Hello
in our application we need to precisely control a 230VAC resistive heater coil load (air cooled with a large air flow) from a 230VAC/50Hz 1 phase circuit with a max power of 3.3kW (16A). The 230VAC input side must be power factor corrected and should have less than 5% THDi. There is no isolation requirement for the load.
The resistive heater coil load has to be regulated from 0-100% in about 1% increments (7 bits 0-127 are fine). The regulation normally ramps over a couple of seconds but can also jump at 50Hz The output of the controling MCU is a proportional PWM 0-100% signal (it could also control a resistor network or write the value through I2C/SPI).
Simple circuits lilke triacs can't be used as phase cutting produces to many harmonics. Also half wave switching can't be used as the AC load must be continuous with each cycle. The load is to be used behind inverters (e.g. solar and ups).
Research has shown a number of approaches:
diode full bridge rectifier with PFC and variable DC/DC converter
fully controlled igbt full bridge with AC chopping (5+ kHz) and duty cycle control
fully controlled igbt half / diode half bridge with AC chopping agin
and possibly others
The possible tropologies are quite a few. What I'm looking for is a suitable cost, parts and space efficient topology with a (single) control IC that drives the IGBTs as well as manages their duty cycle and PFC based on the MCUs proportional load output. The efficiency is secondary as the switching losses can be damped into the airflow together with the heat load.
Most designs and evaluation modules are intended for a fixed voltage (CV) output instead of a variable voltage with constant current (CC with a constant resistive load). The ideal IC / topology could operate in constant power mode, however that would be only icing on the cake for a small premium.
Any pointers and discussions for suitable topologies, TI power controller ICs and reference designs is greatly appreciated.
