How to design a smps based battery charger?

[amjadali56]

Dear Amjad Ali,

Can you share schematic of this charger ?

Thank You.
Regards,
Gapoo

Sorry Brov! the charger i shared has some Bugs, please just wait a little for update and fix , I will post scham also...

 

[Gapoo]

we can fix mutually bugs by discussing here too.

 

[Gapoo]

Re: smps based battery charger

What is the part number of the component at E$23 ? In PCB and Parts list only 40V/30A is written.

 

[amjadali56]

Re: smps based battery charger

What is the part number of the component at E$23 ? In PCB and Parts list only 40V/30A is written.

40 volts / 30Amps High Speed Diode.

we can fix mutually bugs by discussing here too.

only if you can redesign the whole thing..

 

[Gapoo]

Re: smps based battery charger

I've no issues in redesigning whole thing. If it is a diode kindly let me know it's part number as it contains three pins used for different purposes.

 

[amjadali56]

Re: smps based battery charger

i used MBR3045PT out of an old computer power supply (35v/ 30A ultra Fast recovery Power Diode)

 

[D.A.(Tony)Stewart]

There are many elements to designing even a "Simple": AC to DC battery charger. These must be fully understood from your research before starting.

1) Safety requirements (Hipot, leakage, grounding , component selection, creapage, surge protection) Agency approval
2) Noise ingress and Egress requirements( Impulse noise, switcher noise, lightning and ESD ) Agency test requirements
3) Efficiency
4) Cost budget
5) Regulation: 3 stage battery profile: Constant current (CC) mode, Constant Voltage (CV1) Mode, Float voltage (CV2) mode (vs Temp.)
6) Reliability,: temperature rise, surge current limit, short circuit protection, over-voltage protection, over temperature protection, temperature compensation
7) Mechanical strength from shock, vibration
8) Connector choices
9) Custom transformer design for turns ratio, losses, HV isolation, lower inter-winding capacitance, SRF, efficiency
10) Manufacturing plan

**broken link removed**

 

[amjadali56]

For reference check it out
(up to 5 Amps/ 14.4V )

trfo = Primary 15+15 Turns , Feed 3 turns/ Secondary 7 Turns.

 

[amjadali56]

Sorry Brov! the charger i shared has some Bugs, please just wait a little for update and fix , I will post scham also...

(UC3842 15 Amps) update and bug fix ver.......

 

[--BawA--]

Can anyone please tell me how to adjust the current for uc3842 based charger? I want to design a single charger which can provide a current from 1amp to 15amp. The current should be adjusted with the help of a pot.

 

[red_alert]

Feed the voltage across the current sense resistor to the IN+ of an opamp then adjust the opamp gain (using a pot) to get ~1V at its output for any specific charger output current (1 - 15A).

The opamp output shoud be connected to the curent sense pin of UC3842.

 

[--BawA--]

Thanks red_alert ,
and how to implement a float charge and overcharge protection in this circuit ?

 

[red_alert]

That's a sample circuit:



You have to read the output voltage (V_OUT) and compare it with an manual adjusted threshold. If the output voltage exced 14.4V (float voltage), the I_SENSE input of UC3842 is forced to V_ZENNER voltage so it becomes active and will cut the output pulse (despite the output current).

Thus you have both voltage and current limiting.

 

[--BawA--]

Red_alert , could you please try to explain the working of 2nd opamp in the circuit?
How the float voltage is set in the schematics you posted?, I mean , when the battery voltage reaches 14.1V and the current drawn by the battery is approx 0.5Amp , the charger should go in float mode and the output voltage should be 13.65.

 

[red_alert]

Without a MCU it's a little bit complicated (complex schematic) to do this.

The circuit above just limit the output voltage at a V_SET level (14.1V, by example) and the output current at a I_SET level (1 .. 15A) simultaneously.

Lead acid batteries have a dynamically changed internal resistance. If you limit the charging voltage to 14.1V, the charging current will be self limited, too.

Thus you could have a charge current of 15A (if that's your adjusted value) as far as the voltage across battery doesn't rise above 14.1V. After that, the current will be automatically reduced (by decreasing the PWM duty cycle) to keep the battery voltage at 14.1V.

Actually, all the battery operations are current controlled. By keeping the voltage constant, the battery will self adapt the charging current.
It is just an impression that one could control the battery voltage. By pumping a higher/lower current, the battery voltage is kept at a specific voltage (state of charge).

By the way, you can't overcharge a battery if the charging voltage is kept at 14.1V.

 

[amjadali56]

Bawa just look and observe at the LM358 current/voltage control section in the pcb if you have eagle. otherwise tell me to convert it to any other possible mean for you.

 

[--BawA--]

Dear Amjad and Red_alert, please explain the detail working of lm358 in the schematics below


i have got this schematics from some other thread.
amjad , is your pcb is same as schematics i have posted? if not , could you please upload the schematics of the layout ,you posted? its very difficult to understand the circuit without schematics.

red_alert , in the above schematics , the lm358 is not connected to the Isense pin of uc3842, can you please explain the complete working of that lm358 section ?
can we not adjust the current in this schematics?

 

[D.A.(Tony)Stewart]

U4A only sense charge current with 0.2V over 0.02Ohm for 10 A limit. R30 controls this 0.2V but the Pot value ratio is too large from the zener.

There is NO full SOC foldback to 13.6V when charge is complete.. This design is unsuitable.

 

[--BawA--]

Sunnyskyguy ,
in the schematics R37 is also used for sensing the current , and its output is fed to ISENSE pin of UC3842 , so why there is a need of current sensing (R19) in output section again?

 

[D.A.(Tony)Stewart]

R37 is only to prevent core saturation. R19 prevents over current to the battery. Meanwhile there is no 3 step regulation as desired.
1) CC 1A
2) CV 14.1
3) FLoat CV 13.2~13.5 temperature dependent.