Semiconductor circuit having an excess voltage protection circuit
First Claim
1. A semiconductor circuit comprising d.c. supply lines and an excess voltage protection circuit, wherein the protection circuit comprises;
- at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltage, a switching transistor connected in series with one of the supply lines, and a control circuit which is responsive to a voltage detector circuit coupled to the one supply line so as to trigger the switching transistor to a non-conductive state upon detection by the voltage detector of an excess voltage, wherein the voltage detector circuit comprises;
a semiconductor element having a voltage breakdown characteristic correlated with said one or more semiconductor elements and driven to breakdown in response to a voltage across the supply lines less than that which will cause breakdown of said one or more semiconductor elements, and wherein an increased current drawn at the onset of breakdown of the semiconductor element causes the control circuit to trigger the switching transistor to its non-conductive state.
1 Assignment
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Accused Products
Abstract
A semiconductor circuit has d.c. supply lines (10/13,11/14) and an excess voltage protection circuit. The protection circuit comprises a switching transistor (T1) connected in series with one of the supply lines (10/13) and a control circuit (15) which is responsive to a voltage detector circuit (16) coupled to the one supply line (10/13). The control circuit triggers the switching transistor to a non-conductive state upon detection of an excess voltage. The voltage detector circuit comprises a semiconductor element (T8) having a voltage breakdown characteristic correlated with one or more of the remaining semiconductor elements (T10). The semiconductor element (T8) is adapted to be driven to breakdown in response to a voltage across the supply lines less than that which will cause breakdown of the one or more remaining semiconductor elements T10. The increased current drawn by the semiconductor element (T8) at the onset of breakdown is effective to cause the control circuit to trigger the switching transistor to its non-conductive state.
11 Citations
22 Claims
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1. A semiconductor circuit comprising d.c. supply lines and an excess voltage protection circuit, wherein the protection circuit comprises;
- at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltage, a switching transistor connected in series with one of the supply lines, and a control circuit which is responsive to a voltage detector circuit coupled to the one supply line so as to trigger the switching transistor to a non-conductive state upon detection by the voltage detector of an excess voltage, wherein the voltage detector circuit comprises;
a semiconductor element having a voltage breakdown characteristic correlated with said one or more semiconductor elements and driven to breakdown in response to a voltage across the supply lines less than that which will cause breakdown of said one or more semiconductor elements, and wherein an increased current drawn at the onset of breakdown of the semiconductor element causes the control circuit to trigger the switching transistor to its non-conductive state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltage, a switching transistor connected in series with one of the supply lines, and a control circuit which is responsive to a voltage detector circuit coupled to the one supply line so as to trigger the switching transistor to a non-conductive state upon detection by the voltage detector of an excess voltage, wherein the voltage detector circuit comprises;
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16. A direct current power supply circuit comprising:
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a pair of input terminals for a source of alternating current, a voltage clamp and rectifier circuit coupled to said pair of input terminals, a semiconductor circuit having d.c. supply lines coupled to said voltage clamp and rectifier circuit and having an excess voltage protection circuit, said excess voltage protection circuit comprising;
at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltage,a switching transistor connected in series with one of the d.c. supply lines, and a control circuit responsive to a voltage detector circuit coupled to the one supply line so as to trigger the switching transistor into a non-conductive state upon detection of an excess voltage, wherein the voltage detector circuit comprises; a semiconductor element having a voltage breakdown characteristic correlated with said one or more semiconductor elements and driven to breakdown in response to a voltage across the supply lines less than that which will cause breakdown of said one or more semiconductor elements, and wherein an increased current drawn at the onset of breakdown of the semiconductor element causes the control circuit to trigger the switching transistor to its non-conductive state.
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17. A discharge lamp unit comprising:
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a switched mode power converter having an output coupled to a discharge tube and an input coupled to a direct current power supply circuit, and wherein said power supply circuit comprises; a pair of input terminals for a source of alternating current, a voltage clamp and rectifier circuit coupled to said pair of input terminals, a semiconductor circuit have d.c. supply lines coupled to said voltage clamp and rectifier circuit and having an excess voltage protection circuit, said excess voltage protection circuit comprising;
at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltage,a switching transistor connected in series with one of the d.c. supply lines, and a control circuit responsive to a voltage detector circuit coupled to the one supply line so as to trigger the switching transistor into a non-conductive state upon detection of an excess voltage, wherein the voltage detector circuit comprises; a semiconductor element having a voltage breakdown characteristic correlated with said one or more semiconductor elements and driven to breakdown in response to a voltage across the supply lines less than that which will cause breakdown of said one or more semiconductor elements, and wherein an increased current drawn at the onset of breakdown of the semiconductor element causes the control circuit to trigger the switching transistor to its non-conductive state. - View Dependent Claims (18, 19)
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20. A semiconductor circuit providing protection against excess voltages and comprising:
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first and second input terminals for a source of supply voltage for the semiconductor circuit, at least one load terminal for connection to a load including one or more semiconductor elements to be protected against said excess voltages, a supply line including a switching transistor connected between the first input terminal and said one load terminal, a control circuit coupled to a control electrode of the switching transistor to trigger the switching transistor into cut-off upon detection of the excess voltage, a voltage detector circuit coupled to said supply line and responsive to a voltage thereat to trigger the switching transistor into cut-off via the control circuit upon detection by the voltage detector circuit of an excess voltage at said supply line, said voltage detector circuit comprising a semiconductor element having a voltage breakdown characteristic correlated with the breakdown characteristics of said one or more semiconductor elements and adapted to be driven into breakdown in response to a voltage at the supply line which is less than a voltage which will cause breakdown of said one or more semiconductor elements, and wherein an increased current drawn at the onset of breakdown of the semiconductor element causes the control circuit to trigger the switching transistor to its cut-off state. - View Dependent Claims (21, 22)
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Specification