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LM25037EVAL: Using the LM25037 in an H-bridge converter

amine cheriti
Prodigy 135 points
Part Number: LM25037EVAL
Other Parts Discussed in Thread: LM25037

Hi guys,

I'm thinking about using the LM25037QMT to design a boost converter that would take a 12V input from my battery and convert it to a 24V output. 

I want to use a topology of an H bridge so that I can have regenerative properties at the same time .My load being a motor ,sometimes it ends up being a generator so I also want my circuit to be able to charge my battery when this happens. 

I'm thinking about using the LM25037EVAL as a reference design to design my converter, however there are certain things from this eval board I'm having a hard time understanding. Could you guys give me a little help with that?

Thanks a lot 

  • There is a part of the circuit I don't understand. It is the part containing the components C20,D5&L3. I've put a picture below. What is the purpose of this circuitry? From my little knowledge in converter, these components would not be required for a typical flyback.
  • I'd like to use this eval board to do my first tests. What would I have to modify on the board so that it properly operates with a 12VDC input and give me a 24VDC output instead of the actual output of 5V?
  • Are they any further considerations I should take when using the LM25037QMT as my controller of my h-bridge converter ?

Thanks a lot guys 

  • 0
    TI__Mastermind 28015 points

    Hi Amine,

    I copy/pasted your inquiries below with my answers attached to each:

    • There is a part of the circuit I don't understand. It is the part containing the components C20,D5&L3. I've put a picture below. What is the purpose of this circuitry? From my little knowledge in converter, these components would not be required for a typical flyback.
      • The components you've highlighted are part of the start-up bias circuitry (called a "bootstrap winding"). For a flyback there is no output inductor (L3 is not present in a flyback) but you will see this additional winding as part of the flyback transformer design. In either case (push-pull output inductor winding or flyback transformer winding), the function is the same. The PWM controller initially starts-up from a resistor(s) connected to the DC input voltage. Once the controller begins switching, the VCC bias winding builds up voltage to take over the role of supplying bias voltage to VCC. A VCC capacitor is correctly sized to hold up VCC during the hand-off between start-up from the DC input and the time it takes for the VCC winding voltage to take over. 
    • I'd like to use this eval board to do my first tests. What would I have to modify on the board so that it properly operates with a 12VDC input and give me a 24VDC output instead of the actual output of 5V?
      • You have to work through the data sheet to set up the controller properly to meet your new design requirements. Parts of the LM25037 that may need to change: start-up, current sense resistor, current sense filter, compensation, feedback resistor divider regulation set point. Things that may need to change in your power stage: transformer turn ratio, output inductor, input/output capacitor banks, check MOSFET VI rating against your new requirements. TI Power Stage Designer can help you with the power stage portion of the design.
    • Are they any further considerations I should take when using the LM25037QMT as my controller of my h-bridge converter?
      • H-bridge is usually referring to a full-bridge but LM25037 is a half-bridge controller. If the function of your converter is to drive a motor (constant voltage) but also charge a battery (constant current), you need to research CC/CV battery chargers. Also your 12V input battery voltage has a wider min/max range - make sure you design a converter that can operate over this min/max range and use the full range as inputs to TI Power Stage Designer so you can determine/optimize your power stage design.

    Thanks for connecting through E2E.

    Regards,

    Steve M