Tighter EU legal limits on standby power consumption: could simple new power ICs come to the rescue?

Read this to find out about: 

• The scope and requirements of the new EC regulation 2023/826
• How power ICs that eliminate the X-capacitor bleed resistor in power supplies save no-load power
• Evaluation boards and reference designs for ac-dc power supplies that comply with 2023/826

In tune with the European Commission (EC) commitment for Europe to be a climate-neutral continent by 2050, new regulations coming into force in 2025 will clamp down on the amount of power that almost all types of domestic electronic equipment are allowed to dissipate when off or in standby mode.

According to European Union (EU) research, annual energy consumption of household equipment in off mode or a standby mode was an estimated 59.4 TWh in 2015. This power wastage was responsible for the emission of 23.8 million tonnes of CO2 equivalent greenhouse gases.

Now device manufacturers are to be compelled to design products to bring the standby power consumption within strict limits. But this will not always be a complicated and expensive effort: as this article explains, a simple IC added to an ac-dc power converter can on its own yield a substantial saving in power consumption whenever a device is plugged in.

Broad scope of new Ecodesign requirements

The new EC regulation 2023/826 on standby power comes into effect from 9 May 2025: the goal is to cut annual energy consumption in Europe by 4 TWh. This is an ambitious target: it is to be achieved by regulating the power consumption of a very broad range of household products and of office equipment intended for use in a domestic setting.

The regulation applies to products with an integrated power supply. Products equipped with a low-voltage external power supply are not currently included in its scope, but manufacturers would be wise to expect to be required to comply sooner or later, as the EC is likely to want to provide a level playing field for competition between manufacturers.

The types of device which are listed in the regulation include kitchen equipment such as toasters and microwave ovens, white goods, IT equipment except products such as laptop computers that are covered by specific Ecodesign regulations, audio-visual equipment, toys, sports equipment, and products which contain a motor, such as power-operated furniture and beds, and motorized blinds and shutters. A full list can be found at the EC EUR-Lex law website.

The limits on energy consumption are tight: a maximum of 0.5 W in off mode, falling to 0.3 W after two years. Standby mode limits vary. If the device only maintains a reactivation function and indicator, the limit is 0.5 W. If a status or information display is active, the limit rises to 0.8 W for most products.

Still higher limits are applied to products which operate in networked standby. Networked standby means a condition in which the equipment is able to resume a function by way of a remotely initiated trigger from a network connection. Products that are classed as having high network availability (HiNA) capability, such as routers and gateways, must not use more than 8 W in networked standby. For non-HiNA products, networked standby power consumption is to be limited to 2 W.  

A cheap and easy fix for high standby power consumption

A strategy for ensuring compliance with regulation 2023/826 should consider power consumption across the system as a whole, including in functions such as control, interfacing and sensing. But a fertile source of savings is sure to be the power-supply circuit, and one of the quickest and easiest ways for many OEMs to cut standby power consumption is by eliminating the continuous power drain through the EMI filter’s X-capacitor bleed resistors.

These resistors are found in the power supply of many household appliances and consumer devices to provide for compliance with IEC 60335-1, a safety standard for these products which specifies that the power supply’s X-capacitor needs to be discharged below 34 V within one second after the device is powered off.

A typical EMI filter is shown in Figure 1. C1 and C2 represent the X-capacitors; R2 ensures that the X-capacitors are discharged after the input voltage is removed. The capacitance of the X-capacitors can vary from hundreds of nanofarads for low-power converters, up to some microfarads in higher-power converters.

To take an example, for a capacitor of 2.2 µF specified with a tolerance of ±20%, the maximum capacitance will be 2.64 µF. The mains input voltage is up to 264 V ac, 240 V ac +10%. To discharge the capacitor to 34 V within one second, a resistor of 184 kΩ is required. This bleed resistor will dissipate 377 mW.

Fig. 1: In this typical EMI filter, the bleed resistor R2 draws a continuous current as long as the device is plugged in

This circuit configuration makes it almost impossible to comply with the new standby power consumption regulation: the 377 mW dissipation continues all the time that the device is plugged into a mains power socket, whether the device is active, quiescent, or switched off.

Fortunately, it is easy to add a simple integrated circuit to stop power consumption through the bleed resistors except when the X-capacitors need to be discharged. Examples include the CAPZero-2 or CAPZero-3 from Power Integrations, the HF81 from Monolithic Power Systems, and the TEA1708T from NXP Semiconductors.

These components are all of a similar design. They consist of MOSFETs with integrated drivers, plus voltage sensing and other circuits, and are placed in series with the bleed resistors. During normal operation, when an ac voltage is present, the MOSFETs are off, and so the resistors are disconnected and no current flows through them. When the device is unplugged and the ac voltage is removed, the MOSFETs turn on to bring the resistors into the circuit, which then discharge the X-capacitors.

Fig. 2: Typical high-voltage motor control board, showing the CAPZero-2 X-capacitor discharge circuit

Tests performed by Monolithic Power Systems reveal the huge power saving that can be made by using the HF81 in this way: the test results are published in the datasheet of the HF81, shown in Figure 3. For the example above of an X-capacitor of 2.2 µF, the saving made by using the HF81 would bring power dissipation through the bleed resistors to below 200 mW, low enough to allow for compliance with the 2023/826 regulation.

Separately, Power Integrations and NXP specify the power dissipation of their ICs at less than 5 mW.

Fig. 3: power savings made by replacing a conventional X-capacitor discharge circuit
with one based on the HF81 from Monolithic Power Systems. (Source: Monolithic Power Systems)

The solution shown in Figure 2 provides a way to cut the power wasted through the bleed resistors: this can be implemented as a cheap and easy modification of an existing power supply design, with minimal change to the bill-of-materials or board layout.

For new designs, however, OEMs have the option to choose from a new generation of power controllers that include an integrated X-capacitor discharge circuit. Examples are:

• HR1275 from Monolithic Power Systems, a combination controller with multi-mode PFC and LLC power stages
• TEA2017 from NXP, a combination controller with multi-mode PFC and LLC power stages
• NCP1618 from onsemi, a multi-mode PFC controller
• HiperPFS-5 from Power Integrations, a quasi-resonant PFC controller with integrated gallium nitride (GaN) FET
• L4985 from STMicroelectronics, a PFC controller which operates in continuous conduction mode

These suppliers are innovating in product designs to save even more power in standby mode. For instance, many work in burst mode when the load is below a certain threshold, allowing the power-supply control and switching circuits to be intermittently disabled.

The scale of the improvements that can be made are substantial: with the TEA2017, NXP has reduced low-load and quiescent mode power consumption compared to its predecessor part, the TEA2016, as shown in Figure 4.

Fig. 4: Efficiency graph showing the reduced power losses at low load in the latest
TEA2017 power controller from NXP Semiconductors (red curve) compared to the TEA2016 (pink curve) 

Implemented in an NXP evaluation board, the TEA2017DK1003, a 600 W offline ac-dc converter with a 12 V output, the TEA2017 enables the power supply to reduce no-load power consumption to 0.11 W with a 230 V ac input. The TEA2017 also provides the main power control functions in the new Lightning ac-dc converter board developed by Future Electronics’ European Power Design Centre. Technical information about the Lightning board, which provides a 42 V dc output and supports loads of up to 240 W, can be found at www.my-boardclub.com, where engineers can also apply to receive the board.

Power Integrations, onsemi and ST also supply evaluation boards which demonstrate the capability of controllers with integrated X-capacitor discharge to support compliance with regulation 2023/826.

Power Integrations provides the DER-672, a 220 W evaluation board which achieves no-load power consumption of 120 mW at 230 V ac thanks to the PFS5178F, a quasi-resonant PFC controller with GaN FET, operating in discontinuous conduction mode.

From onsemi comes the NCP13994MM360WGEVB, a 360 W evaluation board in which the NCP1618 multi-mode PFC controller is used in conjunction with the NCP13994, the latest current-mode LLC controller. At 230 V ac, the no-load power consumption of the NCP13994MM360WGEVB is 100 mW.

ST, on the other hand, supplies a 400 W evaluation board, the EVL400W-80PL, in which the L4985A PFC controller operating in continuous conduction mode achieves no-load power of less than 150 mW at 230 V ac.

Component market responds to demand for compliance with standby regulation

The TEA2017 and the other new and improved products featured in this article show that the component market is ready to provide various solutions to power-supply designers who face the task of achieving compliance with the tight restrictions on standby and off-mode power consumption specified in the latest EU regulation.