Patent ID: 8971005
Filing Date: 2015-03-03
Classification: H02H

Abstract:
1. An over temperature protection circuit, comprising: a reference circuit for generating a reference voltage and a changeable voltage, wherein the changeable voltage is varied by temperature; and a hysteretic comparator for comparing the reference voltage and the changeable voltage to output a power down signal, wherein the hysteretic comparator further comprises: a switching unit connected to the bias current unit, wherein the switching unit including a first current path and a second current path, and the switching unit receives the reference voltage and the changeable voltage to arrange the constant current in the first current path and the second current path; a current sink unit connected to the switching unit, wherein the current sink unit sinks the current into the first current path and the second current path; and a signal output unit connected to the current sink unit to output the power down signal, wherein the reference circuit is a bandgap voltage reference circuit, further comprises: an operational amplifier; an eleventh transistor, a gate of the eleventh transistor being coupled to an output end of the first operational amplifier, a source of the eleventh transistor being coupled to a power supply, a drain of the eleventh transistor being coupled to a positive input end of the first operational amplifier; a twelfth transistor, a gate of the twelfth transistor being coupled to the output end of the first operational amplifier, a source of the twelfth transistor being coupled to the power supply, and a drain of the twelfth transistor being coupled to a negative input end of the first operational amplifier; a thirteenth transistor, a gate of the thirteenth transistor being coupled to the output end of the first operational amplifier, and a source of the thirteenth transistor being coupled to the power supply; a resistor, a first end of the first resistor being coupled to the positive input end of the first operational amplifier; a divider, a first end of the divider being coupled to a drain of the thirteenth transistor to generate the reference voltage; a first diode, a first end of the first diode being coupled to a second end of the resistor, and a second end of the first diode being coupled to a ground; a second diode, a first end of the second diode being coupled to the negative input end of the operational amplifier to generate the changeable voltage, a second end of the second diode being coupled to the ground; and a third diode, a first end of the third diode being coupled to the drain of the thirteenth transistor, a second end of the second diode being coupled to the ground.