Active Clamp Circuit for IGBT Overvoltage Protection
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Solution Overview
Problem
Existing active clamp circuits for IGBTs suffer from malfunctions due to reverse recovery of voltage regulator diodes, leading to increased loss and uneven voltages in series-connected IGBTs, which affects their performance and reliability in high-voltage applications.
Innovation Solution
An active clamp circuit design that includes a discharging circuit, a unidirectional blocking circuit, and an RC circuit, where the RC circuit is connected to the gate of the power semiconductor switch, allowing for rapid discharge of energy and preventing reverse recovery issues, thereby avoiding active clamp malfunctions and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage regulator diode is connected inversely between the collector and gate of the IGBT to prevent overvoltage, then the IGBT is protected from overvoltage, but the reverse recovery of the voltage regulator diode causes active clamp malfunctions and increased loss
Solution Approach 1:
The patent introduces an RC circuit as an intermediary between the voltage regulator diode and the IGBT gate. This RC circuit acts as a buffer that prevents the direct coupling of reverse recovery current to the gate, thereby eliminating the malfunction caused by the voltage regulator diode's reverse recovery while maintaining overvoltage protection functionality.
Solution Approach 2:
The patent segments the protection circuit into distinct functional blocks: the voltage regulator diode for overvoltage clamping, the RC circuit for filtering and timing, and the gate driver for controlled switching. This segmentation allows each component to perform its specific function without interfering with others, particularly preventing the reverse recovery effect from affecting the gate.
2Power
If series connection technology is used for IGBTs to increase voltage level, then high voltage applications are enabled, but uneven voltages and high voltage spikes occur across the series-connected IGBTs
Solution Approach 1:
The active clamp circuit provides feedback control by continuously monitoring the collector voltage of each IGBT and dynamically adjusting the gate voltage through the RC circuit. When overvoltage is detected, the voltage regulator diode conducts and the RC circuit responds by adjusting the gate voltage to redistribute the voltage evenly across series-connected IGBTs, preventing voltage spikes and ensuring stable voltage distribution.
3Reliability
If the energy of overvoltage is released by the IGBT itself through the voltage regulator diode, then overvoltage is prevented, but the loss of the IGBT increases
Solution Approach 1:
The RC circuit serves as an intermediary energy dissipation path. Instead of the IGBT directly dissipating the overvoltage energy through the voltage regulator diode, the RC circuit provides a controlled discharge path that limits the current and reduces the energy burden on the IGBT, thereby maintaining overvoltage protection while minimizing IGBT loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the stability and reliability of IGBTs by preventing active clamp malfunctions, reducing losses, and extending the modulation range, allowing for smoother motor starting and improved bus utilization in series-connected IGBT applications.
Implementation Method 1
When a voltage of the collector exceeds a preset voltage value, the voltage regulator diode breaks down inversely
Implementation Method 2
a resistance-capacitance RC circuit includes a first terminal and a second terminal, the first terminal of the RC circuit, the second terminal of the discharging circuit, and the second terminal of the series branch being electrically connected
Data Source
AI summary
The present disclosure discloses an active clamp circuit for a power semiconductor switch and a power converter using the same. The active clamp circuit includes: a discharging circuit, a first terminal of the discharging circuit being electrically connected to a collector of the power semiconductor switch; an unidirectional blocking circuit; a first voltage regulator diode connected in series with the unidirectional blocking circuit to form a series branch, a first terminal of the series branch being electrically connected to the collector of the power semiconductor switch; and a resistance-capacitance RC circuit, a first terminal of the RC circuit, a second terminal of the discharging circuit, and a second terminal of the serial circuit being electrically connected, a second terminal of the RC circuit being electrically coupled to a gate of the power semiconductor switch.