An illumination device and method is provided herein for calibrating individual LEDs in the illumination device, so as to obtain a desired luminous flux and a desired chromaticity of the device over changes in drive current, temperature, and over time as the LEDs age. The calibration method may include subjecting the illumination device to a first ambient temperature, successively applying at least three different drive currents to a first LED to produce illumination at three or more different levels of brightness, obtaining a plurality of optical measurements from the illumination produced by the first LED at each of the at least three different drive currents, obtaining a plurality of electrical measurements from the photodetector and storing results of the obtaining steps within the illumination device to calibrate the first LED at the first ambient temperature. The plurality of optical measurements may generally include luminous flux and chromaticity, the plurality of electrical measurements may generally include induced photocurrents and forward voltages, and the calibration method steps may be repeated for each LED included within the illumination device and upon subjecting the illumination device to a second ambient temperature.

An LED tube lamp having an LED unit is disclosed. The LED tube lamp includes a control circuit that selectively determines whether to perform a first mode or a second mode of lighting operation according to a state of a property of an external driving signal and a switching circuit coupled to the control circuit and the LED unit. When the control circuit determines to perform the first mode of lighting operation, the control circuit controls the second circuit in a manner such that the switching circuit maintains its on state to allow continual current to flow through the LED unit, until the external driving signal is disconnected from the LED tube lamp, and when the control circuit determines to perform the second mode of lighting operation, the control circuit controls the switching circuit in a manner to regulate the continuity of current to flow through the LED unit by alternately turning on and off the switching circuit.

An LED driver is provided with transient protection circuitry to satisfy dielectric testing requirements. An embodiment of the driver includes a fuse coupled between an AC input and a DC power source, and first and second electrolytic capacitors coupled across the DC power source. Respective circuits including a transient voltage suppressor and a current limiting resistor are coupled in series across each of the electrolytic capacitors. The transient voltage suppressors have breakdown voltage thresholds slightly below a full rated output for the DC source, wherein a sensed short condition across one of the first and second electrolytic capacitors causes a short circuit across the DC source and thereby disabling of the LED driver prior to failure of the other electrolytic capacitor. The current limiting resistors further are configured to avoid causing the LED driver to be disabled for transient overvoltage conditions in which neither of the electrolytic capacitors is shorted.

Methods for controlling power consumption and temperature in an LED luminaire are disclosed. The LED luminaire has one or more sets of LED light engines disposed on a printed circuit board (PCB), some or all of which are activated in response to an instruction or set of instructions. The instruction or set of instructions are processed to derive an indication of power consumption for each of the one or more sets of LED light engines. Power allocations for the one or more sets of LED light engines are adjusted to meet targets. This can be done by, e.g., ramping up or down the duty cycle of active sets of LED light engines by a uniform factor until the targets are met. Temperature control methods similarly ramp down the duty cycle of active sets of LED light engines uniformly over time if the measured temperature of the PCB exceeds limits.

In accordance with an embodiment, a switched-mode power converter includes a switch, a freewheeling diode coupled between an output terminal of the switch and a power supply input node, an inductor coupled between the output terminal of the switch and a power supply output node, and a passive network having a first terminal coupled to the output terminal of the switch, a second terminal coupled to a power supply output node, and a third terminal coupled to a reference terminal of the switch. A method includes measuring a first voltage at a fourth terminal of the passive network when the switch is on; measuring a second voltage at the fourth terminal of the passive network when the switch is off; and estimating an output voltage between the power supply output node and the reference terminal of the switch based on the first voltage and the second voltage.

Light sources for replacing fluorescent lamps comprise light circuits with light emitting diodes, first and second terminals located at first and second ends of the light sources for exchanging first signals with high-frequency ballasts, and converter circuits for converting the first signals into second signals for feeding the light circuits. The converter circuits comprise reactive circuits for matching the light circuits and the high-frequency ballasts and provide safety to persons when installing the light sources. The light sources may further comprise protection circuits for protecting parts of the light sources against problems. The protection circuits may comprise monitor circuits for monitoring parameters of the light sources and for in response to monitoring results short-circuiting outputs of the converter circuits, and fuses. The reactive circuits may comprise protecting capacitors.

A light emitting diode (LED) tube lamp includes a lamp tube having four pins for receiving an external driving signal; a first rectifying circuit coupled to two of the four pins to rectify the external driving signal; a second rectifying circuit coupled to another two of the four pins to rectify the external driving signal; a filtering circuit coupled to the first and the second rectifying circuits to filter rectified signal; and an LED lighting module coupled to the filtering circuit to receive filtered signal to emit light. The first rectifying circuit further includes a terminal adapter circuit for providing four terminals correspondingly coupled to the four pins. With function of the terminal adapter circuit, the LED tub lamp is compatible with an AC driving mode and a ballast driving mode. The LED lighting module further includes a driving circuit having a controller and a converter circuit. The controller receives a current detection signal for controlling or stabilizing the driving signal output by the converter circuit to be above an objective current value. The controller is further coupled to the filtering circuit for setting the objective current value according to the voltage output by the filtering circuit.

The present disclosure discloses a protective circuit for an output terminal capacitor of a light-emitting diode (LED) driver, and a method for providing the protective circuit. The protective circuit is connected to two ends of the output terminal capacitor and includes a switching element, a voltage dividing unit and a one-way conduction unit. The switching element is in parallel connection with the output terminal capacitor, the one-way conduction unit is connected between the switching element and the output terminal capacitor, the switching element is switched on when a voltage exceeds a threshold so as to establish a short circuit between two ends of the output terminal capacitor and prevent an excessively large voltage from being applied to the output terminal capacitor, and the one-way conduction unit allows a current to flow across the output terminal capacitor from the protective circuit by a one-way conduction.

An AC-DC power supply receives input AC power and outputs DC power. The converter includes a high power factor bridge rectifier, a barrier circuit with resistor(s) and capacitor(s), and a step-down switching DC-DC converter to step-down a first DC voltage to a second, lower, DC voltage for output. Additionally, fault-protection is provided by redundancy in diodes on diode legs of a bridge rectifier and capacitor(s) of a filter circuit thereof, and a fault-protection circuit to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.

An AC-DC power supply receives input AC power and outputs DC power. The converter includes a high power factor bridge rectifier, a barrier circuit with resistor(s) and capacitor(s), and a step-down switching DC-DC converter to step-down a first DC voltage to a second, lower, DC voltage for output. Additionally, fault-protection is provided by redundancy in diodes on diode legs of a bridge rectifier and capacitor(s) of a filter circuit thereof, and a fault-protection circuit to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.