A current ripple injection device for improving the stability of a cascaded power converter

Abstract

The present application relates to the technical field of cascade power converter, and especially relates to a current ripple injection device for improving the stability of a cascade power converter, comprising a front-stage converter, a control circuit, a rear-stage converter and a current ripple generator, the output end of the front-stage converter is connected with the input end of the control circuit and the input end of the rear-stage converter respectively, the connection point of the front-stage converter and the rear-stage converter is connected with the output end of the current ripple generator, the current ripple generated by the current ripple generator is injected into the input end of the rear-stage converter, the current ripple fed forward by the rear-stage converter is reduced or offset, thereby eliminating the influence of the current ripple fed forward by the rear-stage converter on the stability of the front-stage converter, and improving the stability of the cascade power converter. The present application is used for eliminating the influence of the current ripple fed forward by the rear-stage converter on the stability of the front-stage converter in the cascade power converter, and improving the stability of the cascade power converter.

Description

Technical Field

[0001] This invention relates to the field of cascaded power converter technology, and in particular to a current ripple injection device for improving the stability of cascaded power converters. Background Technology

[0002] Cascaded power converters, characterized by high efficiency, high power density, and high reliability, have been widely used in new energy power generation, electric vehicles, industrial control, and communications. With the continuous improvement of power supply technology, people have put forward increasingly higher requirements for the performance of cascaded power converters. In order to ensure the stable and reliable operation of cascaded power converters, how to improve their stability has always been a focus of attention.

[0003] In a cascaded power converter, the output of the preceding converter serves as the input of the following converter. Thus, the input voltage of the following converter is determined by the preceding converter, while the output current of the preceding converter is determined by the power required by the following converter. Simultaneously, the input current ripple of the following converter feeds forward to the output capacitor of the preceding converter, causing significant changes in the output capacitor current ripple and output voltage ripple of the preceding converter. For a preceding converter employing ripple control, the output capacitor current or output voltage is used as a feedback control signal to adjust the output voltage of the preceding converter. Therefore, the current ripple fed forward by the following converter will affect the stability of the cascaded power converter, narrowing the stable operating range of the preceding converter. Summary of the Invention

[0004] To address the shortcomings of existing algorithms, this invention aims to eliminate the impact of feedforward current ripple from the subsequent stage converter on the stability of the preceding stage converter in a cascaded power converter, thereby improving the stability of the cascaded power converter.

[0005] The technical solution adopted in this invention is: a current ripple injection device for improving the stability of a cascaded power converter, comprising: a pre-stage converter, a control circuit, a post-stage converter, and a current ripple generator. The output terminal of the pre-stage converter is connected to the input terminal of the control circuit and the input terminal of the post-stage converter, respectively. The connection point between the pre-stage converter and the post-stage converter is connected to the output terminal of the current ripple generator. The current ripple generated by the current ripple generator is injected into the input terminal of the post-stage converter, reducing or canceling the feedforward current ripple of the post-stage converter, thereby eliminating the influence of the feedforward current ripple of the post-stage converter on the stability of the pre-stage converter and improving the stability of the cascaded power converter.

[0006] Furthermore, the pre-converter includes: input 1, switching device 2, filtering device 3, and output 4. The control circuit includes: voltage detection device 6, reference voltage 7, comparator 8, clock 9, RS flip-flop 10, and drive circuit 11. Input 1 is connected to switching device 2, filtering device 3, and output 4 in sequence. Output 4 is connected to voltage detection device 6, comparator 8, RS flip-flop 10, drive circuit 11, and switching device 2 in sequence. Reference voltage 7 is connected to comparator 8, and clock 9 is connected to RS flip-flop 10.

[0007] Furthermore, the current ripple generator includes: input 12, switching device 13, inductor 14, current sampling device 15, reference current 16, comparator 17, clock 18, RS flip-flop 19, and drive circuit 20. Input 12 is connected in sequence to switching device 13, inductor 14, current sampling device 15, comparator 17, RS flip-flop 19, drive circuit 20, and switching device 13. Reference current 16 is connected to comparator 17, clock 18 is connected to RS flip-flop 19, and inductor 14 is connected to the subsequent converter.

[0008] Furthermore, the current signal sampled by the current sampling device 15 is compared with the reference current 16 to generate a reset signal for the RS flip-flop 19. The clock 18 (whose frequency is consistent with the operating frequency of the load converter) is used as the set signal for the RS flip-flop 19. The two output terminals of the RS flip-flop 19 are connected to the control terminals of the switching device 13 through the drive circuit 20 to control the switching device 13 to turn on and off, thereby realizing the output of current ripple. The amplitude of the current ripple generated by the current ripple generator is determined by the magnitude of the reference current 16.

[0009] Furthermore, comparators 8 and 17 use the LM319 chip.

[0010] Furthermore, RS flip-flop 10 and RS flip-flop 19 employ 74HC02.

[0011] Furthermore, drive circuit 11 and drive circuit 20 adopt IR2125 or IR2110.

[0012] The beneficial effects of this invention are:

[0013] It effectively eliminates the instability caused by the current ripple feedforward of the downstream converter in the upstream converter, and improves the stability of the cascaded power converter. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the current ripple injection device for improving the stability of cascaded power converters according to the present invention.

[0015] Figure 2 This is a schematic diagram of the circuit structure of the present invention;

[0016] Figure 3 This is a time-domain simulation waveform diagram of the output voltage, inductor current, control pulse signal and clock signal of the front-stage converter in the cascaded power converter of the present invention when voltage ripple control is adopted;

[0017] Figure 4 This is a time-domain simulation waveform diagram of the output voltage, inductor current, control pulse signal, and clock signal of the corresponding front-end converter of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0019] like Figure 1 As shown, a current ripple injection device for improving the stability of a cascaded power converter is described, such as... Figure 1 As shown in the figure, the circuit consists of a pre-stage converter, a post-stage converter, and a current ripple generator. Considering that this invention improves the stability of the pre-stage converter through current ripple injection, detailed structures of the main circuits and control circuits of the pre-stage converter and current ripple generator are provided, while the detailed structure of the post-stage switching converter is omitted. The long dashed box represents the power circuit of the pre-stage converter, including: input 1, switching device 2, filtering device 3, and output 4. Connections: Input 1 is connected to switching device 2, and after passing through switching device 2, the signal is transmitted to filtering device 3, and after the action of filtering device 3, it enters output 4. The short dashed box represents the control circuit of the pre-stage converter, including: voltage sampling device 6, reference voltage 7, comparator 8, clock 9, RS flip-flop 10, and drive circuit 11. Connections: Voltage sampling device 6 and reference voltage 7, connected to output 4, are respectively connected to the two input terminals of comparator 8; the output terminal of comparator 8 and clock 9 are connected to the two input terminals of RS flip-flop 10; the output terminal of RS flip-flop 10 is connected to drive circuit 11; drive circuit 11 is connected to switching device 2; furthermore, output 4 is connected to the post-stage converter 5.

[0020] The dashed box represents the current ripple generator. Its main circuit includes: input 12, switching device 13, and inductor 14. The input is connected to switching device 13, and after passing through 13, the current is transmitted to inductor 14. After passing through inductor 14, the current enters the output terminal of output 4 or the input terminal of the subsequent converter 5. Its control circuit includes: inductor current sampling device 15, reference current 16, comparator 17, clock 18, RS flip-flop 19, and drive circuit 20. The inductor current sampling device 15 and reference current 16, connected to the output terminal of inductor 14, are respectively connected to the two input terminals of comparator 17. Comparator 17 and clock 18 are connected to RS flip-flop 19. The input terminal of drive circuit 20 is connected to the output terminal of RS flip-flop 19. The output terminal of drive circuit 20 is connected to switching device 13.

[0021] The input current ripple of the subsequent converter 5 is fed forward to the output capacitor of the preceding converter, causing significant changes in the output capacitor current ripple and output voltage ripple of the preceding converter, thereby generating subharmonic oscillations. By adding a current ripple generator to the input terminal of the subsequent converter 5, the feedback voltage and current ripple of the subsequent converter 5 can be suppressed.

[0022] Figure 2 The circuit structure diagram of the Buck converter cascaded with the Boost converter of the present invention is shown.

[0023] The current ripple generator includes inductor L3, comparator 2, RS flip-flop 2, and MOSFETs S3 and S4. One end of L3 is connected to the input of the subsequent converter, and the other end is connected to the drain of S4. The connection point between the source of S4 and the drain of S3 is connected to the input of the subsequent converter. The S-terminal of RS flip-flop 2 is connected to the clock signal.

[0024] Next, the RS flip-flop The Q terminal is connected to the gates of S4 and S3 respectively. The R terminal of the RS flip-flop is connected to the output terminal of comparator 2. The inverting input terminal of comparator 2 is connected to the current sampling device. The non-inverting input terminal of comparator 2 is connected to the reference current.

[0025] Input 1 is a device used to provide the input voltage, the input voltage V. inThe voltage range is 6V-10V, and lithium batteries or storage batteries can be used; switching devices 2 and 13 can be power MOSFETs, IGBTs, etc. In this embodiment, power MOSFETs are used, preferably the IRF540; filtering device 3 can be a low-pass filter composed of an inductor and a capacitor, or a filter composed of a single inductor or a single capacitor. In this embodiment, a low-pass filter composed of an inductor and a capacitor is used as filtering device 3; voltage detection device 6 can be directly connected by a single wire or a voltage divider resistor; reference voltage 7 and reference current 16 can be provided by an auxiliary power supply or an adjustable voltage regulator chip. In this embodiment, an adjustable voltage regulator chip is used, preferably the LM117; comparators 8 and 17 use the LM319 chip; the signals of clock 9 and clock 18 are generated by a function signal generator; RS flip-flops 10 and 19 are built using 4-way 2-input NOR gates, preferably the 74HC02; driving circuit 11 and driving circuit 20 can use driving chips such as IR2125 or IR2110. In this embodiment, the IR2125 is preferred. Figure 1 The driving circuit 11 in the middle corresponds to Figure 2 Driver 1 in the middle, Figure 1 The driving circuit 20 in the middle corresponds to Figure 2 The drive circuit consists of drives 3 and 4; input 12 can be a lithium battery or a storage battery; the current acquisition device 15 can be implemented through a sampling resistor and a differential amplifier circuit. In this embodiment, the switching and filtering devices in the power circuit of the subsequent converter 5 are of the same type as those in the preceding converter, the control pulse is provided by a function signal generator, and the load resistor R is provided by a power resistor or an electronic load.

[0026] Simulation Result Analysis:

[0027] Figure 3 The following are time-domain simulation waveforms of the output voltage, inductor current, control pulse signal, and clock signal of the front-stage converter in a cascaded power converter without the present invention. Simulation circuit parameters: Input voltage V in =10V, reference voltage of the pre-converter V ref =3V, inductor L1 = 60μH, capacitor C1 = 470μF, capacitor equivalent series resistance ESR r1 = 100mΩ, subsequent converter inductor L2 = 100μH, capacitor C2 = 100μF, load R = 5Ω, clock signal clk1 period T S1 and clk2 period T S2 All values ​​are 10 μs with a duty cycle of 0.01. The horizontal axis represents time (ms), and the vertical axis represents voltage (V) or current (A). Figure 3 It can be seen that under the simulated circuit parameters, the front-end converter exhibits subharmonic oscillations and is in an unstable operating state.

[0028] Figure 4The time-domain simulation waveforms of the output voltage, inductor current, control pulse signal, and clock signal of the cascaded power converter after incorporating this invention are shown. A current ripple generator is introduced between the output of the pre-stage converter and the input of the post-stage converter. Its simulation circuit parameters are: inductor L3 = 40μH, input voltage E = 8V, and reference current I... ref = -0.25A, clock signal clk3 period T S3 =10μs, duty cycle 0.01, its relationship with simulation circuit parameters and Figure 3 Same. Put Figure 3 and Figure 4 The comparison shows that, under the same circuit parameters, after injecting current ripple, the operating state of the front-stage converter changed from an unstable state to a stable state, proving the feasibility of the device of the present invention. That is, the present invention can effectively eliminate the influence of the feedforward current ripple of the rear-stage converter on the stability of the front-stage converter, thereby improving the stability of the cascaded power converter.

[0029] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A current ripple injection device for improving the stability of a cascaded power converter, characterized in that, include: The system consists of a pre-converter, a control circuit, a post-converter, and a current ripple generator. The output of the pre-converter is connected to the input of the control circuit and the input of the post-converter, respectively. The connection point between the pre-converter and the post-converter is connected to the output of the current ripple generator. The current ripple generated by the current ripple generator is injected into the input of the post-converter to reduce or cancel the feedforward current ripple of the post-converter, thereby eliminating the impact of the feedforward current ripple of the post-converter on the stability of the pre-converter and improving the stability of the cascaded power converter. The current ripple generator includes: input 12, switching device 13, inductor 14, current sampling device 15, reference current 16, comparator 17, clock 18, RS flip-flop 19 and drive circuit 20. Input 12 is connected to switching device 13, inductor 14, current sampling device 15, comparator 17, RS flip-flop 19, drive circuit 20 and switching device 13 in sequence. Reference current 16 is connected to comparator 17. Clock 18 is connected to RS flip-flop 19. Inductor 14 is connected to the subsequent converter. The current signal sampled by the current sampling device 15 is compared with the reference current 16 to generate a reset signal for the RS flip-flop 19. The clock 18 is used as the set signal for the RS flip-flop 19, and the frequency of the clock 18 is consistent with the operating frequency of the subsequent converter 5. The two output terminals of the RS flip-flop 19 are connected to the control terminals of the switching device 13 through the drive circuit 20 to control the switching device 13 to turn on and off, thereby realizing the output of current ripple. The amplitude of the current ripple is determined by the magnitude of the reference current 16.

2. The current ripple injection device for improving the stability of a cascaded power converter according to claim 1, characterized in that, The pre-converter includes: input 1, switching device 2, filtering device 3 and output 4. The control circuit includes: voltage detection device 6, reference voltage 7, comparator 8, clock 9, RS flip-flop 10 and drive circuit 11. Input 1 is connected to switching device 2, filtering device 3 and output 4 in sequence. Output 4 is connected to voltage detection device 6, comparator 8, RS flip-flop 10 and drive circuit 11 and switching device 2 in sequence. Reference voltage 7 is connected to comparator 8 and clock 9 is connected to RS flip-flop 10.

3. The current ripple injection device for improving the stability of a cascaded power converter according to any one of claims 1 and 2, characterized in that, Comparator 8 and comparator 17 use the LM319 chip.

4. The current ripple injection device for improving the stability of a cascaded power converter according to any one of claims 1 and 2, characterized in that, RS flip-flop 10 and RS flip-flop 19 use 74HC02.

5. The current ripple injection device for improving the stability of a cascaded power converter according to any one of claims 1 and 2, characterized in that, The drive circuit 11 and drive circuit 20 use IR2125 or IR2110.

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