A Crowbar is an electrical circuit, usually used to prevent overvoltage from a power supply unit from damaging some downstream circuit. An electrical crowbar operates by throwing a short circuit across the voltage source, much as if one dropped its mechanical namesake across the output terminals of the power supply. Crowbar circuits are frequently implemented using an SCR (or a trisil or thyratron) as the shorting device. Once triggered, they depend on the correct functioning of the power supply's current-limiting circuitry or, if that fails, the blowing of the line fuse or circuit breaker. An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ... A power supply unit (sometimes abbreviated power supply or PSU) is a device that supplies electrical power to a device or group of devices. ... For alternate meanings see Short circuit (disambiguation) A short circuit (sometimes known as simply a short) is a fault whereby electricity moves through a circuit in an unintended path, usually due to a connection forming where none was expected. ... This article may be too technical for most readers to understand. ... A crowbar is a tool consisting of a metal bar with one curved end and flattened points, often with a small fissure on the curved end for removing nails. ... Circuit symbol for a thyristor The thypissor is a solid-state semiconductor device similar to a diode, with an extra terminal which is used to turn it on. ... Trisil is an electronic component designed to protect electronic circuits against overvoltage. ... A thyratron is a type of gas filled tube used as a high energy electrical switch. ... The word current usually implies a flow or movement. ... 200 A Industrial fuse. ... A circuit breaker is a piece of equipment which is designed to protect an electrical apparatus from damage caused by overload or short circuit. ...
A crowbar is distinct from a clamp in that, once triggered, it pulls the voltage below the trigger level. A clamp holds it at the trigger level. Thus, a crowbar will not automatically return to normal operation when the overvoltage is removed; power must be removed entirely to reset it.
The great advantage of a crowbar over a clamp circuit is that the low triggered voltage lets it carry a much higher fault current without overheating.
The term is also used as a verb to describe the act of short-circuiting the output of a power supply.
The hold circuit capacitor 40 holds the output from the comparator 36 at the inverting input to the op amp 78 in the cyclical shutdown circuit 44, thereby causing the op amp 78 to turn off the transistor pass element 22.
The hold circuit 40 holds the output from the comparator 36 at the inverting input of an op amp 78 in the cyclical shutdown circuit 44, even after the transistor pass element 22 is switched off and the comparator 36 discontinues the fault signal.
The pulse width modulation circuit 20 of the present invention protects the transistor pass element 22 from an overcurrent situation caused by a cold positive temperature coefficient load 23 or a short circuit of any cause and allows the transistor pass element 22 to be chosen for optimal steady state operation.
A crowbar and the claw of a hammer used to pry loose nails are both common examples of levers in action.
A crowbar, also called a pry bar or prybar, or more informally known as a jimmy, jimmy bar [ citation needed ] or jemmy (British Isles), is a tool consisting of a metal bar...
Crowbar may refer to: Crowbar (tool) Crowbar (circuit), an electrical circuit;Crowbar (US band), a doom/sludge metal band from Louisiana; Crowbar an album by the U.S. band...
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