Power Converter Clamp Circuit for MOSFET Gate Protection
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Solution Overview
Problem
Power converters used in vehicles with in-vehicle batteries face damage due to excessive voltage fluctuations, which can cause failure in the MOSFET's gate drive circuit, especially when the DC power source voltage rises to high levels.
Innovation Solution
A power converter configuration that includes a clamp circuit to restrict excessive voltage application to the high-side drive circuit, utilizing a charge pump circuit and a bootstrap circuit to generate higher voltages while the clamp circuit limits voltages above a preset level, preventing damage to the semiconductor elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap circuit is used to generate high voltage for driving the MOSFET gate, then the MOSFET can be properly driven in high-side configuration, but excessive voltage spikes can damage the gate drive circuit
Solution Approach 1:
A clamp circuit is introduced as an intermediary component between the bootstrap circuit and the high-side drive circuit. This clamp circuit includes a clamp element (such as a Zener diode or TVS diode) that activates when voltage exceeds a predetermined threshold, providing a safe discharge path for excessive voltage and protecting the MOSFET gate drive circuit from voltage spikes and surges.
Solution Approach 2:
The clamp circuit is configured to activate before excessive voltage can reach damaging levels. By setting the clamp voltage threshold below the maximum tolerable voltage of the MOSFET gate, the system provides preventive protection that cushions against potential voltage damage before it occurs.
2Reliability
If the DC power source voltage fluctuates to high levels, then the bootstrap circuit generates excessively high output voltage, but this causes damage to the semiconductor element
Solution Approach 1:
The clamp circuit serves as a protective intermediary that monitors and limits the output voltage of the bootstrap circuit. When the power source voltage fluctuates to high levels, the clamp element activates to restrict the voltage to a safe level, preventing damage to the MOSFET and other semiconductor elements while allowing the bootstrap circuit to continue operating.
Solution Approach 2:
The clamp circuit provides automatic feedback control by monitoring the voltage level and activating the clamp element when voltage exceeds the predetermined threshold. This feedback mechanism ensures that the output voltage remains within safe limits even when the power source voltage fluctuates, protecting the semiconductor elements without requiring external intervention.
Data Source
AI summary
An inverter main circuit using high-side MOSFETS converts a power source voltage of a battery to an alternating current, and supplies the alternating current to a three-phase motor. A control circuit drives, via a high-side drive circuit and a low-side drive circuit, the MOSFETS. A charge pump circuit boosts the power source voltage to a charge pump voltage. A bootstrap circuit outputs a bootstrap voltage that is boosted by diodes and capacitors, which is then passed to a clamp circuit for clamping and outputting as a clamp voltage. Based on the supply of the charge pump voltage or the clamp voltage in response to a fluctuation of the power source voltage, a continuous circuit operation is provided while protecting the circuit in operation.