Electronic Design
  • Resources
  • Directory
  • Webinars
  • CAD Models
  • Video
  • Blogs
  • More Publications
  • Advertise
    • Search
  • Top Stories
  • Tech Topics
  • Analog
  • Power
  • Embedded
  • Test
  • AI / ML
  • Automotive
  • Data Sheets
  • Topics
    - TechXchange Topics --- Markets --AutomotiveAutomation-- Technologies --AnalogPowerTest & MeasurementEmbedded
    Resources
    Electronic Design ResourcesTop Stories of the WeekNew ProductsKit Close-UpElectronic Design LibrarySearch Data SheetsCompany DirectoryBlogsContribute
    Members
    ContentBenefitsSubscribeDigital editions
    Advertise
    https://www.facebook.com/ElectronicDesign
    https://www.linkedin.com/groups/4210549/
    https://twitter.com/ElectronicDesgn
    https://www.youtube.com/channel/UCXKEiQ9dob20rIqTA7ONfJg
    Electronicdesign 6307 Xl ifd150x155 1
    1. Technologies
    2. Power

    Supervisor Circuit Decides When Solar Array Can Power A Load

    March 23, 2011
    Design prevents powering-up a load such as a microprocessor with a solar array when available light is insufficient to sustain operation.
    Giovanni Romeo

    Electronicdesign Com Article Power Supervisor Circuit Decides When Solar Array Can Power A Load
    1 of Enlarge image
     
    Electronicdesign Com Images Spacer

    Fig 1. The solar array supervisor includes a dummy load greater than the real load to make a correct determination of when the array can power the load.

    Electronicdesign Com Images Spacer

    Fig 2. D1’s zener voltage and Q3’s Vbe determine the threshold for when the solar array can power the load successfully. The response in Figure 3 was obtained by using a 180-O dummy load.

    Electronicdesign Com Images Spacer

    Fig 3. The circuit was tested with a typical load while the light on the solar array was varied from 0% to 100% and back to 0% (a). The expanded detail (b) shows that the supervisor provided a 10-ms rising edge on 5 V at the regulator’s output.

    The performance of solar-powered electronic devices may suffer in twilight conditions. In particular, microprocessors often used to perform solar power conditioning (such as in maximum-power-point trackers) do not like unstable power or smooth edges on power-up. The solar array supervisor described here helps with this problem by offering power supervision at the cost of only three transistors.

    The circuit connects the microprocessor to the panel when the array can power it and disconnects it when the array cannot power it. Because an unloaded solar array supplies a high voltage even in poor lighting, the supervisor circuit employs a dummy load greater than the real load (Fig. 1). This allows the threshold and hysteresis block to make a proper measurement. When the array reaches the correct voltage threshold, the supervisor switches it to the real load.

    Zener diode D1 defines the threshold (Fig. 2). The difference between the real load and the dummy load, which must drain more current than the load, determines the hysteresis. The schematic shows an example of an expected load, a linear regulator (7805) used to power a microcontroller and loaded by a 150-Ω resistor.

    When the input from the solar array is below the threshold (D1’s zener voltage plus Q3’s Vbe), Q2 is on and the panel is loaded by the dummy load, R5. When the input exceeds the threshold, Q3 shuts off Q2, disconnecting the dummy load. This raises the voltage on Q1’s base, supplying power to the load. Because the load is lighter than the dummy load, the voltage on the solar array increases, as does the current on Q3’s base. Thus, the circuit acts like a trigger, confirming the reached condition.

    Figure 3a shows the circuit’s performance when connected to a small solar array (0.5 A shorted, 19 V open), while the light was varied from 0% to 100% and back to 0%. A 100-µF capacitor was placed at the input, and the output load was a 7805 with 10-µF capacitors at its input and output. The solar array supervisor delivered a 10-ms rising edge on 5 V at the regulator’s output (Fig. 3b).

    Continue Reading

    How Edge Processing Enables Next-Gen mmWave Scanners

    Allegro to Supply Current-Sensor ICs for EV Traction Inverters

    Sponsored Recommendations

    Designing automotive-grade camera-based mirror systems

    Dec. 2, 2023

    Design security cameras and other low-power smart cameras with AI vision processors

    Dec. 2, 2023

    Automotive 1 TOPS vision SoC with RGB-IR ISP for 1-2 cameras, driver monitoring, dashcams

    Dec. 2, 2023

    AM62A starter kit for edge AI, vision, analytics and general purpose processors

    Dec. 2, 2023

    Comments

    To join the conversation, and become an exclusive member of Electronic Design, create an account today!

    I already have an account

    New

    Securing Data in the Quantum Era

    Celebrating Field Engineers: The Unsung Heroes of Innovation

    Checking Out the NXP Hovergames NavQ Plus

    Most Read

    MEMS Mirrors: The Next Big Wave in MEMS Technology

    Altech Corporation Products for Electronic Design

    Partnership Develops Coherent Detection-Based LiDAR Platforms


    Sponsored

    How innovative packaging can drive higher power density in load switches

    Voltage reference selection basics

    Power tips: Iq (quiescent current) and light load efficiency

    Electronic Design
    https://www.facebook.com/ElectronicDesign
    https://www.linkedin.com/groups/4210549/
    https://twitter.com/ElectronicDesgn
    https://www.youtube.com/channel/UCXKEiQ9dob20rIqTA7ONfJg
    • About Us
    • Contact Us
    • Advertise
    • Do Not Sell or Share
    • Privacy & Cookie Policy
    • Terms of Service
    © 2023 Endeavor Business Media, LLC. All rights reserved.
    Endeavor Business Media Logo