New Industry Products

Power Integrations’ Flyback Switcher ICs are AEC-Q100 Certified

May 12, 2021 by Gary Elinoff

The new family features 900V and 750V versions, both also capable of operating with inputs as low as 30 volts

Power Integrations’ (PI) family of flyback switcher ICs offer efficiencies of up to 90% and feature 15 mW power consumption during no-load conditions. The units combine primary and secondary controllers, along with their high-isolation feedback link, into one IC.

Image courtesy of Power Integrations
Image courtesy of Power Integrations


The Need for High Voltage Solutions

With electric vehicle battery system’s running at 800 volts and trending ever higher, the 900 volt version in particular will provide the necessary voltage margins needed now and in the future.

As described by Edward Ong, Senior Product Marketing Manager at PI, “New 400 V system designs for electric vehicles require higher operating voltages to account for fault conditions and transients. The new 900 V INN3996CQ ICs provide plenty of voltage headroom and meet the Automotive Electronics Council strict requirements for qualification ensuring safe and reliable operation in the demanding automotive application. Using a StackFET approach, the new device is suitable for 900 V and greater bus designs.” 


Available Versions

The members of the family include the 750 volt INN3977CQ and the 900 volt INN3996CQ, as defined by the breakdown voltages of their internal MOSFETS. The two ICs are capable of providing the following power outputs:

  30 volts 60 volts 400 volts 800 volts
INN3977CQ 10 watts 20 watts  30 watts 30 watts
INN3996CQ 7 watts 14 watts 20 watts 20 watts


The apparent contradiction of the 750 volt device working with an 800 volt input is explained by the use of a StackFET. This is an external MOSFET installed in a cascode configuration with the InnoSwitch 3-AQ’s internal MOSFET. The technique is described in detail on page 10 of the datasheet, and elsewhere in PI’s extensive documentation. 

The StackFET modus is also possible with the INN3996CQ, extending that device’s capability beyond 900 volts, as suggested by Mr Ong.


A Secondary Side Feedback Solution

The InnoSwitch 3-AQ consists of a primary and a secondary side. The primary controller operates in continuous conduction mode (CCM), boundary mode (CrM) and discontinuous conduction mode (DCM). 


A typical Application for the InnoSwitch3-AQ. Image courtesy of the Power Integrations Datasheet
A typical Application for the InnoSwitch3-AQ. Image courtesy of the Power Integrations Datasheet


The secondary side controls the primary side. This configuration allows the output Schottky diode to be replaced with a synchronous rectifier FET (SR FET in the diagram), significantly increasing efficiency.



FluxLink is a magneto (magnetic) based coupling between two loops built into the ICs leadframe; one on the primary side and one on the secondary side. This allows InnoSwitch 3-AQ to avoid the use of optocouplers, which are disliked by automakers. There is 0.4 mm between the loops, and it is 4.5 kV hi-pot tested.



The new devices are aimed automotive standby, auxiliary and bias power supplies used in:

  • DC/DC converters
  • Traction inverters
  • On-board chargers



  • Available in a 13.43 (including gull wings) by 9.40 mm InSOP-24D Package. 


Regulatory and Safety

  • Isolation voltage greater than 4 kV
  • UL1577 compliant
  • TUV EN60950 in process
  • Noise an immunity class “A” for EN61000 suite


Environmental Green Package

  • Halogen free
  • RoHS compliant