Himax Analogic, Inc.

Aung Aung Yinn

Chow-Peng Lee

Tyng-Yang Chen

Chin-Lung Wu

An error amplifier and a LED circuit comprising the same are provided. The LED circuit comprises an inductor, a group of LEDs and a power MOS connected to the inductor, an error amplifier and a pulse width modulator controlling the gate of the power MOS according to an error amplifier output. The error amplifier comprises a differential input stage, an output stage having a NMOS, a PMOS and an adjusting current source connected to the gate of the PMOS. During a first operation mode, a control voltage makes the adjusting current source turn on, and during a second operation mode, the control voltage makes the adjusting current source turn off.

Error amplifier and LED circuit comprising the same

A buck circuit having a fast transient response mechanism is provided. The buck circuit comprises a high side MOS, a low side MOS, a transient control module and an operation control module. The low side MOS is connected to the high side MOS at a connection point for generating an output voltage to an external load according to an input voltage from the high side MOS. The operation control module controls the operation of the high and the low side MOS according to the output voltage when the external load is in a heavy load state such that the transient control module is disabled. When the external load turns from the heavy load state to a light load state such that the output voltage raises over a predetermined level, the transient control module is enabled to turn on the low side MOS for discharging to pull down the output voltage.

Buck circuit having fast transient response mechanism and operation of the same

An error amplifier and a LED circuit comprising the same are provided. The LED circuit comprises an inductor, a group of LEDs and a power MOS connected to the inductor, an error amplifier and a pulse width modulator controlling the gate of the power MOS according to an error amplifier output. The error amplifier comprises a differential input stage, an output stage having a first NMOS, a first PMOS, a second NMOS, a second PMOS and a control switch module. During a first operation mode, the control switch module connects the first NMOS and PMOS and connects the second NMOS and PMOS, and during a second operation mode, control switch module disables the second NMOS and PMOS.

A LED circuit is provided. The LED circuit comprises: a plurality of LED channels, a driving module and a feedback-selecting module. The driving module supplies a driving voltage to the plurality of LED channels according to a feedback voltage. The feedback-selecting module comprises an open detection unit and a minimum-selecting unit. The open detection unit performs an open detection mechanism to separate the plurality of LED channels into a plurality of open LED channels and a plurality of non-open LED channels having an output voltage respectively. The minimum-selecting unit performs a selection mechanism to select a minimum output voltage as the feedback voltage from the output voltage of each of the plurality of non-open LED channels. A LED circuit operation method adapted in the LED circuit is provided herein as well.

LED circuit and operation method of the same having minimum output voltage selection mechanism to generate feedback voltage

A detection circuit is disclosed in specification and drawing, where the detection circuit includes a current source, a voltage-current converter and a current comparator. The voltage-current converter is configured to acquire a receiving current from the current source by comparing a reference voltage with an input voltage of a detecting terminal. The current comparator is configured to output an output voltage by comparing a steady current with an output current based on the receiving current.

Detection circuit

A short detection circuit, for detecting an output node corresponding to an output voltage converted from an input voltage of a power converter, includes a first current source, a charging/discharging unit, a comparator, and a logic control unit. The charging/discharging unit performs charging operation in accordance with the first current source to generate a charging signal in a shorted condition of the output node. The comparator outputs an enable signal by comparing the charging signal with a reference signal. The logic control unit is controlled by the enable signal to generate a fault signal for turning off a first switch coupled between the output node and the input voltage in the shorted condition of the output node. A method for detecting short of an output node corresponding to an output voltage converted from an input voltage of a power converter is also disclosed herein.

Power converter, short detection circuit thereof, and method for detecting short

A voltage converter to convert a high voltage to a low voltage is provided. The voltage converter comprises: a current mirror, a current bias, a plurality of loads and a low voltage output. The current mirror comprises a first PMOS and a second PMOS, wherein the source of the first PMOS and the second PMOS receive a high voltage input which is a supply voltage of the current mirror, and the gate of the first PMOS is connected to the drain of the first PMOS. The current bias is connected between the drain of the first PMOS and a ground potential. The plurality of loads are parallel connected between the drain of the second PMOS and the ground potential. And the low voltage output connected to the drain of the second PMOS.

Voltage converter

An LED driver includes a start-up feedback circuit, an operating feedback circuit and a multiplexer. The start-up feedback circuit has first terminals for receiving LED feedback voltages each delivered from at least one LED coupled to an output terminal for outputting an output voltage, of the LED driver, and generates a start-up feedback voltage accordingly. The operating feedback circuit has second terminals for receiving the LED feedback voltages, and generates an operating feedback voltage accordingly. The multiplexer selects the start-up feedback voltage for initial boost of the output voltage when the LED driver is initially activated, and selects the operating feedback voltage for following boost of the output voltage when the output voltage increases to a certain value.

LED driver and start-up feedback circuit therein

A LED circuit comprises: an inductor, a group of LEDs, a capacitor, a power MOS and a switching circuit. The inductor is connected to a voltage supply and a first node; the group of LEDs is connected to the first node and a ground potential; the capacitor is connected to the first node and a ground potential; the power MOS is connected to the first node and a ground potential, wherein the gate of the power MOS receives a switching signal such that the capacitor is charged when the power MOS is turn on to further turn on the LEDs and the capacitor is discharged when the power MOS is turn off to turn off the LEDs. The switching circuit is to generate the switching signal.

LED circuit with high dimming frequency

A frequency divider includes a transmission gate, a first inverter, a first switch circuit, a second switch circuit, and a second inverter. The transmission gate transmits a clock signal according to an inverted enable signal. The first inverter inverts the clock signal outputted from the transmission gate. The first switch circuit generates a first control signal according to the inverted clock signal and an output signal of the frequency divider. The second switch circuit generates a second control signal according to the clock signal, the inverted clock signal, and the first control signal. The second inverter inverts the second control signal to generate the output signal. The frequency of the clock signal is a multiple of the frequency of the output signal.

Counter and Frequency divider thereof

A short detection circuit to detect a short condition in a backlight module, wherein the backlight module comprises a WLED circuit having a first terminal connected to an output voltage and second terminal connected to a driver IC. The short detection circuit comprises: a PMOS, a NMOS, a load and a detection module. The gate of the PMOS receives a first voltage and the source of the PMOS connects to the second terminal; the gate of the NMOS receives a reference voltage, the drain of the NMOS connects to the drain of the PMOS and the source of the NMOS connects to a detection terminal. The voltage of the detection terminal becomes a high state when the WLEDs have a short condition; and the detection module is connected to the detection terminal, when the voltage of the detection terminal becomes a high state, the detection module detects a short condition.

Short detection circuit

A driving circuit includes a DC-to-DC voltage converter, a current source, a detector and a feedback control circuit. The DC-to-DC voltage converter has a switch and generates a driving voltage on first ends of the series of light emitting diodes, in which a magnitude of the driving voltage is correlated with conduction of the switch. The current source is coupled to second ends of the series of the light emitting diodes and provides driving currents flowing through the light emitting diodes. The detector generates a feedback voltage corresponding to a sum of voltages on the second ends of the series of the light emitting diodes. The feedback control circuit generates a first control signal which controls the conduction of the switch in response to the feedback voltage.

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Sinshih, Taiwan

Aung Aung Yinn