Comparison of three LED power supply schemes compatible with thyristor dimming

Author: Wu Guangmin

The thyristor dimming LED power supply technology is an important technical bottleneck for LED lighting to replace incandescent lamps in the future. At present, major semiconductor manufacturers and professional power supply manufacturers around the world are actively investing in research and development and launching some special IC chips to meet the LED lighting replacement. The arrival of the incandescent era.

NXP, National and IWATT semiconductor manufacturers that have pioneered the introduction of dedicated LED driver ICs for thyristor dimming have played a very good role in this technology.

NXP chip models are: SSL2101 and SSL2102;
National's chip model is: LM3445;
The chip type of IWATT is: IW3610;

It should be said that the above-mentioned manufacturers have different technical ideas, but the general principle is: simple, stable, and have certain versatility. Technically, it mainly follows the principle of keeping the thyristor dimmer on and then performing PWM conversion, and adds frequency conversion control and QR mode to achieve the purpose of exponential dimming and high efficiency for the human eye.

From a technical point of view, the ICs of these three manufacturers, LED power supplies for thyristor dimming, have their limitations, and the facts prove that: versatility is poor. For thyristor dimmers of different types and different countries, the problem of poor adaptability has not been well solved.

Judging from the general judgment, the generality of IWATT is slightly better. The dedicated chopper circuit is used for the stable conduction of the thyristor, and the chopping energy is utilized, and the efficiency is also the highest, but the circuit complexity is slightly higher; the application of NXP is the most Simple, but less efficient and versatile.

For the field of targeted applications, the above-mentioned LED driver-specific thyristor dimming power IC can have different adaptability, but can not think that it has great adaptability, which will disappoint you.


LED products enter the home lighting market, and the requirements for drives are getting higher and higher:

-cost

 drive part of the cost should be controlled below 15% of the total cost of the bulb

-Thermal efficiency

功率The power loss in the LED driver also affects the luminous efficiency and reliability of the whole lamp.

- Reliability and service life

 Comprehensive protection: over temperature protection, over current protection, short circuit, open circuit lock 单一 single failure protection in any case  as few components as possible

- Specification and safety

 electromagnetic interference  power factor and harmonic  isolation and safety

- dimming performance

 no visual flicker, wide dimming range

Direct replacement of incandescent lamps, compatible with existing dimmers:

- Front edge phase-cut dimmer, trailing edge phase-cut dimmer, intelligent dimming;
- LED lights should provide some security when the LEDs do not match properly with certain dimmers.

The traditional dimmer is used to drive the purely resistive load. When connecting the capacitive load, the dimmer may not work properly.

- need to provide a resistive or resistive load to operate the dimmer;
-The traditional dimmer power is relatively large, 200W-600W.

 dimming performance

- Wide dimming range: 1%~100%;
- No strobe, soft dimming curve.

High reliability

- lower AC peak current; safe operation of the thyristor
- High efficiency, low ripple current.