The switching regulators are approximately 90% efficient at full load. This may or may not require ventilation - depending on the application's enclosure size and power use.

It is permissible to use transformers with a lower AC voltage or a lower VA rating. However, the full rated output power of the power supply may not be realized. In general, the VA rating of the power transformer should be at-least 1.6 times the total supply output power.

If using a DC source to power the unit, the source voltage must be at least 10% above the highest output voltage (not to exceed 36V however). The required DC input power is 10% above the total output power. The negative DC input source should be connected to the output return terminal.

24V, 56VA power transformers, as well as 16V, 40VA and 16V, 20VA wall-cube transformers are available from Ibex Mfg. The 24V, 56VA transformer will allow a supply output power of 30W at +85C or 40W at +45C while the wall-cube tranformers yield 25W and 12W respectively at supply output voltages of up-to 15VDC.

Similar 24V wall-cube transformers are available from distributors for higher supply output voltages.

The supply's DC input can be used for battery backup under some conditions. Application Note 9 discusses this.

The average DC input current (if used) should not be allowed to greatly exceed 3A - especially at high ambient temperatures. Short-term current bursts of up to 5A are permissible.

Voltage Outputs: There are two 3-port terminal blocks on the board - one for each output voltage. There is a voltage adjustment pot located at the base of each heatsink. These may be adjusted in the field if desired (the heatsinks are connected to the RET terminals so a slip of the screwdriver won't cause a problem).

Voltage #1 has two output ports labeled V1A and V1B. V1A is the direct output of the switching regulator and offers regulation of +/- 2% over all combinations of line, load, and ambient temperature variation.

Port V1B has an additional LC filter to provide additional ripple reduction at the expense of degraded regulation. The resistance of the filter is approx. 0.05 ohm. So, for every 1A drawn at the B ports, the voltage will drop by 50mV. This is unlikely to be a problem for most applications.

Likewise, Voltage #2 has two output ports labeled V2A and V2B with the same extra-filtering option.

The negative ports for Voltage #1 and Voltage #2 are labeled RET and are tied together on the board. The two outputs voltages are not isolated from each other. For best results, connect both negative returns to the application's negative power input. The DC input power return (if used) also is connected to the unit's negative returns.

The switching regulators have built-in current limiting at 3.0 - 3.5A. They may be allowed to go into current limit by the application with no damage and no time limit.

Each voltage output can source up-to the maximum current limit (3.0 -3.5A) provided the combined output power of the two voltage outputs is not more than 30W at +85C or 40W at +45C. If the 30W/40W specification is exceeded, the current limit of one or both voltage outputs may be lowered automatically.