Dr Ronald Stiffler SEC technology

[itsu]

All,

i was looking into getting the x-tal oscillator to be able to supply over 20Vpp at 13.56Mhz.
I build the shown x-tal oscillator using a 13.56MHz x-tal and it works OK, then used the by
TK mentioned SN74AC14 to buffer/clean up the signal which shows a nice DC square wave like signal.

The problem however is to boost this 5Vpp 13.56MHz signal.
A normally used MOSFET driver will not cut it, my highspeed IXDN614CI works fine with a 4Mhz
X-tal, but fails to be stable at 13.56MHz (IXDN614 rise/fall times = 25/18ns).

RF version MOSFET drivers are very expensive.

Then i used a BJT totem pole setup as driver using BC547 and BC557 transistors and shows
promising results but when attaching a MOSFET (IRF840) the signal sags till some noisy ripples
unable to open the MOSFET.

So it will be a challenge to boost the 13.56MHz x-tal signal so its useable to drive the L3 coil
and CREE like leds board/diodes to full light.

Itsu

[erfandl]

Okay, very good.   Do you have to use the ferrite rod for fine tuning to get the brightness you show now?  Is this the maximum brightness you can get?  Try to use several such white LEDs in series too.

Hmm. thanks for helping me in this project. I solved the problem with a 1000 uh Barrel inductor. the 7 watt LED have a good brightness at 9 volt @ 67.6 mAh - 608.4 mW

[gyulasun]

Hi Itsu,

I have pondered on this and the first thing would be to utilize resonant voltage increase of tuned LC circuits right already in the xtal oscillator itself as a first step.
I mean to place a tapped LC circuit into the collector of the xtal oscillator to step up the 13.56 MHz signal to as high as possible with such transformation.  See this LC circuit how I mean:
https://overunity.com/17249/dr-ronald-stiffler-sec-technology/msg522125/#msg522125  The oscillator circuit can remain the same you have now, just remove the 1 kOHm or the choke coil from the collector and insert the LC tank there.  The L coil here could be wound on an RF toroidal core you may have from Amidon to have high Q for the tank. 

Another possibility is to use the air core coil itself (called here as L3) to step up resonantly the 13.56 MHz collector current to a relatively 'high' voltage. See this sketch here:
https://overunity.com/17249/dr-ronald-stiffler-sec-technology/msg522451/#msg522451 
What I mean here is this: coil wire #1 would go directly to supply voltage positive and coil tap #2 would go directly to the collector of the transistor. The air core coil should also resonate at 13.56 MHz,  basically this is very similar to the previous tapped LC tank suggestion, just the C is supplied by the air coil self capacitance and by the capacitive load the AV plug will represent with the LEDs too.  This latter 'autotransformer' is more difficult to tune to resonance than the LC tank on the toroid, due to the fully open L air coil.
If these resonant RF voltage up-transformer methods prove useless in the end, then we can ponder on further solutions...   
Gyula

[gyulasun]

Hmm. thanks for helping me in this project. I solved the problem with a 1000 uh Barrel inductor. the 7 watt LED have a good brightness at 9 volt @ 67.6 mAh - 608.4 mW

Hi Erfandl,
Very good progress!  It is good to suspect the behaviour of choke coils and now you chose a good type for the job.  Some adjustments you can still make would be to use a 100k or 220 kOHm trimmer potmeter to replace the 100 kOhm base resistor and adjust for the best brightness possible by that too.   Make sure to connect at least a 10 kOhm resistor in series with the trimmer potmeter to prevent excess base current when the potmeter is approaching to the very low resistance values, ok?  Try to wrap up the transistor body into a heat sink like metal cylinder to help conduct heat away from it.

A question: I cannot see it clearly from your picture: Do you have a ferrite rod in the coil now?

Gyula
PS The battery symbol is lit on the display of your DMM, it needs changing soon.   

[erfandl]

Hi Erfandl,
Very good progress!  It is good to suspect the behaviour of choke coils and now you chose a good type for the job.  Some adjustments you can still make would be to use a 100k or 220 kOHm trimmer potmeter to replace the 100 kOhm base resistor and adjust for the best brightness possible by that too.   Make sure to connect at least a 10 kOhm resistor in series with the trimmer potmeter to prevent excess base current when the potmeter is approaching to the very low resistance values, ok?  Try to wrap up the transistor body into a heat sink like metal cylinder to help conduct heat away from it.

A question: I cannot see it clearly from your picture: Do you have a ferrite rod in the coil now?

Gyula
PS The battery symbol is lit on the display of your DMM, it needs changing soon.   

thanks. OK I will order the 100k and 220k trimmer for testing and share the result when received. yes I used ferrite rod in the coil. Unfortunately, I do not have an oscilloscope that measures the coil frequency if I had an oscilloscope, the result would be better than that   
eh I didn't even notice the battery symbol  thanks for reminder