Power Conversion Device Zero-Voltage Switching Control
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Solution Overview
Problem
Existing power conversion devices fail to consistently achieve zero-voltage switching, leading to increased power losses during DC/DC conversion.
Innovation Solution
A power conversion device is designed with primary-side and secondary-side converters, each comprising switching legs with snubber capacitors and controlled semiconductor elements, where the capacitance of the snubber capacitors and the control device set a short-circuit prevention period to ensure zero-voltage switching by coordinating the on/off states of semiconductor elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If zero-voltage switching is implemented using snubber capacitors in conventional power conversion devices, then power loss is reduced, but zero-voltage switching cannot be consistently achieved depending on operating conditions
Solution Approach 1:
The invention applies preliminary action by setting a predetermined short-circuit prevention period before the semiconductor switching element turns on. During this period, the control device prevents turn-on of the switching element even if the voltage across it becomes zero, ensuring that the snubber capacitor has fully charged and discharged before switching occurs. This preliminary timing control guarantees consistent zero-voltage switching across all operating conditions, resolving the reliability issue while maintaining low power loss.
2Reliability
If the short-circuit prevention period is extended to ensure reliable zero-voltage switching, then switching consistency improves, but the risk of snubber capacitor short-circuiting increases
Solution Approach 1:
The invention uses feedback by continuously monitoring the voltage across the snubber capacitor and the current through the semiconductor switching element. The control device adjusts the short-circuit prevention period dynamically based on the charging/discharging status of the snubber capacitor. When the capacitor voltage indicates complete charging/discharging, the control device permits switching; otherwise, it extends the prevention period. This feedback mechanism ensures reliable zero-voltage switching while preventing snubber capacitor short-circuits.
3Loss of energy
If snubber capacitors are added to achieve soft switching, then power loss decreases, but device complexity increases
Solution Approach 1:
The invention applies universality by designing the control device to perform multiple functions: it controls the semiconductor switching elements, monitors snubber capacitor voltage, determines charging/discharging completion, and enforces the short-circuit prevention period. This multi-functional control approach integrates the complexity management into a single control unit rather than adding separate circuits, thereby achieving soft switching with minimized additional complexity while reducing power loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device effectively achieves zero-voltage switching, reducing power losses and ensuring efficient DC/DC conversion by adequately setting the short-circuit prevention time.
Implementation Method 1
each including positive-side and negative-side semiconductor elements which are serially connected to each other and which are each provided with a snubber capacitor connected in parallel thereto
Data Source
AI summary
Using two converters placed in a primary-side and a secondary-side and each configured as a single-phase full-bridge, and one single-phase transformer TR, a power conversion device converts DC power of a primary-side capacitor to which a primary-side DC voltage is applied, to DC power of a secondary-side capacitor to which a secondary-side DC voltage is applied, through a transformer. A control device sets a dead time Td1 for the converter serving as a power-transferring side converter, to be equal to or less than a current-polarity reversal time Tcmtt, to thereby surely achieve zero-voltage switching.