adnan012
Advanced Member level 1
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Hi,
I am evaluating the performance of a DC/AC inverter. The inverter specs are as follows
Input:
40-48VDC Lithium ion cell power bank.
Output:
110VAC 60Hz @ 1600 Watts
Invert topology:
Push Pull DC/DC stage. There are two MOSFETS at each leg on primary side. The voltage is boosted to 230VDC. After Battery +iver terminal there is an electrolytic capacitor. After this there is large inductor (on a EE ferrite core ). After the inductor there are 4 ceramic type capacitors with a total capacitance of 20uF and this point is connected to power push-pull transformer. Push pull transformer is designed by using PQ40/40 type core.
Full Wave rectifier at output stage.
H-Bridge for converting DC voltage to pure sine wave.
There is a fly-back power supply which provide 3 isolated power sources.
The primary and secondary side sides re isolated.
The PWM controller is TL494.
Switching frequency is 50KHz.
There is no voltage or current feed-back to the TL494. The duty cycle is fixed and is about 40% -45% for each primary side MOSFETS.
On secondary side, MCU sense the output current via shunt resistor and it performs over load protection. Sine wave sampling frequency is 20 KHz.
There are 3 separate heat sinks. One for primary side MOSFETS, one is for full-wave diode rectifier and the 3rd one is for h-bridge.
I have tested the inverter in a proper EMC lab. There are frequency peaks from 30 to 70 MHz range. The standard is FCC PART 15B 3M. The peaks have more than 6 to 10dBuV/m above the limit.
I have to fix the emi issues. I want to know what type of equipment is required like spectrum analyzer and some special probes for debugging and fixing the issues.
There was a 7MHz ringing at the drain of MOSFETS during turn-off period. Its peak was almost 30Vpp. I have fixed it. There is no other issue regarding stability of the inverter.
I need help to solve this issue.
Regards
I am evaluating the performance of a DC/AC inverter. The inverter specs are as follows
Input:
40-48VDC Lithium ion cell power bank.
Output:
110VAC 60Hz @ 1600 Watts
Invert topology:
Push Pull DC/DC stage. There are two MOSFETS at each leg on primary side. The voltage is boosted to 230VDC. After Battery +iver terminal there is an electrolytic capacitor. After this there is large inductor (on a EE ferrite core ). After the inductor there are 4 ceramic type capacitors with a total capacitance of 20uF and this point is connected to power push-pull transformer. Push pull transformer is designed by using PQ40/40 type core.
Full Wave rectifier at output stage.
H-Bridge for converting DC voltage to pure sine wave.
There is a fly-back power supply which provide 3 isolated power sources.
The primary and secondary side sides re isolated.
The PWM controller is TL494.
Switching frequency is 50KHz.
There is no voltage or current feed-back to the TL494. The duty cycle is fixed and is about 40% -45% for each primary side MOSFETS.
On secondary side, MCU sense the output current via shunt resistor and it performs over load protection. Sine wave sampling frequency is 20 KHz.
There are 3 separate heat sinks. One for primary side MOSFETS, one is for full-wave diode rectifier and the 3rd one is for h-bridge.
I have tested the inverter in a proper EMC lab. There are frequency peaks from 30 to 70 MHz range. The standard is FCC PART 15B 3M. The peaks have more than 6 to 10dBuV/m above the limit.
I have to fix the emi issues. I want to know what type of equipment is required like spectrum analyzer and some special probes for debugging and fixing the issues.
There was a 7MHz ringing at the drain of MOSFETS during turn-off period. Its peak was almost 30Vpp. I have fixed it. There is no other issue regarding stability of the inverter.
I need help to solve this issue.
Regards