Power electronics application: What is a zero-voltage switch (ZVS) primarily used for in high-current switching to a load?

Introduction:
Zero-voltage switching (ZVS) is a soft-switching technique in power electronics. By turning on a switch when the across-switch voltage is near zero, switching losses and electromagnetic interference (EMI) are significantly reduced. This question targets the main purpose of ZVS in practical converters and AC controllers.

Given Data / Assumptions:

• Switching of high current into a load.
• Concern about EMI/radiated high-frequency energy and switching losses.
• Soft-switching strategy is employed.

Concept / Approach:
Hard switching at non-zero voltage produces high dv/dt and di/dt, causing loss and EMI. ZVS (or zero-current switching, ZCS) minimizes one of these by timing transitions at a natural zero crossing (e.g., AC line zero crossing or resonant transition), reducing spectral content and heating. Therefore ZVS is used primarily to reduce high-frequency radiation and losses during turn-on (and/or turn-off).

Step-by-Step Solution:

Verification / Alternative check:
Comparative spectra of hard- vs soft-switched converters show reduced high-frequency components under ZVS. Thermal measurements also indicate lower switching loss.

Why Other Options Are Wrong:

• Control low-voltage circuits: Too generic; not the defining purpose of ZVS.
• Provide backup power: That is the role of UPS or hold-up circuits.
• Extremely low-voltage applications: ZVS is about switching conditions, not absolute voltage level.

Common Pitfalls:
Confusing ZVS with ZCS; both are soft-switching but minimize different stress terms. Also, mixing “zero crossing relay” for AC mains with resonant ZVS converters—they aim at similar benefits but via different mechanisms.

Final Answer:
To reduce radiation of high frequencies during turn-on of a high current to a load