Patent ID: 10116160

Abstract:
A charging circuit for a bootstrap capacitor comprises a P MOSFET having a body diode and an N channel power MOSFET also having a body diode. The drain of the P MOSFET is coupled to the source of the N channel power MOSFET, and the source of the P MOSFET receives current from a vehicle's battery. The gate of the P MOSFET receives a control signal for turning the P MOSFET either on or off and the drain of the N channel power MOSFET is connected to a bootstrap capacitor The P MOSFET's body diode prevents current flow from the battery to the bootstrap capacitor when the P MOSFET is turned off and the N MOSFET's body diode prevents current flow from the bootstrap capacitor to the battery when the N MOSFET is turned off. The use of a power MOSFET device with its low ON resistance ensures that the capacitor is charged to a sufficiently high voltage even under low battery conditions.