Integrated Inductive Switch-mode Power Supply : Fundamentals on Power Stage

Static conversion of electrical energy takes the form of switching converters. Here, we're talking about the conversion of one DC voltage level to another, whose amplitude is either greater or smaller. This is also referred to as a switching voltage regulator, in reference to linear voltage regulators. The desired function is to create a (DC) voltage level of precise value, to power a function. In low-power electronic products, these converters are numerous. They are even more numerous when the electronic product is battery-powered. All nomadic devices generally meet this criterion, but a modern LED television set poses the same energy conversion constraints, but in this case the initial voltage is produced from the electrical grid.

Until recently, the voltage regulator (type 7805) was designed to generate a precise DC voltage (in this case 5 volts) from a more or less regulated primary DC voltage source (in this case at least 9 volts for the 7805 circuit). With the democratization of small batteries, it has become necessary to think in terms of conversion efficiency, for the purpose of autonomy. In fact, for a linear voltage regulator there is an efficiency in the ratio between its output voltage and its input voltage. If the voltage to be generated is half the input voltage, 50% of the energy is dissipated as heat. Electronic products are often manufactured using CMOS technology, and their supply voltage is becoming ever smaller as technology advances. What's more, the electronic circuits fed by the voltage regulator can show very rapid variations in consumption (the inrush current). To maintain the output voltage at its nominal value, a control loop must be set up. It is now also necessary to adjust the DC voltage value in real time. The role of the control loop, or closed loop or control scheme, will be twofold. Even triple, if we consider that the input voltage (battery) will vary inexorably during discharge and charge cycles. Here again, the control loop must maintain the output voltage at its nominal value. A linear regulator can do this, but so can a static switching converter, and its energy efficiency has been shown to be superior to that of a linear voltage regulator [D3075] .

The context of this article, therefore, is the powering of integrated electronic circuits from a low voltage, a battery for example, i.e. between 5 volts (the load), 3.3 volts (the nominal voltage) and 2.7 volts (the low limit voltage) in the case of a standard lithium-ion cell. The advanced...