LED technology has become increasingly popular in lighting in recent years. LEDs have many advantages over conventional lighting technologies. For example, LEDs consume less power and generate less heat. As a result, they are significantly more efficient. Often the color and color temperature can also be adjusted.
Further advantages are, for example, the absence of a switch-on delay (LEDs provide full brightness immediately after being switched on) and infinitely variable dimming.
Depending on the application, LED lights require either a constant current (CC) or constant voltage (CV) LED driver.
Holtek offers suitable ICs for both. Below we present the CC controller, which is available in two versions: HT7L5502 and HT7L5503
The HT7L5502/03 controller is suitable for implementing constant current LED drivers with active power factor correction (PFC). The current is regulated on the primary side and requires no further regulation or additional components on the secondary side. The accuracy of the regulation is ±3%.
The HT7L5502/03 is a quasi-resonant controller that operates in Boundary Conduction Mode (BCM). If the coil current drops to zero, the MOSFET is switched on. If the current reaches the set limit, the MOSFET is switched off. The Boundary Conduction Mode ensures low switching losses and high conversion efficiency.
The HT7L5502/03 also offers a dimming function. This can be implemented via PWM or analog. If the voltage at the DIM pin is within the specified limits, the LED current is proportional to the DIM voltage. The frequency for dimming via PWM is between 500Hz and 1kHz. The LED current is linearly proportional to the PWM for a duty cycle of 100% to 5%. Below this limit, the LED current is not linearly proportional and the controller switches to constant voltage mode.
The difference between the HT7L5502 and the HT7L5503 can be found in the dimming function. The HT7L5502 works with a dimming signal from the secondary side (via optocoupler), the HT7L5503 with a direct dimming signal on the primary side.
The protection functions can be seen in the block diagram as well as an NTC input to take the ambient temperature into account for LED current control. Detailed descriptions of this and the soft-start function and layout tips can be found in the Datasheet.
The most important features of the HT7L5502/03 constant current controller at a glance:
Do you need more information? Our team will be happy to advise you on the CC Controller HT7L5502/3 as an LED driver and other Holtek solutions. Contact us directly or send us your inquiry her