300 VAC will violate the Vds(st) specification without special prequirements.it will sure support 300V AC
viper ic is not desgined to handle 20 to 300vac
you can desgin it only for 180vac 280vac for satisfactory operation.
in no way any such pwm controller will operate in 40vac
Here this Viper 22A is working with 40 V AC but that time i cant use 300V AC that time maximum of voltage range is 40-240,after this range the device will go to over voltage protection. So i want to maintain the VDD voltage under the over voltage condition of viper22(38V) how it will achieve in design.can you give some tips on that.
The Viper 22A will not turn on until VDS > 100 V. With VDS < 100 V it will not charge Vdd capacitor. Figure 10 https://www.st.com/web/en/resource/technical/document/datasheet/CD00087939.pdf
You may be able to operate at 40 VAC if you start-up at 100 V and then you decrease.
Regarding Vdd varying voltage there should be some design problem... Are you using the transformer auxiliary winding for Vdd supply? With which turns ratio? Wich diode are you using in D3 and C5 of Figure 4? https://www.st.com/web/en/resource/technical/document/datasheet/CD00087939.pdf
I would suggest using the eDesignSuite in he ST website to design the circuit components according to your needs.
I don't see anything in the datasheet that defines a clear value for the minimum Vdrain required for startup. That figure just states that the test condition is with 100V<Vdrain<400V. Operation with Vdrain<100V isn't specified, apparently.The Viper 22A will not turn on until VDS > 100 V. With VDS < 100 V it will not charge Vdd capacitor. Figure 10 https://www.st.com/web/en/resource/technical/document/datasheet/CD00087939.pdf
You may be able to operate at 40 VAC if you start-up at 100 V and then you decrease.
That's the absolute max range of Vds, not the operating range...In data sheet VDS start up voltage has mentioned as -0.3-400 so it should work at 40V AC range.
I don't see anything in the datasheet that defines a clear value for the minimum Vdrain required for startup. That figure just states that the test condition is with 100V<Vdrain<400V. Operation with Vdrain<100V isn't specified, apparently.
That's the absolute max range of Vds, not the operating range...
Again, the datasheet doesn't clearly say what happens under 100V, it might still work but maybe the startup current is decreased or something. If it turns out it doesn't start up with Vds<100V, then you'll either have to use an external startup circuit or another controller.
If it turns out it doesn't start up with Vds<100V, then you'll either have to use an external startup circuit or another controller.
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