Protection circuit for power switch

1 . A circuit comprising:

a first voltage input, a second voltage input, and a voltage output;

a transistor coupled between the first voltage input and the voltage output, the transistor having a control terminal;

first circuitry coupled between the second voltage input and the voltage output, the first circuitry having an output coupled to the control terminal of the transistor;

second circuitry coupled between the control terminal of the transistor and a ground terminal, the second circuitry separate from the first circuitry; and

third circuitry coupled between the control terminal of the transistor and the voltage output, the third circuitry separate from the first circuitry and the second circuitry.

2 . The circuit of claim 1 , wherein the third circuitry includes a control terminal coupled to the voltage output, the circuit further comprising:

a first control signal input coupled to a control terminal of the first circuitry; and

a second control signal input coupled to a control terminal of the second circuitry.

3 . The circuit of claim 1 , wherein the transistor is a first transistor, the second circuitry including:

a second transistor coupled between the control terminal of the first transistor and the ground terminal;

a first unidirectional current device coupled between the control terminal of the first transistor and a terminal of the second transistor; and

a second unidirectional current device coupled between the control terminal of the first transistor and the terminal of the second transistor.

4 . The circuit of claim 3 , the third circuitry including:

a third transistor coupled between the control terminal of the first transistor and the voltage output;

a third unidirectional current device coupled between the voltage output and the ground terminal; and

a fourth unidirectional current device coupled between a terminal of the third unidirectional current device and the ground terminal, wherein a control terminal of the third transistor is coupled between the terminal of the third unidirectional current device and a terminal of the fourth unidirectional current device.

5 . The circuit of claim 4 , further comprising:

a first control signal input coupled to a control terminal of the second transistor.

6 . The circuit of claim 1 , wherein the transistor is a first transistor, the circuit further comprising:

a third voltage input;

a second transistor coupled between the first voltage input and the voltage output;

fourth circuitry coupled between the third voltage input and the voltage output, the fourth circuitry having an output coupled to a control terminal of the second transistor;

fifth circuitry coupled between the control terminal of the second transistor and ground; and

sixth circuitry coupled between the control terminal of the second transistor and the voltage output.

7 . The circuit of claim 1 , wherein the first circuitry has a control input and is configurable to provide a first current path between the second voltage input and the control terminal of the transistor responsive to the control input having a first state and provide a second current path between the control terminal of the transistor and the voltage output responsive to the control input having a second state.

8 . The circuit of claim 1 , wherein the second circuitry is configurable to enable a first current path from the control terminal to the ground terminal responsive to a voltage at the control terminal being non-negative; and the third circuitry is configurable to enable a second current path from the control terminal to the voltage output responsive to the voltage at the control terminal being negative.

9 . A circuit comprising:

a first voltage input, a second voltage input, a first control signal input, a second control signal input, and a voltage output;

a first transistor coupled between the first voltage input and the voltage output;

a second transistor including a first terminal coupled to second voltage input, a second terminal coupled to a control terminal of the first transistor, and a control terminal coupled to the first control signal input;

a third transistor including a first terminal coupled to the control terminal of the first transistor, a second terminal coupled to the voltage output, and a control terminal coupled to the first control signal input;

a fourth transistor coupled between the control terminal of the first transistor and a ground terminal, the fourth transistor including a control terminal coupled to the second control signal input;

a fifth transistor coupled between the control terminal of the first transistor and the first terminal of the fourth transistor;

a sixth transistor coupled between the control terminal of the first transistor and the first terminal of the fourth transistor;

a seventh transistor coupled between the control terminal of the first transistor and the voltage output;

an eighth transistor coupled between the ground terminal and the voltage output, the eighth transistor including a control terminal coupled to a control terminal of the seventh transistor; and

a nineth transistor coupled between the ground terminal and the first terminal of the eighth transistor.

10 . The circuit of claim 9 , wherein the fifth transistor and the sixth transistor are diode-connected transistors configurable to allow unidirectional current flow from the control terminal of the first transistor to the ground terminal, and wherein the eighth transistor and the nineth transistor are diode-connected transistor configurable to allow unidirectional current flow from the ground terminal to the voltage output.

11 . The circuit of claim 9 , wherein the control terminal of the fifth transistor is coupled to the first terminal of the fifth transistor, the control terminal of the sixth transistor is coupled to the first terminal of the sixth transistor, the control terminal of the eighth transistor is coupled to the first terminal of the eighth transistor, and the control terminal of the nineth transistor is coupled to the second terminal of the nineth transistor.

12 . The circuit of claim 9 , further comprising:

a first resistor coupled between the control terminal of the first transistor and the first terminal of the sixth transistor; and

a second resistor coupled between the first terminal of the eighth transistor and the first terminal of the nineth transistor.

13 . The circuit of claim 9 , further comprising:

a third voltage input; and

a tenth transistor coupled between the first voltage input and the voltage output.

14 . The circuit of claim 13 , further comprising:

an eleventh transistor coupled between a control terminal of the tenth transistor and the ground terminal;

a twelfth transistor coupled between the control terminal of the tenth transistor and the first terminal of the eleventh transistor;

a thirteenth transistor coupled between the control terminal of the tenth transistor and the first terminal of the eleventh transistor;

a fourteenth transistor coupled between the control terminal of the tenth transistor and the voltage output;

a fifteenth transistor coupled between the ground terminal and the voltage output; and

a sixteenth transistor coupled between the first terminal of the fifteenth transistor and the ground terminal.

15 . The circuit of claim 14 , further comprising:

a third control signal input;

a seventeenth transistor including a first terminal coupled to the second voltage input, a second terminal coupled to the control terminal of the tenth transistor, and a control terminal coupled to the third control signal input; and

an eighteenth transistor including a first terminal coupled to the control terminal of the tenth transistor, a second terminal coupled to the voltage output, and a control terminal coupled to the third control signal input.

16 . The circuit of claim 14 , wherein the first transistor has a first number of channels, the tenth transistor has a second number of channels, and the second number is greater than the first number.

17 . A system comprising:

a controller including a first output and a second output;

a voltage source;

a voltage converter including an input and an output, the input of the voltage converter coupled to the voltage source;

load circuitry including an input; and

switching circuitry coupled to the controller, the voltage source, the voltage converter, and the load circuitry, the switching circuitry including:

a first voltage input coupled to the voltage source;

a second voltage input coupled to the output of the voltage converter;

a voltage output coupled to the input of the load circuitry;

a first control signal input coupled to the first output of the controller;

a second control signal input coupled to the second output of the controller;

a first transistor coupled between the first voltage input and the voltage output in a first current path, the first current path including the first voltage input, a first terminal of the first transistor, a second terminal of the first transistor, and the voltage output;

transistor control circuitry coupled between the second voltage input and the voltage output, the transistor control circuitry having a control input and a control output, the control input coupled to the first control signal input, and the control output coupled to a control terminal of the first transistor;

first protection circuitry coupled between the control terminal of the first transistor and a ground terminal, the first protection circuitry separate from the transistor control circuitry, the first protection circuitry having an input coupled to the second control signal input, the first protection circuitry configurable to, responsive to a state of the second control signal input and a voltage at the control terminal being non-negative, enable a first current path from the control terminal of the first transistor to the ground terminal; and

second protection circuitry coupled between the control terminal of the first transistor and the voltage output, the second protection circuitry separate from the first protection circuitry and the transistor control circuitry and configurable to provide a second current path from the control terminal of the first transistor to the voltage output.

18 . The system of claim 17 , the first protection circuitry including:

a second transistor coupled between the control terminal of the first transistor and the ground terminal, the second transistor including a control terminal coupled to second control signal input;

a first unidirectional current device coupled between the control terminal of the first transistor and the first terminal of the second transistor; and

a second unidirectional current device coupled between the control terminal of the first transistor and the first terminal of the second transistor.

19 . The system of claim 18 , the second protection circuitry including:

a third transistor coupled between the control terminal of the first transistor and the voltage output;

a third unidirectional current device coupled between ground and the voltage output; and

a fourth unidirectional current device coupled between the ground terminal and the first terminal of the third unidirectional current device, wherein a control terminal of the third transistor is coupled between the first terminal of the third unidirectional current device and the first terminal of the fourth unidirectional current device.

20 . The system of claim 17 , further comprising:

a second transistor coupled between the first voltage input and the voltage output;

third protection circuitry coupled between a control terminal of the second transistor and the ground terminal, the third protection circuitry including a control terminal coupled to the second control signal input, the third protection circuitry configurable to, responsive to a state of the second control signal input and a voltage at the control terminal of the second transistor being non-negative, enable a third current path from the control terminal of the second transistor to the ground terminal; and

fourth protection circuitry coupled between the control terminal of the second transistor and the voltage output, the fourth protection circuitry configurable to enable a second current path from the control terminal of the second transistor to the voltage output responsive to a voltage at the control terminal of the second transistor being negative.

21 . The system of claim 17 , wherein the voltage source is a battery, the voltage converter is a charge pump, and the controller is a microcontroller.