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  1. cabraham

    Young people replacing old workers in Electrical Engineering?

    I think the biggest problem is that there is no long term plan. Engrs in their last 5 yrs. before retirement should be working with under 50 aged engrs to groom them. When one retires, another w/ 15 or more years left should pick up the mentor role. But today's corporations are so "this...
  2. cabraham

    Out of college and dismal about job.

    First jobs cannot offer you intense development activity because you are too new & raw. Also, design/development is difficult with only a BS. The BS degree is a great degree for sure. It is the biggest & toughest step. But the BS is pretty much all about basics & requirements. Applying...
  3. cabraham

    Why do engineers encourage people to become engineers

    I don't encourage or discourage anyone to choose engineering. I encourage all to pursue the field in line with their aptitudes, and discourage all from entering a field simply because it's what they want, or the pay is good. Every field requires certain innate abilities that most people don't...
  4. cabraham

    would you discourage your child to take up engineering in college?

    Your child should pursue the subject they are talented in. It's all about aptitude. I've lost EE jobs, but not for long. I always get hired quickly. I stay at a job for a long time, but with today's economy, even a good worker can get hit. But the good ones bounce back. The ones always...
  5. cabraham

    Engineering Outsourcing

    It's hard to say. Engineering graduation rates are higher in India and other countries. I overhear people here in the US saying that they discourage their young from majoring in engineering because their job can be offshored. But that is a self-fulfilling prophecy. If US students avoid engr...
  6. cabraham

    Electrical Engineering being hit hard by the economic downturn

    <quote> Funny the article failed to mention the IEEE's complicity in the fabled 'engineer shortage', which has apparently evaporated overnight.The IEEE, and its analogs, are not really organizations for engineers; their mission has more to do with ensuring an oversupply of engineers, so as to...
  7. cabraham

    Any differences between the BSEE and BEEE?

    To "cksh", you seem to have the BEEE degree mixed up with the BSEET degree. The "2+2" curriculum is for the BSEET degree. The BEEE is a 4-4.5 year curriculum. Then an MS is the next step w/o the need for any make-up courses. A BEEE is slightly stronger than a BSEE, but the difference is...
  8. cabraham

    Any differences between the BSEE and BEEE?

    It was a very good curriculum then, & I understand that it still is. Only now there is no MS program, so you'll have to go elsewhere for the masters degree. But the basic education is great. Claude
  9. cabraham

    Any differences between the BSEE and BEEE?

    I went to YSU for the BEEE & MSEE. The BEEE is a little more course work than a BSEE. In the 70's, it was about 12-15 hrs. of more courses, when the quarter schedule was in place. On the trimester system, it would be 8-10 additional hours. So, the BEEE is slightly stronger than the BSEE, but...
  10. cabraham

    Why Gold? It's useless!!

    Gold is used in producing semiconductors. Diamonds are useful for cutting due to their extreme hardness. Gold, diamonds, and other precious metals, such as silver, and gems, such as sapphires, have practical use in industry. In semiconductors, gold doping can reduce minority carrier lifetime...
  11. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    No problem. I'm glad we agree and that your closed loop tests affirm the correct RHPZ frequency value of (R*(1-D)^2)/L, for the boost topology. We did go off on a tangent but covered some interesting stuff. This stuff is good to go over and review. None of us really know as much as we think...
  12. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    Hysteretic mode does not use an error amp. It is a "bang-bang" type of controller. It does not have an oscillator, and it runs at variable frequency. The lack of error amp & servo loop means that no freq comp is needed. It is simple, and stability is never a concern because it is always...
  13. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    Off the cuff here is my abbreviated answer. I don't have enough time to do an exhaustive analysis. With a boost cvtr in CCM driving LED lamps, the output is a constant current driver. The cap across the LEDs is sometimes not used. But during the on time, the inductor is disconnected from the...
  14. cabraham

    Slope compensation for current mode SMPS

    It sounds like you're using the 28C43 family of current mode control IC. The 1.0 volt shut off is a maximum value intended for fault conditions. During normal operation, the PWM is turned off when the sensed current signal Is, attains the value of the control signal Vc. At the start of the...
  15. cabraham

    Slope compensation for current mode SMPS

    An added slope equal to the inductor current downward slope is excessive, which overdamps the system. With a duty factor of 0.69, the optimum added ramp slope is around 0.75 of the inductor current downslope. Visit the Ray Ridley site, "Switching Power Magazine" and download his app notes. He...
  16. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    In a boost PFC there is no RHPZ. For a PFC the controlled quantity is not the output voltage, but rather the input current. As soon as the duty factor command is increased, the input current immediately increases. Thee is no "wrong way" phenomena in the PFC case. Of course, the transfer...
  17. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    Lloyd's cookbook is indeed "scriptures" in my mind as well. Few individuals, if any, have contributed more to understanding the SMPS than Lloyd. He starts out the paragraph (pg 21 per above post) stating that both boost and buck-boost converters have a RHPZ when the inductor current is in...
  18. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    In dcm the rhpz for all practical purposes does not exist. It is located above the bandwidth of the error amp and has negligible influence. In ccm it falls in the range of the error amp bandwidth and it is generally what limits said bw. Scroll up a few posts and download my hand written...
  19. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    The rhpz freq is not changed by slope comp. The slope comp, SC, is mixed with the sensed current signal, Isns, and the PWM is terminated when the sum of SC + Isns equals the error signal. The rhpz freq is determined by the time required for the inductor current to ratchet to its new level. SC...
  20. cabraham

    Formula for Right Half Plane Zero in a Boost Converter

    Sorry, but I omitted the "L" in the denominator of the boost computation. At the bottom the left hand equation is missing the "L" in the denominator, but the L was re-inserted into the final answer. The final answer is correct, but one step along the way had an error. I updated the mistake...

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