1. Pulse Width Modulation Based On Phase Locked Loop
P. Wisartpong, J. Koseeyaporn, P.Wardkein
Department of Telecommunication Engineering, Faculty of Engineering
King Mongkut’s Institute of Technology Ladkrabang
Bangkok, THAILAND

2. Outline Introduction to PWM signal generating
An Analytical Phase Shifter and PWM [2]
The Proposed Phase Shifter and PWM
R-S Flip-Flop Phase Detector
Experimental and Result
Conclusions

3. Introduction (1)
Natural Sampling
Uniform Sampling

4. Introduction (2)
In 2000, M. Siripruchyanun et al. proposed a PWM signal generating circuit using CCII [1].
In 2001, M. J. Nasila reported the patent name “Phase Locked Loop Pulse Width Modulation System” in the US, which is the PWM construction with phase locked loop and the constant carrier PWM signal is obtained [2].
Later in 2005, Y. Zheng and his colleague also proposed PWM signal generating with phase locked loop technique but the proposed circuit was complicated [3].

5. An Analytical Phase Shifter and PWM [2]
Figure2. Block diagram of a phase shifter and PWM [2].

6. An Analytical Phase Shifter and PWM [2]
By taking inverse Laplace transform
If function
and
are not a function of time.

7. The Proposed Phase Shifter and PWM
Figure3. Block diagram of the propose phase shifter

8. The Proposed Phase Shifter and PWM
By taking inverse Laplace transform
If function
and
are not a function of time.

9. Ex-OR GATE PHASE DETECTOR
Timing diagram of a phase detector

10. R-S FLIP-FLOP PHASE DETECTOR
Figure4. R-S flip-flop phase detector schemes.
Figure5. Timing diagram of a phase detector

11. The relationship between and If is a time varying signal
Model from [2]
Proposed

12. Experimental
The circuit proposed by [2] (see Fig. 2) where a phase detector used is based on an EX-OR gate.
The proposed circuit (see Fig. 3) where a phase detector used is based on an EX-OR gate.
The proposed circuit (see Fig. 3) where a phase detector used is based on an R-S F/F.

13. Experimental Result (1)
Figure6. Phase shifting versus input voltage.

14. Experimental Result (2)
Figure7. Input signal and PWM signal

15. Experimental Result (3)
Figure8. Total harmonics distortion response.

16. Conclusions
In this paper, a new structure of the PWM circuit based on PLL is presented. The mathematical analysis and experimental results of the proposed circuit shows that this circuit provides superior performance than the compared circuit.
The compared results of total harmonic distortion clearly confirm the improved performance of the proposed circuit over the compared circuit structures.
In addition, a phase detector based an R-S F/F and a multi-vibrator is employed in the proposed circuit. It provides wider range of phase detection compared to that of using an EX-OR gate.