Backlight drive circuit, electronic device and backlight drive method

Abstract

A backlight drive circuit (1) comprises an LED constant current driver chip (10) outputting PWM signals, a power interface (20), a voltage transformation unit (30), a first switch unit (50), a second switch unit (60), a third switch unit (70) and a level converting unit (40). The voltage transformation unit (30) comprises a primary coil (31) and a secondary coil (32). The first switch unit (50) is connected with the power interface (20) and the primary coil (31), the second switch unit (60), the secondary coil (32) and a first LED string (21) form a first current loop (LP1), the first switch unit (50) and the second switch unit (60) receive the PWM signals to be powered on and powered off, the third switch unit (70), the primary coil (31) and a second LED string (22) form a second current loop (LP2), and level converting is carried out on the PWM signals through the level converting unit and then the PWM signals are outputted to the third switch unit (70). The invention further provides an electronic device and a backlight drive method. The backlight drive circuit can drive multiple LED lamps without increasing output voltage.

Description

technical field [0001] The invention relates to a driving circuit, in particular to a backlight driving circuit, an electronic device with the backlight driving circuit, and a backlight driving method. Background technique [0002] At present, LEDs (light-emitting diodes, light-emitting diodes) have become more and more common as backlight sources for electronic devices such as mobile phones, televisions, and computer lamps. Generally, as the external environment changes, the luminance of the LED needs to be adjusted manually or automatically. As we all know, the LED is driven by a backlight driving circuit, and the backlight driving circuit changes the voltage output to the LED to change the brightness of the LED. like figure 1 As shown, the current backlight driving circuit 1' includes an LED constant current driving chip 10', a power interface 20', an inductor L and a MOS transistor Q. Wherein, the power interface 20' is used to access the power supply voltage Vin. The...

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Problems solved by technology

[0003] However, in the prior art, the output voltage Vout is only determined by the duty cycle D of the PWM signal. When the number of LED lamps connected in series in the LED module 2' is larger, the required output voltage Vout is also larger to drive the LED module 2'. Some LED lights, so the value of the duty cycle D also needs to be larger

When the value of the duty ratio D is large, the conduction time of the MOS transistor Q in one cycle is very long, because the current on the inductor L rises linearly, so the current flowing through the MOS transistor Q and the inductor L will be very large, and the entire The power loss of the circuit is large, and the operating temperature of the components is high and easily damaged

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