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Offline constant voltage and PFC controller from Diodes

Diodes Incorporated has introduced the AL1788, a high-performance offline constant voltage and PFC controller.

It has been developed to combine high power factor correction (PFC) with low total harmonic distortion (THD) and low standby power, making it suited for commercial applications and connected lighting requirements.

Based on a platform that supports both flyback and buck topology, the AL1788 is intended for primary side regulation (PSR), which removes the need for feedback optically coupled from the secondary side. This delivers an improved level of performance, such as high efficiency of up to 91%, good line and load regulation of 2% over a full range of line and load regulation, and low standby power of less than 0.2 Watts.

With a PFC of >0.9 and low standby power it 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.

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 its PFC and THD performance across a wide input range over a load from 50% to 100% and features low start-up and operating current of just 3μA and 500μA, respectively (typical), combined with ‘Burst Mode’ operation. The AL1788 enables users’ designs to meet low standby power system requirements.

Comprehensive protections are integrated, including output-open protection and output-short protection, as well as overcurrent, overvoltage and over-temperature protection. Undervoltage lockout has also been 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.

Author
Neil Tyler

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