Gate Driver Startup Clamping for Negative Rail Undershoot
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Solution Overview
Problem
Inverters in electric vehicles face issues with negative output voltage undershoot during startup, which can damage high-power switches due to the lack of immediate regulation by the shunt regulator, leading to uncontrolled energy dissipation and potential component damage.
Innovation Solution
A gate driver circuit with a short-circuit transistor and regulation control circuit that shorts the negative output rail to ground until the positive output voltage reaches a sufficient threshold, enabling the shunt regulator to activate and prevent undershoot, using a shunt transistor and error amplifier for precise voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shunt regulator is used to regulate the negative output voltage, then the negative output voltage can be maintained at a target value, but during startup the shunt regulator cannot immediately regulate the voltage, causing negative output voltage undershoot that can damage high-power switches
Solution Approach 1:
The patent applies preliminary action by enabling the shunt regulator before the high-power switch is turned on. The regulation control circuit activates the shunt regulator in advance during startup, allowing it to immediately clamp the negative output voltage and prevent undershoot when the switch operates, thereby protecting the switch from voltage spikes
Solution Approach 2:
The patent introduces a regulation control circuit as an intermediary between the flyback converter and the shunt regulator. This control circuit monitors the startup state and actively manages the shunt regulator's operation, coordinating between the converter output and the voltage clamping function to eliminate harmful undershoot
2Reliability
If the shunt regulator is activated during startup, then negative output voltage can be regulated, but the shunt regulator requires positive output voltage to power it, creating a startup sequence dependency
Solution Approach 1:
The patent implements feedback through the regulation control circuit that monitors the positive output voltage level and uses this information to control the shunt regulator activation. The circuit continuously senses the voltage state and adjusts the shunt regulator operation accordingly, creating a closed-loop control system that manages the startup sequence automatically
Solution Approach 2:
The regulation control circuit performs self-service by autonomously managing the startup sequence without external intervention. It automatically detects when the positive output voltage is sufficient, activates the shunt regulator at the appropriate moment, and coordinates the voltage regulation process, reducing the need for complex external control logic
Data Source
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AI summary
A driver circuit for controlling a high-power switch. The driver circuit comprises a flyback converter having a positive output rail and a negative output. The driver circuit also comprises: a driving stage that is connected between the positive output rail and the negative output rail; a shunt regulator configured to regulate the negative output voltage on the negative output rail based on a difference between the negative output voltage and a target negative voltage value, wherein the shunt regulator is powered by the positive output voltage on the positive output rail; a short-circuit transistor having a conduction channel that is connected between the negative output rail and a ground terminal; and a regulation control circuit configured to: provide a short-circuit control signal to a control terminal of the short-circuit transistor in order to short the negative output rail to the ground terminal until the positive output voltage reaches a positive threshold.