Type: Posts; User: treez

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  1. Replies

    Closed: Re: Protecting SMPS against mains transients.

    Thanks, presumably thats because the combination of the AC filter section and the TVS's ensures the downstream SMPS circuitry sees no more than ~600V (ie not the 1200v of let-through)?
  2. Replies

    Closed: Re: Protecting SMPS against mains transients.

    Thankyou...we have [1.8uF film cap plus 200nF] behind a diode (its for the 10W flyback and the diode is so the Power factor is not detrmiented) And there is 130nF oif ceramic caps after the bridge...
  3. Closed: To which standards must we conform for our electronics/electrical product?

    My company has developed a way of removing body and facial hair for cosmetic reasons. It involves high frequency flashing (~1KHz) of high intensity light into the skin. The skin is flashed...
  4. Replies

    Closed: Re: SRF of filter inductors in offline SMPS

    Thanks, the 100pF caps were placed across diff mode inductors...i was assured by the engineer that it was for moving peaks on the scan to get the scan passing overall
  5. Replies

    Closed: SRF of filter inductors in offline SMPS

    I have seen quite a few offline SMPS schematics with 100pF or so capacitors across the diff mode filter inductors. This is said to offer the opportunity to shift peaks in the EMC scan to...
  6. Closed: Dimming the MP2489 right down to zero (Buck LED driver)

    We wish to analog dim this chip down to 25% output, and then we obviously have to PWM dim to further get the leds dimmer from there. I trust that it is possible to pwm dim the chip with a 0.3v...
  7. Replies

    Closed: Protecting SMPS against mains transients.

    As can be seen, this LSP05240 Mains Surge module lets through up to 1100V of ‘residual’ voltage.
    Obviously, the surge module has to go upstream of the AC mains filter in the SMPS. As such, would you...
  8. Closed: Re: CCM boost PFC with reverse recovery management

    I attended an interview and they briefly showed a schem of a 650W Boost PFC. Just downstream of the Diode, there was a gate controlled device, with a symbol something like a SCR……its gate was...
  9. Closed: Type one compensator...why is everybody giving it a phase of -90 degreees

    Surely a type one compensator phase vs frequency Bode plot should always be drawn with -270 degrees phase?
    I mean, -180degrees for the inverting opamp...then -90 degrees for the capacitor in the...
  10. Replies

    Closed: Re: Integrated planar transformer

    I did one like that but it was very low was because my PCB was connected to a 50khz power bus and had to slowly charge a battery from it...the mech eng guys fitted up the core halves...
  11. Closed: SMPS feedback compensation..origin pole is "pole at origin"?

    Hi 4 , equation 8 of the above doesnt make sense....because "fp0" is zero has to be zero Hertz, because its a pole at the origin?
  12. Replies

    Closed: Re: Half bridge SMPS xformer turns calculation

    To design a half bridge transformer, first design a virtual buck converter with your vout. Decide what is your max duty cycle (say 0.7).
    So you then design a buck with whatever vin gives your vout...
  13. Closed: SMPS feedback loop parameters...."Excess phase" is king?

    I am reading page 205 of “power supply cookbook” by Marty Brown, 2nd ed.

    It says that there are three main parameters in SMPS stability…
    1..Gain margin
    2…Phase margin
    3…Excess phase...
  14. Replies

    Closed: Re: Well regulated mains to large cities

    Thanks Klaus, especially for your great help on this subject some time ago aswell.
    I wonder when we have people charging electric cars all over the place we are going to see mains voltages...
  15. Closed: Re: CCM boost PFC with reverse recovery management

    Thanks, at one of the worlds major TV design/manufacturers, they were using a ferrite bead in the place where i show a drain_inductor....(they werent using the freewheeling diode with it).
  16. Replies

    Closed: Well regulated mains to large cities

    How is the mains so stable in large cities like London?....surely it is because there are thousands of micro generators all over London, with regulating tap changers on their...
  17. Replies

    Closed: Re: Buck Converter distortion

    Yes, when the diode goes off, the diode voltage suddenly collapses from abotu 0.7v to zero, and its klind oif liek a step input, and the buick inductor then rings in the loop comprising the output...
  18. Closed: Re: SMPS PFC+LLC/Flyback 24V 100W low THD cool thermals reference design?

    or you could do a simple BCM Boost PFC....followed by Innoswitch syncronous rectified flyback on the output.
  19. Closed: Re: Flyback SMPS power MOSFET getting hot? uc3843 pwm converter

    2v is too low for a fet to turn on properly.
    What is your vin.
    What is the gate series resistor value.
    Can you show scoep shot of gate voltage on no load.
    Can you show scope shot of source sense...
  20. Closed: CCM boost PFC with reverse recovery management

    There is a small inductor in the drain of the fet of this boost converter (attached). It massively reduces the reverse recovery spike that goes through the fet at switch on.
    Why don’t CCM PFC boost...
  21. Closed: [moved] Switch mode power supply interview question and response...bluffing?

    At an interview today, the engineer told me that Voltage mode controlled SMPS’s need slope compensation to be added when the duty cycle goes >0.5………he said that this slope compensation would take...
  22. Replies

    Closed: MCP6001 input voltage near rail (3v3)

    The MCP6001 offers "rail to rail input and output".....but if the vin goes above 3.1v, then it latchs up to the 3.3v rail. Do you know where in the datasheet this is predicted?
    We are using it...
  23. Replies

    Closed: Re: Earth leakage current in offline smps

    Thanks, sorry i thought you were going to say ....
    "For an SMPS the Earth current is the unwanted = leakage current, plus the capacitive current." ?
  24. Replies

    Closed: Re: Adding an offset voltage to a signal

    Thanks, Precision around +/-0.05v
    vbus/300 is made from a potential divider fed to a opamp buffer.
    Load impednace >10Meg
  25. Replies

    Closed: Adding an offset voltage to a signal

    As in the attached schematic, we wish to add a 1.2V offset to the signal “HSIN”.
    The circuit does it but needs two opamps and a negative supply. Is their not a lower component count way of doing...
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