| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a small-sized switching power unit which can respond at a high speed. SOLUTION: A switching power unit is provided with a pulse width modulator 35 which generates control signals for turning on/off a switching transistor 31, a central processing unit 41 which outputs a modulate signal to the modulator 35, sensors 42, 43, and 44 which respectively detect the input voltage Vin, output current Iout, ambient temperature Ta of the power unit, and a table 48 on which the relations between the detected values of the sensors 42, 43, and 44 and the turning-on time of the transistor 31 are stored. The central control unit 41 selects the turning-on time of the transistor 31 from the table 48 and controls the turning on/off of the transistor 31 based on the selected turning-on time. Therefore, the switching of the input voltage of the power unit can be controlled correspondingly to the fluctuation of the input voltage, output current, or ambient temperature without monitoring the output voltage of the power unit, and the output voltage can be maintained stably at a desired value.</p> |
