How to Read DC Bus voltage with Simulink

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How to Read DC Bus voltage with Simulink

NXP Employee
NXP Employee

In the User Guide for the HVP-MC3PH board I found the following;

4.6 Current inrush circuit

The inrush circuit is used during the powering of highvoltage circuits. It is based on the (NTC) Thermistor RT1 and the shorting relay K1. Before powering the power circuits, the DCbus capacitors are usually discharged. To avoid a huge current pulse when the power is connected, the RT1 limits the current to a reasonable value. This protects from melting the fuse, input filter, rectifier and the output capacitors from current shock. Immediately after the output capacitors are charged, the relay must short RT1 to avoid overheating. This should be done by the user once the DCbus voltage achieves 80% of nominal value, usually in the time range 0.3 – 3 seconds after power is applied.

Now I would like to measure the DC bus voltage and switch the relay output at 80%, whereby RT1 is bridged.

For that the voltage could read with an analog input in a Simulink model and if 80% are reached the digital output PTC13 (where the relay is connected) would switch on.

Unfortunately, I could not figure out where the DC bus voltage is measured.

Which sample index I have to configure in the Simulink ADC Block ?

Which value I have to configure in a compare block, so that it matches 80% DC Bus voltage ?

Or should I connect a switch externally at J2 (e.g. RxD_EXT), read it by a digital input block and manually operate it after 0.3-3 seconds?

A software-controlled solution would be more elegant ...

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NXP Employee
NXP Employee

Hi lethuer‌,

I do not have the board in my possession - but from the board user manual the VDC should be connected on pin B4 which in turns should be ADC index/result 12


Let me know if that works.

Best regards,

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Contributor V

Hi dumitru-daniel.popa‌,

why do you think it is Index 12 ?

I am using the KV46F150M Controller. The Pins you can see in the following picture.

U_dcb is connected to Pin 11 and ADCA_CH1, so i would configure Index 1 in the ADC Read Block...

Is that correct ?

U_dcb am Controller KV46.PNG

What do you think about this solution ?

The step Block has a step time of 3 seconds.

If the step time is reached or the value from the dc bus voltage is higher or equal than 3.3V * 80% = 2.64 (which is read by the adc read block index 1 ??) the digital Output will be set to high. Pin PTC13 is connected to the relay, you can see here:

Relay am Controller KV46.PNG

Simulink DC Bus Spannung einlesen und RT1 überbrücken.PNG

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