Mobile phones, portable music players, portable game consoles, laptops and other portable electronic products exist in our daily lives. These portable electronic products are powered by batteries , and each machine is equipped with multiple power supply voltage conversion circuit (DC-DC) converters that convert the battery voltage into the voltage required by the functional modules.
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There are many types of DC-DC converters, and those used for portable electronic devices are mainly non-isolated conversion power supplies. This non-insulated switching power supply has a circuit breaker type using a coil and a supply pump type mainly using a capacitor. For example, a lithium battery mainly used for portable devices may have a change in battery voltage, and a supply pump type DC-DC converter is widely used because it can maintain a high power conversion efficiency when the battery voltage changes.
The types of power supplies required for portable electronic devices vary greatly depending on the type and function of the machine. Therefore, the input and output voltage and current specifications and volume of the DC-DC converter are also very different. The size and performance of coil components (power inductors) used in these DC-DC converters are also diverse.
Murata has two types of power inductors, laminated and wound, which can be applied to various DC-DC converters for portable electronic devices.
This time, it is applicable to a wide range of winding power inductors (LQH series) from small portable devices such as portable music players to large portable electronic devices such as notebook computers.
Summary of the LQH Series
The product line of the wound-type power inductor LQH series is shown in Table 1.
Table 1: List of power inductor LQH series product lines
The LQH series is available in a variety of different sizes of winding inductance. The LQH2MC_52 series is the smallest size for small LCD modules such as mobile phones; the AQH55P_R0 series is the largest size for notebook hard drives and digital cameras.
The most suitable sense value can be selected according to the performance requirements and size requirements of various DC-DC converters.
LQH2MC_52 series
Introducing the smallest and thinnest LQH2MC_52 series in the LQH series.
Figure 1 shows the outline drawing of the LQH2MC_52 series.
Figure 1: LQH2MC_52 series outline drawing
Portable devices such as portable music players and mobile phones are becoming more and more high-performance, multi-functional, and power-saving. More and more DC-DC conversion circuits are used, and DC-DC conversion circuits are miniaturized and thin. It has become indispensable. The power inductor used under such a trend also requires miniaturization and thinning. The LQH2MC_52 series is based on a unique material and molding technology. The ultra-thin ferrite core and highly coiled wire and terminal processing technology realize a small ultra-thin size power inductor of 2.0×1.6×0.70m, which is especially suitable for portable music. LCD screen for players and mobile phones. In addition, according to the above technique and the magnetic circuit design technique, it is possible to obtain a maximum value of 10 μH which satisfies the actual demand (Table 2), and at the same time achieve excellent DC overlap characteristics (Fig. 2).
Table 2: LQH2MC_52 Series Rating Table
Figure 2: LQH2MC_52 Series DC Overlap Characteristics
Fig. 3 shows the evaluation results of the power supply voltage conversion efficiency when the LQH2MCN2R2M02 and LQH2MCN2R2M52 are used in the step-down DC-DC converter . Although the LQH2MC_52 series is a miniaturized product with a maximum thickness of only 0.7 mm, it has the same high power supply voltage conversion efficiency as the LQH2MC_02 series with a maximum thickness of 0.95 mm.
Figure 3: Voltage conversion efficiency of a step-down DC-DC converter (PWM type)
LQH55P_R0 series
Next, the power inductor LQH55P_R0 series corresponding to a large current is introduced. Power inductors used in digital still cameras (DSCs), notebook computers, and 3.5/2.5-inch HDDs must be capable of handling large currents while requiring low DC resistance values.
The winding type power inductor mentioned here can achieve higher magnetic shielding and lower DC resistance. If the magnetic shield is high, the magnetic flux will not leak to the outside and be constrained inside by the ferrite core, thereby obtaining a large inductance. Therefore, using a thicker winding can obtain a sense value and a lower DC resistance value with a smaller number of turns.
Figure 4: LQH55P_R0 series outline drawing
On the other hand, once the magnetic shielding energy is increased, the DC overlap characteristic is deteriorated.
The LQH55P_R0 series is coated with magnetic resin around the coil to improve magnetic shielding, which results in lower DC resistance. In addition, the coating amount of the magnetic resin is controlled by a precise coating technique to adjust the actually effective μ and control the required inductance and DC overlap characteristics. Fig. 5 shows the DC superposition characteristics when the amount of the magnetic resin coating is changed. The precision magnetic resin coating technology allows for the minimum sense of inductance to be maintained at higher currents, as well as the DC overlap characteristics such as reduced initial inductance values ​​to be freely controlled.
Figure 5: Relationship between the amount of magnetic resin coating and the sensitivity and DC overlap characteristics
Table 3 and Figure 6 show the rated ammeter and DC overlap characteristics of the LQH55P_R0 series.
Table 3: LQH55P_R0 Series Rated Table
Figure 6: LQH55P_R0 Series DC Overlap Characteristics
to sum up
Portable electronic devices use a variety of DC-DC converters, and are available in a variety of modules for machines and power supplies. The power inductors used in these DC-DC converters also have to be varied in size and performance.
Murata has a winding-type power inductor with various sizes and performance variations for various DC-DC converters.
In order to continue to provide the most suitable power inductor for a wide variety of DC-DC converters for portable electronic devices, we will further improve the performance of power inductors while further expanding the size and model, and make our contribution to the low power consumption of the machine. .
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