Power Converter Switching Loss Reduction via Segmented Bridge Control
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Solution Overview
Problem
Existing current converters for electrically driven vehicles experience significant power losses due to switching losses in power transistors, particularly at high switching frequencies and low currents, which are exacerbated by the simultaneous switching of parallel-connected transistors.
Innovation Solution
A current converter with a bridge circuit and control device that thermally couples switching elements within parallel circuit arrangements, allowing for selective switching based on load conditions to minimize switching losses, and optimizing the number of switching elements active during a cycle to reduce power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If parallel-connected transistors are switched simultaneously to increase power capacity, then the power output is improved, but switching losses increase substantially
Solution Approach 1:
The patent divides the parallel-connected transistor group into multiple sub-groups, where each sub-group can be switched independently. This segmentation allows selective activation of transistors based on load requirements, reducing the total number of switching operations while maintaining the required power output capacity.
Solution Approach 2:
The patent implements dynamic switching control where the switching state of parallel-connected transistors is adjusted in real-time based on the instantaneous power demand. During low-power periods, fewer transistors are switched, reducing switching losses. During high-power periods, more transistors are activated to meet the power requirement, thus dynamically optimizing the trade-off between power output and energy loss.
2Speed
If switching frequency is increased to improve response time, then the response speed is improved, but switching losses become a substantial proportion of total power loss
Solution Approach 1:
The patent maintains continuous power delivery through optimized switching sequences that ensure at least one transistor in each parallel group remains conductive during transitions. This continuity reduces the frequency of complete switching cycles, thereby reducing switching losses while maintaining the required response time for power delivery.
Solution Approach 2:
The patent dynamically adjusts switching parameters such as duty cycle and switching timing based on load conditions. By optimizing these parameters, the system achieves fast response times when needed while minimizing the duration and frequency of high-loss switching events, thus reducing overall switching losses.
3Power
If multiple transistors are operated at high current density to meet power demand, then the power output is improved, but overlapping high current density and high applied voltage cause substantial switching losses
Solution Approach 1:
The patent applies preliminary gating where transistors are pre-biased or pre-charged before full power switching events. This preliminary action reduces the voltage-current overlap during switching transitions by preparing the transistor states in advance, thereby minimizing switching losses while maintaining the ability to deliver high power when required.
Data Source
AI summary
A power converter including a bridge circuit is provided. The power converter is designed to convert a direct current of a current source into an alternating current and/or an alternating current into a direct current. The bridge circuit includes a first parallel circuit assembly, which is coupled to a higher potential of the current source and which has a plurality of switching elements connected in parallel, a second parallel circuit assembly, which is coupled to a lower potential of the current source and which has a plurality of switching elements connected in parallel, and a plurality of taps, which are each coupled to the first and second parallel circuit assemblies. Each switching element of the first and the second parallel circuit assemblies has two conducting connections and a control connection, which controls the flow of current from one conducting connection to the other conducting connection. The power converter also includes a control device, which is designed in such a way that, when the power converter is operated at partial load, at least one switching element of a parallel circuit assembly is controlled in such a way that said switching element is not switched on during at least one cycle. The switching elements of a parallel circuit assembly are thermally coupled to one another.