Offline constant voltage and PFC controller suits connected lighting

Diodes has released the AL1788, an offline constant voltage and power factor correction (PFC) controller that offers low standby power for connected LED lighting.

The AL1788 has been developed to combine high PFC with low total harmonic distortion (THD) and low standby power, making it suitable for commercial applications and connected lighting requirements, says Diodes.

Due to being based on a platform that supports both flyback and buck topology, it 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 per cent, good line and load regulation of two per cent over a full range of line and load regulation, and low standby power of less than 0.2W.

With a PFC of up to 0.9 and lower standby power than its competitors, claims Diodes, the AL1788 operates with an external MOSFET to deliver constant voltage to an LED load. The high power factor is achieved through constant on time operation, while its quasi-resonant mode valley switching method minimises switching losses and provides outstanding EMI performance.

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

PFC and THD performance is maintained across a wide input range over a load from 50 to 100 per cent. The AL1788 features low start-up and operating current of 3.0 and 500-microA, respectively (typical), combined with Burst Mode operation to meet low standby power system requirements.

The controller has integrated output-open protection and output-short protection, as well as over-current, over-voltage and over-temperature protection. Under-voltage lockout is also integrated.

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


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