Harvard Technology: driving forward

Harvard Technology’s new programmable generation of CoolLED drivers represents a massive step change in LED driver functionality.

In a time of innovation there are two possible directions that an innovative company can take. Either throw out what’s gone before and release the next big thing – or go deeper into what they know best and innovate by doing what they do, better. And by introducing us to Generation lll of the CoolLED range of LED constant current drivers, Harvard Technology has done the lighting industry an enormous favour.

As time is moving so quickly in lighting technology, it’s worth spending a minute reminding ourselves of what Generations I and II were all about.

Generation l was the first iteration of the LED driver, and Harvard offered the largest range of high efficiency, high power factor drivers available at that time. It did what it said on the tin and provided a tidy and efficient link from the mains supply to the delicate LED module. But that’s just about all that it did. The clever versions understood dimming, of course, and varying degrees of success were available with phase, analogue and DALI dimming protocols.

Generation ll provided the first demonstration of doing what you know – only doing it better. Improved dimming conditions were created with more sophisticated integrated circuit (IC) technology leading to smoother and deeper dimming.

The most obvious – and expensive – aspect of Generations l and ll remained, however – shelves and shelves of hundreds of versions of drivers. With driver manufacturers caught between the rock of holding instantly-available stock and the hard place of an aggressive pricing market, something was needed to shift the financial pressure caused by having to second-guess what clients wanted (and expected) by the end of each working day. The answer is a simple one, provided you can achieve it – one piece of hardware providing thousands of software options. Say hello to Generation III and the latest and greatest driver development in the form of the CL Pro range.

The change came in mid-2016. New integrated circuit technology became available, both powerful and of high quality. Driver designers saw immediately that these new ICs, while being physically very small, could not only impact on the performance of the next generation of drivers, but would also change the form factor. The world was about to become much smaller.

If we look at the headline figures for the latest generation of Harvard CoolLED, it’s easy to see how the benefits add up:

  • A maximum current of 1050ma on all models, with a higher 40W output driver in the pipeline
  • Either 1-12 LEDs or 2-18 LEDs supported by a single driver
  • Reduced total output power range at almost 45dB (less than 2mW to 40W)

And if we step outside the driver housing, we can appreciate the added control benefit of a 15W driver that uses mains ‘touch dimming’ via the DALI terminal. And to make electricians even happier, there are push-fit terminal blocks on all models. It’s clear that the Harvard designers have been looking to please everyone along the line when it comes to installing and using the new CoolLED drivers.

One of the major improvements in driver performance comes from the use of twin stage circuit design. This is where those new ICs come in. You would expect the circuit losses to accrue with every stage, but the new IC-enabled circuits are delivering comparable or better figures. Overall efficiency of the 15W driver is at 84 per cent, with the 40W driver reporting an efficiency of 87.5 per cent. Inrush currents are reduced, giving confidence to the electrical designer that these drivers can be protected using MCBs – a regular source of irritation and embarrassment up to now.

A few of the operational features are worth reporting.

  • These drivers deliver near-perfect ‘ripple-free’ DC power to the LED load at any current setting, meeting IEEE1789:2015 ‘no effect’ standards, making the drivers ideal for specialist applications such as video conferencing. These drivers are also fully compatible with performance requirements for TV filming.
  • Circuit design and a rigorous testing regime mean that electromagnetic compatibility (EMC) performance is improved, potentially eliminating installation issues.
  • The drivers are fast-starting, with a non-dimming version taking only 0.014 seconds to come to full light.

For lighting specifiers, there are other things to look forward to. These drivers are small. The redesigned CLi10/15W driver delivers high performance within an ultra-slim, low profile form factor that requires only a 40mm diameter hole for mounting within ceilings.

And the CoolLED Pro range will complement the fast-growing range of programmable drivers:

  • CLK (in-fixture housing): 97 x 43 x 30mm (integral version)
  • CLS (linear housing): 280 x 30 x 21mm
  • CLX (standalone housing): 120.75 x 85 x 22mm (integral version)

The programming methodology is simplicity itself. The performance parameters are entered into a (Windows-based) PC, from which either a standard USB connection or a special programming jig is used to transfer the information to each driver. It is reckoned to take around two seconds to programme each driver.

A wireless programming option is also available via a radio frequency identification (RFID) connection. Drivers can be reprogrammed in situ, without being powered up via a compatible RFID connection such as ThingMagic or the KathreinRRU4 RFID reader/writer.


Harvard Technology promises yet more versions of the CoolLED programmable driver, including constant power, constant lumen and constant voltage options. We await those additions with great interest.