Forums

Help With Royer Oscillator

Started by Kooner January 24, 2011
Hello,

I have a working Royer Oscillator. This version is not current fed. It
is a push push tolpolgy and the LC oscillationis are set by the
transformer inductance and winding capacitance. The schematic looks
like a multivibrator except the reistors in the collectors are
replaced withthe half primaries of the pushpull transformer.

This circuit has BJTs and has a sine wave output but I when I replace
them with Mosfets the output is square wave. I've been simulating this
thing for a week now and can't get the output to be sinewaves liek the
BJT version.

In the BJT version  there are  caps connected from the base of one BJT
to the collector of the other BJT and they stay charged to twice Vcc.
The current that charges these caps flows though the BE didoe.  With
mosfets that current path is not there so they don't stay charged to
twice Vcc. I think there might be other differences too.

Can anyone point me to link with some more info on using Mosfets in  a
Royer Osciilator? Is there a way to post a schematic here?

Jason.
On Mon, 24 Jan 2011 13:49:36 -0800 (PST), Kooner <jjkooner@gmail.com>
wrote:

>Hello, > >I have a working Royer Oscillator. This version is not current fed. It >is a push push tolpolgy and the LC oscillationis are set by the >transformer inductance and winding capacitance. The schematic looks >like a multivibrator except the reistors in the collectors are >replaced withthe half primaries of the pushpull transformer. > >This circuit has BJTs and has a sine wave output but I when I replace >them with Mosfets the output is square wave. I've been simulating this >thing for a week now and can't get the output to be sinewaves liek the >BJT version. > >In the BJT version there are caps connected from the base of one BJT >to the collector of the other BJT and they stay charged to twice Vcc. >The current that charges these caps flows though the BE didoe. With >mosfets that current path is not there so they don't stay charged to >twice Vcc. I think there might be other differences too. > >Can anyone point me to link with some more info on using Mosfets in a >Royer Osciilator? Is there a way to post a schematic here? > >Jason.
Post the schematics, and we can better understand the situation. John
On Jan 24, 4:49=A0pm, Kooner <jjkoo...@gmail.com> wrote:
> Hello,
<snip>
> Is there a way to post a schematic here?
You can post a schematic several ways. -- You can draw simple schematics in ASCII characters in fixed-width fonts, and post directly to the newsgroup. -- You can cut, paste, and directly post the (ACSII) contents of an LTSpice .asc file directly to the newsgroup. -- you can post a .JPG, .PNG, or other binary image to alt.binary.schematics.design -- you can post a graphic to your own website, or a 3rd-party photo site. -- Cheers, James Arthur
On 01/24/2011 01:49 PM, Kooner wrote:
> Hello, > > I have a working Royer Oscillator. This version is not current fed. It > is a push push tolpolgy and the LC oscillationis are set by the > transformer inductance and winding capacitance. The schematic looks > like a multivibrator except the reistors in the collectors are > replaced withthe half primaries of the pushpull transformer. > > This circuit has BJTs and has a sine wave output but I when I replace > them with Mosfets the output is square wave. I've been simulating this > thing for a week now and can't get the output to be sinewaves liek the > BJT version. > > In the BJT version there are caps connected from the base of one BJT > to the collector of the other BJT and they stay charged to twice Vcc. > The current that charges these caps flows though the BE didoe. With > mosfets that current path is not there so they don't stay charged to > twice Vcc. I think there might be other differences too. > > Can anyone point me to link with some more info on using Mosfets in a > Royer Osciilator? Is there a way to post a schematic here?
A quick search on Royer oscillator got me this page: http://wiki.4hv.org/index.php/Royer_oscillator, which has one made with MOSFETs. Neither of their circuits have any caps from collector to base. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
On Mon, 24 Jan 2011 15:02:50 -0800, Tim Wescott <tim@seemywebsite.com>
wrote:

>On 01/24/2011 01:49 PM, Kooner wrote: >> Hello, >> >> I have a working Royer Oscillator. This version is not current fed. It >> is a push push tolpolgy and the LC oscillationis are set by the >> transformer inductance and winding capacitance. The schematic looks >> like a multivibrator except the reistors in the collectors are >> replaced withthe half primaries of the pushpull transformer. >> >> This circuit has BJTs and has a sine wave output but I when I replace >> them with Mosfets the output is square wave. I've been simulating this >> thing for a week now and can't get the output to be sinewaves liek the >> BJT version. >> >> In the BJT version there are caps connected from the base of one BJT >> to the collector of the other BJT and they stay charged to twice Vcc. >> The current that charges these caps flows though the BE didoe. With >> mosfets that current path is not there so they don't stay charged to >> twice Vcc. I think there might be other differences too. >> >> Can anyone point me to link with some more info on using Mosfets in a >> Royer Osciilator? Is there a way to post a schematic here? > >A quick search on Royer oscillator got me this page: >http://wiki.4hv.org/index.php/Royer_oscillator, >which has one made with MOSFETs. Neither of their circuits have any >caps from collector to base.
That BJT version is a guaranteed croaker (Needs diodes to limit reverse Vbe). Did Larkin draw that up ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Remember: Once you get over the hill, you pick up speed
"Tim Wescott"
> > A quick search on Royer oscillator got me this page: > http://wiki.4hv.org/index.php/Royer_oscillator, > which has one made with MOSFETs. Neither of their circuits have any caps > from collector to base.
** That is one brutal looking circuit !!!! At the start, both MOSFET gates are permanently biased hard on with a 12V zener regulated supply !! Then somehow it starts ( ??) and each MOSFET is able to rob bias from the other when it's turn comes to be fully conducting. It says also a 10 amp supply is needed and the 0.68uF, 250V cap "Must Be Good" . Brutal. .... Phil
On Mon, 24 Jan 2011 15:02:50 -0800, Tim Wescott <tim@seemywebsite.com>
wrote:

>On 01/24/2011 01:49 PM, Kooner wrote: >> Hello, >> >> I have a working Royer Oscillator. This version is not current fed. It >> is a push push tolpolgy and the LC oscillationis are set by the >> transformer inductance and winding capacitance. The schematic looks >> like a multivibrator except the reistors in the collectors are >> replaced withthe half primaries of the pushpull transformer. >> >> This circuit has BJTs and has a sine wave output but I when I replace >> them with Mosfets the output is square wave. I've been simulating this >> thing for a week now and can't get the output to be sinewaves liek the >> BJT version. >> >> In the BJT version there are caps connected from the base of one BJT >> to the collector of the other BJT and they stay charged to twice Vcc. >> The current that charges these caps flows though the BE didoe. With >> mosfets that current path is not there so they don't stay charged to >> twice Vcc. I think there might be other differences too. >> >> Can anyone point me to link with some more info on using Mosfets in a >> Royer Osciilator? Is there a way to post a schematic here? > >A quick search on Royer oscillator got me this page: >http://wiki.4hv.org/index.php/Royer_oscillator, >which has one made with MOSFETs. Neither of their circuits have any >caps from collector to base.
The critical bit is L1. The op said that his circuit is "not current fed"; if he has no L1, it's not a Royer, it's a square-wave multivibrator. And if he's trying to resonate the primary, it will be very inefficient. We need a schematic. John
On Jan 24, 4:35=A0pm, dagmargoodb...@yahoo.com wrote:
> On Jan 24, 4:49=A0pm, Kooner <jjkoo...@gmail.com> wrote: > > > Hello, > > <snip> > > > Is there a way to post a schematic here? > > You can post a schematic several ways. > =A0-- =A0You can draw simple schematics in ASCII characters in fixed-widt=
h
> fonts, and post directly to the newsgroup. > =A0-- =A0You can cut, paste, and directly post the (ACSII) contents of an > LTSpice .asc file directly to the newsgroup. > =A0-- =A0you can post a .JPG, .PNG, or other binary image to > alt.binary.schematics.design > =A0-- you can post a graphic to your own website, or a 3rd-party photo > site. > > -- > Cheers, > James Arthur
Ok, thanks. How's this: http://www.flickr.com/photos/58722598@N07/?saved=3D1 - This is part of a schematic from an old design I got my hands on, these are not the original component values but the circuit still works. - The simulation run is from 0 to 8uS. Once it starts to oscillate it doesn't stop. - I probed the base and collector of both transistors and the cap above Q1 (5 traces total). Maybe it's not a Royer but it does oscillate and produce sinewaves. - Notice Vcap (C1) charges to about 9.5VDC and holds. This doesn't happen if I use mosfets. - The other thing I notice is the connection from the 5V supply to the 500K resistors is not needed. The circuit will still oscillate, getting base drive from the transformer. With mosfets I don't get sinewaves, more like squarewaves. It has something to do with caps C1 and C2, they don't charge to a DC level with mosfets. I really hope I can get this thing to produce sinewaves with fets. Jason.
In article <lo1sj6del97obqhjt4likjq88d8ktrn5gm@4ax.com>,
 Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> 
 wrote:

> On Mon, 24 Jan 2011 15:02:50 -0800, Tim Wescott <tim@seemywebsite.com> > wrote: > > >On 01/24/2011 01:49 PM, Kooner wrote: > >> Hello, > >> > >> I have a working Royer Oscillator. This version is not current fed. It > >> is a push push tolpolgy and the LC oscillationis are set by the > >> transformer inductance and winding capacitance. The schematic looks > >> like a multivibrator except the reistors in the collectors are > >> replaced withthe half primaries of the pushpull transformer. > >> > >> This circuit has BJTs and has a sine wave output but I when I replace > >> them with Mosfets the output is square wave. I've been simulating this > >> thing for a week now and can't get the output to be sinewaves liek the > >> BJT version. > >> > >> In the BJT version there are caps connected from the base of one BJT > >> to the collector of the other BJT and they stay charged to twice Vcc. > >> The current that charges these caps flows though the BE didoe. With > >> mosfets that current path is not there so they don't stay charged to > >> twice Vcc. I think there might be other differences too. > >> > >> Can anyone point me to link with some more info on using Mosfets in a > >> Royer Osciilator? Is there a way to post a schematic here? > > > >A quick search on Royer oscillator got me this page: > >http://wiki.4hv.org/index.php/Royer_oscillator, > >which has one made with MOSFETs. Neither of their circuits have any > >caps from collector to base. > > That BJT version is a guaranteed croaker (Needs diodes to limit > reverse Vbe). Did Larkin draw that up ?:-) > > ...Jim Thompson
The first schematic is used for many CCFL drivers, and they never have diodes. I think the error is in the number of windings on the base drive. -- I will not see posts or email from Google because I must filter them as spam
On 25 ene, 04:54, Kooner <jjkoo...@gmail.com> wrote:
> On Jan 24, 4:35=A0pm, dagmargoodb...@yahoo.com wrote: > > > > > On Jan 24, 4:49=A0pm, Kooner <jjkoo...@gmail.com> wrote: > > > > Hello, > > > <snip> > > > > Is there a way to post a schematic here? > > > You can post a schematic several ways. > > =A0-- =A0You can draw simple schematics in ASCII characters in fixed-wi=
dth
> > fonts, and post directly to the newsgroup. > > =A0-- =A0You can cut, paste, and directly post the (ACSII) contents of =
an
> > LTSpice .asc file directly to the newsgroup. > > =A0-- =A0you can post a .JPG, .PNG, or other binary image to > > alt.binary.schematics.design > > =A0-- you can post a graphic to your own website, or a 3rd-party photo > > site. > > > -- > > Cheers, > > James Arthur > > Ok, thanks. How's this: > > http://www.flickr.com/photos/58722598@N07/?saved=3D1 > > - This is part of a schematic from an old design I got my hands on, > these are not the original component values but the circuit still > works. > > - The simulation run is from 0 to 8uS. Once it starts to oscillate it > doesn't stop. > > - I probed the base and collector of both transistors and the cap > above Q1 (5 traces total). Maybe it's not a Royer but it does > oscillate and produce sinewaves. > > - Notice Vcap (C1) charges to about 9.5VDC and holds. This doesn't > happen if I use mosfets. > > - The other thing I notice is the connection from the 5V supply to the > 500K resistors is not needed. The circuit will still oscillate, > getting base drive from the transformer. > > With mosfets I don't get sinewaves, more like squarewaves. It has > something to do with caps C1 and C2, they don't charge to a DC level > with mosfets. > > I really hope I can get this thing to produce sinewaves with fets. > > Jason.
Hello Jason, You are right, this is not a royer circuit. When using BJT, you have a path via the BC diode, so this is a form of negative feedback resulting in lower average base voltage. The DC base current is limited by R2, R3, hence the collector current (via HFE). When using a mosfet, you don=92t have a BC diode and current is only limited by the mosfet itself (and wire resistance). When (for example) Q2 (but now a mosfet) is on, it will not go off. This is because of the high input impedance, the gate voltage will not drop (as happens with the BJT. It will only go off when for some reason the current through the mosfet becomes soo high, that it will go into current saturation (So drain voltage starts to rise). When the drain voltage of Q2 starts to rise, you may have sufficient loop gain so that it will oscillate. You may probe the drain current, it may be high (depending on the mosfet you selected). You can make a royer oscillator sith mosfets, but you need additional components to mimic BJT behavior. Best regards, Wim PA3DJS www.tetech.nl without abc, PM will reach me.