Features of choosing multi-channel power supplies MEAN WELL

One of the tasks often encountered in practice is to provide power to different functional parts of one device with separate rated voltages, for example, the microcontroller and the logic circuit should be powered with a voltage of +5V, and the actuators (relays, indications, etc.) with a voltage of +12V DC. In this case, in order to optimize the cost of the end device, it is advisable to use power supplies with two or more outputs.

The most popular and sought–after housing-type series are the two-channel RD series, the three-channel RT series, and the four-output RQ series. Among the powerful series with four housing-type outputs, the QP series can be distinguished. A special feature of all these series is their design - the additional outputs are separate taps of the pulse transformer, thereby achieving galvanic isolation between the outputs.

Block diagram of the RT-125 series three-output power supply

Complete separate channel voltage stabilization for such a topology is usually difficult or expensive to provide, which reflects the Cross regulation parameter - the dependence of the output voltage on the other channel(s) on the load on one (main channel). Sometimes the Cross regulation parameter is specified in the documentation, sometimes it is not, and all necessary comments are given in the note.:

Output parameters and their compliance conditions using the RT-125 example

So, using the example of the RT-125 series, it is noted that a sufficiently low voltage deviation is provided only on channel CH1 (provided that the load current exceeds 15% of the nominal value for this channel), the permissible deviation on channels CH2 and CH3 is much higher. Output stability (Load Regulation) is also at an acceptable level only for channel CH1, and has a much larger deviation for channels CH2 and CH3, and this is ensured only when the load on the remaining channels (not participating in the measurement for this channel) is at 60%. When the load level changes, the deviation (i.e. deterioration of output stability) may be even greater. More information about the output parameters can be found here.

To ensure complete independence and stabilization of the output channels, it is advisable to use power supplies with separate DC/DC converters (each on its own channel), which are combined by a single front-end mounted in a chassis (basket) in which separate DC/DC modules are mounted. An example of such series are the NMP series (for a total of 650 and 1200W). A detailed description of the series is provided here. How the configuration is selected and calculated can be found here.

NMP1K2 chassis with separate power supply modules installed

This option of a full power supply is significantly more expensive than the first type of power supplies (RD, RT, RQ, QP and similar series), but it is also designed for high total power, complete channel separation, and each module has additional channel monitoring and control functions.:

Block diagram of the NMS-240 module installed in the NMP chassis

There is also a third option for creating multi–channel power supplies - to use separate power supplies and connect them to a common output in such a way as to ensure the required polarity of each output. In this case, the power supplies can be selected with any power of any series. But the total volume of such a power supply will be the largest, which may be inconvenient for some applications.

The technical specifications are provided in more detail in the Specifications for the series of power supplies, and for questions related to the selection and use of MEAN WELL products, please contact the email address Meanwell@chipdip.ru .