OB2374 is an excellent primary side regulation controller with CC/CV operation for medium level power AC/DC charger and adapter applications. The device directly drives a power MOSFET and 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. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below.

In CV control, the controller changes the mode of operation according to line voltage and load condition. At full loading, the controller operates in fixed frequency CCM in low line voltage and operates 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.

In CC control, OB2374 samples the Vcs peak current and the demagnetization pulse to regulation the output constant current. The current and output power setting can be adjusted externally by the sense resistor Rs at CS pin.

OB2374 offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD OVP, OLP, SCP, OTP etc.

OB2374 consumes less than 75mW input power at no- load condition with high line voltage.

OB2374 is offered in SOT23-6 package.

Figure.1. Typical CC/CV Curve



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

   High precision constant voltage and current regulation at universal AC input

   Fixed frequency (65kHz) CCM mode operation with low line voltage at full load

   Quasi-resonant operation for high efficiency in high line voltage

   Good dynamic response

   Programmable CV and CC regulation

   Built-in primary winding inductance compensation

   Programmable cable drop compensation

   Built-in control loop compensation

   External over temperature protection with latch shutdown (OTP)

   Audio noise free operation

   Built-in leading edge blanking (LEB)

   Ultra low start-up current and low operating current

   Comprehensive protection coverage with auto-recovery

o    VDD over voltage protection (OVP)

o    VDD under voltage lockout with hysteresis (UVLO)

o    Cycle-by-cycle current limiting

o    Feedback open loop protection (OLP)

o     Output short circuit protection (SCP)



Medium level Power AC/DC offline SMPS for

n  Cell phone charger

n  Tablet PC

n  AC/DC adapter

n  Set-top box power supplies