- #61
Will the bleed resistors enable a shorter path to ground or not?
- Thread starter checkmatescott
- Start date
Click For Summary
Discussion Overview
The discussion revolves around the design and functionality of an H-bridge circuit using P-channel and N-channel MOSFETs, specifically addressing the configuration of bleed resistors and their impact on gate-source voltage (Vgs) protection for the MOSFETs. Participants explore the implications of their circuit design choices, including the use of transistors controlled by an Arduino to toggle the MOSFETs and the potential for current paths in the circuit.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant describes the layout of the H-bridge using two P-channel and two N-channel MOSFETs, detailing the connections and components involved, including bleed resistors and transistors.
- Another participant emphasizes the need to ensure that Q1 and Q3, as well as Q2 and Q4, are not on simultaneously, suggesting the use of identical FETs to create dead time.
- There is a proposal to use a 40V zener diode between the P-N gates or ~16V zeners across each Vgs with a current limiter, raising questions about the best approach for protecting the MOSFETs.
- One participant suggests that the circuit's simplicity is beneficial for understanding but warns that real-world applications may require more complexity and recommends consulting PMIC manufacturers for control chips.
- Another participant expresses uncertainty about the current path in the circuit, questioning whether the electric current would take the shortest path to ground through the bleed resistors.
- Clarifications are made regarding the toggling of inputs and the states of the MOSFETs when the input signals are low or high.
Areas of Agreement / Disagreement
Participants express differing views on the optimal configuration and protection methods for the MOSFETs, indicating that multiple competing approaches exist. The discussion remains unresolved regarding the best way to implement the circuit while ensuring the safety of the components.
Contextual Notes
Some participants mention specific voltage ratings and configurations, but there are unresolved assumptions about the behavior of the circuit under different conditions, including the impact of bleed resistors on current paths and Vgs levels.
- #62
checkmatescott
- 80
- 2
ok I have spice, does it have IC's integrated in/with the software?
- #63
checkmatescott
- 80
- 2
why skeptical?checkmatescott said:
- #64
checkmatescott
- 80
- 2
the mechanical flywheel in my case is equivalent to a low-pass-filter in electrical terms dunno if you've ever come accross maybe you might find the different analogys of some interest https://lpsa.swarthmore.edu/Analogs/ElectricalMechanicalAnalogs.html
- #65
checkmatescott
- 80
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anyway that software is EPIC, I can't thank you enough
- #66
DaveE
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Read the online instructions. Less typing, more study. In our service/support department the favorite acronym was RTFM; which BTW, you would never say to a customer.checkmatescott said:
But, yes some. IC manufacturers will often give you spice models. But that only works for people that can search the web and find answers themselves.
- #67
DaveE
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- #68
TonyStewart
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Do not trust a simple schematic unless you know the credentials of who did it. When there are specs like max 60V ask why and get component specs and examine the interface. Trustworthy designs come from TI, Analog Deices, Microchip, Hitachi, Toshiba, etc. This is just a rookie undergraduate example. Using DO NOT EXCEED (DNE) levels is not a good design practice. Use the values in the tables where it is guaranteed. U1 is DNE 22V This also would exceed Vgs(max).
If this is your 1st attempt , it is impossible to design anything and have it work without failure and it will cost much more than buying one. But you may learn tools in the process. I recommend fast learners buy one then analyze it for load impedance ratio error and noise. Then learn how that works. It's simple resistor divider Ohms Law. The voltage drop load regulation error is the same % ratio of impedances for small values. Obviously 50% drop they are equal 1:1
If this is your 1st attempt , it is impossible to design anything and have it work without failure and it will cost much more than buying one. But you may learn tools in the process. I recommend fast learners buy one then analyze it for load impedance ratio error and noise. Then learn how that works. It's simple resistor divider Ohms Law. The voltage drop load regulation error is the same % ratio of impedances for small values. Obviously 50% drop they are equal 1:1
- #69
checkmatescott
- 80
- 2
Ok I think I understand that, so which should I choose ir2103 or lt1160 in your opinion? are there any books that you recommend for learning?
- #70
checkmatescott
- 80
- 2
so the vgs of the P-channel mosfets cannot go above -20v and and the chips are rated for 18v so must not exceed that.
- #71
checkmatescott
- 80
- 2
I need to choose the N-channel mosfets, how do I do this correctly?
- #72
checkmatescott
- 80
- 2
so these are the N chan fets that i have settled on
IRFP4668
I am still unclear how to make "The two halves a whole" or how to wire it up. As far as I can work out, the N chan fets are used as high side switches. The drain is connected to the supply voltage in my case it will be 55v and source to load. The gate needs the correct vgs to turn it on then I was looking at direct drive, level shifted drive, or bootstrap gate drive. In the picture you provided its a bootstrap driver and I suppose the logic in pins are important can I please have some guidance. Thanks again!- #73
checkmatescott
- 80
- 2
can you teach me how to use google effciently for example when you search that initial image and cross checked with the internet?
- #74
checkmatescott
- 80
- 2
what is personal speculation
- #75
checkmatescott
- 80
- 2
can you draw me a diagram of where and how to place components to at least give me a clue, in the form of a very rough schematic plase
- #76
- #77
DaveE
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Probably not.checkmatescott said:
- #78
- #79
checkmatescott
- 80
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logging off for the night, my eyes are gone cyas
- #80
berkeman
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Thread is on "pause" for a bit...
- #81
berkeman
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Whelp, it turns out that this newbie is an accomplished hacker of a number of things, and proud of it. He is now gone, and this thread will remain closed. Sorry that you spent so much time trying to help this "Help Vampire", but his intentions were not good. Thanks folks.berkeman said:
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