PWM Controlled Dimmer for Triac and SCR Driver Applications
- Lentark Electronics
- Apr 5, 2023
- 2 min read
Updated: Jun 17
ZCD-28PT835A: PWM Controlled Dimmer and Triac/SCR Driver
ZCD-28PT835A is a triac and reverse-parallel SCR driver module designed for AC power control applications. It supports an 85–285 VAC RMS input range and allows firing control through the duty cycle ratio of the PWM signal applied to the device.
This structure makes the module suitable for digitally controlled dimmer and AC switching applications. Instead of using a purely analog control method, the firing behavior can be adjusted by changing the PWM duty cycle provided by the control system.
Zero-Cross Detection and Signal Monitoring
The device detects the points where the applied AC input signal crosses the zero-potential region. These zero-cross points can be monitored and used as reference information in the control system.
The ZCD-28PT835A is designed to maintain stable detection behavior under practical AC line conditions. It provides high immunity against noise, voltage fluctuations and short interruptions in the input signal. Signal deformations with a duration of up to 1.25 ms do not affect the zero-cross detection output.
Galvanically Isolated Structure
In AC power control applications, isolation is an important part of system reliability and safety. In the ZCD-28PT835A, the AC input, digital input/output section and firing outputs are isolated from each other using galvanic isolators.
This isolation structure helps separate the control side from the AC power side and supports safer integration in systems where digital control circuitry and mains-related switching sections operate together.
Key Features
85–285 VAC RMS input range
PWM-based firing control
Triac and reverse-parallel SCR driver output
Zero-cross detection output
Adjustable ZCD amplitude: 5 V – 18 V
High immunity against noise, voltage fluctuations and short input interruptions
Immunity against signal deformation up to 1.25 ms
Galvanic isolation between AC input, digital input/output section and firing outputs
Conclusion
ZCD-28PT835A provides a practical PWM controlled dimmer structure for triac and SCR-based AC power control applications. With PWM-based firing control, zero-cross detection and galvanically isolated sections, it can be used in systems where digital control and AC switching need to be integrated in a more controlled and reliable way.
