The utility model relates to a
liquid crystal display television power supply technology, discloses an
overvoltage and
overcurrent protection circuit applied to a
liquid crystal display television power supply
system, effectively solves the
overvoltage and
overcurrent problems of the television power supply
system, and is simple in structure and easy to implement. In the scheme of the utility model, the
overvoltage and
overcurrent protection circuit is designed behind the switch
transformer in the power supply
system, and the output of the protection circuit is fed back to the
power management chip; the designed protection circuit detects
voltage and current output by a power supply system in real time through
voltage comparison at the two ends of a sampling
resistor and monitoring of a
voltage stabilizing
diode, and when overcurrent occurs, a
comparator outputs a high level to trigger a
field effect transistor and an optocoupler to be conducted, so that a protection pin of a
power management chip is pulled down, and a power supply is
cut off; and when overvoltage occurs, the voltage stabilizing
diode is conducted, so that the
field effect transistor and the optocoupler are triggered to be conducted, and therefore, the protection pin of the
power management chip is pulled down, and the power supply is
cut off.