L6574

Today’s lighting fixtures are expected to go beyond simple on/off switches and provide further control over light intensity and color temperature for a range of different applications. Because of this, more and more control devices and circuits are being developed to govern power distribution and other elements within the fixture. The L6574 is an integrating voltage-controlled switch from STMicroelectronics which provides an ideal solution for a wide range of lighting applications. This article will discuss the applications of the L6574, as well as its underlying working principle.

L6574 Application Field

The L6574 was launched in 2017 and is a dual-output integrated power-factor-corrected (PFC) voltage-controlled switch. It is primarily designed to drive light loads operating between 8W and 350W, and as such is ideal for controlling LEDs, halogens, and fluorescent lamps. It is capable of intelligently controlling the current or dimming of a light source while maintaining a power factor of above 0.9. This makes it convenient for applications in the residential, commercial, and industrial lighting industries.

The L6574 also enables real-time dimming control through a 0-10V dimmer, as well as by using PWM signals. Furthermore, the device helps reduce power losses as it integrates active and passive EMI/EMC filtering components, as well as a full control loop. Finally, its DDM (dynamic detect mode) feature offers voltage-transient protection in line dimming applications, making it highly reliable and cost-effective.

L6574 Working Principle

The L6574 is based on a voltage-controlled switch topology, and thus is capable of detecting and amplifying the signal of an external voltage source. It uses a low-frequency signal, typically located around 16kHz, to amplify and produce its own output voltage signal. This signal is then fed to a power factor controller, which in turn is fed to the control component of the switch. The control component then regulates the power load and uses the signal of the power factor controller to adjust the current and voltage.

The output of the switch is regulated through a bridge rectifier, and with the help of external Z-Diode, it is converted into a positive voltage. This voltage is in turn sent to the transformer, which ultimately converts the voltage into a power load. This power load is then sent to the output, which is typically connected to the light source.

Aside from the above, the device employs two main control loops, one controlling the power factor, and the other controlling the switching, which are regulated by two independent control signals. The PFC control loop is a feedback control loop, where the output voltage is compared to a reference voltage, and the feedback signal is used to adjust the magnitude of power inside the switching power supply.

The PWM control loop, on the other hand, is a feedforward control method, in which the power supply is dynamically adjusted according to the output voltage of the switch. This ensures that the device maintains a constant output voltage and current, while minimizing the power losses due to current or voltage variations.

In conclusion, the L6574 is an integrated voltage-controlled switch designed for a wide range of lighting applications. Its dual-output design provides for an ideal solution for controlling light intensity and color temperature, while its low-frequency PFC and PWM power factor control loops help maintain optimal power efficiency and reliability. Thus, the L6574 is sure to become an increasingly popular choice for residential and commercial lighting control in the near future.