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STD PBL Sem 5 - Buck-Linear Voltage Regulator

Project Status: Ongoing

License: Public Domain

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Creation time: 2020-09-07 12:38:51
Update time: 2021-06-14 11:58:04
**Introduction** This is a DC-DC converter module that uses a buck converter (LM2596-ADJ) and a linear regulator (LM317) in cascade in order to obtain a low ripple DC output at fast short circuit response (courtesy of the linear regulator) and a moderate efficiency (courtesy of the buck converter acting as a tracking pre-regulator). An arduino uno, an ADS1115 module and an LCD display are used to display the output voltage, current and power. **Tinkercad link: https://www.tinkercad.com/things/dAnySuxN8RZ (LTspice simulation .asc file available in the attachments section below) (Arduino code available in the attachments section)** **Working** The power supply module is designed to output 1.25V-20V at a maximum current of 250mA. The output of the power supply module is varied using a 10kΩ trimmer. The ‘tracking’ functionality is achieved by modifying the feedback network of the buck converter with the help of a PNP transistor and a TL431 IC. This ensures that the output of the buck converter is always 3V higher than the output of the linear regulator for the entire output voltage range. A 2.2Ω current sense resistor and an NPN transistor are used to set a maximum current limit of 250mA. The output current, in the event of an overload or short circuit, is limited to that value. This ensures that the power supply is not damaged due to overload. Pushbuttons are used for two functionalities: one toggles the output on or off and the other switches the reading on the display from current to power or vice-versa. The pushbuttons send an interrupt to the Arduino, which then runs an ISR to perform the above functionalities. **Result** By combining a switch-mode and linear voltage regulator, it is seen that the power supply module provides a low-noise output at a moderate efficiency. The LCD display shows all important measurements (current, voltage and power) in an easy-to-understand layout that is very convenient for the user. (This project was not fully completed due to the pandemic.) ![Full Load DMM measurements.jpeg](//image.easyeda.com/pullimage/JKNSoRQQrfUClW7dlSQtxklX0VRrdQJJ61EwTvey.jpeg) Short circuit test ![Short Circuit DMM measurements.jpg](//image.easyeda.com/pullimage/6IMQ6Z4UVzSvtBZ7QbWhlAY3Xjp1ax3Pesev47Mu.jpeg) ![PXL_20201129_070737664.jpg](//image.easyeda.com/pullimage/edsIYOjY0poH1ljKA0RJArMAYJblwOajDqABhhVd.jpeg) ![PXL_20201129_070822711.jpg](//image.easyeda.com/pullimage/eFMuy0MDUxzM1eprFrk7FSzxc4EedTkPyCTbKxFt.jpeg) Full load pre-regulator waveform ![Full Load PreRegulator Waveforms.png](//image.easyeda.com/pullimage/ad64laqaB9l2BJnTdLwE5TsqrSuMA2qt556phAz8.png) Short circuit response ![Short Circuit Response.png](//image.easyeda.com/pullimage/bxynyRzKB8HlXFIK27MADOl0QXZcVQizOfDTEY0D.png) Short circuit to normal response ![Short Circuit to Normal Operation.png](//image.easyeda.com/pullimage/EOyxvxsv2cqm6NC22KjGC4kp1Zbrei7FcixjCNAk.png) LTspice simulation ![Screenshot 61.png](//image.easyeda.com/pullimage/55dDF2aRvjaqE8bDMT5085cfyH82VKIU126QRCR2.png) ![Screenshot 63.png](//image.easyeda.com/pullimage/ewDFBIhQTWkF80tSikzCLTFWiNAQXtBbnORJLkV9.png) Output Ripple - Buck converter (top) vs linear regulator (bottom) ![Screenshot 64.png](//image.easyeda.com/pullimage/1pIVrDTY1rLnYhV0rTy8LPdZUzKg03EYUaskib2R.png) Short circuit response ![Screenshot 65.png](//image.easyeda.com/pullimage/1Lw4UszxyP6ilzaefG2GkRHVXvAaNx75TfGJvItN.png) ![Screenshot 66.png](//image.easyeda.com/pullimage/2t2PnSs6BXZ7O8dZdlg3gFm9dKHvR5YhjaeE7uoT.png) TinkerCAD simulation ![Screenshot 146.png](//image.easyeda.com/pullimage/GmS1o9EpHczhwVyoUJQESY8negGNZAuLMuTZPEUA.png) ![Screenshot 147.png](//image.easyeda.com/pullimage/eyTzCJ6B3GL6reipWWaoAq9aZ5s95HclNFsa9CtP.png) ![Screenshot 148.png](//image.easyeda.com/pullimage/Y8JXsgksZcuixCp8qi2xSY0HftFbNbKOizAq1sbp.png)
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ID Name Designator Quantity
1 1N5819 D1 1
2 2N3906 Q3 1
3 Arduino Uno U6 1
4 100n C2,C7,C8 3
5 LM78L05 U5 1
6 ADS1115 Module U8 1
7 Ammeter PB1,PB2 2
8 100n C9,C10 2
9 TL431 U2 1
10 2N3904 Q1 1
11 32V VIN 1
12 LM2596-ADJ U3 1
13 1N4148 D2 1
14 33u L1 1
15 10u C1,C4,C6 3
16 100u C3,C5 2
17 LCD-16X2 (JHD162A) U7 1
18 560R R1,R7 2
19 100R R2 1
20 100k R3,R8 2
21 5.6k R4 1
22 4.7k R9 1
23 2.2R R5 1
24 1k R6,R13,LOAD 3
25 LM317AT U1 1
26 10k RP1 1


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