Patent ID: 7368895

Claim:
An apparatus for a power supply with brownout protection, comprising: a PFC circuit, receiving an input voltage for performing a power factor correction and a voltage boosting operation to increase said input voltage to a bus voltage, wherein said bus voltage is greater than said input voltage; a bus capacitor, connected to an output terminal of said PFC circuit, wherein said bus capacitor is charged to a magnitude of said bus voltage; a PWM circuit having an input coupled to said bus capacitor and an output coupled to a microprocessor, said PWM circuit generating at least one output voltage at said output thereof in response to the bus voltage; a supervisor circuit having a first input coupled to said bus capacitor to detect a proportional bus voltage, a second input coupled to said output of said PWM circuit to monitor said at least one output voltage thereof, and an output connected to said microprocessor, said supervisor circuit outputting at least one power-good signal to said microprocessor said proportional bus voltage being less than a threshold voltage, said supervisor circuit outputting said at least one power-good signal preceding a reduction in said output voltage of said PWM circuit due to a reduction in said bus voltage during a brownout condition; and a brownout circuit, coupled between said input voltage and said PFC circuit, said brownout circuit disabling said voltage boosting operation of said PFC circuit responsive to detection of the brownout condition and thereby reduce said bus voltage, wherein once said at least one power-good signal is output to the microprocessor, the microprocessor process a shutdown procedure.