Generally, which type of switching regulator has more losses, lower efficiency: CC or CV?

For comparison, assume same power watts.

 

Generally, which type of switching regulator has more losses, lower efficiency: CC or CV?

For comparison, assume same power watts.

All else being equal, they're pretty much the same, efficiency-wise, except of the extra power dissipated by the current-sense resistor in a CC regulator.

 

All else being equal, they're pretty much the same, efficiency-wise, except of the extra power dissipated by the current-sense resistor in a CC regulator.

Even during transients?

 

Even during transients?

I don't know what you mean. Provide an actual use case, maybe show some schematics. Identify the source and magnitude of such transients. What is your end goal here?

One thing I know for sure: my response above stands even during full moons and leap seconds, so you need not ask about those.

 

which type of switching regulator has more losses, lower efficiency: CC or CV?

The power parts for both regulators are the same. The only difference is how the error amplifier works.

 

Even during transients?

Why do you think transients would significantly affect efficiency, since they are, by definition, short?

 

All else being equal, they're pretty much the same, efficiency-wise

I asked because my understanding is that the larger the difference between Vin and Vout, the harder the converter has to work. True?

My example might be incorrect:

Assume Vin = 1V @ 100A available = 100W available.

Converter:
- CV: Output 100V, load is drawing 0.5A (0.5A reserve)
vs
- CC: Output 2V, load is drawing 25A (50A reserve)

You'd expect similar efficiency?

except of the extra power dissipated by the current-sense resistor in a CC regulator.

Normally, that would be rather small compared to the power-path, correct?

 

How do you get from:

All else being equal...

To:

Converter:
- CV: Output 100V, load is drawing 0.5A (0.5A reserve)
vs
- CC: Output 2V, load is drawing 25A (50A reserve)

With the conclusion that:

You'd expect similar efficiency?

?

 

Normally, that would be rather small compared to the power-path, correct?

The current sense resistor is in the power path, and dissipates I²R.

Is it small? How the heck would I know?

Does it reduce overall efficiency? Yes.

 

the larger the difference between Vin and Vout, the harder the converter has to work. True?

For a linear regulator the heat loss is larger with increased Vin-Vout.
There are many different types of switchers. Generally speaking, they don't care.

My example might be incorrect:
Assume Vin = 1V @ 100A available = 100W available.
Converter:
- CV: Output 100V, load is drawing 0.5A (0.5A reserve)
vs
- CC: Output 2V, load is drawing 25A (50A reserve)

I don' t understand. I will assume " Vin = 1V @ 100A available = 100W available" is how the current is measured. No one in their right mind will make a current measuring circuit that eats up 100 W. I have made many LED CC power supplies, and we often used 0.1V for feedback for at 1A load. At 100A I would use a Hall sensor that has about zero voltage drop. There are other ways of measuring current. One is to look across the resistive part of an inductor which is in the switcher. This way adds no heat loss. Another method I use is to watch the voltage drop across the power MOSFET in the switcher. While there are some errors in the measurement it also does not add power loss.

I do see your point that measuring current might take some small amount of power. In the same way measuring voltage takes a small amount of power.

 

To compare similar cases:

A CV delivering 0.5A at 100V is going to have very similar efficiency to a CC delivering 0.5A at 100V.
A CV delivering 25A at 2V is going to have very similar efficiency to a CC delivering 25A at 2V.

The differences will be due to differing feedback processes, largely trivial.

 

Generally, which type of switching regulator has more losses, lower efficiency: CC or CV?

For comparison, assume same power watts.

Hi,

If you looked into line-tied solar powered converters, you would find that they operate in CC mode and the efficiency can be fairly high. When I worked in the industry, we made high power synthesized pure sine wave converters that did this and reached upwards of 90 percent efficient. We also made plenty of high power synthesized pure sine wave converters that worked in CV mode, also in the neighborhood of 90 percent efficient, and that was a long time ago.

Transients are not usually considered part of the efficiency spec. The only catch is that if they happen very often there may be a significant effect. Then it would depend on the design and type of load. However, if transient operation was part of the requirement, then engineers would take that into account and come up with a way to mitigate that as well in order to keep the efficiency within reason.
This would probably be a rare case, but then life is full of rare cases so we can't rule anything out

In the converter industry the efficiency is usually measured at constant half load and constant full load, without any real concern for transients in most cases. Power consumption with no load is also often measured. For the determination of stability however, transient analysis and transient measurements are a HUGE part of the design and testing.