Energy saving solutions through driver IC and input detection mechanism

Space and cost constraints have always been important factors in the design of consumer electronics, so that the products that enter the market are beautiful and attractive, and offer competitive prices that are attractive to the public. In addition to meeting these two requirements, the impact on the environment has also become a growing concern, which means that energy consumption has become an important consideration for design engineers. The latest changes that have been made to the US Energy Star (Energy Start) directive highlight this fact.

Today, most video entertainment systems still require analog video signals. The most commonly used is a single-channel composite video blanking sync (CVBS) signal, which is often seen on video output interfaces to maintain standard resolution functions as a backup output. Typically, 1080i high-definition (HD) analog video content requires a 3-channel YPbPr signal. In order to comply with the Energy Star directive, any DVD/Blu-ray player or set-top box (STB) must consume less than 1 W in sleep mode, as shown in Figure 1.

Video signal detection

Semiconductor suppliers serving the set-top box and DVD/Blu-ray player markets face an important energy-saving challenge to help systems reduce power consumption when entering sleep mode. In this mode, a certain percentage of the chipset's functional blocks are turned off, including the integrated video digital-to-analog converter (DAC). As a result, no signal passes through the video driver. At the same time, other functional blocks of the chipset are still working at full capacity and consuming power. Since these functional blocks are powered by the same power supply line as the video driver, additional control is actually required to activate/deactivate these drivers. Therefore, if there is no "enable" logic in the design, the power consumption will still be unacceptably high.

Therefore, there is a clear need for video drivers that can automatically detect the presence of a video signal at the input, eliminating the need for external control to turn the driver on or off. However, the key question that needs to be answered here is: how long does it take for the video driver to resume operation from sleep mode - can the video driver start up quickly enough to ensure that image integrity is maintained? If this is not possible, the viewer experience will be impaired.

Load detection

In addition to the energy savings from automatic video signal detection by the video driver, there are other areas where significant energy savings can be achieved. It has proven costly and difficult to have the chipset detect the presence of a TV connected to the RCA connectors dedicated to analog video channels, especially if the output of the video driver needs to be AC ​​coupled. Some original equipment manufacturers (OEMs) have investigated using mechanical solutions to solve this problem - triggering a switch when the cable is inserted, but this has also proven to be cost-prohibitive. The possibility of integrating load detection functionality into the video driver will also have obvious advantages in the design process.

The NCS2584 4-channel video driver IC (as shown in Figure 2) introduced by ON Semiconductor can automatically detect whether there is a video signal at its input, and can turn on or off each driver channel separately when there is or is not an input signal. This driver has applied the signal detection block intellectual property (IP) (patent pending), which manages the timing and enables the chipset to resume work quickly enough when it leaves sleep mode to avoid any synchronization loss.

When a TV is not plugged into the CVBS and/or YPbPr channels, the driver component enters a low-current shutdown mode, consuming less than 10 μA. On the other hand, when a TV is plugged into the analog channel, the driver recognizes that the TV is present. It then verifies if the input signal is working. If no signal is working, the component waits for the input video signal to wake up the system. This is described in detail in Table 1.

In periods longer than the standard resolution line duration (i.e. 63.556 μs), the driver detects the input signal in less than 2 μs and automatically restarts, resulting in no image loss. In addition, its integrated load detection circuit menu shows that the driver can manage its own power consumption and minimize energy loss even during normal operation of the video entertainment system. As a result, the chipset does not have to manage the detection of the presence of a TV connection, thus simplifying the chipset code and reducing power dissipation. In addition, because the driver is not limited to any specific chipset, specifying this driver provides engineers with greater design flexibility by being able to fully manage output load detection autonomously.

in conclusion

The latest generation of analog video driver components is now emerging and needs to meet the energy-saving requirements stipulated by the Energy Star program. By using the embedded detection functions provided by some driver ICs, engineers do not need to worry about how to improve the energy efficiency of their designs in analog video output. By integrating more functions such as video signal detection and load status monitoring in the driver itself, the control of the drive mechanism can be simplified and the overall energy consumption of the system can be limited.