Can zero standby power consumption technology be achieved?

Five years ago, when many manufacturers proposed to reduce standby power consumption to below 1W, many people exclaimed that it was an unattainable "myth"! But in the end, this so-called "myth" finally became a reality. Now, some manufacturers have begun to impact zero standby power consumption. I believe that this technology will once again refresh our understanding of standby power consumption.

At the 2011 IIC-China, PI demonstrated two zero standby power consumption solutions, one of which was based on its integrated offline switch IC - LinkZero-AX, which attracted many whole machine design engineers. We all know that when electronic products are in standby mode, the main power supply is usually not working, while the auxiliary power supply is in working state. PI's LinkZero-AX adopts a new power-off mode, which can effectively shut down the auxiliary power supply when the power supply is unloaded. The power-off mode can be triggered by a signal obtained by the microcontroller, which can completely shut down the switch operation and the internal switch control circuit, thereby eliminating the energy wasted by these unnecessary functions. In the power-off mode, LinkZero-AX does not terminate the work, and the IC can be awakened by a reset pulse or a key operation.

"In fact, the zero standby power consumption mentioned here does not mean that the standby power consumption is completely zero, but that the standby power consumption is reduced to a very low level. Generally, 10 mW of standby power consumption can be measured, but it is difficult to measure below 10 mW, so it can be called zero power consumption!" said Doug Bailey, vice president of marketing at Power Integrations. Actual measurements show that LinkZero-AX can reduce the standby power consumption of high-power consumer products and electrical appliances to 4 mW, or even close to zero watts. (According to Article 4.5 of IEC 62301, standby power below 5 mW is considered zero power consumption.)

As energy conservation and environmental protection become a consensus, lower standby power consumption technology has also attracted the attention of consumers. It is understood that the power consumed by electrical products in standby mode has become a serious waste of energy. According to a survey by the China Energy Conservation Product Certification Center, there are nearly 10 kinds of household appliances with standby function in a city household, and the average monthly standby power consumption is between 15-30 watts, which accounts for about 10% of household electricity consumption. In other words, one tenth of the electricity bill you pay every month is for standby, so there is still potential for energy-saving technology to be further explored.

"Another standby phenomenon is the charger. For example, after the mobile phone charger is fully charged, many users do not turn off the power in time, causing the charger to continue to consume current in the standby state." Doug emphasized, "After adopting our solution, this phenomenon can be prevented." In response to this zero standby demand, PI launched the LinkZero-LP product, which is suitable for chargers and adapters. LinkZero-LP uses a new control technology that enables the device to automatically enter the no-load mode and can be awakened from the no-load mode, and the no-load power consumption is also 4 mW - this is far lower than the zero no-load power consumption standard specified by IEC.

“LinkZero-LP can automatically monitor the load and enter power-off mode when the load is removed, and automatically reactivate when the load is applied again.” Doug pointed out, “In addition, the IC power supply during startup and operation comes directly from the drain pin, without the need for a startup circuit. The jittering of the internal oscillation frequency greatly reduces the quasi-peak and average EMI, thereby reducing the cost of the filter.”

Currently, PI provides a low-power zero-standby solution, as shown in the figure below.

Figure 1 PI 2.1W CC/CV charger solution, based on PI LinkZero-LP device, with standby power consumption close to 0

Figure 2 PI 1.5W non-isolated flyback power supply, standby power consumption close to 0

Doug revealed that PI will develop zero standby power consumption products in two directions in the future. One direction is to further reduce standby power consumption and develop towards true "zero power consumption", and the other direction is to expand the application field of products to higher power products, such as white household appliances, large electrical equipment, etc. As flat-panel digital TVs become increasingly popular, it takes time to start them up. In addition, many users have already known that the transient current during startup is very harmful to home appliances. Therefore, many Chinese users no longer use the direct power-off mode used in the CRT TV era, but put the appliances in standby mode. Such usage habits urgently need the launch of zero standby power consumption products.

Now, in addition to PI, Fairchild Semiconductor, NXP and other companies have also begun to launch zero standby power consumption products. I believe that in the near future, zero standby power consumption appliances will usher in an era of popularization.

Background knowledge: Analysis of the standby power consumption mechanism of switching power supplies

At present, most electronic devices below 100W, such as power adapters, chargers, cordless phones, ADSL routers, LCD monitors and DVDs, etc., use offline flyback switching circuits to convert the 85V~275V AC power provided by the power grid into the DC voltage required by electronic devices. Under normal working conditions, the losses of flyback switching power supplies mainly include conduction losses and switching losses, as well as control circuit losses. In standby mode, since the output current of the system is close to zero, the conduction loss can be ignored, and the switching loss and control circuit loss become the main system standby power consumption. To reduce standby power consumption, we should focus on reducing switching losses and control circuit losses.

The figure above shows the main loss types of the flyback switching power supply in standby mode. Its power tube switching loss, drive loss, transformer core loss, output rectifier tube reverse recovery loss and buffer loss are all switching losses. Various types of switching losses are related to the switching frequency. Reducing the switching frequency can reduce switching losses. The loss of the control circuit is mainly manifested as the loss on the starting resistor, and the loss of the starting resistor is directly related to the DC bus voltage after rectification and the value of the starting resistor. Under the working condition of ensuring a wide voltage input, the starting resistor loss can be reduced by reducing the starting current.