SiC Switching Element RC Snubber for Voltage Oscillation Control
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Solution Overview
Problem
Power conversion devices face challenges in suppressing current and voltage oscillations during switching operations, leading to increased losses and circuit size due to steep dv/dt and di/dt characteristics, especially in semiconductor devices using silicon carbide (SiC), where existing CR snubber circuits are inefficient in reducing surge voltages and heat dissipation.
Innovation Solution
A semiconductor device with a serial connection body of a capacitor and resistor between the high voltage and control terminals of the switching element, where the capacitor's capacitance is set to be ten times or less than the parasitic feedback capacitance, and the resistor is connected between the control terminal and an external connection control terminal, effectively adjusting the time constant to suppress resonance characteristics and oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a CR snubber circuit is used to suppress voltage oscillation, then voltage oscillation is reduced, but loss increases in proportion to capacitance and frequency
Solution Approach 1:
The patent introduces an RC circuit as an intermediary element connected between the drain and gate terminals. This RC circuit acts as a mediator that suppresses voltage oscillation by controlling the charging and discharging of the parasitic capacitance between drain and gate, thereby reducing the harmful voltage oscillation without requiring a large-capacitance CR snubber circuit that would increase loss.
Solution Approach 2:
The patent changes the parameter configuration by using a small capacitance value (0.1 pF to 10 pF) in the RC circuit, which is significantly smaller than conventional CR snubber circuits. This parameter change allows effective voltage oscillation suppression while minimizing the loss proportional to capacitance and frequency.
2Object-affected harmful factors
If capacitor size is increased to suppress voltage oscillation, then voltage oscillation suppression improves, but circuit size increases
Solution Approach 1:
The patent applies parameter changes by using a very small capacitance value (0.1 pF to 10 pF) in the RC circuit, which is orders of magnitude smaller than conventional CR snubber circuits. This enables effective voltage oscillation suppression while keeping the circuit size minimal, as the small capacitance requires minimal physical space.
3Speed
If dv/dt and di/dt are made steep for high-speed switching, then switching speed improves, but current and voltage oscillation increases
Solution Approach 1:
The RC circuit serves as an intermediary that mediates between the steep dv/dt and di/dt required for high-speed switching and the resulting voltage oscillation. By controlling the charging and discharging of the parasitic capacitance, the RC circuit allows high-speed switching to proceed while suppressing the harmful voltage oscillation that would otherwise result.
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 configuration significantly reduces current and voltage oscillations, thereby minimizing circuit size and heat dissipation, while effectively controlling the rising and falling speeds of voltage and current during switching operations, enhancing the efficiency of power conversion.
Implementation Method 1
the capacitor's capacitance is set to be ten times or less than the parasitic feedback capacitance, and the resistor is connected between the control terminal and an external connection control terminal, effectively adjusting the time constant to suppress resonance characteristics and oscillations
Implementation Method 2
effectively adjusting the time constant to suppress resonance characteristics and oscillations
Implementation Method 3
a serial connection body of a capacitor and a resistor is connected between the high voltage side terminal and the control terminal
Implementation Method 4
a serial connection body of a capacitor and a resistor is connected between the high voltage side terminal and the control terminal
Data Source
AI summary
A semiconductor device includes a unipolar switching element having a drain terminal, a gate terminal, and a source terminal, wherein a serial connection body of a capacitor and a resistor is connected between the drain terminal and the gate terminal.