Will the bleed resistors enable a shorter path to ground or not?

  • Thread starter checkmatescott
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In summary, the P-channel and N-channel FETs are connected in a square and the gates of each are connected together. The P-channel FETs are at the bottom of the square and the N-channel FETs are at the top of the square. The P-channel FETs are connected to the gates of the N-channel FETs and the N-channel FETs are connected to the gates of the P-channel FETs. The supply voltage is 55V and there is a 10kohm resistor between the gates of the P-channel FETs and the sources of the N-channel FETs. There is a T1 and T2 transistor and
  • #1
checkmatescott
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ok without ai quote here goes.
i want to build an h-bridge I have two P-channel IRF9630 and two N-channel IRF630 mosfets laid out in a square. the two N-channel mosfets are at the bottom of the square and the two P-channel mosfets to form the top of the square.

the lower left is the first N-channel mosfet and is labelled Q1, and the top left is the first P-channel mosfet and is labelled Q2, this is the left side. the bottom right is the second N-channel mosfet is labelled Q3 and the top right P-channel mosfet is labelled Q4, this is the right side, there is a 55v vcc.

The gates of the left side are connected via a 10kohm resistor, the gates on the right side are connected via a 10kohm resistor. on the left side, the node which connects to Q2 to the resistor that goes to Q1, the node has a bleed resistor going to source and is called a gate to source bleed resistor and is 10kohm. also on the left side Q1 gate is connected to its source via 10kohm bleed resistor. on the right side, the node which connects to Q4 to the resistor that goes to Q3, the node has a bleed resistor going to source and is called a gate to source bleed resistor and is also 10kohm.

At the node on the left side (where the gate connects to the gate on Q2 through the resistor to Q1, and the bleed resistor that goes to vcc) there is also a bleed resistor 10kohm from Q3 gate to its source. There is a transistor T1 and the collector of that transistor goes to the gate of Q2. the emitter of T1 goes to ground and then the base connects through a 2.2kohm to the digital pin of an arduino (pin 2). At the mirrored node on the right side (which connects to the gates of Q4 to Q3 through the 10kohm resistor and said node is connected to the gate of Q4 goes through the bleed resistor of 10kohm to vcc) there is a transistor T2 and the collector of that transistor goes to the gate of Q4, the emitter of T2 goes to ground and then the base connects through a 2.2kohm to the digital pin of an arduino (pin 3)

Pin 2 and 3 toggle high and low and 50hz to produce an alternating current the drains on the left side are connected and the drains on the right side are connected, between these lines i will be putting a transformer and the current will alternate though the winding exciting the winding at 50hz the sources of the N-channel mosfets will be connected to ground. the sources of the P-channel will be connected to vcc. T1 and T2 are 2n2222 npn transistors.

Okay now i want to know do I have to have a vgs of less than 16 to protect Q2 and Q4 from going over the rated 20 gate to source voltage and I want to do it by voltage divider and zener the zener's I have an assortment of zeners and resistors do you understand P-channel source goes to positive vcc and the N-channel sources goes to ground again the mosfets gates are connected to the collectors of the transistors and the transistors are controlled by arduino.

I hope you can understand and get me a speedy reply i want to know before friday next week? thanks
 

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  • #2
When InpA is low, Q5=T1? is off,
then both Q1 and Q2 are on,
because 10k+10k splits the 12V supply.
 
  • #3
Q1&3 must never be on at the same time which means the gates cannot be ganged together. Same for Q2&4. Quad Nch FETs are preferred to create a dead time using identical FETs in the range of 1 us.

With Miller Capacitance, and you want to try this out, what do you think would be a better?

- a 40V zener between the P-N gates
- or ~16V Zeners across each Vgs. with a current limiter in between.

Bring up the supply voltage slowly and sense Temp. on the forced air heatsink.
 
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  • #4
Your schematic is simple, which is great for a basic description of this common topology, thank you! But in real life these circuits are much more complex. I think you need to study this a bit more to be successful.

My advice is to go to the big PMIC manufacturers and buy a control chip and, as much as make sense, copy their application examples.

Here's one that I chose quickly mostly at random. IDK if it will work in your system, but something similar will. They cost about $2 each, for which you'll get a lot of great engineering development. In any case, read the documentation to see what features they think are important.
 
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  • #5
is it allowed to reference a youtube link? thanks
 
  • #6
Baluncore said:
When InpA is low, Q5=T1? is off,
then both Q1 and Q2 are on,
because 10k+10k splits the 12V supply.
yes i have labled Q5 as T1 to standing for transistor 1 did you look at both pictures when inpA is low Q1 is on and Q2 is of i want to toggle the inputs from high to low at 50hz to make and alternating current. the drains of Q1 and Q2are connected directly and also the drains of Q3 and Q4 are connected directly and between these two lines will be the transformer also the vcc voltage is 55v
 
  • #7
Baluncore said:
When InpA is low, Q5=T1? is off,
then both Q1 and Q2 are on,
because 10k+10k splits the 12V supply.
when inpA is low then Q1 is on Q2 is off so when inpB is high Q3 is on and Q4 is off from my understanding in this configuration you cannot burn out any of the mosfets, but something just doesnt seem to make sence it looks as though the electric current would take the shortest path to ground (through the bleed resistors) can i give the link the video for youtube where i got this information? also i made a mistake in my initial post the gates are not connected though 10kohm resistors they are connected directly both on side A and side B.

ok without ai quote here goes.
i want to build an h-bridge I have two P-channel IRF9630 and two N-channel IRF630 mosfets laid out in a square. the two N-channel mosfets are at the bottom of the square and the two P-channel mosfets to form the top of the square.

the lower left is the first N-channel mosfet and is labelled Q1, and the top left is the first P-channel mosfet and is labelled Q2, this is the left side. the bottom right is the second N-channel mosfet is labelled Q3 and the top right P-channel mosfet is labelled Q4, this is the right side, there is a 55v vcc.

The gates of the left side are connected, the gates on the right side are connected. on the left side, the node which connects to Q2 gate to Q1 gate, the node has a bleed resistor going to source and is called a gate to source bleed resistor and is 10kohm to vcc. also on the left side Q1 gate is connected to its source via 10kohm bleed resistor which is GND. on the right side, the node which connects to Q4 to the gate of Q3, the node has a bleed resistor going to source and is called a gate to source bleed resistor and is also 10kohm and goes to vcc. also from the same node (the gate of Q3 there is a 10kohm bleed resistor from the gate to its source that goes to GND

At the node on the left side (where the gates of Q2 and Q1 are connected and the bleed resistor that goes to vcc) There is a transistor T1 and the collector of that transistor goes to the gate of Q2. the emitter of T1 goes to ground and then the base connects through a 2.2kohm to the digital pin of an arduino (pin 2). At the mirrored node on the right side (which connects to the gates of Q4 to Q3) and said node is connected to the gate of Q4 there is a transistor T2 and the collector of that transistor goes to the gate of Q4, the emitter of T2 goes to ground and then the base connects through a 2.2kohm to the digital pin of an arduino (pin 3)

Pin 2 and 3 toggle high and low and 50hz to produce an alternating current the drains on the left side are connected and the drains on the right side are connected, between these lines i will be putting a transformer and the current will alternate though the winding exciting the winding at 50hz the sources of the N-channel mosfets will be connected to ground. the sources of the P-channel will be connected to vcc. T1 and T2 are 2n2222 npn transistors.

Okay now i want to know do I have to have a vgs of less than 16 to protect the mosfets, they are rated Q2 and Q4 from going over the rated 20 gate to source voltage and I want to do it by voltage divider and zener the zener's I have an assortment of zeners and resistors do you understand P-channel source goes to positive vcc and the N-channel sources goes to ground again the mosfets gates are connected to the collectors of the transistors and the transistors are controlled by arduino.

i hope this ammendment makes sense thanks, if it doesnt let me know appreciate all your help guys
 

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  • #8
That schematic from a youtube video has this major design fault.

Q1&3 must never be on at the same time which means the gates cannot be ganged together for large Vdd. This only works on low-voltage logic.

Pch and Nch FETs on each side go through a transition where both have Vgs >> Vgs(th) {=1.0Vmin} x 250%. This is sufficient to force low RdsOn and massive shoot-through currents with Vdd > 10V.


A Google search on your schematic image reveals the same answer.

https://forum.arduino.cc/t/various-h-bridge-designs/376460/5The theory behind some successful commercial designs lies in isolated high (HO) and low (LO) output gate drives that use asymmetry in the design of propagation delays to make the Toff much faster than the Ton for gate control resulting in a "dead-time" when both FETS on one side are OFF.

This results in a back EMF of V=LdI/dt into some output and stray capacitance (Tau =RC) so that flyback voltage current must be diverted to some fast recovery clamp.

As @DaveE correctly points out, this is performed well in "modern" Half-Bridge IC's but "only" in SMT (aka SMD), which may be beyond your urgent requirements. There are less efficient older technology examples in THT but this strays from your question.
 
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  • #9
thanks for reply.
what I am trying to achieve is to alternate the dc current of 55v at 50hz with use of and arduino to generate ac current and put through a transformer to achieve 230v can you (if you have the time) create a circuit that would suit my needs thank you so much for your input
 
  • #10
checkmatescott said:
thanks for reply.
what I am trying to achieve is to alternate the dc current of 55v at 50hz with use of and arduino to generate ac current and put through a transformer to achieve 230v can you (if you have the time) create a circuit that would suit my needs thank you so much for your input
I am not allowed to create a design for you. I pointed out one of many fundamental theories, but it's up to you to find a commercial solution that works until you can understand the design details.

Buying an inverter for AC or PWM FET ESC for a DC motor is perhaps the best way to analyze and learn design if you have the analytic toolset and skill after you learn to specify the requirements. Preferably you will use a BLDC Motor and by the way, all motors draw about 10x the rated current on full start and 20x on full reverse unless PWM acceleration is limited. (V+/coil DCR)
 
  • #11
ok sorry for being dumb i appreciate your answers are there any cicuits that i should look at or could you explain in detail what is meant by FET EMC or talk about the "theory" some more and ellaborate on the "commercial solutions" or where to start looking any extra pointers at all. I want to understand the details so to speak. any help welcomed or theories thanks
 
  • #12
also im not using a motor i want to make 50hz for a transformer
 
  • #14
ok any more references? I'm a good learner and will learn the basics
 
  • #15
checkmatescott said:
also im not using a motor i want to make 50hz for a transformer
If you are a good learner no more questions are required from what I have said. You are looking or an AC inverter design which is far beyond the complexity of this XY question but has similar low impedance no overlapping H bridge switches. If you have a better question , follow the Rules and search 1st then open a new question. To answer the original question, simply:

Will the bleed resistors enable a shorter path to ground or not?​

No. It creates a fault condition called "shoot-thru"
 
  • #16
checkmatescott said:
what I am trying to achieve is to alternate the dc current of 55v at 50hz with use of and arduino to generate ac current and put through a transformer to achieve 230v can you (if you have the time) create a circuit that would suit my needs thank you so much for your input
You have not specified how much current or power, only 55V.
You want to switch the energy through a transformer, but what then?

What you are trying to do, is well beyond your reach and experience now. If you study calculus and electronics solidly for at least one year, you might then be able to achieve it.
 
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  • #17
ok so im an inventor and have worked with electrics for over 10 year i will upload my project i have programmed an esc to work with a drone motor and have programmed an arduino to work with a speedometer on an lcd (not in this video because its old and i have progressed further adding a forth coil to the system i am familiar with calsulus dx/dy stuff intergrals and that and altough the voltage says 45 in this vid the voltage goes up with speed
 

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  • #18
and a few more
 

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  • #19
and a few more
 

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  • #20
im going to run it up tomorrow when my batteries have charged and measure its max output and measure the current draw ohms law says v=IxR and power in V*I my power resistor is rated 100watt and its value is 27ohm so to get the watts below 100 i need to set the wheel to out put 50v divide that by 27ohm which gives a current of 1.85 amps the lower the resistor value the higher the amps simple
 
  • #21
checkmatescott said:
... i have programmed an esc to work with a drone motor ...
What is an esc ?

How are the pictures relevant ?
You know what the pictures are. I don't have a clue.
 
  • #22
ok esc is an electronic speed controller and i programmed an arduino uno (wrapped in tape with leds on it to make the drone motor spin and its speed is controlled by a potentiomer in picture dsc00323 the silver and gold motor is the drone motor the esc is the thing that connects the motor to the arduino and is yellow and has a little silver sticker with 3 blue wire going to the drone motor picure dsc00332 shows that 42.7v is being generated when at full speed makes 57v this is the dc voltage I want to oscillate to 50hz and i was going to use the H-Bridge to do it, and other questions about it id be happy to answer
 
  • #23
But why ?
What does it all achieve in the end ?
 
  • #24
I want the stable 55v that it produces at a certain speed, and turn it to 55v ac, with the use of circuitry, and put through my step up transformer to 230v ac on the output of the transformer the aim is to make an oven fan motor thats 15watt and 230v 50hz and i want it to spin at full capacity that is all
 
  • #25
perhaps you could tell me where to buy a dc to ac inverter that handles 55v in
 
  • #26
also i was wondering how did you search the web for an image, i though that was cool?
 
  • #27
is there a format of video that the site lets me upload so you can get a better understanding
 
  • #28
just to clarify i want an inverter that has 55v in to it and all i can find on the internet is to make 12v dc to ac current i need 55
 
  • #29
after all that i found a solution for my needs!!! thanks for the answers, cheers
Scott
 

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  • #30
checkmatescott said:
perhaps you could tell me where to buy a dc to ac inverter that handles 55v in
An Uninterruptible Power Supply, UPS, that has a 48 volt battery bank could be modified to do that job.

The only source of energy seems to be the drone motor. I have my doubts about the efficiency of the generator that produces 55 volts. You need to check if it can supply sufficient power to turn the oven fan, without the voltage falling too far.
 
  • #31
checkmatescott said:
after all that i found a solution for my needs!!! thanks for the answers, cheers
Scott

Your high side transistors will likely be damaged as they will have 38V (50V - 12V) to 50V across the gate and source. The absolute maximum is 20V. Even if they survive they will never turn off as they need less than 2V to do that.

You need to find some high side gate drivers for them. Many high side gate drivers are designed to drive N-Channel FETs. Make sure to either swap out the P-Chanel ones or get a driver that can drive them.

BoB
 
  • #32
will this not do, it specifys (in dc (max 60v)) also is there any way i can upload a video of the machine in motion
 

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  • #33
checkmatescott said:
will this not do, it specifys (in dc (max 60v))
No, it will not do above about 15 volts input.
I would suggest you use a pair of half-bridge drivers, with four N-channel MOSFETs. N-chan are cheaper than P-chan, have lower on-resistance, and switch faster.

checkmatescott said:
is there any way i can upload a video of the machine in motion
We have a pretty good imagination. Why do we need video?
 
  • #34
because its cool to see the black rubber wheel with the magnets on doing 600rpm you would be supprised, its a beast!
 
  • #35
did a quick search of half bridge driver on youtube there doesnt seem to be anything is it called anything else perhaps thanks again
 

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