Two terminal drive of bipolar junction transistor (BJT) of a light emitting diode (LED)-based bulb
First Claim
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1. A method comprising:
- driving a base current from a base current source to a base of a bipolar junction transistor (BJT) to maintain conduction of the bipolar junction transistor (BJT) during a first time period;
disconnecting the base current source from the bipolar junction transistor (BJT) during a second time period;
receiving a current measurement from a current detect circuit coupled to an emitter of the bipolar junction transistor (BJT);
repeating the steps of driving the base current during the first time period and disconnecting the base current source for the second time period to obtain an average current output to a load; and
dynamically adjusting the base current output from the base current source to adjust a reverse recovery time period of the bipolar junction transistor (BJT) based, at least in part, on the received current measurement.
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Abstract
A bipolar junction transistor (BJT) may be used in a power stage DC-to-DC converter, such as for LED-based light bulbs. The BJT may be switched on and off from a controller coupled to two terminals of the BJT. Through the two terminals, the control IC may dynamically adjust a reverse recovery time period of the BJT. The reverse recovery time period may be adjusted by changing an amount of base charge that accumulates on the BJT. Additional, the reverse recovery may be controlled through the use of a reverse base current source applied to the BJT after beginning switching off the BJT.
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Citations
28 Claims
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1. A method comprising:
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driving a base current from a base current source to a base of a bipolar junction transistor (BJT) to maintain conduction of the bipolar junction transistor (BJT) during a first time period; disconnecting the base current source from the bipolar junction transistor (BJT) during a second time period; receiving a current measurement from a current detect circuit coupled to an emitter of the bipolar junction transistor (BJT); repeating the steps of driving the base current during the first time period and disconnecting the base current source for the second time period to obtain an average current output to a load; and dynamically adjusting the base current output from the base current source to adjust a reverse recovery time period of the bipolar junction transistor (BJT) based, at least in part, on the received current measurement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus, comprising:
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a controller configured to couple to a base and to an emitter of a bipolar junction transistor (BJT), wherein the controller is configured to perform the steps comprising; driving a base current from a base current source to the base of the bipolar junction transistor (BJT) to maintain conduction of the bipolar junction transistor (BJT) during a first time period; disconnecting the base current source from the bipolar junction transistor (BJT) during a second time period; receiving a current measurement from a current detect circuit coupled to an emitter of the bipolar junction transistor (BJT); repeating the steps of driving the base current during the first time period and disconnecting the base current source for the second time period to obtain an average current output to a load; and dynamically adjusting the base current output from the base current source to adjust a reverse recovery time period of the bipolar junction transistor (BJT) based, at least in part, on the received current measurement. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. An integrated circuit (IC), comprising:
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a base current source configured to be coupled to a base of the bipolar junction transistor (BJT) through a first base switch; and a controller coupled to the base current source and configured to couple to an emitter switch coupled to an emitter of the bipolar junction transistor (BJT), wherein the controller is configured to perform the steps comprising; driving a base current from the base current source to the base of the bipolar junction transistor (BJT) to maintain conduction of the bipolar junction transistor (BJT) during a first time period; disconnecting the base current source from the bipolar junction transistor (BJT) during a second time period; receiving a current measurement from a current detect circuit coupled to an emitter of the bipolar junction transistor (BJT); repeating the steps of driving the base current during the first time period and disconnecting the base current source for the second time period to obtain an average current output to a load; and dynamically adjusting the base current output from the base current source to adjust a reverse recovery time period of the bipolar junction transistor (BJT), wherein at least a portion of the base current is proportional to a collector current of the bipolar junction transistor (BJT) based, at least in part, on the received current measurement. - View Dependent Claims (26, 27, 28)
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Specification