| 摘要 |
PURPOSE:To enhance the power effects, prevent the mutually interfering action from occurring between both power sources, and improve reliability by detecting the polarities of diodes in a diode OR circuit. CONSTITUTION:When the polarity of a voltage at point A is positive with respect to a voltage at C point, a transistor Q1 becomes conductive by a differential amplifier 8 while the transitors Q2 and Q3 becomes non-conductive. If the output voltage of a first power source is increased to make a zener diode ZD reach the breakdown voltage, a photocoupler PC is illuminated. In other words, a high-voltage disconnecting circuit 12 is activated to prevent the voltage to a charge 3 from being increased abnormally. On the contrary, if the polarity of the voltage at A point is negative with respect to the voltage at C point, the transistor Q3 becomes conductive. Therefore, the photocoupler PC is not illuminated. Thus, it is possible to prevent the mutually interfering action from occurring due to the abnormally high voltage between the power sources without activating the high-voltage disconnecting circuit. In other words, lower-order voltage drop diodes can be adopted as the diodes for the diode OR circuit, thus enhancing the power effects. |
