Power Converter Voltage Drop Compensation
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Solution Overview
Problem
In power converter devices using synchronous rectification, the voltage drop cannot be accurately compensated due to current division between switching elements and freewheeling diodes, leading to inaccuracies in output voltage.
Innovation Solution
A power converter device design that calculates and compensates for voltage drops across semiconductor elements using a current sensor to detect output current and ON-time ratios, allowing for precise correction of voltage commands and improved accuracy in output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification is used to reduce loss, then energy efficiency is improved, but voltage drop compensation becomes inaccurate due to current division between switching elements and freewheeling diodes
Solution Approach 1:
The patent performs preliminary calculation of voltage drops using pre-stored characteristic data before generating the voltage command. By calculating the expected voltage drops based on predicted current values and switching patterns, the system can compensate for these drops in advance, ensuring accurate output voltage even when current division occurs in synchronous rectification mode.
Solution Approach 2:
The patent implements feedback by detecting actual output current, comparing it with the voltage command, and adjusting the voltage command based on the detected current and stored characteristic data. This closed-loop feedback mechanism enables accurate voltage drop compensation by continuously adapting to actual operating conditions, resolving the inaccuracy caused by current division.
2Measurement precision
If current sensors are provided at upper arm and lower arm to judge current flow direction for voltage drop compensation, then output voltage accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the single output current sensor serve multiple functions: it detects output current for both voltage drop compensation calculations and output voltage control. By storing characteristic data that relates output current to voltage drops in both upper and lower arms, the system can derive compensation values from a single sensor reading, eliminating the need for separate current sensors in each arm.
Solution Approach 2:
The patent creates a virtual model of the semiconductor device characteristics by storing voltage drop characteristic data in memory. This copied characteristic data allows the control unit to simulate and calculate voltage drops without directly measuring currents in each arm, replacing complex physical measurement arrangements with a simplified computational model.
3Measurement precision
If voltage drop compensation is performed by judging current flow direction, then output voltage accuracy is improved, but the method becomes inapplicable when current is divided between multiple semiconductor elements
Solution Approach 1:
The patent changes the approach from binary current direction judgment to continuous parameter-based calculation. By storing voltage drop characteristic data that varies with current magnitude and using this data to calculate compensation values based on detected output current, the system can handle continuous current division in synchronous rectification rather than relying on discrete current direction states.
Solution Approach 2:
The patent replaces the mechanical/judgment-based current direction detection method with a computational approach using stored characteristic data and mathematical calculations. This substitution allows the system to handle complex current division scenarios through calculation rather than simple directional judgment, making the compensation method applicable to synchronous rectification.
Data Source
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AI summary
There is provided a power converter device in which a current is divided to flow in a plurality of semiconductor elements and a voltage drop is compensated so as to obtain an output voltage with high accuracy. In a power converter device wherein a leg (21) comprises two semiconductor device groups which are connected in series and a division current is generated in a current which flows in the semiconductor device group between elements in the semiconductor device groups, a current sensor (26) which detects a current which flows in the semiconductor device group, a voltage command generation unit (31) which calculates a voltage command value to be output, a voltage drop calculating unit (32) which calculates a voltage drop of the semiconductor device group by using a current value which is detected by the current sensor (26) and voltage drop characteristics including a division characteristic of the semiconductor device group and a switching control unit (33) which corrects a voltage command value which is generated by the voltage command generation unit by using the voltage drop which is calculated so as to control ON/OFF of the switching element are provided.