What is different with active current sharing?

As Redundant Solutions usually are offered two standard power supplies in parallel operation with external decoupling diodes and maybe fault relays. This will offer already a much higher protection against supply failure than a single unit. But what will happen? The two units are voltage controlled at the output and this must result in one unit operating at full load, while the second unit will operate at no load. So now the full-load unit will age much faster and fail probably already early. At this point now the no load unit has to take over the full load in a very short time. And at this point in time this unit has for the first time to take load. Probably this will work smoothly. But if for any reason this unit is not able to take full load, you will not know this until the first unit will fail.
In addition the external decoupling diodes are often cause of trouble. In many cases lowest cost diodes with very low life time are selected and their failure will not be detected (because they are not integral part of the supply unit). If diode A fails, output voltage of the power supply unit A will rise by the diode voltage drop and this unit will take over the full load. So probably the supply unit with the failed diode will fail first and if short to ground will lead to system failure.
This is why we believe, that active current sharing is a safer solution.
If you have 2, 3, 4 or even 5 units operating at the same current your risk of supply failure is virtually zero.
The decoupling diodes are high quality O-Ring diodes and they are integrated into the supply unit and their failure will be detected.
 

A short example:
If your 24V power supply demand is 300W (12A)
 -> with 3 x 150W (6A) units you are already redundant
 -> but with 4 x 150W units you are triple redundant;
and this at a very affordable cost, as you can see above.
TRICONEX is using this solution e.g.
 
 
 

 ... more Details:

Since more than 25 years TRACO is specialized in design and manufacturing of high quality industrial switching power supplies. TRACO is European market leader for DC/DC converters and one of the leaders for AC/DC power supplies. Oem customers include Yokogawa, GE and Triconex.

General Features TIS Series:

• Switch Mode Power Supplies for harsh Factory Floor Conditions
• Easy Snap-On Mounting on DIN-Rail
• Low Profile Case
• Low Ripple and Noise
• 2 Year Product Warranty

Technical Details

• Input voltage range: 93 - 132 VAC / 187 - 264 VAC (user selectable)
• Regulation: Input variation: ±0.2% Load variation 10-90%: ±1.0%
• Ripple and noise (20 MHz BW):  <50 mVpk-pk
• Output current limitation: 110% Iout typ.
• Overvoltage protection: 140% Vout typ.
• Efficiency: to 93%
• Operating temperature range: -25°C ... +70°C
• Reliability, MTBF (MIL-HDBK-217E): >200'000 h at +25°C
• EMI suppression: EN 55011-B, EN 55022-B, FCC part 15 level B
• Noise immunity: EN 50082-2
• Safety standards and approvals: UL/cUL1950 recognized, UL/cUL 508C listed, UL/cUL 1604 listed, IEC/EN60950, CB-scheme
• Mounting: Snap-On mounting on DIN-Rail 35 mm (as per EN 55022) or chassis mounting (with mounting kit MK)
• Connection: Plugable screw terminals (included) TIS 600: Screw terminals