Power managment for this circuit supplying power to my pump load

[core7916]

hello,
i am working on a load, by giving continous 12v power supply and current consumed by the load is max of 1.5 A.
there is a resistor between load and supply. power consumption (heat dissipation) is more at the resistor. i am finding difficulty while designing in pcb board. bcuz size of the resistor will increase. i want to avoid it. is there any alternate approach.

Thank you.

 

[Baluncore]

there is a resistor between load and supply. power consumption (heat dissipation) is more at the resistor. i am finding difficulty while designing in pcb board. bcuz size of the resistor will increase. i want to avoid it.

What is the value of that resistor?
Why is there a resistor in the supply connection?
Can you give us a circuit diagram?

 

[core7916]

What is the value of that resistor?
Why is there a resistor in the supply connection?
Can you give us a circuit diagram?

Thank you for your reply.
Sir. For preventing overcurrent or short circuit in the load i am isolating dc converter with lm338 voltage regulator in which I can set current limit using resistor. Since load current is 1.5 A . I have to use high wastage resistor. Problem is size of high wattage is more. This is the main problem while designing pcb.
So what to do ? Either I have to reduce the resistor size or use alternate approach in which I can prevent overcurrent or short circuit.

 

[Baluncore]

Use a 12 volt switching voltage regulator, that has built in current limiting. That will have very low power when overcurrent, since it will drop output voltage to limit current.
This regulates adjustable voltage, with an adjustable maximum current.
https://www.ebay.com.au/itm/284729600905

Or make a current regulator from a BJT with base-emitter voltage, not a precision 1.2 volt reference. Compared to LM338, expect in a BJT limiter, to dissipate 25% of power.

What is the 12 volts regulator?
What is the load?
Circuit diagram?

 

[core7916]

Use a 12 volt switching voltage regulator, that has built in current limiting. That will have very low power when overcurrent, since it will drop output voltage to limit current.
This regulates adjustable voltage, with an adjustable maximum current.
https://www.ebay.com.au/itm/284729600905

Or make a current regulator from a BJT with base-emitter voltage, not a precision 1.2 volt reference. Compared to LM338, expect in a BJT limiter, to dissipate 25% of power.

What is the 12 volts regulator?
What is the load?
Circuit diagram?

Load is small pump which has excitation of 12 v and can be controlled speed by pwm.
Sir. Since I am new to thease concepts. Please suggest any documents or circuits .

 

[Baluncore]

Since I am new to these concepts. Please suggest any documents or circuits.

There are still too many possibilities to work out what you will need.

Please provide a link to the pump, make and model, or supplier.

Does the power come from a 12 volt battery, an AC mains powered supply, or from a solar panel?

 

[core7916]

There are still too many possibilities to work out what you will need.

Please provide a link to the pump, make and model, or supplier.

Does the power come from a 12 volt battery, an AC mains powered supply, or from a solar panel?

Pump is actually a coolant pump of Ford car engine.
I am supplying 12 volts from a dc dc converter.

 

[Baluncore]

Please provide a link to the pump, make and model, or supplier.

Pump is actually a coolant pump of Ford car engine.

Pump part number or link?
I would be surprised if an automotive coolant pump would run on 1.5 A. If it was PWM, then it may sometimes average 1.5 amp.
Do you PWM the pump, if so how are you doing it?

What is the DC-DC converter input voltage, output voltage, and rated output current?
To protect the DC-DC converter, fit a fuse to the pump circuit. You might use a self-resetting breaker. That will eliminate the need for a current limiter and short-circuit protection.

 

[core7916]

Pump part number or link?
I would be surprised if an automotive coolant pump would run on 1.5 A. If it was PWM, then it may sometimes average 1.5 amp.
Do you PWM the pump, if so how are you doing it?

What is the DC-DC converter input voltage, output voltage, and rated output current?
To protect the DC-DC converter, fit a fuse to the pump circuit. You might use a self-resetting breaker. That will eliminate the need for a current limiter and short-circuit protection.

Sir. While I am testing pump in stand alone mode it took around 1.3 A at Max speed. (12 v input)
Input to dc dc converter is 18-36 V.
My problem is if there is a overcurrent of fault happens to load, it will cause the loading problem. To avoid this I have to design a circuit or isolation. Or any alternate approach other than using fuse.

 

[berkeman]

My problem is if there is a overcurrent of fault happens to load, it will cause the loading problem. To avoid this I have to design a circuit or isolation. Or any alternate approach other than using fuse.

As in several of your previous threads, you seem to not have the experience yet to avoid designing dangerous circuits. Is there a standard pump driver module available for this pump? If so, you should probably buy it instead of trying to design a circuit that may catch fire under single-fault conditions...

 

[Rive]

There is ready-made DIY component class for this kind of task
You may look for something like 'PWM DC motor controller 12V' on any supplier of electronic gadgets


You will need a safe box, wiring and a fuse or two.
Please get somebody to build it for you, or at least: who will supervise and mentor you during the build.

Not particularly difficult task and fortunately it's low voltage, but given the apparent lack of experience and since liquids will be involved ...

 

[DaveE]

Most DC-DC converters (the good ones) already have overcurrent protection. For distribution systems without that, like a big battery, for example, load fault isolation is normally done with fuses. In a more sensitive design you can look into electronic circuit breakers. Be careful to use parts specified for the proper DC voltage and DC current.

So, what's wrong with just using a fuse?

 

[Baluncore]

Sir. While I am testing pump in stand alone mode it took around 1.3 A at Max speed. (12 v input)

Please define "stand alone mode".
Did the pump have water in it ?
What flow rate and head?

 

[core7916]

Please define "stand alone mode".
Did the pump have water in it ?
What flow rate and head?

Pump was filled with water. And I didn't measured the flow rate. But I can see the flow rate change difference while changing the pwm.

 

[core7916]

As in several of your previous threads, you seem to not have the experience yet to avoid designing dangerous circuits. Is there a standard pump driver module available for this pump? If so, you should probably buy it instead of trying to design a circuit that may catch fire under single-fault conditions...

I tried to search for ic which will do the whole job. But I didn't got any.

 

[Baluncore]

This regulates adjustable voltage, with an adjustable maximum current.
https://www.ebay.com.au/itm/284729600905

Replace your DC-DC converter with this AU$6.47 unit. Your higher DC voltage in at one end, 12 volts will come out the other. They share the ground connection.
First, adjust the output voltage to 12 volts with one potentiometer. Then adjust the maximum current limit with the other potentiometer. It is short circuit protected.
Fit your PWM after this converter, before the pump.

 

[Tom.G]

Replace your DC-DC converter with this AU$6.47 unit. Your higher DC voltage in at one end, 12 volts will come out the other. They share the ground connection.

Hmm... A PWM converter fed by another PWM converter can be problematic.

They sometimes interact with each other and end up with neither working as intended.

If that occurs, some extra filtering between the two may help, either LC or RC; or even a small series resistor.

Cheers,
Tom

 

[berkeman]

Hmm... A PWM converter fed by another PWM converter can be problematic.

Oops, I missed that. Two switching converters in series can definitely be problematic. I've done a lot of work on that in past designs.

 

[Baluncore]

Hmm... A PWM converter fed by another PWM converter can be problematic.

They sometimes interact with each other and end up with neither working as intended.

The converter is a regulated power supply, it has a low-pass filter with a big capacitor across the low impedance output, with a low ripple voltage.

The PWM is an on/off current switch, that is insensitive to ripple, driving a high impedance inductive load.

Fear, uncertainty and doubt, are not required here.

 

[berkeman]

The converter is a regulated power supply, it has a low-pass filter with a big capacitor across the low impedance output, with a low ripple voltage.

The PWM is an on/off current switch, that is insensitive to ripple, driving a high impedance inductive load.

Fear, uncertainty and doubt, are not required here.

As I alluded to in my reply above, I've had issues with two switching power supply circuits in series in the past.

I have spent a lot of time mapping out frequency-amplitude domain sensitivity regions of operation for such systems. The issue is that the traditional stability analysis for a switching power supply circuit assumes a DC input voltage (or at the worst an input voltage that varies at line AC frequency). There are definitely regions of instability when the input voltage has ripple anywhere near the switching frequency of the 2nd circuit or it's harmonics.

 

[berkeman]

BTW, this is probably way too advanced for this OP's thread, so we can just drop it or take the discussion to PMs. Based on the previous threads by @core7916 they probably have no clue what we are talking about now.

 

[Baluncore]

Fear, uncertainty and doubt, are not required here.

The OP is already fearful of short circuits, and overcurrent.

BTW, this is probably way too advanced for this OP's thread, ...

We need to counter problem expansion, by beginning progress towards a low-cost, fear-free solution, for the OP.