Block capacitor
Block capacitor (also blocking capacitor , backup capacitor or filter capacitor ) describes a capacitor in electrical engineering that maintains the operating voltage in local circuits in a circuit. The operating voltage collapses in a pulsed manner during switching operations. These are caught or blocked by the capacitor by absorbing energy or releasing previously stored energy and thus protecting against voltage drops. Compared to other types of energy storage , the capacitor performs particularly unfavorably, but it is significantly faster in taking up or releasing its charge compared to other storage devices .
A blocking capacitor is also used to denote a capacitor which diverts the alternating voltages superimposed on a direct voltage to ground, effectively blocking undesired frequencies .
Capacitors were needed at the beginning of industrialization as early as the 19th century. In telegraphy , capacitors were used to screen undesired interference on the lines. In the emerging telephone systems , capacitors were also needed “in the supply circuit of central battery stations in order to keep away the disturbances caused by the battery charging apparatus, such as buzzing and other noises” (original text, 1912).
From around 1850, mica , a naturally occurring mineral , was cut into slices and used as an insulator for capacitors. Paper capacitors with metal foil coatings have been in use since 1876 and 1900. These were already significantly smaller than mica capacitors with the same capacitance . Since both types of capacitors were manufactured as cuboid "blocks" and diverted the superimposed alternating voltages to ground in direct current circuits, "blocking" them as it were, it made sense to call this ability of these block capacitors "blocking". The term "blocking" is still used today for circuits with capacitors that suppress unwanted interference, "seven" the interference frequencies, so to speak.
In analog circuits , block capacitors reduce distortion, in digital circuits they prevent malfunctions and in processors and microcontrollers the brownout .