Compact Fluorescent Lamps Case Study

ABSTRACT

This note describes how high frequency electronic ballast is able to drive the 15W compact fluorescent lamp at a voltage sequence of 220V-240V with the operating frequency of 50Hz.

1. INTRODUCTION

The recent compact fluorescent lamps open up a whole new market for fluorescent sources. With a continuous growth rate of 20% per year, electronic ballast is widely spread over the world. Eventhough the light out of a fluorescent tube has a discontinuous spectrum, the higher efficiency brought by the electronic control of these lamps make them the best choice to save the energy absorbed by the lighting systems. The average life of CFL is 7-10,000 hours. This technical note describes how electronic ballast is designed to drive a CFL.

The Main purpose of the electronic ballast in CFL is to generate the light out of low pressure fluorescent lamp by performing the following main functions.

1. Provide a start-up voltage across the end electrodes of the lamp.

2. Maintain a constant current when the lamp is operating in steady state.

3. Assure that the circuit will remain stable, even under the fault conditions and improving lamp life.

4. Reduced ballast loss with higher efficiency

5. Facility on lamp power control

6. More efficient tube ignition

7. Flicker free operation

2. CIRCUIT DESCRIPTION

The CFL circuit shown in fig 1.0 consists of three basic blocks namely Input unit which is having a full bridge rectifier (D2, D3, D4 & D5) and Filter circuits (C4), Base drive unit which is having 2 half bridge inverters (T1, T2, Resonance Circuits) and Lamp which is actually the load for the electronic ballast. The detailed sketch of the ballast circuit is shown in the fig 1.1.

Fig 1.0 Basic Block Diagram of CFL

2.1 INPUT UNIT