| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC-DC converter in which a switching element can be driven perfectly even when the input voltage drops to decrease the output current. SOLUTION: A bootstrap circuit 2 is connected between the drain and source of an N-MOSFET Q1, and an FET drive circuit 3 is connected between the gate of the N-MOSFET Q1 and the joint of a diode DB and a capacitor CB comprising the bootstrap circuit 2. A smoothing circuit 1 comprising a diode D1, a coil L1 and an output circuit Co and a voltage dividing resistor 4 for detecting the output voltage comprising resistors R1, R2 are connected to the output side of the N-MOSFET Q1. Furthermore, an error amplifier 5 and a pulse width modulation circuit 6 are connected between the FET drive circuit 3 and the joint of the resistors R1, R2 comprising the voltage dividing resistor 4. The pulse width modulation circuit 6 is also connected with a variable frequency circuit 11. |
