Diodes Incorporated – Offline PFC controller features low stand-by power consumption


Diodes Incorporated has introduced the AL1788 high-performance AC-DC constant-voltage and Power Factor Correction (PFC) controller. Offering a combination of high PFC, low Total Harmonic Distortion (THD) and low stand-by power, it is well suited to use in commercial applications and connected lighting.

Based on a platform that supports both flyback and buck topologies, the AL1788 is designed for primary-side regulation, which removes the need for feedback signals to be optically coupled from the secondary side.

The AL1788 provides outstanding performance: high efficiency of up to 91%, good line and load regulation of 2% over a full range of conditions, and low stand-by power consumption of 0.9.

The AL1788 operates with an external MOSFET to supply a constant voltage to an LED load. The high power factor is achieved through constant on-time operation, while its quasi-resonant valley-switching method minimises switching losses and EMI.

The controller’s implementation of primary- side regulation helps to reduce the complexity of the secondary side of an LED driver’s circuit, resulting in a lower 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 draws a low start-up current of 3μA, and operating current of 500μA. It enables users’ designs to meet the requirements of regulations that restrict stand-by power.


  • Universal AC mains input-voltage range
  • Output-open protection
  • Output-short protection
  • Over-current, over-voltage and over-temperature protection
  • Under-voltage lock-out


  • General LED lighting
  • Smart connected LED light sources
  • Power supplies that require high PFC and low THD