Sonsivri

hi

what is the purpose of Anti-Parallel Diode in igbt and mosfet ?
what is meaning of switching SOA capability in IGBT ???
 ??? ???

Diode:  Handles current forced by inductive loads at turnoff time.

SOA Safe Operating Area.  Voltage / Current allowable maximums for safe power dissipation.

Hi,
In igbt and mosfet, Anti-Parallel Diode acts as freewheeling diode. In addition to that, some Indian and Bangladeshi IPS and UPS manufacturers use those as Rectifier Diodes for  charging of Battery, which is not recommended. I also use those as Rectifier Diodes in my IPS design.
The SOA is the safe operating area, within which the IGBT can be safely used. I think it is like, a MOSFET has a threshold voltage of ~2.5v, but to operate it in its SOA, you need to drive it above 8v and charge and discharge the gate relatively quickly, also maintaining a good square wave at the input. Around 4-5v, you may be operating it in the linear region, and end up heating the MOSFET.

hi


how to use freewheeling diode( anti parallel diode )for battery charging purpose in ups. please provide  the any application notes or example circuits

Thankyou

Hi,
I don't have any application notes on this subject but I have example circuit, which I hope to provide soon.
When I first tried to use the internal freewheeling diodes for rectification purpose for battery charging,I burned out few mosfets. Then I collected a prototype from a local manufacturer, studied the circuit and made one for me. The secret is that while using the freewheeling diodes as rectifier, the mosfet gates have to be shut forcefully,so that gates are not fired ( open) in any circumstances either for miller capacitance or any other reasons.
Hope, this will help.

search for full bridge mosfet converter. and see how to charge implement.

hi


i cannot see in search results..??? please  provide the any links.....?

just short the gate and source of a mosfet or IGBT together and you are effectively left with nothing but the freewheeling diode.  Not sure why you couldn't find a suitable discrete diode rather than wasting a perfectly good IGBT...

use primary side ac control (zero crossing topology)

Hi,
While using the freewheeling diodes for rectification purpose in battery charging in ips/ups, the gate and source of mosfet or igbt cannot be shorted permanently as one has to use those mosfets/igbts in inverter mode and only using those freewheel diodes while charging the battery instead of using additional diodes. For that, the mosfet/igbt  gates have to be shut forcefully,so that gates are not fired ( open) in any circumstances either for miller capacitance or any other reasons and that should be done temporarily while in charging mode only.Hope, I could make it clear what I intended to mean.