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EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference) are unwanted electromagnetic energy that pollutes the environment and can affect the operation of other equipment around it. It can be radiated into the air or conducted over system power lines. EMC (Electromagnetic Compatibility) is the ability of a system to function in a high EMI/RFI environment and the ability to limit its own EMI/RFI output. The International Special Committee on Radio Interference (CISPR) makes recommendations for EMI/RFI suppression to nationalized EMC regulatory bodies such as the Federal Communications Commission (FCC), and the German VDE. The FCC is the governing body in the U.S., and VDE is widely recognized in Europe as well as worldwide. Astrodyne TDI power supplies are designed to meet the EMC regulations directed by these governing bodies.

The level of AC voltage on the output of a power supply is expressed in millivolts peak to peak, or RMS, at a specified band width. Ripple and Noise is dependent upon output voltage as specified per the model. It is measured directly at the pins/screw terminals at nominal load, 25°C ambient. Typical specifications call for a 0.1-uF bypass capacitor at the measurement point and measuring equipment set to 20 MHz bandwidth.

Underwriters Laboratories (UL) develops minimum safety standards for commercial electronic products in the U.S. Some states have made these standards legal requirements, though most are voluntary. UL does not "approve" equipment or systems, because this may be construed as a recommendation. Instead, it "recognizes" components and power supplies, and "lists" systems and end-use equipment, thereby attesting this equipment is in compliance with published standards. The more common UL standard related to power supplies is, UL62368-1 - Standard for Safety – Audio, Visual, and Communication Equipment. The Canadian Standards Association (CSA) is the governing safety standards organization in Canada, and compliance is mandatory. The CSA standard for electronic equipment (CSA 22.2) is very similar to UL62368-1. Two of the more common CSA standards related to power supplies are:

1) C22.2 No. 950 - Safety of Information Technology Equipment 2) C22.2 No. 234 - Power Supplies

The International Electromechanical Commission (IEC) is a group of technical committees from member countries, including the U.S., which based on the consensus of opinion, publishes specifications for varying subjects. It is recommended that the National committees adopt these standards. The specification published by IEC of interest to power supply manufacturers is:

IEC 950 - Safety of Information Technology Equipment including Electrical Business Equipment

German Safety Laws are internationally recognized electrical standards highly regarded throughout Europe and the rest of the world. Both VDE and TUV are authorized to test and certify products to these standards. The common standard related to power supplies is:

IEC 950/EN60950 - Safety of Information Technology Equipment including Electrical Business Equipment (Formerly VDE 0806)

Most Astrodyne TDI products are certified to applicable UL, CSA, and IEC/TUV standards. Astrodyne TDI recommends that you refer to the detailed specification sheets provided in downloadable PDF format on this website for standard information including file certification numbers.

All Astrodyne TDI converters are specified to operate within a given range of ambient or case temperatures expressed in degrees-Centigrade. These are the temperatures that the supply may be utilized safely in and perform to other posted specifications.

Exceeding these temperatures diminishes the capability of the supply to deliver the full load current and may damage the supply. The "Derate Curve" section of the specification sheet illustrates how much power the supply can deliver outside its Full Load Operating Temperature Range.

Astrodyne TDI recommends that "derating" the power supply be considered in applications where the ambient temperature may exceed the recommended Full Load Operating Temperature Range. Other recommendations to consider are:

For natural convection cooled supplies, providing forced air across the supply (18-20 CFM is typical)
Heat sinking to a Metal Chassis
Using Finned Heat sinks

Connecting power converters in parallel for power redundancy is an acceptable practice.

The converters must have their outputs connected in parallel through two diodes. Each converter must be capable of driving the full load. The diodes permit one output to fail without affecting the other.

Contact Astrodyne's Technical Support department for further information.

Unless the power supply is specifically designed for parallel operation, parallel operation is not recommended. Two output voltages from fixed output converters will not be exactly equal.

The converter with the higher output will try to provide the full load, causing it to go into current limit. The second supply will then do the same. Even if an adjust function is used to set the outputs, any drifts with time and temperature will cause the same reaction.

Astrodyne recommends that you refer to the detailed specification sheets provided in downloadable PDF format on this web site, or Contact our Technical Support department.

Series Operation Astrodyne power converters can be operated with the outputs connected in series. However, it is important to note some limitations:

1. The output of one converter could affect the feedback loop of another.
2. The ripple voltage of the outputs will be additive.
3. The total combined output voltage should not exceed the working breakdown voltage of any one of the converters.
4. Reverse bias diodes should be utilized across the output of each supply to protect each output from the reverse voltage of another.Contact Astrodyne's technical support department for further information.

A number of Astrodyne Power Supplies and DC/DC converters offer a Logic Level Inhibit operation where Logic "1" = On, and Logic "0" = Off. Most are designed to be operated by pulling the ON/OFF ("Control") Pin low (Minus input or Output Return in some cases) to inhibit converter operation. If this function is not utilized, the Control pin may be left floating, as it is pulled high internally. Astrodyne recommends that you refer to the detailed specification sheets provided in downloadable PDF format on this web site.

All of Astrodyne’s converters offer some form of Output Current Limiting; an output protection feature that limits the output current to a predetermined value in order to prevent damage to the power supply or the load under overload conditions.

Some supplies are automatically restored to normal operation upon removal of the overload condition, and some require re-powering of the input. Astrodyne recommends that you refer to the detailed specification sheets provided in downloadable PDF format on this web site.

Forms of current limiting are:

Fold back Current Limiting

Designed to linearly decrease both the output voltage and current to a level that is safe for the supply and the load.

Constant Current Limiting

Allows the output current to remain stable, but reduces the output voltage to a level that permits the safe operation of the supply.

Fold back Current

In effect, Shutdown cuts off the output to the load by shutting down the output voltage and output current.

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Astrodyne products carry a 2-year warranty (from date of shipment) against defects in material or workmanship. Astrodyne will repair or replace, at its sole discretion, any product returned and found to be defective. To assure proper handling and credit, all returned products must have a Returned Material Authorization (RMA) number. Please contact the factory at (908) 850-5088 to obtain an RMA number prior to returning any product. Product returns without an RMA number will not be accepted. Astrodyne is not responsible for products returned without an approved RMA number. The customer is responsible for return shipping charges, Astrodyne will assume shipping charges for repaired/replaced products back to the customer. Failure Analysis Reports are available upon request at the time of RMA issuance, at an additional cost of $150.00 per RMA. To facilitate handling, please have your work order or invoice number at hand when contacting the factory for an RMA number. Please mark the RMA number on the outside of the shipping box/label for easy recognition.

In some instances, an application may require a specially designed power supply. This special product may be as simple as a slightly modified output voltage, or may require a totally custom design from "the ground up". Astrodyne has developed and provides a wide variety of custom products to many of our customers. In some cases, one of these existing "specials" may meet your specific requirements. To better help us recommend the best product solution, we suggest that you fill out the Special Product Request form within this site. Our design engineering group will review and respond immediately with a solution to meet your requirements. Or, if you prefer, contact our Technical Support engineers at (908) 850-5088 to discuss your special product needs.