Gate Drive Circuit Bootstrap Voltage Maintenance
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Solution Overview
Problem
The existing gate drive circuits with voltage-drop prevention resistors between the emitter and base terminals of bipolar transistors in the booster circuit fail to sufficiently prevent voltage lowering, leading to potential malfunctions in semiconductor switches.
Innovation Solution
A gate drive circuit design that includes a signal generation unit, a signal isolation unit, and an output stage device with complementary semiconductor switches, utilizing a resistor in the path to ensure the gate drive signal maintains the output voltage of the power supply, reducing the risk of malfunction by maintaining the voltage between the gate and source terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage-drop prevention resistor is connected in series with a resistor of the booster circuit, then the voltage applied between the emitter terminal and base terminal of bipolar transistors is reduced through potential division, but the voltage lowering between emitter and base terminals is not sufficiently prevented, resulting in voltage lower than the driver output voltage
Solution Approach 1:
The patent introduces a bootstrap capacitor as an intermediary energy storage element between the driver and the booster circuit. This capacitor stores energy during the off-state and releases it during the on-state, mediating the voltage transmission to prevent excessive voltage division and ensure sufficient voltage reaches the bipolar transistor base-emitter junction, thereby resolving the contradiction between preventing voltage lowering and minimizing energy loss.
2Device complexity
If the voltage between the emitter terminal and base terminal of bipolar transistors is lowered, then the circuit configuration is simplified, but the semiconductor switch may malfunction due to insufficient voltage
Solution Approach 1:
The patent employs a dynamic bootstrap circuit configuration where the bootstrap capacitor is charged and discharged in synchronization with the switching states of the semiconductor devices. During the off-state, the capacitor charges to a predetermined voltage; during the on-state, it dynamically releases this stored energy to maintain adequate base-emitter voltage. This dynamic operation ensures reliable semiconductor switch operation while maintaining a relatively simple circuit configuration without requiring complex voltage regulation mechanisms.
Data Source
AI summary
A gate drive circuit includes a signal generation unit configured to generate a first gate drive signal, a signal isolation unit configured to produce, at an output side thereof in response to the first gate drive signal, a second gate drive signal electrically isolated from the signal generation unit, an output stage device configured to receive the second gate drive signal at an input side thereof and to produce a third gate drive signal at an output side thereof in response to the second gate drive signal, a first path connecting the output side of the signal isolation unit and the input side of the output stage device; and a second path connecting the output side of the signal isolation unit and the output side of the output stage device.