Product Roundup LED Drivers

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For LEDs, the power supply, or driver, must match to the electrical characteristics of the device. Low-voltage in nature, LEDs require a constant and low DC voltage power supply to operate efficiently and enables LEDs to have longer stand-by power, increase safety, and easily adapt to different power supplies to operate efficiently.

LED drivers protect the light source from line-voltage fluctuations, which cause similar fluctuations in light output. These fluctuations can also shorten the useful life of an LED because of the heat involved, should the current to the LED exceed manufacturer recommendations.

Drivers are divided into two types:

  • Constant voltage,
  • Constant current.

Constant voltage is displayed in 10 V, 12 V and 24 V commonly, while constant current is displayed in 350 mA, 700 mA, etc. Drivers are typically specific to an LED, or there are general-purpose drivers that drive common LEDs.

Drivers can also dim or sequence LEDs. Dimming drivers commonly operate using pulse width modulation (PWM) so that the frequency ranges from 100 modulations/second up to hundreds of thousands of modulations per second; the latter minimizing flicker.  Integration of LEDs into circuits is common and has resulted in the reduction of the number of discrete components necessary in a design.

Drivers also enable color changing or sequencing so that LED driver output is converted into 3-channel output, typically RGB, and mixed to create a vast range of colors.

Designed for use in full color/monochrome large displays, the LED1642GWXTTR by STMicroelectronics is a monolithic, low-voltage, low-current power 16-bit shift register designed for LED panel displays. It guarantees 20 V output driving capability to connect several LEDs in series. Sixteen regulated current sources provide from 3 mA to 40 mA constant current of output to drive the LEDs. The current is programmed through an external resistor and can be adjusted by 7-bit current gain register in two subranges. A programmable turn-on and turn-off time improves a system’s low-noise generation performance. Features include thermal management equipped with an over-temperature data alert and an output thermal shutdown. High clock frequency makes the device suitable for high data-rate transmission.

Comparatively, the STMicroelectronics LED2000PUR driver is designed for high brightness LED driving, halogen bulb replacement, general lighting and signage applications. A 850 kHz fixed switching frequency monolithic step-down DC-DC converter is designed to operate as a precise constant current source with an adjustable current capability up to 3 A DC. Embedded PWM dimming circuitry features LED brightness control, and the regulated output current is set connecting a sensing resistor to the feedback pin. The size of the application is minimized with this driver based on high switching frequency and ceramic output capacitor compatibility.

LT3952EFEPBF LED 60 V driver with 4 A switch

Figure 1: The LT3952’s pseudorandom spread spectrum reduces average EMI without causing flicker during PWM dimming. (Source: Linear Technology)

The LT3952EFE#PBF LED driver by Linear Technology is designed for automotive and avionic lighting, accurate current-limited regulators and display backlighting. The 60 V driver with 4 A switch is designed to drive high-power LEDs in multiple configurations and combines input and output current regulation loops with output voltage regulation resulting in a flexible current/voltage source. Programmable switching frequency combined with optional spread-spectrum modulation delivers EMI reduction.

Main driver challenges include potential overload whereby too many LED strings are connected resulting in low voltage to the strings, or using the incorrect voltage driver. In this case, the LEDs will operate at higher currents than they should, the result of which is a shorter life, or they will not light up at all. 

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