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  • HV9963 Backlight LED Driver

  • Created: Oct 17, 2016

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Description

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Summary

Backlight LEDs are common application in digital TV. This backlight LEDs is the one responsible for the LCD images to be visible TV. It illuminates LCD from the side or back of the display panel, which increase the visibility of the images. The reference design is a backlight LED driver that features HV9963, a current mode control LED driver IC designed to control single switch PWM converters (buck, boost, buck-boost or SEPIC) in a constant frequency mode.


The reference design can be supplied from a voltage range of 22-26VDC, but HV9963 can accept input voltage ranging from 8V-40V. Pin J1 is the header for the input supply followed by the filter capacitor C1 & C2. This design is capable of driving 20 one-watt LEDs using boost topology. The switching frequency of the design is set by the value of R7. The current sense (CS) input is used to sense the source current of the switching FET. Resistor R5 is the sensing resistor for the circuit, while capacitor C5 programmed the slope compensation for this design. The LED current in the HV9963 is controlled in a closed loop manner. The current reference, which sets the LED currents output at the IREF pin, is set using a resistor divider (R9 and R11) from the AVDD pin (or can be set externally with a low voltage source). Pin J2 is the output pin thus the string of LED is connected. For protection of the LEDs, the HV9963 has also an over-current protection which trip off when the voltage at pin OVP is beyond 1.25V, thus turning of the pins GT and FLT of HV9963 and saturating transistor Q2. Feedback to the circuit is catered through pin FB which R8 as the feedback resistor. To achieve stable loop control, C13 and C9 are connected to pin COMP. Multiple HV9963s can be synchronized to each other or to an external clock using the SYNC pin.



The HV9963 can be applied also on battery powered lamps and other application that required backlights and dimming.