LTspice has a few kinds of "ideal" models.  I used both kinds.

 

If you used any "real" diode (one with a part number), there's chances of a few factors that could affect results.

 

The ideal diode "D" follows the Shockley diode law, so it is actually pretty close to an actual silicon diode's behavior, but it lacks capacitance and bulk (ohmic) resistance.  That might be what affected your results.

 

Andy

I didn't use the "ideal" diode so even the minuscule capacitance was causing issues. The LTspice ideal diode is very similar to the XSPICE simple diode code model.

On Thu, Dec 26, 2024 at 08:08 AM, Tony Casey wrote:

Did you try enabling "This is an active load" in the current source properties?

I thought that did something different (shutting off the current source as the voltage approaches zero).  Is there a different explanation?  Can it throttle the current when the terminal voltage exceeds some preset value?

 

Andy

 

On Wed, Dec 25, 2024 at 08:53 PM, Tom wrote:

Yes there are multiple types of "Fully-Differential Amplifiers". There is no set minimum requirements. For the case of feeding a differential ADC, a "true" Fully-Differential OpAmp is generally used.

I  would think that a non-Op-Amp would be needed in that case, perhaps a diff amp with a preset gain of 1 or 2.

 

What is meant by the word "true" in "'true' Fully-Differential OpAmp"?  Is there another kind that is not "true"?

 

Why swapping the outputs works for Fully-Differential amps made with E and G sources is unknown to me. The XSPICE code model also uses G sources and also works when outputs are swapped. The caveat being R1=R2=R3=R4.

Perhaps it is teetering on the brink of instability, and it only remains stable when the resistors are exactly matched?

 

Andy

 

I uploaded Voltage-Clamped-Current-Source.asc which has four five (three four, really) examples of adding a voltage clamp to an ideal current source.  It is not an algorithmic approach, but it does the job.

 

I don't know why you got spikes with your diode and voltage source method.  Did you use the ideal diode "D", or a real diode model?

 

Andy

 

 

 

Yes there are multiple types of "Fully-Differential Amplifiers". There is no set minimum requirements. For the case of feeding a differential ADC, a "true" Fully-Differential OpAmp is generally used.

 

The Delta-Sigma Converter uses the input amp as a differential-summing-integrator. The amp used by the original Author Holger was a XSPICE gain code model. I was having trouble getting my version created from the original netlist to work and changing the amp seemed to help. The "other" changes I made were probably the real reason I finally got the simulation to work.

 

Why swapping the outputs works for Fully-Differential amps made with E and G sources is unknown to me. The XSPICE code model also uses G sources and also works when outputs are swapped. The caveat being R1=R2=R3=R4.

Having issues making a current source with limited voltage compliance for an ideal charge pump in a PLL circuit. The methods of clamping the Source max Vc using a diode and voltage source or Zener diode create spikes which disrupt the loop. VCCS or 2 terminal G source would work. 

4 boost, 1 in-out, 1 buck

 

boost_1, Ne/Nb: RL1 NC, RL2 NC, RL3 NC

boost_1, Ne/Nb: RL1 NC, RL2 NO, RL3 NC

 

boost_2, Ne/Nc: RL1 NO, RL2 NC, RL3 NC

 

boost_3, Nd/Nb: RL1 NC, RL2 NC, RL3 NO

boost_3, Nd/Nb: RL1 NC, RL2 NO, RL3 NO

 

boost_4, Nd/Nc: RL1 NO, RL2 NC, RL3 NO

 

in-out, Ne/Ne: RL1 NO, RL2 NO, RL3 NC

 

buck, Nd/Ne: RL1 NO, RL2 NO, RL3 NO

 

Off topic

 

When I started designing and producing mains stabilizers for the local consumers, around 4 decades ago, I used LM324 with trimmers to activate the relays properly (much like the one discussed here).

 

In my latest designs, I use the old MCU ATmega8A. It ADC pins read both the mains voltage and the output voltage as well. Trimmers are no more needed. I followed two topologies: old conventional and digital.

 

The MCU conventional design takes 1 relay for each boost tap and 1 relay for each buck one, besides 1 relay for protection (connected at the input, not the output as in the old designs). For example, if the transformer has 5 boost taps and 1 buck tap, the transformer has 7 taps (1 for in-out) connected to 6 relays (and the protecting one). Its advantage is that the transformer is cost effective.

 

The MCU digital design takes 4 relays (+1 for protection) to achieve 11 boost steps, 1 in-out, and 4 buck steps, total 16 steps (typical input from 120 to 285 Vac, to output 220 +/- 10V). Similarly, with 5 relays, we get 23 boost steps, 1 in-out, 8 buck steps, total 32 steps. But it is better for the latter one to use triacs instead of relays (that is 10 power triacs instead of 5 relays). Its disadvantage is that the transformer costs more than of the conventional design.  

 

As most engineers are doing, I took advantage of the SMPS availability (say 24V, 1A) whose input can vary from 100 to 240V, to supply my boards. But I had to also design a small circuit to increase this range. By connecting it between the mains voltage and the SMPS input, the range becomes from 70 to 400 Vac.

 

Thanks to LTspice, I was able to test every design before drawing its final PCBs. I substitute the MCU by logic elements.

On Wed, Dec 25, 2024 at 02:39 PM, Bell, Dave wrote:

The boost/buck question depends completely upon the taps of TR1.

I believe there were 5 taps in the drawing, labelled A … E.

If C was defined to be the 220VAC (Phase) input, then there would be two boost taps (D, E) and two buck (A, B).

Almost, but not quite.  One of the pins is the common, leaving you with 4 pins for choosing the input:output transformation.

 

A is the common.  The input voltage may be applied between pin A and:

There is also the straight-through one where input flows to output without passing "through" the transformer (but is also applied between pins A and E so that other circuits receive power).

 

So you get one straight-through, plus potentially five "boosted" outputs, and one "buck" output.  I don't know if all seven combinations are selectable but those are the potential ones.  On top of that, the right half of the schematic disconnects the output, presumably for under/over voltage conditions that can't be corrected.

 

Andy