Development of electronic technology, multi-function mobile devices, the power supply circuit voltage becomes diversified. In a typical mobile phone, for example, the most basic function is to start talking, and now the development of diversified functions, such as: a variety of functions camera, radio, television, etc. has been very common. These functions work required voltages vary, therefore, the battery voltage must be through the power supply voltage conversion circuit converts the voltage of each circuit is required to work. It uses a high power conversion efficiency of the switching controller (commonly referred to as DC-DC converters).
In addition, the process of multi-function mobile devices, the machine is small, thin requirements have gradually improved. To this end it is necessary to reduce the number of components, or the component to do less. This strategy is borrowed from the increase DC-DC converter switching frequency, parameter values necessary to reduce the rated power inductors and capacitors, in order to adapt to the size of the element.
The centralized control of power PMIC (Power Management IC) switching frequency, 1MHz will have been changed to use 3MHz, as well as manage a separate power of DC-DC converter IC has been in the mainstream of frequency 3 ~ 4MHz, for such a case As the main component of power inductors need 1.0uH inductance values to 2.2uH low product. The number of higher switching frequencies enable squelch becomes necessary, in order to solve these problems, and promote the development of power inductors.
Mobile power supply circuit necessary characteristics of power inductors
In this elaborate multi-function mobile phone power supply circuit to the shape and characteristics of power inductors requirements. Mainly in the following three.
Small, thin
We have to adapt to the high power conversion efficiency of the power supply circuit characteristics
Have noise immunity in the work of state power
Murata has developed a corresponding demand for miniaturization of the power supply circuit laminate type power inductor LQM2HP (2520 size), LQM2MP (2016 size) series. These are in line with the set PMIC power inductors and power supply terminal baseband IC packaging and other 1.0mm thick slim design trends.
Developed for small power supply circuit laminate type power inductor
Corresponding to the small, thin power required inductance and its main properties
Paranoid characteristics of a good sense of value by the DC current, can be used as power inductors each specialty. Current - sense of paranoia characteristic value refers to the power inductor is energized, the current value becomes larger decline caused by a sense of nature. This is the magnetic flux closed magnetic circuit structure stacked power inductor saturation caused due, so in order to overcome this weakness, the development of new technologies to reduce stack ferrite magnetic flux distribution, thereby improving the current superposition characteristics, reflected in the final various products.
The power supply circuit (DC-DC converter) high power conversion efficiency characteristics
Associated with power conversion efficiency and power inductor DC-DC converter performance between shown in Figure 3. PFM refers to the phone in standby mode to maintain a low current load, then the power conversion efficiency of performance and power inductor Rac (AC resistance) and current - inductance characteristic related paranoid. Figure 4 which shows the characteristics of each power inductors Rac and the number 5 in the switching frequency is 4MHz power conversion efficiency of DC-DC converter IC's.
Rac properties, LQM products can be sufficiently inhibited Rac. Meanwhile, the current - sense of values displayed paranoid characteristics, it is energized when the current value but also to ensure a high sense, with good power conversion efficiency characteristics. These properties enable the phone high power conversion efficiency in standby mode, and contribute to longer battery life.
On the other hand, PWM mode refers to call state equivalent high current load condition, this mode and inductance Rdc characteristics (DC resistance) related to a low Rdc performance LQM series in this area has good power conversion efficiency.
Anti-noise performance measures
The DC-DC converter using the phone's power supply circuit, the magnetic flux leakage inductance of the power used may induce an unstable power supply circuit, resulting in a bad influence to the circuit. These problems can be through the use of magnetic flux leakage inductance less power to solve the multi-layer, can prevent noise power supply circuit remains stable. Further, the magnetic flux leakage less electromagnetic coupling also enables the power supply circuit and signal lines, peripheral weakened, noise suppression induced signal purity deterioration.
Wire-wound power inductors and power inductors stacked magnetic flux leakage monitoring data. As has been compared to the DC-DC converter using the main power inductor winding type power inductors, power inductors stacked magnetic flux leakage less, it has now been confirmed closed magnetic circuit structure so that less magnetic flux leakage. These data suggest that the case of the use of small power inductors stacked in small high-speed switching DC-DC converter circuit, it is possible to play it anti-noise characteristic strengths.
Small, thin portable devices demand prompted mounted on the component size must be smaller and smaller. DC-DC converter power supply circuit in a small, thin allows higher switching frequencies, the surrounding components more compact. Murata development process for small-scale power inductors stacked goods, the manufacturing excellent addition to the current - sense of value paranoid characteristics, magnetic flux leakage power is less in 1008 and 0806 the size of the product. Further development of the future will be more miniaturized 0805 and 0603 multi-layer power inductors, high-performance compact power circuit design for portable devices contribute