Phase detector

T

Tim Williams

Guest
Okay, I've got a Rube Goldberg thing going in my mind...

First of all, I have an SG3524 based driver circuit, running a half bridge
that runs an induction coil.
Driver schematic:
http://webpages.charter.net/dawill/tmoranwms/Elec_SG3524Driver.gif
Half bridge:
http://webpages.charter.net/dawill/tmoranwms/Elec_HalfBridge2.gif
(Cmatch + Ctank = 6.4uF, Lmatch = 35uH, Ltank = 1uH, supply = 110V.)

Well the circuit works as good as I can expect it to at this power level...
what I'm racking my brain on is control. At the moment I manually adjust it
to resonance for maximum power (or above resonance, giving the inverter a
lighter, inductive phased load). As you can imagine... frequency varies
quite a bit depending on load resistance, dimensions and permeability.

What kind of circuit would work here? I was thinking of detecting phase
between the instant the tank reaches peak voltage and the time when the
inverter switches off. At 50-100kHz (the larger model will be lower), that
requires fractional-microsecond pulses, which aren't impossible but I'm not
familiar with the circuitry (storage time doesn't like me..) to handle it.
Then some sort of circuit to measure the time between the pulses and
translate that to a current which controls the 3524's frequency (current
draw from pin 6, which probably goes to a current mirror inside the chip).

Or if you have recommendations for chip(s) I have on hand that do all this
automatically...I'm all ears...(which is basically limited to an MC1391 I
pulled from a monitor, and various 74[LS] chips I have on hand).

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms
 
On Fri, 25 Mar 2005 15:46:51 -0600, "Tim Williams"
<tmoranwms@charter.net> wrote:

Okay, I've got a Rube Goldberg thing going in my mind...

First of all, I have an SG3524 based driver circuit, running a half bridge
that runs an induction coil.
Driver schematic:
http://webpages.charter.net/dawill/tmoranwms/Elec_SG3524Driver.gif
Half bridge:
http://webpages.charter.net/dawill/tmoranwms/Elec_HalfBridge2.gif
(Cmatch + Ctank = 6.4uF, Lmatch = 35uH, Ltank = 1uH, supply = 110V.)

Well the circuit works as good as I can expect it to at this power level...
what I'm racking my brain on is control. At the moment I manually adjust it
to resonance for maximum power (or above resonance, giving the inverter a
lighter, inductive phased load). As you can imagine... frequency varies
quite a bit depending on load resistance, dimensions and permeability.

What kind of circuit would work here? I was thinking of detecting phase
between the instant the tank reaches peak voltage and the time when the
inverter switches off. At 50-100kHz (the larger model will be lower), that
requires fractional-microsecond pulses, which aren't impossible but I'm not
familiar with the circuitry (storage time doesn't like me..) to handle it.
Then some sort of circuit to measure the time between the pulses and
translate that to a current which controls the 3524's frequency (current
draw from pin 6, which probably goes to a current mirror inside the chip).

Or if you have recommendations for chip(s) I have on hand that do all this
automatically...I'm all ears...(which is basically limited to an MC1391 I
pulled from a monitor, and various 74[LS] chips I have on hand).

Tim
Click to expand...

XOR gate!

John
 
TC5081AP Phase Detector from Toshiba
http://www.ajpotts.fsnet.co.uk/ICS/tc5081.htm
 
On Fri, 25 Mar 2005 23:00:36 -0500, "John Walton"
<jdwalton@comcast.net> wrote:

TC5081AP Phase Detector from Toshiba
http://www.ajpotts.fsnet.co.uk/ICS/tc5081.htm
Click to expand...
Amazing! Looks like a poor logical copy of the gating in an MC4044
;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
"John Walton" <jdwalton@comcast.net> wrote in message
news:trmdnSfSl-72_trfRVn-pA@comcast.com...
Basically, the CFB amps drive 1n4148's through 200R -- this clips the sine
wave of both reference and signal to be measured -- each circuit feeds one
side of the transistor array used as a comparator. Phase is proportional
to
the voltage averaged over time.
Click to expand...
Hm, so I can add a current loop toroid to the work coil supply, clip the
signal with two 1N4148's in antiparallel, amplify (hm, rather one 1N4148 and
a B-E junction) to get a "full height" square wave, and send this to a LTP
against clock from the 3524? Does it matter in the closed loop that the
3524 isn't ever at 50% duty cycle?

And that makes a PWM error signal, which can then be averaged as you say and
compared to a control voltage (power level) and sent to drive the frequency
pin, no?

I like... almost uses fewer pins (as discrete transistors) than that 9-pin
SIP alone. ;-)

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms
 
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