High-power expansion dock integrating fast charging protocols

1. Project Overview
Traditional docking stations only support 5V, 500mA output, which can easily lead to insufficient power supply when driving devices exceeding 2.5W. Therefore, this project integrates fast charging technology on the basis of a regular docking station to improve the power supply problem. Specifically, the power supply section of this device adopts a CH224 (fast charging decoy) and two TPS54202 (DC-CDC 5V step-down) architecture. Meanwhile, the data section uses the SL2.1A chip, which also functions as a docking station, meeting the needs of high power and data transmission. After testing, the total output power of the power supply expansion interfaces reached 20W, and the maximum data transmission rate reached 34.9Mb/s.
2. Block Diagram
2.1 Power Supply Section


Figure 1 shows a schematic diagram of the power supply section. The `CH224K` is connected to the charger via the `CC` cable, and the charger's output voltage is stepped down to `5V` by the `TPS54202`.
2.2 Data Section


The data section expands to 4 channels via USB D+ and D-.
3. Principle Analysis
3.1 Power Supply Principle Analysis
3.1.1 Fast Charging Protocol
The mainstream fast charging protocols include QC and PD. The QC protocol uses the USB D+ and D- lines, while the PD protocol uses the CC line. The CH224 supports both protocols. Since the D+ and D- lines are used for data expansion, this paper uses the QC protocol for spoofing in the power supply section. This is achieved by connecting the CC1 and CC2 of the Type-C male connector to the CC line of the CH224 chip. The CH224's CFG1 is connected to GND with resistor R11, and different resistance values ​​correspond to different voltage request levels. The specific table is as follows:




Resistor
Request Voltage




6.8KΩ
9V


24KΩ
12V


56KΩ
15V


NC
20V




The specific voltage that can be spoofed depends on the capability of the fast charging device itself. If the device's maximum voltage is only 12V, then even if configured for 20V, only the highest 12V output can be requested.
3.1.2 TPS54202 Step-Down Chip
The TPS54202 step-down chip supports 4.5V-28V input. R11 is set to 24K, induced at 12V.
The maximum voltage of the PD3.0 protocol is 20V, so R11 can be omitted (but note that the withstand voltage of C2 and C8 should be above 20V). The voltage is directly induced based on the maximum output voltage of the charging head. The design of the step-down circuit and PCB layout both refer to the datasheet.
4. Usage Method
4.1 High-Power Expansion
After plugging the device into the charging head, this device can expand the charging head to 4 outputs. Without fast charging protocol support, each output supports 5V/0.5A; when fast charging protocol is activated, it provides the corresponding output power according to the load demand to meet the needs of high-power devices.


4.2 Ordinary Expansion Dock
After plugging the device into the computer, the device can be used as an ordinary expansion dock, conveniently connecting peripherals such as mice, keyboards, and USB flash drives. The data transfer rate can reach 34.9Mb/s, meeting daily usage needs.


5. Precautions:

Capacitors C14 and C15 must be soldered; otherwise, the expansion dock function in the data section will not work properly.
Pin 11 of the CH224 chip (similar to a heatsink pad) must be connected; otherwise, fast charging cannot be triggered.
It is recommended to choose a PCB thickness of 1.0mm when fabricating the board; otherwise, the Type-C interface may not be able to be inserted.

6. Attached Files:

High-Power Expansion Dock BOM - LCSC_20240904.xls
Datasheet,
High-Power Expansion Dock Gerber File (for direct board fabrication),
High-Power Expansion Dock PCB