Problem in LM2576 circuit

[shindehari]

Dear all,

I am using a LM2576 (5 Volt) switching regulator IC in my board, earlier it was working well for some time. When i switched on relays either small resistor type inductor is blowing or LM2576 is blowing up. To resolve it i have replaced diode 1N5822, 100uh inductor, LM2576, but still one of the two are blowing up. I have wasted couple of inductors and LM2576. My relay is connected to 24 volt power supply so no supply is going from the LM2576 regulator to the relay. I have tested capacitor also and it is in good condition.

I cant find where is the exact problem. What is the main reason for blow up of inductor or lm2576.

 

[Colin Mitchell]

What load have you got connected to the output of the IC?

 

[Martaine2005]

Have you got a diode across the relay coil?

Martin

 

[shindehari]

Thanks for your attention

I have connected ULN2003, so i hope no need of diode please specify if it requires.

I have connected PIC16F877A, 5- 7 segment LEDs, 3 single LEDs, 5-BC547, 5-PC817 as load to 5 volt power supply.

As per my knowledge resistor type inductor can support around 100mA. I think my load current is more than 500mA. Please help me to resolve this issue.

 

[Martaine2005]

It may be better to upload a schematic of your circuit! with component values..
And save people here from guessing.

Martin

 

[shindehari]

sorry sir,

Please find the attached schematic for my circuit.

Looking forward for your valuable suggetions

 

[eetech00]

How about showing the LM2576 schematic?

 

[Arouse1973]

sorry sir,

Please find the attached schematic for my circuit.

Looking forward for your valuable suggetions

Post the schematic you are having issues with and please highlight the area that is causing you issues.
Adam

 

[Martaine2005]

Is it by any chance U10? The text is not very clear at all.
Also, I am having difficulty seeing how RL1, RL2 and RL3 are connected. What pins do they go to? Are they all parallel connected?

Martin

 

[GPG]

As per my knowledge resistor type inductor can support around 100mA. I think my load current is more than 500mA

This could be your problem.

 

[Harald Kapp]

This could be your problem.

Not only could, almost definitely is.

When used with overcurrent, the inductor saturates and loses inductivity. It behaves as a resistor with comparatively low resistance. You neeed to use an inductor which is rated for at least the max. current that will flow through the inductor. Note that this is more than the average load current but the peak current which is higher!