Abstract: A multi-stage LED driving circuit capable of eliminating current undershoot, including: an LED module having a plurality of stage output terminals; a plurality of switch units coupled with the stage output terminals to receive a plurality of branch currents and provide a plurality of current sensing signals; a current regulation circuit, having a control end coupled with a variable reference voltage, and a current path for receiving the branch currents; and a control unit, receiving the current sensing signals and a voltage signal at an input terminal of the current path, and controlling the switch units; wherein, the control unit uses every two adjacent signals of the current sensing signals to get a ratio in turn to determine whether to switch off a corresponding switch unit of the switch units after a deferred time, and uses the voltage signal to determine whether to change the deferred time.

Abstract: An LED driver having one end coupled with an LED module and another end coupled to a ground, being capable of generating a duty current and a duty in response to a dropout voltage across the LED driver in a way that, the duty current will increase and the duty will decrease when the dropout voltage exceeds a first threshold, and the duty current will decrease and the duty will increase when the dropout voltage falls below a second threshold.

Abstract: A power converter used in the current control circuit and control method, consisting of a converter, a voltage divider circuit, a current sampling circuit, a first gain circuit, a differential amplifier, a second gain circuit, a multiplier, a saw tooth wave generator, a modulation comparator, and a driver. The invention samples inductor current through the current sampling circuit and generates the current sense signal, then processes again. With the differential amplifier, it compares the feedback voltage from the voltage divider circuit with the reference voltage, and the results along a modulation comparator output a drive signal to control the duty cycle in order to avoid the generation of inrush current. The present invention avoids inrush current caused by the large drive signal and achieves a good response rate and better system stability.

Abstract: A power converter used in the current control circuit and control method, consisting of a converter, a voltage divider circuit, a current sampling circuit, a first gain circuit, a differential amplifier, a second gain circuit, a multiplier, a saw tooth wave generator, a modulation comparator, and a driver. The invention samples inductor current through the current sampling circuit and generates the current sense signal, then processes again. With the differential amplifier, it compares the feedback voltage from the voltage divider circuit with the reference voltage, and the results along a modulation comparator output a drive signal to control the duty cycle in order to avoid the generation of inrush current. The present invention avoids inrush current caused by the large drive signal and achieves a good response rate and better system stability.

Abstract: A voltage converter with a sampling-hold and integrating circuit is provided herein. According to the minimum different value generated by the practical status of each of the illuminant channels in the LED backlight module, the sampling-hold and integrating circuit will generate an superposition voltage and the voltage converter can output different PWM signal to drive each of the illuminant channels in the backlight module. When the sampling-hold and integrating circuit of the voltage converter and the control device with adjusting pulse width function are embedded together to provide to the LED backlight module, the power saving is more convenient.