1. A Novel Pulse Shift Modulation
Technique For Controlling Dc-Dc
Converter
Presented by
R.SARAVANAN
1611110016
2nd yr M.Tech(PED)

2. Abstract:
 Pulse Width Modulation Technique (PWM) and Pulse
frequency Modulation Technique(PFM) are commonly used
techniques to generate pulses to control switches in DC-DC
converters.
 The conduction losses and output voltage ripples are
dominant in PWM at High loads, and Switching losses are
dominant in PFM at low loads.
 In proposed a Phase Shift modulation technique, which
dynamically changes the duty cycle and frequency of the
control pulse to control the switches in DC-DC converters.
 This techniques reduces the conduction losses and
ripple voltage inherent in PWM and switching losses
inherent in PFM .

3. Introduction:
 The Load condition in these Portable devices changes extreme
from standby mode to the operating mode.
 PWM technique changes the duty cycle of the control pulse
without altering the frequency.
 PFM technique changes the frequency of the control pulse
without altering the duty cycle.
This inefficiency is due to conduction losses, switching losses
and output voltage ripples.
 PFM technique due to the high switching frequency.

4. Cond…..
 A Pulse Shift Modulation Technique that increases the
efficiency of the DC-DC converters at Wide load ranges.
 This technique dynamically manipulates the switching
frequency and the duty cycle of the control pulse to maintain
a constant output and reduce the losses to both PWM and
PFM techniques.
 At Low load values the switching frequency is manipulated
along with the duty cycle in the PWM technique.
 To Minimize the ripple output voltages and the losses in the
PWM technique.
 At High load values, the duty cycle is manipulated along
with the switching frequency in the PFM technique.
 Lower the switching losses inherent in the PFM technique.

5. Control Pulse Generation through
PSM technique:

6. Description:
The triangular pulse (Vtp) of varying duty cycle and
switching frequency changes dynamically with the change in
the load value.
At each clock cycle, this triangular pulse (Vtp) is compared
to an error voltage (Verr) which corresponds to the difference
between the output voltage (Vout) of the DC-DC converter
and a reference voltage (Vref).
If Verr is higher than Vtp, the control pulse Vcon is driven
high (3.3V); otherwise it is driven low (<0.8V).
One can see that the control pulse Vcon in the PSM
technique has a variable duty cycle ,switching frequency in
contrast to the constant switching frequency in the PWM
technique and the constant duty cycle in the PFM technique.

7. Flow Chart:

8. Circuit Diagram of Buck Converter:

9. Description:
The output voltage at the load is sensed and
converted to a digital signal by an Analog/Digital
converter.
The duty cycle and frequency are determined to
transfer the appropriate amount of power to the load
such that the output voltage remains constant.

10. FPGA-based hardware implementation of
the PSM controlled:

11. Waveform for Duty Cycle:

12. Description of duty cycle at
differential load values:
The duty cycle dynamically changes with the change in
the load condition whereas it is constant in PFM
technique and goes below the minimum value (20%) in
PWM.
This duty cycle is smoothly increased with the increase of
the load value to avoid that the circuit enters in the
discontinuous mode,which corresponds to duty cycles
under 20%.

13. Waveform for Frequency:

14. Description Of Frequency at
Differential Load Values:
The frequency in the proposed technique changes with
the change of the load conditions.
 As can be seen, this frequency is kept higher compared
to the constant frequency in the PWM mode and smaller
compared to the switching frequency in the PFM mode
of operation.

15. Conduction Losses :
These conduction losses (inductive and capacitive losses)
dominate in the PWM technique.
Therefore,these losses are calculated for the proposed
technique and compared to those of PWM technique at
different load values.The inductive and capacitive losses
are given as


16. Waveform for Inductive Losses:

17. Waveform for Capacitive Losses:

18. Switching Losses:

19. Contd…..
Switching losses with the
Proposed technique, the
switching frequency of the
control pulse is high, Which
result in High switching losses .
In this Proposed technique the duty
cycle as well as the switching
frequency is Manipulated,which
results in lower Switching frequency
is lower switching losses.

20. Voltage Ripple:
This ripple voltage is due to the switching behavior of the
converter.
 In the feedback loop for the converters, this voltage corrupts
the input supply voltage, and hence, reduces the stability of the
system.
 Appropriate values of LC combination can be used to minimize
this ripple voltage. For a given LC combination, the ripple
voltage increases rapidly with the decrease in the duty cycle
and switching frequency.
 These ripple voltages are dominant in the PWM technique.
Therefore, the ripple voltages with the proposed technique are
calculated and compared to those of the PWM technique at
different load values.

21. Contd…

22. Waveform of Voltage Ripple:

23. Conclusion:
This paper discusses an FPGA-based technique to control
DC-DC converters. This technique dynamically
manipulates
 The duty cycle and the switching frequency of the control
Pulse.
The results indicate that the proposed technique has lower
conduction losses and ripple voltage compared to the losses
and ripple voltages inherent in the PWM technique.
Furthermore, it also significantly reduces the switching
losses compared to those of the PFM technique. Thus, a
converter based on the proposed technique results in higher
efficiency under a wide range of load conditions.