Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

An off line LED driver topology with TRIAC dimmer compatibility and near unity power factor with no loss in efficiency.

An LED technology especially suited to use with domestic TRIAC dimmers. RAIS sits between the mains and the LED. LEDs Magazine published an article in June 2009 that explained the technology in more detail. Report L10270 from the Lighting Association Laboratories found the technology would work across different dimmer types while still maintaining a power factor of 0.96 with an input to output system efficiency of 91 per cent. As the light is dimmed, the system is able to hold a significantly higher efficiency than a Buck converter as RAIS draws a continuous current without using bleed resistors.

RAIS is a single stage supply that also delivers a constant current output to the LED with no sense resistor. The report also found that RAIS technology fitted into the dimensions of a standard GU10 lampholder (bayonet mount).

LED lighting typically involves LEDs connected in series. The resultant forward voltage may be in the region of 10 to 20V. In such cases, the ratio between the mains voltage and the voltage required to drive the load is between 10 and 20. With such a large ratio, conventional circuits used to drive LEDs become very inefficient because the switching will be operating at extremes of duty ratio with very short conduction times and high peak currents. This inevitably means that extra components, such as a common mode choke, need to be used. It is therefore common to include a magnetic or piezoelectric (ceramic) transformer with an input-to-output ratio suitable to create a step down in voltage and a corresponding step up in current. This though introduces further efficiency loss, cost and bulk.

In contrast, the RAIS technology can drive high current, low voltage LED strings from a 240V AC mains supply without high peak currents, a transformer or common mode choke and still achieve the turn’s ratio.

Typical Use: Between the mains and the LED with in a retro fit lamps such as a GU10 where small size and use with conventional TRIAC dimmers is required.

Special Features : Inherent Compatibility with a TRIAC dimmers through continuous current draw in the same way as a conventional lamp, in other words it looks like a resistor to the mains. This also has an impact on the efficiency as it does not require a bleeder circuit or holding current resistor to ensure proper TRIAC operation which can cause efficiency loss during dimming.

The topology is inherently constant current. There is no need for a second stage, current sensing, feedback or short circuit protection

Typical Performance of a TRIAC dimmable LED retrofit lamp, Power Factor 0.96, efficiency > 90%