With the popularity of the USB type-C interface, more and more mobile phones and laptops support outputting videos through the C interface. This small and precise interface has the potential to replace traditional HDMI and DisplayPort interfaces. Especially with the launch of USB 4, it laid the foundation for the unified wired interface form of USB type-C interface.

In this context, it has become inevitable for monitors and televisions to use USB type-C interfaces. So how can we design monitors and televisions based on the USB C interface to have better compatibility and pass certification? Let's elaborate on the design process of transitioning from a display to a USB type-C interface in detail.

The first form is a portable display with a single USB C interface.

After the USB-IF Association released the USB type-c standard, the first manufacturer to introduce this interface display was Asus.

Figure 1: The world's first USB type-c portable monitor released on CES 2016

Asus did not choose to launch its first USB type-C monitor on its existing desktop monitor, but instead launched a portable monitor to complement the state-of-the-art C interface. This seems to be a product designed to fully highlight the characteristics of the USB type-C interface that can transmit both power and video, perfectly interpreting the design intention of a USB type-C cable to handle all transmission. The functional structure diagram of this product is as follows:

Figure 2 Structural Block Diagram of a Single USB Type-C Interface Display

This portable display only requires a USB PD control chip, similar to LDR6023M or LDR6282, to achieve synchronous transmission of power and power. For lightweight portable displays, this technology architecture is the most suitable.

The second form is a desktop display with a single USB C interface and both HDMI/USB expansion and DC/AC power supply.

This is a typical form of desktop display, where the entire display receives 24V/3A high-power input through a DC circular port or AC input, with a built-in high-power AC/DC conversion circuit. The power supply of this type of monitor not only provides power for the monitor itself, but also provides a power output of around 30W to 40W for connecting to the monitor phone or laptop through the USB C interface, similar to Apple's display with MAGSAFE power output.

Figure 3 Dell Launches Single USB Type-C Interface Display with a Maximum Output of 90W Power

The Dell U2720QM is quite aggressive. In addition to transmitting 4k high-definition videos, the USB type-c interface can also provide up to 90W of output power to external USB C devices. The technical architecture of this type of display is shown in the following figure:

Figure 4 Interface Control Chip LDR6282/LDR6290/LDR6023D for Single USB C Interface Desktop Display

From the figure, it can be seen that the USB PD main control chip, such as LDR6282, LDR6023D, LDR6290, etc., can simultaneously control the USB C interface and power module. Make the power module and USB-C control module perfectly cooperate to solve various complex functions required by the USB-C interface display.

The third form is a display with independent dual USB C interfaces and an HDMI interface.

This type of monitor has dual USB C interfaces, but the functions of the two ports are different. One port is a fully functional port that can be used to transmit video signals and power. The other port can only be used to transmit power signals and cannot be used to transmit video signals. In fact, it is equivalent to changing the circular DC power supply port commonly used in monitors to a USB C power supply port. The circuit structure of this type of display is simple, making it particularly suitable for low-cost portable displays.

Figure 5 Circuit structure diagram of a non fully functional dual USB C interface display

The fourth form is a display with dual full function USB C interface and HDMI interface (commonly known as dual blind plug USB C display).

This type of display has more advanced technology. Both USB C interfaces are fully functional, capable of transmitting both power and video signals. It can also achieve power transfer between two USB C interfaces. The power input from any USB C interface, after retaining sufficient power as the display's own power supply, can be transmitted to the intelligent device through another USB C interface. Since there is no longer a need to remember the difference between the two USB C interfaces, it can be inserted arbitrarily. This type of USB C display, also known as a dual blind USB C interface display.

This display design architecture can be used for both portable and desktop displays. For the portable display market, the dual functional USB C interface is undoubtedly the best choice for consumers. Because the operation of plugging and unplugging interfaces for portable displays is relatively frequent, consumers will be annoyed if they need to distinguish the functions of two interfaces with identical appearances. Even for desktop displays, considering that all power adapters will be unified to the USB C interface in the future, pre layout for power supply through the USB C interface is a very forward-looking strategy in product planning.

Figure 6CF011XPRO Dual Functional USB C Interface+HDMI Interface Display

Obviously, to achieve such a complex dual function USB C interface display, the internal circuit is also relatively complex. By disassembling mainstream displays with such functions, we have discovered that the core to achieving this function is a chip called LDR6282. This chip can manage the power supply and Datapath of two usb c interfaces. Perfect solution to various complex compatibility issues when implementing dual USB C full functionality. The following is the application circuit diagram of LDR6282.

Figure 7 Reference Circuit Block Diagram of Dual Full Function USB C Interface (Double Blind Insertion) Display

The fifth form includes three USB C interfaces for picture in picture functionality and USB C video daisy chain functionality.

Three USB C interface display configurations are currently relatively rare. However, considering the future applications of multi-screen interaction and display expansion, this technology is still worth researching and developing. We have indeed found an implementation solution for three USB C interface displays for those who need it to refer to.

From the structural diagram of the display design of the three USB C interfaces in Figure 8, we can see that in fact, two of the three USB C interfaces have the same function as the fourth form. The third additional USB C interface is very valuable. It can serve as a high-power power input, allowing the other two USB C interfaces to be connected to smart devices and achieve a picture in the picture function. It can also serve as a one-stop video daisy chain output for multi-screen expansion. This application scenario has a very rich imagination space.

Source: Charging head network