Download a novel transformer-less interleaved four-phase step

A NOVEL TRANSFORMER-LESS INTERLEAVED FOUR-PHASE STEP-DOWN DC
CONVERTER WITH LOW SWITCH VOLTAGE STRESS AND AUTOMATIC
UNIFORM CURRENT SHARING CHARACTERISTICS
ABSTRACT:
In this paper, we propose a novel transformer-less direct current (dc) converter that features low
switch voltage stress and automatic uniform current sharing. An interleaved four-phase voltage
divider operating from a 400V DC bus is used to achieve a high step-down conversion ratio with
a moderate duty ratio. Based on the capacitive voltage division, the proposed converter achieves
two major objectives, i.e., increased voltage conversion ratio, due to energy storage in the
blocking capacitors, and reduced voltage stress of active switches and diodes. As a result, the
proposed converter permits the use of lower voltage rating MOSFETs to reduce both switching
and conduction losses, thereby improving the overall efficiency. In addition, due to the charge
balance of the capacitors, the proposed converter enables automatic uniform current sharing of
the interleaved phases without adding extra circuitry or complex control methods. The operation
principles and performance analyses of the proposed converter are presented, and its
effectiveness is verified by a 500W output power prototype circuit that converts 400V input
voltage into 24V output voltage
INTRODUCTION:
In this paper, we propose a novel transformer-less direct current (dc) converter that features low
switch voltage stress and automatic uniform current sharing. An interleaved four-phase voltage
divider operating from a 400V DC bus is used to achieve a high step-down conversion ratio with
a moderate duty ratio.
Based on the capacitive voltage division, the proposed converter achieves two major objectives,
i.e., increased voltage conversion ratio, due to energy storage in the blocking capacitors, and
reduced voltage stress of active switches and diodes.
As a result, the proposed converter permits the use of lower voltage rating MOSFETs to reduce
both switching and conduction losses, thereby improving the overall efficiency.
In addition, due to the charge balance of the capacitors, the proposed converter enables automatic
uniform current sharing of the interleaved phases without adding extra circuitry or complex
control methods
Quadratic buck converters were built with cascaded dc-dc buck converters which achieve a high
voltage conversion ratio. These converters can be transformed into fewer switch topologies to
achieve improved characteristics, such as size, and simplified driver design. It can be operated
over a wider range of the step-down conversion ratio without using an extremely low duty ratio.
However, it requires an additional power stage that reduces the efficiency.
A three-level buck converter was proposed to lower the switch voltage stress to half of the input
voltage. By using metal-oxide-semiconductor field-effect transistors (MOSFETs), improved
efficiency and enhanced performance are achieved as compared to the conventional buck
converters whose switches must be rated for the full dc bus voltage.
On the other hand, an IBC uses a high number of components. An IBC with a single-capacitor
turnoff snubber was introduced which reduces the switching loss associated with turn-off
transition. In this design, a single coupled inductor implements the converter with two output
inductors.
However, it can only be operated at the discontinuous conduction mode (DCM) and, as such, all
elements suffer from a high current stress, resulting in high conduction and core losses.
Moreover, the input voltage still applies across all semiconductor devices. To reduce switching
losses, an active-clamp IBC was proposed In this converter, all active switches are turned on
with zero-voltage switching (ZVS).
EXISTING SYSTEM:
In the conventional multi-phase IBC, active switches are required to use high-voltage devices
that are rated above the input voltage. High-voltage-rated devices generally render a number of
undesirable characteristics, such as high cost, large on-resistance, large voltage drop, and severe
reverse recovery.
For high-input low-output voltage regulation applications, operations at higher switching
frequencies are required to achieve a higher power density and better dynamics. However, the
buck converter with a high step-down conversion rate yields a significant switching loss due to
its extremely low duty cycle.
This fact not only limits the achievable switching frequency, but also complicates its
implementation. In addition, the efficiency is further compromised due to the short on-time and
long freewheeling time within each switching cycle.
PROPOSED SYSTEM:
In this paper, we propose a novel transformer-less dc converter that features low switch voltage
stress and automatic uniform current sharing. An interleaved four-phase voltage divider is used
to achieve a high step-down conversion ratio.
In the proposed converter, series charging of the two capacitors from the input voltage and
parallel discharging to the load facilitated by a new four-phase IBC. This architecture provides a
high step-down conversion ratio and a low output current ripple without requiring an extremely
low duty cycle.
Moreover, due to the charge balance of the capacitors, the converter features automatic uniform
current sharing of the interleaved phases without adding extra circuitry or complex control
methods.
ADVANTAGES:

Increased voltage conversion ratio, due to energy storage in the blocking capacitors.

Reduced voltage stress of active switches.

Reduce both switching and conduction losses, thereby improving the overall efficiency
BLOCK DIAGRAM:
TOOLS AND SOFTWARE USED:

MPLAB – microcontroller programming.

ORCAD – circuit layout.

MATLAB/Simulink – Simulation
APPLICATIONS:

Voltage regulator modules (VRMs) for computer central processing unit (CPU) boards.

Battery chargers.

Distributed power systems
CONCLUSION:
In this paper, we have proposed a novel transformer-less dc converter that offers a high stepdown conversion ratio, low switch voltage stress, and automatic uniform current sharing. The
proposed converter topology yields a low switch voltage stress and, thereby, enables the use of
low voltage rating MOSFETs to reduce both switching and conduction losses. It achieves an
improved overall efficiency and features automatic uniform current sharing. The operation
principle and steady-state analyses of the voltage gain were provided, and the effectiveness and
superiority of the proposed converter were verified by experimental studies sing a prototype
circuit.
REFERENCES:
[1] D. D.-C. Lu and V. G. Agelidis, “Photovoltaic-battery-powered DC bus system for common
portable electronic devices,” IEEE Transactions on Power Electronics, vol. 24, no. 3, pp. 849855, March. 2009.
[2] Kai Sun, Li Zhang, Yan Xing, and Guerrero, J.M., “A distributed control strategy based on
DC bus signaling for modular photovoltaic generation systems with battery energy storage,”
IEEE Transactions on Industrial Electronics, vol. 26, no. 10, pp. 3032-3045, Oct. 2010.
[3] M. Pahlevaninezhad, J. Drobnik, P.K. Jain, and A. Bakhshai, “A load adaptive control
approach for a zero-voltage-switching DC/DC converter used for electric vehicles,” IEEE
Transactions on Industrial Electronics, vol. 59, no. 2, pp. 920-933, Feb. 20112.