This efficient 16V 4A AC switching power supply employs an isolated-flyback power-supply controller that provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. The 16 volt ac power supply processes information from opto-coupled feedback and an auxiliary flyback winding for high-performance control of output voltage and current. The output voltage is regulated accurately by a high-performance voltage-mode amplifier with an accurate voltage reference. The 16 volt power supply uses power-saving technologies limits the no-load power consumption to lowest level resulting in excellent efficiency performance. The precise output over-voltage protection greatly enhances the system reliability. The 16 volt ac power supply offers good EMC, and keeps high PF and low total harmonic distortion (THD) under universal input voltage. Effective thermal management reduces thermal stress on power supply reliability, allows the 16 volt dc power supply to operate at full power at higher ambient temperatures (see our UL/TUV documents).