| 摘要 |
PURPOSE:To make the relation characteristic between energizing degree to a fan motor and the number of rotation linear, by setting the minimum unit of the energizing and unenergizing duration to the fan motor on a one AC cycle basis. CONSTITUTION:A zero-cross point detection circuit is composed of diodes 7 and 8, resistances 9, 10 and 12 as well as a transistor 11. A microcomputer 13 performs the timing of ON and OFF controlling the energizing duration output by the number of output pulses of a zero-cross voltage detection circuit on a cycle basis by the number of set-up zero-cross voltage detection pulses. On that account, the minimum unit of the energizing duration or unenergizing duration to a fan motor is set based on a cycle of an AC power source, so that the number of cycles energized on the positive side of the AC power source tallies with the number of cycles energized on the negative side and on deviation is found and that the DC braking is eliminated. |
