IST Invents World’s Widest Dimming Dynamic Range LED and OLED Driver

Traditional LED drivers that use DC (non-pulsed) dimming usually have a limited current dimming ratio well below 256:1 and even LED drivers that utilise current pulses through the LEDs often only achieve 16-bit resolution in theory and 10-bits in practice, which culminates in lower colour and contrast control of LED fixtures.

As LED and OLED lighting fixtures increase in efficacy, their penetration of the lighting market will rapidly increase and many researchers are studying the health impacts of these new light sources. One of the major issues seen with artificial light sources such as LEDs is the health impact due to flicker/ripple current and the frequency of the flicker. The majority of LED dimming solutions available today can be categorised as either DC or pulsed dimming, but each method has significant drawbacks. With DC LED dimming solutions, the dimming dynamic range is usually 256:1 or less and the systems have a lower dimming range of between 5 and 20% before becoming unstable, according to the maximum forward current required. Pulsed dimming driver solutions based on modulation techniques such as Pulse Width Modulation (PWM) offer higher dimming dynamic ranges up to 65535:1, but have very high ripple currents (100%) that can cause noticeable visual effects and potential health issues, especially if the pulsing frequency is low (few hundred hertz).

The IST research and development team has spent the last 18 months developing and perfecting a new dimming control technique that has visual health and healthy lighting systems right at its core. The new healthy driver systems are built upon IST’s iDrive® digital signal processing (DSP) platform and provide 16-bit DC dimming with exceptionally low LED RMS ripple current of less than 5%. The system is able to control the LED or OLED forward currents down to 1 millionth of an Amp and offers up to 98% stage efficiency at a maximum forward current of 2100mA.

The new hybrid dimming solution also solves issues commonly found with switching stages, including:
• Hot plugging without blowing the LEDs
• Short circuit protection not only to ground but other switching output stages
• Channel bondable in order to create higher current outputs
• Common anode compatible for multichannel coloured LED fixtures
• Long life output stages, using solid-state capacitors with >300,000 hours
• Wide dimming dynamic range > 65,535:1 with no pulsing
• Software programmable maximum forward current (1uA to 2100mA)
• Extremely low RMS ripple current (<5%)
• Software programmable switching frequency (30kHz to 120kHz)
• Healthy driver compliant with DC output current (no pulsing)
• Wide LED/OLED forward voltage range (1V to 48V)

Dr Geoff Archenhold, Director and lead innovator at IST, enthused: “The IST team have invested close to 10 man years of development time in perfecting the hybrid dimming technology and we believe it offers the most advanced solution for those that are sensitive to healthy lighting system design. The team didn’t just focus on the technical challenges found in conventional driving techniques, but understood that driver costs were a key priority for our customers which meant we had to utilise standard off-the -shelf components to achieve the high performance. The technology works with all LED solutions and is just as applicable to OLED designs as it is with LEDs”.

Nina Blackmore, Marketing Manager at IST stated “The patented hybrid dimming system offers unparalleled dimming control and it now becomes simple to replicate incandescent lamp dimming with LED fixtures, as well as step-less dimming at very low light levels. Today, the highest efficiency LEDs switch on from just 100 millionth of an Amp and most customers find that even a 5% dimming level of a 700mA LED fixture (35mA) is too bright for the majority of applications, so the IST hybrid dimming solution offers future-proof dimming even for white LEDs that reach 250 lumens per watt levels”.

The new hybrid dimming technology will be available as standard in the iDrive® Quad 120W 4 channel, iDrive® Force 24 720W 24 channel, iDrive® Force 12 240W 12 channel, iDrive® White Knight 32 720W 32 channel and iDrive® Quattro CC 400W DC/DC LED drivers in Q1 of 2012.  

For further information on IST’s hybrid dimming system or any iDrive® LED driver products, then please contact Nina Blackmore at marketing@istl.com or by calling
+44 (0)1922 457712.

About IST:
IST Ltd is a world-class solid-state lighting company, specialising in the design and manufacture of innovative, ultra-efficient Serenity Lighting systems and iDrive® LED drivers.  
The Serenity Lighting portfolio supplied to OEMs includes patented white, dimmable LED downlighters, as well as RGB lighting solutions.  The company has experience in commercial, wide area, architectural, retail and entertainment applications.  
The research and development team has more than thirteen patents worldwide and a reputation for developing high-quality LED drivers used by global lighting companies.  The iDrive® LED driver range, including single, 3, 4, 24 & 36 channel, DMX/RDM, mains dimmable, 1-10V and DALI solutions, provide a high degree of innovation, significant energy efficiency and the world’s first variable voltage, variable current drivers.  
IST offers over 20 years’ experience in traditional and solid-state lighting solutions, including award winning electronic and optical system designs including controllers, luminaires, light engines and LED drivers.