USB has been the de facto standard for charging phones and tablets, and for both powering and charging many other consumer electronics devices. Legacy USB specifications using the Standard-A port have allowed for up to 7.5W (5v 1.5A) for USB BC 1.2 devices. This is enough for small devices, however in order to power larger devices like Laptop computers, modern tablets, and external displays, a new charging standard is required that supports higher voltages and higher wattage.USB Power Delivery, along with the USB-C port, allows for providing up to 240W (48V 5A) with the latest USB PD 3.1 EPR (Extended Power Range) specification. This is enough to power most notebook computers, external displays, and many external devices. Most current USB-C power supplies output between 60-100W, we expect EPR's adoption over time.USB Power Delivery (USB PD for short) also allows for chaining devices together using USB PD Pass-Through, for example a power supply can power a docking station which in turn can power a computer, reducing the need for keeping track of multiple power supplies. Each device along the way has a power budget and may reserve some portion of the available power for powering built-in or connected components.For example our USBC-6950PDZ USB-C Dual HDMI Mini Docking Station sits between the host computer's original USB-C power supply and the computer, it requires about 18W to power the docking station's internal components and external USB devices reducing the available power to the computer. In most cases the computer will operate fine with the reduced power budget, but may charge a bit slower when using the docking station. However, if there is not enough power in the budget to charge or power the computer, a higher rated power supply may be connected to the docking station. For example replacing a laptop's original 45W USB-C power supply with a Plugable 60W USB-C power supply. This docking station supports up to 100W power supplies and can provide up-to 82W to the connected computer.PD Pass-Through is an important step to bringing one connector to support all devices, providing a method of powering multiple devices from a single power source. If you have any questions about our devices with USB Type-C PD Pass-Through, or questions regarding compatibility with your computer, please feel free to contact our support team via email at  'support@plugable.com' and we will be happy to help!