[First Release on the Entire Webpage] Thunderbolt 4 Laptop Graphics Card Dock

Project Introduction:
       This project aims to open-source a Thunderbolt 4 graphics card enclosure based on the JHL7440 controller. Users can connect high-performance desktop graphics cards to laptops via Thunderbolt interfaces to improve laptop graphics processing performance. The enclosure features a PD3.1 charging circuit, allowing simultaneous charging of the laptop and graphics card. It also includes a battery pack and battery management system; when the power supply to the enclosure is interrupted, the battery pack continues to power both the enclosure and the user's laptop, preventing game crashes and data loss due to sudden power outages. The finished product image and rendering of the graphics card enclosure are shown in the figures.
 
Open Source License :
This project is licensed under the Creative Commons Attribution-ShareAlike 4.0 license. Commercial use is prohibited. Please indicate the source when reprinting.
 
Project Attributes
: This is the first public release of this project, and it is the author's original work. This project has not won any awards in other competitions.
 
Project Update:

April 4, 2024: Released the open-source project Thunderbolt Laptop Graphics Card Dock. The main circuit version is: NoteBook eGPU Dock-B v0.2.

 
Project Progress:
This project is part of the Spark Program's bounty track. As of March 25, 2024, all project indicators have been completed and verified.
Additional components were added to the project requirements, including a UPS circuit, PD3.1 charging circuit, USB 10Gbps interface, and buck-boost power supply, enabling the graphics card enclosure to support

UPS functionality
and PD3.1 reverse charging.
Wide voltage power supply was also

implemented. As of April 2, 2024, all of the above functions have been verified.
 
Project Parameters
: Maximum Supported Graphics Card Power: 240W;
Thunderbolt Data Bandwidth: 32Gbps;
Maximum Reverse Power Supply Power of PD Port: PD3.1@140W;
Maximum Reverse Power Supply Power of Thunderbolt Port: PD3.0@60W;
Dimensions: 190x148x68mm (LxWxH).
 
Project Introduction
  : 1. Hardware Introduction
      : 1.1 Overall Introduction:
The hardware circuit consists of two PCBs. One is the graphics card enclosure motherboard, responsible for power supply, PCI-E high-speed lines, and battery management. The other PCB displays negative battery parameters and provides a power failure alarm.
The motherboard power tree is shown in the diagram.
        The system power supply can operate in two states. In the first state, when powered by an external power adapter, the input from the top left (12-24Vin) is the external power adapter input. After entering the system, it splits into two paths: one goes to the Charger, which charges the battery via the BQ40z50 fuel gauge; the other goes to the PowerPath circuit. The PowerPath circuit checks if the main power supply is functioning correctly. If so, it turns on the main power discharge MOSFET and turns off the backup power discharge MOSFET. The main power supply then powers the subsequent circuits. The subsequent PowerSwitch is a power switching circuit that uses a PMOSFET as the high-side switch. When the user closes the mechanical switch, the PMOSFET conducts, powering on all subsequent power supplies.
       In the second state, when the system is powered by the battery, the 4S Li-ion battery enters the PowerPath circuit via the BQ40z50 fuel gauge. Since the external power supply is disconnected, the PowerPath turns on the battery discharge MOSFET, selecting the battery to power the subsequent system.
When the adapter voltage is below 10.8V, PowerPath will choose to use battery power; when the adapter voltage rises back to 11.8V, it will switch to adapter power.
      ThunderBolt Module2 high-speed wiring diagram:
Motherboard PCB 3D diagram is shown in the figure:
MCU board hardware block diagram is shown in the figure:
The MCU board is responsible for accessing battery parameter data from the BQ40z50 fuel gauge, power failure alarm, and temperature detection. The MCU selected is STM32F103C8T6.
MCU board circuit 3D diagram is shown in the figure:
     1.2 Introduction to the graphics card power supply (LM34936):
       Since the project needs to support a wide voltage (11-24V) power supply, and the graphics card's operating voltage is 12V, the input must pass through a DC-DC power converter before powering the graphics card. Furthermore, because the RTX3060TI graphics card's full-load power consumption can reach 240W with a large dynamic range, a high-efficiency DC-DC power supply with good dynamic response is required.
      This project uses TI's LM34936 solution. The LM34936 is a buck-boost topology DC-DC power controller that supports a wide input voltage range of 4.2-30V. It uses current-mode control in both buck and boost modes, providing excellent dynamic response performance. After generating the circuit diagram using Texas Instruments' WEBENCH power design software and performing simulations, the power efficiency reached 97.2%. The dynamic response simulation is shown in Figure
    1.3. PowerPath Module Introduction :
        Since both power supplies can power the graphics card enclosure, and the secondary power supply needs to immediately replace the main power supply to power the device when the main power supply is disconnected, there can be no switching delay. Therefore, the LTC4416 chip was chosen. The LTC4416 is a dual-channel power path management chip that uses a hardware comparator to control the power switching circuit, achieving the fastest power switching speed. Actual testing showed that a 0-second switching time was achieved under a 20V 20A load, as shown in the figure.
        Channel 1 in the figure represents the power adapter output voltage, and channel 2 represents the voltage output by the PowerPath circuit. At approximately 240ms, when the external adapter is powered off (channel 1), the PowerPath circuit switches to the auxiliary power supply, and the voltage drops to the auxiliary power supply voltage (channel 2).
       Before use, resistors for three hysteresis comparators need to be configured; the formulas are available in the datasheet and the engineering circuit diagram.
 
    1.5 The BQ40z50 fuel gauge
      requires 400W of power when running at full load, and the load is quite dynamic, putting significant stress on the battery. Due to the battery's internal impedance and the dynamic load, battery power measurement faces considerable challenges. This project uses the BQ40z50 fuel gauge with an impedance tracking algorithm. This fuel gauge can measure the battery pack's impedance, and regardless of load changes, the fuel gauge can find the battery pack's open-circuit voltage. Through prior chemical parameter matching, the corresponding power level at the current open-circuit voltage can be obtained.
2. Hardware Performance Testing
   2.1 Graphics Card Power Supply Ripple and Dynamic Response
    The oscilloscope was set to AC coupling, bandwidth limited to 20MHz, probe at x1 setting, and grounded using a grounding spring. The measured ripple of the graphics card power supply under no-load conditions is shown in the figure:
     Ripple magnitude is 24mV.
     The measured ripple under full load conditions is shown in the figure:
      Full-load ripple magnitude is 35mV.
      Test Scenario:
     A dynamic electronic load was connected to the power supply. A 100Hz 1100mV square wave signal was generated using a signal generator to control the electronic load to produce a step current signal. The resulting dynamic response of the power supply is shown in the figure:
       In the diagram, channel C2 represents the power supply's output current, and channel C1 represents the power supply's voltage. Channel C1 enables AC coupling, with a bandwidth limit of 20MHz. As the current increases from 0A to 11A, the system overshoot is approximately 72mV; as it decreases from 11A to 0A, the overshoot is 61mV, indicating good dynamic response.
      Dynamic Response Test Scenario:
    2.2 Thunderbolt 4 Bandwidth Test:
                  Graphics Card: MSI AERO RTX3060TI LHR
                  Cable: JEYI Passive Thunderbolt 4 Data Cable 25cm
                  Test Software: AIDA64 Extrame
 
    2.3 System Heat Test:
       PCB temperature was detected using a thermal imager when the battery was not fully charged, the system was not connected to any devices, and no heatsink was installed: PCB temperature was detected
       when the adapter was used for power supply, the battery was not fully charged, the system was under full load, and no heatsink was installed:
Test Equipment: Hikvision K20
 
Replica Notes:
   1. Required Components:

 THUNDERBOLT MODULE2 module, as shown in the picture;


  High-voltage lithium battery, model: 1102760, capacity 1.95AH, as shown in the picture;

 
 

  14AWG silicone wires, used for powering the graphics card and connecting the graphics card and the graphics card box.
   SMD soldered copper block, 6*2*2mm, used to assist in heat dissipation and increase the current carrying capacity of PCB wires;
   5557 clamp-type 8-pin graphics card soldering connector, used for graphics card power supply, as shown in the picture;


     6.5mm banana head connector, used to connect the graphics card and the motherboard of the graphics card enclosure, 2 male and 2 female connectors are needed,        as shown in the picture; 7*5*0.3mm cold solder pads, used to connect the battery to the motherboard of the graphics card enclosure, 8 are needed, as shown in the picture; 0.96-inch LCD screen, ST7735S main controller, used for the MCU board to display system parameter information, as shown in the picture; screws: M2*4, M2*16, M3*8 ; studs: 4; M3*45+10; power adapter: 12~24V is acceptable, depending on the graphics card used. I used an RTX3060Ti graphics card. The graphics card enclosure also charges the laptop while working, using a HOTA 245W*2 GaN power supply, which works stably in actual testing. If using a 12V power supply, the full-load voltage drop should not be too large. If the input voltage is less than 10.8V, the system will consider the external power supply abnormal and switch to battery power. 8mm heat shrink tubing is used for capacitor aluminum shell insulation.    2. PCB Fabrication        2.1 Prototyping            This project requires prototyping three PCBs: GPU_Dock_MotherBoard, MCU_Board, and an 8-pin connector.            When ordering the GPU_Dock_MotherBoard PCB, select the JLC04161H-3313 laminated structure. Impedance control is required, ±20%, and the board thickness is 1.6mm. The other PCBs are also 1.6mm thick and do not require impedance control.        2.2 Soldering              2.2.1 Some Precautions         Solder the battery last! Solder the battery last! Solder the battery last!            The PCB component layout is relatively dense. If SMT is not selected, it is recommended to solder the chips first, then solder the resistors and capacitors; otherwise, if the chips have solder joints, the soldering iron will not be able to remove them.            After all components are soldered, do not insert the Thunderbolt Module 2 module. Power on and test first. Once the power supply is normal, insert the module and test again.            If the computer recognizes the graphics card, perform a stress test. If no problems occur, then solder the battery, being careful not to short-circuit. 2.2.2               PCB after soldering.               2.2.3 Soldering           Precautions: Ensure insulation on the front of the PCB: The NTC resistors with reference numbers BAT1~BAT4 are MF52B103F3450, or you can use B3450 10K resistors instead. Since these NTC resistors use through-hole pads, the graphics card backplate directly contacts the front of the PCB. You need to grind the leads flat on the front of the PCB and then apply insulating paper to prevent the graphics card backplate from short-circuiting the resistor. The same applies to reference numbers C217 and U22.           Ensure capacitor insulation: Capacitors with reference numbers C113, C114, C217, and C221 need to be covered with heat shrink tubing before soldering to prevent short circuits in the aluminum casing.           Note the battery soldering order: Solder the battery with reference number B4 first, then B3, and so on.           NTC Resistor Locations: This project uses a total of 6 NTC resistors. Four NTC resistors detect battery temperature, and two NTC resistors detect the temperature of the graphics card power supply and power path management. The four NTC resistors for detecting battery temperature need to be glued to the battery; 704 silicone rubber can be used. The NTC resistor for the graphics card power supply needs to be glued to the inductor with the L6 bit number, and the NTC resistor for power path management needs to be glued near Q14 and Q13.       2.3 After programming and          PCB soldering, power on the device and check if each power supply is working properly. If all power supply voltages are normal, the module and graphics card can be inserted. After insertion, use Thunderbolt 4 to connect the graphics card enclosure to the computer. The computer should be able to recognize the new GPU. If it is recognized, it means that the soldering of the main components is correct.              2.3.1 Fuel Meter Configuration:          Configuring the fuel meter requires an EV2400, which can be purchased from Taobao for around 120 RMB. The EV2400 is shown in the image.            You also need to download Battery Management Studio from the Texas Instruments website, or use the one uploaded to your cloud drive. Connect the debugger's SMBD and SMBC interfaces to the SDA_BQ and SCL_BQ pins of the graphics card enclosure's motherboard, respectively. Since the PCB does not have a pre-installed GND interface, you can use a Thunderbolt cable to connect the computer and the graphics card enclosure's motherboard, ensuring they share a common ground. After connecting, open Battery Management Studio. Normally, this interface should pop up: If this interface appears, "Auto Detected Device: None," it indicates that the fuel gauge and computer have not communicated successfully, as shown in the image.         At this point, you can select any device to enter the configuration interface and check if the EV2400 is successfully connected to the computer. If the software can read the EV2400 version, the EV2400 connection is fine. You need to check for any issues with the circuit soldering.







 











           











          If the EV2400 version number cannot be detected, check if the EV2400 is properly connected to the system and whether Windows provides a prompt after plugging in the EV2400. If the system provides a prompt but the host computer software still cannot detect the version, it may be a system environment issue. You can try running Battery Management Studio on another computer or in a virtual machine.
            The fuel gauge on the PCB is BQ40Z50-R1, which is flashed with R1 firmware by default. The configuration in the cloud drive link is based on R2 firmware and needs to be upgraded. Refer to the fuel gauge configuration video for details.
Other
      tests have shown that this project can run stably on Redmebook 14, Thinkbook 14+, and Legion Y9000x. Some Lenovo ultrabooks may experience Thunderbolt 4 incompatibility, mainly manifested as Thunderbolt 4 disconnection within a few seconds after connecting the graphics card enclosure.
Attachment
link: https://pan.baidu.com/s/1yPTTYX021ZoxA8l5VQojqw?pwd=0udn Extraction code: 0udn