A Real-Time Digital Control with Variable Switching Frequency for ZVS Four-Switch Converter

Abstract

A new variable switching frequency real-time digital control method for a four-switch converter with zero voltage switching (ZVS) is presented in this paper. To overcome the drawbacks of conventional fixed-frequency techniques, the suggested control method dynamically modifies the switching frequency to maximize efficiency and reduce switching losses. To achieve precise regulation and adaptive operation, a microcontroller or FPGA is used to implement a real-time digital control system. The effectiveness of the suggested strategy is confirmed by simulation and experimental results, which show enhanced efficiency, transient response, and thermal management.

Introduction

1. Introduction

Power electronic converters are critical in modern systems such as electric vehicles, renewable energy systems, and industrial power supplies. Among various converter topologies, the four-switch converter has gained attention due to its:

• Lower component count

• Reduced cost

• Improved efficiency compared to six-switch designs

2. Challenges with Traditional PWM

• Uses fixed switching frequency

• Leads to high switching losses, electromagnetic interference (EMI), and reduced efficiency under varying loads

• Especially problematic in high-power and thermally sensitive applications

3. Zero Voltage Switching (ZVS) & Motivation for Improvement

• ZVS reduces switching losses and heat, improving reliability and performance

• Maintaining ZVS across all load conditions is difficult

• Solution Proposed: Variable Switching Frequency Control using real-time digital systems (DSP or FPGA) to:

  • Dynamically adjust frequency

  • Enhance thermal performance

  • Improve efficiency and EMI behavior

4. ZVS Four-Switch Converter Design

• Uses a buck-type converter equation:
  Vo=D⋅VinV_o = D \cdot V_{in}Vo?=D⋅Vin?

• ZVS condition:
  Lr⋅dILdt=Cr⋅dVswdtL_r \cdot \frac{dI_L}{dt} = C_r \cdot \frac{dV_{sw}}{dt}Lr?⋅dtdIL??=Cr?⋅dtdVsw??

• Optimal switching frequency:
  fs=12πLrCrf_s = \frac{1}{2\pi \sqrt{L_r C_r}}fs?=2πLr?Cr??1?

• Real-time control dynamically tunes switching frequency to:

  • Match load conditions

  • Maintain ZVS

  • Minimize conduction and switching losses

5. Variable Switching Frequency Control Strategy

• Dynamically adjusts switching frequency using:

  • Inductor current

  • Resonant circuit parameters

• Control law:

  fs=fs0(1+k⋅ILIL,ref)f_s = f_{s0} \left(1 + k \cdot \frac{I_L}{I_{L,ref}} \right)fs?=fs0?(1+k⋅IL,ref?IL??)

• Benefits:

  • Maintains ZVS across varying conditions

  • Reduces switching losses and thermal stress

  • Minimizes EMI by spreading spectral energy

  • Improves efficiency, component lifespan, and acoustic performance

6. Experimental Setup

• Includes:

  • A four-switch half-bridge converter

  • DSP/FPGA-based real-time controller

  • Voltage and current sensors

  • Adaptive control algorithm

7. Simulation and Experimental Results

• Simulation in MATLAB/Simulink and real-world hardware testing confirm:

  • Reduced switching losses

  • Consistent ZVS operation

  • Efficiency gain of 5–10% over fixed-frequency methods

  • Lower device temperatures (by ~15°C)

  • Improved EMI performance

  • Better transient/load response

Conclusion

In order to address the main issues of power conversionefficiency, thermal management, and transient response, thispaper has proposed a novel variable switching frequency real-time digital control strategy for a ZVS four-switch converter.The suggested technique effectively reduces switching losses,preserves ideal ZVS conditions, and improves system performanceby dynamically varying the switching frequency.System efficiency and operational reliability are significantlyimproved when compared to traditional fixed-frequency control methods.

References

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Copyright

Copyright © 2025 Mukesh Kumar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.