Inverter Switching Frequency Control for Loss Reduction
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Solution Overview
Problem
Conventional full-bridge inverter circuits experience increased turn-on and turn-off losses, switching noise, and reduced efficiency under light load conditions due to hard switching states, particularly when operated in continuous current mode.
Innovation Solution
A control method that divides the AC output voltage half cycle into two stages, where the upper and lower switch elements are operated at a first switching frequency lower than a preset threshold in the first stage for continuous current mode, and at a second switching frequency in the second stage for discontinuous current mode boundary mode, reducing turn-on and turn-off losses and achieving a soft switch state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter circuit is operated in continuous current mode with fixed switching frequency, then the output voltage and current are maintained, but the turn-on loss and turn-off loss of switch elements increase under light load conditions
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed switching frequency to a variable switching frequency that adapts based on the operating stage. In the first stage, a first switching frequency is used, and in the second stage, a second switching frequency is applied. This dynamic adjustment allows the system to optimize performance and reduce losses under different load conditions while maintaining reliable output.
Solution Approach 2:
The patent changes the switching frequency parameter from a fixed value to a variable parameter that takes different values in different stages. By adjusting the switching frequency based on the operational stage, the system reduces turn-on and turn-off losses in the second stage while maintaining proper output in the first stage, effectively resolving the energy loss issue.
2Measurement precision
If the switching frequency is increased to improve output control, then the output voltage regulation is enhanced, but the switching noise and parasitic oscillation increase
Solution Approach 1:
The patent uses dynamic switching frequency adjustment where the system operates at a first switching frequency in the first stage and switches to a second switching frequency in the second stage. This dynamic approach allows the system to maintain good output voltage regulation while reducing switching noise and parasitic oscillation by using appropriate frequencies for different operational conditions.
Solution Approach 2:
The patent implements periodic action by dividing the operation into distinct stages with different switching frequencies. The system periodically transitions between stages, using the first switching frequency when needed and the second switching frequency to reduce harmful effects, thereby achieving a balance between regulation precision and noise reduction.
3Ease of operation
If the inverter circuit operates in hard switch state, then the switching control is simplified, but the overall efficiency is reduced due to increased switching loss
Solution Approach 1:
The patent maintains ease of operation by using a control method that divides operation into two stages with different switching frequencies. This dynamic approach allows the system to achieve soft switching in the second stage, reducing switching losses, while keeping the control logic relatively simple through stage-based frequency adjustment.
Solution Approach 2:
The patent changes the switching frequency parameter to enable soft switching in the second stage, which reduces switching losses compared to hard switching. By adjusting the frequency parameter based on the operational stage, the system improves efficiency while maintaining manageable control complexity through the two-stage approach.
4Loss of energy
If the switching frequency is reduced to decrease switching loss, then the turn-on loss and turn-off loss are reduced, but the output voltage control precision deteriorates
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the switching frequency based on the operational stage. In the first stage, a higher first switching frequency maintains good output voltage control precision. In the second stage, the system transitions to a second switching frequency that reduces switching losses. This dynamic frequency adjustment allows the system to optimize both precision and efficiency at different times.
Solution Approach 2:
The patent applies periodic action by alternating between two distinct operating stages with different switching frequencies. The system periodically uses the first switching frequency when output precision is critical and the second switching frequency when reducing switching losses is prioritized, achieving a temporal balance between precision and energy efficiency.
Data Source
AI summary
A control method of an inverter circuit includes the following steps. Firstly, a half cycle of the AC output voltage is divided into a first stage and a second stage. Then, the upper switch element and the lower switch element are controlled to be operated at a first switching frequency lower than a preset threshold frequency in the first stage, so that the inverter circuit is operated in a continuous current mode. Then, the upper switch element or the lower switch element of the bridge arm is controlled to be operated at a second switching frequency in the second stage, so that the upper switch element and the lower switch element are turned on at a preset voltage level and the inverter circuit is operated at a discontinuous current mode boundary mode.