LEDs behave differently to other lighting methods and therefore require a special drive circuit in order to take advantage of all LED properties.

The most well-known LED property is its high luminous efficiency, small design and long service life. Not so wellknown, however, is the fact that LEDs must be run with constant current as opposed to constant voltage in order to provide optimal performance.

While, at first glance, the LED gives the impression of being a prefect illuminant, its negative properties are not to be ignored. These include the temperature sensitivity of the forward voltage TK = –3.6 to –5.2mV/K, the high manufacturing tolerance of the forward voltage 2.7 to 3.8 V or the color drift when the cell voltage is changed.

Different circuit variations are available as possible solutions for providing an LED with constant current. The LED is either supplied with a higher current, using a series resistor, or a linear controller with the appropriate circuit is chosen. Transistor or JFET current sources or sinks can also be used. All methods mentioned have one thing in common – they “burn” the excess energy and deteriorate the overall efficiency of the lighting system.

As the LED is a lighting method that converts very efficiently electrical energy into light, a similar behavior regarding energy efficiency is expected from the drivers. As a manufacturer of DC/DC converters and switch mode regulators, Recom has spent decades studying energy conversion. It is therefore logical that Recom applies its accumulated special knowledge in the development of this LED driver series.

The LED drivers from the RCD-24 series can boast a maximal efficiency of 98%. This high efficiency means the driver can be used with ambient temperatures of 85 °C when in full drive capacity. This high efficiency is enabled by a step-down circuit used as a circuit topology. The input voltage range reaches from 4.5 to 36 V. Individual models are available for each of the 300, 350, 500, 600 and 700mA output currents and 800, 900, 1,000 and 1,500mA versions are already being developed. In addition, output currents can be regulated using analog or digital dimmers (PWM).

Analog and digital dimmers can also be used simultaneously. Analogue dimmers produce a constant but reduced current according to the control voltage, whereas PWM dimmers produce current pulses, the average of which is the required current value. This means, for example, that reduced current can be produced using an analogue dimmer compared with the nominal current. This reduced current can then be additionally dimmed using the PWM method.

The frame size of the encapsulated plastic casing for the leaded version measures 22.1 x 12.6 x 8.5 mm. A version with cast-in incoming wires is offered in the same housing and can be delivered with plug connectors by request, depending on the order quantity. UL-94V-0 material is used for housing and encapsulation.

As these drivers produce a regulated constant current, LED shortcomings, such as manufacturing tolerance, temperature gradient of the forward current and color drift, can be counterbalanced. RCD-24 drivers are planned as ready-to-use solutions, making external components unnecessary. Together with the outstanding LED properties and the excellent properties of the LED driver from Recom, the combination of both components forms a perfect lighting system.

For detailed specifications please contact your local Sasco Holz Branch Office.