Cap Dump Circuit

[totoalas]

Hi all
can ur ckt be used in solar charged primary with sg oscillator also

[BroMikey]

Solar

Hi all
can ur ckt be used in solar charged primary with sg oscillator also

Hi Totoalas

If you run the solar panel to the lights in the house and pulse charge the battery AT THE SAME TIME you will trash your inverter.

If you shorten the pulse time and lower the current dumped you will extend the life of your inverter.

Mike

[Mario]

Hi Mike,

sorry if I confused you. I didn't mean exactly 1%, I just meant you need to be able to adjust your timer duty cycle from almost nothing to very narrow. This is the time you allow the cap to dump. This depends on the size of your caps, mosfet resistance, wire resistance, battery impedance, etc… But the way to find out the correct duty cycle or ON time is to hook your scope to the cap and watch the dump, so you can adjust the time. You want your cap to dump and stop at a couple volts (2-5V) over the battery voltage. So the ON time (dump time) can be in the very low millisecs duration, depending on the factors above.

So basically you have the rise time which is how long it takes your mosfet to turn ON, then the ON time (duty cycle or cap dump duration) , and at turn OFF you have the fall time. The rise/fall times with your opto you should be able to get down to 4-5 microsecs, with the correct resistors.

regards,
Mario

[totoalas]

Hi Totoalas

If you run the solar panel to the lights in the house and pulse charge the battery AT THE SAME TIME you will trash your inverter.

If you shorten the pulse time and lower the current dumped you will extend the life of your inverter.

Mike

Thanks Bro Mikey
you give me some insight on my future set up
Im using Cool joules SSG monster charger with my alum batteries
planning to migrate to cap dump and your design is easy to follow

Im current ly using zpdm oscillator with induction from a wall adaptor and earth ( no batteries) to charge a 470 uf 450 v dc cap up to 338 v in 9 hours.....
will use this as a source beside my solar and sg motor/gen to go to the cap dump circuit
thanks

[BroMikey]

30 mili-seconds

Hi Mike,

sorry if I confused you. I didn't mean exactly 1%, I just meant you need to be able to adjust your timer duty cycle from almost nothing to very narrow. This is the time you allow the cap to dump. This depends on the size of your caps, mosfet resistance, wire resistance, battery impedance, etc… But the way to find out the correct duty cycle or ON time is to hook your scope to the cap and watch the dump, so you can adjust the time. You want your cap to dump and stop at a couple volts (2-5V) over the battery voltage. So the ON time (dump time) can be in the very low millisecs duration, depending on the factors above.

So basically you have the rise time which is how long it takes your mosfet to turn ON, then the ON time (duty cycle or cap dump duration) , and at turn OFF you have the fall time. The rise/fall times with your opto you should be able to get down to 4-5 microsecs, with the correct resistors.

regards,
Mario

Hi Mario

I am down to as low as 30 mS using 560 ohms dumping 80vdc from 80,000uF.

I burned up my small dump driving to the max on the big yard battery, then I burned up my SSSG Osc transistors over driving them so I am going to bring in a slight evolution for the Solid State Version Oscillator.

Plus I am putting together two toroidals, one hand wound 115v down to 55v and the other is a 30 amp 400hz toroidal variac with bridge and caps.

It was almost done last night. This unit gives me 0-70vdc and then also last night I got out my one foot long 1 ohm resistors and charged and discharged my cap bank watching the delay. Perfect.

This resistor will let me run 10-50 amp surges with slightly delayed charge times.

This will be easier from this pulsating arrangement.

The room is a total disaster.

I will get it all done ASAP.

Mike

[BroMikey]

New Oscillator

Thanks Bro Mikey
you give me some insight on my future set up
Im using Cool joules SSG monster charger with my alum batteries
planning to migrate to cap dump and your design is easy to follow

Im current ly using zpdm oscillator with induction from a wall adaptor and earth ( no batteries) to charge a 470 uf 450 v dc cap up to 338 v in 9 hours.....
will use this as a source beside my solar and sg motor/gen to go to the cap dump circuit
thanks

Great totoalas

This new Oscillator is a darlington?

Keep at it.

Mike

[totoalas]

Great totoalas

This new Oscillator is a darlington?

Keep at it.

Mike

http://www.energeticforum.com/renewa...tml#post246907

[thx1138]

A few notes

If you know this already just disregard but I thought it might be helpful.

The MOSFET's used at the cap-dump are voltage controlled devices. The voltage applied to the gate determines when and how fast they turn on.

We'll call the resistor connected to the gate R1 and the resistor connected between the gate and the drain R2.

R1 acts as a current limiting device between the power from Wiley and the MOSFET.

I = R / V

So raising the resistance decreases the current which isn't important to the MOSFET since it is voltage driven but does affect how much power will be drawn from the driving circuit.

The two resistors that you show at each MOSFET (R1 and R2) results in a voltage divider. These will affect the MOSFET switching since they affect the voltage. Vout will be the voltage between R1 and the gate. Vin is the volatage from Wiley to R1.

Vout = Vin * (R2 / ( R1 + R2))

The transistor you show in the 555 circuit is a BJT (Bipolar Junction Transistor) and it is driven by current rather than voltage. So the current limiting resistor in this circuit does affect the turn-on time of the transistor. It affects how much current is available to turn the circuit on and how fast that current accumulates in the transistor.

This may help you do some calculations to determine the switching you need. You compare the values calculated to the device datasheets to attain the results you want. If the device you are using won't give the results you desire just look for another device.

[BroMikey]

Voltage dividing and voltage driven gate

If you know this already just disregard but I thought it might be helpful.

The MOSFET's used at the cap-dump are voltage controlled devices. The voltage applied to the gate determines when and how fast they turn on.

We'll call the resistor connected to the gate R1 and the resistor connected between the gate and the drain R2.

R1 acts as a current limiting device between the power from Wiley and the MOSFET.

I = R / V

So raising the resistance decreases the current which isn't important to the MOSFET since it is voltage driven but does affect how much power will be drawn from the driving circuit.

The two resistors that you show at each MOSFET (R1 and R2) results in a voltage divider. These will affect the MOSFET switching since they affect the voltage. Vout will be the voltage between R1 and the gate. Vin is the volatage from Wiley to R1.

Vout = Vin * (R2 / ( R1 + R2))

The transistor you show in the 555 circuit is a BJT (Bipolar Junction Transistor) and it is driven by current rather than voltage. So the current limiting resistor in this circuit does affect the turn-on time of the transistor. It affects how much current is available to turn the circuit on and how fast that current accumulates in the transistor.

This may help you do some calculations to determine the switching you need. You compare the values calculated to the device datasheets to attain the results you want. If the device you are using won't give the results you desire just look for another device.

Hello thx1138

Say on. I am in need up these refresher talks. I have not given much of my life to this work and while I am hard at it now, information like you have offered is perfect for quick and easy practical application.

This is the kind of rehearsal I need.

Mike

[Farmhand]

To properly turn on and off a mosfet quickly and sharply a certain current and
voltage is required, the reason is that the gate of the mosfet is basically a
capacitor and to turn the mosfet full on requires the gate be charged to 10 volts
as quickly as possible, for logic level the gate only need be charged to 5 volts.

The higher value resistor to the gate of the mosfet does indeed slow down the
mosfet turn on time. For a regular mosfet the "threshold" voltage is around 4 volts
but that is only when the mosfet begins to turn on, to get the lowest "on"
resistance the mosfet needs to be turned fully on, the quicker it is turned fully
on and off the less power is dissipated by the mosfet.

The mosfet gate has a very high resistance (effectively infinite) but the
capacitance allows the gate to charge via displacement current just like any
other capacitor.

I usually use TC4420 mosfet driver chips which are 6 amp peak current parts.

If the mosfet turns on and off slowly it will dissipate more power and heat up.

You should be able to turn on the mosfet with a "rise" time of nS, the delay
time is irrelevant to power dissipation the rise and fall time is the time it take
to turn the mosfet on or off.

For example an IRF740 mosfet has an input capacitance of 1400pF, so to
charge that capacitance quickly requires a relatively high peak current. That
current is displacement current, just like charging a capacitor, if you try to
charge a capacitor through a resistor it will charge slower and so if you try to
charge a mosfet gate with a resistor the higher the value of the resistor the
slower the mosfet will turn on. Similarly if the drive signal to the mosfet gate
cannot supply sufficient peak current the mosfet will turn on slower as well.

Typically I don't use a resistor between the driver and the gate unless the
mosfet is switched at high frequency > 500 Khz, in the case of HF switching
the mosfet driver can get hot due to the current it is required to deal with if
the mosfet driver gets hot then a resistor of fairly low value 10 Ohms or so
maybe more or less between the driver and the gate will alleviate that but not
too high so as to restrict the drive current too much .

The resistor between the gate and circuit ground/mosfet source typically
between 2 to 10 K is mainly to ensure the mosfet remains off when not driven,
preventing it turning on when not wanted, it is not really necessary with
dedicated driver chips or even some oscillator chips like the SG3525.

Driving power mosfets.
http://ww1.microchip.com/downloads/e...tes/00786a.pdf

A quote from the PDF linked above.

1. MOSFET gate drive rise and fall times must be symmetrical,
and as short as possible. A driver like the TC4427 has a
specified tR and tF of approximately 19nsec into a 1000pF
load. A higher peak output current driver may be selected to
achieve more aggressive rise and fall times if so desired.

Don't believe anyone who says you don't need current to switch a mosfet properly.

To switch the mosfet on and off quickly a drive voltage of at least 10 to 15 volts
and sufficient drive current to charge the gate capacitance at the desired
rate is required.

The easiest and most reliable way to do that is with a dedicated mosfet driver.

Cheers

[BroMikey]

Great Answers

To properly turn on and off a mosfet quickly and sharply a certain current and
voltage is required, the reason is that the gate of the mosfet is basically a
capacitor and to turn the mosfet full on requires the gate be charged to 10 volts
as quickly as possible, for logic level the gate only need be charged to 5 volts.

The higher value resistor to the gate of the mosfet does indeed slow down the
mosfet turn on time. For a regular mosfet the "threshold" voltage is around 4 volts
but that is only when the mosfet begins to turn on, to get the lowest "on"
resistance the mosfet needs to be turned fully on, the quicker it is turned fully
on and off the less power is dissipated by the mosfet.

The mosfet gate has a very high resistance (effectively infinite) but the
capacitance allows the gate to charge via displacement current just like any
other capacitor.

I usually use TC4420 mosfet driver chips which are 6 amp peak current parts.

If the mosfet turns on and off slowly it will dissipate more power and heat up.

You should be able to turn on the mosfet with a "rise" time of nS, the delay
time is irrelevant to power dissipation the rise and fall time is the time it take
to turn the mosfet on or off.

For example an IRF740 mosfet has an input capacitance of 1400pF, so to
charge that capacitance quickly requires a relatively high peak current. That
current is displacement current, just like charging a capacitor, if you try to
charge a capacitor through a resistor it will charge slower and so if you try to
charge a mosfet gate with a resistor the higher the value of the resistor the
slower the mosfet will turn on. Similarly if the drive signal to the mosfet gate
cannot supply sufficient peak current the mosfet will turn on slower as well.

Typically I don't use a resistor between the driver and the gate unless the
mosfet is switched at high frequency > 500 Khz, in the case of HF switching
the mosfet driver can get hot due to the current it is required to deal with if
the mosfet driver gets hot then a resistor of fairly low value 10 Ohms or so
maybe more or less between the driver and the gate will alleviate that but not
too high so as to restrict the drive current too much .

The resistor between the gate and circuit ground/mosfet source typically
between 2 to 10 K is mainly to ensure the mosfet remains off when not driven,
preventing it turning on when not wanted, it is not really necessary with
dedicated driver chips or even some oscillator chips like the SG3525.

Driving power mosfets.
http://ww1.microchip.com/downloads/e...tes/00786a.pdf

A quote from the PDF linked above.



Don't believe anyone who says you don't need current to switch a mosfet properly.

To switch the mosfet on and off quickly a drive voltage of at least 10 to 15 volts
and sufficient drive current to charge the gate capacitance at the desired
rate is required.

The easiest and most reliable way to do that is with a dedicated mosfet driver.

Cheers

Hello Farmhand

Thanks A Million, this is a good answer for me because I have been needing to collect my thoughts about the way to turn these fets on and off.

So far I have been using a 555 timer to triger a OPTO and from the OPTO I am using a buffer transistor that cam handle more power to drive 12 IRFP250 fets.

My on time does not need to be in the nS but it is a great confirmation that the possibility does exist. Looking at the Bedini patent for his energy pump sg3524 he states that 100mS is the target.

So rise time and fall time and ON TIME???? HUmm ...........................

I am not sure what 100mS is for, maybe ON TIME?

Then I am wondering if a quicker rise time helps and just how much help.

Of course there is the stability of the parts operating within their design perimeters so as not to over heat them and burn them out.

Thank you for putting forth special effort to help me think this through.

I better go back and read your post again.

Well i read it again now and I think I am going to order. I will do it my way for now and see the difference. Been working all night on the 3 components I will be showing you guys. Huge dump, Modified Energizer convertor Oscillator and power supply made from 2 toroidal transformers one variable 0-70vdc @ 30amps 95 percent efficient power conversion.

You guys are cool. Thanks

Mike

[BroMikey]

pulsing594.JPG

Here is a circuit that I have 3 of. What do you think about that? All comments excepted.

The only question I need to ask is how can I use this circuit to drive 12 IRFP250 fets all at the same time the same way. In unison.

The TC4420 will not have enough power to run 12 mosfets this size I don't think.

Thanks for each of your comments.

All comments will be treated with high regard.

Mike

[Mario]

Hi Mike,

Check the data sheets of your devices, how many pf is the capacitance of your mosfet gate, how many pf can your driver handle? If one driver is not enough run a few of them in parallel.

Also check the SOA curve (safe operating area) on your mosfet data sheet, it tells you how many amps at how many volts for a given on time is safe so you won't blow it.

regards,
Mario

[blackchisel97]

[ATTACH]14238[/ATTACH]

Here is a circuit that I have 3 of. What do you think about that? All comments excepted.

The only question I need to ask is how can I use this circuit to drive 12 IRFP250 fets all at the same time the same way. In unison.

The TC4420 will not have enough power to run 12 mosfets this size I don't think.

Thanks for each of your comments.

All comments will be treated with high regard.

Mike

Hi Mike,

I would use double drivers for each pair of Fet's. Check the Mouser site and search for double gate non inverting drivers - gate driver dual Integrated Circuits - ICs | Mouser

Regards
V

[BroMikey]

Dual 4A Mosfet Drivers

Hi Mike,

I would use double drivers for each pair of Fet's. Check the Mouser site and search for double gate non inverting drivers - gate driver dual Integrated Circuits - ICs | Mouser

Regards
V

Hello V

SO each dual driver chip will handle one mosfet for each channel. So I need to parallel 6 dual chips together, driven by a single tl594? Non-inverting.

My circuits now run fine using non inverting TC4420 and run 2 large Mosfet's.

Can you tell me the benefit of going to Non inverting dual??

Paralleling must occur for both arrangements.

I feel bad today but I may run upstairs and show you all my work anyway in a minute.

I have been working day and night.


Sounds like it would make a big flash

I hold your entry in high regard so when you get time let me know what you found. I am going to guess that that many fets run cooler and this means less conflict.

Am I right?

Mike