# single phase inverter

Discussion in 'Homework Help' started by diya khan, Mar 11, 2012.

1. ### diya khan Thread Starter New Member

Nov 29, 2010
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Hi,

For a single phase inverter circuit,is it true that the Vgs of High side is always greater than the low side Vgs? is yes then why!!

Thank You

2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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what has single phase inverters got to do with high side and low side mosfet driving in the first place ?

3. ### diya khan Thread Starter New Member

Nov 29, 2010
18
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doesnt a full bridge single phase inverter have two legs, each leg consists of two power devices (MOSFET/IGBT) connect in series??

by saying high side, i meant the source is not low but "high" or above ground.

4. ### diya khan Thread Starter New Member

Nov 29, 2010
18
0
doesnt a full bridge single phase inverter have two legs, each leg consists of two power devices (MOSFET/IGBT) connect in series??

by saying high side, i meant the source is not low but "high" or above ground.

5. ### R!f@@ AAC Fanatic!

Apr 2, 2009
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Do u know what you are talking about?

6. ### praondevou AAC Fanatic!

Jul 9, 2011
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Vgs of the high side switch is in general the same as Vgs of the low side switch.

Please post a diagram or the source of information you are referring to.

Jan 4, 2011
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I think he is referring to Vg referenced to ground. It is higher because you need Vgs to be 10V so you need Vg to be the load voltage plus 10 volts.

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8. ### shortbus AAC Fanatic!

Sep 30, 2009
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But it still is only 10V to the gate. This is what a high side gate driver does. The bootstrap capacitor forms an isolation barrier from the source voltage, while still putting 10V to the gate.

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9. ### RRITESH KAKKAR Senior Member

Jun 29, 2010
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I think he is talking about a MOSFET with common drain..

10. ### diya khan Thread Starter New Member

Nov 29, 2010
18
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I mean to ask Vgs applied to g1 should be higher than Vgs applied to g4? because for g4 mosfet, source is connected to ground, but for g1 mosfet, source is floating.

am i wrong?

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11. ### praondevou AAC Fanatic!

Jul 9, 2011
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"Vgs" means the voltage from the gate to the source of the SAME MOSFET.

Of course, if you measure to ground, Vg of the upper switch will be higher than that of the lower switch, depending on the bus voltage.

It is however usually never done like this.

The upper switch's source terminal is not floating with respect to the MOSFET driver's output, the one that provides the Vgs.