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Analysis on Photo Effect of Double Latching and PWM LED Driver IC

May. 22, 2019

With the popularity of smart phones and the increasingly powerful camera functions, more and more customers have reported that the picturesof screen with dual-latch ICs is very poor. ICN25X of PWM IC from CHIPONE can solve the bad photo pain point of double latching products, to get a perfect photo of screen. So compared with double latching IC, which effect has been improved by ICN205X, let's  find out from the result of a test.

The test based on the popular items P4.81 (indoor &outdoor),which are separately with double-latching and ICN205X. To ensure the fairness and objectivity of the test, we first adjust the brightness and color temperature to exactly the same, and compare the photos at different shutter speeds. In addition, it should be noted that all the pictures in this article are original drawings and have not been processed.

ApplicationBrightness RangeCamera shutter range
Indoor Studio500-800cd1/1000-1/300 S
Indoor Stage800-1200cd1/400-1/600 S
Semi-outdoor Stage3000-4000cd1/800-1/1500 S
Outdoor sports, advertising6000-8000cd< 1/2000 S

---------------------------------- Portrait comparison -----------------------

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 1: 1/200 Shutter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 2: 1/200 Sh5utter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 3: 1/1000 Shutter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 4: 1/2000 Shutter, left screen with double-latching IC, right screen with ICN 205X.


------- Dark theme Picture Comparison------

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 5: 1/200 Shutter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 6: 1/500 Shutter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 7: 1/1000 Shutter, left screen with double-latching IC, right screen with ICN 205X.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 8: 1/2000 Shutter, left screen with double-latching IC, right screen with ICN 205X.

From the above test photos, the following conclusions can be drawn:

Although the double-latch product can achieve a refresh rate of 1920 or even higher, the photo effect begins to deteriorate at the 1/200 shutter speed, and over 1/500 is completely unviewable. The double-latch product does not show scan lines in some photos, indicating that the refresh rate is sufficient, but serious display distortion still occurs.(Figure 2&6)

While with PWM IC , figure quality is still acceptable at 1/2000 shutter speed.


------ Grayscale performance comparison ----

Not only the figure quality is far better than double-latch's, PWM ICs also has significantly better gray scale performance after brightness reduction.

Analysis on Photo Effect of Double Latching and PWM LED Driver IC

Figure 9: brightness reduce to 50%, left screen with double-latching IC, right screen with ICN 205X.


In addition to the above comparisons, the PWM IC also has the following advantages

Large load capability without loss of performance

Low data clock facilitates, better for EMI improvement

Can eliminate open circuit cross

Achieve a wide range of current gain adjustments

The LED display has entered the full-color era more than 20 years,the driver IC, which plays a decisive role in the display effect, has undergone two technical phases, universal constant current and PWM constant current phase. PWM constant current IC has a huge display effect, so its price is always high.  In order to meet the customer's need to increase the refresh rate without bearing the huge cost pressure, double-latch products came into being and quickly became the main force. Users saw double the refresh rate on the software interface and thought that they had better photographic effects. In fact, this was not achieved.  Now all this will be completely subverted by the ICN205X, it will lead the industry into the PWM era. 

It is believed that in the near future, dual-latch products will only exist in the lowest-end market, and PWM will become the starting point of high performance.  Let us embrace the advent of a new era of LED display.