| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To stably output an output voltage which is close to a target value in a such configuration that two power supply circuits are combined. <P>SOLUTION: While a switch 14 is turned off, a power supply circuit 15 of an IC 11 for a power source operates according to the supply of a battery voltage VBAT, and outputs the voltage of Vz-VF. While the switch 14 is turned on, the power supply circuits 15 and 16 operate, and an operating amplifier 20 controls the power supply circuit 15 and the power supply circuit 16. When an output voltage Vo is made lower than a target voltage (5 V), the collector currents (flushing currents) of a transistor Q11 are decreased, and currents flowing to a voltage generating circuit 5 are increased, and an output voltage is increased. At the same time, the collector/emitter voltage of the transistor Q3 is decreased, and an output voltage is increased. When Vz-VF>5 V, the IC11 for a power source outputs the power supply voltage of 5 V based on the reference voltage VBG. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
