UCC2803-EP: START UP CIRCUIT USING RESISTORS

Asha C

Part Number: UCC2803-EP
Other Parts Discussed in Thread: UCC2803

Tool/software:

Hello

As per below webench start up circuit suggestion,

Input voltage ranges from 180-370V, if i consider 180V as input voltage then the current consumed by UCC2803 during start up is 0.1mA.

CVCC is rated for 35VDC. But as per 370V Input voltage and only 0.1mA start up current, We have to consider 370V as maximum rated voltage for capacitor, isnt it?

1 month ago

0 Hong Huang 1 month ago

TI__Guru 73255 points

Hi,

The capacitor voltage rating is the same as the VCC abs max, 12V with margin, so 16V is ok. VCC abs max 12V, it looks you need to add a 12V zener on to VCC to make sure VCC not over 12V.

0 Asha C 1 month ago in reply to Hong Huang

Intellectual 365 points

Hello,

But since we have very low current because of higher value resistors, zener cannot be used to clamp the voltage.

0 Hong Huang 1 month ago in reply to Asha C

TI__Guru 73255 points

Hi,

Zener can, as the clamping only when CVcc voltage is over Zener voltage so nothing to do with the resistor values.

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UCC2803-EP: START UP CIRCUIT USING RESISTORS