Hi, I am using TEA1792, a synchronous rectifier controller, as the controller for MOSFET in a three-phase rectifier. The simplified schematic is as illustrated:
The schematic of the two right-most TEA1792s is shown below:
The MOSFETs are used here to substitute for the traditional diodes. The conceived benefit of the replacement is to reduce the voltage drop through the diode and thus the power loss.
However, the results of the actual tests are confusing.
1. If C32 and C39 are removed, Q2 will never be switched on, and Q1 will be switched on simetimes.
2. If C32 and C39 are connected, Q2 and Q1 will be switched on most of the time. But during a small portion of time(see 2.8 ms), Q2 and Q1 are not switched on, although the voltage drop is -0.8V.
3. I want to see if a constant direct current will force U14 to switch Q2 on. So I did a test. First, C39 was removed. Second, direct current(10A) from GND to phase C was conducted. Then I noticed that Q2 was not switched on. The voltage of phase C was around -0.8V. This means that although TEA1792 senses that the voltage drop is below -220mV, it still cannot switch Q2 on.
Other parameters are posted here: the frequency of the three-phase voltages is 400Hz. The voltage of the load is 40V.
Could you help me figure out whether TEA1792 is suitable for three-phase rectifier or direct current? Thanks a lot.
