Bi-directional feedback pin

1. A controller for a power conversion circuit, comprising:

a first current-reading circuit including an input connected to a first circuit node for receiving a first feedback signal into the first circuit node and generating an internal feedback signal from an output at a second circuit node inversely proportional to the first feedback signal; and

a second current-reading circuit including an input connected to the first circuit node for enabling a second feedback signal to be drawn from the first circuit node and generating the internal feedback signal from an output at the second circuit node inversely proportional to the second feedback signal, wherein the input of the first current-reading circuit and the input of the second current-reading circuit are both connected to the first circuit node, and the output of the first current-reading circuit and the output of the second current-reading circuit are both connected to the second circuit node.

2. The controller of claim 1 , wherein the first current-reading circuit is configured to generate the internal feedback signal inversely proportional to a first electric current injected into the controller at the first circuit node.

3. The controller of claim 2 , wherein the second current-reading circuit is configured to generate the internal feedback signal inversely proportional to a second electric current drawn from the controller at the first circuit node.

4. The controller of claim 1 , further including a drive output of the controller configured to be controlled by the internal feedback signal.

5. The controller of claim 1 , wherein the first current-reading circuit includes a first current mirror coupled between the first circuit node and second circuit node.

6. The controller of claim 1 , further including:

a clamp circuit coupled between the first circuit node and first current-reading circuit; and

a diode coupled between the first circuit node and second current-reading circuit.

7. A controller for a power conversion circuit, comprising:

a first current-reading circuit coupled to a first circuit node for receiving a first feedback signal into the first circuit node and generating an internal feedback signal at a second circuit node inversely proportional to the first feedback signal, wherein the first current-reading circuit includes a first current mirror coupled between the first circuit node and second circuit node; and

a second current-reading circuit coupled to the first circuit node for enabling a second feedback signal to be drawn from the first circuit node and generating the internal feedback signal at the second circuit node inversely proportional to the second feedback signal, wherein the second current-reading circuit includes:

(a) a second current mirror having an input coupled to the first circuit node, and

(b) a third current mirror having an input coupled to an output of the second current mirror and an output coupled to the second circuit node.

8. A controller for a power conversion circuit, comprising:

a first current mirror including an input coupled to a terminal of the controller and an output of the first current mirror coupled to a feedback circuit node;

a second current mirror including an input coupled to the terminal of the controller; and

a third current mirror including an input coupled to an output of the second current mirror and an output of the third current mirror coupled to the feedback circuit node.

9. The controller of claim 8 , further including a clamp circuit coupled between the terminal of the controller and the input of the first current mirror.

10. The controller of claim 9 , wherein the clamp circuit includes a Zener diode.

11. The controller of claim 8 , further including a diode coupled between the terminal of the controller and the input of the second current mirror.

12. The controller of claim 8 , further including a resistor coupled between a voltage input terminal of the controller and the feedback circuit node.

13. The controller of claim 8 , wherein the first current mirror includes:

a first transistor comprising a first conduction terminal coupled to the terminal of the controller, a control terminal coupled to the terminal of the controller, and a second conduction terminal coupled to a power supply terminal; and

a second transistor comprising a first conduction terminal coupled to the feedback circuit node, a control terminal coupled to the terminal of the controller, and a second conduction terminal coupled to the power supply terminal.

14. The controller of claim 8 , wherein the second current mirror includes,

(a) a first transistor comprising a first conduction terminal coupled to a first power supply terminal of the controller, a second conduction terminal coupled to the terminal of the controller, and a control terminal coupled to the terminal of the controller, and

(b) a second transistor comprising a first conduction terminal coupled to the first power supply terminal of the controller, and a control terminal coupled to the terminal of the controller,

and the third current mirror includes,

(c) a third transistor comprising a first conduction terminal coupled to a second conduction terminal of the second transistor, a control terminal coupled to the second conduction terminal of the second transistor, and a second conduction terminal coupled to a second power supply terminal of the controller, and

(b) a fourth transistor comprising a first conduction terminal coupled to the second power supply terminal of the controller, a control terminal coupled to the second conduction terminal of the second transistor, and a second conduction terminal coupled to the feedback circuit node.

15. A method of generating a voltage signal, comprising:

providing a controller including a feedback terminal and a feedback circuit node;

forming a first current-reading circuit coupled between the feedback terminal and the feedback circuit node adapted for receiving a first feedback signal into the feedback terminal to generate an internal feedback signal at the feedback circuit node; and

forming a second current-reading circuit coupled between the feedback terminal and the feedback circuit node, wherein the first current-reading circuit includes an input connected to the feedback terminal and an output connected to the feedback circuit node, and the second current-reading circuit includes an input connected to the feedback terminal and an output connected to the feedback circuit node, and the second current-reading circuit is adapted for enabling a second feedback signal to be drawn from the feedback terminal to generate the internal feedback signal at the feedback circuit node.

16. The method of claim 15 , further including disposing a phototransistor adjacent to the controller and coupled to the feedback terminal of the controller.

17. The method of claim 15 , further including disposing a transformer comprising an auxiliary winding adjacent to the controller with the auxiliary winding coupled to the feedback terminal of the controller.

18. The method of claim 15 , further including providing a resistor coupled to the feedback circuit node.

19. The method of claim 18 , further including:

drawing electric current through the resistor using the first current-reading circuit when electric current is injected into the feedback terminal; and

drawing electric current through the resistor using the second current-reading circuit when electric current is drawn from the feedback terminal.

20. The method of claim 15 , further including:

providing a Zener diode coupled between the feedback terminal and first current mirror; and

providing a diode coupled between the feedback terminal and second current mirror.