Universal-Input/140 W Off-Line Quasi-

Resonant Flyback Switching Regulator

STR-W6756

Sanken Power Devices

from Allegro MicroSystems

Switching

Regulators

ABSOLUTE MAXIMUM RATINGS

Peak Drain Switching Current,

Single-Pulse Avalanche Energy,

OCP/BD Voltage Range,

10 mA

–0.5 V to +9 V

Operating Temperature Range,

-20°C to +115°C†

Storage Temperature Range,

-40°C to +125°C

* Drain switching current is limited by tem-

perature (page 2) and safe operating area

(page 5).

†For the availability of parts meeting -40°C

requirements, contact Allegro’s Sales Represen-

tative.

The STR-W6756 is a quasi-resonant regulator specifically designed

to satisfy the requirements for increased integration and reliability in

switch-mode power supplies. It incorporates a primary control and drive

circuit with an avalanche-rated power MOSFET. The regulator exhibits

only low-level high-frequency EMI noise because of soft switching of

the MOSFET close to ground (bottom point). A bottom-skip function

minimizes an increase of operational frequency during light loads to

improve system efficiency over the entire load range.

Covering the power range from below 240 watts for a 230 VAC

input, or 140 watts for a universal input (85 to 264 VAC), this device

can be used in a range of applications, from DVD and VCR players to

ac adapters for cellular phones and digital cameras. An auto-standby

function, which is internally triggered by sensing on time, reduces

power consumption at light load. An externally triggered standby mode

reduces the input power further. Multiple protections, including the

avalanche-energy-guaranteed MOSFET, provide high reliability of

system design.

Cycle-by-cycle current limiting, undervoltage lockout with hyster-

esis, and overvoltage protection protect the power supply during the

normal overload and fault conditions. Overvoltage protection is latched

after a short delay. The latch may be reset by cycling the input supply.

Low start-up current and a low-power standby mode selected from the

secondary circuit completes a comprehensive suite of features. The

STR-W6756 is provided in a fully molded TO-220-style flange-

mounted, high power, isolated plastic package.

■ Rugged 650 V Avalanche-Rated MOSFET

Simplified Surge Absorption

■ 0.73

DS(on)

■ Two Operational Modes by Automatic Switching:

Quasi-Resonant Mode for Normal Operation

Burst Mode for Standby Operation or Light Loads

■ Automatic or Manually Triggered Burst Standby

Input Power <0.1 W at No Load

■ Low Operating Current (6 mA typ)

— continued

Always order by complete part number, e.g., STR-W6756 .