Negative voltage needed on IGBT gate ?

[andrelux]

Hi All,

I am designing a 3 kW power charger with a classic architecture
230 AC mains -> rectifier +caps -> IGBT full bridge -> HF trafo -> Output Bridge -> Filter

I will use 4 HCPL 3120 opto drivers (2.5 A peak) to drive each of the STGE50NC60VD igbt's
Frequency on the gate switch is 20 KHz and total gate charge is 214 nC.

My question is relevant to the gate driver. On a theoretical point of view, I should use +15v -5 V as gate level voltage.
I want to use 4 small standard DC/DC 3 watts converters and they are available in +/- 15 V only.

What could happen if I use +/-15 volts instead of +15/-5 V ?
I have checked the datasheet of the switch and they accept +/- 20 V as Vge.

I have also seen some IGBT applications where negative voltage is not needed for turning off the device.
Should I use +15 volts only ?

Thanks for helping

 

[ALERTLINKS]

It works without -neg volts which help for fast switching off the switch with additional stress to diver. At low frequency such as 20KHz, you can do without -neg voltage if driver properly designed.

 

[andrelux]

if driver properly designed.

What do you think of this driver design ?
Notes:
All DC/DC converters are 3W +15/-15 volts
Theoretically, I could use 3 instead of 4 (1 converter for the 2 low side switches) but I will stick to 4.