Offline quasiresonant flyback switching regulator

The STR-G6651 from Allegro MicroSystems Europe is specifically designed to satisfy the requirements for increased integration and reliability in offline quasiresonant flyback convertors.

The STR-G6651, now available from Allegro MicroSystems Europe, is specifically designed to satisfy the requirements for increased integration and reliability in offline quasiresonant flyback convertors.

The device offers a robust, economical, low-risk solution for off-line switch-mode power supplies, particularly where management of electromagnetic interference at the source is a significant element of the system design.

The new product is a hybrid power integrated circuit incorporating the primary control and drive circuit, along with a discrete avalanche-rated power mosfet operating at up to 650V.

Output power rating is up to 70W.

Cycle-by-cycle current limiting, undervoltage lockout with hysteresis, overvoltage protection, and thermal shutdown protect the power supply during the normal overload and fault conditions.

Overvoltage protection and thermal shutdown are latched after a short delay.

The latch can be reset by cycling the input supply.

Other features include an active lowpass filter for enhanced light-load stability, adjustable switching speed for EMI control, and switched attenuation of the leading-edge current-sensing signal.

Low-current startup and a low-power standby mode selected from the secondary circuit complete a comprehensive suite of features.

The device is supplied in a 5-pin overmoulded TO-220 style package, affording dielectric isolation without compromising thermal characteristics.

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