Silan announces primary-side control LED driver SD6857/8 series with SCR dimming and PFC

Date Announced: 12 Nov 2011

Silan continuously unveiled new products in green LED illumination field—the primary side control LED driver SD6857/8 series with SCR dimming and PFC. This series circuits using PFM technology provide accurate constant current (CC) control loop with high stability and average efficiency, which make them widely used in AC input LED illumination such as PAR light, bulb light and fluorescent light, etc.

The difference between SD6857 and SD6858 is that SD6858 supports SCR dimming. The SD6858 system solution supports several different types of dimmers and there is no blinking during the dimming process.

These series devices control the system output current indirectly and realize the constant output current by detecting the primary side current of the transformer. They use numerous Silan’s patented technologies---PFC+PSR+TRIAC control technologies, which use the primary side control mode to control the LED constant current driving and realize the SCR dimming, output same current under different voltage input, primary side control and high power factor.

The major highlight of SD6857/8 series LED drivers is in the high power factor (PF>0.95). The power factor is the phase difference Cos@ of voltage and current added to the load. In general, the power factor is 0 <= Cos@ <= 1, and 1 is the ideal situation. The high power factor (PF) is to be considered as the challenge of LED illumination design following the energy-saving development. These circuits feature high PF value more than 0.95, which can avoid power supply efficiency reduction and excessive high-order harmonics (too many harmonics will be fed back to the electricity supply grid and have an effect on it) caused by low PF.

SD6857/8 using primary side control mode reduces total component count, such as opto-coupler, secondary feedback control, loop compensation and at the same time decreases the power dispassion and the total cost. It is well suited for cost effective designs with smaller design size.

In addition, this device integrates lots of protection circuits such as temperature protection, open loop protection, peak current compensation, current limit, overvoltage protection, undervoltage lockout, etc to ensure the normal working environment and prolong its life.

SD6857/8 series circuits are based on the BiCMOS/BCD process developed by Silan. They are available in SOP-8 package with the advantages of high integration, small PCB area, and convenient debugging, etc.

Should you have any questions, please, visit NEON-EK Ltd. at official distributor of Silan Microelectronics in Bulgaria and Russia or send e-mail to

9000 Bulgaria, Varna, Batak st. 7, the second floor, offices 9 and 10 +359(52) 606-113 +359(52) 606-881


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