Usually this DC coupler is working with an AC power adapter that with DC 8.4-8.7V output. When you want to long time shooting outside without AC outlet, then you'll feel it's not convenient. Also you can use with a DC 8.4V power bank, but it's not easy to find a DC 8.4V power bank, and it's expensiver.
So we provide this solution, with our coupler and customized USB cable built-in intellgent circuit board(improve DC output from 5V to approx 8.7V), you can connect this USB with DC 5V 2A power source. It's easy to find a DC 5V 2A power source, and DC 5V 2A power source is much cheaper than a DC 8.4V power source.
By the way, we notice a buyer feedback that, use our prodcuts can start his camera, but when shooting, the camera shut down. we'd like to explain here, we provide the the DC coupler and the USB cable adpater only. For this customer's case, proves our products can successfully connect the power, and the cable adapter successfully improves the voltage. But when shooting, the camera shut down, this the power source's problem. Please use a power source at least DC 5V 2A, DC 3A is better. To solve this problem, you just need to change a power source.
And If you use a power bank, please choose a high quality power bank, there are too many power bank in the market. A lots of power bank mark the fake output, they do not allow to draw higher current, when you shoot, it's bond to draws higher power than you start the camera, then the power bank stop supplying the power, then the camera shut down.