DC to AC Output using a Step-up Transformer?

Thread Starter

pro86

Joined Aug 6, 2014
15
Hi All,

Does anyone have any good material or circuit diagrams to help me design a circuit based on the following info:
Input - 4x1.5V AA battery Supply (~6V)
Circuit - THIS IS WHAT I NEED HELP WITH
Transformer - 50/60Hz power isolated trans with ~9.58 step up / coil ratio
Output Required - 50-60V AC (This does not have to be Sinusoidal waveform. Square or something close to square i.e ramped edges is OK!) and less than 10mA current draw is required.

I have good circuit understanding but I just don't quite get what waveform and how (which IC circuit etc) to supply to the trans primary...

Thanks!
 

tranzz4md

Joined Apr 10, 2015
310
Search for the following thread:
Step-up DC to AC converter


Your oscillator or multivibrator to obtain a 50-60Hz signal will not be as much of a challenge as magnetizing just any old xformer at your energy level. You'll probably have some fiddling to do to get your magic combination. You may be able to tear up a couple wall-warts to get where you're going however.
 

avayan

Joined Oct 30, 2015
38
I did this with a full H Bridge. I fed the microcontroller timer output to the PHASE input. This made the primary switch from VIN to GND in both polarities. That is, when PHASE is HI, the primary sees VIN and when PHASE is LO, the primary sees -VIN. Back when I tried this a long time ago, I did it from 12V to 120VDC. It worked well!

Do note the trick is that as the voltage increases from primary to secondary, the current decreases from primary to secondary. Inversely, whatever current your secondary loads uses, will increase on the primary side. This means your H bridge will need to be able to drive this current, whatever it might be.
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Thanks so much guys. Sorry the reply has taken so long, I have been in Japan for work lately.

The transformer I am looking at using is a step down transfer from about 230vac to
24vac. But I'm looking using it in reverse to step up, this should be ok?

Avayan, thanks for your input. As to your query about the reduction of current as voltage increases, I only require approx 10mA output on the secondary side, therefore the primary would need to draw about 100ma. I'm not fully sure what an H bridge is, do you have a link on the theory?

Bordodynov, thanks so much for the spice circuit, this is exactly what I was looking for. I will attempt to create it in Lt spice.
A few questions though:
1] I understand the functions of the two mosfets on the left hand side of the circuit, but what are the other two doing/achieving as the outputs are connected to GND basically, are they providing alternating GNDs for each flip/flop etc?
2] the components you have selected, are the any standard size, cheaper versions of these as I'm trying to keep the cost down of I need to make Qty 50 of these circuits? I see these components run around the $1-2 range each, anything in the cents range using stand pcb 2.54mm pitch sizes?

Cheers.
 

Bordodynov

Joined May 20, 2015
2,939
I used a small timer (you can use the CMOS timer) to set the frequency. The supply voltage is not sufficient to obtain the required output voltage. The circuit uses the shutter drivers. Two are used for a voltage doubler (two-stroke circuit). The other two drivers are used as a bridge circuit. This circuit is powered by increased voltage. If you used a transformer with voltages of 240Volt -> 12V, the doubler would not be needed. You would save on two drivers, four diodes, and three capacitors.
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Thanks for the clarification Bordodynov,
I missed the outputs labelled "vcc1" and read them as just vcc, therefore not recognising their use as voltage multipliers..

Am I going to run into problems with reversing the normal step down transformer to use for step up, in terms of
 

Thread Starter

pro86

Joined Aug 6, 2014
15
... in terms of transformer design?
If I buy an isolation trans specifically for 230 to 24v step down at 50/60Hz, can it be used in the reverse effectively?
I have the trans data sheet at work and can provide if required?
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Also, are there Mic1557, Mic4420, Mic4420 equivalents available that are not surface mount? Obviously a 555 could be used in place of the 1557 with circuit modification, but surely there's a direct equivalent?
I would try using a basic templated pcb or breadboard to begin with therefore using surface mount is very difficult...
Cheers
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Hi bordodynov,
I tried adding your library from wikispice to my Lt spice library so I could access the mosfets required for this circuit. I've recreated the circuit but when I try to run simulation it states cannot find "MicrelPS1_1.lib".
I checked thr zip that downloaded from wikiqpice and the file does not exist...
Any suggestions?
Cheers
 

Bordodynov

Joined May 20, 2015
2,939
Apparently, you did not put my library in the right places. Required location (address) is determined by which version of the program you installed (IV or XVII). But I'm sending you a packed folder with a schematic and the necessary models. You can use other drivers. The main thing is that these drivers work at a voltage of 4.5 V. One must be a repeater, and the second inverter.
 

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DickCappels

Joined Aug 21, 2008
7,994
Thanks for the clarification Bordodynov,
I missed the outputs labelled "vcc1" and read them as just vcc, therefore not recognising their use as voltage multipliers..

Am I going to run into problems with reversing the normal step down transformer to use for step up, in terms of transformer design?
Yes. You will find the voltage ratio is not quite what you expect it to be. This is because in a transformer the primary drives both the load current and the magnetizing current and the secondary only drives the load current. Because of this the secondary may experience an higher voltage drop because of the higher voltage that winding which also has higher relative resistance. Just be prepared to drive the low voltage winding with a higher voltage or accept a lower output.
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Yes. You will find the voltage ratio is not quite what you expect it to be. This is because in a transformer the primary drives both the load current and the magnetizing current and the secondary only drives the load current. Because of this the secondary may experience an higher voltage drop because of the higher voltage that winding which also has higher relative resistance. Just be prepared to drive the low voltage winding with a higher voltage or accept a lower output.
Thanks for the wisdom Dick,
Due to your comment, I may change my transformer selection.
My trans supplier list is --> http://www.hammondmfg.com/162.htm
These of course are step down transformers from 230VAC.
Do you think it is reasonable to choose part no. 162E36?
It is dual primary and dual secondary winding. 2x115V Primary. 2x18V Secondary. 2.4VA Size.
If I use the primary in series, and secondary in parallel, this gives 230V primary & 18V @ 0.13A secondary, approx turns ratio 12.77:1
I obviously will use this in reverse with lower input V, therefore theoretically:
Vpri = 5V
Vsec = 5V x 12.77 = 63.85V (Assuming this would be less, according to Dick's comment above, but so long as not less than 48V.
Isec = 0.010 draw.
Ipri = 0.010 x 12.77 = 0.123A (This is just below trans winding design limit of 0.13A??)

If you think I'm cutting it too fine, are you able to suggest another transformer model part no. from the list on the link above??? Considering my required output voltage range is 48-60V, with load approx 10mA. Size is also a constraint, I would prefer only to use the 1.1 or 2.4VA sizes...

As always, thanks in advance.
 

Thread Starter

pro86

Joined Aug 6, 2014
15
Apparently, you did not put my library in the right places. Required location (address) is determined by which version of the program you installed (IV or XVII). But I'm sending you a packed folder with a schematic and the necessary models. You can use other drivers. The main thing is that these drivers work at a voltage of 4.5 V. One must be a repeater, and the second inverter.
Thanks so much Bordodynov, I will try this out when I get home from work.
 

Thread Starter

pro86

Joined Aug 6, 2014
15
I see I could also choose part no. 164E10.
Part: Primary 115V single wind, Secondary (in series) 10V @ 0.250A, Size = 2.4VA
This gives ratio 11.5:1
In my application
Vpri = 5V
Vsec = 5V x 11.5 = 57.5V
Isec = 0.010A
Ipri = 0.010A x 11.5 = 0.115A (Which is far below design limit 0.250A)


Or would I be better using 10V secondary in parallel from part no 164E20?

Which would give me lower winding resistance?
Am i right in assuming 164E20 with 2x 10V windings in parallel would give less winding resistance since it is effectively double the winding wire cross-sectional area?

Thoughts?
 
Last edited:

Thread Starter

pro86

Joined Aug 6, 2014
15
Apparently, you did not put my library in the right places. Required location (address) is determined by which version of the program you installed (IV or XVII). But I'm sending you a packed folder with a schematic and the necessary models. You can use other drivers. The main thing is that these drivers work at a voltage of 4.5 V. One must be a repeater, and the second inverter.

Hi Bordodynov,

After using your latest library components (as provided above) I'm receiving the following error when I try to simulate:

"Fatal Error: Unknown parameter "cpar"
in line:
"b:u2:3 n004«:vs» 0«:gn» i=(16e-5+13e-6*v(n004,0)*u(v(n003,0)-0.5*v(n004,0))) rpar=100meg cpar=40p""

When I remove the MIC1557 component simulation launches OK so I think the error may be related to the MIC1557 part?
Any ideas?
Thanks
 

Bordodynov

Joined May 20, 2015
2,939
This is not an error for LTspice. I showed the results of the calculation. Perhaps you "made it" with the installation of my libraries. I have two versions of the models of this timer. I'll put another option on the timer.
draft561.png Draft565.png
 

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Bordodynov

Joined May 20, 2015
2,939
Explanation of the calculation of Draft565. The 240 volt winding has a number of turns equal to {240 * 10} = 2400, the 12 volt winding has a number of turns equal to {12 * 10} = 120. Inductance per revolution is equal to Al = 1 mH. This value can be clarified by knowing the no-load current of the transformer.
 

Janis59

Joined Aug 21, 2017
1,357
Re: Pro 86 question
Why to not give a try of Cheeneeze wonder MC23063 for some 2 or 3 cents a piece (I bought a thousand for few dollars). Circuits like www.massmind.org/images/www/hobby_elec/e_ckt233_2.htm or at addendum of www.sparkfun.com/datasheets/IC/MC34063A.pdf

Yet I am not very happy with it when I need to work with very low voltages, then the MAX series are best, but at 4V5 it is trustful and well suited. However, my experience tells, the 10x up factor is maximum maximorum, if more it become non-prognozable. Other is that diode must be flashlike fast and with extreme tiny V(F). And coil is thing which one may use a identical inductance but 4 coils will work and 6 will not. Why? Have no an idea.
 
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