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I have the following schematic:

enter image description here the switch (S) is not the right one but i hope it will do the purpose here.
It controls electro-screwdriver using 48V. When I switch it off slowly, the voltage regulator blows (IC1).

Datasheet: https://www.diodes.com/assets/Datasheets/ZXTR2112FQ.pdf

I added the diode (D2), it helps but not 100%. Is there any solution for this problem without the need to change the schematic?

Would adding a resistor as voltage drop instead of 0ohm (R1) help and which value?

The +48V is the power supply The 48V: enter image description here Taken after J3 (pin1) and befor R1

And the output of the regulator: enter image description here Taken after (IC1) pin2 after both C9 and C3.

The current consumption is 2mA.

The switching off moment: enter image description here

Taken from the Gate of (Q1) pin4
The green line is the gate voltage (pin4)
The orange line is the source voltage (pins 1,2,3) to load.

The switching on moment: enter image description here

Taken from the Gate of (Q1) pin4
The green Line is the gate voltage
The orange line is the source voltage (to load) Both ocsillograms were taken and the e-screwdriver (load) were connected.

Hamo
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  • How much current is used on the 12 V? How about reverse voltage when 48 V disappears but 12 V is sill present? – winny Jan 25 '24 at 12:01
  • When I switch it off slowly can you elaborate? What does "slow switch off" mean in your system? Is there also a fast/quick switch off? – Rohat Kılıç Jan 25 '24 at 12:17
  • According to the datasheet of the Mosfet-driver it draw only 225 micro A. https://www.mouser.de/datasheet/2/609/ltc7004-3125761.pdf

    The regulator can supply about 15mA. I mean with slowly switching off slowly pressing the switch on/off bottun. At that moment it flow a large amount of current and that make it blows, or so i think.

     – Hamo Jan 25 '24 at 12:25
  • Slowly switching mechanical button = contact bounce. Please hook up your oscilloscope to input and output of the regulator and post oscillograms. Please measure your actual current consumption. – winny Jan 25 '24 at 12:41
  • What switch? There is none in the diagram. What is +48V? How long wires? – Tim Williams Jan 25 '24 at 12:58
  • @ Tim Williams:

    this switch: https://m2bswitches.eu/producto/rl-15y/. +48V is the power supply

     – Hamo Jan 25 '24 at 14:46
  • Capture the switching off moment. – winny Jan 25 '24 at 21:41
  • @winny, i did it, the switching on and switching off moment. – Hamo Jan 26 '24 at 06:26
  • Why is there a sawtooth between 9-14 V before you switch on? – winny Jan 26 '24 at 08:42
  • This is because of boost diode D1 and capcacitor C1 i would say. – Hamo Jan 26 '24 at 09:19
  • I don't understand. If the +48 V is switched off, the entire circuit is unpowered and all other voltages should be zero. – winny Jan 26 '24 at 09:25
  • Yes but in this oszigram the 12V (output of regulator is present) and the Mosfet driver ist supplied but the suplly for the pin which in turn switchs the Mosfet is off. Of course when i switch both off then there is no voltage: 0V. In the previous comment i tried to explain why the gate voltage is sawtooth. – Hamo Jan 26 '24 at 09:40
  • This is becoming close to being closed as unclear. Please draw and switch as a switch in your schematic. Draw all voltage sources, even external ones as voltage sources and name relevant nodes. Explain each oscillogram in what setup they were taken from, referring to node and component names. Explain each trace in each oscillogram. – winny Jan 26 '24 at 11:30
  • @ winny i drew the main voltage and the switch too in the schematic and i tried to explain all the ocsillograms. – Hamo Jan 29 '24 at 07:00
  • Are you injecting both 48 and 12 V into your circuit? – winny Jan 29 '24 at 09:42
  • @ winny No, i am injecting only 48V into the circuit. The 12V is generated from injected 48V by the (IC1) regolator to supply the Mosfet-Driver (U1). – Hamo Jan 29 '24 at 10:04
  • Then how is 12 V saw tooth available at the time of 48 V turn-on? – winny Jan 29 '24 at 10:14
  • In ocsillogram is available because i injected the 12V just for test puprose, but now it is not available so when 48V is off there is no 12V too. – Hamo Jan 29 '24 at 10:19

0 Answers0