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IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 53, NO. 1, FEBRUARY 2006
Novel Zero-Voltage-Transition PWM
DC–DC Converters
Chien-Ming Wang, Member, IEEE
Abstract—A new family of zero-voltage-switching (ZVS) pulsewidth-modulated (PWM) converters that uses a new ZVS-PWM
switch cell is presented in this paper. Except for the auxiliary switch, all active and passive semiconductor devices in the
ZVS-PWM converters operate at ZVS turn ON and turn OFF.
The auxiliary switch operates at zero-current-switching (ZCS)
turns ON and OFF. Besides operating at constant frequency, these
new converters have no overvoltage across the switches and no
additional current stress on the main switch in comparison to
the hard-switching converter counterpart. Auxiliary components
rated at very small current are used. The principle of operation, theoretical analysis, and experimental results of the new
ZVS-PWM boost converter, rated 1 kW, and operating at 80 kHz,
are provided in this paper to verify the performance of this new
family of converters.
Index Terms—DC–DC converter, zero-voltage-switching (ZVS).
I. I NTRODUCTION
Fig. 1.
P
ULSEWIDTH-MODULATED (PWM) dc–dc converters
have been widely used in industry due to their high-power
density, fast transient response, and ease of control. The aim
of higher power density and faster transient response can be
achieved easily by increasing switching frequency. However,
increasing switching frequency will result in more switching
losses and electromagnetic interference (EMI). In recent years,
a number of zero-voltage-switching (ZVS) and zero-currentswitching (ZCS) PWM converters are proposed by adding
resonant active snubbers to conventional PWM converter to
combine the desirable features of both resonant and normal
PWM techniques [1]–[12]. In these converters, the turn ON
and/or OFF process takes place under ZVS and/or ZCS during
very short periods of time; the converter acts as a normal PWM
converter during most of the time. Switching losses and EMI
noises are reduced. However, these auxiliary components still
generate substantial switching losses and EMI noise, because
the auxiliary semiconductor devices are turned ON and OFF at
hard switching in some active snubbers. A series of ZVS-PWM
converters is proposed to overcome this problem, but additional
voltage and/or current stresses on the main switch and the
main diode occurred in these converters. This paper proposes
a novel ZVS-PWM switch cell that improves the drawbacks of
the previously proposed ZVS-PWM converters. In the proposed
Manuscript received March 8, 2004; revised August 10, 2005. Abstract
published on the Internet November 25, 2005. This work was supported by
the National Science Council, Taiwan, R.O.C., under Project NSC94-2213E-197-005.
The author is with the Department of Electrical Engineering, National Ilan
University, I-Lan 260, Taiwan, R.O.C. (e-mail: jimiwang@ms6.hinet.net).
Digital Object Identifier 10.1109/TIE.2005.862253
Proposed ZVS-PWM switch cell.
cell, except for the auxiliary switch, all active and passive
semiconductor devices in the ZVS-PWM converter turned-ON
and OFF with ZVS. The auxiliary switch operates at ZCS
turn ON and OFF. A new family of dc-to-dc PWM converters
based on the proposed ZVS-PWM switch cell is proposed.
Besides operating at constant frequency, the new family of
ZVS-PWM converters has no additional voltage and current
stress on the main switches compared with the corresponding
hard-switching converters. Among the new family of dc-to-dc
PWM converters, a boost converter was taken as an example
and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the
1-kW prototype converter operating at 80 kHz.
II. P ROPOSED ZVS-PWM S WITCHING C ELL
The new proposed ZVS-PWM switching cell is shown in
Fig. 1. It is formed by two switches Mm and Ma , four diodes
D1 , D2 , D3 , and D4 , two resonant inductors Lr1 and Lr2 , and
two resonant capacitors Cr1 and Cr2 . Mm is the main switch,
which is responsible for the power transferred to the load, while
Ma is an auxiliary switch that handles a small fraction of the
total output power and is rated at a small average current to provide conditions for soft commutation under constant frequency
to the main switch. In the case of boost-type converters, it does
not require a floating driver for the auxiliary switch, since the
two switches have a common ground. The proposed ZVS-PWM
auxiliary circuit can be applied to various kinds of converters.
Fig. 2 shows the new family of ZVS-PWM converters derived
using the proposed ZVS-PWM switching cell.
0278-0046/$20.00 © 2006 IEEE
WANG: NOVEL ZERO-VOLTAGE-TRANSITION PWM DC–DC CONVERTERS
Fig. 2.
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Six basic topologies of the new ZVS-PWM converters. (a) Buck. (b) Boost. (c) Buck–boost. (d) Cuk. (e) Sepic. (f) Zeta.
III. O PERATION P RINCIPLE
It should be noted that the principle operation and features
of these new converters are the same as those of the new
ZVS-PWM boost converter. A new ZVS-PWM boost converter,
shown in Fig. 2(b), will be taken as an example and be analyzed
in this paper. To simplify the analysis, it is assumed that
the converter is operating in steady state and the following
assumptions are made during one switching cycle.
1) All components and devices are ideal.
2) The input filter inductance Lin is large enough to assume
that the input current Iin is constant and is much greater
than resonant inductors Lr1 and Lr2 .
3) The output capacitor Co is large enough to assume that
the output voltage Vo is constant and ripple free.
4) Input voltage Vin is constant.
5) The voltages of the resonant capacitors Cr1 and Cr2
are equal to 0 and the resonant currents of the resonant
inductors Lr1 and Lr2 are equal to 0 before the main
switch turns ON.