17-04-2013, 03:38 PM
HIGH EFFICIENCY ZCS BUCK CONVERTER FOR RECHARGABLE BATTERIES
BATTERIES.pptx (Size: 98.19 KB / Downloads: 28)
INTRODUCTION
Rechargeable batteries are extensively utilized in many applications. Since these appliances continuously consume electric energy, they need charging circuits for rechargeable batteries.
Modern battery chargers require Pulse width-modulated dc–dc converters for battery charger, employing semiconductor power switches.
To eradicate these problems, soft-switching and various charger topologies more suitable for battery energy storage systems have been presented and investigated. Zero-voltage-switching (ZVS) and zero current switching (ZCS) techniques are two conventionally employed soft-switching methods.
BUCK CONVERTER
Definition: A buck converter is a step-down DC to DC converter. Its design is similar to the step-up boost converter, and like the boost converter it is a switched-mode power supply that uses two switches capacitors and inductors.
SWITCHING TECHNIQUES
Hard switching :
When the switch state is changed from on to off (turn-off) or from off to on (turn-on), the transition will take a finite time in the non-ideal case.
Soft switching :
Soft switching converters constrain the switching of power devices to time intervals when the voltage across the device, or the current through it is nearly zero.
ZVS:
This technique eliminates capacitive turn-on losses.
Decreases the turn-off switching losses by slowing down the voltage rise, thereby lowering the overlap between the switch voltage and the switch current.
A large external resonant capacitor is needed to lower the turn-off switching loss.
ZCS:
Eliminates the voltage and current overlap by forcing the switch current to zero before the switch voltage rises.
For high efficiency power conversion, the ZCS topologies are most frequently adopted.
ADVANTAGES:
ZCS technology for use in the charging test of a lead-acid battery, to demonstrate the effectiveness of the developed methodology.
These techniques lead to either zero voltage or zero current during switching transition, significantly decreasing the switching losses. This increases the reliability for the battery chargers high quality, small size, light.
The circuit structure is simpler and much cheaper.
CONCLUSION
ZCS buck converter is an efficient step down DC-DC converter used in numerous electronics devices.