Over-current protective circuit and digital output circuit

Abstract

The invention provides an over-current protective circuit and a digital output circuit. The over-current protective circuit comprises a current limiting circuit, a timing circuit, a voltage regulating circuit and a comparator. When the digital output circuit is at an over-current status, the over-current protective circuit limits the current within a second threshold value by the over-current limiting circuit to determine the current at the over-current status, and outputs a first control signal by the comparator in the voltage regulating unit to control a switch tube to quickly switch off for closing the output, thereby ensuring the high switch-off speed at the over-current status without changing a fuse; when the switch-off time of the switch tube is longer than the first time timed by the timing unit, the voltage regulating unit outputs a second control signal to control the switch tube to switch on; and the switch-on time of the switch tube is the second time timed by the timing unit; and if the output is still at the over-current status, the output is closed again. According to the over-current protective circuit and the digital output circuit, the time for retuning output to normal is determined by repeatedly and periodically trying until the output is not at the over-current status.

Description

technical field [0001] The invention relates to the field of digital output circuits, in particular to an overcurrent protection circuit and a digital output circuit. Background technique [0002] In digital output circuits, in order to prevent overcurrent damage to devices, the method of blowing fuses or self-recovery fuses in series in the output circuit is generally used. [0003] When current flows through the fuse, the resistance of the fuse causes the fuse to heat up, and the amount of heat generated increases with time. The size of the current and its resistance determines the speed of heat generation, and the structure of the fuse and its installation condition determine the speed of heat dissipation. If the speed of heat generation is lower than the speed of heat dissipation, the fuse will not blow. If the rate of heat generation is equal to the rate of heat dissipation, it will not melt for a long time. Only when the speed of heat generation is greater than the s...

AI Technical Summary

Problems solved by technology

[0005] In view of this, the present invention provides an overcurrent protection circuit and a digital output circuit to solve the problem of insufficient fast protection of load equipment in the existing circuit, inconvenient use, difficulty in determining the magnitude of the current during overcurrent and the restoration of the self-recovery insurance The problem of uncertain timing

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