OB3840 Flyback Power Switch

The OB3840 is a highly integrated current-mode PWM controller for isolated flyback converters, combining high performance with low system cost. The switching frequency is internally fixed at 50 kHz; as the load falls the device enters green mode, and at light or no load the frequency folds back to a minimum of 23 kHz. Low startup and operating currents keep standby power low and make startup reliable. Protection includes cycle-by-cycle current limiting, VCC undervoltage lockout (UVLO), VCC overvoltage protection (OVP), over-temperature protection (OTP) and output-diode short-circuit protection. At the 23 kHz minimum the energy per cycle is at its lowest, which removes the dummy-load loss and eliminates audible noise. Available in DIP-8, SOP-8 and SOT-23-6.

Key Features

• Soft start at power-up reduces MOSFET voltage stress
• No audible noise in normal operation
• Strong-pulse burst mode for light-load efficiency
• Fixed 50 kHz typical switching frequency, foldback to 23 kHz
• Cycle-by-cycle current limiting
• VCC UVLO, VCC OVP, OTP and output-diode short-circuit protection
• Low startup and operating current for low standby power

Applications

• Isolated AC/DC flyback converters
• General-purpose power supplies
• Adapters and chargers

Part Numbers

• OB3840

Product family: On-Bright official page