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R&S®Essentials | Power supplies fundamentals

Power supply in series vs. parallel

Authors: Elizabeth McKenna, R&S®ESSENTIALS Product Manager and Paul Denisowski, Test & Measurement Expert

Many DC benchtop power supplies offer multiple channels that can operate independently or be combined to enhance performance. You can achieve higher output or voltage by configuring these channels in series or parallel.

Why combine power supply channels?

When working with power supplies, you may encounter setups requiring higher output than a single channel can provide. By connecting power supply channels in series or parallel, you can boost voltage or current to meet specific testing demands without additional equipment.

Connecting in series vs. parallel

There are two ways power supply channels can be combined:

Connecting the channels in series increases output voltage.
Connected the series in parallel increases output current.

These connections are typically made externally, but some power supply models, such as the R&S®NGA100, support serial channel fusion, which connects channels internally for a streamlined setup.

The only requirement for connecting channels is that the channels must be floating and galvanically isolated:

Floating: channels are not connected to the common instrument ground
Isolated: channels are independent of each other with no current flow between them

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Power supply in series vs. parallel

Connecting power supplies in series

Series operation allows for higher output voltage. To connect power supply channels in series, you would link the positive terminal one channel to the negative terminal of another. These channels can be within the same power supply, but you can also connect the channels of separate power supplies.

In this setup, the output voltage would be a combination of the two channels, and the circuit current would remain unchanged. For example, if each channel output 25 V, connecting four channels in series results in a total of 100 V. Here, it is important to ensure that you do not exceed the maximum voltage to ground rating of each channel.

Connecting power supply channels to get 100 V

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Connecting power supply channels to get 100 V

Connecting power supplies in parallel

Parallel operation allows for higher current. To connect power supply channels in parallel, you would link the negative terminals of the channels together to create a common negative connection and the positive terminals together to form a common positive connection. These channels can be within the same power supply, but you can also connect multiple power supplies in parallel.

In this setup, each channel’s current adds up, while the voltage remains constant across the load. For instance, connecting four channels each set to 2 V with a maximum output of 10 A results in a 2 V output and a combined current capacity of 40 A.

In parallel configurations, load sharing helps prevent overloads on any single power supply, ensuring an even distribution of current.

Example of power supply parallel operation

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Example of power supply parallel operation

Summary

There are two ways power supply channels can be connected: in series and in parallel.
Channels must be floating and galvanically isolated to be connected.

For higher voltage, you can connect channels in series.
- The total output voltage is the sum of the channels’ individual voltages.
- The current is unchanged.
For higher current, you can connect channels in parallel.
- The voltage is unchanged.
- The total current capacity is the sum of the channels’ individual currents.
In parallel configurations, load sharing helps prevent overloads on any single power supply, ensuring an even distribution of current.

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Power supply in series vs. parallel

Why combine power supply channels?

Connecting in series vs. parallel

Connecting power supplies in series

Connecting power supplies in parallel

R&S®NGE100

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R&S®NGA100