USB EQUIPMENT POWER SUPPLY CIRCUIT

PROBLEM TO BE SOLVED: To provide a USB equipment power supply circuit capable of supplying excess power to USB-connected equipment that is supplied with power from a USB. SOLUTION: The USB equipment power supply circuit for USB equipment connected to USB VBUS is provided with multiple electric double layer capacitors C1, C2 that are charged from VBUS and discharged to USB equipment. Switches S1 to S5 are so switched that, during charging, the multiple electric double layer capacitors are connected in parallel with VBUS; and during discharging, the multiple electric double layer capacitors are connected in series with the VBUS to generate excess voltage. A comparator P1 compares the voltage of a predetermined electric double layer capacitor with a reference voltage to actuate the switches S1 to S5. Thus, when the output of USB equipment is low, power is supplied from the VBUS to the USB equipment. When the output of the USB equipment approximates to the VBUS output, excess voltage is supplied. COPYRIGHT: (C)2007,JPO&INPIT