Richtek Technology Corporation

Huan-Chien Yang

Shui-Mu Lin

Tsung-Wei Huang

Ti-Ti Liu

Shei-Chie Yang

Yung-Chun Chuang

Chueh-Kuei Jan

Jian-Ming Fu

Nang-Ching Yeung

Hui-Wen Cheng

Chuan-Yo Hsiao

Shih Chung Wang

A power converter includes an upper-gate circuit, a lower-gate circuit, an inductor, a first current sensor, a second current sensor, a weight adjustment circuit, and a PWM (Pulse Width Modulation) controller. The upper-gate circuit receives an input voltage. The lower-gate circuit is coupled to a ground node. The upper-gate circuit and the lower-gate circuit are operated according to the PWM voltage. The inductor is coupled to the upper-gate circuit and the lower-gate circuit. The first current sensor monitors the upper-gate circuit, so as to generate a first detection current. The second current sensor monitors the lower-gate circuit, so as to generate a second detection current. The weight adjustment circuit generates a control current according to the first detection current and the second detection current. The PWM controller generates the PWM voltage according to the control current.

Power converter and control method thereof

A switching regulator includes a power stage circuit and a controller circuit. The controller circuit includes a first amplification circuit, a second amplification circuit, a ramp signal generation circuit, and a comparator. The first amplification circuit generates an amplification signal according to a difference between a low-pass filtered signal and a feedback signal. The second amplification circuit generates an adjustment signal according to a difference between the feedback signal and a fast response signal. The comparator generates a pulse width modulation signal according to a difference between the amplification signal and a ramp signal to generate a switch control signal. The adjustment signal adaptively adjusts the amplification signal or the ramp signal. The low-pass filtered signal is related to a signal generated by filtering out higher frequency part of the reference signal, and the reference signal is related to a dynamic change of a target level of the output voltage.

Switching regulator and controller circuit and control method thereof

A PWM (Pulse Width Modulation) controller includes a current detector, a current emulator, a voltage-to-current converter, and a current adder. The current detector detects a first current, and generates a second current according to the first current. The current detector receives an input voltage and outputs an output voltage. The current emulator obtains the relative information of a lower-gate current. The voltage-to-current converter draws a third current from the current emulator according to the input voltage and the output voltage. The current emulator generates a fourth current according to the relative information and the third current. The current adder adds the fourth current to the second current, so as to generate a sum current.

Pulse width modulation controller and control method thereof

A switching power conversion circuit includes a conversion capacitor, a capacitive power conversion circuit, an inductor, an inductive power conversion circuit and a switching control circuit. The capacitive power conversion circuit switches the conversion capacitor periodically according to a switching control signal generated by the switching control circuit, to generate a first intermediate voltage and a first proportional voltage in a promptly rising mode and to generate a second intermediate voltage and a second proportional voltage in a promptly falling mode. In the promptly rising mode, a rising slope of an inductor current is determined by a difference between a high level of the first proportional voltage and an output voltage. In the promptly falling mode, a falling slope of the inductor current is determined by a difference between a low level of the second proportional voltage and the output voltage.

Switching power conversion circuit and switching circuit

A switching power conversion circuit includes a conversion capacitor, a capacitive power conversion circuit, an inductor, an inductive power conversion circuit and a switching control circuit. The capacitive power conversion circuit includes plural switching devices for generating an intermediate voltage which is in a predetermined proportional relationship to the input voltage. The inductive power conversion circuit includes plural switching devices for converting the intermediate voltage to an output voltage. The plural switching devices of the capacitive power conversion circuit and the inductive power conversion circuit switch the conversion capacitor and the inductor periodically according to the duty ratio of the switching control signal generated by the switching control circuit. The capacitive power conversion circuit and the inductive power conversion circuit share one of the plural switching devices.

A light emitting device driver circuit includes: a power conversion circuit, an error amplifier circuit, a sample-and-hold circuit, a load current generation circuit and a feed-forward capacitor. When the light emitting device driver circuit is in a disable phase, the sample-and-hold circuit connects a feedback signal with a second reference voltage and the sample-and-hold circuit disconnects the feedback signal from a load node, whereby the feed-forward capacitor samples a sample voltage and holds it after the disable phase transits to an enable phase. In the enable phase, the sample-and-hold circuit disconnects the feedback signal from the second reference voltage and the sample-and-hold circuit connects the feedback signal with the load node, so that during a predetermined period following the transition, there is a sufficient difference between two input terminals of the error amplifier circuit so that the load current is raised to a desired current level within the predetermined period.

Driver circuit for driving light emitting device

A LED driver using a PWM signal for dimming control includes a power converter and a current regulator. The power converter provides an output voltage and a load current for a plurality of LEDs. The current regulator provides a load current dependent signal for the power converter to speed up load transient response caused by variation of the load current, to reduce the ripple of the output voltage, and thereby to avoid audio noise during PWM dimming.

Avoid audio noise of a LED driver during PWM dimming

A method for brightness control, adapted to a light emitting device emitting a light of an output brightness, comprises: setting the output brightness to be an initial value, and controlling the light emitting device emitting the light accordingly; setting a target value, and controlling the output brightness changing from the initial value toward the target value with the brightness changing rate of the brightness zone corresponding to the initial value; controlling the output brightness changing toward the target value with the following brightness changing rate when the output brightness crossing one of the brightness thresholds and entering the following brightness zone, wherein the following brightness changing rate corresponds to the following brightness zone; stopping changing the output brightness when reaching the target value.

Method for brightness control

An LED driver includes a power converter to convert an input voltage to a regulated voltage, a current source to be connected with an LED string in series between the power converter and a bias node, and a switching circuit to apply a bias voltage to the bias node to set the total voltage drop of the LED string and the current source. By controlling the total voltage drop of the LED string and the current source, the LED driver will automatically select a boost mode or a buck mode for operation, thereby improving the efficiency thereof.

LED driver and driving method

The present invention discloses an LED controller with de-flicker function and an LED de-flicker circuit and method thereof. The LED controller includes: a duty ratio calculation circuit for receiving a pulse width modulation (PWM) signal and generating a duty input signal, indicating a digital duty ratio of the PWM signal; an LED de-flicker circuit for receiving the duty input signal and generating a duty output signal wherein a noise in the duty input signal is filtered; and a dimming circuit for receiving the duty output signal and generating a dimming signal to control an LED circuit; wherein the duty output signal remains unchanged when the variation of the duty input signal is not larger than a hysteresis threshold, and the duty output signal follows the duty input signal when the variation of the duty input signal is larger than the hysteresis threshold.

LED controller with de-flicker function and LED de-flicker circuit and method thereof

The present invention provides a transistor switch on a light emitting device channel, the transistor switch receiving a control voltage VG. A current source circuit controls the current on the light emitting device channel, the current source circuit requiring a minimum voltage VR for normal operation. The present invention further provides a dynamic headroom controller circuit which compares a voltage VS at a current outflow end of the transistor switch with the voltage VR to determine the relationship between the voltage VS and the voltage VR when the control voltage VG is higher than a reference voltage VH, and adjusts the voltage difference between the voltage VS and the voltage VR accordingly.

Circuit and method for controlling light emitting device, and integrated circuit therefor

The present invention discloses an adaptive two-stage voltage regulator and a method for controlling the same. The adaptive two-stage voltage regulator includes: a voltage regulator for converting an input voltage (Vin) to a middle voltage (Vm), wherein Vin&#x2266;Vin_max; a linear regulator for converting the middle voltage to an output voltage (Vout); and a middle voltage controller for adjusting the middle voltage according to (1) an input voltage indicator and one of (2a) an output voltage indicator and (2b) a predetermined reference signal, such that when Vin&#x2266;Vout, Vm=Vout+&#x394;V and (Vout+&#x394;V)&#x3c;Vin_max.

Adaptive two-stage voltage regulator and method for two-stage voltage regulation

A boost converter includes a load disconnect switch connected between a voltage input terminal and an inductor, a power switch connected to the inductor by a switching node, a diode connected between the switching node and a voltage output terminal, and an output capacitor connected to the voltage output terminal to provide an output voltage. A protection apparatus is connected to the load disconnect switch, switching node and power switch to monitor the voltage at the switching node and the output voltage to provide open circuit and short circuit protection for the boost converter.

Short circuit and open circuit protection for a boost converter

A LED display system includes multiple LEDs, a power converter to produce a supply voltage for the LEDs, and multiple drivers to drive the LEDs. According to the maximum one of the forward voltages of the LEDs, the drivers provides a feedback signal for the supply voltage control, and the feedback signal is amplified or digitized to reduce the voltage drop in the global power line.

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Taipei, Taiwan

Huan-Chien Yang