Power Semiconductor Driving Circuit dv/dt False Operation
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Solution Overview
Problem
Conventional driving circuits for power semiconductor elements, such as IGBTs and MOSFETs, face issues with false operation due to voltage changes (dv/dt) leading to arm short-circuits and potential breakage, especially when negative bias voltages are applied, requiring inverse voltage-resistance characteristics or diodes to manage these voltages effectively.
Innovation Solution
A driving circuit configuration that connects a switching element between the control terminal of the power semiconductor element and the negative side of the negative-voltage power supply, allowing the switching element to turn on without applying an inverse voltage between the main terminals, thereby preventing false operations caused by positive bias voltages during OFF states, without the need for inverse voltage-resistance characteristics or diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative bias voltage is applied between gate-emitter terminals to prevent false operation, then the power semiconductor element can be kept in OFF state, but voltage changes may occur before the negative bias voltage is established, causing gate voltage to increase and trigger false operation
Solution Approach 1:
The circuit applies a negative bias voltage to the gate-emitter terminals in advance, before the power semiconductor element is turned OFF. This preliminary application of negative bias ensures that when voltage changes occur during turn-off, the gate voltage does not rise above the threshold, preventing false operation. The negative bias is established beforehand to counteract any dv/dt-induced voltage spikes.
2Reliability
If a normally-on-type FET is connected between gate terminal and source terminal to short-circuit gate-source terminals, then false operation can be prevented, but an inverse voltage is applied between drain-source terminals requiring special characteristics or additional diodes
Solution Approach 1:
Instead of connecting the switching element between gate terminal and source terminal (conventional approach), the invention connects it between gate terminal and reference terminal. This inversion of connection points allows the switching element to clamp the gate voltage to the reference potential, preventing false operation without applying inverse voltage across the switching element's main terminals, thus eliminating the need for special characteristics or diodes.
3Reliability
If the switching element is connected between gate terminal and source terminal, then false operation can be prevented, but the switching element requires inverse voltage-resistance characteristics which complicates the circuit design
Solution Approach 1:
The invention inverts the conventional connection by placing the switching element between gate terminal and reference terminal instead of gate terminal and source terminal. This configuration change allows the switching element to function as a voltage clamp without exposing it to inverse voltage stress, simplifying the circuit design and eliminating the need for special component characteristics.
4Reliability
If voltage change dv/dt occurs between collector-emitter terminals in OFF state, then the gate voltage increases due to parasitic capacitance, but this can cause arm short-circuit and breakage of the power semiconductor element
Solution Approach 1:
The circuit applies a negative bias voltage to the gate-emitter terminals in advance to counteract the harmful effect of dv/dt. When voltage changes occur between collector-emitter terminals, the pre-applied negative bias ensures that the gate voltage does not rise above the threshold, preventing false turn-on and subsequent breakage. This preliminary counter-action neutralizes the harmful dv/dt effect before it can cause damage.
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 effectively prevents false ON operations and subsequent breakage of power semiconductor elements by managing voltage changes without requiring elements with inverse voltage-resistance characteristics, reducing the risk of short-circuits and maintaining the power semiconductor elements in the correct OFF state.
Implementation Method 1
when a voltage change dv/dt occurs between collector-emitter terminals of the power semiconductor element in OFF state, the gate voltage increases due to the parasitic capacitance associated with the gate of the power semiconductor element
Data Source
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AI summary
An object of the invention is to prevent the false operation of a power semiconductor element due to a voltage change, to thereby prevent breakage of the power semiconductor element. A driving circuit (34) of this invention is characterized by including: a voltage detector (circuit (37)) that detects the sum voltage of a positive bias voltage and a negative bias voltage, the negative bias voltage or the positive bias voltage; and a switching element (transistor (81)) that is connected to the control terminal of a power element (arm (32u)) and the negative side of a negative-voltage power supply (DC power supply (62)); wherein, when the value of the detection target voltage becomes lower than a voltage setting value or when a voltage between the control terminal and the reference terminal in the power element (arm (32u)) increases in a state where the value of the detection target voltage is lower than the voltage setting value, the voltage detector (circuit (37)) turns on the switching element (transistor (81)) to thereby supply, between the above terminals in the power element (arm (32u)), a voltage of 0 V or lower.