| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device which can be easily downsized because the number of program writing external connection terminals is small and a program writing system therefor.SOLUTION: The switching power supply device comprises: a digital processor 10 which includes an EPROM having a control program stored therein and terminals D11 and D12 to which a digital signal for writing the control program into the EPROM is input; a power supply line 26 for a control circuit including the digital processor 10; and a power supply voltage monitoring circuit 42 which monitors a voltage change in the power supply line 26. When the control program is written into, a power supply voltage necessary to drive the digital processor 10 is supplied to the power supply line 26, and a specific digital signal is superposed on the power supply voltage as it is transmitted. The power supply voltage monitoring circuit 42 extracts the specific digital signal from the power supply voltage and outputs the extracted signal to the terminal D11. Other digital signals are input directly to the terminal D12. |
