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Black Tech | LTECH T-PWM Super Depth Dimming Technology

Dec 14, 2018

Two years ago, LTECH created LED 0.01% depth flicker-free dimming (high frequency exemption level), which is still unsurpassed nowadays!

Two years later, with deeper exploration, revolutionary T-PWM Super depth dimming technology will continue to lead LED industry in the next decade!

Small Knowledge Sharing:

Before understanding what’s the T-PWM super depth dimming technology, we will take you to review some existing dimming drive modes in the market closely related to it.

In LED commercial lighting, the key words we hear most often, such as: DMX, DALI, 0/1-10V, Triac, WIFI, bluetooth, RF, Zigbee.... Many people think it is the standard  of deciding the  dimming in good or not. But they are the input signal of dimmable driver. choose different input signals is mainly because of the environment (installation, wiring), function, cost, the late development of flexibility, has nothing to do with judging the dimming quality, the quality of dimming effect is mainly decided by the drivers output dimming way.

What is a good dimmable driver?  in addition to meeting the requirements of conventional parameters, also include following five points:

1.Dimming does not affect the light index;

2.Wide dimming range, dimming depth is less than 1%, can meet the requirements of more scene applications;

3.When viewing with human eyes, without any invisible flicker on the light in static states or adjustable process. Dimming is uniform and delicate;

4.There is no ripple or flicker when shooting works with cameras and other photographic equipment;

5.Meet the standard requirement in the testing of professional stroboscope and has no impact on human health.

CCR (Analog) dimming

It is output dimming curve graph of some brand’s 0-10V led driver adopting CCR (analog) (about 8% output current, LED goes out directly)

Analog dimming/ CCR (Constant Current Reduction) dimming refers to the linear adjustment of LED brightness by changing the current passing through LED. Ideally, the brightness of LED is proportional to the passing current.

This dimming principle has following characteristics when dimming LED:

【Advantages】

1.Without low noise in dimming. In the use of digital camera equipment photography, not easy to produce ripple and flicker.

【Shortages】

1.It will cause color shift of the LED when current changes.

2.Narrow dimming range, poor dimming consistency and linearity at multiple drivers.

3.LED is not working with rated voltage and current and the LED life would be shorten in long-term working.

4.The LED driver conversion efficiency would rapidly reduce with the reduction of current, thus increasing the power loss of the power system.

Real shooting of a CCR (analog) dimming power supply

CCR(Analog)+PWM Dimming

CCR(Anolog)+PWM dimming schematic diagram( P% is PWM dimming)

CCR(Analog)+ PWM Dimming means on the basis of analog dimming adding the PWM dimming mode at low brightness, which aims to make up the insufficient dimming range of CCR, at the same time keep the advantage of non-flicker at high brightness dimming of CCR. But both advantages absorb but also defects. The practical problems are as following:

【Advantages】

1.Wider dimming range comparing to pure analog dimming, and wider application.

2.Keep the advantage of non-flicker at middle and high brightness dimming.

【Shortages】

1.The accuracy of analog dimming is not high, and the problem of poor dimming linearity has not been improved.

2.Unnatural during analog and PWM transitions.

3.PWM dimming may still exist stroboscopic problems at low brightness, and some shots may exist ripple phenomenon.

4.At Low brightness of PWM is technical difficulty. Most manufacturers have a response delay dimming after they add PWM dimming into CCR.

The actual shooting in a CCR + PWM dimmable driver

PWM Dimming

PWM dimming schematic diagram

Pulse Width Modulation(PWM), which principle is to change the on-time of forward current by the PWM wave to turn the LED on and off to achieve the brightness adjustment effect.

This mode is often compared to a high-frequency switching action, that is the LED is repeatedly at 0% and 100% brightness, so the advantages and disadvantages of PWM are obvious (such as stroboscopic problems at low brightness). The control and development of PWM technology determines the quality of PWM dimming. So commonly features of PWM dimming are also obvious:

【Advantages】

1.Extremely high dimming accuracy, no color shift during dimming process, and won’t affect LED life.

2.High-quality PWM dimming, non-flicker in a wide range of dimming.

【Shortages】

1.If the PWM program and hardware do not match well, the drive circuit would easily cause low noise during dimming.

2.If the PWM pulse frequency is very low, human eyes will feel flicker. And if the frequency is not high, even ordinary digital camera devices can capture ripples and stroboscopic phenomena.

3.If the PWM frequency is too high, although it will up to flicker-free standard, but the dimming gray level range will be reduced and have flicker at low brightness.

X brand(left) and LTECH(right) Comparation for High Frequency Exemption Level Dimming effect

Small summary

PWM is the most ideal LED dimming mode at present. However, it is a worldwide problem to improve the frequency of PWM without affecting the effect of the gray scale range.

It still needs certain technical strength to achieve excellent dimming effect. By using PWM technology and grinding it, we can overcome this problem to create a different lighting effect.At present, the minimum dimming depth of individual brands reaches 1%.

In 2016, LTECH has broken through the technical bottleneck to reach 0.1% dimming depth, and the stroboscopic index is the first domestic company to reach the high frequency exemption level.

LTECH New Breakthrough: T-PWM Super Depth Dimming Technology

In fixed brightness, the perceived brightness of human eyes is much higher than the measured brightness

Due to the difference between human eyes perception and measured brightness, when the human eyes needs dark atmosphere, the brightness must be much lower than the measured brightness. Therefore, the difficulty in the range of dimming finally stays in the low brightness region which most sensitive to human eyes.At present, PWM dimming mode drivers of all major brands has their own optimization schemes, but there are not many effective solutions to achieve wide range, high depth, and flicker free throughout.

Compared with the previous three dimming methods, the revolutionary T-PWM Super depth dimming technology of LTECH has solved all the disadvantages of above dimming methods and retained all the advantages. Besides, T-PWM dimming also has following important breakthroughs:

0-100% full range dimming, LED dimming depth < 0.01%.(Current ammeter accuracy has been unable to measure the minimum current value).

There is no visual flicker in human eyes or during shooting and viewing, which meets the highest standard of professional stroboscope and has no impact on human health.

Select a unique program algorithm and hardware matching, the human visual experience is more comfortable, low brightness and smooth.

In order to make you feel the different dimming modes more intuitively, LTECH compares the dimming driving modes of different brands:

Dimming effect of Ltech power supply

In the future, LTECH will continue to overcome technical difficulties, pursue the ultimate product experience, and present high-quality LED dimming power supply and intelligent controller to customers.


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