LCD DRIVING VOLTAGE GENERATING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To improve the productivity of products by generating an analog voltage and a stable digital voltage with a single board. SOLUTION: A DC/DC converter 10 receives a power supply voltage variable in voltage value Vcc and generates the analog voltage Va of 5V. Resistors R1, R2 divide the output voltage Va of the DC/DC converter 10 in a specified ratio. An n-p-n type transistors Q1 receives the voltage impressed at both ends of the resistor R2 at its base. The input terminal of the power supply voltage Vcc and the output terminal of the digital voltage Vo are respectively connected to a collector and an emitter and have the function that sets the digital voltage of 3.3V. An nMOS transistor M1 is inputted with the output voltage Va of the DC/DC converter 10 at its gate and the input terminal of the power supply voltage Vcc and the output terminal of the digital voltage Vo are respectively connected to its drain and source. This TR outputs the digital voltage Vo set regardless of the supplied power supply voltage Vcc.