Adaptive bipolar junction transistor gain detection

摘要

A power converter that controls a collector current of a bipolar junction transistor (BJT) by controlling the base current to the BJT after having determined the gain of the BJT. A gain detection block determines a gain of the BJT during a first mode. A current calculation block generates a current setting for the base current based on the gain of the BJT determined by the gain detection block during a second mode distinct from the first mode. In some embodiments, the power converter may be included in a LED lamp system.

主权项

1. A power converter comprising:
a magnetic component coupled to an input voltage and to an output of the power converter, a shape of the input voltage having a phase cutoff portion adjustable by a dimmer switch; a bipolar junction transistor (BJT) coupled to the magnetic component; a current control circuit configured to generate a control signal for controlling a base current of the BJT; a gain detection circuit configured to, during a first mode, generate a first current setting signal for setting the base current of the BJT to a first base current level and to determine a current gain of the BJT in a forward-active region based on a feedback signal indicative of a level of current flowing through the BJT and the first base current level, the control signal generated responsive to the first current setting signal in the first mode; and a current calculation circuit configured to, during a second mode distinct in time from the first mode, generate a second current setting signal for setting the base current of the BJT to a second base current level that operates the BJT in the forward-active region during the phase cutoff portion of the shape of the input voltage, the current calculation circuit determining the second base current level responsive to a target current level and the determined current gain of the BJT, the BJT drawing current from the dimmer switch when operated in the forward-active region during the second mode, the control signal generated responsive to the second current setting signal in the second mode, the current control circuit generating the control signal to switch the BJT between a saturation region and a cutoff region during a third mode distinct in time from the first mode and the second mode, the third mode substantially corresponding to a portion of the input voltage that is not cutoff by the dimmer switch.