pulse width modulated voltage controller for solar panels

[twister]

https://www.linear.com/product/LM129?utm_source=supplyFrame&utm_medium=SEP&partnerName=DSA

I found a circuit that I think might work good, with a few modifications for a controller. I have a few questions about this circuit. Thanks in advance to whoever helps me.
1. Is there any advantage to using a positive and negative power supplies?

2. How can this circuit be changed to a single supply voltage using a 324 op amp?

3. I don't exactly understand how the ramp is created. Does it have anything to do with the LM129?
https://www.datasheetarchive.com/voltage+reference+IC+LM129-datasheet.html

4. Can I use an ordinary zener or does it have to be that special one?

5. I plan to substitute a 10K pot for LM135 to monitor the batteries voltage. Will that work? And also use a mosfet instead of the bipolar. The heat element will be substituted by batteries.

 

[alec_t]

1) Not all opamps have a common mode input including ground when operated from a single-polarity supply, so using dual polarity supplies enables both inputs to be at ground potential if necessary.
2) A PWM circuit using a 324 and single supply is possible, but the 324 will have characteristics (e.g. bandwidth) different from those of the LF347. So the operating frequency may need to be different.
3) The ramp is generated by A2, which is acting as an integrator. Re the role of the LM129, read the description of Fig 1.
4) It depends what accuracy you need. An ordinary zener may well do, but won't give such accurate control as a precision reference voltage source.
5) Can't say about the 10k, without knowing the precise circuit you will be using. BTW, why do you want to switch batteries on and off with the PWM signal?

 

[colin55]

What are you trying to do?

 

[twister]

1) Not all opamps have a common mode input including ground when operated from a single-polarity supply, so using dual polarity supplies enables both inputs to be at ground potential if necessary.
I didn't know that. I have only worked with 324s. The dual polarity is confusing to me. Ha

2) A PWM circuit using a 324 and single supply is possible, but the 324 will have characteristics (e.g. bandwidth) different from those of the LF347. So the operating frequency may need to be different.
I think I want a frequency of around 10, unless you know of a reason for a different freq.


3) The ramp is generated by A2, which is acting as an integrator. Re the role of the LM129, read the description of Fig 1.
Thanks for that. I think I'm beginning to understand that circuit now. Does LM 129 act as a constant current source?


4) It depends what accuracy you need. An ordinary zener may well do, but won't give such accurate control as a precision reference voltage source.
I have some ordinary zeners in various voltages. I probably don't need a super precision circuit.



5) Can't say about the 10k, without knowing the precise circuit you will be using. BTW, why do you want to switch batteries on and off with the PWM signal?

I built a circuit that would charge the batteries with a constant voltage of 13.8, however it creates a lot of heat when the batteries get up to a full charge, because the pass mosfets have to drop about 6 volts. I have already blown some transistors because of the heat. I would have to use a larger heat sink or install a fan. With the pulse width modulation, I'm hoping that there won't be much heat created. I hope to be able to modulate the pass transistors from 0 to full on when the batteries are very low.
I will try to draw a schematic to show how I think it could work. Maybe you can visulize this. The heating element will be replaced by my batteries. The pass transistors will be hooked to the negative of the batteries to the drain. The source will be hooked to the negative of the solar panel. The positive of the solar panel will be hooked to the batteries.
The 10K pot hooks from the positive of the batteries to ground, with the wiper to the inverting input of the op amp that controls the pulse width. The non inverting pin is hooked to a zener diode of 6V. This is how the one that I built works now, but only at a constant voltage.
What I'm not sure of is if I can convert that circuit to a single voltage source.

Thanks very much for your answers.

 

[twister]

What are you trying to do?

Thanks for your help.
I want to build a pulse width modulated charger, because the one I built before creates a lot of heat. For example. The batteries are fully charged and I'm using 10 amps of current. The solar panels are at their max, at 22 volts. 22-14=8, 8X10=80 watts to be disipated as heat.
That circuit that I found seems like it would be almost perfect with the changes that I mentioned to alec. What I'm not sure of, is changing to a single voltage source. It is already difficult working with two different voltages. I hope to not have to build a negative voltage supply for the op amps.

 

[twister]

Thanks much for your help. I think I have answered my own questions today. I have been on the computer all day. I think that if I just bias the non inverting inputs to half of the supply voltage it will work. I plan to breadboard it tomorrow. If it doesn't work I'll have more questions.
thanks colin and alec

 

[alec_t]

Does LM 129 act as a constant current source?

It's a constant voltage source. It will only pass a constant current if the voltage applied to it via the series resistor is also constant (in which case the LM129 would be redundant).