| 摘要 |
PURPOSE:To obtain the linearity of control even in a low speed rotating range by controlling ON or OFF in the low speed rotating range, and controlling the ON/OFF control period proportionally to the temperature of an object to be cooled. CONSTITUTION:When a fan motor 8 is disposed in a stable high speed rotating range control, a Zener diode 10 is OFF. Thus, a thyristor 7 is controlled in phase in response to a temperature detection signal A. Since the diode 10 is turned ON in the low speed range, a current is flowed to a resistor 9 to generate a potential difference across the resistor 9. Thus, an error voltage V1 is generated in a differential amplifier 5. A comparator 13 compares the voltage V1 with a triangular wave signal V2, and generates a pulse (e). A conduction angle signal C fed from the comparator 5 is supplied to a trigger pulse generator 5 during a period that an AND gate 14 is gated by the pulse (e), and the thyristor 7 is controlled ON or OFF at the prescribed period during the output of the signal (e). |
