| 摘要 |
PURPOSE:To prevent the voltage converted through a step-down voltage converting circuit from lowering even when the load current drops below a rated range by feeding the output current from a step-up voltage converting circuit through a rectifying element to the step-down voltage converting circuit even when the load current exceeds the rated range. CONSTITUTION:Upon provision of an operational command to any one of drive motor, paper feed motor, or head section in a printer, a decision is made that the power supply voltage has dropped and a control circuit 16 operates a step-up switching regulator 11 to feed a step-down regulator 14 with an output voltage converted to 18V. The regulator 14 converts input voltage of 18V into 9V which is then fed to the step-down regulator 12. Consequently, even if a machine consuming high power operates to cause power supply voltage drop, a converted high voltage is fed from the regulator 11 to the regulator 12. At that time, counter flow to the power supply 20 is blocked by means of a diode 13. |
