Output Status Monitoring in MEAN WELL DIN Rail Power Supply Series

21.02.2022

One of the most important factors in the operation of any electrical and/or electronic circuit is the ability to monitor its performance. For the power subsystem, this is, first of all, control of the presence of the output voltage. Almost all DIN rail power supplies from MEAN WELL have LED indication for monitoring the status of the main output of the DC OK power supply. The LED, located on the front panel of the power supply, allows you to visually control the presence of the output voltage of the power supply, as well as evaluate its performance.

DC output status LED OK

DC output status LED OK

However, using only LED indication to control the output status is not always convenient, especially if additional control of the power supply output status is required by a separate device or circuit, for example, as part of a smart home system or automation system. In this case, it is better to use power supplies with an additional DC OK output.

The simplest way to implement DC OK power supply status monitoring is to use an active output. The active DC OK output is a tap from the main output of the power supply, where you can get a logic level of 1 or 0, depending on the state of the main output of the power supply (stabilized voltage at + 5V), connect an LED or relay. This method has found its application in low-power DIN rail power supplies of the MDR-10 and MDR-20 series. The resistance of the load resistor or the winding of a low-power relay, depending on the supply voltage through the main channel of the power supply using the MDR-20 as an example, is shown in the figure:

Active DC OK output in MDR-20 series power supplies and how to use it

Active DC OK output in MDR-20 series power supplies and how to use it

The second option for additional control of the state of the output of the power supply to the DIN rail is a relay contact, also called a "dry contact". In fact, another secondary winding is added to the power supply pulse transformer, to which the winding of an electromagnetic relay is connected, the contacts of which are brought to the terminal block for connecting an external control circuit, that is, the contacts of this relay represent the DC OK output. Thus, complete galvanic isolation is provided both from the input of the power supply and from its main output. "Dry contact" is again convenient in that it allows you to use almost any device as a control circuit, with any supply voltage, and not just the one that is on the main output of the power supply.

Block diagram of a power supply with a DC OK relay output and the status of this output

Block diagram of a power supply with a DC OK relay output and the status of this output

Given that to implement such a DC OK status output, additional space is required in the power supply case to accommodate an electromagnetic relay, this method is used only for sufficiently powerful and large DIN rail power supplies - MDR-40 , MDR-60 , MDR-100 , as well as all WDR series power supplies.

For questions related to the selection and use of MEAN WELL products, please contact Meanwell@chipdip.ru .