Parallel Switching Control for Lower-Loss Power Conversion
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Solution Overview
Problem
Existing power conversion devices struggle to reduce maximum switching losses in switching elements connected in parallel, especially due to variations in characteristics like threshold voltages and gate voltages, without increasing manufacturing steps or costs.
Innovation Solution
The power conversion device employs a control unit that adjusts the turn-on and turn-off start times of switching elements to equalize switching losses, even with variations in characteristics, by selecting each switching element as a target for turn-on and turn-off operations in alternating cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If switching elements are connected in parallel to increase power conversion capacity, then the power conversion capacity is increased and device size is reduced, but switching losses increase due to variations in characteristics such as threshold voltages and gate voltages
Solution Approach 1:
The control unit pre-adjusts the gate voltage application timing for each switching element based on its individual characteristics (threshold voltage, gate voltage requirements) before the switching operation. This preliminary customization of control parameters ensures that each switching element operates optimally despite manufacturing variations, thereby reducing switching losses while maintaining high power conversion capacity
Solution Approach 2:
The invention applies different gate voltage timing adjustments to each switching element according to its specific characteristics. Rather than using a uniform control approach, the control unit tailors the gate voltage application timing locally for each switching element, optimizing its switching performance and minimizing individual switching losses that would otherwise accumulate in parallel configurations
2Manufacturing precision
If gate resistance is increased to equalize currents in parallel switching elements, then current distribution is improved, but switching speed decreases and switching loss increases
Solution Approach 1:
Instead of changing the physical gate resistance parameter, the invention changes the timing parameter of gate voltage application. The control unit adjusts when gate voltage is applied to each switching element based on its characteristics, achieving current equalization through temporal parameter adjustment rather than resistive parameter change, thus maintaining fast switching speeds while ensuring uniform current distribution
3Loss of energy
If switching characteristics are measured and controlled in a variable manner to equalize switching losses, then switching loss distribution is improved, but manufacturing steps and cost increase significantly
Solution Approach 1:
The control unit automatically determines the optimal gate voltage timing for each switching element based on pre-stored characteristic data, without requiring external measurement or manual adjustment during manufacturing. The system self-configures the switching control parameters by referencing the stored characteristics, achieving switching loss equalization through automated control rather than complex manufacturing processes
Data Source
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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.