On a sunny day (Tue, 21 Aug 2012 10:26:37 -0700 (PDT)) it happened panfilero <panfilero@gmail.com> wrote in <d88db390-c12c-4dc4-91f8-7c8000d8973e@googlegroups.com>:>On Monday, August 20, 2012 11:01:28 PM UTC-5, panfilero wrote: >> Hello, >> >> >> >> I'd like to drive a small high frequency transformer at around 100kHz-300= >kHz with a 24Vpk signal, I tried building up an astable multivibrator with = >a couple of caps and transistors but i couldn't get it to drive the transfo= >rmer, it wouldn't even make anything close to a nice square wave.... anyone= > know of a better simple oscillator circuit I could use to do this? >> >> >> >> thanks! > >Thanks for the replies, I'm basically trying to turn 24V into 72V using a v= >oltage tripler, then I was gonna send that into a voltage regulator to clea= >n it up, the load is only going to draw maybe like.... 5mA.... so I was thi= >nking, take the 24Vdc, oscillate it somehow, feed it to a transformer and t= >hen triple it...For that sort of thing, get a small ferroxcube E core, and use 1 V / turn, 3 windings, one feedback. Diagrams have been published here. No tripler, 1 transistor, 1 tuning capacitor, 1 resistor, 2 decoupling caps, 1 rectifier diode, 1 rectifier cap. You can do the feedback in the base or in the emittor.
oscillator for driving a transformer
Started by ●August 21, 2012
Reply by ●August 21, 20122012-08-21
Reply by ●August 21, 20122012-08-21
For doing something like that, a circuit like this works well: http://t3sl4.dnsdynamic.net/Images/Deadbug_Sch.png Notes: - The base drive on the left-hand side drops a lot of voltage, so it starts getting impractical over 12V. This is most efficient for low voltages, where Vbe is relatively large. - Your step-up ratio isn't very much, so you could skip the tapped inductor and doubler, and just use a boost setup. This is only a matter of the inductor and output rectifier; the rest of the circuit remains the same. - Note that this circuit was built for current limited drive, because the output has to charge capacitors as shown. In boost mode, this goes away, and the switch will saturate efficiently. - For more power, the current limiting resistor (2.2 ohms) will have to be decreased, of course. Maybe a higher power switching transistor as well. - A MOSFET can be used for the main switch, just change the bias components a bit (i.e., short out the 100 ohm resistors so the 3904 and 3906 fight each other for gate voltage) and add a complementary emitter follower to drive the gate capacitance. At 24V supply, this will probably work fine, but for safety margin, a voltage limiting zener should be used to keep gate voltage below 15V or so. - Compensation components may need to be changed, of course. Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "panfilero" <panfilero@gmail.com> wrote in message news:d88db390-c12c-4dc4-91f8-7c8000d8973e@googlegroups.com... On Monday, August 20, 2012 11:01:28 PM UTC-5, panfilero wrote:> Hello, > > > > I'd like to drive a small high frequency transformer at around > 100kHz-300kHz with a 24Vpk signal, I tried building up an astable > multivibrator with a couple of caps and transistors but i couldn't get > it to drive the transformer, it wouldn't even make anything close to a > nice square wave.... anyone know of a better simple oscillator circuit I > could use to do this? > > > > thanks!Thanks for the replies, I'm basically trying to turn 24V into 72V using a voltage tripler, then I was gonna send that into a voltage regulator to clean it up, the load is only going to draw maybe like.... 5mA.... so I was thinking, take the 24Vdc, oscillate it somehow, feed it to a transformer and then triple it...
Reply by ●August 21, 20122012-08-21
panfilero wrote:> Hello, > > I'd like to drive a small high frequency transformer at around 100kHz-300kHz with a 24Vpk signal, I tried building up an astable multivibrator with a couple of caps and transistors but i couldn't get it to drive the transformer, it wouldn't even make anything close to a nice square wave.... anyone know of a better simple oscillator circuit I could use to do this? > > thanks!We use this type of oscillator via a tube to create the 100Khz for the rectifier stack on a 2Mev irradiation unit. http://en.wikipedia.org/wiki/Armstrong_oscillator You may also want to look at a basic blocking oscillator circuit. http://en.wikipedia.org/wiki/Blocking_oscillator Jamie
