Exclara: Small, low-cost, long-life drive circuit for LED lighting
LED lighting is receiving increasing attention due to its reduced power consumption. With the reduction in the price of white LEDs and the mass production effect of peripheral components, the price of LED lighting fixtures will fall. For example, LED bulbs that used to be close to 10,000 yen can now be purchased at a minimum of 1,000 yen. The price reduction has accelerated the popularity of LED lighting, and the popularization has accelerated the price reduction of LED lighting equipment, and the market is developing in this direction.
What needs to be done to reduce the price of LED lighting fixtures? For LED bulbs, it is inevitable to reduce the cost of white LEDs, which account for about 40% of the manufacturing cost. At the same time, it is also necessary to reduce the cost of peripheral components such as the drive circuit and the casing. American company Exclara is engaged in driving IC business that can reduce the cost of drive circuits. If the company uses the driver IC "EXC100" that becomes HVX technology, the cost of the drive circuit can be reduced to nearly 1/3.
What is the difference between an LED lighting driver circuit using HVX and a normal driver circuit?
Dodani: The drive circuit of HVX is characterized by the use of an AC power source rectified by a rectifier circuit to illuminate the LED. Due to the higher voltage, it can be used to drive LED strings in series. This is different from the ordinary drive circuit that uses AC/DC conversion with a switching circuit and then illuminates the LED with DC power. Compared with the LED bulb, the dimming bulb can be supported by a common driving circuit, and the number of components is 40 to 50, and the driving circuit using the HVX only needs about 12. There is no need for large components such as transformers and electrolytic capacitors, and there is no switching circuit, so there is no need to take EMI countermeasures. The component cost of the drive circuit can be reduced to nearly 1/3 of the original. For lighting fixture manufacturers, not only can the component cost of the drive circuit be reduced, but also the size of the drive circuit can be greatly reduced. Therefore, it is also a great charm to improve the design freedom of the LED lighting fixture.
In addition, it is also a major feature to improve the long-term reliability of the drive circuit. The life of an LED lighting fixture is around the electrolytic capacitor of the drive circuit. The use of HVX eliminates the need for electrolytic capacitors, thus extending the life of the drive circuit. The heat resistance of the drive circuit can also be improved without using an electrolytic capacitor. It is also possible to mount an HVX driver IC on the same printed substrate as the LED.
The HVX driver IC, the EXC100, supports AC 220V and 110V inputs, as well as 50Hz and 60Hz AC frequencies. In addition, the driver circuit can be formed by using a small number of peripheral components. For the lighting fixture manufacturer, the EXC100 can be used to easily change the supply location and performance parameters of the lighting fixture, and the design period can be shortened.
The performance of the drive circuit is also high. The power conversion efficiency is 93% and the power factor is as high as 0.98. A 20:1 dimming is possible. It is equipped with a temperature sensor that cuts off the circuit at high temperatures.
——When the LED is directly driven by the AC power rectified by the rectifier circuit, its brightness will change with the frequency of the AC power.
Dodani: Indeed, there is a non-lighting time when using 50 Hz AC every 100 Hz, 60 Hz every 120 Hz. Since the lighting time is about 46%, about half of the time is a non-lighting time. However, we have introduced HVX to many customers. Although there are concerns about non-lighting time, there are more opinions about not lighting time.
It also depends on the use of lighting fixtures. If it is outdoor lighting, non-lighting time is not necessarily a problem. The non-lighting time is in the millisecond level and is hard to find with the naked eye, so even for indoor lighting, there are not a few customers who think there is no problem. When I introduced HVX in China and Japan recently, I received the attention of most manufacturers.
- Can't you shorten the non-lighting time?
Dodani: We have prepared a solution to shorten the HVX non-lighting time. That is, a small capacitor is used in combination. For example, a drive circuit with an input power of 10W can extend the lighting time from 46% to 68% by adding a 20μF capacitor. Although the power conversion efficiency will drop by about 7 percentage points, the non-lighting time can be greatly shortened.
If the LED lighting time is extended by adding a capacitor, the brightness of the LED lighting fixture can be maintained even if the power peak of the input LED is lowered. By reducing the peak power of the input LED, the degradation of the LED can be suppressed.
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