When it comes to supplying power from a monitor and PC, you may already know that a DisplayPort has a unique ability to support and supply power to an external display adapter. With that said, could VGA cables supply power in any sense?
VGA ports are signaling specifications and are not designed to carry power to and from any source. As most display sources transmit a digital signal, VGA is designed only to transmit an analog signal to translate into a visual image supplied from either the video card or motherboard.
Does VGA Supply Power?
To understand how the VGA connector works, let’s look at the above picture (the VGA connector found on your PC) and see what each of the 15 pins does when plugged into your monitor from your monitor (the male connector).
- Red Video (To monitor from video card)
- Green Video (To monitor from video card)
- Blue Video (To monitor from video card)
- Monitor ID 2 (To video card from the monitor)
- TTL Ground (Monitor self-test, used for testing purposes only)
- Red Analog Ground
- Green Analog Ground
- Blue Analog Ground
- Key (A plugged hole, not used for electronic signals)
- Sync Ground (For both sync pins)
- Monitor ID 0 (To video card from the monitor)
- Monitor ID 1 (To video card from the monitor)
- Horizontal Sync (To monitor from video card)
- Vertical Sync (To monitor from video card)
- Monitor ID 3 (To video card from the monitor), or DDC (Display Data Channel)
The synchronization or sync pins on a monitor’s connection are the most critical. Horizontal, vertical, and ground are the three options. A horizontal sync pulse signals the end of a horizontal line, while a vertical sync pulse indicates the end of a vertical screen frame.
Each horizontal pin pulse generates one scanline across the screen. The vertical pin only pulses after the entire screenful has been drawn; a vertical pin pulse causes the monitor to return to the upper-left corner of the screen and begin displaying the next frame.
The horizontal sync pin often pulses several thousand times per second. Still, the vertical sync pin typically pulses fewer than 100 times per second (depending on the display’s vertical refresh rate).
VGA cables are classified into two types: 14-pin and 15-pin. 14-pin cables will suffice; however, 15-pin cables may be necessary for greater display compatibility. It is a VGA cable with 15 pins.
Manufacturers deleted pin “9” from 15-pin cables, turning them into 14-pin cables because the key signal had become outdated with current computer displays and was no longer used in the VGA standard’s default applications.
However, Pin 9 has lately been resurrected as a power supply pin in certain screens to power circuitry. Although this pin does not power the entire display, it is essential for data exchange between the display and the computer.
Display data communication (Display Data Channel or DDC) sends display information such as maximum resolution and display name or type to identify screen resolution.
Does VGA Have 5V?
Modern VGA implementations employ all 15 pins to enable a broader range of applications, notably in the expanding home theater sector. Because digital material may now be sent to a TV rather than a computer monitor, it is critical that displays are accurately recognized and identified by source hardware.
Pin 9 now serves as a 5v DC power rail, while Pin 15 serves as the VESA DDC (Display Data Channel). The power line is intended to power the EDID or DDC chip within a display to be identified when not powered externally. In contrast, the DDC line is intended to carry that information back to the source device.
Whether or not your TV needs this power for the DDC handshake depends on the manufacturer and the implementations selected for each display brand. Some screens can happily operate without pin “9” as long as they receive electricity from the wall, while others will refuse to ‘handshake’ until it is there.
Additionally, another way of seeing it is taking visual signal transmitting into consideration; pins 1, 2, and 3 on a VGA connection have a maximum voltage of 0.7 volts. In particular, they are analog 0.7-volt positive signals with a 75-ohm load at either end of the circuit in the video card and display.
In other words, if all three of these pins are at 0.7 volts, the monitor will show the brightest white possible. All of the remaining pins on a VGA connection are TTL-level signals, which means they are 5 volts.
There is a lot of uncertainty and a lot of missing information about what format VGA color signals truly have. Although many individuals realize that these signals are 0.7 volts, some appear to believe that the video signals are waves (that is, that the signals must be continually changing and cannot simply be a constant voltage).
It is just not true; it is feasible to provide 0.7 volts DC (direct current, which is a steady, unchanging 0.7 volts rather than a wave) to a color wire to achieve the maximum brightness for that wire’s color.
While this is completely worthless for drawing a real picture (unless the picture is all one color), it does make it simple to design a test circuit that makes a monitor’s screen all one color to test whether or not it works.
However, some monitors will not function properly until all three color wires are brought to zero volts outside of the viewable video region. Some displays demand the color signals to be at zero while either of the sync signals is active.
Other monitors don’t mind and will continue to function normally even if the three-color pins are not at zero volts.
If you’re planning to build a basic test circuit in which one color is always “on,” keep this in mind; your display may need you to mute the color signal when sync pulses are active. In fact, most modern displays demand this. Leaving the color signals turned on during sync pulses may result in a blank screen.
1/ How Much Power Does A VGA Cable Use?
Now that you have a better understanding of the VGA connecter, what about the connector? Is great to know that power is transmitted through the cable to communicate between PC hardware and monitor; however, how much power does the cable hold?
Devices that adhere to the DDC host system standard supplies power on pin “9” of the conventional 15-pin VGA connection. The voltage is 5V +-5% and provides a minimum of 300mA to a maximum of 1A throughout the cable.
2/ What Does VGA Mean On A Power Supply?
It may be confusing when you look at a power supply unit (PSU), and it would stipulate on some ports “VGA1, VGA2, VGA3,” and so forth.
In this instance, the “VGA” labeling you may find on some of your power supplies ports is for “Video Card Power.” Very much so as the “SATA” on the power supply is for “Drive Power,” both are entirely different things compared to their most common uses and meaning.
VGA cables have tons of interesting aspects to them. Understanding how they work and what feeds power is always a great start to understanding how your computer displays information, what instruments make it happen, and how they work.
Try not to be confused when you build or set up your computer tower and find VGA on your PSU (power supply). That information is understood differently in terms of power. At the same time, Virtual Graphics Array (VGA) is also understood in terms of display sources and identified as a specific display cable.
Vance is a dad, former software engineer, and tech lover. Knowing how a computer works becomes handy when he builds Pointer Clicker. His quest is to make tech more accessible for non-techie users. When not working with his team, you can find him caring for his son and gaming.