Protection device and control circuit for a semiconductor switch and method for controlling a semiconductor switch
The invention relates to a protection for a semi-conductor switch against over voltages. A capacitive element is provided on an inlet connection of the semi-conductor switch. The load amount, which flows into said capacitive element, is integrated in order to trigger a protection function when a threshold value is exceeded.
1. A protection device ( 1 ) for a semiconductor switch ( 3 ) comprising:
a capacitive component ( 11 , 11 a , 11 b );
an integrator ( 12 , 12 b ) configured to integrate a charging current into the capacitive component ( 11 , 11 a , 11 b ) in order to determine a quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) from the integrated charging current;
a comparison device ( 13 ) configured to control the semiconductor switch ( 3 ) when the determined quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) exceeds a preset limit value (S); and
a logic gate ( 14 ) for linking the result of the comparison device ( 13 ) and a control signal (D),
wherein the capacitive component ( 11 , 11 a , 11 b ) is arranged between an input terminal ( 31 ) of the semiconductor switch ( 3 ) and the integrator ( 12 , 12 b ), and
wherein the integrator ( 12 , 12 b ) is configured to synchronize the integration of the charging current with the control signal (D) for the semiconductor switch ( 3 ).
2. The protection device ( 1 ) as claimed in claim 1 , wherein the capacitive component ( 11 , 11 a , 11 b ) comprises an avalanche diode.
3. The protection device ( 1 ) as claimed in claim 2 , wherein the preset limit value (S) is set using a junction capacitance of the avalanche diode ( 11 a ).
4. The protection device ( 1 ) as claimed in claim 2 , wherein the comparison device ( 13 ) is configured to control the semiconductor switch ( 3 ) when an electrical voltage across the diode ( 11 a ) exceeds a breakdown voltage of the avalanche diode ( 11 a ).
5. The protection device ( 1 ) as claimed in claim 1 , wherein the capacitive component ( 11 , 11 a , 11 b ) comprises a capacitor ( 11 b ).
6. The protection device ( 1 ) as claimed in claim 1 , wherein the integrator ( 12 , 12 b ) is designed to start the integration of the charging current when the semiconductor switch ( 13 ) is opened.
7. The protection device ( 1 ) as claimed in claim 1 , wherein the integrator ( 12 b ) comprises a capacitor.
8. A control circuit ( 2 ) for a semiconductor switch ( 3 ) comprising:
a driver circuit ( 20 ) configured to receive the control signal (D) for the semiconductor switch ( 3 ) and to control a gate ( 32 ) of the semiconductor switch ( 3 ) using the received control signal (D); and
a protection device ( 1 ) as claimed in claim 1 ,
wherein the driver circuit ( 20 ) is electrically coupled to the protection device ( 1 ), and the driver circuit ( 20 ) is configured to control the semiconductor switch ( 3 ) at least partially when the quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) determined by the protection device ( 1 ) exceeds the preset limit value (S).
9. The protection device ( 1 ) as claimed in claim 1 , wherein the capacitive component ( 11 , 11 a , 11 b ) comprises a zener diode.
10. A method for controlling a semiconductor switch ( 3 ) comprising:
integrating (S 1 ) a charging current into a capacitive component ( 11 , 11 a , 11 b ) to determine a quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) from the integrated charging current, wherein the capacitive component is arranged between an input terminal ( 31 ) of the semiconductor switch ( 3 ) and an integrator ( 12 , 12 b );
comparing (S 2 ) the determined quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) with a preset limit value (S);
controlling (S 3 ) the semiconductor switch ( 3 ) when the determined quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) exceeds the preset limit value (S);
linking the result of a comparison device ( 13 ) and a control signal (D) with a logic gate ( 14 ); and
synchronizing the integration of the charging current with the control signal (D) for the semiconductor switch ( 3 ).
11. The method as claimed in claim 10 , wherein the integration (S 1 ) of the charging current is started when the semiconductor switch ( 3 ) is opened.
12. The method as claimed in claim 10 , wherein the capacitive component ( 11 , 11 a , 11 b ) is arranged between an input terminal ( 31 ) of the semiconductor switch ( 3 ) and the integrator ( 12 , 12 b ).
13. The method as claimed in claim 12 , wherein the capacitive component ( 11 , 11 a , 11 b ) includes an avalanche diode.
14. The method as claimed in claim 12 , wherein the capacitive component ( 11 , 11 a , 11 b ) includes a zener diode.
15. A control circuit ( 2 ) for a semiconductor switch ( 3 ) comprising:
a capacitive component ( 11 , 11 a , 11 b );
an integrator ( 12 , 12 b ) configured to integrate a charging current into the capacitive component ( 11 , 11 a , 11 b ) in order to determine a quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) from the integrated charging current;
a comparison device ( 13 ) configured to control the semiconductor switch ( 3 ) when the determined quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) exceeds a preset limit value (S);
a logic gate ( 14 ) for linking the result of the comparison device ( 13 ) and a control signal (D); and
a driver circuit ( 20 ) configured to receive the control signal (D) for the semiconductor switch ( 3 ) and to control a gate ( 32 ) of the semiconductor switch ( 3 ) using the received control signal (D);
wherein the driver circuit ( 20 ) is electrically coupled to a protection device ( 1 ), and the driver circuit ( 20 ) is configured to control the semiconductor switch ( 3 ) at least partially when the quantity of charge (Q) in the capacitive component ( 11 , 11 a , 11 b ) determined by the protection device ( 1 ) exceeds the preset limit value (S), and
wherein the capacitive component ( 11 , 11 a , 11 b ) is arranged between an input terminal ( 31 ) of the semiconductor switch ( 3 ) and the integrator ( 12 , 12 b ).
16. The control circuit ( 2 ) according to claim 15 , wherein the capacitive component ( 11 , 11 a , 11 b ) includes either an avalanche diode or a Zener diode, and control of the semiconductor switch also takes place when the avalanche diode or the Zener diode transfers to an on state once a breakdown voltage has been exceeded.
17. The control circuit ( 2 ) according to claim 15 , wherein the integrator ( 12 , 12 b ) is configured to synchronize the integration of the charging current with the control signal (D) for the semiconductor switch ( 3 ).