Linear Technology Corporation

Richtek Technology Corporation

Richtek Technology Corporation, R.o.c

Richtek Technologies Corporation, R.o.c.

Chiawei Liao

Jing-Meng Liu

Leng-Nien Hsiu

Robert C Dobkin

Hsin-Kai Chiang

Xiaoyong Zhang

The present invention discloses a backlight control circuit with flexible configuration, comprising: a light emitting device path; a current source for controlling the current amount on the light emitting device path, the current source receiving a relatively high reference voltage in a first state, and receiving a relatively low reference voltage in a second state; and a current source control circuit for controlling the current source, whereby when the light emitting device path is in normal use, the current source is set to the first state, and when the light emitting device path is not in normal use, the current source is set to the second state.

Backlight control circuit with flexible configuration

The present invention discloses a backlight control circuit, comprising: a voltage supply circuit for receiving an input voltage and generating an output voltage under control by a control signal; at least one voltage comparison path respectively coupled to at least one light emission device path; a voltage operative amplifier circuit for generating the control signal according to a lowest voltage on the at least one voltage comparison path; and at least one under current detection circuit for detecting whether a corresponding one of the at least one light emission device path is in an under current status, whereby when anyone of the under current detection circuits detects the under current status, it sends an exclusion signal excluding a corresponding one of the at least one voltage comparison path from being an effective input of the voltage operative amplifier.

Backlight control circuit with under current detection and start-up control

The present invention discloses a current splitter circuit for splitting a supply current to multiple light emitting device strings of a light emitting device array. The current splitter circuit includes: a minimum selector circuit coupled to the multiple light emitting device strings to generate a minimum signal which indicates a minimum voltage of the light emitting device strings; and multiple current source circuits each including a first current source end coupled to a corresponding light emitting device string, a second current source end coupled to ground, and a current source control end receiving a current control signal related to the minimum signal, so as to control currents through the corresponding light emitting device string.

Light emitting device array driver circuit and current splitter circuit and method of splitting current therefor

The present invention discloses a dimming control circuit and a method for generating analog and digital signals according to an analog control signal. The dimming control circuit according to the present invention comprises an input for receiving an analog control signal; a digital dimming circuit for receiving the analog control signal and generating a digital signal; an analog dimming circuit for receiving the analog control signal and generating an analog signal; and a power circuit enabled by the digital signal for converting a supply voltage to an output voltage according to the analog signal generated by the analog dimming circuit.

Dimming control circuit and method for generating analog and digital signals according to one analog control signal

The present invention discloses a backlight control circuit capable of distinguishing an under current condition, comprising: at least one light emission device path having a voltage node; at least one current source for controlling the current amount on the light emission device path; and at least one under current detection circuit for generating a first control signal according to the voltage at the voltage node, wherein when the first control signal changes its state, the under current detection circuit generates a second control signal to change the voltage on the voltage node if the light emission device path is normally connected.

Backlight control circuit capable of distinguishing under current condition

The present invention discloses a tail-less LED control circuit, which includes: a power supply stage having an output terminal which provides electrical power to an LED circuit; an output capacitor coupled to the output terminal; an LED driver circuit coupled to the power supply stage for controlling the power supply stage to provide the electrical power to the LED circuit, the LED driver circuit receiving a PWM dimming signal for adjusting brightness of the LED circuit; and a MOSFET switch coupled to the output capacitor in series, the MOSFET switch switching synchronously with the PWM dimming signal to alleviate LED afterglow, wherein the MOSFET switch includes a body diode having an anode-cathode direction against the discharge direction of the output capacitor.

Tail-less LED control circuit

The present invention discloses a backlight control circuit, and a method for controlling light emission devices. The method comprises: providing a plurality of light emission device paths connected in parallel; and setting a total current of the paths connected in parallel to a constant.

Backlight control circuit with low brightness variation when light emitting devices not operating

The present invention discloses a dimming control circuit, comprising: an input terminal for receiving an input signal; an analog and digital dimming circuit receiving the input signal, wherein the analog and digital dimming circuit provides an analog dimming function when a voltage level of the input signal is between a predetermined lower limit and a predetermined upper limit, and a digital dimming function when the voltage level of the input signal switches above and below the predetermined lower limit, and wherein the analog and digital dimming circuit generates an analog signal when the voltage level of the input signal is above the predetermined lower limit; and a power circuit for supplying an output current in correspondence to the analog signal generated by the analog and digital dimming circuit.

Dimming control circuit

Controlled compensation for a switching regulator is attained by detecting switching duty cycle of the switching regulator, developing a compensation signal having a time duration that is related to the detected switching duty cycle percentage, and generating a duty cycle control signal for the regulator that is dependent in part on the developed compensation signal. The compensation signal has a slope profile and is initiated during each switching cycle at a set point in the cycle that is related to the switching duty cycle percentage,

Switching regulator with variable slope compensation

Output voltage overshoot of a switching regulator is controlled by deactivating switching operation when a signal proportional to the output voltage exceeds a variable threshold level, with the threshold level set as a function of regulator output current. In accordance with an embodiment, a difference signal is generated that corresponds to a difference between an output voltage feedback signal and a constant reference voltage. The generated difference signal is combined with a signal proportional to load current to obtain an adapted threshold level. The adapted threshold level is greater than the level of the constant reference voltage. A regulator switch is reset to an off state when the output voltage feedback signal exceeds the adapted threshold level.

Switching regulator over voltage reduction circuit and method

A clock oscillator system for use in providing the switching regulator duty cycle control in a fixed frequency (no cycle skipping) operation is provided. In one embodiment, the circuit according to the invention uses an analog feedback loop to extend the switch ON time of the clock cycle by controlling the oscillator charging current and, thereby, increase the duty cycle. Preferably, this circuit can achieve very high switching duty cycle and/or very low switching duty cycle in a PWM switching regulator operated in very low drop-out operation when very high duty cycle is required or in other conditions when very low duty cycle is required.

Switching regulator duty cycle control in a fixed frequency operation

Switching regulator Burst Mode control circuitry is provided for limiting voltage overshoot at the output of a switching regulator operating in power saving Burst Mode. The Burst Mode control circuitry may include regulator load current sensing circuitry which may be operative to put and maintain the regulator in the SLEEP state when the load current amplitude is below a threshold. The control circuitry may also include gated over-voltage comparator circuitry operative to reduce regulator output overshoot and to eliminate erroneous deactivation of the regulator switch circuitry when the regulator is not operating in Burst Mode. The gated over-voltage circuitry may include a one-shot timer circuit.

Methods and circuits for output over-voltage reduction in switching regulators

A slope compensation circuit that provides slope compensation in a switching regulator is provided. The slope compensation circuit preferably is adapted to receive an oscillator pulse train from a pulse width modulator oscillator and a modulator pulse train from a pulse width modulator. The circuit preferably includes a feedback loop that is responsive to the oscillator pulse train. The circuit preferably provides a slope compensation pulse train of ON and OFF states that is responsive in part to the feedback loop and in part to the pulse width modulator switch pulse train. The invention preferably achieves lower maximum slope compensation current by incorporating an analog feedback loop in the PWM system to start slope compensation preferably only slightly ahead of PWM switch-OFF. This preferably occurs independent of the PWM duty cycle.

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San Jose, CA, United States of America

Chiawei Liao