Inferno

hello there...
i have a question about another h-bridge design..
i m using the N-channel power mosfet IRF540(http://pdf1.alldatasheet.com/datashe.../datasheet.pdf) with the half-bridge driver IR2111 (http://pdf1.alldatasheet.com/datashe...heet.pdf)....i know how to connect the mosfets... but i m not sure about the driver connections....

1)i see that the driver has one logical input....and 2 outputs for the mosfets... i want to know... when the high output is on... the low output will be on or off ???

2)if i want the mosfets to drive a 12V small turbine...what is the Vcc needed on the driver ???? ( by the way what are the cc in the Vcc )

3)in an example circuit for the driver.. i saw them putting 2 resistors between the mosfets and the highside and low side outputs...what are the resistors for ?? and what resistros should i use ??

4)what is the Vs output in the driver?? and why should it be connected to the load ??

Norlin

Stolen from elsewhere:

Vcc - Voltage Collector Collector
Vdd - Voltage Drain Drain
Vee - Voltage Emitter Emitter
Vss - Voltage Source Source

Vcc -- For TTL circuitry, this is the +5 volts which sits on the collector of the bi-polar transistor output circuit.
Vee -- For TTL circuitry, this is the GND which sits on the emitter of a bi-polar transistor output circuit.
Vdd -- For CMOS circuitry (like the PIC) this is the +5 (or +3) voltage that sits on the 'drain' of a MOS-FET transistor output circuit.
Vss -- For CMOS circuitry, this is the GND that sits on the 'source' of a MOS-FET transistor output circuit.

Positive voltages:
Vcc- Positive supply voltage of a Bipolar Junction Transistor.
Vdd- Positive supply voltage of A Field Effect Transistor

Negative voltages/ground:
Vee- Negative supply voltage of a Bipolar Junction Transistor.
Vss- Negative supply voltage of A Field Effect Transistor.

Russlk

1. When the high mosfet is on the low mosfet is off.
2. Vcc has to high enough to turn the IRF540 on. The gate drive should be +10 volts, so +12 volts VCC minimum.
3. The resistors are a low value, like 10 ohms. I am not sure of the purpose, but the resistors limit the peak current to the gate and slows the turn-on.
4. Vs is connected to the source of the upper mosfet in order that the driver can drive the gate relative to the source. Also, the capacitor from Vs to Vb is necessary to bootstrap the gate supply voltage. The capacitance must be several times larger than the gate capacitance of the mosfet.

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Inferno

thank you guys....
your answers are more then clear and more then enough for me ....
really thanks

Inferno

i was wondering.....
is it possible to driver the turbine directly from two half bridges ?? they say in the driver datasheet that the ic could handle 200-420 mA...that would be more then enough for the small turbine ...
but if possible what would be the tension on the turbine ?

speakerguy79

FET drivers aren't really meant for driving current continuously, they are meant to overcome the gate capacitance of the device. If you are continuously sourcing/sinking a few hundred mA out of a DIP it's not going to be good.

The resistors in there are very low value like said before, they are just there to limit peak current in the case of a huge gate capacitance or something. They will slow down the FET turning on a little but not an issue if you are at low frequencies.

I use the L6384 half bridge driver and it is a very nice part. It does not need the resistors or the external diode. Read its data sheet or the data sheet for your part and it will tell you the basic way to calculate the value for a bootstrap capacitor. If all else fails just throw a 1uF ceramic in there and it should work.

Inferno

ok.. i ll try looking for this chip.....the problem is that i can t find everything here...

speakerguy79

Oh sorry, didn't see the location. USians have it way too easy when it comes to parts. The part you have will work fine too, so don't worry too much about it.

Inferno

hello there..
i tried the bridge.. and it didn't work... i m not sure what the problem is..
but the Ic caused a very high tension drop....i m using a big 12 volts battery .. and the tension on the IC is just 4 volts !!! is that normal ?? what the problem could be ???

speakerguy79

By tension do you mean voltage?

Inferno

yes... i m measuring the voltage between vcc and ground and it s just 4 volts ....and the bridge is not working .. what could the problem be ?

audioguru

The 12V battery is supposed to connect to Vcc and ground. Since you measure 4V then the battery is dead.

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Uncle $crooge

Inferno

no it s not that ....
look what s happening !
i connected the two capacities and the diode .... i didn t connect the mosfets ...
vcc and groud are to the 12 v battery ....
i m measuring the hight and low outputs...
the low is 0v .... and the hight is 6.2 volts..
when i connect the In pin to the 5 volts.... nothing change ....the low is 0 and the high is 6.2....
what to do ?

audioguru

Are you trying to drive the motor with the Mosfets driver IC?
The Mosfet driver IC is not strong enough to drive a motor by itself. It is designed to drive Mosfets that drive the motor.

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Uncle $crooge

Inferno

no...
i m using irf540 mosfets...
but the bridge didn t work ..
so i was checking the ic
the results i gave ... are when i tested the ic wihout connection the mosfet or the motor... just the output of the mosfet