• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 63 subscribers
  • Views 1056 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Line under voltage and Over voltage protection circuit-Ref no SLUA753-Aug2015

S Ramakrishnan
Prodigy 100 points
Other Parts Discussed in Thread: TPS92314A, TLC27L4

Dear Mr.Sanjay Dixit/Bharat Agrawal, Please refer to your application note cited above. We liked the concept and wired a pcb following the schematic assuming the VDD supply to the Quad Op amp( we used TLC27L4AIDR) is from 12V(VR1). However the Peak rectifier does not not work. ie.the DC output does not vary with the input AC mains. We are looking for 90V low cut and 100V reconnect and 310V upper cut and 300V reconnect. Please suggest suitable changes in circuit components for the above range and also share some waveforms and voltage s around the peak rectifier at different mains input voltages to help us trouble shoot the problem. Please also enlighten the role of the 23.5K resistor at the out put of peak rectifier. We plan to use this circuit with TPS92314A.

Regards,

S.Ramakrishnan

  • 0
    TI__Mastermind 25500 points

    Hello Mr. Ramakrishnan,

    I believe this should be posted in the Amplifiers forum if you need help with the TLC27L4 circuits. I would move it for you but I do not have admin capabilities and I haven't found out who to contact yet. But I don't want you waiting around for a response from the wrong forum.

    Thanks.

  • 0
    TI__Mastermind 28655 points
    Hello,

    Are you just looking at the output of the AC input to DC level amplifier? What this does is C4 discharges via R8 unless the (+) input is higher than the (-), then it charges via R7 and the rail voltage minus the diode drop. This will be somewhat like a peak detector but filters so as not to false trip on noise. R7, the 23.5K resistor allows for fast charging but also allows a certain amount of noise above the threshold to prevent false peak charging.

    Looking at the circuit it should vary it's output with a variance in input voltage. I simulated it and it changes with respect in input voltage.

    Thanks,
  • 0 in reply to Irwin Nederbragt
    Prodigy 100 points

    Thanks for your valuable inputs Irwin. We will take another look at the wired board to trace any assembly error. Does your simulation throw up some answers for the following:

    1.  DC voltage across C4 at 100V/50HZ, 200V/50HZ & 300V/50HZ

    This data would be helpful in debugging the circuit assembly. We have given 12V supply to the  IC though this is not shown in the application note.

    Also  the designer has selected 23.5K resistor for R7. Does this indicate it is critical to stick to this value for proper performance?we used 24K resistor for R7 in the proto

    Look forward to your reply!

    Regards

  • 0 in reply to S Ramakrishnan
    TI__Mastermind 28655 points

    Hello,

    It shows a little above 1.0 volt at 100V, 2.0 volt at 200V and 2.9 volt at 300V.  24 Kohm is fine it can vary quite a bit.  I don't know which op-amp you are using but it has to have common mode range to the (-) rail, in the case the circuit common.  The diode also needs to be in the output otherwise it is not a peak detector.

    Thanks,

  • 0 in reply to Irwin Nederbragt
    Prodigy 100 points

    Thanks Irwin. You have been a great help! We are using the TI quad op amp Part no TLC27L4AIDT.. Trust this Part is ok  vis a vis the common mode requirement you mentioned. The supply is 12V drawn through a Drop resistor from the input Bulk capacitor and a 12V zener duly bypassed with a 4.7MFD ceramic cap.I would love to hear from you some tips to trouble shoot the Peak rectifier part of the circuit. The diode(IN4148) is connected at the output of op amp before the 24K resistor. Do we have to use a Shotkey  diode in the place of IN4148? the input AC freq is 100HZ.

    Regards,

    S.Ramakrishnan

  • 0 in reply to S Ramakrishnan
    TI__Mastermind 28655 points

    Hello,

    That part should be fine since it's the same as the app note.  If you have it configured the same way I would measure pin 2, pin 3 and pin 1 to see what they look like (with rectified AC applied to the resistor divider.  Measure pin 4 and pin 11 as well to make sure the IC has power and is tied to ground.  Note that this circuit is not isolated so care must be used in measuring signals, the circuit ground is not the test equipment ground.

    Pin 2 should look like a DC level with a small sawtooth waveform from the charging and discharging of the 4.7 uF capacitor

    Pin 3 should look like a reduced rectified AC waveform

    Pin 1 should be a square wave with very low duty cycle at 120 Hz or possibly even just pulses that don't even get to the op-amp rail duty to slew rate limitations.  It may have alternating smaller and larger pulses depending on what the rectified AC is or possibly even skipping half resulting in a 60 Hz pulse train.  This portion is trying to make pin 2 DC value near the peak value of pin 3.

    This can be tested without high voltage if the upper resistor in the resistor divider is lowered down.  Applying DC at lower voltage should also show this circuit working.

    The 1N4148 diode is a good choice for this.  Sounds like you're using all the same parts as on the application note.

    Thanks,