IGBT Gate Circuit with Integrated Diode and Resistor for dv/dt Control
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Solution Overview
Problem
Insulated gate bipolar transistors (IGBTs) used in light-emitting devices face a trade-off between dv/dt breakdown and thermal breakdown due to the limitations of external gate resistors, where increasing resistance to prevent dv/dt breakdown can lead to excessive turn-off loss and thermal breakdown, and existing configurations cannot control turn-on and turn-off characteristics independently.
Innovation Solution
An insulated gate semiconductor device is designed with a rectifier diode and a resistor connected in parallel, integrated into the same chip as the IGBT, allowing independent control of dv/dt during turn-off and turn-on, and a gate-to-emitter protection diode is included to prevent excessive voltage from damaging the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance of the gate resistor is increased to reduce dv/dt and prevent dv/dt breakdown, then dv/dt breakdown is prevented, but turn-off loss increases leading to thermal breakdown
Solution Approach 1:
The gate control path is segmented into two separate resistors: a first gate resistor connected to the gate drive circuit for turn-on control, and a second gate resistor connected between the gate and emitter for turn-off control. This segmentation allows independent optimization of turn-on and turn-off characteristics, enabling the second resistor to limit dv/dt during turn-off without significantly affecting turn-on performance, thus reducing the trade-off between dv/dt breakdown prevention and turn-off loss.
Solution Approach 2:
Different resistance values are applied to different parts of the gate control circuit: the first gate resistor has a lower resistance value optimized for turn-on speed, while the second gate resistor has a higher resistance value specifically for dv/dt control during turn-off. This local quality differentiation allows each resistor to be optimized for its specific function, preventing the need to compromise overall performance.
2Reliability
If a single gate resistor is used to control dv/dt, then dv/dt can be limited, but turn-on and turn-off characteristics cannot be controlled independently
Solution Approach 1:
The gate control circuit is divided into two independent paths: one path through the first gate resistor for turn-on control from the gate drive circuit, and another path through the second gate resistor for turn-off control to the emitter. This segmentation enables independent adjustment of resistance values to optimize turn-on speed and turn-off dv/dt characteristics separately, providing versatile control capability.
Solution Approach 2:
The circuit dynamically switches between different resistor paths during turn-on and turn-off operations. During turn-on, the first gate resistor dominates the control characteristics, while during turn-off, the second gate resistor becomes the primary control element. This dynamic behavior allows the system to adapt different resistance characteristics to different operational phases.
3Reliability
If external gate resistors are used to control dv/dt, then dv/dt can be limited, but device complexity and space requirements increase
Solution Approach 1:
Both the first gate resistor and the second gate resistor are integrated onto the same semiconductor chip as the IGBT, forming a single integrated device. This merging eliminates the need for separate external resistor components and their associated mounting hardware, reducing device complexity and space requirements while maintaining the dv/dt control functionality.
Solution Approach 2:
The gate resistors are nested within the chip structure, with the second gate resistor connected between the gate electrode and emitter region inside the chip. This nesting approach embeds the dv/dt control functionality directly within the device architecture, eliminating external components and simplifying the overall system.
Data Source
AI summary
By integrating a diode and a resistor connected in parallel into the same chip as an IGBT and connecting a cathode of the diode to a gate of the IGBT, the value of dv/dt can be limited to a predetermined range inside the chip of the IGBT without a deterioration in turn-on characteristics. Since the chip includes a resistor having such a resistance that a dv/dt breakdown of the IGBT can be prevented, the IGBT can be prevented from being broken by an increase in dv/dt at a site (user site) to which the chip is supplied.