PWM Controller for Bridge Circuit Switching Loss Reduction
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Solution Overview
Problem
Conventional power conversion apparatuses face challenges in accurately controlling switching elements in bridge circuits for efficient DC to AC power conversion, particularly in maintaining optimal on and off periods, leading to inefficiencies and increased switching losses.
Innovation Solution
A power conversion apparatus incorporating a PWM controller that alternately controls switching elements Q1 and Q2 based on a carrier wave signal, ensuring consistent on and off periods and reducing the need for shortening these periods, even at low voltage outputs, thereby enhancing voltage accuracy and minimizing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PWM control is used to convert DC to AC power, then power conversion is achieved, but switching losses increase and voltage accuracy deteriorates
Solution Approach 1:
The patent applies periodic action by using a carrier wave signal with a fixed period to control the switching elements. The PWM controller generates control signals that repeat periodically, ensuring consistent on-periods and off-periods for each switching element. This periodic control mechanism maintains optimal switching timing, reducing switching losses while preserving voltage accuracy through regular, predictable switching cycles.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the duty cycle of the PWM control signals while maintaining a fixed carrier wave period. The PWM controller varies the on-period duration relative to the constant off-period, allowing efficient power conversion at different voltage levels without compromising switching element performance or voltage accuracy.
2Loss of energy
If on-periods are shortened to reduce switching losses, then switching efficiency improves, but voltage output accuracy deteriorates
Solution Approach 1:
The patent maintains a fixed carrier wave period to ensure consistent timing cycles. By keeping the off-period constant and only varying the on-period through PWM duty cycle adjustment, the system achieves efficient switching without compromising voltage accuracy. The periodic nature of the control signals ensures predictable switching behavior that preserves output precision.
Solution Approach 2:
The patent implements dynamic control by allowing the on-period to vary while keeping the off-period fixed. This dynamic adjustment of the on-period duration, controlled by PWM duty cycle variations, enables the system to optimize switching efficiency at different operating points while maintaining voltage output accuracy through the stable, fixed off-period timing.
3Adaptability or versatility
If switching elements are controlled with variable on-periods, then power conversion flexibility increases, but switching losses increase
Solution Approach 1:
The patent reduces switching losses by implementing a fixed off-period for each switching element through periodic carrier wave control. While the on-period varies to provide power conversion flexibility, the consistent off-period ensures that each switching element has a stable recovery time, minimizing switching losses regardless of the on-period duration or power conversion requirements.
Data Source
AI summary
A power conversion apparatus includes a power converter and a PWM controller. A first switching element is coupled to a positive pole of a DC power source and one terminal of a load. A second switching element is coupled to a negative pole of the DC power source and another terminal of the load. A third switching element is coupled to the positive pole and the other terminal. A fourth switching element is coupled to the negative pole and the one terminal. The PWM controller PWM-controls the power conversion apparatus to repeat an on-period during which the DC power source outputs a voltage to the load and an off-period during which no voltage is output. The PWM controller alternately controls the first and second switching elements based on a signal set at a high or low level any time during a carrier wave period.