MC33063A boost circuit, burning IC and electrolytic capacitor? With pictures, help!

yhye2world

MC33063A boost circuit, burning IC and electrolytic capacitor? With pictures, help! [Copy link]

As shown in Figure 1, two circuits designed using MC33063A:

The above is the step-down circuit for DC12V to DC5V;
the below is the step-up circuit for DC12V to DC24V.

Attached Figure 2 is a layout diagram;
Attached Figure 3 is a physical diagram;

During the test, about half of the samples had the following faults:
about 30 seconds after power-on, a strange smell appeared, and about 30 seconds later, the aluminum electrolytic capacitor E13 swelled and became hot to the touch; then, U8 began to smoke.

May I ask what is the cause of this?

Thank you so much!

Figure 1

Figure 2

Figure 3

maychang

"About half of the samples will have the following failure"

Then, most likely there is something wrong with your electrolytic capacitor E13 or inductor L6.

qwqwqw2088

Are you sure that the unburned half of the circuit is all good?

Are there any problems with the welding assembly connections?

yhye2world

maychang posted on 2019-12-3 14:21 "About half of the samples will have the following faults." Then, most likely your electrolytic capacitor E13 or inductor L6 has a problem.

Thank you teacher maychang!

I'll check

yhye2world

qwqwqw2088 posted on 2019-12-3 14:51 Have you confirmed that the half of the circuit that is not burned is good? Are there any problems with the welding assembly connection?

Thank you moderator!

The step-down circuit is good and outputs 4.98V.

No problems were found in welding, assembly and connection