Backlight power supply control circuit and method

Abstract

The invention provides a backlight power supply control circuit and method. A feedback loop module samples an output voltage of a second secondary winding to obtain a sampling voltage and generates a feedback signal; the flyback control module controls the primary winding to store electric energy according to the feedback signal and transmits the electric energy to the first secondary winding; the constant-voltage constant-current control chip detects the winding voltage of the second secondary winding; if the winding voltage is larger than the voltage threshold value, the first MOS tube is controlled to be switched on, so that the first secondary winding supplies power to the LED array; if the winding voltage is smaller than or equal to the voltage threshold value, the first MOS tube is controlled to be switched off, so that the first secondary winding transmits the residual electric energy to the second secondary winding and outputs the residual electric energy to the load. In the scheme, the control chip and the MOS tube are used for controlling the flyback topology to output two paths of voltages, one path of constant-current power supply is used for supplying power to the LED array, and one path of constant-voltage power supply is used for supplying power to the load, so that the power loss caused by adopting more peripheral power devices is avoided, and the purposes of reducing energy loss, reducing the area of a PCB (Printed Circuit Board) and reducing the cost are achieved.

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