Over-voltage protection circuit for use in USB Type-C port and related method
An over-voltage protection circuit includes an over-voltage detection circuit, a voltage generator and a switch for providing over-voltage protection between two pins of a USB Type-C port. The over-voltage detection circuit provides an over-voltage signal according to the level of the second pin. The switch includes a first end coupled to the first pin, a second end coupled to the second pin and a control end coupled to a control signal. When the over-voltage signal does not indicate an over-voltage occurrence at the second pin, the voltage generator provides the control signal having a first level for operating the switch in a first region. When the over-voltage signal indicates an over-voltage occurrence at the second pin, the voltage generator adjusts the control signal to a second level for cutting off the switch. The switch operates in a second region after the over-voltage occurrence and before the switch is cut off.
1. An over-voltage protection circuit for use in a USB Type-C port, comprising:
a first node coupled to a supply voltage;
a second node coupled to a first pin or a second pin of the USB Type-C port;
an over-voltage detection circuit configured to provides an over-voltage signal according to a voltage level of the second node;
a switch including:
a first end coupled to the first node;
a second end coupled to the second node; and
a control end coupled to a switch control signal; and
a voltage generator configured to provide the switch control signal and adjust a level of the switch control signal according to the over-voltage signal, wherein:
when the over-voltage signal does not indicate that an over-voltage occurs at the second node, the voltage generator is configured to provide the switch control signal having a first level for operating the switch in a first region;
when the over-voltage signal indicates that the over-voltage occurs at the second node, the voltage generator is configured to adjust the switch control signal from the first level to a second level for cutting off the switch;
the switch is configured to operate in a second region during a period after the switch control signal is adjusted from the first level to the second level and before the switch is cut off;
a first conducting current flows from the first end of the switch to the second end of the switch when the switch operates in the first region;
a second conducting current flows from the second end of the switch to the first end of the switch when the switch operates in the second region;
a value of the first conducting current is proportional to a voltage difference between the control end of the switch and the second end of the switch; and
a value of the second conducting current is proportional to a square of the voltage difference between the control end of the switch and the second end of the switch.
2. The over-voltage protection circuit of claim 1 , wherein:
the first pin is a first configuration channel pin(CC 1 ) of the USB Type-C port; and
the second pin is a second configuration channel pin(CC 2 ) of the USB Type-C port.
3. The over-voltage protection circuit of claim 1 , wherein:
the switch is an N-type metal oxide semiconductor field effect transistor (NMOSEFT);
the first end of the switch is a drain terminal;
the second end of the switch is a source terminal; and
the control end of the switch is a gate terminal.
4. The over-voltage protection circuit of claim 3 , wherein:
the first region is a linear region;
a first conducting current flows from the first end of the switch to the second end of the switch when the switch operates in the linear region;
a value of the first conducting current is proportional to 2(VGS−Vth)VDS−VDS 2 ;
VGS represents a gate-source voltage of the switch;
VDS represents a drain-source voltage of the switch; and
Vth represents a threshold voltage of the switch.
5. The over-voltage protection circuit of claim 3 , wherein:
the second region is a saturation region;
the second conducting current flows from the second end of the switch to the first end of the switch when the switch operates in the saturation region;
a value of the second conducting current is proportional to (VGS−Vth) 2 ;
VGS represents a gate-source voltage of the switch; and
Vth represents a threshold voltage of the switch.
6. The over-voltage protection circuit of claim 3 , wherein:
when the control end of the switch receives the switch control signal having the first level and the over-voltage signal does not indicate that the over-voltage occurs at the second node, VDS<VGS−Vth;
VGS represents a gate-source voltage of the switch;
VDS represents a drain-source voltage of the switch; and
Vth represents a threshold voltage of the switch.
7. The over-voltage protection circuit of claim 3 , wherein:
when the control end of the switch receives the switch control signal having the first level and the over-voltage signal indicates that the over-voltage occurs at the second node, VDS>VGS−Vth;
VGS represents a gate-source voltage of the switch;
VDS represents a drain-source voltage of the switch; and
Vth represents a threshold voltage of the switch.
8. The over-voltage protection circuit of claim 3 , wherein the voltage generator is a charge pump.
9. The over-voltage protection circuit of claim 1 , wherein a value of the first level is determined based on a device characteristic of the switch, a load current of the second node, and a maximum voltage of the second node after the over-voltage occurs and before the switch is turned off.
10. A method of providing over-voltage protection in a USB Type-C port, comprising:
providing a supply voltage to a first node;
coupling a first pin or a second pin of the USB Type-C port to a second node;
a switch selectively conducting or cutting off a signal transmission path between the first node and the second node;
detecting a voltage level of the second node and providing a corresponding over-voltage signal;
providing the switch control signal having a first level for turning on the switch when the over-voltage signal does not indicate that an over-voltage occurs at the second node, so that the switch operates in a first region when no over-voltage occurs at the second node and operates in a second region during a period after the over-voltage occurs at the second node and before the switch is cut off; and
adjusting the switch control signal from the first level to a second level for cutting off the switch when the over-voltage signal indicates that the over-voltage occurs at the second node, wherein:
the switch includes a first end coupled to the first node, a second end coupled to the second node, and a control end coupled to the switch control signal;
a first conducting current flows from the first end of the switch to the second end of the switch when the switch operates in the first region;
a second conducting current flows from the second end of the switch to the first end of the switch when the switch operates in the second region;
a value of the first conducting current is proportional to a voltage difference between the control end of the switch and the second end of the switch; and
a value of the second conducting current is proportional to a square of the voltage difference between the control end of the switch and the second end of the switch.
11. The method of claim 10 , wherein:
the first pin is a first configuration channel pin(CC 1 ) of the USB Type-C port; and
the second pin is a second configuration channel pin(CC 2 ) of the USB Type-C port.
12. The method of claim 10 , wherein:
the switch is an N-type metal oxide semiconductor field effect transistor (NMOSEFT);
the first region is a linear region; and
the second region is a saturation region.
13. The method of claim 10 , further comprising:
determining a value of the first level based on a device characteristic of the switch, a load current of the second node, and a maximum voltage of the second node after the over-voltage occurs and before the switch is turned off.