Switched-Mode Power Converter Delay Compensation
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Solution Overview
Problem
Switched-mode power converters face challenges in accurately controlling the off-time of electronic switches due to delays, leading to inefficiencies and variations in output power delivery, especially when dealing with varying input voltages and loads.
Innovation Solution
A method is introduced where the off-threshold for switching off the electronic switch is dynamically calculated by compensating for delay times using a compensation offset, which is based on measured and estimated delay times from previous drive cycles, allowing for precise control of the off-time and maintaining a constant output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the off-time of electronic switches is controlled without delay compensation, then the control circuit is simpler, but the output power delivery varies and efficiency decreases
Solution Approach 1:
The control circuit measures the actual delay time between the drive signal and switch off-time, then feeds back this information to adjust the off-threshold calculation. This closed-loop feedback mechanism compensates for delay variations without requiring overly complex predetermined compensation circuits, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The system dynamically adjusts the off-threshold parameter based on measured delay times and operating conditions. By changing the off-threshold parameter adaptively rather than using fixed values, the system achieves precise off-time control while keeping the control circuit relatively simple through parameter optimization rather than structural complexity.
2Measurement precision
If delay compensation is implemented using fixed offset values, then the control circuit is simpler, but the compensation accuracy decreases under varying input voltages and loads
Solution Approach 1:
The off-threshold is calculated dynamically in each drive cycle based on the measured delay time from the previous cycle and current operating conditions. This dynamic adjustment allows the system to adapt to varying input voltages and loads while maintaining accurate delay compensation, resolving the contradiction between compensation accuracy and adaptability.
Solution Approach 2:
The control circuit performs preliminary measurement of the delay time in each drive cycle and uses this information to pre-calculate the appropriate off-threshold for the next cycle. This preliminary action enables accurate compensation under varying conditions without requiring complex real-time adjustment mechanisms during critical switching periods.
3Manufacturing precision
If the off-threshold is calculated without considering delay time, then the calculation is faster, but the on-time control precision deteriorates
Solution Approach 1:
The control circuit uses the delay time measured in one drive cycle to compensate for delay in the next cycle, creating a self-sustaining compensation mechanism. This self-service approach maintains high on-time control precision without requiring complex real-time calculations during each switching event, thus minimizing calculation time loss.
Data Source
AI summary
In accordance with an embodiment, a method includes driving an electronic switch in a switched-mode power converter in successive drive cycles, wherein driving the switch in each of the drive cycles comprises switching on the electronic for an on-period and subsequently switching off the electronic switch for an off-period. The method further includes establishing the on-period based on a comparison of an on-time signal with an off-threshold, calculating the off-threshold based on an output signal of the switched-mode power converter and a compensation offset, and calculating the compensation offset in one drive cycle based on an estimated delay time, wherein the estimated delay time is calculated based on a measured delay time and an estimated delay time of a previous drive cycle.