Patent ID: 9672779
Date: 2017-06-06
CPC Classifications: G09G,H05B,Y02B

Claim:
1. A backlight drive circuit, comprising: a booster circuit, which boosts an input voltage to a working voltage as required, a light-emitting unit, which is electrically connected to the booster circuit and works based on the working voltage therefrom, a current sensing resistor, in series connection to the light-emitting unit, a circuit for automatic adjustment of current, which is electrically connected to the current sensing resistor, and compares a detected voltage of the current sensing resistor with a predetermined reference voltage, so as to adjust the value of a resistor in series connection to the light-emitting unit, and thus to regulate current flowing through the light-emitting unit, and a controller, which is electrically connected to the light-emitting unit, and detects a relationship between an actual voltage corresponding to a current fed back by the light-emitting unit and a predetermined, internal voltage thereof, so as to generate a pulse width modulation signal for controlling the current flowing through the light-emitting unit; wherein the circuit for automatic adjustment of current further comprises: a first comparator, which compares the detected voltage of the current sensing resistor with a predetermined, first reference voltage, and outputs a switch signal according to a comparison result, a second comparator, which compares the detected voltage of the current sensing resistor with a predetermined, second reference voltage, and outputs a switch signal according to a comparison result, a first switch, which has a control terminal electrically connected to the first comparator, and performs an operation of turn-on or turn-off in accordance with a switch signal from the first comparator, a first resistor, which is in parallel connection to the first switch, and in series connection to the current sensing resistor along with the first switch, a second switch, which has a control terminal electrically connected to the second comparator, and performs an operation of turn-on or turn-off in accordance with a switch signal from the second comparator, and a second resistor, which is in series connection to the second switch, and in parallel connection to the current sensing resistor along with the second switch, wherein when the detected voltage of the current sensing resistor is higher than the first reference voltage, the first comparator outputs a turn-off signal, while when the detected voltage of the current sensing resistor is lower than the second reference voltage, the second comparator outputs a turn-on signal.