CFL Lighting's "Green" Design Strategy

As more and more regions launch action to eliminate traditional incandescent lamps, our attention has also turned to the ever-changing lighting field. The latest lighting replacement products in this field are said to provide lower energy consumption, better durability and longer service life, which can bring better lighting solutions for the new century; at the same time, the reduction of energy consumption can also save energy. Consumer spending is very attractive.

Two products that have begun to gain popularity in the mass market are compact fluorescent lamps (CFLs) and LED lamps. Both of these can provide the above advantages, but this article will focus on the CFL technology. We want to analyze a non-dimmable CFL luminaire produced by the Chinese manufacturer Baishi.

The spiral tube CFL was first introduced in 1976 by Edward E. Hammer, the father of modern fluorescent technology. Although this design has greatly improved compared with incandescent lamps, at the time, General Electric's boss did not adopt it. CFLs with electronic ballasts were introduced by Osram in 1985, but it was not until 1995 that CFL lamps began commercial production.

To understand why a 20W CFL can produce the same brightness as a 75W incandescent lamp, it requires knowledge of every component of a CFL lamp. Like other fluorescent luminaires, this CFL uses a U-shaped glass tube. The inner wall of the tube is coated with phosphor and emits visible light when it encounters ultraviolet radiation generated by the ionized gas inside the tube.

In order to achieve a size suitable for the home market, the CFL design generally uses a smaller glass tube diameter and adopts a straight-folded or spirally curved structure. The electronic ballast used to light the lamp tube is designed with full consideration of the space constraints of the standard screw socket lamp. To achieve this design, it is necessary to use a reduced power source to create a suitable luminaire driver with a relatively small area.

Phosphor-coated U-glass tubes have their own history of development, but chemical engineering enthusiasts may be more interested in this history. From the consumer's point of view, the loss of the phosphor coating inside the lamp is a major problem. Despite this, high-quality CFL lamps can last months or even years.

Another point worth noting when looking at this special CFL luminaire is a through hole in the lamp holder housing. This through hole implies that the loss of ballast electronics associated with heat dissipation is also a factor that affects lamp life.

A typical electronic ballast contains a small circuit board that allows consumers to easily replace incandescent lamps with CFL lamps. The electronic ballast provides the initial energy boost to turn on the CFL lamp and then limits the current to the nominal operating value of the lamp used.

The ballast design uses transistors, diodes, and many capacitors and inductors. These devices first rectify the AC power and then create a follower-type resonant inverter circuit that generates a high-frequency, high-voltage power supply that is used to light CFL lamps. In this electronic ballast, one of the most important components is NXP Semiconductors' half-bridge CFL driver chip UBA2211.

The UBA2211 can drive CFL lamps up to 25W from a 110VAC or 220VAC input voltage, a feature that is necessary in any electronic ballast used in modern CFLs. However, one of the major advantages of the UBA2211 is its circuit includes over-temperature protection (OTP) and capacitive mode protection (CMP) functions. OTP and CMP can monitor voltage, current and power consumption, and ensure proper shutdown of the system under abnormal conditions. The burned part is safely handled at the end of its life. During the initial power "upgrade" phase of the CFL startup, the UBA2211 also provides Saturation Current Protection (SCP) so that the CFL can operate at the saturation current limit without damaging the power transistors in the electronic ballast.

We noticed its complicated power circuit when dismantling CFL, and also figured out why CFL can take a place in the market. Compared with the price of (relatively) short-life incandescent lamps, CFL lamps are now available to ordinary consumers. The price of the combination with the electronic drive circuit has begun to become competitive.

However, the price gap still exists - the typical incandescent lamp costs only 0.25 US dollars, while the CFL lamp price still hovering between 1 to 2 US dollars; but the real advantage of CFL comes from the potential energy savings. Although incandescent lamps cost only 25 cents, they cost as much as $7 over their life expectancy; CFL lamps cost as little as $1.50 over their lifetime. In this sense, CFL lamps are not only a "green" solution from an energy-saving perspective, but also a "green" solution from the perspective of saving consumer costs.