Power Converter Current Averaging Beyond Switching Noise
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Solution Overview
Problem
Existing power conversion devices face challenges in accurately calculating output current values due to measurement errors caused by switching noise and time errors in detection timing.
Innovation Solution
A power conversion device comprising a voltage conversion circuit with a switching element, a control circuit for switching control, and a current detection circuit that calculates the average current output based on first and second current values detected in specific switching states and a modulation ratio related to switching control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current detection is performed at switching timing of the inverter, then DC-AC conversion control can be implemented, but measurement errors occur due to mixing of switching noise and time error of detection timing
Solution Approach 1:
The patent applies preliminary action by detecting current values at specific timing (midpoint of switching ON period and midpoint of switching OFF period) before the actual switching event occurs. This timing selection prevents the detection from being contaminated by switching noise and time errors, as the current is measured at stable points in the switching cycle rather than during the transient switching period.
Solution Approach 2:
The patent changes the detection timing parameter from switching timing to midpoint timing of switching periods. By modifying when the current detection occurs (from during switching to at stable midpoints), the measurement accuracy is improved while still maintaining the ability to perform DC-AC conversion control through subsequent average value calculation.
2Ease of operation
If average current is calculated based on detection at switching timing, then control can be performed, but calculation accuracy deteriorates due to measurement errors
Solution Approach 1:
The patent detects current values at predetermined timing (midpoints of switching periods) before performing the average value calculation. This preliminary detection at optimal timing ensures that the raw data used for calculation is free from switching noise contamination, thereby improving the accuracy of the subsequent average current calculation while maintaining ease of control operation.
Solution Approach 2:
The patent uses the detected current values (obtained at optimized timing) as feedback for controlling the inverter operation. By ensuring high accuracy in the detected current values through proper timing selection, the feedback control loop operates more effectively, improving both calculation accuracy and overall control performance.
Data Source
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AI summary
A power conversion device (6) comprises: a voltage conversion circuit (61) having a switching element; a control circuit (60) performing switching control of the voltage conversion circuit (61); and a current detection circuit (63) detecting current output from the voltage conversion circuit (61), and the control circuit (60) calculates an average value of current output from the voltage conversion circuit (61) based on a first current value detected in a first switching state where output of current increases, a second current value detected in a second switching state where output of current decreases and a modulation ratio related to switching control of voltage conversion, and controls operation of the voltage conversion circuit (61) based on a calculated average value.