ZeroKool
Newbie level 4
Hello ALL,
I am new here on this forum. I hope someone can help me design a Half-Bridge Converter. I want to design a Half-Bridge DC-DC converter with an input voltage varies from 350-400Vdc and output of
3-35Vdc@10A max. with adjustable output voltage. I would like the SMPS to have current overload protection (short circuit, over current), overvoltage protection, and reverse output voltage protection, soft start (pefer not to use NTC), emergency shut down incase something bad happen due to external source, and any other protection I may have missed...maybe I am asking a little too much of the protection issues (just preparing, incase, I decide to build a higher voltage and current in the future)...LOL . Can anyone give me a reference schematic so I can make the require changes/addition/modify to meet my requirements?
I have compose a list of concerns and issues, and hope that someone could also help me address them.
1- Can anyone help with selecting an operating switching frequency? should I run it at 100KHz? I would like it to run at 200KHz so I can use a smaller transformer, does anyone have any objection to that or see any drawback (emi, fast components availablility)?
2- Can anyone help with recommending a Hi and Lo side FETs (commonly use and easy to find parts)?
3- Can anyone help with recommending a IC controller? I am thinking about using LM3524/SG3524/SG3525. I am have conflicting answer when it come to operating Half-Bridge in Current Mode, can it be done using current transformer on the primary side (for short circuit, overload, and components protections, etc)?
4- I have seen in many cases (circuit samples) that some half-bridge converters use a serie capacitor is insert between the transformer primary and split capacitor to balance the volt-second integral of each switching transistor in order to avoid core saturation (due to DC walking/shifting) and other time they are not used it. Does anyone know why it is use in some half-bridge converters while other half-bridge does not? How do I know when it should be use and when it shouldn't be use? and sometime a low resistor is added in serie with the coupling capacitor.
5- Which method is the best way to sense the current for short circuit or over current?
6- Any oscillation concern I should worry about (fault FETs turn ON or OFF)? Maybe placing a series RC snubber across each FETS and output rectification diodes/sync-Fets? Place a filtering capacitor across
the transformer's secondary?
7- How to determine the split capacitor's value to hold the charge at 1/2*Vin to deliver the power requirement?
Thank you,
ZeroKool
I am new here on this forum. I hope someone can help me design a Half-Bridge Converter. I want to design a Half-Bridge DC-DC converter with an input voltage varies from 350-400Vdc and output of
3-35Vdc@10A max. with adjustable output voltage. I would like the SMPS to have current overload protection (short circuit, over current), overvoltage protection, and reverse output voltage protection, soft start (pefer not to use NTC), emergency shut down incase something bad happen due to external source, and any other protection I may have missed...maybe I am asking a little too much of the protection issues (just preparing, incase, I decide to build a higher voltage and current in the future)...LOL . Can anyone give me a reference schematic so I can make the require changes/addition/modify to meet my requirements?
I have compose a list of concerns and issues, and hope that someone could also help me address them.
1- Can anyone help with selecting an operating switching frequency? should I run it at 100KHz? I would like it to run at 200KHz so I can use a smaller transformer, does anyone have any objection to that or see any drawback (emi, fast components availablility)?
2- Can anyone help with recommending a Hi and Lo side FETs (commonly use and easy to find parts)?
3- Can anyone help with recommending a IC controller? I am thinking about using LM3524/SG3524/SG3525. I am have conflicting answer when it come to operating Half-Bridge in Current Mode, can it be done using current transformer on the primary side (for short circuit, overload, and components protections, etc)?
4- I have seen in many cases (circuit samples) that some half-bridge converters use a serie capacitor is insert between the transformer primary and split capacitor to balance the volt-second integral of each switching transistor in order to avoid core saturation (due to DC walking/shifting) and other time they are not used it. Does anyone know why it is use in some half-bridge converters while other half-bridge does not? How do I know when it should be use and when it shouldn't be use? and sometime a low resistor is added in serie with the coupling capacitor.
5- Which method is the best way to sense the current for short circuit or over current?
6- Any oscillation concern I should worry about (fault FETs turn ON or OFF)? Maybe placing a series RC snubber across each FETS and output rectification diodes/sync-Fets? Place a filtering capacitor across
the transformer's secondary?
7- How to determine the split capacitor's value to hold the charge at 1/2*Vin to deliver the power requirement?
Thank you,
ZeroKool