Managing power consumption of video entertainment equipment

Managing power consumption of video entertainment equipment

Placing video signal detection and load status monitoring in the driver will simplify control of the driving mechanism and curb overall power consumption

BY XAVIER BIGNALET
Application Engineer
ON Semiconductor
www.onsemi.com

Space and cost constraints have always been important factors in consumer electronic designs, so that products entering the market are sleek and attractive as well as having competitive price tags that will appeal to the public. In addition to satisfying these two requirements, increasing concern for impact on the environment means that, in recent years, power consumption has also become an important consideration for design engineers. This is highlighted by the recent changes that have been made to Energy Star directives.

Today, the majority of video entertainment systems still require an analog video signal. The most commonly used is the 1-channel Composite Video Blanking Sync (CVBS) signal, which is found on video output interfaces and is used to maintain a standard definition capability as a backup output. Primarily the three-channel YPbPr signal is needed for 1080i high definition (HD) analog video content. In order to comply with Energy Star, any DVD/Blu-ray player or set-top box must consume less than 1 W when it is in sleep mode. Table 1 gives further details.

Table 1: Energy Star Program Requirements for Audio/Video

Video signal detection

Semiconductor manufacturers serving the set-top box and DVD/Blu-ray player markets face major energy saving challenges when the system has to enter sleep mode. Here a certain proportion of the chipset’s functional blocks are turned off, including the integrated video digital-to-analog converters (DACs). Consequently, no more signals pass through the video drivers. Meanwhile various other functional blocks of the chipset are still fully active and drawing power. As these functional blocks are powered from the very same supply lines that are used by the video drivers, additional control is effectively imposed in order to activate/deactivate these drivers. Consequently, if no enable logic is present within the design, the power consumption will remain unacceptably high.

As a result there is a clear need for a video driver that has the capability to automatically detect the presence of video signals at its inputs so that no external control is called for to turn drivers on or off. However, the vital issue that needs to be addressed here is how long will it take to a driver to turn back on again after being in sleep mode — can it be activated fast enough to ensure that picture integrity is preserved? If this is not possible then this will impinge on the viewer’s experience.

Load detection

In addition to making energy savings through automatic video signal detection by the drivers, there are other areas where significant savings can be made. It can prove costly and difficult for the chipset to detect the presence of a TV on the RCA connectors dedicated to the analog video channels, especially when the output of the video drivers need to be ac-coupled. Some OEMs have investigated using a mechanical solution to solve this problem, with a switch being tripped when the cable is inserted, but this again would prove too costly. The possibility of integrating the load detection function into the video driver would again have serious benefits to completion of the design process.

The NCS2584 four-channel video driver IC from ON Semiconductor (see Fig. 1 ) is capable of automatically detecting the presence of video signals at its inputs and can turn each of the driver channels on or off respectively when the input signals are active or non active respectively. A signal detection block IP (patent pending) has been implemented which manages the timing so that when the chipset leaves sleep mode it becomes active again fast enough to avoid any loss of synchronization.

Fig. 1: NCS2584 functional block diagram

When the TV is not plugged into the CVBS and/or the YPbPr channels, the driver device goes into a low current shutdown mode with less than 10 µA being drawn. Meanwhile, when the TV is plugged into the analog channels, the driver can recognize its presence. Then, it verifies the input signal activity. If there is no signal activity, the device waits for the input video signal to wake up the system. Table 2 details this.

Table 2: Summary of NCS2584’s different devices states

In less than 2 µs of it detecting an input signal of a period greater than the length of a standard definition line (which is 63.556 µs) it automatically reactivates so that there is no loss of picture. In addition, its integrated load detection facility means that even during the video entertainment system’s regular activity the driver can manage its own power consumption and minimize loss of energy. Therefore the chipset does not need to manage detection of the presence of the TV connection, resulting in simplified chipset code and lower power dissipation. Furthermore, as this driver is not dependent of any specific chipset, thanks to its complete autonomy to manage output load detection, specifying it gives engineers a greater degree of design flexibility.

This latest generation of analog video driver devices that is now emerging needs to support the energy savings that have been outlined by the Energy Star program. Through the use of embedded detection features offered by certain driver ICs, engineers will not have to worry about how to go about improving the power efficiency of their design with respect to the analog video outputs. By placing greater functionality, such as video signal detection and load status monitoring, into the driver itself, control of the driving mechanism will be simplified and the system’s overall power consumption curbed. ■