NOW ARCHIVED! Automotive Power Supplies Office Hours

Welcome, everyone, to the Automotive Power Supplies Office Hours!

TI Experts, Wen-Shin Wang, Ben Hopf, and Mahmoud Harmouch are on hand now to answer your questions.

Just hit reply and ask your question now!

What are the critical components in DCDC buck converter and how to place them for EMC?  

Hello, can we post open Innovation topics? 

Here's another question - What are the effects of violating the minimum on-time requirement for DC/DC converters?

Is anyone even on  this forum? 

The critical components are the input capacitor, the catch diode, and the output capacitor.  During switching time there is a sudden current in these components and stray inductance can cause huge L*di/dt voltage spikes.  These components have to be very close to their respective device pins. To minimize these spikes, the grounds of these three components must be connected together with very short traces.  Also, a ground plane is necessary to minimize the stray inductance.

Hi, Andrew,

Thanks for your interest. We are limiting this Office Hours to automotive power supply questions so feel free to post anything in topic area.

cheers,

Aimee

Working at high switching frequency we should think about minimum on time violation. The BUCK feedback is correcting the DC output voltage but not the AC ripple.  If the minimum on time is violated the duty cycle will no longer be constant and the output voltage will have higher AC ripple than expected.

I am interested in creating new advances for T.I.

My questions do involve auto-innovation.

Andrew Corum said:

I am interested in creating new advances for T.I.

My questions do involve auto-innovation.

Please feel free to post your questions and we'll do our best to answer!

Next question: What is the effect of the boost converters’ right half plane zero (RHPZ) in continuous mode?

Okay, can we add multi-cameras to the Auto Black Box?

Record your trip in case something unforeseen happens? 

Plus, auto-photo updates on your car alarm when you are at work. 

Andrew Corum said:

Okay, can we add multi-cameras to the Auto Black Box?

Record your trip in case something unforeseen happens? 

Plus, auto-photo updates on your car alarm when you are at work. 

 

Hi Andrew,

Thanks for the update. These are very interesting ideas and we can pass them on to our Automotive Solutions Marketing Team to see if they see a trend in these.

Regarding adding multi-cameras to the black box system - there is already something similar happening in Asia. It is currently an after-market device, and it is a recorder that the driver can install on their front windshield.

It will record everything that is happening in front of the car (and to the sides of the car in upgraded systems) and can be replayed in the case of something unforseen happening (i.e. accident). Since it is an after-market device, the next step may be to integrate into the black box system as suggested.

Thanks and Best Regards,

Wen-Shin Wang

Nicole Bernard said:

Next question: What is the effect of the boost converters’ right half plane zero (RHPZ) in continuous mode?

For higher load current and to avoid high peak current, the boost converter should work in continuous mode. Once it is in continuous mode a right half plane zero RHPZ is created. The RHPZ is +20db/decade and -90degree phase. The RHPZ frequency is VIN/(2*PI*Iin*L) where VIN is the input voltage, PI = 3.14, Iin is the input current and L is the inductance value. The RHPZ can not be compensated. The only solution is to design the circuit bandwidth lower than RHPZ frequency. So the direct negative impact is low bandwidth. The RHPZ frequency can be increased by lowering the inductance value and here the compromise is with the inductor peak current.

Wang, suggest that the device look like a rear view mirror.   

This should open the door for a partnership with OnStar.  

We are about to wrap up our first Automotive Office Hours on Power Supplies. We have time for one more question.

This thread will also be archived. Thanks!

cheers,

Aimee

Can the EN pin of TPS57140-Q1 (and other Alcor devices) accept a voltage greater than the listed abs max of 5V?

Morgan Field said:

Can the EN pin of TPS57140-Q1 (and other Alcor devices) accept a voltage greater than the listed abs max of 5V?

Andrew Corum said:

Wang, suggest that the device look like a rear view mirror.   

This should open the door for a partnership with OnStar.  

Hi Andrew,

Thanks for the suggestion. It's something we can take into consideration.

Best Regards,

Wen-Shin Wang