±15V Fixed Power Supply
For the Extron RGBHV Video 8x8 Matrix Switcher in my Home A/V System

Devin R. Ott
Designed & Constructed – August 2013

Description:

Utilizes two ungrounded +18V @ 2.75A switching power supplies (salvaged from my company’s warehouse) as input voltage sources, referenced above and below earth ground to feed the positive and negative linear regulators in this circuit.

Like the power supply for my Extron Composite Video Matrix Switcher, this is a very standard circuit I setup, tested, laid out & assembled on PCB, and installed in the same weekend.

This power supply restored operation to my main RGBHV matrix switcher, which handles all HD Video switching to the (4) LCD/LED flat panel displays around my apartment.

I was going to use the exact same circuit I employed for my Composite Video Switcher, but the inrush current on the positive supply was too high, forcing the ‘7815 regulator into overload protection from which it could not recover by itself (even though it could handle its steady-state current draw). For this reason, I used an adjustable regulator in a TO-3 package which could handle the inrush current.

Schematic:

Same negative power supply circuit as my Composite Video Switcher, but the positive regulator circuit is equipped to handle the higher 1.3A inrush current for when the RGBHV switcher powers up.

Click HERE for complete design notes [PDF]

PowerSupply_8x8_RGBHV_Matrix_Schematic

Final Assembly:

Dual +18V, 2.75A ungrounded switching DC power supplies provide the 18V input (referenced above & below chassis ground) to the linear IC voltage regulators. Also provide non-conducting mounting surface for the ±15V power supply assembly.

Final Installation:

Red LEDs provide convenient at-a-glance verification of the output voltage from linear regulators.

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