Infineon CCM PFC products: Frequently asked questions – KBA236234
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Sep 23, 2022
06:17 AM
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Sep 23, 2022
06:17 AM
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- Is the ISENSE pin current limited by both RCS + opamp input resistance in ICE3PCS01G PFC IC? If yes, what is the value of the opamp internal input resistance highlighted in the attached figure? Explain with an example of 40A allowable start-up inrush current what will be the ISENSE current.
- Yes. In the ICE3PCS01G PFC IC, the ISENSE pin current is limited by both RCS + opamp input resistance. The value of opamp internal input resistance is 7kΩ. This resistor inside the IC that is connected in series with the ISENSE pin is large enough to limit the ISENSE current so that the inrush current during startup will be within the -1 mA – 1 mA range.
See the following example to allow maximum 40A inrush current during start-up.
The selected Rshunt value is 3 mΩ.
The voltage across the Rshunt is Vshunt = IINRUSH × Rshunt = 0.12 V
The current at the ISENSE pin = Vshunt/RCS + opamp = 17 µA, which is within the limit as specified in the datasheet.
- What are the possible solutions to reduce higher noise in power factor correction (PFC) choke?
Use a capacitor not more than 10nF at the ISENSE pin.
Improve the PCB layout such that the ICOMP capacitor GND does not share any path with another signal, but has a direct path to the IC GND pin.
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