Switched Mode Power Supplies (SMPS)

[Cristi]

Triplej: is hard switched, I will check and correct the mistake.

DJNUBZ: about 15,000uF for the 48V version. you need single or dual rail ? if single rail, chose SMPS500RS with heatslug instead of heatsink and install the heatslug on the housing for better cooling.

[Cristi]

Riileywc: SMPS500R/RS can deliver up to 200W continuous, long term power without forced air cooling. SMPS500RS with heatslug and installed on the housing as heatsink can deliver up to 300W. SMPS800RE can deliver up to 400W, +-60V and +-72V versions. or up to 300W the +-32V or +-40V versions, with convection cooling only. SMPS300RE +-45V to +-60V can provide up to 140W.
using the data above, please consider which is the most appropriate power supply for your application, keep in mind that the max. power required by the amp to be within the power range which the smps can deliver.

[DJNUBZ]

cristi I plan on using the SMPS with a Zen v1. I know the single rail 48V version will work for me (not sure if the noise is low enough for such a circuit but I guess I will find out). what I would still like to know is if I could us a dual rail 24V SMPS and still make it work. The reason for this is that I have more use for a dual rail 24V smps then a 48V smps, if it turns out that I don't want to keep using the smps with the zen. Is there any problem with this?

[Blt258]

Hi all

Cristi i have purchased 2 x Ta3020v3k as the begining of my home theatre system i am looking at running a PC based active Xover 7.4 S/S system i am planning on running 12 of the 3020's in 2 or 3 enclosures based on your following answer
what SMPS would you recomend?

thanks in advance

PS. love your site and all its information

[HNCadet]

Cristi,

Still awaiting several requests for answers on the SMPS500R-24Single supply and I have yet another.

I see where a Secondary voltage output of 12V states its capable of 500ma. I have a need for 600ma(continuous) on this circuit. Is this too high, OR can I specify the secondary Voltage at a higher number for a "custom supply"?

[4real]

I'd like to know if it would hurt performance if one would add additional buffer caps to a SMPS (like the A1000SMPS). 10.000 of 20.000 per rail for instance?

[Cristi]

Blt258, I send you mail.

HNCadet, sorry for waiting, is really difficult to have access to real world internet from my location, and recently I can only post on the forum when I'm outside cxina. I wrote here the reasons: Forum Accesibility Issues

The value of 500mA for aux. voltage is the average, not the maximum. the linear regulator which ensures regulation from a higher voltage generated from an aux. winding is capable to deliver 1A. If the current is higher, the dissipation will be higher as well, as a product of (Vin-Vout)*I. Currently the transformer aux. winding provide 20-24V but the transformer can be made with a lower voltage aux. winding, of 16-18V so the dissipated power will be lower, as the difference voltage will be lower. Also need to consider that for stable operation, the main output must be loaded with at least 50-100mA while the current demand from aux. exceed 200mA to keep the SMPS within continous mode, not burst mode. Usually this is done by default, as any amplifier power stage quiescent current is at least 50-100mA. In extreme cases, a 5W 1K resistor can be added across the V+ and GND of the main output.

4real: All the power supplies are fitted with large capacitors, usually thousands of uF for 500W SMPS and up, and at least 1000-2200uF each for lower power SMPS like SMPS200QR SMPS240R or SMPS300R(E). these values are much more than necessary for any conventional SMPS, where usually values of hundreds up to one thousand uF are used. But considering that these power supplies are made for audio amplifiers use, and some amplifiers, especially switched ones, class D and T require large capacitance to reduce bus pumping, the caps used are the largest. There are two things which can affect a power supply if the added caps are even bigger:
1. the OC protection might trip during turn-ON sequence if the capacitors are excessively large and require huge current to charge up to their nominal voltage,
2. the control loop stability for regulated type power supplies might be affected if the caps are much larger and the smps can become unstable in some particular working conditions.

For A1000SMPS the maximum recommended capacitance is about 6800uF for +-72V, 10,000uF for +-45V to +-60V and can go up to 22,000uF for lower voltage versions. There is a selection menu for capacitors on the order page for this power supply, and chosing the largest caps is almost always enough for most demanding applications.

[4real]

Thanks for the answer Cristi, that is very clear! I won't add any capacitance other than the smaller caps on the amps.

[Cuda]

Originally Posted by Cristi

For A1000SMPS the maximum recommended capacitance is about 6800uF for +-72V, 10,000uF for +-45V to +-60V and can go up to 22,000uF for lower voltage versions. There is a selection menu for capacitors on the order page for this power supply, and chosing the largest caps is almost always enough for most demanding applications.

Hi Cristi

So Ta3020 V3 amp with 18000uF ELNA on board could not be used with SMPS800R 60V ?

Thanks

[Cristi]

It can be used if the soft start time is increased otherwise the overcurrent protection might trip.

Some ppls keep asking me by mail why the OC protection can trip if larger capacitors are used, especially if connected to a power hungry amplifier (high quiescent current) as this does not happen with their previous configuration, mains transformer, rectifier bridge, capacitors. The answer is: if the capacitance is much larger than the maximum capacitance allowed for safe and reliable start, the following phenomenon will happen: the soft-start period allows the power supply to start with limited output power capability, thus slowly rising the output voltage to nominal value. This soft start period is finite and last around 100-200ms. Just enough to fully charge the stock capacitors. If larger capacitors are used, the soft-start will ramp-up the output power with the same pace but the capacitors will demand a higher current than the power supply is able to provide to follow the output voltage while charging. then the power supply will enter in OC protection, SMPS will shut-down for a small amount of time, typically one two seconds, and the cycle will repeat with the power supply being reset to minimum output power capability and again slowly ramp-up towards maximum power. BUT.... there's always a butt... if the amplifier or any load connected to SMPS quiescent current is high enough, this will discharge the fatty capacitor which was just about to be charged and at the next soft-start cycle the power supply will have to start-over, because the capacitor was discharged in during the interval when the SMPS was shut-down due to OC condition.
If I would have to make a comparision, is like we try to fill a large bottle with water (capacitor) with a spoon (soft-start) while the bottle has a tiny hole at the botom through the water leak-out (amplifier quiescent current). we can't fill-it as fast as it leaks. Moreover, the power supply trying to start with a killing charge hanged at the output might eventually fail because the very first moment of the start-up the transistors are working in hard-switched mode (with all the related issues of the regarding the body diode and cross-conduction) for few cycles till the converter starts up to steady state. This opperation mode is normal, is described in many papers, and is better to be avoided, thus many conventiona LLC converters would have latched OC protection just to avoid this scenario.