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Thread: Open source power pre-regulator

  1. #1
    diysmps Member
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    Open source power pre-regulator

    I'd like to present my first SMPS project of power pre-regulator that can be used in variable/programmable bench power supply as replacement for AC mains transformer or combination of AC/DC converter with fixed output and DC/DC converter used for efficient pre-regulation. Additionally, it provides four bias outputs for powering post-regulator circuit. More details (incl. some measurements) can be found on the project web pages and GitHub repository. Its block diagram is show below.



    The major challenge was to make a converter that could accept (without mechanical switch) wide input voltage and provide wide output voltage in the same time. Therefore a CF-DIC (current fed dual inductor converter) topology has been selected combined with HV synchronous buck. The main controller is LM5041B, that can drive directly CF-DIC section and provide PWM outputs for HV buck driver. Si8233 is intentionally used as a driver to isolate power and signal grounds that simplify e.g. PCB routing and improve circuit stability.
    The converter comes with built-in various protection against overheating (OTP), short circuit and over-voltage (OVP). Additionally, an Active Duty limiter is employed to guard it against fast changes of output voltage programming input that could result in dramatic increase of PWM Duty (for HV buck stage) that could be fatal with high input voltage (i.e. 230 Vac).
    Bias power supply, a QR (quasi-resonant) flyback topology has been selected that provide all necessary power for primary and secondary side of the CF-DIC stage, and connected post-regulator. Choosen VIPer35 controller comes with built-in various protections for improved safety.
    The synchronous rectification is used instead of classical diode full wave rectifications to improve converter efficiency.



    This converter employ few interesting components:

    • SiC MOSFETs and freewheel SiC diode for improved efficiency and lower EMI of the HV buck stage
    • High performance VAC Vitroperm 500F core material with high permeability and high saturation induction that power transformer can be much smaller that one with standard ferrite materials


    Converter's BOM is also available on the GitHub, and all used components can be sourced from the major distributors. Only two components: flyback and power transformer are custom made (that is common case for AC/DC converters) and can be sourced from Feryster (Poland). Shown enclosure is provided by Varisom (Portugal).

    Basic facts:

    • Wide range input: 85 265 Vac, 120 380 Vdc
    • Wide range output: 2.5 52.5 Vdc
    • Output current up to 3 A continuously without additional cooling (e.g external fan) or 5 A with additional cooling (max. power up to ~260 W)
    • Output voltage controlled by tracker circuit (+2.5 V for full scale) or optionally with multiturn trimpot if fixed output voltage is required
    • Cascaded PWM Controller LM5041B (sync buck + push-pull stage)
    • Isolated HV power ground and signal ground for improved noise immunity
    • HV buck section with high performance SiC MOSFET switches
    • High performance VAC Vitroperm 500F core material for power transformer
    • Synchronous rectifier with low R(ds, on) MOSFET switches
    • Active Duty cycle limiter
    • Over-voltage (OVP), short circuit protection and over-temperature protection (OTP) with latched shutdown and opto-isolated open-collector "Fault" output
    • Over-current protection (OCP)
    • QR flyback as bias power supply (VIPer35)
    • Four bias power supply outputs: +6.5 V, -8.5 V and "floating" +12 V / -12 V that can be further regulated with LDOs
    • Compact size (155 x 90 x 45 mm)
    • Weight (with enclosure): 490 g

  2. #2
    .... Silvio's Avatar
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    A very nice project. Congratulations.

  3. #3
    diysmps Member
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    Thanks, please find below a short video about it:


  4. #4
    .... Silvio's Avatar
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    Very versitile and ingenious

  5. #5
    Nice work indeed
    www.diysmps.com & www.Micro-Audio.com

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