Thermal shutoff circuit
AssigneeKabushiki Kaisha Toshiba
InventorsHiroyuki Haga, Mitsuru Nagata, Hiromi Kusakabe
Life of this patent
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Abstract
A thermal shutoff circuit for controlling current to an external circuit in response to changes in the temperature of the shutoff circuit. The thermal shutoff circuit includes a source for supplying a voltage which varies with changes in temperature, and a switch circuit responsive to the temperature variable voltage for interrupting the current to the external circuit when the temperature of the shutoff circuit exceeds a predetermined amount. The switch circuit has a detection transistor having a base connected to the temperature variable voltage source for generating a base current responsive to the temperature variable voltage and a compensation transistor connected in series to the detection transistor for generating an equivalent base current.
Claims15
A thermal shutoff circuit for controlling current to an external circuit in response to changes in the temperature of the shutoff circuit, comprising:
- means for supplying a voltage which varies with changes in temperature;
- and
- switch means, responsive to the temperature variable voltage, for interrupting the current to the external circuit when the temperature of the shutoff circuit exceeds a predetermined amount, said switch means including
- transistor means for compensating for variations in the current amplification ratios of other transistors in said thermal shutoff circuit, said transistor means including
- a detection transistor having a base current responsive to the temperature variable voltage, and
- a compensation transistor connected in series to the detection transistor for generating an equivalent base current to the base current of the detection transistor.
Dependencies are inferred from the claim text.