ЭНЕРГОРЕСУРСОСБЕРЕЖЕНИЕ И ЭНЕРГОЭФФЕКТИВНОСТЬ Achieving very low or zero standby power for AC/DC power supplies European Power Design Services Group, Freising, Germany In the future the average household will have more than 60 devices plugged in and on standby 24 hours a day. <...> From coffee machines and TVs, to chargers and smart plugs, these devices can cost households hundreds, even if inactive. <...> But while consumer demand for electrical goods increases, global energy standards are driving the need for reduced standby loss. <...> The European Commission Code of Conduct (COC) and the US Department of Energy (DOE) define standby power standards for power supplies when they are on, but disconnected from a load. <...> The Energy Star program, developed in the US and expanded to the EU, for cell phone charger limits the no-load power to 30 mW for the highest 5 star. <...> At low power levels, the flyback topology is probably the best choice for an offline design. <...> It is one of the least expensive isolated topologies because it uses a very low number of components. <...> In the past, an optocoupler was usually used to regulate the secondary side output but modern quasi-resonant (QR) flyback controllers provide primary side regulation, enabling designers to bypass the optocoupler altogether. <...> This makes it among the most cost-effective isolated offline topologies, because a simple resistor divider connected to the bias winding is sufficient to regulate the output voltage. <...> This article focuses on achieving low standby power for a primary-side regulated QR flyback. <...> After the core of the transformer is completely demagnetized (secondary side current has ramped down to zero) there will be a resonant ringing, caused by the primary inductance and the energy stored in the parasitic switch node capacitance. <...> The controller detects the valley of the resonant ringing and turns on the MOSFET. <...> The switching frequency varies in order to have the switching event happen on a valley. <...> The lower switchnode voltage at the valley reduces switching losses. 31 VDC Standby power The total standby power consists of two main components. <...> The first main component is the energy, which is taken every switching cycle from the input, and the second main component is the loss of the startup circuit <...>