Product category:
Power Supply ICs and Controllers
News Release from: Prema Semiconductor | Subject: PR4403
Edited by the Electronicstalk Editorial
Team on 26 November 2007
LED driver powers green lighting
Boost driver device reduces component count by handling both charging and driving in solar-powered LED lighting applications.
Prema Semiconductor has extended its family of LED drivers with a boost driver for solar applications The new PR4403 drives and controls white LEDs from a single battery charged by solar cells
This article was originally published on Electronicstalk on 30 Jun 2008 at 8.00am (UK)
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Dual photodiodes target applications in light measurement, laser beam alignment in laser printers and DVD/CD players, optical encoders and light barriers.
It uses the connected solar cells to detect daylight.
LED solar lamps operate with automatic LED control depending on the ambient light level.
The battery is charged by solar cells.
Normally this requires several components such as Schottky diodes, capacitors, resistors, two or three rechargeable battery cells and a photoresistor.
In contrast to this standard solution the PR4403 saves several components, as it is able to drive the current for the white LED out of a single rechargeable battery cell.
Also the expensive photoresistor is no longer needed.
A supply voltage of down to 0.9V is sufficient for the IC to drive a current of up to 40mA independent of the input voltage.
The value of the external inductor defines the LED current.
Instead of the photoresistor, the solar cell is directly connected to the IC for daylight level detection, and an optional resistor sets the light threshold.
Depending on the voltage at this connection, the integrated step-up convertor is switched on or off.
During daytime the driver is shut down and the solar cell charges the battery via the external Schottky diode.
With decreasing ambient light the voltage at the solar cell drops, the IC is activated and drives the LED current out of the battery cell.
Deep discharge of the battery cell is prevented as the PR4403 shuts off the driver when the supply voltage drops to less than 850mV.
Applications for the PR4403 are solar garden lamps as well as house number lights, decoration lights and road markers powered by solar cells.
Samples are available on request in SO8 packages.
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