time point of the series power device group in the driving signal delay unit, taking the switching time point of the first power device as a reference, generating a signal with different delay times t d The gate drive signal is sent to the gate drive unit; 3) The gate drive unit receives signals with different delay times t d The gate drive signal controls the corresponding power device to turn on and off. The time point of each power device turning on and off is a specific time point calculated by the switch transient trajectory control strategy, so that the switch transient trajectory of the series power device group is controlled to be an "S" type transient trajectory waveform. The amplitude spectrum of the "S" transient trajectory waveform is effectively reduced in the high frequency range, thereby reducing electromagnetic interference.

7. A method for controlling the transient trajectory of a switch to reduce electromagnetic interference according to claim 2, It is characterized in that The specific content of step 1) is: The switching waveform of the power device is an ideal trapezoidal wave, and the single slope function model expression in the voltage rising stage is: Where V DS is the drain-source voltage of the power device, V DC is the input voltage, Indicates the expected voltage after the power device is turned off, t r is the voltage rise time of the power device; For N power devices, there are N specific switching time points t s1 ~t si , for a series power device group, N specific switching time points t s1 ~t si Corresponding to 2N key time points of the switching waveform t 1 ~t i and 2N key switching waveform voltage nodes v 1 ~v i , the function model expression of the switching transient trajectory is: t i , v i is the key time point and voltage node of the switching transient trajectory, and the specific switching time point t si And the voltage rise time t of the power device r There is also the shutdown voltage of the power device Jointly determine the key time point t of the first N switching transient trajectories i The specific switching time point t of the power device si Determine the critical time point t of the next N switching transient trajectories i is the corresponding specific switching time point t si Plus the voltage rise time t of the power device r ; Critical voltage node v i The superposition of the ideal trapezoidal wave for each shutdown; The functional model expression of "S" type transient trajectory is: Among them, σ t Represents the smoothness of the "S" type transient trajectory waveform. Make the "S" type transient trajectory keep the voltage rise time of the series power device group within an acceptable range; In order to control the switching transient trajectory to an "S"-shaped transient trajectory, it is necessary to approximate the key switching waveform voltage node with the function of the "S"-shaped transient trajectory, so that the switching transient trajectory waveform of the series power device group is similar to the "S"-shaped trajectory. The cost function of fitting the switching transient trajectory function v(i) of the series power device with the "S"-shaped transient trajectory is expressed as: The constraints are: t si <t s(i+1) ;t sN -t si <t r ;1≤i≤N Solving the minimum value of the above constrained nonlinear function can obtain the N specific switching time points t that make the switching transient trajectory of the series power device group closest to the "S" type transient trajectory. s1 ~t si , where t s1 =0, that is, the switching time point of the first power device is used as the benchmark.

8. A method for controlling the transient trajectory of a switch to reduce electromagnetic interference according to claim 2, It is characterized in that In step 2), the N driving signals generated by the driving signal delay unit have different delay times t d , the specific expression is: t di =t si 。 9. A series high-voltage pulse power supply for controlling the transient trajectory of switches to reduce electromagnetic interference according to claim 1, Features: The series power device group is a voltage-driven device, including IGBT or MOSFET.

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