Monostable comparator device

Abstract

A monostable comparator relates to overcurrent protection or short circuit protection of a switch power supply including a primary voltage circuit providing reference level for operation amplifier or a comparator, a single-way isolation circuit isolating level signals to ensure that current should flow to overcurrent detection circuit only and prevent energy fed back from the overcurrent detection current from leaking, an operation amplifier or comparator circuit generating high level output signals when input pulse signal is higher than the primary voltage, energy storage, feed back network and discharge circuit is the releasing channel of energy storage and feedback network.

Description

technical field [0001] The invention relates to overcurrent protection or short circuit protection of switching power supplies. Background technique [0002] For switching power supplies, due to load changes or abnormal loads, the switching power supply will be overloaded or short-circuited. Once overloaded or short-circuited, the current of the switching power supply switching tube and the output rectifier tube will be too large, especially in the short-circuit state. The current of the output rectifier tube is several times that of normal operation, causing the temperature of the output rectifier tube to rise sharply, and eventually damage the switching power supply. In addition, if there is a problem with the load that causes overload or short circuit, if the switching power supply cannot be protected in time, the load will be completely damaged, which may cause fire and other accidents. Therefore, it is required that the switching power supply must have over-current pro...

AI Technical Summary

Problems solved by technology

Since the output current decreases rapidly after the power supply is turned off, at this time figure 2 The output of the comparator becomes low again, so the output of the comparator is a spike signal, the time is very short, making figure 1 The charge of the external capacitor connected to the SS-SOFT pin of the chip cannot be completely discharged, and the power supply resumes to work at this time, but because the charge of the SS-SOFT pin capacitor has not been discharged, the initial output voltage of the power supply is not zero. If the output of the power supply is in a short-circuit state, it will cause a large current impact on the switch tube and rectifier tube. After multiple impacts, the temperature of the switch tube and rectifier tube will rise sharply. When the temperature of the switch tube and rectifier tube reaches a certain level will be damaged

[0005] image 3 The comparator is a self-locking comparator. When the power supply is over-current or short-circuited, the output of D301 is locked at a high level output through the feedback of the diode, so that the power supply is always in the off state. When the overload or short-circuit disappears, the power supply cannot To restore the work by itself, it is necessary to cut off the input voltage of the switching power supply, and then restart the power supply to restart the work, so it causes great inconvenience to the use of the power supply

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