single phase igbt inverter with driver

[nareshgtr]

igbt gate driver

Hi guys,
I am designing IGBT driver. How to select the current rating of Gate driver for particular IGBT. What is the criteria. What is the criteria for selecting fast switching diodes across the IGBT Driver. I want use the SGP23N60UFD in 3-phase Half Bridge design. Please give me suggestions to select the suitable driver for 3-phase Half Bridge.
Thanks advance
V. Naresh Kumar

 

[eem2am]

igbt driver schematic

what is switch freq.

get igbt datasheet.
it tells you the total gate capacitance.

you know how fact you want the gate voltage to rise.....just work out using i = c dv/dt

the igbt datasheet may say what current driver it needs to come on.

for hi side what about HCPLXXXX ...but it depend on your frequency...above 10KHz you cannot use opto driver.

 

[hock]

igbt gate drive circuit

this may be useful. from some seminar i had attended.
hock

 

[Mr.Cool]

igbt gate resistor

get your IGBT datasheet and look at the gate capacitance. be careful that you do not get gate CHARGE. you can tell which you are given in the datasheet by looking at the units of measure. the capacitance is measured in farads [F].

if you get charge as the unit, then we will work together to figure it out properly.

then look at your datasheet and see the recommended gate resistance value, sometimes there are two, Ron and Roff. you can tell beacuse each datasheet parameter has given test conditions, and one of the conditions it says what the gate resistance is.

your gate driver has 3 critical requirements:

1) what is the peak current it takes to charge the gate capacitance of your IGBT? this is determined by taking your applied gate voltage (15V typical) and dividing it by your gate resistor. your circuit must be able to supply this much current in a VERY short period of time.. so large caps with stored energy are used with wide PCB tracks (copper pours), close distance to your IGBT and proper layout thought because this is a high di/dt scenario. here is the reason why your gate resistor needs to be NON-INDUCTIVE type.

2) what is your desired switching frequency? the higher this value the more power dissipation your circuit will have and the more critical your component selection. 20kHz is do-able without any deep thought. higher values takes more care.

3) what is the AVERAGE power to switch your IGBT? this is the energy it takes to charge your gate capacitance multiplied by switching frequency. Pavg = CV^2*f (not 1/2 because you both charge and discharge this circuit). the voltage is the applied voltage, so if you turn ON at +15V and turn OFF at -10V, then V = 25V.

the vast majority of this average power is dissipated in your gate resistors.. so they better be able to handle the power.

then you might think... gee... i'll just put a heatsink on my gate resistor. well, this is OK if your are dealing with just small IGBT and small power.. but 100kW drives and such have very high di/dt and you can not afford the parasitic capacitance between your gate drive board & heatsink. so there is NO PHYSICAL connection between your gate drive board and the system heatsink.. now how will you cool your gate resistors? you must size them for convenction cooling only, and probably need to get 175C rated junction temperature type resistors.

and we only just begun.

of course, if this is just a hobby project you are speaking about you can forget about the above, and just flip open an appnote and plug & play with no thought. easy to do and quick results of something that basically works.

Mr.Cool

 

[nareshgtr]

igbt gate driver design

thanks hock and Mr.Cool

Added after 1 hours 29 minutes:

please any body throw the light on how to select the fast switching diodes across the driver......

 

[FvM]

igbt gate drivers

please any body throw the light on how to select the fast switching diodes across the driver......

I doubt, they are required. You have diodes for particular purposes, e.g. H.V. diodes for desaturation detection circuits.

 

[nareshgtr]

gate driver design

thanks FVM, Please some body explain about what is dv/dt, di/dt and "shoot through" in IGBT/MOSFET. How to calculate these values.
Regards
V. Naresh Kumar

 

[Mr.Cool]

igbt gate voltage

nareshgtr, i am not sure what you mean about fast switching diode across the DRIVER. did you mean, across the IGBT?

definition:

dV/dt = rate of change of voltage

dI/dt = rate of change of current

shoot-through = when two adjacent IGBTs conduct at the same time effectivly shorting out the DC link capacitor

now, can you figure out the significant of the above definitions? see if you can learn, self teach. post your answer & we will discuss.

Mr.Cool

 

[nareshgtr]

igbt gate drive

Dear Mr. Cool, thanks for your information. For fast switching diodes I am attaching IGBT BRIDGE Driver schematic, Please find in the attachment. I collected this from Freescale Semiconductor website.
Please explain why designer selected following diodes in the document
1. D200, D207 and D212 are MURS130LT3.
2. D201, D203, D206, D209, D211 and D214 are MBRS130LT3
3. How to calculate Gate resistor.
Regards
V. Naresh Kumar

 

[nareshgtr]

igbt driver design

I am thinking dv/dt in my application
dv/dt = ((DC Bus voltage/IGBT turn on time) -- For turn-on
dv/dt = (DC Bus voltage/IGBT turn off time) -- For turn-off
di/dt = (Output current/IGBT turn on time) -- For turn-on
di/dt = (Output current/IGBT turn off time) -- For turn-off
Which one I should consider...either turn-on or turn-off

 

[FvM]

gate resistor igbt

Please explain why designer selected following diodes in the document

Using 1A schottky diodes in these places isn't absolutely necessary to my opinion, but is basically O.K. The diodes are bootstrap diodes respectively shorts for the gate resistors to achieve asymmetric drive, somewhat unusual in the present form.

 

[nareshgtr]

igbt gate charge

I am thinking these diodes are using to by pass the 75ohm resistors in discharging period. I am not getting motive behind this.

 

[FvM]

what you mean by igbt

It's not unusual to make the gate drive asymmetrical. IR2133 has already asymetrical current limit, as you can see from the datasheet. One reason to have a lower impedance discharge path is to keep the IGBT safely off while Vce rises.

 

[chatwitdebo]

how to design an igbt drive

Hi everyone,
could anyone please recommend an IGBT to me, which does not require a negative gate voltage to turn off. if not, please could you help with a circuit showing how to easily supply +15V to the Vcc of my optocoupler and -10V to the Vee, from the same source.
thanks

 

[FvM]

igbt power dissipation calculation

No IGBT doesn't necessarily require a negative gate voltage. Low cost designs, e.g, for household appliances are often using single supply. But reduced switching performance must be expected. Also the driver impedance must be considerably lower to keep the IGBT from turning on during positive Vce transients.

 

[chatwitdebo]

igbt gate

thank Fvm,
i am trying to design a buck chopper, so i think i require a good switching performance. please could you help with such a circuit, especially supplying both the negative and positive from the same source.

 

[hakeen]

igbt bootstrap resistor circuit capacitance dv dt

Hi Chatwitdebo

You can simply use center tapped transformer, where tap is GND. Each side is positive and negative voltage supply.

regards

 

[FvM]

igbt schematic

You didn't tell, what's your existing supply source. Typically, a bipolar DC/DC converter would be used for an insulated gate driver. The design depends on required insulation voltage, driver power demand, primary supply voltage.

 

[Mr.Cool]

igbt gate current

i give up