Part Number: STR-W6753, STRW6753, STRW-6753
Function: Quasi-Resonant Switching Regulator
Package: TO-220-7 Pin Type
Manufacturer: Allegro MicroSystems
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Description
The STR-W6753 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.
Key Architecture
- Integrated PWM controller + 650V avalanche-rated MOSFET
- Quasi-resonant (QR) switching for low switching loss
- Valley switching (turn-on near VDS minimum)
- Primary-side control (no optocoupler required in some designs)
- Burst mode operation for light-load efficiency
Application circuts
Features
1. Rugged 650 V Avalanche-Rated MOSFET Simplified Surge Absorption No VDSS Derating Required
2. 1.7 Ω Maximum rDS(on)
3. Two Operational Modes by Automatic Switching :
(1) Quasi-Resonant Mode for Normal Operation
(2) Burst Mode for Standby Operation or Light Loads
4. Automatic or Manually Triggered Burst Standby Input Power <0.1 W at No Load
5. Low Operating Current (6 mA typ)
Absolute maximum ratings
1. Control Supply Voltage : VCC = 35 V
2. Drain-Source Voltage : VDSS = 650 V
3. Drain Switching Current : ID = 11.2 A
4. Peak Drain Switching Current : IDM = 11.2 A
5. Single-Pulse Avalanche Energy : EAS = 145 mJ
6. Package Power Dissipation : PD = 0.8 W
Typical Circuit Usage
- AC-DC flyback converter (85~265VAC input)
- CRT / LCD TV power supply
- Set-top box SMPS
- Adapters and chargers (low to mid power)
- Auxiliary standby power supplies
Design Notes (Critical Points)
- Transformer design is key (QR operation depends on resonance timing)
- Snubber network still required, but can be simplified
- Ensure proper VCC startup resistor and auxiliary winding design
- Thermal design must consider internal MOSFET dissipation
- Layout: minimize loop area of primary switching path
Advantages vs Conventional PWM Flyback
- Lower switching loss (valley switching)
- Lower EMI (soft switching)
- Higher efficiency at light load (burst mode)
- Reduced external components
Applications
- TV SMPS (very common in CRT/LCD designs)
- Consumer electronics power supplies
- Industrial auxiliary power
- Low standby power designs (Energy Star compliant)
Alternative / Equivalent Products
- STR-W6754 / STR-W6756 (higher power variants)
- NCP1207 (ON Semiconductor)
- ICE2QR series (Infineon)
- TNY277 (Power Integrations – lower power range)
Other data sheets are available within the file: STRW6753
STR-W6753 Datasheet PDF Download
