Power supply, power management device applied to a power supply, and method for performing brown-out protection and overheat protection of a power management device

摘要

A power supply can provide brown-out protection and overheat protection. The power supply includes a rectifier, a transformer, and a power management device. The rectifier is used for receiving an alternating current voltage. The alternating current voltage has a voltage cycle. The transformer coupled to the rectifier has an inductor coupled to a switch for supplying an output voltage. The power management device is used for controlling the switch to make the inductor save power or release power. The power management device has a multi-functional pin coupled to the rectifier for receiving a detection voltage corresponding to a positive half cycle of the alternating current voltage. The multi-functional pin is also coupled to a thermistor for receiving an overheat protection signal.

主权项

1. A power supply, comprising:
a rectifier for receiving an alternating current voltage, wherein the alternating current voltage has a voltage cycle; a transformer coupled to the rectifier, the transformer having an inductor coupled to a switch for supplying an output voltage; and a power management device for controlling the switch to make the inductor save power or release power, wherein the power management device has a multi-functional pin coupled to the rectifier for receiving a detection voltage corresponding to a positive half cycle of the alternating current voltage, and the multi-functional pin is further coupled to a thermistor for receiving an overheat protection signal, wherein the power management device comprises:
a low voltage detection circuit coupled to the multi-functional pin for comparing the detection voltage with a first reference voltage to output a first comparison signal when the voltage cycle of the alternating current voltage is the positive half cycle, wherein the power management device executes a brown-out protection according to the first comparison signal;an overheat detection circuit coupled to the multi-functional pin for comparing the overheat protection signal with a second reference voltage to output a second comparison signal when the voltage cycle of the alternating current voltage is a negative half cycle, wherein the power management device executes an overheat protection according to the second comparison signal and the second reference voltage is not fixed; anda switching circuit coupled to the multi-functional pin for detecting a current signal flowing in the multi-functional pin to determine the voltage cycle of the alternating current voltage, wherein the switching circuit switches the low voltage detection circuit to couple to the multi-functional pin for receiving a peak value of the alternating current voltage when the current signal is larger than zero, and switches the overheat detection circuit to couple to the multi-functional pin for receiving the overheat protection signal when the current signal is roughly equal to zero or smaller than zero.