Analysis of double step-down two phase Buck converter

1. ANALYSIS OF DOUBLE STEP-DOWN TWO PHASE
BUCK CONVERTER
Submitted by
SAMPREETH D
SUNIL
NAVODAYA INSTITUTE OF TECHNOLOGY
RAICHUR-584103

2. ABSTRACT
 The objective of this presentation is to design DC-DC
converter for supplying power to CPU, called as voltage
regulator module (VRM).
 This converter essentially has double step-down conversion
and high efficiency.
 Connecting a capacitor to conventional two phase buck
converter divides the input source voltage into one half,
useful for balancing the inductor currents.

3. CIRCUIT DIAGRAM

4. STATE-1
Switch Sma ON

5. Accordingly the energy is stored in the
inductor La from this input voltage, and the
inductor current iLa rises linearly.
The change in the inductor current ∆iLa(ON) is
as follows,
∆iLa(ON) = (Ei - Vci – Eo)TON/La............(1)

6. STATE-2&4
Switch Sma & Smb OFF

7. Therefore the inductor current falls
linearly.
The change in the inductor current
∆iLa(OFF)=(Eo*TOFF)/La……………(2)

8. STATE-3
Switch Smb ON
SRb

9. Accordingly the energy is stored in the
inductor Lb from the capacitor Ci, and
the inductor current iLb rises linearly.
The change in the inductor current
∆iLb(ON)=(Vci-Eo)TON/La………..(3)

10. During the states I, II and IV, the main
switch Smb is OFF.
The inductor Lb is connected to the
capacitor Co
The energy stored in the inductor Lb is
supplied to the capacitor Co through
the switch SRb.

11. Therefore the inductor current falls linearly.
 The change in the inductor current is
∆iLb(OFF)=(Eo*TOFF)/Lb……………….(4)
The inductor current iLb of the lower side
with triangle waveforms is repeated with
180 degree phase shifts with iLa.

12.  In the steady-state, the equations (1) and (2) are equal
(Ei- Vci- Eo)ToN - EoToFF =0.............. (5)
 Similarly, from the equations (3) and (4)
(Vci - Eo)TON - EoToFF = 0.............. ..(6)
 From (5) and (6), the capacitor voltage Vci is as
Vci=Ei/2………………………………………..(7)

13. From (5) and (7)
Eo/Ei=1/2*(TON/(TON+TOFF))
i.e
Eo/Ei=D/2…………………..(8)

14. CIRCUIT WAVEFORMS

15. ADVANTAGES
 Doubling of step-down conversion(Eo/Ei=D/2).
 Reducing switching loss.
 Reducing of voltage stress of switching element.
 Automatically balancing of inductor currents.

16. REFERENCES
 [1] Intel Corp. "Voltage Regulator Module (VRM) and Enterprise
Voltage Regulator-Down (EVRD) 10.0".
 [2] David W. Parsley, "Dual-Inductor Buck Switching Converter,
"US patent 4,713,742, Dec. 1987.
 [3] H.C. Martin, "Power Supply Technology for Low Voltage Low
Ripple Requirements," US patent 4,618,919, Oct. 1986.
 [4] David W. Parsley, Hubert C. Martin, Jr., Switching Capacitor
Interleaved Forward Power Converter, US patent 5,008,795, Apr.
16, 1991.
 [5] D. W. Borst, E.J. Diebold, F.W. Parrish "Voltage Control by
means of Power Thyristors," IEEE Trans. on Industry and General
Applications, Vol. IGA-2, No. 2, pp. 102-103, Mar./Apr. 1966.

17. Thank
you