Active Clamping Circuit for Semiconductor Switch Surge Protection
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Solution Overview
Problem
Existing semiconductor switches face deterioration due to excessive surge voltage when turning off, especially when the energy in the inductance component of the load circuit exceeds the switch's capacity, leading to degraded performance.
Innovation Solution
A switch system incorporating a semiconductor switch, a voltage clamping element, and an active clamping circuit with controlled diodes and transistors to manage the surge voltage, including a first diode with a lower breakdown voltage than the clamping element, allowing controlled energy dissipation and reduced voltage application during switch-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage clamping element is used to limit surge voltage, then the semiconductor switch is protected from overvoltage, but the clamp voltage remains too high when inductance energy exceeds switch capacity
Solution Approach 1:
The voltage clamping function is segmented into two stages: first, the active clamping circuit with breakdown diode provides initial clamping at a lower voltage level; second, the voltage clamping element provides backup clamping at a higher voltage level. This segmentation allows the system to handle both small and large inductance energy scenarios effectively.
Solution Approach 2:
The active clamping circuit with the breakdown diode and control switch operates preliminarily to clamp voltage before the main voltage clamping element is activated. By engaging the active clamping circuit first, the system reduces the surge voltage to a lower level, preventing excessive voltage from reaching the semiconductor switch.
2Loss of energy
If the breakdown voltage of the first diode is made smaller than the clamp voltage, then controlled energy dissipation is achieved, but the circuit complexity increases
Solution Approach 1:
The breakdown diode acts as an intermediary element that activates at a specific voltage threshold (breakdown voltage) to provide controlled energy dissipation. By positioning the breakdown diode in parallel with the semiconductor switch and controlling it through the control switch, the system achieves precise energy management without requiring complex additional circuitry.
Solution Approach 2:
The circuit utilizes parameter changes in the breakdown diode's voltage-current characteristics to achieve controlled energy dissipation. By selecting a breakdown voltage lower than the main clamping voltage, the diode naturally limits the voltage across the semiconductor switch, and the control switch modulates the current flow to optimize energy dissipation based on operating conditions.
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
The system effectively reduces surge voltage applied to the semiconductor switch, minimizing deterioration and extending its lifespan, while also reducing the clamp voltage and preserving the load circuit's characteristics.
Implementation Method 1
The first diode causes breakdown upon application of voltage between the first main terminal and the second main terminal of the semiconductor switch
Data Source
AI summary
In a switch system, a voltage clamping element is connected to a semiconductor switch in parallel. An active clamping circuit is connected between a control terminal and a first main terminal of the semiconductor switch. The active clamping circuit includes a first diode, a second diode, and a control switch. A second anode of the second diode is connected to a first anode of the first diode. The control switch is connected between the first anode of the first diode and the control terminal of the semiconductor switch. A second control unit controls the control switch. A breakdown voltage of the first diode is smaller than a clamp voltage of the voltage clamping element.