Matthias' Blog

In this article, I will describe an algorithm that can be used to compute component values in a passive filter circuit from the filter circuit's transfer function or poles and zeros. For this article, I will consider a passive filter circuit to be a filter circuit with one input and one output consisting of only ideal inductors, capacitors, and resistors with positive values. Inductance, capacitance, and resistance matrices Consider the following circuit: This circuit has 5 nodes (\(V_i\), \(V_g\), \(V_1\), \(V_2\), and \(V_3\)) and 5 components. Recall that the impedance of an inductor is \(j\omega L\) and the impedance of a capacitor is \(\frac{1}{j\omega C}\). Thus, for example, the current through \(L_1\) is \(\frac{V_i - V_3}{j\omega L}\). For nodes \(V_1\), \(V_2\), and \(V_3\), we want to calculate the total current flowing into the node. By Kirchoff's current law (KCL), the total currents flowing into each node must be zero (i.e. what comes in must come out). Thu

In this article I will show how you can turn a buck converter module (like the one shown below), which can only output a voltage lower than the input voltage, into a buck-boost converter module, which can output a voltage that is either lower or higher than the input voltage. Buck converter theory The schematic of a buck converter is shown below: Link to simulation The components in the box, in addition to the feedback loop (not shown), are usually integrated into a single chip. A regular buck-converter works by switching current into the output capacitor through an inductor. When the transistor in the box is on, current can flow from the supply to the output via the inductor. The voltage across the inductor is \(V_{in}-V_{out}\) and the rate of change of the current is \(\frac{V_{in}-V_{out}}{L}\). When the transistor in the box switches off, the current in the inductor continues to flow, but now through the diode. The voltage across the inductor is \(V_{out}\) and the rate of