Dynamic control of power switching bipolar junction transistor

1. A switching power converter comprising:

a magnetic component coupled to an input voltage and to an output of the switching power converter;

a bipolar junction transistor (BJT) switch coupled to the magnetic component, current through the magnetic component being generated while the BJT switch is operating in a saturation mode and not being generated while the BJT switch is operating in a cutoff mode; and

a controller configured to generate a control signal to operate the BJT switch in the saturation mode, the cutoff mode, or an active mode;

wherein the switching power converter operates in a switching mode responsive to the BJT switch continuously switching operation between the saturation mode and the cutoff mode, the switching power converter delivering power to the output of the switching power converter during the switching mode;

wherein the switching power converter operates in a linear mode responsive to the BJT switch operating in the active mode, wherein the BJT switch is configured to draw current from a dimmer switch coupled to the switching power converter during the linear mode.

2. The switching power converter of claim 1 , wherein input capacitors between the switching power converter and the dimmer switch are discharged via the BJT switch during the linear mode.

3. The switching power converter of claim 1 , wherein the switching power converter is incorporated into a light emitting diode lamp.

4. The switching power converter of claim 1 , further comprising:

a switching mode driver configured to generate a first range of current magnitude that drives a base terminal of the BJT switch responsive to receiving the control signal from the controller, the first range of current magnitude causing the BJT switch to operate in the saturation mode; and

a linear mode driver configured to generate a second range of current magnitude that drives the base terminal of the BJT switch responsive to receiving the control signal from the controller, the second range of current magnitude causing the BJT switch to operate in the active mode.

5. The switching power converter of claim 4 , wherein a lower end of the first range of current magnitude is greater than at least a lower end of the second range of current magnitude, and a higher end of the first range of current magnitude is greater than at least a higher end of the second range of current magnitude.

6. The switching power converter of claim 4 , wherein the switching mode driver is further configured to increase the current delivered to the base terminal of the BJT switch from a first current magnitude to a second current magnitude during the switching mode to keep the BJT switch in the saturation mode and wherein the linear mode driver is further configured to maintain the current delivered to the base terminal of the BJT switch at a third current magnitude to keep the BJT switch in the active mode.

7. The switching power converter of claim 6 , wherein the linear mode driver is further configured to increase the current delivered to the base terminal of the BJT switch from the third current magnitude to a fourth current magnitude during the linear mode to determine a current magnitude to deliver to the base terminal of the BJT switch during the linear mode in a next AC cycle to keep the BJT switch in the active mode.

8. The switching power converter of claim 7 , wherein a current step size from the first current magnitude to the second current magnitude during the switching mode is larger than the a current step size from the third current magnitude to the fourth current magnitude during the linear mode.

9. In a controller, a method of controlling a switching power converter, the switching power converter including a magnetic component coupled to an input voltage and to an output of the switching power converter and a bipolar junction transistor (BJT) switch coupled to the magnetic component, current through the magnetic component being generated while the BJT switch is operating in a saturation mode and not being generated while the BJT switch is operating in a cutoff mode, the method comprising:

generating a control signal to operate the BJT switch in the saturation mode, the cutoff mode, or an active mode;

operating the switching power converter in a switching mode with the BJT switch continuously switching operation between the saturation mode and the cutoff mode, the switching power converter delivering power to the output of the switching power converter during the switching mode; and

operating the switching power converter in a linear mode with the BJT switch operating in the active mode;

wherein the BJT switch is configured to draw current from a dimmer switch coupled to the switching power converter during the linear mode.

10. The method of claim 9 , wherein input capacitors between the switching power converter and the dimmer switch are discharged via the BJT switch during the linear mode.

11. The method of claim 9 , wherein the control signal controls a switching mode driver to generate a first range of current magnitude that drives a base terminal of the BJT switch to operate the BJT switch in the saturation mode responsive to the switching mode driver receiving the control signal and wherein the control signal controls a linear mode driver to generate a second range of current magnitude that drives the base terminal of the BJT switch to operate the BJT switch in the active mode responsive to the linear mode driver receiving the control signal.

12. The method of claim 11 , wherein a lower end of the first range of current magnitude is greater than at least a lower end of the second range of current magnitude, and a higher end of the first range of current magnitude is greater than at least a higher end of the second range of current magnitude.

13. The method of claim 11 , wherein the control signal controls the switching mode driver to increase the current delivered to the base terminal of the BJT switch from a first current magnitude to a second current magnitude during the switching mode to keep the BJT switch in the saturation mode and wherein the control signal controls the linear mode driver to maintain the current delivered to the base terminal of the BJT switch at a third current magnitude to keep the BJT switch in the active mode.

14. The method of claim 13 , wherein the control signal further controls the linear mode driver to increase the current delivered to the base terminal of the BJT switch from the third current magnitude to a fourth magnitude during the linear mode to determine a current magnitude to deliver to the base terminal of the BJT switch during the linear mode in a next AC cycle to keep the BJT switch in the active mode.

15. The method of claim 14 , wherein a current step size from the first current magnitude to the second current magnitude during the switching mode is larger than a current step size from the third current magnitude to the fourth current magnitude during the linear mode.