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TOPSwitch-HX - How to find mode of operation?

Posted by: Harel Levy on 12/29/2021

Hello everyone,

I have a question regarding the mode of operation of the TOPSwitch-HX family, specificly the TOP255YN.

Flyback topology with 370V DC Input, aux. control scheme, X'mer inductance of 300uH and output power of 31W, how can I determine ahead of time the mode of operation?

Modes of Operations:

1. Full Frequency PWM mode

2. Variable Frequency PWM mode

3. Low Frequency PWM mode

4. Multi-Cycle-Modulation mode


If you guys need anything more just let me know and ill provide any informations necessary.


Submitted by PI-csbabu on 01/12/2022

Hi Levy,

        Thank you for choosing TOPswitch for your product.  In your application, Input voltage is high and output power low, you can operate in DCM mode of operation at full load. I recommend to use PIexpert online tool to design transformer and keep KP>1 to operate unit in DCM mode. In a given TOPswitch design,  operates in different modes ( Full frequency, variable frequency, Low frequency and multi-cycle mode) based on applied load and input voltage to maximize efficiency. Please check TOP-switch datasheet ( Page.9), pulse width modulator section for more details.