EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: eas on August 15, 2016, 07:27:38 am
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I am hoping to use use a USB power bank that supports Qualcomm Quick Charge 2 as a 12V power supply for an otherwise "dumb" device.
Can anyone point me to a simple implementation of the circuitry needed to negotiate the 12v output?
I think I have enough information to figure out a solution myself, but I'd rather start with a known-good design.
If I understand things correctly, the QC2 charger (ie my the USB power bank) starts by signaling support for USB Charging-1.2. The device is then supposed to drive the USB D+ and D- lines high ( >0.325v, <2v) for at least 1.25s. This should put the charger in QC2 mode. The charger will then connect a pull-down to D-, and once D- goes low for more than 1ms, it will look for the device to signal the requested output voltage. For 12v, it is supposed to hold D+ and D- at 0.6v.
So, if I've got that right, I think I could manage it with a small MCU, a voltage regulator, a few passives and some simple code, but, again, I'd rather start with something that is know to work.
Thanks for any suggestions on where I can find something to get me started!
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take a look of the NCP4371 State Diagram on page 10
NCP4371 - Qualcomm Quick Charge 3.0 HVDCP Controller
http://www.onsemi.com/pub_link/Collateral/NCP4371-D.PDF (http://www.onsemi.com/pub_link/Collateral/NCP4371-D.PDF)
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Thanks! I actually found that diagram shortly after I made my post, which helped clarify the handshaking.
I'm still hoping to find an existing device-side implementation of QC2/HVDCP handshaking I can leverage. There are some ICs, but they including a 1S charger, which I really don't need.