ILLUMINATION DEVICE WITH ELECTRICAL VARIABLE SCATTERING ELEMENT
First Claim
1. A current limiting controller for a driver circuit, the current limiting controller comprising:
- a voltage detector for detecting a fault detection voltage corresponding to a voltage produced across a load by the driver circuit;
a current limiter for limiting a current supplied from the driver circuit to the load in response to the fault detection voltage falling below a threshold value;
a reset circuit for disabling the current limiter upon expiration of a first time interval after the fault detection voltage falls below the threshold voltage level, the reset circuit allowing the current limiter to limit the current supplied from the driver circuit to the load when the fault detection voltage remains below the threshold voltage after a second time interval. wherein the reset circuit comprises;
a delay circuit configured to set the first time interval;
a switch having a first state and a second state, the switch being configured in the first state to disable the current limiter, and being configured in the second state to allow the current limiter to respond to the fault detection voltage; and
a unijunction transistor configured to set the switch into the first state when the first time interval expires, and to set the switch into the second state when the second time interval expires.
1 Assignment
0 Petitions
Accused Products
Abstract
A current limiting controller (100) for a light emitting diode (LED) driver automatically resets the LED driver to normal operation after elimination of a fault. The current limiting controller (100) includes a fault detector to detect a fault across a load (20, 40) that is being driven by the driver circuit (10, 30); a current limiter (130, 230) to limit the current supplied from the driver circuit (10, 30) to the load (20, 40) in response to the detected fault; and a reset circuit (120, 220, 320) to disable the current limiter (130, 230) upon expiration of a first time interval after the fault is detected, and to allow the current limiter (130, 230) again to limit the current supplied from the driver circuit (10, 30) to the load (20, 40) when the detected fault remains after a second time interval.
31 Citations
20 Claims
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1. A current limiting controller for a driver circuit, the current limiting controller comprising:
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a voltage detector for detecting a fault detection voltage corresponding to a voltage produced across a load by the driver circuit; a current limiter for limiting a current supplied from the driver circuit to the load in response to the fault detection voltage falling below a threshold value; a reset circuit for disabling the current limiter upon expiration of a first time interval after the fault detection voltage falls below the threshold voltage level, the reset circuit allowing the current limiter to limit the current supplied from the driver circuit to the load when the fault detection voltage remains below the threshold voltage after a second time interval. wherein the reset circuit comprises; a delay circuit configured to set the first time interval; a switch having a first state and a second state, the switch being configured in the first state to disable the current limiter, and being configured in the second state to allow the current limiter to respond to the fault detection voltage; and a unijunction transistor configured to set the switch into the first state when the first time interval expires, and to set the switch into the second state when the second time interval expires. - View Dependent Claims (2, 3, 4, 5, 7, 8)
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6. (canceled)
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9. A method of controlling a driver circuit driving a load, the method comprising:
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supplying a load current from a driver circuit to a load; detecting a fault across the load; in response to the detected fault, limiting the load current to a limited current value and charging an emitter voltage of a unijunction transistor for a first time interval; upon expiration of the first time interval, conducting current through the unijunction transistor for a second time interval to disable the limiting of the load current, allowing the load current to exceed the limited current value for the second time interval; turning off the unijunction transistor at the end of the second time interval and detecting whether the fault remains after the second time interval; and in response to the fault still being detected after the second time interval, once again limiting the load current to the limited current value. - View Dependent Claims (10, 11, 12, 13)
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14. A current limiting controller for a driver circuit, the current limiting controller comprising:
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a fault detector for detecting a fault at a load that is being driven by the driver circuit; a current limiter for limiting a current supplied from the driver circuit to the load in response to the detected fault; a reset circuit for disabling the current limiter upon expiration of a first time interval after the fault is detected, the reset circuit adapted to allow the current limiter again to limit the current supplied from the driver circuit to the load when the detected fault remains after a second time interval, wherein the reset circuit comprises; a delay circuit configured to set the first time interval; a switch having a first state and a second state, the switch being configured in the first state to disable the current limiter, and being configured in the second state to allow the current limiter to respond to the fault detection voltage; and a unijunction transistor configured to set the switch into the first state when the first time interval expires, and to set the switch into the second state when the second time interval expires. - View Dependent Claims (15, 16, 17, 19, 20)
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18. (canceled)
Specification