LED backlight sources for liquid crystal devices and liquid crystal devices

摘要

The LED backlight source includes a boost circuit, a current control module, a voltage detection circuit. The boost circuit is configured for boosting an input voltage to an operation voltage needed by a LED string. The current control module connects to a negative end of the LED string to adjust an operation current of the LED string. The voltage detection circuit is configured for detecting whether the input voltage has been decreased, and for providing a control signals to a backlight driving control circuit upon determining the input voltage has been decreased. The backlight driving control circuit is configured for providing first square-wave signals to the boost circuit for boosting the voltage, for providing second square-wave signals to the current control module for adjusting a current, and for decreasing an input current upon receiving the control signals from the voltage detection circuit.

主权项

1. A LED backlight source for LCD, comprising:
a boost circuit for boosting an input voltage to an operation voltage needed by a LED string; a current control module connecting to an negative end of the LED string to adjust an operation current of the LED string; a voltage detection circuit for detecting whether the input voltage has been decreased, and for providing a control signals to a backlight driving control circuit upon determining the input voltage has been decreased; the backlight driving control circuit is configured for providing a first square-wave signals to the boost circuit for boosting the voltage, for providing a second square-wave signals to the current control module for adjusting a current, and for decreasing an input current upon receiving the control signals from the voltage detection circuit; and wherein the voltage detection circuit comprises: a divider configured for dividing the input voltage to generate a comparing voltage; a comparator configured for comparing the comparing voltage and the reference voltage; and a frequency adjusting circuit configured for controlling the backlight driving control circuit to increase the frequency of the first square-wave signals to be provided to the boost circuit upon determining the comparing voltage is smaller than the reference voltage so as to decreased the input current; and wherein the frequency adjusting circuit comprises a second MOS transistor, a third resistor, and a fourth resistor, a gate of the second MOS transistor connects to an output end of the comparator, a drain of the second MOS transistor connects to one end of the third resistor and to the backlight driving control circuit, the source of the second MOS transistor connects to one end of the fourth resistor, and the other end of the third resistor and the other end of the fourth resistor are electrically grounded.