MOS tube overcurrent protection system

Abstract

The invention relates to an MOS tube overcurrent protection system. The system comprises a current sampling unit, a current effective value conversion unit, a comparison output unit and a control unit. The input end of the current effective value conversion unit is connected to the current sampling unit, the current effective value conversion unit comprises a plurality of linear conversion modules, and the current effective value conversion unit is used for conducting the corresponding linear conversion modules according to the magnitude interval of the load current and outputting a calculated value; a volt-ampere characteristic curve of a linear conversion module conducted according to the magnitude of the load current is fit with an actual electrical signal quadratic function curve; the input end of the comparison output unit is connected to the output end of the current effective value conversion unit, and the comparison output unit compares the calculated value with a first threshold value and sends out a first control signal when the calculated value is larger than the first threshold value; and the control unit is used for disconnecting the MOS tube after receiving the first control signal.

Description

technical field [0001] The invention relates to the field of overcurrent protection systems, in particular to a MOS tube overcurrent protection system. Background technique [0002] At present, the AC-AC AC voltage regulator with MOS tube as the actuator will distort the current waveform of the load due to the phase cut of the MOS tube switch. The thermal damage of MOS will be caused by transient impact current and steady-state current effective value. [0003] Some electronic dimmers use NTC or thermal fuse to detect the temperature of the MOS tube to limit the MOS load. This method is greatly affected by the ambient temperature and it is difficult to accurately limit the load current. For the MOS tube with capacitive load or short circuit, most of the protection of the instantaneous surge current adopts the logic AND of the output signal of the peak detection circuit and the driving signal of the MOS tube to close the MOS tube. When the fault persists, this protection met...

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Problems solved by technology

[0003] Some electronic dimmers use NTC or thermal fuse to detect the temperature of the MOS tube to limit the MOS load. This method is greatly affected by the ambient temperature and it is difficult to accurately limit the load current.

For the MOS tube with capacitive load or short circuit, most of the protection of the instantaneous inrush current uses the logic AND of the output signal of the peak detection circuit and the driving signal of the MOS tube to close the MOS tube. When the fault persists, this protection method will cause the MOS to fail. Repeated and rapid on-off in the state will increase the switching loss and further aggravate the heat generation of the MOS

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