How to set the output of high-side driver(VND7020AJ) with pwm

[DiogoPedrosa]

Hey,so I was trying to use the VND7020AJ as a driver to loads,and wanted to power the load to 7.2V while powering the high side driver with 12V.Im using a stm32f103rb,and using an outpin pin timer to control the pulse width to the input pin on the driver.It works fine when not connecting the driver to the load,but when I connect it jumps to 12V.Is it possible to pulse width the output or not?Is there a specific frequency that I am supposed to use?The input pin is still under 60%pulse(around 1.9V).Ive tried modifying the pulse while connected to the load but it didnt change anthing on the output.

The code is pretty simple,Ive only set the input pin and controlled it:

__HAL_TIM_SET_COMPARE(&htim3,TIM_CHANNEL_3,3000);

Clock(8Mhz)

Prescaler(8-1)

CounterPeriod(10000-1)

[Andrew Neil]

Please show your schematic

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

[DiogoPedrosa]

Ive attached the schematic,its a custom board thats used to drive loads in an formula sae car.Im measuring the voltage in the output pins in the board and in the connector of the board,which is simply a trace directly to the connector.

The high side switch is fed with stable 12V.

What I was doing was modifyng the pulse in the input pin(IN1),and then measuring the pin with a multimeter.When the output is 7.2v I connect to the load and it instantly jumps to stable 12V,or whatever I'm feeding the driver.Ive tried changing the pulse while connect to the load and it doesnt change anything apparently.

Ive also measured the voltage on the input pin(IN1) and it doesnt change when connected to the load and when not.

[Andrew Neil]

Show the full schematic - including power supplies and the STM32

[DiogoPedrosa]

Sure heres the full schematic.Page 1 is the connector,Page 2 is the power supply,Page 3 is the STM32,Page 4 is releated to the high side driver,Page 6 is related to the fuses of the outputs which are in series with the outputs.Page 5 and 7 are not really related to the driver

[MHoll.2]

Without knowing the PWM frequency and the load you want to drive it's difficult to say why you don't see a reduced voltage. Do You have access to a oscilloscope? If yes confront the INx signal with the OUTx signed (with the load connected) this are only Hig-side switches they need a load to work properly.

[DiogoPedrosa]

I've attached photos of the oscilloscope during testing. It seems that when the driver is connected to the load, it can't maintain a stable frequency. I've tested with 20 Hz, 100 Hz, and 20 kHz, but nothing really changed. Even though the frequency appears to vary (perhaps the oscilloscope couldn't compute it correctly), the average voltage remained close to the maximum input I used to power the board.

In this specific test, I supplied the board with 8V, but the same issue occurred when using 12V.

I noticed that the frequency doesn't remain steady—it seems random. However, the current stayed stable throughout the entire test.

I also changed the load to check if it was causing the issue.

Next, I will test with a DC motor to determine if the problem is just a measurement issue and not related to the actual output voltage.

Here’s my PWM configuration for the 20 Hz pulse:

Prescaler:(8-1)

CounterPeriod(50000-1)

Clock():8Mhz

I just added this simple code to turn the pulse to 60%.The config is pre generated by cube mx.Ive also added the HAL_TIM_PWM_Start():

__HAL_TIM_SET_COMPARE(&htim3,TIM_CHANNEL_3,30000);

Heres the description for the photos even though the titles are self explanatory:

Load_Connect_Output:Output of the smartswitch with the load Connected.

Load_NotConnect_Output:Output of the smartswitch with no load connected.

Input_Pin:This is the voltage going to the inputPin of the smartSwitch.

[MHoll.2]

Ok

From the Load_Connected_Output.jpeg I can see that "someting" is holding the voltage high while the Switch is OFF.

How is Your load connected?

The load has to be between the OUTx and GND. (The VND7020AJ is a High-side only switch)