Semiconductor Components Industries, LLC

Fairchild Korea Semiconductor Ltd.

Hyunchul Eum

Youngjong Kim

Kuo-Hsien Huang

Chih-Chun Chuang

Moon Sik Song

Moon Ho Choi

Seunguk Yang

Eungwoo Lee

Young Mo Yang

Young Je Lee

Jintae Kim

Moonsik Song

Inki Park

Minha Hwang

Gyumin Park

The present disclosure is related to accurate analog dimming of a light emitting diode (LED). Accurate dimming can require precise control of a power converter that supplies the LED with a current. The precise control relies on accurately sensing a level of the LED. When the power converter operates in a discontinuous conduction mode (DCM), for example at a low dimming ratio, the accuracy of the sensed LED-level can be affected by a resonant current offset, resulting from current ringing in the power converter. The disclosed circuits and methods provide accurate control of the LED-level by compensating for the resonant current offset in the sensed LED-level.

Current control for power converter

A circuit for controlling a lighting system includes a phase angle detector detecting a phase angle of a rectified input signal and generating a phase angle signal indicative of the phase angle, and a current shape controller determining a current shaping signal using the detected phase angle and adjusting the rectified input signal in response to the current shaping signal. The current shape controller varies a limiting value of the rectified input signal with the phase angle.

System and method for shaping input current in light emitting diode (LED) system

A circuit includes a power supply circuit and a ripple reduction circuit. The power supply circuit supplies a Direct Current (DC) lighting current to a light emitting circuit. The lighting current has a ripple current at a ripple frequency. The ripple reduction circuit receives the lighting current, and performs, based on the received lighting current, Pulse Width Modulation (PWM) of the lighting current at a PWM frequency. The PWM frequency is higher than the ripple frequency. By performing the PWM, the ripple reduction current reduces variations in a magnitude of the lighting current at the ripple frequency. The PWM frequency may be higher than a frequency at which variations in the magnitude of the light produced by the lighting circuit have a harmful effect on the human eye.

Line ripple reducer

A phase-cut dimming control system according to the embodiment includes a phase angle detector configured to detect a phase angle of an input voltage generated by phase-cut dimming, a feedback signal generator configured to generate a first reference signal corresponding to the detected phase angle, and generate an initial feedback signal based on a detection signal corresponding to power supplied to a load and the first reference signal, a feedback signal modulator configured to modulate the initial feedback signal and generate a feedback signal, a power transmission controller configured to generate a control signal which controls power transmission according to the feedback signal, and a power transmission circuit configured to transmit power to the load according to the control signal.

Control system for phase-cut dimming

A method for controlling a lighting system includes detecting a phase angle of a rectified input signal, determining a current shaping signal using the detected phase angle, and adjusting the rectified input signal in response to the current shaping signal. A circuit for controlling a lighting system includes a phase angle detector detecting a phase angle of a rectified input signal and generating a phase angle signal indicative of the phase angle, and a current shape controller determining a current shaping signal using the detected phase angle and a scaled input signal and adjusting the rectified input signal in response to the current shaping signal.

A lighting circuit includes a light emitting diode (LED), a transistor that controls a current through the LED, and a lighting controller integrated circuit (IC) that controls the transistor to vary a brightness of the LED. The controller IC has a dimming pin that receives a dimming signal. The controller IC generates a low reference threshold and a high reference threshold that follow the dimming signal. The lighting controller IC controls the transistor by hysteretic control by comparing a sense signal indicative of the current through the LED to the low reference threshold and the high reference threshold.

Lighting circuit with internal reference thresholds for hybrid dimming

A lighting circuit includes a light emitting diode (LED), a transistor that controls a current through the LED, and a controller integrated circuit (IC) that controls the transistor to vary a brightness of the LED. The controller IC has a dimming pin that receives a hybrid dimming signal from a dimming input circuit. The dimming input circuit receives pulse width modulation (PWM) dimming signals and generates the hybrid dimming signal as a PWM dimming signal, an analog dimming signal, or both depending on the received PWM dimming signals.

Hybrid dimming for lighting circuits

A light emitting diode (LED) lighting circuit includes a ripple reducer. The ripple reducer includes a ripple detector, an adaptive offset generator, and a linear regulator. The ripple detector generates a ripple voltage that is indicative of a ripple current. The adaptive offset generator generates an adaptive offset voltage from the ripple voltage and from a voltage of a transistor. The linear regulator drives the transistor to regulate an LED current in accordance with a reference control voltage that is generated from the ripple voltage and the adaptive offset voltage.

LED lighting circuit with ripple reducer

Provided is a standby current supplier including a bleeding circuit electrically connected to a dimmer and through which a first current flowing to the dimmer flows when the dimmer is in an off state, and a first controller configured to detect a first voltage corresponding to an input voltage generated by the dimmer and control the bleeding circuit based on the first voltage when the first voltage is lower than a predetermined first level.

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Seoul, South Korea

Hyunchul Eum