Fig. 1. Equivalent circuit of single-side compressor of refrigerator

Fig. 2. Variation results of equivalent resistance and equivalent inductance of compressor with frequency

Fig. 3. Traditional cryocooler drive full bridge inverter circuit

Fig. 4. MOS transistor driving signal and output waveform under traditional driving method

Fig. 5. Freewheeling path after half wave under traditional driving mode

Fig. 6. Working loop for zero voltage freewheeling through the upper circuit

Fig. 7. MOS transistor driving signal and output waveform of upper loop freewheeling method

Fig. 8. Control signal processing logic of upper loop freewheeling method

Fig. 9. Working loop for zero voltage freewheeling through lower loop

Fig. 10. MOS transistor driving signal and output waveform of lower loop freewheeling method

Fig. 11. Typical working circuit of IR2110

Fig. 12. Frequency spectrum of lower loop freewheeling method and bipolar driving method

Fig. 13. Improved method 2 cryocooler driving circuit

Fig. 14. Improved method 2 (a) output voltage and (b) current waveform of 120 Hz drive

Fig. 15. Improved method 2 (a) output voltage and (b) current waveform of 360 Hz drive

Fig. 16. Photo of experimental test platform

Fig. 17. Traditional driving methods drive output voltage waveforms at (a) 120 Hz and (b) 360 Hz frequencies

Fig. 18. Improved method 2 drive output voltage waveforms at (a) 120 Hz and (b) 360 Hz frequencies

Fig. 19. Traditional driving methods drive the output voltage spectrum at (a) 120 Hz and (b) 360 Hz frequencies

Fig. 20. Improved method 2 drive the output voltage spectrum at (a) 120 Hz and (b) 360 Hz frequencies