MK Dynamics

Solar Power Devices - Dual Diode Box


Description

Introduction

The item is an electrical box which selects from two independent DC power sources. The two sources are diode-OR'd by Schottky diodes, and the voltage that exceeds the other in addition to a power Schottky diode voltage drop supplies power to the outlet. The presence of voltage is indicated via LED, and the level of current flowing through the box, is shown via LED bar graph. Each bar graph element corresponds to 1A of box load current.

Specific requirements are shown below:

Requirements:

  • Dual Independent Voltage Inputs
    • 110VDC nominal
    • 150VDC maximum
    • 90V minimum (limited by internal +12VDC power supply)
  • Current available
    • 10A maximum (fused)
  • Voltage Output
    • 110VDC nominal
    • 150VDC maximum
    • 90V minimum (limited by internal +12VDC power supply)
  • Environment
    • Interfaces to household wiring
    • Will see outdoor use
  • The following not implemented in prototype:
    • Exposed to lightning
    • Must survive reversed input voltage
    • Must survive overvoltage and undervoltage transients
    • Must provide 20ms output holdup at maximum load

Circuit Schematic

Discussion:

A differential amplifier stage was used to amplify the voltage developed across a current sense resistor. The differential amplifiers output a zero to 10V signal, corresponding to 0A to 10A of load current. This signal is then fed into an LED bar graph driver IC, which activates the appropriate number of bars on the bar graph. The presense of power LED's are controlled by an NPN BJT's. Part numbers are for simulation purposes only. For example, unless a 15mA LED is choses, anomolous simulation results are produced.

Simulation Output

Application of 110VDC and then 120VDC, and the resulting load current. Also shown is the output of the differential amplifiers. As shown in the simulation output, the load current rises to 11A, which in the real system will blow the fuse. The simulation is run like this to show a definite transition between power sources.

Test results videos

Testing the dual-diode box one side at a time.

Test results videos

Test of internal +12V power supply.

Test results videos

Observations upon examining the internal boards.

Test results videos

Testing of the signal processing board.

Test results videos

Testing of the display board.

Test results videos

Repair and retest of the signal processing board.

Test results videos

Discussion of the test setup schematic and simulation.

Test results videos

Successful two-sided test of the Dual Diode Boxn.