The offline constant voltage and power factor correction (PFC) controller from Diodes Inc. offers low standby power for connected LED lighting and is targeted at commercial applications. The AL1788 controller combines PFC with low total harmonic distortion (THD) to deliver standby power of less than 0.2 W.
Additionally, AL1788 is designed for primary side regulation (PSR), which removes the need for feedback optically coupled from the secondary side. That ensures efficiency of up to 91% and good line-and-load regulation of 2% over a full range of line-and-load regulation.
The controller chip utilizes PSR to reduce the complexity of the secondary side and thus enable a smaller profile suitable for solid-state lighting installations. Next, with a PFC of less than 0.9 and lower standby power, the AL1788 can operate with an external MOSFET to deliver constant voltage to an LED load.
The high power factor is achieved through constant on-time operation. And its quasi-resonant mode valley switching method minimizes switching losses and provides a robust EMI safeguard.
The AL1788 controller chip maintains strong PFC and THD performance across a wide input range over a load ranging from 50% to 100%. Then there is output voltage that is regulated when operating in constant-voltage mode through feedback provided by an auxiliary winding while being coupled to the secondary side winding.
Furthermore, AL1788 features low start-up and operating current of just 3 μA and 500 μA, respectively. That allows connected LED lighting designs to meet low-standby-power system requirements.
The controller chip also integrates output-open protection and output-short protection as well as protection for overcurrent, overvoltage, and overtemperature.
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