A method for fast compensation control of output sudden change of direct current power supply

Abstract

This invention discloses a rapid compensation control method for sudden output changes in a DC power supply, applied to a switching power supply with power feedback control implemented in a programmatic manner. The method includes the following steps: when a sudden output current change in the switching power supply is detected, rapid compensation control is initiated, i.e., a corresponding control quantity is directly given based on the current output current value. This control quantity is used to adjust the output of the switching power supply to directly restore it to a defined range. This invention directly gives the corresponding output control quantity when a sudden output current change is detected, achieving one-step compensation for the output change. This prevents large fluctuations in the DC power supply when dealing with the erratic characteristics of various loads, such as large output voltage drops, load resets, or load damage, thereby improving the dynamic performance and reliability of the entire electronic system.

Description

Technical Field

[0001] This invention relates to a control method for power converters, and particularly to a method for implementing digital feedback control of power supplies using MCUs, DSPs, etc., in a programmed manner. Background Technology

[0002] In power supply applications, due to the unpredictable nature of the load, sudden increases or decreases in load can cause significant fluctuations in output voltage, potentially exceeding the power supply's normal output voltage range. This can lead to malfunctions or damage to electrical equipment. To ensure normal operation and prevent damage to electrical equipment, power supplies typically need to limit output voltage fluctuations within a normal range, ensuring that the output voltage does not exceed the specified limit when any load is connected. Therefore, power supplies generally have two feedback control loops: a slow feedback control loop that stabilizes the output voltage at a set value when the output voltage fluctuation does not exceed a set threshold, and a fast feedback control loop that quickly adjusts the output voltage back to the specified range when the output voltage fluctuation exceeds the set threshold. See [link to relevant documentation]. Figure 1 A slow feedback control loop acts as a fine-tuning mechanism, controlling the system output to the setpoint with zero steady-state error. A fast feedback control loop acts as a coarse-tuning mechanism, quickly bringing the system output voltage back to near the setpoint when large fluctuations occur. Currently, common fast feedback control loops simply adjust the control parameters of the slow feedback control loop to accelerate its adjustment rate. Figure 2 As shown, the adjustment time is relatively long, and the effect on controlling large fluctuations is limited. Summary of the Invention

[0003] Based on the above reasons, the purpose of this invention is to provide a method for rapid compensation control of sudden output changes in DC power supply. When a sudden change in output current is detected, this control method directly provides the corresponding output control quantity according to the value of the output current to perform one-step compensation for the sudden change in output.

[0004] This invention achieves its objective through the following technical solution: a method for rapid compensation control of sudden changes in DC power supply output, applied to a switching power supply that implements power feedback control in a programmed manner, characterized by comprising the following steps:

[0005] When a sudden change in the output current of the switching power supply is detected, fast compensation control is initiated. That is, a corresponding control quantity is directly given according to the current output current value. The control quantity is used to adjust the output of the switching power supply so that it directly recovers to the limited range. In other words, the output of the switching power supply is adjusted in one step.

[0006] As a preferred method: Output current surges are detected as follows: Let I0, I1, and I2 represent the output current of the switching power supply in the current, previous, and previous cycles, respectively. If:

[0007] ①If I0 minus I1 is greater than the set threshold, and I1 minus I2 is greater than the set threshold, then the output current is considered to have increased suddenly.

[0008] ②If I1 minus I0 is greater than the set threshold, and I2 minus I1 is greater than the set threshold, then the output current is considered to have suddenly decreased.

[0009] The control quantity is obtained from the Ctrl_Out[] array based on the current output current value. The Ctrl_Out[] array is used to store the control quantities corresponding to different output current values ​​when the switching power supply is in steady state.

[0010] When the sudden change condition is not met, the switching power supply operates in PID feedback control mode.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] When a sudden change in output current is detected, the present invention directly provides the corresponding output control quantity to achieve one-step compensation for the output change, which can greatly shorten the loop adjustment time and thus greatly reduce the overshoot and undershoot values ​​of the output voltage. This prevents the DC power supply from experiencing large fluctuations when dealing with the reckless characteristics of various loads, such as large output voltage drops, load resets, and load damage, thereby improving the dynamic performance and reliability of the entire electronic system. Attached Figure Description

[0013] Figure 1 Block diagram of the principle of ordinary DC power supply control method;

[0014] Figure 2 Characteristic curves of the output current I and control quantity Ctrl_Out of a normal DC power supply;

[0015] Figure 3 A schematic diagram of the control method of the present invention;

[0016] Figure 4 The characteristic curve of DC power supply output current I versus control quantity Ctrl_Out after using the control method of this invention;

[0017] Figure 5 Hardware circuit schematic diagram of the first application embodiment;

[0018] Figure 6 Flowchart of a method for rapid compensation control of sudden changes in DC power supply output. Detailed Implementation

[0019] To enable those skilled in the art to more readily understand the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0020] Figure 3 This is a block diagram illustrating the principle of the DC power supply output abrupt change rapid compensation control method of the present invention. Figure 4 This is a diagram illustrating the effect of the DC power supply output sudden change rapid compensation control method of the present invention.

[0021] The overall idea of ​​the control method of this invention is that, under normal circumstances, the switching power supply operates in a normal control state (i.e., Figure 3 The system employs PID feedback control and performs cycle-by-cycle detection of sudden changes in the output current. Once a sudden change in the output current of the switching power supply is detected, fast compensation control is initiated. In fast compensation control mode, the switching power supply directly assigns a corresponding control quantity based on the current output current value. This control quantity is used to adjust the output voltage or current of the switching power supply, ensuring that, under the adjustment of the control quantity, the output voltage or current of the switching power supply can be directly and instantly restored to the defined range.

[0022] When making a sudden change judgment, this invention chooses current instead of voltage because the output current responds faster when the load changes suddenly.

[0023] First Application Example

[0024] Appendix Figure 5 The hardware circuit schematic of the first embodiment shows that the power loop is a half-bridge LLC topology. U1 is a DSP chip used to generate the required PWM signals (PWM1A, PWM1B). The period and duty cycle of the PWM signals are directly controlled by the program in U1. The two complementary PWM signals generated by U1 with a duty cycle of 50% are isolated and enhanced by U2 to drive the complementary turn-on and turn-off of the two MOS on the upper and lower parts of one bridge arm, forming a high-voltage square wave with the required frequency and pulse width at the midpoint of the bridge arm.

[0025] The high-voltage square wave signal, after passing through the LLC circuit composed of Cr, Lr, and T1, outputs a near-sinusoidal voltage at the secondary side of T1. This voltage is then rectified by D2 and D4 to obtain a DC voltage containing high-frequency components. This DC voltage is further filtered by a filter composed of C2-C9 and L1, finally reaching the DC voltage at the Out terminal. The output port voltage Out+ passes through a low-pass filter and attenuation circuit composed of R14, R19, and C27 before being sent to pin 3 of U3A. U3A performs voltage following on this voltage and outputs it from pin-1 of U3A. The output voltage then passes through a low-pass filter composed of R16 and C26 before being sent to pin 18 of U1 for analog-to-digital conversion. The converted digital output voltage becomes the feedback quantity for the voltage control loop in the program. The output current is converted into a weak voltage signal by shunts Shunt1 and Shunt2. After passing through the differential amplifier and filter circuit composed of U3B, R6, R7, R8, R12, C13, and C14, it is converted into a larger voltage signal and output from pin 7 of U3B. After being filtered by the low-pass filter composed of R10 and C16, it is sent to pin 15 of U1. This voltage signal will be converted into a digital signal by the ADC inside U1, which becomes the input for current feedback control in the program.

[0026] Appendix Figure 6 The flowchart below illustrates the software control process in the first application embodiment, representing the implementation of the control method of this invention. This process runs once every set time interval (determined by the MCU performance; the time should be greater than twice the switching frequency), loading the final result into the hardware register of U1 to adjust the PWM signal pulse width or period (PWM mode adjusts the pulse width in time-based mode, PFM mode adjusts the period in time-based mode), thereby controlling the output voltage or current.

[0027] The current output current of the system is I0, the output current of the previous cycle is I1, and the output current of the cycle before that is I2. The Ctrl_Out[] array contains the pulse width or period value corresponding to different output current values ​​when the system is in steady state.

[0028] Upon entering the control flow, the system first checks whether the output current change satisfies either of the following conditions: "① If I0 minus I1 is greater than the set threshold, and I1 minus I2 is greater than the set threshold, then the output is considered to be increasing suddenly; ② If I1 minus I0 is greater than the set threshold, and I2 minus I1 is greater than the set threshold, then the output is considered to be decreasing suddenly." If either of these conditions is met, the corresponding control quantity is searched in Ctrl_Out[] based on the current output current I0 for output control. If neither of these conditions is met, the system exits the fast compensation control state and enters the normal control state.

Claims

1. A method for rapid compensation control of sudden changes in DC power supply output, applied to a switching power supply with power feedback control implemented in a programmed manner, characterized in that, Includes the following steps: When a sudden change in the output current of the switching power supply is detected, fast compensation control is activated, that is, a corresponding control quantity is directly given according to the current output current value. The control quantity is used to adjust the output of the switching power supply so that it directly recovers to the limited range. Output signal abrupt changes are detected as follows: Let I0, I1, and I2 represent the output current of the switching power supply in the current, previous, and previous cycles, respectively. If: ①If I0 minus I1 is greater than the set threshold, and I1 minus I2 is greater than the set threshold, then the output signal is considered to have increased suddenly; ②If I1 minus I0 is greater than the set threshold, and I2 minus I1 is greater than the set threshold, then the output signal is considered to have suddenly decreased.

2. The control method according to claim 1, characterized in that, The control quantity is obtained from the Ctrl_Out[] array based on the current output current value. The Ctrl_Out[] array is used to store the control quantities corresponding to different output current values ​​when the switching power supply is in steady state.

3. The control method according to claim 2, characterized in that, When the sudden change condition is not met, the switching power supply operates in PID feedback control mode.

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