MC33063A: write simulation but bad signals

Andreas Hummel

Prodigy 40 points

Part Number: MC33063A

Hello,

I simulatet a stepup converter.

I have already set up the circuit and received metrologically similar / same signals

But I think there is something going wrong because the signals look bad.

At first the simulation shematic

Now the meassured signals:

I cant find there a fix frequenzy, more some swinging signals.

In application normaly we have constant current of 50 to 100mA and some Peak of 21A für 1,2µs when the IGBTs are switching. They swithing whith 4, 8 or 16kHz.

for calculation:

worst case at 16kHz 62,5µs/1,2µs * 21A = ~400mA

400 +50 mA =450mA

whith an output of 16V, an input of 12V and a minimal sw-freq. 55kHz I've calculate:

Ton/Toff	0,60
Ton+Toff	1,82E-05	s
Toff	1,13E-05	s
Ton	6,83E-06	s
Ct	2,73E-10	F
Ipk	1,44	A
Rsc	0,208	Ω
Lmin	4,74E-05	H
Cout	2,77E-04	F

So I hope you can helb me.

If you would like to give me your mail adress I can send the Simulation-Model

over 5 years ago

0 Jasper Li over 5 years ago

TI__Mastermind 46905 points

Hi Andreas,

could you help to attachment the model in the post? thanks!

and I would need some days to check the model.

0 Andreas Hummel over 5 years ago in reply to Jasper Li

Prodigy 40 points

Hi Jasper,

sorry I dont't saw the option to add a attachment.

I've updatet the component value to our aktuell hardware setup.

Also I meassured yesterday the load current at 8kHz and 16kHz IGBT switching. For the IGBT-driver powersupply we use a IR2085s with 130kHz. see below.

The following picture shows the meassure at our hardware

1. just a load about 80-100mA

2. the load 80-100mA plus the switching load

8kHz IGBT switching (in the middle ~300mA

16kHz IGBT switching (in the middle ~500mA)

now the simulation

MC33063A-Q1_TRANS_BoostStartup_12to15_currently-setup.TSC

0 Jasper Li over 5 years ago in reply to Andreas Hummel

TI__Mastermind 46905 points

Hi Andreas,

i think there are some problems in the model. these problem causes the device to switch at closed 1MHz when the inductor current is 1A.

the waveform in the bench test seem to be normal, approximately 50KHz frequency from the waveform. did you see a issue in your real circuit?

one more question, why did you add external NPN if the inductor current is limited to only 1A.

0 Jasper Li over 5 years ago in reply to Jasper Li

TI__Mastermind 46905 points

Hi Andreas,

I closed the post as I thought you had solved the issue. if not, just reply below.

we will also modify the mode, but it would require not a short time because of the limited resource.

Power management

Power management forum

MC33063A: write simulation but bad signals