Power Converter Gate Timing for Parallel Switch Loss Balancing
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Solution Overview
Problem
Existing power conversion devices with switching elements connected in parallel face challenges in reducing maximum switching losses due to variations in characteristics like threshold voltages and gate voltages, and existing solutions either increase manufacturing steps or costs.
Innovation Solution
A power conversion device with a control unit that selectively adjusts the turn-on and turn-off timing of switching elements to equalize switching losses without requiring additional components or increased manufacturing steps, by setting specific time periods for each switching element based on its characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If switching elements are connected in parallel to increase power conversion capacity, then the device can be downsized, but switching losses increase due to variations in characteristics such as threshold voltages and gate voltages
Solution Approach 1:
The patent applies local quality by setting different gate resistance values for different switching elements based on their individual characteristics. Specifically, switching elements with larger inductance in the current path are assigned smaller gate resistance values, while those with smaller inductance are assigned larger gate resistance values. This localized adjustment equalizes switching speeds and reduces switching losses without requiring uniform treatment of all switching elements.
Solution Approach 2:
The patent changes the gate resistance parameter to compensate for variations in switching element characteristics. By adjusting the gate resistance value as a controllable parameter, the patent optimizes the switching speed of each element to minimize switching losses while maintaining the parallel connection configuration for downsizing.
2Loss of energy
If switching characteristics are measured and controlled in a variable manner to equalize switching losses, then maximum switching loss is reduced, but the number of manufacturing steps and manufacturing cost increase greatly
Solution Approach 1:
The patent applies preliminary action by pre-determining the gate resistance values for each switching element based on their characteristics (such as inductance) before operation. This allows the switching losses to be equalized through a simple resistance value selection process rather than requiring complex real-time measurement and variable control, thereby reducing manufacturing complexity while achieving the goal of minimizing switching losses.
Data Source
AI summary
Provided is a control unit of a power conversion device configured to select, in each first set cycle, a first target switching element and a second target switching element from a plurality of switching elements connected in parallel to each other. The control unit performs control so that, at a time of a turn-on operation of a switching circuit, a turn-on start time of the first target switching element is earlier by a first set time period than a turn-on start time of another switching element that is not the first target switching element. The control unit performs control so that, at a time of a turn-off operation of the switching circuit, a turn-off start time of the second target switching element is later by a second set time period than a turn-off start time of another switching element that is not the second target switching element.