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Technical DC Power Supplies
Information
Accuracy and Resolution
Programmable DC Power Supplies Historically, the DC power supply user turned potentiometers to set output
DC power supplies provide a regulated DC output to power a component, voltage or current. Today, microprocessors receive input from the user
a module, or a device. A power supply must deliver voltage and current interface or from a remote interface. A digital-to-analog converter (DAC)
that is stable and precise, with minimal noise to any type of load: resistive, takes the digital setting and translates this into an analog value, which is
inductive, low impedance, high impedance, steady-state, or variable. How used as the reference for the analog regulator. The setting resolution and
well the power supply fulfills this mission and where it reaches its limits accuracy values are determined by the quality of this conversion and regu-
are defined in its specifications. lation process.
Technical information: DC power supplies
Power supplies have two main settings, the output voltage and the current Voltage and current settings (sometimes called limits or programmed val-
limit. How they are set in combination with the load determines how the ues) each have resolution and accuracy specifications associated with them.
The resolution of these settings determines the minimum increment in
power supply will operate.
which the output can be adjusted, and the accuracy describes the extent to
Most DC power supplies have two modes of operation. In Constant Voltage which the value of the output matches international standards. In addition
(CV) mode, the power supply controls the output voltage based on the to output settings, there are measurement or readback specifications that
Side Text
user settings. In Constant Current (CC) mode, the power supply regulates are independent of the output specifications.
the current. Whether the power supply is in CV or CC mode depends on Most DC power supplies provide built-in measurement circuits for meas-
both the user settings and the resistance of the load. uring both voltage and current. These circuits measure the voltage and
current being delivered by the power supply output. Since the circuits read