Control circuit and control method of primary side feedback constant current

Abstract

The invention discloses a control circuit and a control method of a primary side feedback constant current of a constant current actuator of an alternating current-direct current (AC-DC) light-emitting diode (LED). The control circuit comprises a power switch tube, a secondary current sampling circuit, an error amplifier, an integrator and a pulse width modulator, wherein the power switch tube controls the work of primary inductance in a discontinuous working mode, the secondary current sampling circuit takes samples of demagnetizing time of a secondary winding and the current peak value of the primary inductance through a primary side auxiliary winding and generates feedback signals corresponding to the average value of a secondary current in each switching period based on the demagnetizing time and the current peak value, the error amplifier amplifies the errors between reference voltage and the feedback signals of a sampling circuit of the secondary current, the integrator carries out integration on the value amplified by the error amplifier, and the pulse width modulator generates pulse width modulation signals to control the power switch tube to work based on the signals output by the integrator. The control circuit and the control method of the primary side feedback constant current improve a constant current effect of output currents, and achieves high-precision constant current control with high power factor control.

Description

technical field [0001] The invention belongs to the technical field of LED constant current drivers in AC-DC converters, and relates to a primary side feedback constant current control circuit with high power factor in a flyback converter and a control method thereof. Background technique [0002] At present, LED drivers usually need to meet the following requirements: output constant current, high power factor and electrical isolation. Among them, the output constant current is determined by the characteristics of the LED itself, the high power factor is to reduce the pollution of the driver to the public grid, and the electrical isolation is for safety considerations. Constant current is also a steady current, and the constant current system is a circuit system that stabilizes the output current or the output average current. The function of the constant current system is to stabilize the output current, no matter how the input voltage and output load change, the output ...

AI Technical Summary

Problems solved by technology

[0004]In this technology, the driving voltage MPWM controlled by the control chip controls the voltage of other nodes, thereby controlling the output current and making it stable. The control chip basically realizes the primary side constant current control and high power factor requirements, but the current chip can only basically meet the primary side constant current control and high power factor requirements, its actual effect is relatively poor, and it does not really realize constant current Function

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