| 摘要 |
PROBLEM TO BE SOLVED: To cause a printer to appropriately operate by power feeding from a USB bus power.SOLUTION: A power supply circuit for a printer comprises a USB port 59a for performing communication and power feeding and a USB port 59b for performing the power feeding, and connects current control circuits 54a and 54b to a power supply line, power supply line for first bus power 52a, from the USB port 59a and to a power supply line, power supply line for second bus power 52b, from the USB port 59b, respectively. The current control circuits 54a and 54b are constituted of: N-channel type MOSFETs 55 connected to the power supply lines for USB bus power 52a and 52b; current detection circuits 56 for outputting output voltages Vout in response to currents flowing through the power supply lines for USB bus power 52a and 52b; and driving circuits 57 for applying gate voltages to the MOSFETs 55 in response to the output voltages Vout. |
