| 摘要 |
PURPOSE:To detect the zero-point voltage of full-wave rectified voltage by connecting the first and second capacitors to the collector of the second transistor and connecting the base of the first transistor through the first capacitor. CONSTITUTION:When the output of a full-wave rectifying circuit DB is inputted to a zero-point detecting circuit 5 at the point of time t0, a base is driven and a transistor Q1 is at ON, a transistor Q2 is at OFF, and capacitors C1, C2 are charged. When input reaches near a zero point, the capacitor C2 instantaneously discharges electricity in the course of C2 R5 Q2 D3 C2 because the transistor Q1 is at OFF and the transistor Q2 is at ON, and potential at a point (n) suddenly drops. On the other hand, the capacitor C1 also starts discharge simultaneously in the course of C1 R6 Q2 D3 R3 C1. Accordingly, the output of the collector of the transistor Q1 is inverted into an ''H'' level from ''L'' at the point of time when the transistor Q1 is at OFF, and pulse signals inverted to the ''L'' level from the ''H'' at the point of time when the Q1 is at ON can be detected as the detecting signals of the zero point. |
