A light-emitting element driving device includes a reset signal generation unit that generates a reset signal in accordance with current flowing in a light-emitting element, a set signal generation unit that generates a set signal in accordance with the anode voltage of the light-emitting element, and an output voltage supply unit that generates an output voltage from an input voltage in accordance with the reset signal and the set signal, so as to supply the output voltage to the light-emitting element. The set signal generation unit includes a current generation unit that generates current according to the anode voltage of the light-emitting element, a charging unit that charges the current generated by the current generation unit, and a comparator that generates the set signal in accordance with a comparison result between a charging voltage of the charging unit and a reference voltage.

Circuits and methods for driving an LED from a secondary side of a transformer are disclosed herein. An embodiment of the method includes monitoring an input voltage to determine the power level intended to drive the LED. The current flow through the primary side of the transformer is adjusted to make the power actually driving the LED equal to the power intended to drive the LED.

Disclosed are a light emitting diode (LED) driver circuit having improved flicker performance and an alternating current-driving type LED lighting device including the same. The LED driver circuit can remove an LED off period using a charging and discharging circuit during a compensation period so as to reduce light output deviation of an LED lighting device, and provide a driving voltage to another element of the LED lighting device, using the charging and discharging circuit during an additional discharging period so as to simultaneously improve power efficiency.

A bidirectional voltage differentiator circuit comprises start-up circuitry, sensing circuitry, and output circuitry coupled to logic circuitry. The start-up circuitry acts to start-up the sensing circuitry when the circuit is powered on, and accelerates the response of the sensing circuitry thereafter. The sensing circuitry senses variation in an input voltage applied to an input node. Responsive to the voltage variation sensed by the sensing circuitry, the output circuitry produces a state change at a first or second output node. The logic circuitry receives the states of the output nodes and produces a logic output signal to indicate the occurrence of the variation sensed in the input voltage. The voltage sensing circuit is operable to sense variation of the input voltage regardless of whether the voltage is rising or falling and without regard to the DC value of the input voltage.

According to one embodiment, a vehicle lighting device includes a first circuit portion that has at least one light emitting element and a first resistor connected in series to the light emitting element; a second circuit portion that is connected in parallel to the first circuit portion and has at least a control portion; and a third circuit portion that is connected in series to the first circuit portion and the second circuit portion, and has at least one light emitting element.

The control portion measures an input voltage and causes a current to flow through the third circuit portion in a case where the measured input voltage is a predetermined value.

The present disclosure discloses a multipath current source switching device, including a switching control unit, N current paths, and N loads. Each current path is formed by a constant current source circuit and a switching circuit. One terminal of a first load is coupled to a load power supply, and the other terminal of the first load is coupled to an output terminal of a constant current source circuit of a first current path and one terminal of a second load; one terminal of an i.sup.th load is coupled to the other terminal of an (i−1).sup.th load and an output terminal of a constant current source circuit of an i.sup.th current path; and the switching control unit controls an output current of a corresponding constant current source circuit through a corresponding switching circuit. When the circuits are switched, an output voltage of a switching circuit of a current path to be switched off is decreased to zero according to a preset voltage variation quantity, and an output voltage of a switching circuit of a current path to be switched on is increased to a highest operating voltage according to the preset voltage variation quantity, such that a current on a load does not exceed a preset current and is not zero during switching. N is an integer not less than 2, and i is equal to 2, 3, 4, . . . , N.

A controller for a power converter. The power converter comprises a converter-switch and a converter-inductor. The controller comprises a controller-output-terminal configured to provide a switch-control-signal for the converter-switch, a comparator and a delay-block. The comparator can provide a comparator-output-signal that has a comparator-output-state dependent on whether or not a sensed-signal is greater than a reference-signal, wherein the comparator-output-state can take a first-state-value or a second-state-value. The delay-block can: set a time-delay-value based on: (i) a voltage across the converter-inductor; start a timer when the comparator-output-state changes; and cause a change in the switch-control-signal when the timer reaches the time-delay-value.

The present invention discloses a system and method for active power factor correction and current regulation in led circuit. The system (100) used in the LED driver circuit performs active PFC and current regulation through the dynamic input current wave shaping by limiting peak currents. The dynamic wave 5 shaping scheme is realized through hardware and firmware and is used to strike an optimal balance between current accuracy, Power factor, THD and peak inductor currents. The system (100) is versatile enough to improve PF and current accuracy in LED circuits and indimmers circuits.

A LED driver comprises two output contacts (310, 311) and an additional contact (312) which enables detection of connection of the LED driver to a LED module (301). The LED driver has a normal current regulating mode and an open circuit protection voltage regulating mode. The LED driver is switched from the voltage regulating mode to the current regulating mode in response to the detection of connection of the LED module. This enables a LED module to be connected to the LED driver while it remains powered, in particular because the LED driver is placed in a voltage regulating mode prior to connection to the LED module.

A constant current driving circuit can include: LED strings; a voltage regulator configured to provide an output voltage signal as a supply for the LED strings; current regulating circuits corresponding to the LED strings, and being coupled between the LED strings and ground, where the current regulating circuits are configured to regulate currents through the LED strings according to present currents and reference current signals; a voltage feedback circuit configured to receive input voltage signals of the current regulating circuits, and to select a voltage feedback signal for controlling the output voltage signal according to the voltage feedback signal and a reference voltage signal; and a signal generating circuit corresponding to the current regulating circuits, where each signal generating circuit receives an input voltage signal of a corresponding current regulating circuit, and generates an error amplifying signal according to the input voltage signal and the reference voltage signal.