Holtek HT7L4091 Universal High Brightness LED Lighting Control Solution

Holtek’s HT7L4091 is a general-purpose PWM controller for high-brightness LED lighting control. It is a control chip with cycle-by-cycle current control, peak current control method combined with a fixed off-time. The HT7L4091 includes LED open-circuit protection, over-temperature protection, under-voltage protection, and enhanced short-circuit protection. It is suitable for general lighting such as LED tubes and light bulbs; it is also suitable for different applications such as advertising billboard backlighting and large-size LCD backlighting. This article introduces the main features of the HT7L4091, the block diagram and various typical application circuits.

HT7L4091: Universal Step-Down PWM Control For High Brightness LED Lighting Control

The HT7L4091 device provides a low-cost solution for active current mode PWM controls of High Intensity LED drive systems supplied by either AC or DC line power lines. The device operates in constant off-time mode which is suitable for buck LED drivers. The low start-up and operating currents provides flexible power requirements for high efficiency or low cost applications. The switch frequency off-time can be programmed using an external resistor. The peak current mode control achieves good output current regulation without requiring loop compensations for a wide range of input voltages.

Included in the device is a PWM dimming input which can accept an external control signal with a duty ratio from 0 to 100%. The output current can be programmed from 0 to 250mA by applying an external control voltage on the linear dimming control input.

The device includes a frequency jitter function which helps to reduce EMI power supply emissions. from damage should the LEDs be short circuited. .

The device requires a minimum number of external standard components and is available in an 8-pin NSOP package for small area PCB applications.

Main features of HT7L4091:

●●Input supply AC voltage range: 100V~240V

●●Ultra Low Power-on Start-up current < 30μA

●●Integrated 25V Zener diode internally connected to VIN pin

●●5V LDO output voltage with 6mA driving current for external components

●●Frequency jitter function for enhanced EMI performance

●●Efficiency > 85%

●●Under Voltage Lockout Function – UVLO

●●Current mode operation with cycle-by-cycle current limiting

●●Over Temperature Protection Function

●●High-current FET Drive Output

●●Linear and PWM Dimming Function

●●Enhanced Short Circuit Protection Function

HT7L4091 application:

●●AC/DC and DC/DC Power control For High Power LED Lighting

●●RGB back lighting LED driver

●●Flat Panel Displays Back Lighting

●●General Purpose Constant Current Source

●●Signage and Decorative LED lighting

●●Battery Chargers

figure 1. HT7L4091 block diagram

figure 2. HT7L4091 Typical Application Circuit

image 3. Application circuit of HT7L4091 without input large capacitance

Figure 4. HT7L4091 High Efficiency Application Circuit

Figure 5. HT7L4091 BJT power application circuit

Application Circuit Bill of Materials:

For details, see:
http://www.holtek.com.tw/PDF/consumer/HT7L4091v100.pdf