Method and device for improving output current precision of constant-current Buck circuit

Abstract

The invention discloses a method for improving the output current precision of a constant-current Buck circuit. The method comprises the following steps: receiving measured first and second actual output average currents corresponding to first and second theoretical output average currents respectively; respectively calculating absolute errors between the first and second actual output average currents and the first and second theoretical average currents; respectively calculating a first actual inductance value and a second actual inductance value corresponding to the first theoretical outputaverage current and the second theoretical output average current; calculating an actual inductance value corresponding to the expected target output average current; calculating a peak-to-peak current; calculating a corrected peak current; and controlling the constant-current Buck circuit to work according to the corrected peak current and the product of the given output voltage of the constant-current Buck circuit and the turn-off time of the switching tube. The invention further discloses a device for improving the output current precision of a constant-current Buck circuit. According to the invention, the relative error between the actual output average current of the constant-current Buck circuit and the expected target output average current can be reduced.

Description

technical field [0001] The invention relates to constant current drive circuit technology. Background technique [0002] A step-down chopper circuit, also called a Buck converter (Buck Converter), can convert an input direct current into an output direct current whose voltage is adjustable and not higher than the input voltage. figure 1 A schematic diagram of the circuit principle of the LED lighting driving circuit using the Buck constant current output mode is shown. The LED lighting driving circuit includes a constant current Buck circuit, an output current sampling circuit, a peak-to-peak current control circuit, an SPI register and an MCU. The constant current Buck circuit includes a switch tube Q1 (for example, a MOS tube can be used as the switch tube Q1 ), an inductor L and a freewheeling diode D. The output terminal of the constant current Buck circuit is connected with the LED. [0003] In order to realize the constant current drive of the LED, control the outpu...

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Problems solved by technology

[0022] There is no feedback loop in the LED lighting drive circuit of the Buck constant current output mode, and the peak-to-peak current control circuit cannot control the actual output average current in the open-loop state

In addition, the current passing through the inductor causes the inductance to change, and the influence of the diode voltage on the peak-to-peak current will cause the relative error of the actual output average current to be greater than 5%.

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