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Analysis on the Shooting Effect of Dual-latch and PWM

时间:2017-08-25 浏览量:

With the popularity of smart phones and cameras, a number of customers complain  that the LED display photo picture using the dual-latch driving IC  is not good. Chipone's cost-effective PWM driving IC series products,  ICN205X, can solve the weakness of dual-latches IC display products. It makes the display photo picture perfect.

What are the differences between dual-latch and PWM? How can PWM IC highly improve shooting effect? The followings are observed by a set of tests.

We selected the test platform with one of the most popular rental P4.81 indoor-outdoor GM  products. We will see the display photo picture differences between LED display modules using an industry mainstram dual-latch IC and ICN205X. In order to ensure fairness and objectivity of the test, we put two modules under the same condition with same brightness and color temperature . We will see the photograph performances at each camrea shutter speed.  In addition,all images were picked from the original image without any processing.

Application Scenarios

Brightness Range

Camera shutter range

Indoor Studio


1/100-1/300 S

Outdoor Studio


1/400-1/600 S

Semi-outdoor stage


1/800-1/1500 S

Outdoor sports,advertising


1/2000 S

Portrait Comparison

Figure1: Shutter in 1/200,Left:dual-latch IC, Right: ICN205X

Figure2: Shutter in 1/500,Left:dual-latch IC, Right: ICN205X

Figure3: Shutter in 1/1000,Left:dual-latch IC, Right: ICN205X

Figure4: Shutter in 1/2000,Left: dual-latch IC, Right:ICN205X

Dark Picture Comparison

Figure5: Shutter in 1/200,Left:dual-latch IC, Right: ICN205X

Figure6: Shutter in 1/500,Left:dual-latch IC, Right: ICN205X

Figure7: Shutter in 1/1000,Left: duall-atch IC, Right: ICN205X

Figure8: Shutter in 1/2000,Left: duall-atch IC, Right: ICN205X

We listed the following conclusions through the above test photos.GM Dual-latches products may reach 1920 or higher refresh rate, but the photographing effect began to deteriorate in 1/200 shutter. If more than 1/500, it completely unable to watch.

Some of photos by dual-latch was no scan line showed up,indicating that refresh rate is enough,but it still has serious display distortion(as shown in figure 2,figure 6).

The image could be accepted when camera shutter in 1/2000 with PWM IC

Comparison at gray-scale

The PWM photo effect is much better than the dual-latches. PWM IC is also significantly after brightness reduce at gray-scale.

Figure 9:Brightness reduced to 50% ,left: dual-latch IC, right:ICN205X

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

· Driving more LEDs but no loss of performance.
· Low data clock speed, helping  improve EMI

· Eliminating open-led Cross-line.

· Wide range of current gain adjustment

LED display into the full color era has been more than 20 years. Driver IC plays a decisive role, which has gone two technical stages, namely, Common constant current and PWM constant current stage. PWM constant current driving IC has been keeping high-cost due to its huge display superiority. In order to satisfy the customer’s demand with increasing the refresh rate and reducing  the high-cost, the dual-latch products were innovated, and quickly became the main force in the end. Users thought that they’ve got better pictures effect when they look at the doubled refresh rate figures. In fact,  it does not work out !

Now all this will be completely subversive by ICN205X. It will lead the LED industry into the PWM era.

We believe that in the coming future,dual-latch products will only exist in the low-end market, PWM will become the starting point for performance. Let's embrace the new era of LED display !