Reverse Conducting Switching Device Anti-Parallel Rectifier
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Solution Overview
Problem
Reverse conducting switching devices experience high dynamic switching losses due to reverse recovery current, which affects their switching characteristics in electronic circuits.
Innovation Solution
Incorporating a rectifying device anti-parallel to the switching device, with transistor cells configured for desaturation, to manage charge carrier plasma density and reduce reverse recovery current by altering the I/V characteristics during desaturation and saturation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If transistor cells are turned on during desaturation period to reduce charge carrier plasma, then reverse recovery current is reduced, but switching losses increase due to extended conduction time
Solution Approach 1:
The patent applies dynamics by making the transistor cells switchable between on and off states depending on the operating phase. During the desaturation period, the transistor cells are turned on to reduce charge carrier plasma density. During normal conduction, they are turned off to maintain low resistance. This dynamic switching resolves the contradiction by having the cells serve different functions at different times.
Solution Approach 2:
The patent applies preliminary action by turning on the transistor cells during a desaturation period that precedes the main commutation event. This preliminary action reduces the charge carrier plasma density before the actual switching occurs, thereby reducing the reverse recovery current magnitude when the body diode blocks and reverse recovery current flows.
2Loss of energy
If transistor cells remain off to maintain low resistance state, then conduction losses are reduced, but reverse recovery current increases during switching transitions
Solution Approach 1:
The patent uses dynamic switching of the transistor cells to resolve this contradiction. The cells remain off during normal operation to maintain low resistance and minimize conduction losses. Before switching transitions, they are temporarily turned on to reduce charge carrier plasma, thereby reducing reverse recovery current. This dynamic behavior allows the system to optimize for different operating conditions at different times.
Solution Approach 2:
The patent applies periodic action through the cyclic switching of transistor cells. The cells are periodically turned on during desaturation periods preceding commutation events, and turned off during normal conduction periods. This periodic switching pattern allows the system to periodically reduce charge carrier plasma density while maintaining low resistance during steady-state operation.
3Reliability
If a safety period is provided after desaturation to restore blocking capability, then switching reliability is improved, but charge carrier plasma partially recovers reducing desaturation effectiveness
Solution Approach 1:
The patent applies preliminary action by providing a safety period after the desaturation period during which the transistor cells are turned off to allow the semiconductor portion to restore its blocking capability. This safety period is planned and timed in advance to ensure proper switching sequence and reliability, accepting that some charge carrier plasma recovery occurs but is managed within design parameters.
Solution Approach 2:
The patent applies beforehand cushioning by designing a safety period that acts as a buffer between the desaturation period and the actual commutation. This safety period allows the blocking capability to be restored in advance, providing a cushion or margin of safety that prevents premature commutation before blocking is fully restored, thereby ensuring switching reliability.
4Loss of energy
If rectifying device has low voltage drop to reduce power loss, then energy efficiency improves, but ability to suppress charge carrier injection is reduced
Solution Approach 1:
The patent applies local quality by having different parts of the system serve different functions. The rectifying device is designed with low voltage drop to minimize power loss during normal operation. The transistor cells are designed with specific characteristics to suppress charge carrier injection during desaturation. Each component has optimized local properties suited to its primary function while working together to achieve overall system goals.
Solution Approach 2:
The patent uses the transistor cells as an intermediary between the rectifying device and the semiconductor portion. The transistor cells mediate the charge carrier injection process by being switchable to block injection during desaturation while allowing the rectifying device to operate with low voltage drop during normal conduction. This intermediary role resolves the contradiction by separating the functions of power efficiency and injection suppression into different operational phases.
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 improves switching characteristics by reducing switching losses and enhancing reliability against critical circuit conditions, while maintaining high desaturation efficiency and safety.
Implementation Method 1
A pn junction of the forward biased body diode injects charge carriers of both conductivity types that flood the semiconductor portion of the switching device and build up a dense charge carrier plasma
Implementation Method 2
When the bias changes from reverse to forward, the body diode blocks and a reverse recovery current relieves the charge carrier plasma
Data Source
AI summary
An electric assembly includes a reverse conducting switching device and a rectifying device. The reverse conducting switching device includes transistor cells for desaturation configured to be, under reverse bias, turned on in a desaturation mode and to be turned off in a saturation mode. The rectifying device is electrically connected anti-parallel to the switching device. In a range of a diode forward current from half of a maximum rating diode current of the switching device to the maximum rating diode current, a diode I/V characteristic of the rectifying device shows a voltage drop across the rectifying device higher than a saturation I/V characteristic of the switching device with the transistor cells for desaturation turned off and lower than a desaturation I/V characteristic of the switching device with the transistor cells for desaturation turned on.