Power adapter manufacturers need to embrace the new trend

Not long ago, the laptop is limited, such as the power requirement of only 50-70 watts (W). In recent years, power requirements, climbed to more than 100 W range, but the weight and size of the desired no corresponding improvement. In addition, the need to meet the low standby power adapter performance specifications, the harmonic efficiency requirements of the external power supply (EPS) and IEC1000-3-2 for more than 75 W of input power requirements make this challenge even more difficult to deal with. This article explores the recent trend of acer power supply manufacturers can address these challenges, and provide a different alternative solutions to choose from.

With laptops increasingly feature-rich electronic power requirements increase. In addition, because of the increased laptop battery capacity (or density), the charging requirements also increased – so, laptop power adapter for greater doubled. However, for millions around the world carry the laptop user, the larger and / or more thermal power adapter is not too attractive alternative. Can be attractive apple laptop adapter has a lightweight and small, but immediately charged. Of course, it does not produce heat, but does not spend too much. In recent years, the development of electronic products did not increase our hope in this regard, and whether the future of the revolution can be achieved is still an open question. We also want a asus notebook adapter can be used globally, without the need for a 110/220 volt operating voltage selector switch – laptop adapter must be truly universal line voltage work. At the same time, the expectations of regulators and OEM also play a role.

Regulatory agencies notebook adapter for compaq does not waste energy or electricity lines harmonics. The first factor is that the adapter does not insert the plug with no load, it should be as little as possible the absorption of the power (standby requirements). People generally used the laptop adapter for delta is plugged in, but not connected to the computer, the requirements can prevent the loss of this case. The second factor is the recent requirement, it requires specific average power efficiency under different load conditions (25%, 50%, 75% and 100%) by the global specification bodies perform, in order to promote compliance with the specification and reduce overhead costs. Finally, reduce the harmonic requirements enforced by the European Union and Japan have been used in dell laptop power adapter, because they have already exceeded these standards 75 W input power threshold. In a sense, the movement of the laptop adapter / Universal features making it the first mass production of power products IEC1000-3-2 specification.

Existing solutions and existing laptop converter general flyback topology, the pulse width modulation (PWM) converters. It was for many years the most effective solution (in terms of cost and technical). As shown in Figure 1, a typical flyback converter for laptop adapter for fujitsu at universal input voltage range (90-265 V ac), and ON Semiconductor has introduced a highly integrated PWM controller solution , the use of fewer components. If less than 75 W, the power level of the adapter without additional power section. The key performance criteria for these adapters is the power density (package size requirements), safety and low case temperature. The main method of control is to achieve classic UC384x series current mode control. However, as shown in Figure 1, the laptop hp ac adapter with different PWM controller (such as ON Semiconductor, the NCP1200). The new generation PWM controller is better than UC384x is:

The higher level of integration to reduce the number of external components, while still retaining the advantages of current mode control; * be able to enter skip mode to reduce standby and light load losses; * start input high voltage (HV), reduce the start-up circuit loss and component costs; without IC error amplifier circuit, error handling to be completed in the secondary; * easy to comply with safety and EMI, in order to market faster.

However, for more than 75 W power requirements of the hp compaq power adapter, the laptop manufacturers face a choice. Join the power factor correction (PFC) for universal application design adapter and need PFC (Europe and Japan) market segment or separate design. The increased PFC stage to increase the complexity and cost, make the design more challenging. Typical design applications in this application as shown in Figure 2 critical conduction mode (CRM) boost PFC stage.

CRM PFC design uses the MC33262 controller, as shown in Figure 2. This simple 8-pin controller can easily achieve liteon laptop power factor correction. In critical conduction mode, you can achieve some circuit level advantages, such as non-the diode recovery issues and lower switching losses.

Although manufacturers to adopt this approach has been embodied in the existing design performance and cost acceptable, but still need to be improved in order to meet growing emerging requirements.

In the PFC, although the main CRM methods, but there are obvious limitations. First, it is a variable switching frequency mode work in the zero crossing and under light load conditions, and the switching frequency may be increased to high. Variable frequency filter and low standby laptop power for ibm consumption problem. The NCP1601 introduced a new solution, it draws on the best features of the method of the critical mode, while limiting the switching frequency and improved standby performance. In this solution, the controller can seamlessly in discontinuous conduction mode (DCM) and critical conduction mode switch, and will not affect the sony ac adapter factor correction. The line voltage is at or near the zero-crossing and under lighter load conditions, the controller to work real fixed-frequency DCM PFC mode. Full load and near the peak of the waveform of the line, the controller switches to the critical mode, thus limiting the peak current value does not become too high.

In addition, in recent years, PFC implementation available discrete components come a long way. PFC MOSFET requires a rating of 500 volts, and the introduction of low Rds-on and a small gate charge MOSFET have a tremendous help. CRM or DCM boost diode circuit and manufacturers have begun to introduce a variety of components, such as MUR450PF, to cater to these needs require different characteristics.

The final result of these improvements is increased PFC adapter for toshiba design from a cost point of view, not a big burden, while at full load, low line efficiency of about 95% efficiency and <300 mW standby power consumption. These performance obviously adapter designed to meet OEM specification requirements.

From:http://www.cheapbatteryshop.co.uk