Dual IGBT Power Device Reducing Conduction and Switching Losses
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Solution Overview
Problem
Existing semiconductor devices face challenges in minimizing conduction and switching losses, particularly in high-power applications, due to limitations in controlling carrier concentration across the entire n-type drift layer, especially in high breakdown voltage structures.
Innovation Solution
The semiconductor device comprises two IGBTs with different ON voltage characteristics, where one has a low ON voltage and the other has a high ON voltage, connected in parallel, allowing for independent control of gate electrodes to optimize carrier concentration and reduce losses during conduction and turn-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single IGBT structure is used, then the device complexity is low, but it cannot simultaneously achieve low conduction loss and low turn-off loss
Solution Approach 1:
The patent divides a single IGBT into two separate IGBTs (first IGBT and second IGBT) with different structural characteristics. The first IGBT is optimized for low conduction loss with a first drift layer having specific properties, while the second IGBT is optimized for low turn-off loss with a second drift layer having different properties. This segmentation allows each IGBT to specialize in one loss reduction aspect, and when connected in parallel, they work together to achieve both low conduction and turn-off losses simultaneously.
Solution Approach 2:
The patent applies local quality by creating two IGBTs with locally different drift layer properties. The first drift layer has properties (such as doping concentration, thickness, or carrier lifetime) optimized for minimizing conduction loss, while the second drift layer has different properties optimized for minimizing turn-off loss. This local differentiation in drift layer quality enables each IGBT to excel at a specific function, resolving the contradiction between the two loss types.
2Reliability
If high breakdown voltage is achieved, then device reliability is improved, but control over carrier concentration in the drift layer is limited
Solution Approach 1:
The patent segments the carrier concentration control function by creating two separate IGBTs with different drift layer properties. Each IGBT can be independently controlled through its gate electrode, allowing for flexible carrier concentration management. The first IGBT handles the aspect of maintaining high breakdown voltage, while the second IGBT provides the flexibility for carrier concentration control, resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The patent applies parameter changes to the drift layer properties in the two IGBTs to simultaneously achieve high breakdown voltage and good carrier concentration control. By appropriately selecting and varying parameters such as doping concentration, thickness, and carrier lifetime in different drift layers, the patent optimizes both breakdown voltage performance and carrier concentration controllability through independent gate control of each IGBT.
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 reduces both conduction and switching losses, improving the trade-off relationship between them and enhancing the overall efficiency of power conversion devices.
Implementation Method 1
When a voltage equal to or higher than a threshold voltage is applied to the Gs gates and the Gc gates, an electron inversion layer is formed in the vicinity of a gate electrode interface of a p type well layer
Implementation Method 2
As a result, hole carriers flow from a p type collector layer into the n− type drift layer. Accordingly, a conductivity modulation occurs inside the n− type drift layer
Implementation Method 3
The IGBTs and the diodes generate a conduction loss during conduction and generate a switching loss at the time of switching
Data Source
AI summary
A current switching semiconductor device to be used in a power conversion device achieves both a low conduction loss and a low switching loss. The semiconductor device includes the IGBT in which only Gc gates are provided and an impurity concentration of the p type collector layer is high, and the IGBT in which the Gs gates and the Gc gates are provided and an impurity concentration of the p type collector layer is low. When the semiconductor device is turned off, the semiconductor device transitions from a state in which a voltage lower than a threshold voltage is applied to both the Gs gates and the Gc gates to a state in which a voltage equal to or higher than the threshold voltage is applied to the Gc gates prior to the Gs gates.