Brightness control circuit and backlight control module

A brightness control circuit for a electronic device with a light emitting module, comprising

• a light sensor module generating a first current through the light sensor module according to a light intensity;
• a charging module coupled between the light sensor module and a ground and generating a charging voltage at a voltage node according to the first current;
• a voltage control circuit comprising:
• a reference voltage source providing a reference voltage;
• an operational amplifier having a non-inverse input terminal coupled to the reference voltage source, an inverse input terminal coupled to the voltage node and a first output terminal and outputting a comparative signal according to the reference voltage and the charging voltage;
• and
• a diode coupled between the inverse input terminal and the first output terminal;
• and
• a bipolar transistor coupled to the voltage control circuit and providing a second current according to the comparative signal.

A backlight control module, comprising:

• a light emitting module;
• and
• a brightness control circuit, comprising:
• a light sensor module generating a first current through the light sensor module according to a light intensity;
• a charging module coupled between the light sensor module and a ground and generating a charging voltage at a voltage node according to the first current;
• a voltage control circuit, comprising:
• a reference voltage source providing a reference voltage;
• a comparator having a non-inverse input terminal coupled to the reference voltage source, an inverse input terminal coupled to the voltage node and a first output terminal and outputting a comparative signal according to the reference voltage and the charging voltage;
• and
• a diode coupled between the inverse input terminal and the first output terminal;
• and
• a switch coupled to the voltage control circuit and providing a second current through a light emitting module according to the comparative signal.