Optimal efficiency tracking method for constant current power supply

Abstract

The invention relates to an optimal efficiency tracking method for a constant-current power supply, and belongs to the technical field of power supply control in a power electronic technology. According to the technical scheme, the method comprises the following steps: searching an optimal efficiency point through self-tuning of the switching frequency according to an inverse parabola relationship between the operation efficiency and the switching frequency of the synchronous Buck converter; and measuring an input current value by taking the switching frequency of the Mos tube as a reference quantity, and adjusting the driving frequency through a disturbance observation method to find a minimum value point of the input current so as to realize the optimal operation frequency. The beneficial effects of the invention are that through the closed-loop control of the switching frequency, the input current can be the lowest under the condition that the output is not changed, so that the maximum output efficiency is realized. And digital control is adopted, so that the rapidity and stability of efficiency optimization are ensured.

Description

Technical Field

[0001] The invention relates to an optimal efficiency tracking method of a constant current power supply, belonging to the technical field of power supply control in power electronics technology. Background Art

[0002] With the global energy shortage, energy saving, loss reduction and optimization of energy structure are extremely important. As a key bridge connecting energy production and energy use, power electronic converters play a particularly prominent role. With the miniaturization and integration of power electronic components, the performance and functional requirements of power electronic converters are constantly increasing. Power electronic converters should be especially worthy of attention of technicians in improving energy utilization efficiency.

[0003] The development of high-efficiency power conversion technology usually takes into account the matching selection of power devices, circuit structure optimization, and control method improvement. Suitable power devices are selected based on switching speed, on-resistance, withstand voltage level, loss characteristics, and operating temperature. Soft switching technology is used to reduce the loss of switching devices during the conversion process. Improved control methods are used to achieve precise power control and achieve optimal efficiency operation. Achieving maximum output efficiency and ensuring the rapidity and stability of efficiency optimization are technical problems that will be solved in this field in the future. Summary of the invention

[0004] The object of the present invention is to provide an optimal efficiency tracking method for a constant current power supply, which realizes the optimal operating efficiency by adjusting the switching frequency according to the inverse relationship between the operating efficiency and the switching frequency, and realizes the optimal operating efficiency under the same operating conditions.

[0005] The technical solution of the present invention is: an optimal efficiency tracking method for a constant current power supply, according to the inverse parabolic relationship between the operating efficiency and the switching frequency of a synchronous Buck converter, the efficiency optimum is sought through self-tuning of the switching frequency; the switching frequency of a MOS tube is used as a reference, the input current value is measured, and the driving frequency is adjusted through a disturbance observation method to find the minimum value point of the input current and achieve the optimal operating frequency.

[0006] It includes the following steps: ① Given an initial switching frequency for the converter, the corresponding PWM wave controls the on and off of the MOS tube. After a certain period, the input current value is sampled. When the output current is detected to be stable, the switching frequency is adjusted once, such as adding a constant A0, and then entering the next period for iteration, so that the current frequency is the frequency of the previous moment plus the constant A0; ②Use the current frequency as the switching frequency to control the on and off of the MOS tube. After a certain period, sample the input current value at this time and compare the two input currents. ③ According to the difference between the two input currents, the switching frequency is adjusted to minimize the input current and form a control closed loop.

[0007] The present invention aims to solve the problem that fixed switching frequency will reduce output efficiency. According to the mathematical relationship between switching frequency and output efficiency, the driving frequency of MOS tube is designed to be adjusted online adaptively to minimize input current and maximize output efficiency. This optimal efficiency self-tracking method based on Buck circuit seeks the efficiency optimum through self-tuning of switching frequency to achieve the optimal operating efficiency under the same working conditions.

[0008] The beneficial effect of the present invention is that through the closed-loop control of the switching frequency, the input current can be minimized while the output remains unchanged, thereby achieving the maximum output efficiency. The use of digital control ensures the rapidity and stability of efficiency optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is an optimal efficiency tracking control block diagram of an embodiment of the present invention; Figure 2 is a frequency-efficiency-current relationship curve diagram of the Buck converter according to an embodiment of the present invention; Figure 3 It is an optimal efficiency tracking logic diagram of an embodiment of the present invention; Figure 4 1 is a circuit diagram of a Buck converter according to an embodiment of the present invention; Figure 5 This is an input current sampling circuit diagram of an embodiment of the present invention; Figure 6 It is a circuit diagram of a power module based on Buck circuit optimal efficiency tracking control in an embodiment of the present invention; In the figure: a differential amplifier (subtractor) 111 and a voltage stabilizing protection circuit 112. DETAILED DESCRIPTION

[0010] The present invention will be further described below by way of examples with reference to the accompanying drawings.

[0011] An optimal efficiency tracking method for a constant current power supply seeks the optimum efficiency point by self-tuning the switching frequency according to the inverse parabolic relationship between the operating efficiency and the switching frequency of a synchronous Buck converter; the switching frequency of a MOS tube is used as a reference, the input current value is measured, and the driving frequency is adjusted by a disturbance observation method to find the minimum point of the input current and achieve the optimal operating frequency.

[0012] It includes the following steps: ① Given an initial switching frequency for the converter, the corresponding PWM wave controls the on and off of the MOS tube. After a certain period, the input current value is sampled. When the output current is detected to be stable, the switching frequency is adjusted once, such as adding a constant A0, and then entering the next period for iteration, so that the current frequency is the frequency of the previous moment plus the constant A0; ②Use the current frequency as the switching frequency to control the on and off of the MOS tube. After a certain period, sample the input current value at this time and compare the two input currents. ③ According to the difference between the two input currents, the switching frequency is adjusted to minimize the input current and form a control closed loop.

[0013] In the embodiments, refer to the attached Figure 1 , 3 , optimal efficiency tracking control block diagram, including; input current sampling unit, control unit, MOS tube driving unit, freewheeling unit, output current sampling unit, freewheeling inductor unit, filter capacitor unit and current control unit.

[0014] Process: First, set the initial switching frequency f=f0; if the output current is unstable, reset the initial switching frequency; if the output current is stable, ADC samples the input current I0; If f is not less than f0, adjust the switching frequency f=f+A0, and the ADC samples the input current I1. If I1 is greater than I0, adjust the switching frequency f=f-A0; if I1 is not greater than I0, continue to adjust the switching frequency f=f+A0 until I1 is greater than I0; If f is less than f0, directly adjust the switching frequency f=f-A0; ADC samples input current I2. If I2 is less than I0, the switching frequency f=f-A0 is adjusted. If I2 is not less than I0, the switching frequency f remains unchanged.

[0015] Refer to the attached Figure 4 Buck circuit. Figure 5 Sampling input resistance R in The voltage at both ends of the input resistor is subtracted through the differential amplifier (subtractor) 111, and the voltage is filtered and the sampling peak value is limited through the voltage stabilization protection circuit 112 to protect the ADC peripheral of the controller. The controller detects the value of the input current and uses the disturbance observation method to adjust the switching frequency of the MOS tubes VT1 and VT2 to achieve adaptive output of the switching frequency and increase efficiency.

[0016] In this embodiment, Figure 6Design a step-down DC-DC power supply module with large load current output, with a design size of 50mm*50mm*25mm, and parameter requirements; input voltage 48V, output current 20A continuously adjustable, and output voltage adaptive. All comparators use LM324 operational amplifiers, and MOS tubes VT1 and VT2 use CSD19531Q5A. The above control method and circuit design are used to design and experiment the power supply module. Finally, the adaptive setting of the switching frequency and the precise and stable control of the output current are achieved, with lower overall power consumption and higher efficiency. This method has high application prospects, good economic benefits, and certain promotion value.

Claims

1. A method for tracking the optimal efficiency of a constant current power supply, characterized in that: According to the inverse parabolic relationship between the operating efficiency and switching frequency of the synchronous Buck converter, the efficiency optimum is sought through self-tuning of the switching frequency; the switching frequency of the MOSFET is used as a reference, the input current value is measured, and the driving frequency is adjusted through the disturbance observation method to find the minimum input current point and achieve the optimal operating frequency.

2. The method for tracking the optimal efficiency of a constant current power supply according to claim 1, characterized in that It includes the following steps: ① Given an initial switching frequency for the converter, the corresponding PWM wave controls the on and off of the MOS tube. After a certain period, the input current value is sampled. When the output current is detected to be stable, the switching frequency is adjusted once, plus a constant A0, and then the next period is entered for iteration, so that the current frequency is the frequency of the previous moment plus the constant A0; ②Use the current frequency as the switching frequency to control the on and off of the MOS tube. After a certain period, sample the input current value at this time and compare the two input currents. ③ According to the difference between the two input currents, the switching frequency is adjusted to minimize the input current and form a control closed loop.

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