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Author Topic: 6 Battery Tesla Switch - Power Mosfet Circuit - Uses No Schottky Power Diodes  (Read 42045 times)


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This is the ultimate solid state tesla switch circuit.

I have eliminated all of the schottky power diodes which means that there is no significant component heating & no diode resistance to worry about.

All of the switching is done using power mosfets in their very low on resistance states which means very high currents can flow.

There are 4 diagrams, 2 are for the tesla switch itself A & B, with C the 555 Astable & D the Isolated 12 Volt Regulators.

Everything you need to build this circuit is shown below.

The circuit uses a total of six, 12 volt lead acid batteries to power the load.

3 batteries are wired in series to create 36 volts.
The total discharge current is 30 Amps.

3 batteries are wired in parallel to create 12 volts
The total charge current is 10 Amps per battery.

20 Amps are lost to the environment as heat or work done by the load.
This is the amount of energy that the environment needs to replace to keep the tesla switch running.

A switching circuit is used to set the frequency by which the batteries are changed from series to parallel.
When the switching frequency is high enough, the battery voltage should begin to increase under load.

The copper wiring must be constructed from hundreds of thin copper strands, whilst keeping the circuit resistance to an absolute minimum.
All of the connectors should be high quality copper or silver.

The output voltage across the load will be approximately 24 volts, & this will have to be regulated in someway using the 555 switching circuit.
The capacity of the batteries should be upwards of 40 amps, a small car battery is suitable.
The batteries need to deliver 30 Amps through the load, while only getting 10 Amps charging.
All of the batteries should have equal capacity & be in good condition.

The mosfet drive circuits use isolated 12 volt regulated supplies which can deliver 50 mA.
Dc to dc converters are available ready built, but you can make your own if you need more control over the circuit.

The n type mosfet gates are driven between 0 volts & + 12 volts using transistor pairs, in the push pull fashion.
Logic mosfets do not offer any advantage in this circuit, but they can be used if the gate voltage is held within its maximum swing.

You can place many n type mosfets in parallel to reduce the circuit resistance.
The push pull technique enables very fast charging & discharging of the mosfet gate capacitance, so paralleling mosfets is not a problem.

There are no schottky power diodes used in this circuit because they have been replaced by power mosfets.
There is no significant voltage drop across any of the switching devices.
There is no heating of the switching devices since the mosfets have very low on resistance.
There are no diodes placed in the high current path only mosfets with very low on resistance states.
There is no current flow through the mosfet internal diodes, it is all done through the mosfet channel.
There is no need to use large heatinks to cool any of the components.
Very little electrical power is required to run the switching circuits, less than 10 watts in total.

This tesla switch circuit works very efficiently indeed & has much greater potential of being able to deliver extreme power outputs.
If the total circuit resistance can be reduced significantly to less than 0.1 Ohm & a load of 0.4 Ohm or less is connected, over 1 Kilo Watt of free electrical energy can be obtained.

All of the circuit components are constantly switching on & off & are only being used 50 % of the time.
This circuit can be used to build switched capacitor charging circuits, which work in the same way as the tesla switch.

The opto isolator used in the circut diagram is the 4N25.
It is essentially a normal npn transistor, which is controlled entirely using an internal LED.
The resistor values on the 4N25 collector are between 2k2 to 3k3.
The internal LED requires a 1K or 470R, however this must be chosen depending upon the switching frequency.
The opto isolator diode drops 1.13 volts with a current of 10.8mA, which means they can be placed in series if running off a 12 volt supply.
The base of the photo transistor is left unconnected.
Even though the 4N25 is a slow device, it has been tested to function properly between 100 to 1Kz.
There is no need to use a schmitt trigger opto coupler device.

A number of opto isolator transistors have been placed in parallel.
This is to make absolutely sure that none of the mosfets can turn on at the wrong time.
There is a very short time delay between switches, which is controlled entirely by the transistors themselves.
The switching delay is automatically controlled & lasts 1 micro second.

The transistors used are : npn BC547 & pnp BC557.
The mosfets are all n-type IRFP064N with 50 Amp + drain to source current rating, very low on resistance with 55 volt working voltage.

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The mosfets have integrated zener diodes which do not interfere with the circuit operation.

When the mosfet is turned fully on, +12v gate to source, there is very little voltage drop across the mosfet & it behaves like a switch.
When the gate is shorted to the source terminal, the mosfet stops conducting & no current flows.
The only way current can flow when the mosfet is turned off is through the internal zener diode.
A mosfet can be used in the reverse direction as well as in the forward direction.
The internal zener diodes do not prevent a mosfet from being used back to front, since when the gate is high with repsect to the source,
intead of having a 0.6 volt drop you get 10mV or something insignificant, so you can still use it as a switch in the other direction.

No current is allowed to flow through any of the mosfet body diodes in this circuit.
The mosfets are turned hard on, immediately when the diodes become forward biased, thus eliminating any diodes in the high current path.

A number of 12 volt zener diodes have been placed on the base of the push pull circuit, this is to further regulate the 12 volt supply voltages.
The mosfet gate drive supply voltages can be clamped using zener diodes, transistors or 10 watt resistors.

Download Images & Schematics  - -

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« Last Edit: April 10, 2012, 04:50:26 PM by BediniBattery »


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This looks a bit daunting for anyone to jump in and build it, perhaps if you designed a pcb around it and actually show it in operation more people would like to jump in. You can even sell the pcb's for some monetary gain.


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I think Broli hit the essence. Despite my pretty long presence at this forum, I still feel "green" in electronics fields. Can someone estimate at least an approximate price of such circuit? I guess, I'm determined to build such (at least experimental) system.


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The majority of the circuit has been tested practically for functionality, so I am confident that this circuit will function properly without any diodes.

There will be a considerable amount of wiring up to do, not just the high current multicore copper cable but also the gate & source connections, however this enables the power mosfets to be positioned in a favourable place with respect of minimising all circuit resistance.

The numerous 12 volt isolated power supplies will be on one board with the switching circuit on another board.
The power supplies are created using a single mosfet switching circuit & a ferrite toroid with multiple low current secondaries.
12 turns on the primary & secondary is sufficient.
The frequency used should be over 20Khz with pulse width adjustment.
Iron dust cores require more turns but they can also be used.

A minature step down or any volt switching regulator can hold the power supply input voltage so that the isolated power supply circuit does not use more power than is required. A spare battery can be used to power this circuit.

The secondaries need full wave schottky rectifying & a 2200 uF capacitor at 16 volts.
The secondary dc supplies will be voltage clamped at 12 volts using a power transistor & zener diode.

When one secondary winding is clamped, it has an effect on the other windings, but each one will have a seperate voltage clamp to ensure
that none of the mosfet gates are driven over 15 volts. Many voltage clamps will spread the total power dissipation of about 5 watts.
The amount of current used at 12 volts will be 200ma approx, depending on any additonal loading.

This is a work in progress so if there are any errors or mistakes, I will be correcting them as & when I find a problem.

The expensive components are the power mosfets & the lead acid batteries, the rest of the circuit uses low cost parts.


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Some problems(?)

The South African company trying to bring this product to market: while it works fine within 3 weeks, it got problems after 3-4 months. The inventor says it's easy to fix, but it needs further tests.


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Here is the Isolated 12 to 15 Volt Power Supply Circuit which is used to power each of the seperate mosfet gate circuits.

There are 13 circuits which need an isolated 12 volt supply, each of them has a seperate voltage regulator, rectifier & one secondary winding.

The voltage regulator is build using a single T0220 npn power transistor, a 5 watt 12 volt zener diode & 3k3 2 watt resistor.
A small heatsink is required for the transistor, the power dissipated is under 3 watts per transistor.
The recommended voltage regulating transistor is TIP31C as this has 100 Volts Collector Emitter Breakdown.

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There are two discrete voltage regulating stages, one is shown in the circuit below, while the other ones are shown in the mosfet gate drive circuits in part A & part B.

The mosfet gates should be driven to at least 11 volts to ensure they are turned fully on.

The ferrite toroid single mosfet switching circuit is not regulated as such but it does have a pulse width adjustment to set the output voltage under load.
The loading will be constant once all of the circuits are wired up. Once the pulse width is adjusted correctly, it does not have to be changed.
The output voltage should stay just above 12 volts under the full load of all 13 circuits.

The input voltage to the isolated power supplies must be voltage regulated in a similar manner as shown or you can use a mini switching regulator or any volt device.
The desired input voltage is between 11 to 12 volts.


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This is part E of the 6 battery tesla switch, which shows a simple technique to prevent over charging of the lead acid batteries by
means of reducing the battery switching frequency.

When the battery voltage exceeds 15 volts, the switching frequency is reduced considerably.
When the battery voltage falls below 14.4 volts the switching frequency increases to charge the batteries.

The exact turn on voltage can be adjusted using different zener diode values.
The zener diodes are all 0.5 watt type.

A small 100 uF capacitor is placed on the pcb close to the 555 timer, to eliminate any spikes & to slow down any frequency changes.

Battery 3 & Battery 6 both have their negative terminals connected to 0 Volts so it is easy to measure their potentials accurately.

They are shown in diagrams A & B.

To measure two batteries at the same time, use a seperate 10 K resistor & zener diodes & onboard capacitor, but use the same transistor (OR Gate).

The positive terminals of Battery 3 & Battery 6 must not be connected together because one is part of the charge circuit & the other is part of the discharge circuit.

The discharge & charge batteries must be seperated, however their battery potentials can still be measured accurately while in operation.

This gives the basis of a self regulating tesla switch charge circuit.


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How to connect battery 3 & battery 6 to the voltage controlled oscillator
« Reply #7 on: April 17, 2012, 08:44:42 PM »

This shows how to connect battery 3 & battery 6 to the voltage controlled oscillator.

An improvement from Part E


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Zipped BMP schematics & ExpressSCH Files for 6 Battery Tesla Switch Without Diodes.

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There are no pcb design files yet only schematics(22 April 2012).

Slide Show : - -

I am currently designing the Tesla Switch PCB using electronic workbench UtilBoard 8.
A single sided board measuring 203 X 305mm will be required to build the basic switching circuit & over charge protection circuits.

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The main board will control the mosfet switching & provide all of the 12 volt isolated power supplies to each individual section of the circuit.

I have decided to wire up each mosfet gate circuit using 0.1" or 0.156" PCB Terminal Connectors.
This will allow the board to be constructed more easily & will enable fault finding to be done quickly.
There will be quite a lot of manual wiring up to do on the board itself.
A 10k resistor should be soldered between the mosfet gate & source to keep it turned off while the gate drive cable is disconnected from the board.

I have completed the majority of the schematics, I would advise everyone to wait until I have uploaded a working pcb layout as it is quite complex.
« Last Edit: April 22, 2012, 11:37:35 PM by BediniBattery »


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Power Rectifier Diodes - Forward Voltage Drops & Peak Inverse Voltages
« Reply #9 on: April 26, 2012, 10:50:13 PM »
Power Rectifier Diodes - Forward Voltage Drops & Peak Inverse Voltages

Here is a list of parts that I recommend using for building various switch mode power supply devices, or pulse charge circuits for charging batteries.

The most important component will usually be a rectifying diode, mosfet & ferrite or iron dust toroid.

Whatever circuit you are building, take a close look at which diodes you choose to put in your circuits.

Here are the results of forward drops taken across a number of different diodes during a 0.4 amp load current.

If you want to use a diode for zener voltage regulation purposes, the forward voltage drop cannot be relied upon.

Not all schottky diodes are the same.

The same situation is true of magnetic toroids, as there are so many of them & they all have different characteristics.

Some work better than others, but you won't know until you test it practically.

Download the data sheets here :

Zipped Files & Data Sheets- -

MBR2045CT - Forward Volt Drop = 0.357 Volts - Peak Inverse Voltage 45 Volts - 20 Amp

60CTQ150PbF - Forward Volt Drop = 0.380 Volts - Peak Inverse Voltage 150 Volts - Dual Schottky Rectifier - 60 Amp

1N5819 - 1A Schottky Diode - Forward Volt Drop = 0.402 Volts - Peak Inverse Voltage 40 Volts - 1 Amp

BYW80 150 - Forward Volt Drop = 0.663 Volts - Peak Inverse Voltage 150 to 200 Volts

1N4001 to 1N4007 Silicon Diodes 1 Amp - Forward Volt Drop = 0.858 Volts

500mW BZX55C Zener Diodes for Voltage Regulators

13 Volt Combinations - 6v2 & 6v8 or 4v7 & 8v2 or 3v0 & 10v

13 Volt Zener Diode

N - Type Power Mosfet

IRFP064N - TO-247 Package

VDSS = 55V
RDS(on) = 0.008R
ID = 110A

P - Type Power Mosfet


VDSS = -55V
RDS(on) = 0.06R
ID = -31A

NPN Power Transistor - TIP31C

T0220C Package
DC Current Gain -hFE = 25(Min)@ IC= 1.0A
Collector-Emitter Sustaining Voltage : VCEO(SUS) = 40V(Min)- TIP31; 60V(Min)- TIP31A 80V(Min)- TIP31B; 100V(Min)- TIP31C

Complement to Type TIP32/32A/32B/32C

Light Green Ferrite Toroid

TR-25x15x12C-CF139 - £0.73

25x15x12mm ferrite toroid - Coating: Epoxy
Manufacturer: Cosmo Ferrites
Material Grade: CF139 (Equivalemt to Ferroxcube 3C90 / 3C94; Epcos / Siemens N87; TDK PC44 )


Outside Dia: 25mm
Inside Dia: 15mm
Height: 12mm
Weight: 19.0g

Magnetic Characteristics:
uiac = 2100
AL Value = 2450 - Permeability


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Isolated 12 Volt Supplies With Stabilized 12 Volt Input
« Reply #10 on: April 30, 2012, 09:06:33 PM »
This circuit is intended to use discrete components to regulate the input voltage of the voltage regulator to 12 or 13 volts & to maintain that input voltage under all circumstances by making use of all 6 lead acid batteries. It is very difficult to maintain the correct input voltage to the switch mode power supply without some assistance from a higher voltage supply, such as 24 or 36 volts.

By using discrete components, the circuit will be more reliable & easier to build.

I did not want to use another battery to power the isolated supplies as this would need to be charged in some way.
I have made use of some free energy from the inductor flyback & also some current obtained from the 3 series batteries, 1,2,3 & 4,5,6.

There is a 20 watt, 25 Ohm resistor, which drops about 20 volts at 0.4 amps. The resistor value is approximate.

This resistor is used to boost the input voltage to the voltage regulator when battery 3 & battery 6 are below the desired voltage level.

A zener diode sets the turn on voltage for the mosfet switch & thus the voltage regulator input voltage.

Even though the circuit is not very efficient, it is very reliable & easy to build.

Efficiency is not important here, however what is important is that the switch mode power supply is able to provide an isolated 12 volt supply to all of the power mosfet switches.

The tesla switch circuit is designed to use a ridiculous amount of current .

This will provide a permanent load on all of the batteries, which will not only show when free energy is being created but will help to prevent over charging as well.

The zipped schematic files & BMP images can be downloaded here  - -

The PCB is about 1/2 done so far, this is the most difficult part.


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Great work ! have you got it going ?

I made a little test setup a few years ago using -
 4x 4.8ah sla batteries, 6x transistors npn (tip61c), 220ohm base resistors and 24x 1N5408 diodes - 8 x 3 in parallel
i think ? i used the mueller report solid state circuit diagram by John Bedini and @ the time i used a 12v brushless  pc fan for the flip flop 50% triggering of the transistors, i was using the bemf from the two coils in the pc fan while running the fan from FWBR off the two positive potentials and not the negative side. Anyway i gave up after two of the batteries run down to zero and the other two went to around 18v.
Being a idiot i broke the setup down to use the parts for other projects !

Since then i`ve been distracted by other projects - Ev Gray`s conversion tube, John Bedini solid state battery charger

I`ve been planning to give the tesla switch another go but build much bigger !
so far i have 6 identical 40ah Yuasa batteries , 8 igbt`s rated @ 600v 150amp/300amp if pulsed no flyback diodes, large collection of 50amp diodes, a few heavy duty large transformers and other stuff : ) just have`nt decided how i`m going to put it all together yet ?

Sorry for rambling, just nice to see that there are people out there giving the tesla switch ago !


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Well done.  You're clearly on the right path to achieve efficient
switching by the use of MosFets.

There are a few things which may be done to further enhance the
overall efficiency of your circuit.

It is possible to build a switching supply using an Analog Voltage
Regulator as the control chip.  You may use discrete components
(I like that approach as well, especially for the developmental
phases) to utilize their cost advantage while creating the lower
voltage you need without the high wattage dropping resistor.

Check the Applications section of the LM78XX Data Sheets for
circuit suggestions - they're quite versatile.

And the sub-circuit switching supply which provides power to
each of the individual MosFet drivers can be constructed as
a regulated switching supply as well where regulation takes
place directly in the input switching.

It's highly probable that you would have discovered these
potential solutions on your own as it is evident that you are
quite capable at researching innovative concepts.  As a matter
of fact you may already have considered these possibilities.

Once again, well done.


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nice, very nice.
am already looking for batteries  ;)


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6 Battery Tesla Switch - Update 06 06 2012
« Reply #14 on: June 07, 2012, 03:40:23 AM »

The above posts contain some trial & error work which have errors.

I have simplified the circuits, so there is less work to do.

4 circuit diagrams only.

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Download the latest circuit diagrams, schematics & explainations all in one zip file.

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