| 摘要 |
PURPOSE:To obtain an inexpensive and small-sized power source circuit by detecting electrically a variation of a primary power source, bringing a resistor which has been connected in series to a rectifying circuit, to short circuit/non- short circuit to match said variation, and making a rectifying output voltage constant. CONSTITUTION:When a primary power source 1 is 110V or 120V, a transistor TR 13 is cut off, and when said power source is 220V or 240V, the TR 13 is turned on. When the TR 13 is turned on, a TR 14 is turned off, and when the TR 13 is turned off, the TR 14 is turned on. Accordingly, in accordance with turn-on and turn-off of the TR 14, a resistor 9 is short-circuited or not short-circuited. In this way, in order that the resistor 9 is short-circuited, when the power source 1 is 110V or 120V, and it is not short-circuited, when the power source 1 is 220V or 240V, a rectifying voltage is lowered by a voltage drop. Therefore, by selecting the resistor 9 to a suitable value, a voltage of an output terminal 15, which has been rectified becomes the same, even if the power source 1 is varied greatly.
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