Cascode-type Dimming Switch Using A Bipolar Junction Transistor For Driving A String Of Light Emitting Diodes
AssigneeMicrochip Technology Incorporated
InventorAlexander Mednik
Life of this patent
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Abstract
The invention comprises a dimming switch for use with a string of light emitting diodes (LEDs). The dimming switch comprises a bipolar junction transistor (BJT) driven in a cascode scheme. The dimming switch also comprises circuitry to offset the current that drives the base of the BJT to provide a controlled amount of current to the LEDs when the dimming input signal is high.
Claims26
A dimming switch for use with a string of light emitting diodes, comprising:
- a bipolar junction transistor and a field effect transistor coupled in a cascode configuration, the gate of the field effect transistor receiving a dimming input signal and the collector of the bipolar junction transistor capable of driving a string of light emitting diodes;
- and
- a control circuit coupled to the bipolar junction transistor and the field effect transistor, wherein the current through the collector is unaffected by the current through the base of the bipolar junction transistor.
A lighting system responsive to a dimming input signal, comprising:
- a bipolar junction transistor and a field effect transistor coupled in a cascode configuration, the gate of the field effect transistor receiving a dimming input signal;
- a string of light emitting diodes connected to the collector of the bipolar junction transistor;
- and
- a control circuit coupled to the bipolar junction transistor and the field effect transistor, wherein the current through the collector is unaffected by the current through the base of the bipolar junction transistor.
A dimming switch for use with a string of light emitting diodes, comprising:
- a means for driving current through the string of light emitting diodes in response to a dimming input signal.
A lighting system, comprising:
- a string of light emitting diodes;
- a means for driving current through the string of light emitting diodes in response to a dimming input signal.
Dependencies are inferred from the claim text.