Tracking 0 ~ ± 15V regulated power supply

btty038

Tracking 0 ~ ± 15V regulated power supply [Copy link]

 

Tracking 0 ~ ± 15V regulated power supply

qwqwqw2088

Comparison of typical positive and negative power supplies

btty038

qwqwqw2088 posted on 2019-2-15 09:20 Comparison of typical positive and negative power supplies

If you see this in the literature, please correct me, discuss and guide my study.

cruelfox

IC2 is also an LM317? This is obviously wrong.

btty038

cruelfox posted on 2019-2-15 09:47 Is IC2 also LM317? This is obviously wrong.

Correction, thank you

maychang

btty038 posted on 2019-2-15 09:54 Correction, thank you

It should be LM337, a negative voltage three-terminal adjustable regulator. The characteristics of LM317 and LM337 are basically symmetrical, only one is used for positive voltage and the other for negative voltage.

btty038

maychang posted on 2019-2-15 11:06 It should be LM337, a negative voltage three-terminal adjustable regulator. The characteristics of LM317 and LM337 are basically symmetrical, only one is used for positive voltage and the other for negative voltage.

I will learn from it

btty038

{:1_107:}{:1_107:}{:1_107:}:victory::victory:

bigbat

Experts, please tell me what a "tracking" power supply is. I don't understand it. I have used LM7815 and LM7915 as positive and negative power supplies. I read the data and it says that the output of LM317 is Vout=1.25V~45V. How come 0~ ± 15V appears in the circuit? How do IC3 and IC4 feedback voltage? I don't understand how RP1 symmetrically adjusts the voltage? Looking forward to the popular science of experts.

btty038

bigbat posted on 2019-2-15 12:48 Can an expert tell me what a "tracking" power supply is? I don't understand it. I have used LM7815 and LM7915 as positive and negative power supplies. I looked at the information and found that LM317...

@chunyang @maychang Let me analyze and popularize it.

maychang

btty038 posted on 2019-2-15 12:58 @chunyang @maychang Let me analyze and popularize it.

IC3 op amp is used for positive output voltage and reference voltage (R3R6 and R7 divide the voltage, and the reference is the voltage across R7) to keep the positive output voltage unchanged. IC4 is used for R9 and R10 divide the voltage (R9 and R10 have equal resistance values) and compare with "ground". The two input terminals of the op amp are "virtually shorted", and its output always tends to make the potential of the two input terminals equal when working linearly, that is, the voltage across R9 and the voltage across R10 are equal. Therefore, the negative output voltage tends to be equal to the positive output voltage, that is, "tracking".

maychang

btty038 Published on 2019-2-15 12:58 @chunyang @maychang Let’s analyze and popularize it

If R9 and R10 are not equal, the negative output voltage will still "track" the positive output voltage, but it will be multiplied by a proportionality coefficient, which is the ratio of R10 to R9.

btty038

maychang posted on 2019-2-15 14:25 IC3 op amp is used for positive output voltage and reference voltage (R3R6 and R7 voltage divider, the reference is the voltage across R7) to keep the positive output voltage unchanged. IC4 is used...

{:1_103:}:handshake

chunyang

The output voltage of 317 and 337 is determined by the potential of its adjustment end. There is only one voltage adjustment potentiometer RP1 in the original poster's figure, which is used to adjust the output voltage of IC1. The output voltage of IC2 is naturally affected by the output voltage of the positive power supply because its adjustment voltage divider circuit is connected between the positive power supply and its own output. This is called "tracking". The tracking rule is related to the value ratio of the voltage divider resistor and the subsequent circuit. The figure should be 1:1 symmetrical output. The reason why the power supply can output 0V is that the reference point takes negative voltage/positive voltage (the latter is for the negative power supply of LM337). When the output of 317 is 0 at the adjustment end potential, it outputs 1.25V. To make it output 0V, the voltage at the adjustment end needs to be -1.25V to "offset" the minimum 1.25V limit. In the figure, the negative voltage of 317 is generated by the D6 circuit and drives the op amp, so that the op amp can output negative voltage. Similarly, the positive voltage of 337 is provided by the D5 circuit. The function of IC3 circuit is to output a stable -1.25V. When IC4 circuit is tracking 1:1, the output should be the same as the absolute value of the potential of the adjustment terminal of 317, but the sign is opposite. However, there is a problem with this part of the circuit. The op amp is connected as an open-loop comparator.

btty038

chunyang posted on 2019-2-15 18:58 The output voltage of 317 and 337 is determined by the potential of its adjustment end. There is only one voltage adjustment potentiometer RP1 in the original poster's figure, which is used to adjust the output voltage of IC1, and...

Thank you for learning from the two masters

PowerAnts

The OP thinks that if one is making a product, which components should one pay special attention to?

埋土书生

maychang published on 2019-2-15 14:25 IC3 op amp is used for positive output voltage and reference voltage (R3R6 and R7 voltage divider, the reference is the voltage across R7) to keep the positive output voltage unchanged. IC4 is used for...

Is the negative power supply of op amp 4 missing a node at the input of ic2? I can't understand the negative power supply loop of ic2 in this circuit.

maychang

Maitu Shusheng published on 2019-2-16 15:51 Is the negative power supply of op amp 4 missing a node at the input end of ic2? I can’t quite understand the negative power supply loop of ic2 in this circuit

“Is the negative power supply of op amp 4 missing a node at the input end of ic2?” No.

zhuyebb

Thank you for sharing