WEBENCH® Tools/TPS61088: slow circuit simulation and unexpected results

Shiromini Satkunarajah

Part Number: TPS61088

Tool/software: WEBENCH® Design Tools

Hi,

I downloaded the circuit for TPS61088 from WEBENCH designer to TINA TI and it works perfectly fine. I expanded the circuit with more components (2 BJTs, 2 capacitors and a few resistors) and now it is takes hours to run 10s simulation. It doesn't give the expected results either. We have tested the circuit in real so we know what the current through the load and voltage across the load is meant to be. I always choose the transient analysis and set it to zero initial values. Is the issue due to the Analysis Parameters?

Many thanks,

Shiromini

over 7 years ago

0 Gavin Jin over 7 years ago

TI__Intellectual 1010 points

Hi Shiromini,

Could you please share your simulation circuit? We may repeat your simulation in TINA to check what the issue is.

thanks

Gavin

0 Shiromini Satkunarajah over 7 years ago in reply to Gavin Jin

Intellectual 320 points

MBR230LSFT1G.LIB

BDV64B.LIB

Circuit.tsc

0 Helen chen over 7 years ago in reply to Shiromini Satkunarajah

TI__Mastermind 40080 points

Thanks, could you please also attach the sch in pdf ? (We rarelly use the TI TINA now and I need to install the TI TINA before start the study)

0 Shiromini Satkunarajah over 7 years ago in reply to Helen chen

Intellectual 320 points

0 Helen chen over 7 years ago in reply to Shiromini Satkunarajah

TI__Mastermind 40080 points

Thanks! I'll check it!

0 Jasper Li over 7 years ago

TI__Mastermind 46905 points

i do the quick simulation (several ms) without finding problem. could you post the waveform you observed to show your issue?
you can just use a DC source to replace the TPS61088, this can greatly reduce the simulation time. As there is a 39ohm and 68mF filter before the additional circuit, the ripple of TPS61088 should not impact the performance of the issue you expanded.

0 Shiromini Satkunarajah over 7 years ago in reply to Jasper Li

Intellectual 320 points

Thank you for your response and I have tried replacing TPS61088 with a battery before. Please see the image below. Wouldn't replacing the boost converter circuit with a battery affect the current going to the attached circuit? The purpose of the circuit is to get 5A flow through the load for 10ms while the voltage across is at least 5.5V. Clearly this is not happening and the complementary pair transistors are not switched on.

0 Jasper Li over 7 years ago in reply to Shiromini Satkunarajah

TI__Mastermind 46905 points

do you have a application note about the operating principle of the circuit? i don't fully understand how it start switching, and how to limit the current through the load?

0 Shiromini Satkunarajah over 7 years ago in reply to Jasper Li

Intellectual 320 points

I am new to my job and I am justifying a work done by an intern before me since he designed and tested the circuit.

Below is what I understand about the circuit.

The Zener diode will only allow current to flow when the capacitor (C1) voltage is equal to the sum of the Zener voltage, Voltage across resistor (R1) which allows sufficient current to the base of the NPN, and Saturation voltage across the Base and Emitter of the NPN.

A Schottky diode is positioned next to the positive pole of the battery to prevent a situation where the capacitor discharges into the battery due to battery failure.

The R5 resistor was specified to ensure that the correct current is supplied to the base of the NPN from the collector of the PNP.

The NPN was specified so that it could sustain the current from the base of the PNP and the current through the R3 resistor.

Capacitor Cn is used to minimize the noise in the circuit.

Resistor R4 is in place to increase the charge resistance, thereby increasing the delay until sufficient capacitor voltage is reached.

The “ignitor” is subject to a voltage of 5.5 V (6.1 A) for a period of 29.5 ms which is a sizeable safety margin from the bear minimum of 5 A for a period of 10 ms.

The transistors are Sziklai pair (complementary Darlington).

0 Jasper Li over 7 years ago in reply to Shiromini Satkunarajah

TI__Mastermind 46905 points

are you sure the direction of the BDV64 is correction. the emitter of the PNP should be connected to the high voltage side?

0 Shiromini Satkunarajah over 7 years ago in reply to Jasper Li

Intellectual 320 points

Thank you Jasper Li. You are correct I needed to mirror the PNP and rotate to get emitter connected to the high voltage. It is giving the desired simulation results now. However, when I get both circuits (the circuit above and the voltage regulator circuit) together and simulate I am getting "Convergence problem. Check the analysis parameter!" error message. Could you kindly advice me what changes I need to make?

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WEBENCH® Tools/TPS61088: slow circuit simulation and unexpected results