By Microchip Technology 44
The CL88030 and CL88031 LED drivers from Microchip are intended-offline sequential linear LED drivers designed to provide LED power from a utility voltage input. The CL88030/31 uses a self-commutation technique which inherently provides smooth transitions from one regulator to the next without relying on tap voltages or the rectified AC to coordinate the transitions. The devices are designed to drive a long string of inexpensive, low-current LEDs directly from the AC mains. A basic driver circuit consists of Microchip’s CL88030/31 LED driver IC, four (CL88030) or six (CL88031) power FETs, four resistors, two capacitors, and a bridge rectifier. Various levels of transient protection can be achieved by adding optional components. Overtemperature protection (OTP) is assured by adding an NTC thermistor. No EMI filters or power factor correction circuits are needed unless the optional flicker-reduction feature is desired.
A string of series/parallel LEDs is tapped at four (or six) locations, called taps. The linear current regulators sink current at each tap through a single control point and are sequentially turned on and off. High efficiency is achieved by shutting off upstream regulators when downstream regulators achieve regulation. This makes controlling overall input current easier than trying to control multiple current paths by tracking the input sine wave voltage. The CL88030/31 uses a self-commutation technique that uses only the tap currents. This technique inherently provides smooth transitions from one regulator to the next, without relying on tap voltages or the rectified AC to coordinate the transitions. The LED drivers are ideal for LED lamps, LED lighting fixtures, consumer electronics, and industrial applications.