SDS3537's only built-in multi-channel linear IC meets IEC harmonic THD certification

What is IEC THD certification? Regarding the LED lighting industry, total harmonic distortion (THD) can be a less than a parameter indicator for players of small and medium power products. However, the players in the industry for high-power products are an indicator that cannot be ignored. The International Electrotechnical Commission (IEC) has a special certification standard for lighting: IEC 61000-3-2 Class C (GB17625.1) is also known as THD certification.

Industry linear drive harmonic distortion status

The LED linear drive IC has been developed since 2009, and the technical parameters of all aspects are close to the Switching Power Supply. In terms of high-power products, linear ICs have inherent cost advantages, but the threshold for THD certification has never been better.

Everyone knows that total harmonic distortion refers to the main component of the harmonic output signal that is more than the input signal, which is caused by the incomplete linearity of the system. Yes, it is the THD exceeding the standard caused by the incomplete linearity of the driver IC system. This is caused by the system architecture of the LED driver IC itself, and the greater the power, the more difficult it is to guarantee.

At present, there is still a Magnachip separation device solution to ensure THD on the market. That is to say, the chip is controlled by 1+1, and one of the constant current chips is used as Magnachip, but this can only ensure that the total harmonics reach 20% or less. The harmonic requirements of the IEC certification requirements cannot be guaranteed.

As shown in the above figure, another scheme is to use a four-segment linear IC to collect signals through the external interface of the dimming interface MOS to perform constant current, but the drawbacks of this scheme are very obvious, the cost is high, the parts are many, and The lamp voltage requirements are very high, and the deviation harmonics cannot guarantee the fractional harmonic requirements. The sample can not be mass produced.

Principle of THD architecture of SDS3537 scheme

To ensure that the THD is up to standard, you need to make the output signal infinitely close to the input signal. SDS3537 can be said to be the only linear IC that can achieve IEC THD certification. Let's take a closer look.

This is the SDS3537's IC pinout, ESOP8 package, pin is simple, and the key to the THD index certification is the PWM pin. Let's take a look at the physical map of the SDS3537 as a whole.

It is not difficult to see that the SDS3537 controls the output drive current of the IC by inputting a waveform signal. The peripheral circuit is simple, and the harmonics can guarantee the IEC 61000-3-2 Class C (GB17625.1) certification.

We are looking at the BOM list of the SDS3537 over IEC certification.

From the above table and the physical map, it can be seen that for the high-power IEC certification index, the SDS3537 scheme has zero components and low BOM cost.

The key point is that it can pass the IEC harmonic certification. This can be the first in the industry.

IEC 61000-3-2 Class C certification index

The figure above is the IEC 61000-3-2 2014 Class C (GB17625.1) for harmonic certification requirements for LED lighting.

Let us look at the THD harmonic report measured by the SDS3537-220V-50W lamp.

SDS3537 measured THD data report

Looking at the above figure, it can be seen that it is completely feasible for the SDS3537 to apply the VAC input signal to control the output drive current to meet the harmonic parameters. (Source: 晟Disc integration)