Design play/challenge: Phase Shift PWM

If you can stand a nonlinear control curve, you can eliminate the current source...

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Or, if you're picky like me, linearize it...

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Thanks Jim. My guess is that since the modulator is destined to be inside a feedback loop a little non-linearity is OK. I like this offering of yours best. Nicely simple, gets my vote for the prize :)

piglet

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I am concerned about this. If nothing else, I'll need to provide a +/-5 or

10% trim to the current sources/sinks on the respective capacitors. Or trim caps.

Er... when I said "built-up 555", I clearly didn't mean /using/ one... how Slomanesque! ;-)

Anyway, neither of you are even trying for a full >= 180 degree range, which was the original requirement.

This more than exceeds the *range*...

...if not the offset. Which means OUT1 needs to be offset by a constant phase, which is bothersome.

I don't think it's possible to do >180 degrees in less than 2 time constants and four comparators. You need one time constant for the oscillator, one for the phase shifter, and you can get the remaining half cycle of phase shift by comparing balanced thresholds off the oscillator's (as discussed in earlier ideas -- both outputs shift with respect to the reference), or you can always add more.

Or if I take the above circuit and extend it for "differential phase", I need two more comparators and three more RS-F/F. But the 2-and-3 is only if I need the nearly-full-cycle ranges, which I don't if I have a pair. So those can be stripped back to the nearly-half-cycle versions (OR the trigger pulses into the capacitor reset; one comparator detects ramp; comparator clocks D=OUT1 into Q=OUT2). But that's worse because I need one RS and a pair of Ds, but the RS might as well be replaced with a pair of transistors (yay RTL). Which, with the diodes around the cap in this push-pull oscillator, that can be done rather effortlessly, so that's not bad.

That might just do it, hmmm...

Major downside is it needs to be wired for "Class AB" phase shifting, not true "differential phase". Otherwise there's not enough headroom. Which means more op-amps, or transitors (plus temp compensation, i.e., even more transistors), for solving that.

Tim

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Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com

The 555 packs a lot of functionality and enough precision for a lot of real-world use into a few cents, will never go EOL and is quicker to breadboard with than umpteen descretes. It still has its place.

I thought the original impetus came from power supply apps - so 0-180deg range is from min to max and you did say outputs were to be 50:50 square waves. Can't see the need to go above 180deg shift. How is the output power produced by bridge psu with 90deg shift different from a 270deg shift?

piglet

Thanks! ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

My versions _are_ 50:50 and do 0-180deg... are they not? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

All of the examples so far, exhibit one or both outputs /freezing/ beyond the range. In other words, the attached bridge explodes.

You expect the circuit and source to be so stable that a controller can saturate to 179.9 degrees and not one fraction of a volt past that point?

If the controller can saturate to -10 to 10 and 170-190 degrees, with almost

90 to spare off either end, that's actually practical. I'd be fine with way less headroom, but range more or less comes in half-cycles so it has to be extended.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com

On 12/03/2016 08:44, Tim Williams wrote:

This one does nearly 360 deg range with just one RC time constant ...

Version 4 SHEET 1 1776 740 WIRE 1344 -256 1008 -256 WIRE 1056 -192 1008 -192 WIRE 1312 -192 1056 -192 WIRE 368 -144 368 -176 WIRE 864 -80 864 -112 WIRE 976 -80 864 -80 WIRE -80 -64 -80 -96 WIRE 864 -48 864 -80 WIRE 1056 -48 1056 -192 WIRE 1104 -48 1056 -48 WIRE 192 -32 -16 -32 WIRE 368 -32 368 -64 WIRE 368 -32 192 -32 WIRE 672 -16 400 -16 WIRE 832 -16 672 -16 WIRE 976 0 912 0 WIRE 1104 0 976 0 WIRE 1312 0 1312 -192 WIRE 1312 0 1280 0 WIRE 832 16 816 16 WIRE -80 48 -80 16 WIRE 16 48 -80 48 WIRE 288 48 288 32 WIRE 288 48 240 48 WIRE 368 64 368 -32 WIRE 816 64 816 16 WIRE 816 64 368 64 WIRE 848 64 848 48 WIRE 864 64 864 48 WIRE 864 64 848 64 WIRE -80 80 -80 48 WIRE 848 80 848 64 WIRE -16 112 -16 -32 WIRE 16 112 -16 112 WIRE 256 112 240 112 WIRE 368 112 368 64 WIRE 368 112 336 112 WIRE 400 128 400 -16 WIRE 432 128 400 128 WIRE 560 128 512 128 WIRE 688 128 560 128 WIRE 752 128 688 128 WIRE 1312 128 1056 128 WIRE 688 144 688 128 WIRE 752 144 752 128 WIRE 288 176 240 176 WIRE 368 176 368 112 WIRE 368 176 288 176 WIRE 912 192 880 192 WIRE 976 192 912 192 WIRE 288 224 288 176 WIRE 640 224 640 192 WIRE 880 224 880 192 WIRE 1056 224 1056 128 WIRE 1104 224 1056 224 WIRE 1344 224 1344 -256 WIRE 1344 224 1264 224 WIRE -32 240 -32 224 WIRE 16 240 -32 240 WIRE 560 240 560 128 WIRE 608 240 560 240 WIRE 688 256 688 208 WIRE 688 256 672 256 WIRE 752 256 752 224 WIRE 752 256 688 256 WIRE 848 256 752 256 WIRE 608 272 560 272 WIRE 976 272 928 272 WIRE 1104 272 976 272 WIRE 1312 272 1312 128 WIRE 1312 272 1280 272 WIRE 560 288 560 272 WIRE 816 288 816 64 WIRE 848 288 816 288 WIRE 640 304 640 288 WIRE 288 320 288 288 WIRE 400 336 400 128 WIRE 864 352 864 320 WIRE 880 352 880 320 WIRE 880 352 864 352 WIRE 864 384 864 352 WIRE 400 432 400 416 FLAG 288 320 0 FLAG 288 32 P12 FLAG 368 -176 P12 FLAG -80 80 0 FLAG -32 224 P12 FLAG 400 432 0 FLAG 848 80 0 FLAG 864 -112 P12 FLAG -80 -96 P12 FLAG 560 368 0 FLAG 640 304 0 FLAG 640 192 P12 FLAG 864 384 0 FLAG 912 192 P12 FLAG 1008 -192 OUT-PHA FLAG 1008 -256 OUT-PHB FLAG 192 -32 Ramp FLAG 672 -16 Vmodulate SYMBOL Misc\\NE555 128 144 R0 SYMATTR InstName U1 SYMBOL cap 272 224 R0 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL res 352 -160 R0 SYMATTR InstName R1 SYMATTR Value 30k SYMBOL res 352 96 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL voltage -80 -80 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL Comparators\\LT1011 864 0 R0 SYMATTR InstName U2 SYMBOL voltage 400 320 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value PULSE(4 8 20u 1800u) SYMBOL res 960 -96 R0 SYMATTR InstName R3 SYMATTR Value 5k SYMBOL Digital\\dflop 1184 -96 R0 SYMATTR InstName A2 SYMBOL Digital\\dflop 1184 176 R0 SYMATTR InstName A3 SYMBOL Comparators\\LT1011 880 272 R0 SYMATTR InstName U3 SYMBOL Opamps\\LT1007 640 192 R0 SYMATTR InstName U4 SYMBOL voltage 560 272 R0 WINDOW 0 -36 4 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 6 SYMBOL res 416 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL res 736 128 R0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL res 960 176 R0 SYMATTR InstName R6 SYMATTR Value 5k SYMBOL cap 672 144 R0 SYMATTR InstName C2 SYMATTR Value 50p TEXT 22 424 Left 2 !.tran 2m TEXT 992 376 Left 2 ;SED Phase Shift PWM Challenge TEXT 992 416 Left 2 ;360 deg Range. EPW Mar 2016

piglet

[snip]

I pondered something like that myself, but don't you have a synchronization issue between the two D-flops (like flipped phase from one start-up to another)? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Details, details. :)

Yes I suppose you're right, needs POR and suchlike, am just trying to demostrate one possible scheme, I'm sure there are other solutions.

piglet

Tim won't like having a POR >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

He could make one from seven transistors :>

piglet

Bwahahahahaha >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Piglet, Your two-phase scheme rang my chime. Instead of using the comparator outputs to reconstruct square waves, use them to "splay" the sampling points...

(It is left as an exercise for the student to add the OpAmp needed to create {-VREF+3} from {VREF} ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

The JT version, because of reset time, is slightly shy of 180; it works with time delay, though, so an addon pair of PLLs can give you arbitrarily many cycles adjustability by syncing on those edges, and oscillating faster.

A PLL is overkill.

See...

for more variability. This needs modification, changing the control

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Geez, four ICs? What am I made of, money?

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I don't mind actually, because a UVLO and fault latch would be natural additions. But it is extra stuff for basic functionality.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com