A high response speed BUCK power supply current feedforward control method and system

Abstract

The present invention provides a high-response speed BUCK power supply current feedforward control method and system, in the field of BUCK power supply control technology, including the following steps: collecting feedback voltage, feedback current and setting reference voltage; calculating reference current according to feedback voltage and reference voltage; calculating control signal one according to reference current and feedback current; using reference voltage as control signal two; calculating control signal three according to reference current; superimposing control signal one, control signal two and control signal three to generate duty cycle control signal Duty; adjusting the on and off time of switching device based on duty cycle control signal Duty to achieve stable control of output voltage. The duty cycle control signal is generated by superimposing control signal one, control signal two and control signal three to control the system, which can reduce the influence of inductor current fluctuation on the system and improve the response speed and signal stability of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of BUCK power supply control, and in particular relates to a high-response speed BUCK power supply current feedforward control method and system. Background Art

[0002] The BUCK circuit is a commonly used step-down DC regulated power supply circuit, which is usually used to convert high voltage to lower voltage. The traditional double closed-loop BUCK power supply control strategy often has disadvantages such as insufficient response speed and excessive system error when facing sudden load. In addition, due to the simultaneous action of the two loops, the existing traditional double closed-loop Buck circuit may cause more mutual interference when disturbance occurs, affecting the stability of the system. At the same time, it will also affect the response speed of the current loop as the inner loop, making the overall dynamic response speed of the system less than expected. Summary of the invention

[0003] In view of the above problems in the prior art, the purpose of the present invention is to provide a high-response speed BUCK power supply current feedforward control method, which generates a duty cycle control signal by superposition of control signal one, control signal two, and control signal three to control the system, thereby reducing the impact of inductor current fluctuations on the system and improving the response speed and signal stability of the system.

[0004] A high response speed BUCK power supply current feedforward control method comprises the following steps:

[0005] Collect feedback voltage V fdb , feedback current I Lfdb And set the reference voltage V ref ;

[0006] According to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref ;

[0007] According to the reference current I ref , feedback current I Lfdb The control signal 1 is obtained by calculation;

[0008] The reference voltage V ref As control signal 2;

[0009] According to the reference current I ref The control signal three is calculated;

[0010] The control signal 1, the control signal 2 and the control signal 3 are superimposed to generate a duty cycle control signal Duty;

[0011] The on and off time of the switch device is adjusted based on the duty cycle control signal Duty to achieve stable control of the output voltage.

[0012] Preferably, according to the feedback voltage V fdb , reference voltage V ref Calculate the error voltage V err , according to the error voltage V err And PI controller calculates the reference current I ref , where the transfer function of PI controller 1 is therefore,

[0013] Preferably, according to the reference current I ref , feedback current I Lfdb Calculate the error between the two, and then calculate the control signal 1 through PI controller 2, where the transfer function of PI controller 2 is Therefore, the control signal is

[0014] Preferably, the transfer function from the inductor current to the output voltage is H(S), where

[0015]

[0016] , so the control signal three is

[0017]

[0018] Preferably, the duty cycle control signal Duty is:

[0019]

[0020] The second object of the present invention is to provide a high response speed BUCK power supply current feedforward control system, comprising:

[0021] Input signal setting module, used to collect feedback voltage V fdb , feedback current I Lfdb , and set the reference voltage V ref ;

[0022] The reference current calculation module is used to calculate the current according to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref ;

[0023] A control signal generation module is used to generate a reference current I ref , feedback current I Lfdb Calculate control signal one;

[0024] The control signal generation module is used to generate a reference current I ref Calculate control signal three;

[0025] The duty cycle control signal generation module is used to superimpose control signal 1, control signal 2, and control signal 3 to generate a duty cycle control signal Duty, wherein control signal 2 is a reference voltage V ref .

[0026] Preferably, the reference current calculation module includes a PI controller 1, which converts the feedback voltage V fdb , reference voltage V ref The error voltage between V err Transmitted to PI controller 1 to obtain reference current I ref ,

[0027]

[0028] ,in is the transfer function of PI controller 1.

[0029] Preferably, the control signal generation module includes a PI controller 2, which converts the reference current I ref , feedback current I Lfdb The error between is transmitted to PI controller 2 to obtain control signal 1, which is in is the transfer function of PI controller 2.

[0030] Preferably, the control signal three is in The transfer function from inductor current to output voltage is H(S).

[0031] Preferably, the duty cycle control signal Duty is:

[0032]

[0033] The beneficial effects of the present invention are as follows: the high-response-speed BUCK power supply current feedforward control method and system generate a duty cycle control signal by superimposing control signal one, control signal two, and control signal three, and superimpose reference voltage feedforward compensation and inductor current feedforward compensation on the basis of the traditional dual-closed-loop BUCK power supply control method, thereby improving the dynamic response performance of the power supply system, improving the response speed and signal stability, reducing the impact of inductor current fluctuations on the system, improving the response speed and signal stability of the system, and reducing the overshoot when the system is disturbed, so that the power supply system is suitable for scenarios with high switching frequency and continuous and rapid load changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 is a control block diagram of voltage feed-forward compensation of the present invention;

[0036] Figure 2 is a circuit diagram of a BUCK circuit of the present invention;

[0037] Figure 3 It is a simulation model of voltage feed-forward compensation of the present invention;

[0038] Figure 4 It is a waveform diagram output by the voltage feedforward compensation simulation model of the present invention;

[0039] Figure 5 is an equivalent circuit diagram of the BUCK circuit of the present invention;

[0040] Figure 6 is a control block diagram of the inductor current feed-forward compensation of the present invention;

[0041] Figure 7 It is a simulation model of the inductor current feed-forward compensation of the present invention;

[0042] Figure 8 It is a waveform diagram output by the inductor current feedforward compensation simulation model of the present invention. DETAILED DESCRIPTION

[0043] Embodiment 1

[0044] A high response speed BUCK power supply current feedforward control method, such as Figure 1 As shown, reference voltage feed-forward compensation is added to the BUCK circuit control, thereby improving the dynamic response speed of the system, enabling the system to make adjustments according to changes in the load at the output end of the BUCK circuit, so that the output voltage is always controlled near the reference value.

[0045] The control process of the reference voltage feedforward compensation of the BUCK circuit specifically includes the following steps:

[0046] S1, collect feedback voltage V fdb , feedback current I Lfdb And set the required reference voltage V ref .

[0047] S2, according to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref , specifically, is the transfer function of PI controller 1.

[0048] S3, according to the reference current I ref , feedback current I Lfdb The control signal 1 is calculated and is: is the transfer function of PI controller 2.

[0049] S4, the reference voltage V ref As control signal 2, reference voltage V ref Feedforward compensation.

[0050] S5. Superimpose the control signal 1 and the control signal 2 to generate a duty cycle control signal; at this time, the duty cycle control signal is:

[0051]

[0052] S6, based on the duty cycle control signal, adjust the on and off time of the switch device to achieve the output voltage V out stability control.

[0053] Among them, S3 and S4 are performed simultaneously, and the corresponding duty cycle control signal is generated by the joint action of the control signal 1 and the control signal 2 to control the BUCK circuit.

[0054] Specifically, set Figure 2 The BUCK circuit shown is used to verify the effect of voltage feed-forward compensation. The BUCK circuit in this embodiment includes a voltage source, a MOS tube 1, a MOS tube 2, an inductor L1, a capacitor C1, a resistor R1 and a resistor R2.

[0055] Among them, the capacitor C1, the resistor R1, and the resistor R2 are connected in parallel, one end of the capacitor C1, the resistor R1, and the resistor R2 is connected to the inductor L1, and the other end is connected to the source of the switch tube 2. The other end of the inductor L1 is respectively connected to the source of the switch tube 1 and the drain of the switch tube 2, the drain of the switch tube 1 is connected to the positive electrode of the voltage source, and the source of the switch tube 2 is connected to the negative electrode of the voltage source.

[0056] It should be noted that the resistor R1 and the resistor R2 constitute a load resistor, wherein a switch S2 is connected between the resistor R2 and the inductor L1, and the connection and disconnection of the resistor R2 are controlled by the on-off of the switch S2, thereby achieving the purpose of adjusting the load.

[0057] The duty cycle control signal is used to control the on and off time of MOS tube 1 and MOS tube 2. MOS tube 1 is located on the main circuit of the circuit. When the duty cycle control signal controls MOS tube 1 to turn on, the voltage source flows through the inductor L1 and the load through MOS tube 1. At this time, the inductor current increases, the inductor stores energy, and the capacitor C1 discharges through the load to maintain the output voltage. When the duty cycle control signal controls MOS tube 1 to turn off, the current on the inductor L1 will not disappear immediately. At this time, MOS tube 2 is turned on, and the inductor L1 continues to supply power to the load and capacitor C1 through MOS tube 2. At this time, the inductor current gradually decreases, the inductor L1 gradually releases the stored energy, and the capacitor C1 continues to discharge through the load to maintain the output voltage.

[0058] Therefore, the output voltage V out The average value of the input voltage V in and the duty cycle D of the switching device. Ideally, V out =D×V in The output voltage V can be controlled by adjusting the duty cycle D. out size.

[0059] According to Figure 1 The control block diagram shown in the figure is constructed as follows Figure 3 The simulation model shown in FIG. 1 and FIG. 1B show a specific embodiment in which V is set dc =200V, R1=15Ω, R2=5Ω, L1=666.6μH, C1=470μF. After the simulation starts, the output voltage V out After stabilization, the resistor R2 is connected through the switch S2, and the output voltage V is observed after the load changes. out The waveform of the simulation result is as follows Figure 4 As shown in the waveform diagram.

[0060] according to Figure 4 It can be seen that this control method can make the output voltage V out The output voltage V out When it first rises to the reference value, the inductor current fluctuates greatly and has several consecutive zero crossings. out The time to stabilize is about 0.0045S.

[0061] Consider the effect of inductor current fluctuation on output voltage V out The output voltage V generated by the inductor current fluctuation is out The error value is introduced into the control loop to realize feedforward compensation of the inductor current, thereby improving the dynamic response speed of the system, optimizing the waveform of the inductor current, and further improving the stability of the output voltage.

[0062] Specifically, the equivalent circuit diagram of the BUCK circuit is as follows: Figure 5 As shown, in the Laplace domain, we have:

[0063]

[0064] Therefore, the transfer function H(s) from inductor current to output voltage is:

[0065]

[0066] Among them, the resistance R is the equivalent resistance of the load in the BUCK circuit.

[0067] like Figure 6 As shown, the inductor current feedforward feedback is added, and while the control signal 1 and the control signal 2 are obtained, according to the reference current I ref The control signal 3 is calculated, where the control signal 3 is

[0068] , control signal 1, control signal 2 and control signal 3 are superimposed to generate a duty cycle control signal Duty. At this time, the duty cycle control signal Duty is:

[0069]

[0070] Based on the duty cycle control signal Duty, the on and off time of the switch device can be adjusted to further increase the output voltage V out stability.

[0071] According to Figure 6 The control block diagram shown in the figure is constructed as follows Figure 7 The simulation model shown and in a specific embodiment are set to set V dc =200V, R1=15Ω, R2=5Ω, L1=666.6μH, C1=470μF. After the simulation starts, the output voltage V out After stabilization, connect resistor R2 through switch S2, adjust the load change, and observe the output voltage V out The waveform diagram of the simulation results is as follows Figure 8 As shown in the waveform diagram.

[0072] according to Figure 8 It can be seen that adding the inductor current feedforward compensation adjusted by the transfer function H(S) on the basis of the reference voltage feedforward compensation can greatly improve the response speed of the system, reduce the overshoot when the system is disturbed, and improve the stability of the system.

[0073] Specifically, contrast Figure 4 and Figure 8 It can be seen that the duty cycle control signal generated by superposition of control signal 1, control signal 2 and control signal 3 controls the BUCK circuit so that the output voltage Vout The stabilization time is shorter, thus speeding up the system response time, and at the same time, the inductor current is more stable.

[0074] Embodiment 2

[0075] A high response speed BUCK power supply current feedforward control system includes an input signal setting module, a reference current calculation module, a control signal generation module, a control signal generation module and a duty cycle control signal generation module. The input signal setting module is used to collect the feedback voltage V fdb , feedback current I Lfdb And set the reference voltage V ref .

[0076] The reference current calculation module is used to calculate the current according to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref . Specifically, Figure 6 As shown, the reference current I ref The calculation module includes a PI controller that converts the feedback voltage V fdb , reference voltage V ref The error voltage between V err Transmitted to PI controller 1 to obtain reference current I ref , specifically, is the transfer function of PI controller 1.

[0077] The control signal generation module is used to generate a reference current I ref , feedback current I Lfdb Calculate the control signal 1. Figure 6 As shown, the control signal generation module includes a PI controller 2, which converts the reference current I ref , feedback current I Lfdb The error between is transmitted to PI controller 2 to obtain control signal 1, where control signal 1 is is the transfer function of PI controller 2.

[0078] The control signal generation module is used to generate a reference current I ref Calculate control signal three. Specifically, control signal three is in is the inductor current to output voltage V out The transfer function is H(S).

[0079] The duty cycle control signal generation module is used to superimpose control signal 1, control signal 2, and control signal 3 to generate a duty cycle control signal Duty. Control signal 2 is a reference voltage V refTherefore, the duty cycle control signal Duty is

[0080]

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high response speed BUCK power supply current feedforward control method, characterized in that: The steps include: Collect feedback voltage V fdb , feedback current I Lfdb And set the reference voltage V ref ; According to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref ; According to the reference current I ref , feedback current I Lfdb The control signal 1 is obtained by calculation; The reference voltage V ref As control signal 2; According to the reference current I ref The control signal three is calculated; The control signal 1, the control signal 2 and the control signal 3 are superimposed to generate a duty cycle control signal Duty; The on and off time of the switch device is adjusted based on the duty cycle control signal Duty to achieve stable control of the output voltage.

2. The high response speed BUCK power supply current feedforward control method according to claim 1, characterized in that: According to the feedback voltage V fdb , reference voltage V ref Calculate the error voltage V err , according to the error voltage V err And PI controller calculates the reference current I ref , where the transfer function of PI controller 1 is therefore, 3. The high response speed BUCK power supply current feedforward control method according to claim 1, characterized in that: According to the reference current I ref , feedback current I Lfdb Calculate the error between the two, and then calculate the control signal 1 through PI controller 2, where the transfer function of PI controller 2 is Therefore, the control signal is 4. The high response speed BUCK power supply current feedforward control method according to claim 1, characterized in that: The transfer function from inductor current to output voltage is H(S), where Therefore, the control signal three is 5. The high response speed BUCK power supply current feedforward control method according to claim 1, characterized in that: The duty cycle control signal Duty is 6. A high response speed BUCK power supply current feedforward control system, characterized in that: include: Input signal setting module, used to collect feedback voltage V fdb , feedback current I Lfdb , and set the reference voltage V ref ; The reference current calculation module is used to calculate the current according to the feedback voltage V fdb , reference voltage V ref Calculate the reference current I ref ; A control signal generation module is used to generate a reference current I ref , feedback current I Lfdb Calculate control signal one; The control signal generation module is used to generate a reference current I ref Calculate control signal three; The duty cycle control signal generation module is used to superimpose control signal 1, control signal 2, and control signal 3 to generate a duty cycle control signal Duty, wherein control signal 2 is a reference voltage V ref .

7. The high response speed BUCK power supply current feedforward control system according to claim 6, characterized in that: The reference current calculation module includes a PI controller 1, which converts the feedback voltage V fdb , reference voltage V ref The error voltage between V err Transmitted to PI controller 1 to obtain reference current I ref , in is the transfer function of PI controller 1.

8. The high response speed BUCK power supply current feedforward control system according to claim 6, characterized in that: The control signal generation module includes a PI controller 2, which converts the reference current I ref , feedback current I Lfdb The error between is transmitted to PI controller 2 to obtain control signal 1, which is in is the transfer function of PI controller 2.

9. The high response speed BUCK power supply current feedforward control system according to claim 6, characterized in that: The control signal three is in The transfer function from inductor current to output voltage is H(S).

10. The high response speed BUCK power supply current feedforward control system according to claim 6, characterized in that: The duty cycle control signal Duty is:

Images