Power Conversion Device Reverse Recovery Current Suppression
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Solution Overview
Problem
In power conversion devices, the reverse recovery current in free-wheeling diodes leads to significant heat generation, which needs to be reduced to prevent thermal issues and improve efficiency.
Innovation Solution
The implementation of auxiliary circuits with timers and comparators that control switching elements to apply auxiliary power in a reverse direction, suppressing the free-wheeling current and reducing the reverse recovery current by shortening the free-wheeling and reverse recovery times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the other switching element is turned on when free-wheeling current flows, then the power conversion device can operate with standard switching elements, but large heat generation occurs in the free-wheeling diode due to reverse recovery current
Solution Approach 1:
The auxiliary circuit applies a reverse voltage to the free-wheeling diode before the main switching element turns on, preemptively suppressing the reverse recovery current that would otherwise flow when the switching element is turned on during free-wheeling current flow. This preliminary counter-action prevents the harmful effect before it occurs.
Solution Approach 2:
An auxiliary switching element is introduced as an intermediary component between the main switching element and the free-wheeling diode. This auxiliary element controls the application of reverse voltage to suppress reverse recovery current, acting as a mediator that enables safe switching operations without directly exposing the main switching element to the harmful reverse recovery effects.
2Loss of energy
If auxiliary circuits are added to suppress reverse recovery current, then heat generation is reduced, but device complexity increases
Solution Approach 1:
The auxiliary circuit components (auxiliary switching element, timer, and comparator) are integrated into the existing power conversion device architecture. The timer and comparator share control signals with the main switching elements, and the auxiliary switching element is placed in parallel with the existing circuit structure, merging multiple functions into a unified system rather than adding completely separate components.
Solution Approach 2:
The invention changes the operational parameters of the free-wheeling diode by dynamically applying reverse voltage through the auxiliary circuit. By controlling the timing and magnitude of the reverse voltage application, the system suppresses reverse recovery current without requiring fundamental changes to the diode structure or main circuit topology.
Data Source
AI summary
A power conversion device includes a first switch and a second switch connected in series between a positive electrode and a negative electrode of a first power supply. A first node is between the first and second switches. The first node can be connected to a load. A first diode has an anode connected to the first node and a cathode connected to the positive electrode of the first power supply. A third switch is connected between a positive electrode of a second power supply and the positive electrode of the first power supply. A first timer is connected to a gate electrode of the third switch. A first comparator has a first input that is connected to a gate electrode of the first switch, a second input at which a reference voltage can be received, and an output that is connected to the first timer.