IR2103S not outputting any signal

[Tonci]

Hello,

we have a design with the IR2103S gate driver. The driver has a supply voltage of 12V and two 3.3V 20 kHz PWM signals on HLIN and NLIN pins. Unfortunately, none of the ICs we tested output any signal for the MOSFETs. Sometimes it happens that MOSFET output voltage increases very slowly with time. What might be causing such strange behaviour? Is there a reference design/layout/BOM we can use?

Additionally, why is there a discrepancy in common wire between the datasheet and the simulation model?

Thank you so much in advance.

[yifei_y]

Hello,

Can you share your schematic and waveforms for HIN, LIN, HO, LO with us to review?

The source of high side and drain of low side must be connected together as follows, you can try the schematic of the online simulation circuit

Regards,

YF

[Tonci]

Hello,

thank you for replying. I am attaching the schematic and the HIN and LIN signals. The HO and LO signals are 0V, with some couple MHz ripple, usually to about 1V peak to peak amplitude.

[yifei_y]

Hello,

Please note HIN and LIN are in phase and out of phase respectively

The correct timing should be

HIN high, LIN high --> HO high, LO low

HIN low, LIN low --> HO low, LO high

Please refer to the result of simulation circuit

Regrads,

YF

[Tonci]

Thank you for pointing that out. Phase A now works perfectly, while phases B and C are behaving strangely.

The difference is in the HO output, so I assume there must be an issue with the bootstapping circuit. The LO signals are the same for all three phases. I have attached LO, HO and VS signals for all three phases. What do you think would cause such behaviour? Is the problem in bootstrapping capacitors or in diodes?

Thanks a lot.

[yifei_y · Accepted solution]

We have this AN for bootstrap components' values calculation.

Phases B/C have normal LO outputs but VS are abnormal, please check if MOSFETs are broken.

[Tonci]

I am not sure why the first reply got removed.

Nonetheless, phase A and B now work great. Phase C still has weird behaviour. I have changed all the components to new and removed the MOSFETs, so I hope that limits the possibilty of faulty components.

Below are the HO signals for phase A (that works) and phase C (that does not work yet). Additionally, there seems to be no oscillation on the bootstrap capacitor on phase C, even tho the component is the same.

[yifei_y]

I saw your inquiry in another thread.

Did you change IR2103S? Phase C may have a broken driver IC, you can try with a new one.

[Tonci]

Yes, I have. IC in both cases produce the same result. I wonder if the problem could lie in the layout, however, it is identical to the other two phases.

Thanks so much for helping me out.

[Tonci]

Just wanted to let you know that all phases are now working. The problem was in the high-side MOSFET. Apparently three of them that I was changing among were broken. 😄

Thanks again,

Toni

[Tonci]

Hi,

is it safe to connect the HIN and NLIN pins together and drive them with one PWM? As I understood, the IC has and internal cross-conduction prevention logic, so I assume it regulates the deadtime automatically?

[yifei_y]

Yes HIN and NLIN can be connected together to same PWM signal.