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A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of a power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage output (V o ), like dropping a crowbar across the output terminals of the power supply.
Circuit Diagram of a simple Crowbar Circuit, with an 8V nominal output (7.6V with SD1). Date: 06/05/06: Source: Own work, made in Livewire and Inkscape: Author: jjbeard:
Circuit diagram of a simple Crowbar circuit, with an 8V nominal output (7.6V with SD1). ...
When a circuit must be protected from overvoltage and there are failure modes in the power supply that can produce such overvoltages, the circuit may be protected by a device commonly called a crowbar circuit. When this device detects an overvoltage it causes a short circuit between the power supply and its return.
In electrical engineering, overvoltage is the raising of voltage beyond the design limit of a circuit or circuit element. The conditions may be hazardous. The conditions may be hazardous. Depending on its duration, the overvoltage event can be transient —a voltage spike —or permanent, leading to a power surge.
An inrush current limiter is a device or devices combination used to limit inrush current. Passive resistive components such as resistors (with power dissipation drawback), or negative temperature coefficient (NTC) thermistors are simple options while the positive one (PTC) is used to limit max current afterward as the circuit has been operating (with cool-down time drawback on both).
Although usually the result of a fault, there are cases where short circuits are caused intentionally, for example, for the purpose of voltage-sensing crowbar circuit protectors. In circuit analysis, a short circuit is defined as a connection between two nodes that forces them to be at the same voltage. In an 'ideal' short circuit, this means ...
SMPSs often include safety features such as current limiting or a crowbar circuit to help protect the device and the user from harm. [1] In the event that an abnormal high-current power draw is detected, the switched-mode supply can assume this is a direct short and will shut itself down before damage is done.