OB2579T is an excellent primary side regulation power switch for medium level power AC/DC  adapter applications. The device operates in CCM/QR mode to provide high efficiency along with several functions of built-in protections. It removes the need for secondary feedback circuitry to lower the total bill of material cost. The OB2579T can operate at peak power mode with momentary peak power higher than maximum continuous output power without design cost and size increase. In CV control, the controller changes the mode of operation according to line voltage and load condition. At full loading, the controller operates in CCM in low line voltage and quasi-resonant (QR) mode in high line voltage. The primary side regulation power supplies up to high power without the efficiency limitation of DCM or audible noise.

OCP control, OB2579T samples the primary-side average current and the demagnetization pulse to regulation the output current. The current and output power setting can be adjusted externally by the sense resistor Rs at CS pin.

OB2579T offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD OVP, OLP, SCP, OTP etc.

OB2579T consumes less than 75mW input power at no-load condition with high line voltage.

OB2579T is offered in SOP8 package.


n Primary-side sensing and regulation operates in CCM/QR mode without TL431 and opto-coupler

n High precision constant voltage and current regulation at universal AC input

n Maximum frequency (90kHz) CCM operation at peak load mode

n Integrated power MOSFET

n Quasi-resonant operation for high efficiency in high line voltage

n Programmable CV regulation

n Good dynamic response

n Built-in line compensation for tight OCP regulation

n Built-in fixed cable compensation

n Built-in primary winding inductance compensation

n Built-in control loop compensation

n Built-in leading edge blanking (LEB)

n Ultra low start-up current and low operating current

n Comprehensive protection coverage with auto-recovery

l VDD over voltage protection (VDD OVP)

l VDD under voltage lockout with hysteresis (UVLO)

l Cycle-by-cycle current limiting

l Feedback open loop protection (OLP)

l  Output short circuit protection (SCP)


Medium level Power AC/DC offline SMPS for

n Tablet PC

n AC/DC adapter

n Network power supplies