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Power Integrations


Power Integrations – INN3647/9 1700V InnoSwitch3-EP Flyback Switcher

Off-Line CV/CC QR Flyback Switcher IC with Integrated Primary-Side Switch, Synchronous Rectification and FluxLink Feedback

The InnoSwitch™3-EP family of ICs by Power Integrations dramatically simplifies the design and manufacture of flyback power converters, particularly those requiring high efficiency and/or compact size. The InnoSwitch3-EP family combines primary and secondary controllers and safety-rated feedback into a single IC.

InnoSwitch3-EP family devices incorporate multiple protection features including line over and undervoltage protection, output overvoltage and over-current limiting, and over-temperature shutdown. Devices are available with standard and peak power delivery options, and commonly used auto-restart protection behaviors.


Product Highlights

Highly Integrated, Compact Footprint

  • Very high efficiency across full load range
  • Incorporates a multi-mode Quasi-Resonant (QR) / CCM flyback controller, high-voltage switch, secondary-side sensing and synchronous rectification driver
  • Excellent multi-output cross regulation with weighted secondary-side
  • regulation (SSR) feedback and synch FETs
  • Integrated FluxLink, HIPOT-isolated, feedback link
  • Exceptional CV/CC accuracy, independent of external components
  • Adjustable accurate output current sense using external output sense resistor
  • PowiGaN™ technology – up to 100 W without heat sinks (INN3678C, INN3679C and INN3670C)

EcoSmart – Energy Efficient

  • Less than 30 mW no-load including line sense
  • Easily meets all global energy efficiency regulations
  • Low heat dissipation

Advanced Protection / Safety Features

  • Open SR FET-gate detection
  • Fast input line UV/OV protection
  • Auto-restart fault response for output OVP
  • 725/750 V Switch rating series for excellent surge protection
  • 900/1700 V Switch rating series for industrial design or extra safety

Optional Features

  • Auto-restart output UV protection with option for peak power delivery

Full Safety and Regulatory Compliance

  • Reinforced isolation
  • Isolation voltage >4000 VAC
  • 100% production HIPOT testing
  • UL1577 and TUV (EN60950, EN62368) safety approved
  • Excellent noise immunity enables designs that achieve class “A” performance criteria for EN61000-4 suite; EN61000-4-2, 4-3 (30 V/m), 4-4, 4-5, 4-6, 4-8 (100 A/m) and 4-9 (1000 A/m) and Ford FMC1278 (RI-115)

Green Package

  • Halogen free and RoHS compliant


  • Auxiliary, standby and bias power supplies for appliances, computers and consumer products
  • Utility meter, smart grid and industrial power supplies


Output Power (Max) - Open Frame, 230V 45.00 W (INN3647C)
65.00 W (INN3649C)
Output Power (Max) - Open Frame, Univ 50.00 W (INN3647C)
70.00 W (INN3649C)
Switching Frequency (min) 25.00 kHz
Switching Frequency (max) 95 kHz
Breakdown Voltage 1700 V
Voltage - Output (Min) 5.00 V
Voltage - Output (Max) 24.00 V
Voltage - Input (Min) 40 V
Voltage - Input (Max) 1200 V
Auto-Restart & Overvoltage Response Auto-restart
Latch Off
Auto-Restart Threshold OL
IC Package InSOP-24D
Internal Switch Yes
Over-Temperature Response Hysteretic
Temperature - Operating (Min) -40 °C
Temperature - Operating (Max) 150 °C
Control Scheme Fluxlink
Protection Features Input Undervoltage
Open SR FET Detection
Output Overload
Output Overvoltage
Output Short Circuit
Output Profile CV
Topology Flyback
Product Sub-Type PMIC
MSL Rating 3
Secondary Response Auto-restart
Latch Off


InnoSwitch3-EP Switcher IC Block Diagram

Primary Controller Block Diagram

Power Integrations — InnoSwitch3-EP Primary Controller Block Diagram

Secondary Controller Block Diagram

Power Integrations — InnoSwitch3-EP Secondary Controller Block Diagram


InnoSwitch3-EP Switcher IC Typical Application Schematic

Power Integrations — InnoSwitch3-EP Typical Application Schematic


Design Example: 35 W Isolated Flyback Power Supply Using 1700 V InnoSwitch3-EP INN3647C-H606

This engineering design shows a 40 VDC to 1000 VDC input, 24 V output, 35 W power supply utilizing INN3647C-H606 from Power Integrations. The kit contains the power supply specification, schematic, bill-of-materials and basic performance data.

Power Integrations — INN3647C-H606 Design Example

INN3647C-H606 Design Example


  • 40 – 1000 VDC Input
  • 40 VDC: 4.8 W
  • 100 VDC: 16 W
  • 200 VDC: 25 W
  • 300 VDC – 1000 VDC: 35 W


  • High Input Voltage for Industrial application


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