Author Topic: Heating issues with solar charging circuit  (Read 1035 times)

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Offline aakash deyTopic starter

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Heating issues with solar charging circuit
« on: February 07, 2019, 02:01:56 pm »
I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the calculation it should be 2A). But, the input diode D1, Input capacitor C1, MOSFET Q1, diodes D3 and D4, Inductor L1 are heating too much during charging. What could be the reason of heating ? Any design problem or other?
 

Offline nsrmagazin

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Re: Heating issues with solar charging circuit
« Reply #1 on: February 08, 2019, 02:44:01 am »
D4 should not be heating, your output has a very low resistance and D4 drains a lot of current to ground, maybe around "0.4..0.6ADC". Whats the frequency at which your driver IC controls the MOSFet, it seems as if the MOSFet is on for too long.
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Offline aakash deyTopic starter

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Re: Heating issues with solar charging circuit
« Reply #2 on: February 08, 2019, 05:47:20 am »
As per as datasheet the switching frequency of DRV pin  of cn3722 is 300KHz. And I am using AO3401 MosFET. Is the MosFET has some issue in this frequency?
 

Offline nsrmagazin

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Re: Heating issues with solar charging circuit
« Reply #3 on: February 10, 2019, 02:17:41 pm »
Can be I have to check the datasheet and I don't have time at the moment. Check the datasheet and measure with an osciloscope if possible? Also check with a multimeter or osciloscope the voltage after the MOS.
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Offline Kasper

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Re: Heating issues with solar charging circuit
« Reply #4 on: February 10, 2019, 05:32:26 pm »
Have a close look at PCB layout considerations in the datasheet.  Specially the parts about grounding. It can be challenging to satisfy all the considerations but if you look at some dev kits, you might get some good ideas.

Try measuring voltage between battery ground and input ground with a scope, that might highlight one of the problems, too much resistance between bat ground and input ground.

Per figure 4 kelvin sensing of charge current: R14 layout could be improved by making it more similar to the image. You want to measure voltage across resistor, not across resistor + a bit of track.


 


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