Power supplies, such as switching power supplies, are used for providing direct current (DC) supply for various electronic devices. Such power supplies may be connected at the electrical power input of a device, or they may convert power for a specific part of a device, for example. Power supplies are nowadays usually implemented with switched-mode converters. The input of a switched-mode converter may be AC or DC current, and input/output voltages vary according to the implementation. While most electronic devices have switched-mode power supplies for providing the operating power it is essential that the switched-mode converters have a good efficiency.
Switched-mode converters use input current for charging energy to an inductor in one phase, and in another phase the charged energy is led to load. These operating phases are switched with high frequency. The basic structures of switched power supplies include boost-type converters which increase the voltage, and buck-type converters which decrease the voltage. In the boost type power supply the input power is led to the load with an inductor, wherein a transistor connects the inductor directly to the input voltage in a first phase for loading energy to the inductor, and in a second phase the charged inductor is connected to the load for supplying energy with higher voltage. In the buck-type converter a current flows continuously in the circuit of an inductor and a load A transistor sequentially connects the input voltage to the circuit thus increasing the energy of the inductor in a first phase, for being used in the load in a second phase.
Additionally there exist combinations of the basic switched-mode converter types, such as converters based on resonance, and cascade-type converters for increasing voltage. Simple switched-mode power supplies typically have efficiency between 70% and 90%. For example, nominal efficiency of a boost-type power supply is typically 70% and efficiency of a buck-type power supply is typically 80-90%. There are also power supplies with higher efficiencies, such as split-pi type switch power supplies where several transistors are used for connecting the input energy source to feed several inductors sequentially so that the current from the input voltage source is almost even. This minimizes losses caused by current changes and current spikes, and it is possible to achieve efficiencies that are higher than 90%. However, this solution leads to a more complicated structure and therefore higher production costs.
The following two documents disclose interleaved converters with two sequentially switched, parallel inductors: Taufik Taufik, Tadeus Gunawan, Dale Dolan and Makbul Anwari, Documents Design and analysis of two-phase boost DC-DC converter World Academy of Science, Engineering and Technology, issue 43, 2010, and Mounica Ganta, Pallam Reddy Nirupa, Thimmadi Akshitha, Dr. R. Seyezhai, Simple and Efficient Implementation of Two-Phase interleaved Boost Converter for Renewable Energy Source, International Journal of Emerging Technology and Advanced Engineering Volume 2, Issue 4, April 2012. The solution is based on a number of boost converters connected in parallel. This solution has advantages in applications with very small power, but technology would not be suitable for other applications.
The majority of power supplies are implemented using either of the two basic converter structures. Therefore the power losses form a large portion of electrical energy consumption. Additionally, power losses of the prior art power supplies heat the devices and cause their operating life to become shorter.
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