STR-W6735: Quasi-Resonant Topology Primary Switching Regulators

The STR-W6735 is a quasi-resonant topology IC designed for SMPS applications. It shows lower EMI noise characteristics than conventional PWM solutions, especially at greater than 2 MHz. It also provides a soft-switching operation to turn on the internal MOSFET at close to zero voltage (VDS bottom point) by use of the resonant characteristic of primary inductance and a resonant capacitor.

The package is a fully molded TO-220, which contains the controller chip (MIC) and MOSFET, enabling output power up to 160 W with a 120 Vac input. The bottom-skip function skips the first bottom of VDS and turns on the MOSFET at the second bottom point, to minimize an increase of operational frequency at light output load, improving system-level efficiency over the entire load range.

There are two standby functions available to reduce the input power under very light load conditions. The first is an auto-burst mode operation that is internally triggered by periodic sensing, and the other is a manual standby mode, which is executed by clamping the secondary output. In general applications, the manual standby mode reduces the input power further compared to the auto-burst mode.

The soft-start function minimizes surge voltage and reduces power stress to the MOSFET and to the secondary rectifying diodes during the start-up sequence. Various protections such as overvoltage, overload, overcurrent, maximum on-time protections and avalanche-energy-guaranteed MOSFET secure good system-level reliability.

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  • Features and BenefitsFeatures and Benefits
  • PackagingPackaging
  • Technical DocsTechnical Docs
  • NewsNews
  • Quasi-resonant topology IC → Low EMI noise and soft switching
  • Bottom-skip operation → Improved system efficiency over the entire output load by avoiding increase of switching frequency
  • Standby burst mode operation → Lowers input power at very light output load condition
  • Avalanche-guaranteed MOSFET → Improves system-level reliability and does not require VDSS derating
  • 500 V / 0.57 Ω, 160 W (120 Vac input)
  • Various protections → Improved system-level reliability
    • Pulse-by-pulse drain overcurrent limiting
    • Overvoltage protection (bias winding voltage sensing), with latch
    • Overload protection with latch
    • Maximum on-time limit

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Functional Block Diagram Package

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
STR-W6735 6-lead TO-220 -20°C to 115°C Yes View Data New Contact your
local sales rep
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