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EFFICIENT LIGHT SOURCES REQUIRE EFFICIENT DRIVERS!

2009-09-01  MPS

The “snowball effect” can already be felt, as the advance of LEDs as a lighting source can no longer be halted! And, finally, the topic of energy savings has entered the focus of companies, consumers and politicians alike.

More and more, LEDs are proving their worth as the light source that most efficiently converts electrical energy into light. However, the process of generating light is still tied to an undesirable amount of heat generation.

It’s a fact that achieving acceptably high efficiencies with these modern light sources not only requires continuous improvements in luminous efficiency, but also an efficient, space-saving and cost-effective driver circuit.

This DC/DC converter can be implemented very compactly since the chip itself measures only 3mm x 3mm x 1mm (plus another 1mm each on the two sides with connecting pins), while the high switching frequency of 1.4MHz furthermore enables the use of very small peripheral components. With a feedback voltage of only 200mV, current regulation can be accomplished with low losses to help achieve good efficiency (see Figure 2). In standby, the converter loads the voltage source with a mere 5µA.

The MP2481 is very flexible to use, as it serves equally well as a step-down converter or in buck/boost topologies. Thus, one and the same circuit can cover a wide range of input voltages. The MP2481 can handle voltages of up to 40V and operates at as low as 4.5V. The internal

300mOhm MOSFET can withstand up to 2A; which, for example, enables a 10V / 200mA supply from a 5V input voltage.

Another attractive feature of this regulator IC is the fact that output current dimming can be implemented either with an analog signal (from 0.7V to 1.4V for the entire range) or with PWM (100Hz - 1000Hz). Of course, the device also integrates typical protective functions: e.g., overtemperature and overvoltage protection at the output (for LED failure).

To minimize their customers’ development effort, most manufacturers offer a demo/evaluation kit for their devices. However, the MP2481’s manufacturer – MONOLITHIC POWER SYSTEMS (MPS) – provides the evaluation kit at no cost!  The corresponding board is shown in Figure 3. In this case, it is equipped with a step-up/step-down converter which drives 27 white LEDs (3 to a row in 9 parallel chains) using an input voltage ranging from 4.5V to 26V.

The MP2481 is a universal chip that goes a long way towards meeting the comprehensive needs of designers engaged in the development of modern lighting systems. Like system designers, purchasing departments, too, are interested in minimizing the number of different product types required to meet the design goals. And the good news is that the MP2481 can help meet this goal, thanks to its unmatched versatility!

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IMp_2_2009_A 04_MPS_Effiziente Lichtquellen_Bild4_kl.jpg
Bild 1: Blockschaltdiagramm
IMp_2_2009_A 04_MPS_Effiziente Lichtquellen_Bild5_kl.jpg
Bild 3: MP2481 Board

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