**ABSTRACT:** Solid-state switch mode AC-DC converters having high-frequency transformer isolation are developed in buck, boost, and buck-boost configurations with improved power quality in terms of reduced total harmonic distortion (THD) of input current, power-factor correction (PFC) at AC mains and precisely regulated and isolated DC output voltage feeding to loads from few Watts to several kW. This paper presents a comprehensive study on state of art of power factor corrected single-phase AC-DC converters configurations, control strategies, selection of components and design considerations, performance evaluation, power quality considerations, selection criteria and potential applications, latest trends, and future developments. Simulation results as well as comparative performance are presented and discussed for most of the proposed topologies.

** **

**INDEX TERMS***:* AC-DC converters, harmonic reduction, high-frequency (HF) transformer isolation, improved power quality converters, power-factor correction.

** **

**SOFTWARE****:** MATLAB/SIMULINK

Fig. 1. Classification of improved power quality single-phase AC-DC converters with HF transformer isolation.

**CIRCUIT CONFIGURATIONS**

*A. Buck AC-DC Converters*

Fig. 2. Buck forward AC-DC converter with voltage follower control.

Fig. 3. Buck push-pull AC-DC converter with voltage follower control.

Fig. 4. Half-bridge buck AC-DC converter with voltage follower control.

Fig. 5. Buck full-bridge AC-DC converter with voltage follower control

* B. **Boost AC-DC Converters*

Fig. 6. Boost forward AC-DC converter with current multiplier control.

Fig. 7. Boost push-pull AC-DC converter with current multiplier control.

Fig. 8. Boost half-bridge AC-DC converter with current multiplier control.

Fig. 9. Boost full-bridge AC-DC converter with current multiplier control.

* C. **Buck-Boost AC-DC Converters*

Fig. 10. Flyback AC-DC converter with current multiplier control.

Fig. 11. Cuk AC-DC converter with voltage follower control.

Fig. 12. SEPIC AC-DC converter with voltage follower control.

Fig. 13. Zeta AC-DC converter with voltage follower control.

**SIMULATION RESULTS:**

Fig. 14. Current waveforms and its THD for buck AC-DC converter topologies in CCM. (a) Forward buck topology (Fig. 2).( b) Push-pull buck topology (Fig. 3). (c) Half-bridge buck topology (Fig. 4). (d) Bridge buck topology (Fig. 5).

Fig. 15. Current waveforms and its THD for boost AC-DC converter topologies in CCM. (a) Forward boost topology (Fig. 6). (b) Push-pull boost topology (Fig. 7). (c) Half-bridge boost topology (Fig. 8). (d) Bridge boost topology (Fig. 9).

Fig. 16. Current waveforms and its THD for buck-boost AC-DC converter topologies in CCM. (a) Flyback topology (Fig. 10). (b) Cuk topology (Fig. 11). (c) SEPIC topology (Fig. 12). (d) Zeta topology (Fig. 13).

Fig. 17. Current waveforms and its THD for buck AC-DC converter topologies in DCM. (a) Forward buck topology (Fig. 2). (b) Push-pull buck topology (Fig. 3). (c) Half-bridge buck topology (Fig. 4). (d) Bridge buck topology (Fig. 5).

Fig. 18. Current waveforms and its THD for boost AC-DC converter topologies in DCM. (a) Forward boost topology (Fig. 6). (b) Push-pull boost topology (Fig. 7).

Fig. 19. Current waveforms and its THD for buck-boost AC-DC converter topologies in DCM. (a) Flyback topology (Fig. 10). (b) Cuk topology (Fig. 11). (c) SEPIC topology (Fig. 12). (d) Zeta topology (Fig. 13).

**CONCLUSION**

A comprehensive review of the improved power quality HF transformer isolated AC-DC converters has been made to present a detailed exposure on their various topologies and its design to the application engineers, manufacturers, users and researchers. A detailed classification of these AC-DC converters into 12 categories with number of circuits and concepts has been carried out to provide easy selection of proper topology for a specific application. These AC-DC converters provide a high level of power quality at AC mains and well regulated, ripple free isolated DC outputs. Moreover, these converters have been found to operate very satisfactorily with very wide AC mains voltage and frequency variations resulting in a concept of universal input. The new developments in device technology, integrated magnetic and microelectronics are expected to provide a tremendous boost for these AC-DC converters in exploring number of additional applications. It is hoped that this exhaustive design and simulation of these HF transformer isolated AC-DC converters is expected to be a timely reference to manufacturers, designers, researchers, and application engineers working in the area of power supplies.

**REFERENCES**

[1] *IEEE Recommended Practices and Requirements for Harmonics Control in Electric Power Systems*, IEEE Standard 519, 1992.

[2] *Electromagnetic Compatibility (EMC) – Part 3: Limits- Section 2: Limits for Harmonic Current Emissions *(*equipment input current *16* A per phase*), IEC1000-3-2 Document, 1st ed., 1995.

[3] A. I. Pressman*, Switching Power Supply Design*, 2nd ed. New York: McGraw-Hill, 1998.

[4] K. Billings*, Switchmode Power Supply Handbook*, 2nd ed. NewYork: McGraw-Hill, 1999.

[5] N. Mohan, T. Udeland, and W. Robbins*, Power Electronics: Converters, Applications and Design*, 3rd ed. New York: Wiley, 2002.