Increasing 41-740, 41-742, 41-743 Current

    The 410-740, 41-742 and 41-743 PXI power supplies are capable of generating up to 2Amps on each channel. two independent channels are supported in each module.

    Some users require more current form their module, here is how to do it by forcing two channels to current share.

    Current Sharing

    There are a number of schemes intended to allow two power supplies to share a load. Many of these schemes are intended for use with fixed output voltage power supplies, but they do not work well for programmable power supplies like the 41-740, 41-742 and 41-743. The basic problem is that if one channel is set to a higher voltage than the other then the channel set to a lower voltage does not provide output current and its output is being held at a higher voltage than intended. If one channel is accidentally (or due to a fault) set to a different voltage than the other the result can be damage to the power supply. If for example one gets set to 48V and the other to 5V the lower voltage supply will experience a large reverse voltage.

    Doubling 40-740 Current

    The safest way of doubling the current of a 41-740 (or 41-742) is to connect the V+ terminals together via a diode. The diode prevents reverse voltages from appearing at the output of the supply set to a lower voltage.
    The voltage drop of the diode can be corrected for by connecting the the Vsense lines to the summing point (or the load) directly, forcing the two channels to regulate the voltage AFTER the diode.

    The diode must have a voltage and current rating suitable for the task, we would recommend at least 60V and 3A, and should ideally be a schottky diode to minimize the voltage drop across the diode.
    If the two channels are set to the same output voltage they will each be capable of supplying up to 2A to the load. If one of the supplies is incorrectly set to the wrong voltage the diode will block its output and the load will be supplied from a single channel.

    Further Increases

    Further channels can be added to increase the output current capability. Adding channels in series can also be used to increase the output voltage.

    Diagram of PSU connecting 4 channels together to increase current

    Connecting 4 channels of 41-740/2 together to increase current output by a factor of four

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