Fig. 1: Mosfet pre-regulator and post-regulator prototype


The programmable bench power supply is designed with taking into consideration the following features and requirements:

  • Modular design that allows combining modules with various performance and capability and creation of multiple output solution (min. two channels)
  • Voltage regulation (CV), 10 mV resolution
  • Current regulation (CC), 10 mA initial resolution (possibly improved to 1 mA)
  • Various voltage single range operation (i.e. 0 – 30 V, 0 – 40 V or 0 – 50 V per channel)
  • Various current single range operation (i.e. 0 – 3 A or 0 – 5 A per channel)
  • Minimal overshoot when new voltage or current level is programmed or in marginal cases such as power on/off
  • Min. 15-bit data acquisition resolution
  • Various protection mechanisms: over-voltage (OVP), over-current (OCP), over-power (OPP) and over-temperature (OTP)
  • Pre-regulator circuit for lower power dissipation (using e.g. phase-control or SMPS)
  • Switching frequency synchronization if multiple SMPS are utilized
  • Output enable (OE) circuit
  • Remote voltage sense
  • Simple AC input protection (surge and transient protection)
  • Simple DC output protection (reverse voltage, over-voltage)
  • Serial and parallel connection of the multiple channels
  • MCU based digital control module using Arduino/Genuino boards such as Mega or Due
  • SPI bus for communication with peripherals
  • Galvanic isolation between digital module and power channels
  • Real-time clock (RTC) with supercap/batter backup
  • EEPROM used as a configuration and calibration parameters storage
  • SD-card as an additional storage
  • USB support that can be used for remote control, as a debug console and firmware upload
  • Ethernet support for remote control
  • Local control using TFT touch-screen display
  • Fan-less (“quiet”) operation
  • Basic functionality for e.g. initial testing during assembling phase does not require digital control. It’s achievable by using standard potentiometers and mechanical switches
  • Usage of easy to find components that could be obtain with just single order from suppliers such as Farnell element14 UK or (Transfer Multisort Elektronik (
  • Possibility to house at least dual channel version in affordable metallic enclosure (e.g. Hi-fi 2000/ Economica EP1153220 L 320 x P 200)

The power supply’s modular design gives us more freedom in building functional device. Each module represents one PCB that has to be wired with other boards (PCBs) and components such as main transformer, display, output terminals (binding posts), etc. The following modules is possible to use for PSU building:

Each module will be described in more details in text that follows. Before that a few possible configurations will be presented.

1.1. Single channel without digital control

The simplest possible configuration requires one pre-regulator and one post-regulator module. It represents single channel device that is not programmable and that requires few additional components: two potentiometers for voltage and current settings, one toggle switch for output control (output enable) and two LEDs for CV and CC indications. Pre-regulator require a main transformer with only one secondary winding. The transformer has to be properly rated to provide enough voltage and current for the desired output range (e.g. 0 – 50 V and 0 – 3 A). If no upgrade to enable digital control is planned, and the budget is tight, the whole digital section on the post-regulator module could remain unassembled.

1.2. Dual channel without digital control

Same as above but require four modules in total: two pre-regulators and two-post-regulators. All additional components also has to be multiplied by two. Therefore one will require four potentiometers, two switches and four LEDs. A main transformer with two secondary windings has to be used for ensure isolated and independent operation of each channel.

1.3. Fully featured dual channel configuration

The block diagram of a fully featured power supply is shown on the picture below. It will require six modules in total of which four are as in above mentioned setup. The additional two is used for the digital control: that is Arduino Shield +BP (or just the “Shield” from now on) and auxiliary power supply used for autonomous powering of the Shield. Complete control over both channels is performed using local display with touch screen as an input device and in addition the Shield enables that fully featured remote control is established using serial (via USB) or Ethernet communication.

The remote control is based on a command set that is written in compliance with the SCPI 1999.0 specification that is de facto standard for the middle and high-end commercial power supplies and many other laboratory instruments.



More information about modules used for building the PSU can be found in chapters that follows. A header section with information about module development status was added to simplify progress tracking, for example:


Current version



Completed, ready for production

PCB manufactured


PCB assembled



Yes (Farnell, TME)

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