| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the necessity to develop a power supply IC for each CPU.SOLUTION: A power supply IC 10 generates an output voltage(V) according to a feedback voltage(V) by working together with a filter circuit 20. A CPU 30 is driven by the output voltage as its power supply voltage. A series circuit of voltage dividing resistors R3 and R4 is placed between an output line 51 to which the output voltage is applied and a ground, and a voltage at a connection point 52, at which the voltage dividing resistors R3 and R4 are connected, is provided to the power supply IC 10 as a feedback voltage. Before starting up the CPU 30, a switching element Q1, connected to the voltage dividing resistor R3 in parallel, is turned off, and an output voltage is generated so that a feedback voltage, depending on the resistor values of the voltage dividing resistors R3 and R4, matches with a predetermined initial target voltage. After starting up the CPU 30, the CPU 30 sets the power supply voltage to a desired value through adjusting of a target voltage of the feedback voltage and turning on of the switching element Q1. |
