LED driver circuit and LED driving method
First Claim
1. A light emitting diode (LED) driver circuit, comprising:
- a dimmer connected to an AC input;
a rectifier circuit that is configured to receive the AC input from the dimmer, and to rectify the AC input to generate an input voltage;
an LED string having a first end defined by an anode of an LED element in a first position in the LED string, and the LED string having a second end defined by a cathode of an LED element in a last position of the LED string, the anode of the LED element in the first position connected to the input voltage;
an LED conducting state detection circuit configured to detect a conducting state of the LED string, and to generate a discharge control signal in response to sensing the LED string in a non-conducting state wherein an LED current does not flow to the LED string; and
a current source coupled between the rectifier circuit and the anode of the LED element in the first position in the LED string, the current source configured to generate a discharge current according to the discharge control signal when the LED string is in the non-conducting state.
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Accused Products
Abstract
A light emitting diode (LED) driver circuit includes an LED string and a conducting state detection circuit. The conducting state detection circuit detects a conducting state of the LED string, and generates a discharge control signal upon sensing that the LED string is in a non-conducting state. A current source generates a discharge current according to the discharge control signal when the LED string is in the non-conducting state. A passive bleeder provides current compensation by internal regulator operation. An LED spike current suppression circuit suppresses spike current that can occur when the input voltage increases above a threshold. A bias supply circuit has an input capacitor that provides a bias voltage.
38 Citations
16 Claims
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1. A light emitting diode (LED) driver circuit, comprising:
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a dimmer connected to an AC input; a rectifier circuit that is configured to receive the AC input from the dimmer, and to rectify the AC input to generate an input voltage; an LED string having a first end defined by an anode of an LED element in a first position in the LED string, and the LED string having a second end defined by a cathode of an LED element in a last position of the LED string, the anode of the LED element in the first position connected to the input voltage; an LED conducting state detection circuit configured to detect a conducting state of the LED string, and to generate a discharge control signal in response to sensing the LED string in a non-conducting state wherein an LED current does not flow to the LED string; and a current source coupled between the rectifier circuit and the anode of the LED element in the first position in the LED string, the current source configured to generate a discharge current according to the discharge control signal when the LED string is in the non-conducting state. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A light emitting diode (LED) driver circuit, comprising:
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a dimmer connected to an AC input; a rectifier circuit that is configured to receive the AC input from the dimmer, and to rectify the AC input to generate an input voltage; an LED string having a first end that is connected to the input voltage, the LED string comprising at least one LED element; an LED conducting state detection circuit configured to detect a conducting state of the LED string, and to generate a discharge control signal in response to sensing the LED string in a non-conducting state wherein an LED current does not flow to the LED string; and a current source that is connected to the first end of the LED string, the current source being configured to generate a discharge current according to the discharge control signal when the LED string is in the non-conducting state; wherein the LED conducting state detection circuit comprises; a first transistor connected between a first node and a ground and operates according to a voltage at a first end of the at least one LED element; and a charging circuit connected to the first node, wherein the discharge control signal follows a voltage of the first node.
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9. A light emitting diode (LED) driver circuit, comprising:
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an LED conducting state detection circuit configured to detect a conducting state of an LED string, and to generate a discharge control signal in response to sensing that the LED string is in a non-conducting state wherein an LED current does not flow to the LED string; and a current source coupled between a first end of the LED string and an input voltage, the current source configured to control a discharge current that flows to the current source according to the discharge control signal when the LED string is detected to be in the non-conducting state. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification