Backlight driving circuit, electronic device and backlight driving method

摘要

A backlight driving circuit includes a LED driving chip (10) for outputting a PWM signal, a power port (20), a voltage conversion unit (30), a first, a second, and a third switch unit (50, 60, 70), and a level conversion unit (40). The voltage conversion unit (30) includes a primary unit (31) and a secondary winding (32). The first switch unit (50) is connected to the power port (20) and the primary unit (31). The second switch unit (60), the secondary winding (32) and a first LED string (21) forms a first circuit loop (LP1). The first and the second switch unit (50, 60) are turned on or off when receiving the PWM signal. The third switch unit (70), the primary winding (31), and a second LED string (22) form a second circuit loop (LP2). The voltage conversion unit output a reversed PWM signal to the third switch unit (70).

主权项

1. A backlight driving circuit, configured to drive a light-emitting diode (LED) module of an electronic device to emit light, comprising a LED driving chip, a power port configured to receive a power voltage, the LED driving chip comprising a control terminal, the LED driving chip output a pulse-width modulation (PWM) signal via the control terminal; the LED module comprising a first LED string and a second LED string, wherein the backlight driving circuit further comprises:
a voltage conversion unit comprising a primary winding and a secondary winding; a first switch unit electrically connected between the power port and the primary winding of the voltage conversion unit; a second switch unit forms a first circuit loop with the secondary winding of the voltage conversion unit, and the first LED string; a third switch unit forms a second circuit loop with the primary winding of the voltage conversion unit and the second LED string; and a level conversion unit connected between the control terminal of the LED driving chip and the third switch unit, and configured to receive the PWM signal output by the control terminal of the LED driving chip and reverse a voltage level of the PWM signal, and output the reversed PWM signal to the third switch unit to control the third unit to turn on or off periodically; wherein the first switch unit and the second switch unit are both connected to the control terminal of the LED driving chip, and configured to receive the PWM signal output by the control terminal and to turn on or off periodically accordingly; in one period of the PWM signal, when the first switch unit and the second switch unit are turned on, the third switch unit is turned off, when the first switch unit and the second switch unit are turned off, the third switch unit is turned on.