IGBT Control Circuit Voltage Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control circuits for IGBT transistors in series connections face challenges in voltage balancing, particularly when one IGBT fails, leading to potential voltage imbalances and increased switching losses due to external capacitance additions.
Innovation Solution
A control circuit for IGBT transistors featuring a capacitor connected to the collector and gate, with a diode in series and two Zener diodes between the emitter and a common point, along with a resistor to dampen oscillations, allows for reduced opening resistance to minimize switching time and maintain voltage balance without altering the collector-emitter voltage slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external capacitance is added between gate and collector for voltage balancing, then voltage balancing is improved, but switching time increases and switching losses increase
Solution Approach 1:
The patent introduces a diode as an intermediary element between the external capacitance and the gate. This diode selectively blocks the capacitance from affecting the turn-on process while allowing it to influence the turn-off process, thereby achieving voltage balancing without degrading turn-on switching performance and minimizing switching losses.
2Speed
If opening resistance is reduced to minimize switching time, then switching speed is improved, but voltage balancing becomes more difficult to maintain
Solution Approach 1:
The diode acts as a mediator that enables the use of low opening resistance for fast switching while maintaining voltage balancing. During turn-off, the diode conducts and allows the external capacitance to charge, providing the necessary dv/dt control for voltage balancing even with reduced opening resistance.
Solution Approach 2:
The patent changes the operational parameters by introducing asymmetric resistance values for turn-on and turn-off processes. The opening resistance is reduced for fast switching, while the closing resistance is increased to work in conjunction with the external capacitance for voltage balancing, thereby optimizing both speed and reliability.
3Reliability
If dv/dt controller is active during closure for voltage balancing, then voltage balancing is improved, but additional losses occur due to continuous operation
Solution Approach 1:
The diode enables periodic action by being active only during specific phases of the IGBT operation. The dv/dt controller (external capacitance) is activated during turn-off when the diode conducts, and remains inactive during turn-on when the diode blocks, thereby achieving voltage balancing only when needed and minimizing continuous energy losses.
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 ensures accurate voltage balancing across IGBTs in series, reducing switching losses and maintaining the desired collector-emitter voltage slope, even when one IGBT fails, while minimizing additional losses and voltage imbalances.
Implementation Method 1
A capacitor (8) having one terminal connected to the collector (7) and the other terminal connected to the gate (2) of the IGBT
Implementation Method 2
a diode (10) connected in series between the capacitor (8) and the gate (2) of the IGBT transistor
Implementation Method 3
two Zener diodes (12, 13) connected head to tail between the emitter (14) of the IGBT transistor and the point common to the capacitor and to the diode
Data Source
Figure 1~6
Figure 2~3
Figure 4~5
AI summary
The circuit has zener diodes (12, 13) connected between an emitter (14) of an insulated gate bipolar transistor (1) and a common point i.e. anode (9), of a capacitor (8) and to a diode (10). The diode is connected in series between the capacitor and a gate (2) of the insulated gate bipolar transistor, and is connected in a passing direction from a collector (7) of the transistor to the gate of the transistor. A resistor (6) is in series with the capacitor and the diode, and a capacitance value (C) of the capacitor is equal to 6.6 nanofarads.