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I fear, the circuit lacks control on output voltage and load current. Please try to check application notes based on MC3525.Hi! The attached file is a schematic of 50KHz SMPS power supply which uses 325 VDC (after rectification of Mains 240 V). The required current is approx 15 Amperes. Please give comment if any modification in the circuit is required.![]()
The modified schematic is attached in which both AC mains & secondary sided are separated by two different isolation symbols. the question is that the 0.1 ohms/10W resistor are sufficient to drive the transistor ( about 0.7v) or its value may be increased?
The 12V is derived from a separate small isolation transformer? please point out that the 0.1 ohms/10W resistor are sufficient to drive the transistor ( about 0.7v) or its value may be increased?
I am attaching a modified schematic. perhaps the non -inv input can be held at 2.5V and the inv-input needs a voltage input from Vref which can be switched by the transistor of opto-isolator.you can use 2 nos of 0.1 ohm resistors( to make it 0.5 ohm) and for 15 amps it would develop .75 V
the wattage needed is 15*15*.05=11.25. So using 10 watt 0.1 ohms 2 nos would be safe enough.
Finally whether it would limit at 15 amps or 10 amps , or higher depends on the voltage needed for the transistor (opto isolator) to switch.
Later if needed, you may use a potentiometer of say 100ohms across the current sense and feed only a part of the drop to the transistor and it would help effective control of the current.
How ever i have my doubts on ETD44 core -- whether it could deliver 15*16= 240 watts ( say 300 watts including the system efficiency).
Try out better core with higher capacity.
It is fine that you want to shift to 3842. don't claim it on the criticism by othersAfter receiving many criticism in the design, I have changed the design by using UC3842 Current-Mode PWM Controller chip. The data sheet is available with various manufacturer, while one page from Semiconductors - Integrated Circuits - Electrical Components is shown in the attachment. The schematic is then modified by me to fulfill my requirements. So, please point out if any further change is required.
Both schematic (Original & modified are in the same attachment)