Zero-Voltage Switching DC-DC Converter Technologies

Zero-voltage switching (ZVS) DC-DC converters constitute a class of isolated and non-isolated power conversion topologies designed to transfer energy between different voltage levels while virtually eliminating switching losses and electromagnetic interference. By ensuring that power semiconductor devices turn on or off at moments when the voltage across them is (ideally) zero, ZVS techniques enable higher switching frequencies, reduced device stress and compact magnetic components. Common topologies include phase-shifted full-bridge converters, LLC resonant converters, active-clamp forward–flyback converters and hybrid configurations that integrate multiple resonant modes. Each topology employs resonant networks, clamp circuits or adaptive dead-time control to shape voltage and current waveforms during transitions, thereby extending the range of load conditions over which soft-switching is maintained. Recent advances focus on hybrid designs that combine full-bridge and half-bridge stages for high-voltage applications, energy-recovery snubber circuits that recapture leakage-inductance energy, and planar transformers realised on multilayer PCBs to achieve high power density. Adaptive control algorithms, such as fuzzy-logic and dynamic dead-time methods, further broaden the ZVS operational envelope. These innovations underpin ultra-efficient power supplies for electric vehicles, data centres, renewable energy interfaces and aerospace systems, delivering global benefits in energy efficiency, thermal management and system miniaturisation.

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A hybrid DC-DC converter merges a phase-shifted full-bridge stage with a half-bridge LLC stage via a novel clamp circuit comprising two diodes and a capacitor at the transformer centre. By series-connecting full-bridge rectifiers on the secondary side, the design supports high output voltages while improving efficiency, power density and cost. A 3.3 kW prototype demonstrates its viability for demanding high-voltage applications.

An energy-recovery capacitor snubber added to a full-bridge converter operating at 50 kHz achieves soft-switching independently of load current. By harnessing only the magnetising current of the high-frequency transformer for ZVS on the primary side and deploying a simple capacitor snubber on the secondary side, the design removes circulating currents during free-wheeling intervals. A 2 kW laboratory model confirms reduced switching losses and stable soft-switching over a wide load range.

A high-power-density active-clamp converter integrates a planar transformer realised on a four-layer PCB to accommodate wide-input voltage ranges and high-output currents. The low leakage inductance permits higher switching frequencies and a smaller transformer footprint, while the active-clamp topology minimises conduction losses by limiting circulating currents. The result is a compact, cost-competitive topology well suited to low-voltage DC systems in electric vehicles.

Zero-Voltage Switching DC-DC Converter Technologies publication trend

The graph below shows the total number of articles in zero-voltage switching dc-dc converter technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Zero-Voltage Switching (ZVS): A soft-switching technique in which the voltage across a switching device is reduced to zero at turn-on, minimising switching losses and stress.

Phase-Shifted Full-Bridge Converter: An isolated DC-DC topology using controlled phase shifts between bridge legs to achieve ZVS and regulate output voltage.

LLC Resonant Converter: A resonant topology employing two inductors (L) and a capacitor (C) to create soft-switching transitions via a resonant tank circuit.

Active-Clamp Circuit: A network of diodes, capacitors and switches that recycles energy from leakage inductance and enforces soft-switching by clamping voltage.

Energy Recovery Snubber: A snubber circuit that captures and returns energy stored in parasitic inductances or capacitances back to the system.

Planar Transformer: A transformer with windings realised as flat PCB windings, offering high power density, low leakage inductance and compact form factor.

References

1. Hybrid DC–DC Converter With Novel Clamp Circuit in Wide Range of High Output Voltage. IEEE Access (2024).
2. Soft-Switching Full-Bridge DC-DC Converter with Energy Recovery Capacitor Snubber †. Energies (2023).
3. A High-Power-Density Active-Clamp Converter with Integrated Planar Transformer. Energies (2022).