Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

Change the variable resistor-divider ratio can change the conduction angle, so as to achieve the purpose of changing its RMS.Usually this potentiometer with a switch,connected to the input of n for light switch.In addition, In addition to SCR,there are trailing edge dimming technology transistors, etc,Because their basic problem is the same，Is not described in this.

1 The SCR dimmer shortcomings and problems

However,There are a series of problems in silicon-controlled dimmer.

(1).The SCR destroyed sine wave, which reduces the power factor value,PF is usually less than 0.5,the smaller the conduction angles the worse power factor
(1/4 brightness is only 0.25).
(2).Similarly,non-sinusoidal waveform increased harmonic coeffcient.
(3). Non-sinusoidal waveform on the line will have a serious interference signal.(EMI）
(4). It is easily unstable at low load ,therefore a discharge resistance must be added. And the resistance of the discharge at least 1-2 watts of power consumption.
(5).In the general,SCR dimmer circuit output to LED drive power supply will be unexpected problems arising. That's input terminal of the LC filter will make SCR produce oscillations.This oscillation does not matter for the incandescent, Because the thertia of incandescent lamps makes the human eye can't see out the oscillations. But for LED driver power can produce audio noise and flicker.

2 SCR dimmer advantage

Although SCR dimmer there are so many shortcomings and problems, But, it has certain  advantages ,That is, it has formde an alliance and incandescent lamp halogen lamp, occupies a larger dimmer market. If the LED light to replace the SCR location of incandescent and halogen lamps, it also to have and the SCR dimmer compatible.

Specifically, In some place ,there have installed the SCR dimmer of incandescent lamp or halogen lamp, the wall has been installed SCR dimmer and knobs, the Wolves in the Walls has also installed two root to lamps and lanterns connections. To replace the wall SCR switche and to increase the number of cable is not so easy. The easiest way is to do all the same, as long as the lamp holder of incandescent lamp unscrew and replace with compatible function of SCR dimmer LED lamp can. Such a strategy as LED fluorescent lamp, make best as the T10, T8 and now is exactly the same as fluorescent light size, do not need professional electrician, ordinary people can directly replace, it can quickly popularity. Therefore , many foreign countries and production LED drive IC manufacturers are developed can be compatible with the existing SCR dimmer IC.

3 Compatible with adjustable optical-intensity LED drive silicon IC

There are currently on the market NXP SSL2101 / 2,National Semiconductor's LM3445, iWatt the iW3610 and OnSemi the NCL3000 of four SCR dimmer compatible driver IC. Its characteristics are as follows:

 
And general anti-shock type of IC difference is that they can detect the SCR conduction angle in order to define LED electricity to adjust the light. We are not prepare to detail introduction their principle and performance, because we don't think this is the direction of LED light.

4 SCR dimmer compatible with the problems and shortcomings
Although many multinational big chip companies have introduced a compatible with existing SCR dimmer chip and solutions. But this kind of solution is not recommended, the main reason as follows:
(1) SCR technology is old technology with over half a century, it has many of the shortcomings mentioned above, is a long overdue elimination technology. It should be and incandescent lamp, halogen lamps at the same time from the historical stage.
(2). Many of these chips claiming to have a PFC, can improve the power factor. In fact, it only improves as the SCR load power factor, so that they appear close to the pure resistance of the incandescent and halogen lamps, and didn't improve including SCR of the whole system, the power factor.
(3). All compatible LED SCR dimmer the overall efficiency of the system are very low, and some do not consider the work needed to stabilize the loss of discharge resistance,
completely damaged the energy-efficient LED.
(4). All of the SCR LED adjustable optical-intensity system are also the positive current adjust LED, there are mentioned chromatographic offset shortcomings.
(5). Install SCR dimmer of incandescent and halogen lamps for less than one ten thousandth share, while the proportion of the wall installation of silicon-controlled switch  in the SCR dimmer lamps and lanterns not even one ten thousandth. Because the vast majority of SCR dimmer installation is lamps,  bedside lamps, floor lamp.Moreover,the market there are dozens of different specifications of SCR and transistor dimmer switches. In fact impossible developed IC is compatible with all the thyristor switch,, but only a small part of them compatible.
(6). LED is a kind of brand-new genesis technology, it has incomparable advantage. No necessary to take care of the sacrifice LED behind the advantages of silicon controlled. The more should not go to the new switch  installed on the wall of the silicon-controlled to achieve the LED dimmer.