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  • 21-Watts Universal AC LED Driver

  • Created: Jun 20, 2016

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Summary

Lighting is the proper usage of lights to achieve a practical or aesthetic effect that includes both real lights and artificial lights. LEDs are the most commonly used components in this application, thus the need of LED drivers is to protect them from inrush current or changing temperature to prolong their lifespan. The reference design is a 21-watts universal LED driver demo board from Microchip, that features the HV9861A, an average-mode, constant-current control, LED driver IC operating in a constant off-time mode. The HV9861A is free from peak-to-average error resulting in improved accuracy, line and load regulation of the LED current without the use of loop compensation or high-side current sensing.


The reference design can handle AC power, which is being regulated by U1. The resistor RT1 is a NTC inrush current limiter, which primarily prevents the components in series with the input to the DC/DC converter from being damaged. The HV9861A can take a VIN ranging from 15-450V DC and it also implements tight regulation of the LED current with a few milliamps over the entire range of the input AC line and the output LED string voltage. The accuracy of the LED current is mainly determined by the internal 270mV ± 3% reference voltage of the HV9861A control IC and by the external current sense resistor tolerance. The HV9861A is capable of handling a PWM dimmed by applying a square wave TTL compatible in between the PWMD pin and ground. It has an internal current limiter comparator, which is used for hiccup mode output short circuit protection. The constant off-time control of the buck converter is used for stability and to improve the LED current regulation over a wide range of input voltages



The HV9861A can found its application also in LED back-light driver for LCD displays, LED signage, architectural and decorative LED lighting, and DC/DC or AC/DC driver application. The HV9861A also is compatible to its counterpart the HV9910B and HV9961 and can be directly be substituted in any applications.

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