Electronic – Current flow priorities in PSU / PSU review

currentdiodesmicrocontrollerpower supplytransistors

Being an electronics hobbyist, I'm having quite a challenge to design a PSU, which must run both on batteries (during the night time) as well as on Solar energy (daytime). The device is intend to run 3x brushless motors daily, while in night-time it should keep the telemetry alive.

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What I'm particularly worried about the design:

  • a) Is there anything I could improve about the common-ground design?
    The logic-level transistors sit on the low-side, while I must monitor
    voltage levels of both – the battery and the Solar array
    simultaneously. My common ground solution looks like a poor-mans
    approach, since voltage drop in the circuit is significant even with
  • b) what's the best method of sucking all the current out of Solar
    cells, while prioritizing the 3V & 5V devices over the motors &
    charger? The transistors introduce huge energy waste due to heat
    while in ohmic region.

The components chosen:

  • transistors: IRLZ44N and MTP3055VL
  • for gate controll I've chosen a digital potentiometer: MCP4261
  • uC: Atmega328P
  • voltage sensing via MUX: CD4067BE
  • current sensing via HALL: ACS712

Best Answer

You may want to consider how the IC boost converters for PV panels work, such as the SPV1020 using high side switching and common grounds. The MPPT function shunts the PV to sense voltage drop under a pulse load to detect the power available (Interrogate & Observe algorithm). Considering all the modes of operation, with monitoring & protection circuits and losses is not a trivial design. You have a done a good job in your block diagram, but I agree more work still is needed to reduce the switching losses on your common ground. ( Is that a positive ground?) Diode losses can be reduced by using higher voltage batteries and lower currents.

STMicroelectronics SPV1020 PowerSSO-36 package for ceramic caps and 4 phase current switches. $14 a pc. 9A max 98% eff max.

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links: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00275733.pdf


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