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LYTswitch 6 setup questions

Posted by: treez on Thu, 07/16/2020

LYTSwitch 6
Can I put a FET at the primary to give it a 900V rating ? (as diagram attached)
Page 3 of the datasheet says it operates in QR mode, or CCM mode. Presumably then, there must be a maximum OFF time, after which the primary FET turns on whether or not the secondary inductor has fully discharged?

Page 4 states that the Primary current peak threshold increases as the load increases. Please explain how that happens, because there is no error amplifier in LYTswitch, so how does it know what the load level is?

Can we manually adjust the peak current limit level, in order to do dimming of a LED load.?


Submitted by PI-Bombadil on Mon, 07/20/2020

Hello Treez,

Thank you for considering Power Integrations in your design. Regarding the diagram, unfortunately, I cannot view it. Can you kindly resend it again?

LYT6 can operate in DCM, QR, and CCM mode. And it can change on a cycle per cycle basis in order to deliver the required load. The control of LYT6 employs a variable Frequency and Primary Peak Current scheme. As load increases, the control determines that higher frequency and current limit is needed so it would change operation accordingly.

For the dimming, since LYT6 is highly integrated device (FET, sensing, and controls), primary current limit cannot be overridden as it is inside the IC. There is however an external circuitry that can be used for dimming applications. Have you checked the various Design examples (DERs) for LYT6 that matches your target application?


Submitted by treez on Tue, 07/21/2020

Thankyou for your i attach the image of the 900V FET which we wish to use to give the higher voltage rating to the LYT6. Is this OK?

Attachment Size
LYT6_plus_FET.pdf 76.48 KB
Submitted by PI-Bombadil on Tue, 07/21/2020

Hi Treez,

I believe this configuration might have some problems starting up. For the LYT6 to startup, initial power to the controller inside is obtained via the drain pin. Inserting a FET in between this way may prevent current from going into the controller.

How much power is your application? And what is your expected voltage stress? LYT6 (LYT6078, LYT6079, and LYT6070) has a GaN version that can withstand up to 750V stress. Will this be good in your application?