Power supplies for AS-Interface

General design of the AS-Interface power supplies
Note: The "ground" connection to the system earth must always be as short as possible.

AS-Interface power supplies are part of the necessary and most important components of an AS-Interface system.

AS-Interface power supplies generate a stabilized DC voltage of 30 V DC with a high constancy and low residual ripple. They work in the same way as primary switched-mode regulators.

Data and power are always transmitted simultaneously via the AS-Interface two-wire cable. For this reason, AS-Interface power supplies must also ensure data decoupling in addition to supplying the AS-Interface system.

For this reason, standard power supplies must not be used for the supply of an AS-Interface system.

AS-Interface power supplies supply the electronics of the system (AS-Interface master, AS-Interface modules) and all connected sensors. Depending on the power requirements of the AS-Interface system, graduated power supplies from 2.4 to 7 A are available.

Please note that there are different power supplies for the sensors and actuators.

The power for the actuators (outputs) is usually not supplied by the AS-Interface cable. This must be done by a separate load power supply unit which must be connected via a separate cable (e.g. black AS-Interface flat cable). It can also be used to implement corresponding emergency stop circuits.

If an auxiliary power supply is required in addition to the AS-Interface voltage, the very compact combination power supply unit with 1 x 30 V DC and 1 x 24 V DC can be used.

If so-called double masters are used, the dual power supply unit with 2 x 30 V can be used.

Performance characteristics:

• high efficiency
• low residual ripple
• short-circuit proof and stable at no load
• overvoltage protection at input
• small dimensions
• low weight
• simple and fast assembly

All AS-Interface power supplies have an AS-Interface certificate. Power supplies with UL, CSA, and ship construction approbation are available for worldwide use.

Note: An additional external infeed (AUX POWER) of 20 to 30 V DC is required for the supply of the output circuits. The additional infeed must comply with VDE 0106 (PELV), protection class I.

Earth fault detection

“... earth faults in control circuits must not result in unintended startup or dangerous movements of the machine nor must they prevent the machine from stopping (EN 60 204, Part 1 or DIN VDE 0113)”.

To fulfill these requirements, the AS-Interface earth fault detection module or power supplies with earth fault detection are used. These modules permit earth faults in AS-Interface systems to be safely detected and signaled.

The following earth faults are recognized:

• AS-i ”+” earth fault
• AS-i ”-” earth fault
• Earth faults of sensors and actuators which are supplied by the AS-Interface voltage.

One module for each AS-Interface system is sufficient.