Patent ID: 7928601

Claim:
A power supply circuit for generating a plurality of voltages, including first and second voltages, with an input voltage, the power supply circuit comprising: a converter circuit for converting the input voltage into the first voltage; a switch circuit for outputting the input voltage as the second voltage; and a switch control circuit, connected to the converter circuit and the switch circuit, for comparing the first voltage with a reference voltage, generating a notification signal, based on the comparison result, for indicating the condition of the first voltage from a terminal coupled to the switch circuit, and controlling the switch circuit based on the notification signal, wherein the switch control circuit comprises: a first comparator, connected to the converter circuit, for comparing the first voltage with the reference voltage to generate a comparison signal; a transistor, connected to the first comparator, for generating a notification signal in response to the comparison signal; and a second comparator, connected to the transistor and the switch circuit, for comparing the notification signal with another reference voltage to generate a control signal for controlling the switch circuit.