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MOSFET (Si/SiC) Forum Discussions

asrikrishnagovi
Level 3
5 questions asked First like given 25 sign-ins
Level 3

Hello, I am looking for reference designs and methods to protect the fan circuit and its interface with my MCU, specifically the FAN PWM and FAN RPM. I've come across the INFINEON 22KW Reference design earlier and noticed the circuit in the isolator sheet, of the "Infineon-Schematics_22kW_Inverter_Power_Board-PCBDesignData-v01_00-EN.pdf, page 16". Looking for an explanation and design guide for the following schematic design. Thanks and Regards. 

asrikrishnagovi_0-1657695032867.png

 

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AZIZ_HASSAN
Moderator
Moderator 100 sign-ins 50 solutions authored 10 likes received
Moderator

Hi,

Thank you for the clarification. Please find the answers below.

1) The functionality of Q10 is in case you don't have a internal switch in motor for PWM control, there you can use this configuration to give PWM via a external switch to vary the voltage (from 0 to 100%).

2) The purpose of C136 is to filter out the high frequency components across the V_IO_SELV isolated supply. Remember one point here that the PWM is directly coming from MCU not from gate driver so you need one voltage source at the gate terminal to give adequate gate voltage as per switch requirement. 

3) You can directly connect PWM of MCU to motor terminals provided the a switch is already there in motor. If not then configure it as explained in point 1 and in schematics to vary the voltage.

4) If you don't  want to give PWM( means you want to operate the motor at fixed supply) , you can remove the circuit and make the direct ground as return path. Another way is to give 100% PWM to FET(Q10) and use it as fixed voltage but there will be unnecessary power loss at Q10.

I hope you understood the the explanation.

BR,

AZIZ HASSAN

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AZIZ_HASSAN
Moderator
Moderator 100 sign-ins 50 solutions authored 10 likes received
Moderator

Hi,

Thank you posting at Infineon community. 

May I know whether you need explanation for the portion of schematic shared by you or for complete page 16 schematics?

BR,

AZIZ HASSAN

 

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asrikrishnagovi
Level 3
5 questions asked First like given 25 sign-ins
Level 3

Hello, just the portion attached as an image will suffice.  Thanks and Regards

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AZIZ_HASSAN
Moderator
Moderator 100 sign-ins 50 solutions authored 10 likes received
Moderator

Hi,

Following is the explanation for the image attached.

Generally, the DC- motors will have 4 terminals i.e. power(PWR), PWM, Speed(RPM/SPD) and ground. The image attached shows the configuration that how to logically generate and interface  the terminal parameters from MCU to motor.

1)FAN1 PWR-PWR pin of motor requires a voltage source which is generated by the high side power switch (ITS4040D). Whenever, you give a enable signal to IN pin of this power switch, a internal switch gets turn ON(whose drain is connected to Vs which is nothing but motor voltage required) , the drain voltage comes to source (output pin) after Vds drop and the motor terminal gets supply. The OUT1 and OUT2 are connected in parallel to increase the current capability. In our case, Vs= V24_SELV.

2) To control the motor lets say speed control, you need one  PWM  to vary your speed. For that one FAN1  PWM is generated from MCU(master controller) and given to PWM terminal. If you give high PWM, the another winding terminal will be connected to ground and if you give low PWM , it will be connected to other level based upon the internal architecture of the motor.

3) FAN1 SPD is for the motor speed feedback which will be given directly to MCU and based upon which the PWM will be generated, in case you want to do speed control.

4) The 4th pin is ground and I hope it doesn't need any explanation.

Note:

FAN1 DIS is for enabling or disabling  the supply required for the motor.

FAN ST is the status pin for both the motors (internally, one OR gate is present)

To understand more, please read the attachment as well which shows  you controller section schematics. Also I recommend to  read the user manual to know more.

https://www.infineon.com/dgdl/Infineon-Schematics_22kW_Inverter_Interfaces-PCBDesignData-v01_00-EN.p...

I hope this will solve your purpose.

BR,

AZIZ HASSAN 

 

 

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asrikrishnagovi
Level 3
5 questions asked First like given 25 sign-ins
Level 3

Hello,

 

So in regards to the FAN_PWM, could you please explain the functionality of the Q10 Transistor, along with the capacitor C136, and what happens if one connects the MCU PWM port for the fan directly to the fan's PWM port through a connector? Thanks and Regards

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AZIZ_HASSAN
Moderator
Moderator 100 sign-ins 50 solutions authored 10 likes received
Moderator

Hi,

Sorry for delay. Sure you can connect, but it depends on the  load also. Can you please tell the motor load so that I can help you more on this.

BR,

AZIZ HASSAN

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asrikrishnagovi
Level 3
5 questions asked First like given 25 sign-ins
Level 3

We're using a BLDC Fan, with a 12V Supply Pin, and a PWM Pin to control the speed of the Motor, RPM Feedback and Ground. The supply current is about 0.18A. The PWM signal is not to vary the voltage level to the fan supply ( Fixed at 12 V).  The PWM signal is not given to the 12V Supply of the fan. 

Consider the following fan as an example: https://noctua.at/en/nf-a14-industrialppc-2000-ip67-pwm/specification

We're primarily trying to prevent: 1. Protection against accidental shorting 12V line and PWM Line. 2. Protection against any parasitics in the line leaking back to the MCU. Thanks and Regards.

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AZIZ_HASSAN
Moderator
Moderator 100 sign-ins 50 solutions authored 10 likes received
Moderator

Hi,

Thank you for the clarification. Please find the answers below.

1) The functionality of Q10 is in case you don't have a internal switch in motor for PWM control, there you can use this configuration to give PWM via a external switch to vary the voltage (from 0 to 100%).

2) The purpose of C136 is to filter out the high frequency components across the V_IO_SELV isolated supply. Remember one point here that the PWM is directly coming from MCU not from gate driver so you need one voltage source at the gate terminal to give adequate gate voltage as per switch requirement. 

3) You can directly connect PWM of MCU to motor terminals provided the a switch is already there in motor. If not then configure it as explained in point 1 and in schematics to vary the voltage.

4) If you don't  want to give PWM( means you want to operate the motor at fixed supply) , you can remove the circuit and make the direct ground as return path. Another way is to give 100% PWM to FET(Q10) and use it as fixed voltage but there will be unnecessary power loss at Q10.

I hope you understood the the explanation.

BR,

AZIZ HASSAN

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