Research On Miniaturization Of Power Supply Models Based On LTCC Technology

In recent years, all kinds of electronic products and devices have became more and more small, light and high reliability, especially that in the modern portable devices, this trend is particularly prominent. The power supply system is an indispensable module in every electronic product, acting as the source of energy for the whole electronic equipment. So the power supply system should have the characteristics of small size and high integration. In the conventional power systems, magnetic devices usually occupy a large area, which is the biggest limitation of the miniaturization of the system. The inductance embedded in the magnetic substrate can be made by low-temperature co-fired ceramic(LTCC) technology. The circuits can be printed on the surface of the magnetic substrate. So that it is not only the carrier of the circuit, but also a component in the circuit. In this paper, we take the Buck DC-DC converter as an example to achieve miniaturization of the power supply systems.First,the topology of the power supply and how the circuit works are introduced. The difficulties of the miniaturization through LTCC technology are analyzed. The requirements of magnetic material which is used to made inductance are proposed. The DC-DC circuit is designed and analyzed, and its performance is also optimized by tuning. Finally, we got a DC-DC converter circuit, which has the input voltage range of 3-5 V, the output voltage 1.8 V and the maximum operating current 2 A. The 2 MHz circuit switching frequency is selecting to reduce the external circuits.Next, the power inductor has been designed. In order to improve the inductor DC bias ability, the nonmagnetic air gap is introduced to the inductor by using the matching co-firing technology. The equivalent circuit diagram of the inductor which has the air gap is analyzed. The simulation result of the inductor is got by putting the magnetic material permeability 70 into the software Ansoft Maxwell. The influence of the magnetic properties and the air gap to the DC bias of the inductor are studied. The 1.2 μH inductor which has the saturation current more than 2 A is designed.Finally, the converter is designed and fabricated, basing on the circuits and inductor structure. The metal shielding layer is introduced to reduce the interference of the inductor. The circuit is printed on the no-magnetic layers to reduce the coupling effects. The volume of the whole converter is: 20 mm × 15 mm × 1 mm. The final results of the test showed that the circuit output voltage 1.8 V. The work current can meet the requirement 2 A. The efficiency of the entire circuit is 85%.