High Voltage Bootstrap Circuit

Bootstrap circuit cb sourcing the figure below shows a typical waveform for the voltage across cb.

High voltage bootstrap circuit.

2 basic operation of bootstrap circuit a bootstrap circuit is used in half bridge configurations to supply bias to the high side fet. The bootstrap circuit uses a coupling capacitor formed from the gate source capacitance of a transistor to drive a signal line to slightly greater than the supply voltage. After connecting the circuit as per the circuit diagram the circuit looks similar to the darlington pair. When the base of the transistor q1 is high and point b is low.

Design and application guide of bootstrap circuit for high voltage gate drive ic by kevin angelo ma thursday september 29 2016 the purpose of this paper is to demonstrate a systematic approach to design high performance bootstrap gate drive circuits for high frequency high power and high efficiency switching applications using a power. To generate that high voltage a bootstrap circuit is used. The voltage increases through the charging period when q2 is on. Therefore the capacitor charges upto the value of voltage across r2.

The bootstrap circuit is useful in a high voltage gate driver and operates as follows. Bootstrap circuit cb sourcing figure 1 2. Simple in structure a bootstrap circuit is a step up charge pump composed of a switch a capacitor and a diode where a voltage equal to the switch voltage vin plus the internal supply voltage is used as the gate drive for the high side nch mosfet. Here we have used bootstrapping technique to increase the input impedance of this amplifier circuit.

Figure 1 shows the charging path of a bootstrap circuit in a simplified half bridge configuration using ucc27710 ti s 620v half bridge driver with interlock. When out is pulled down to ground the low side switch is turned on and the high side switch is turned off the bootstrap capacitor charges through the bootstrap diode from the gvdd power supply as shown in figure 1. When the vs goes below the ic supply voltage vdd or is pulled down to ground the low side switch is turned on and the high side switch is turned off the bootstrap capacitor cboot charges through the. When the vs goes below the ic supply voltage vdd or is pulled down to ground the low side switch is turned on and the high side switch is turned off the bootstrap capacitor cboot charges through.

The bootstrap circuit is useful in a high voltage gate driver and operates as follows.