| 摘要 |
PURPOSE:To enable easy manufacture of a stabilized power supply circuit in a stable and highly reliable manner by outputting a voltage for voltage margin test with action of a constant current circuit provided at a part of a resistance in a voltage detection circuit. CONSTITUTION:A constant current circuit 10 comprising a resistance R4, a transistor Q3, a constant voltage diode 7, and a photocoupler 8 is provided at a resistance R2 in a voltage detection circuit 6. With the action of the photocoupler 8 for actuating a gate circuit 9, a constant current I2 flows from the constant current circuit 10 which combines with the resistance R2 to produce a voltage V2. The output voltage V1 gives a low voltage at a constant level by the relationship shown by the following equation: V1=(R1+R2) (E-V2)/R2, where R1 and R2 represents a resistance and E a reference voltage. To meet the requirement of the equation, the resistances are respectively set to satisfy R1+R2>> R3. Thus, the voltage across the resistance R3 subject to R1+R2>> R3. This provides a regulated power supply circuit stable and highly reliable and easy to manufacture. |
