Offline constant voltage and PFC controller for connected LED lights

December 07, 2017 // By Nick Flaherty
Diodes has launched an offline constant voltage and power factor correction (PFC) controller with low total harmonic distortion (THD) and low standby power for connected lighting applications.

The AL1788 is designed for primary side regulation (PSR), which removes the need for feedback optically coupled from the secondary side. This delivers efficiency of up to 91%, line and load regulation of 2% over a full range of line and load regulation, and standby power of less than 200mW.    

With a PFC of >0.9, the AL1788 operates with an external MOSFET to deliver constant voltage to an LED load. This high power factor is achieved through constant on time operation, while its quasi-resonant mode valley switching method minimises switching losses for improved EMI performance. 

By exploiting PSR, the complexity of the secondary side is reduced, enabling a smaller overall profile suitable for solid state lighting installations. The output voltage is regulated when operating in constant-voltage mode through feedback provided by an auxiliary winding, coupled to the secondary side winding. 

The AL1788 maintains the PFC and THD performance across a wide input range over a load from 50% to 100%. It features low start-up and operating current of just 3μA and 500μA, respectively (typical), combined with ‘Burst Mode’ operation. 

It includes output-open protection and output-short protection, as well as overcurrent, overvoltage and over-temperature protection. Undervoltage lockout is also integrated. 

The controller-only version of AL1788 is available now and provided in the SOT26 (SC74R) package, while the MOSFET regulator options will be supplied in an SO-7 package and will be released in 2018.  Both are lead, halogen, and antimony free and fully RoHS compliant. 

Available in quantities of 1k units, AL1788 controllers can be purchased for $0.17 each. 

www.diodes.com