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## Half Bridge for switching Motor with PWM Signal.

Level 1
Level 1

Dear Community,

I want to build an half bridge to control the speed of an DC Motor. One side of the Motor is connected to DC+24V. The other side would be switched by the half bridge to DC+48V and to 0V. The controller is DC+5V Mikrocontroller.

I would use a Gate driver IC to control the MOSFETs. Which Mosfets I should use for the circuit? Which Gate Driver is the right for my Project.

How can I protect the Mikrocontroller. Is it enough to use Opto coupler at the Input of the Gate Driver?

1 Solution

## Re: Half Bridge for switching Motor with PWM Signal.

Moderator
Moderator

Hello @User18636 ,

If you are going for the discrete solution, we need to select the switches which can withstand both the starting current as well as stall current.

Starting current is a single pulse with a known time constant, hence can be considered as pulse current rating of the MOSFET.

But we need to know the duration for which the stall current has to be withstand by the MOSFET. Do you have blocked rotor detection implemented in your design? If yes, what is the response time for this detection and failure reaction?

If there is no such feature, then this stall current has to be considered as worst case continuous current, based on which we can consider  100V, 30A rated switch for this application.

We have below solutions which meet above requirements

1. IRSM005-301MH - Integrated half bridge + gate driver

2.  Discrete switches with half bridge gate driver :   ISZ230N10NM6 or ISC230N10NM6 can be used along with 2EDF7275K half bridge driver if functional isolation is sufficient

or

ISZ230N10NM6 or ISC230N10NM6 can be used along with 2EDF8275F id reinforced insulation is needed.

You can also use discrete drivers for this application, but this may consume more layout space. If you still wish to evaluate that option, please let us know, we can suggest the devices.

Gate driver suggestion is provided based on the isolation request. It can be further optimized if you have clear understanding of the required protection features and isolation requirements.

Regards

Meghana R

7 Replies

## Re: Half Bridge for switching Motor with PWM Signal.

Moderator
Moderator

Hello @User18636 ,

Thank you for posting on Infineon Community. Can you please let us know below details, so that we can suggest you the right solution.

1. Is one end of the motor permanently connected to DC+24V or is it connected through a switch ? And which source will turn on first during the system start up, DC+48V or DC+24V?

2. What is the power rating of the DC motor you are intending to use?

3. What is the intended application, in which you want to use above application?

Regards

Meghana R

## Re: Half Bridge for switching Motor with PWM Signal.

Level 1
Level 1

Dear Meghana,

1. The first Side of the Motor is permanently connected to +24V. Through start up nothing should happen. Both MOSFET has to be off. After start up I move a Joystick (CH Products: HFX-33S12-034) (Forward: 0% - 100%, Reverse: 0% - 100%). Depending on the Direction the Higher or lower MOSFET has to drive the Motor. Between Joystick and MOSFET Driver is a Processor. So I would use a MOSFET Driver to protect the Processor and use feedback from Fault Pin.

2. The Motor has 100W, DC+24V.

3. The Application is for Industry to control a Robot.

I want to build a strong Half Bridge that can deliver Power. I would also like to Dsiplay errors for easier error analysis.

## Re: Half Bridge for switching Motor with PWM Signal.

Moderator
Moderator

Hello @User18636 ,

MOSFET:

1. During off state, the blocking voltage across switches would be 48V. Considering a margin, 80V - 100V rated devices would suffice your requirement

2. The inrush current in DC motors will generally be more than 3 times the steady current or higher depending on the application. Hence to decide the current rating of the device, we need the details of Inrush current, inrush duration and the maximum operating ambient temperature considered for your application. Kindly share these details in order to suggest the right device for your requirement.

Gate driver:

There are very wide range of gate driver solutions available in Infineon portfolio.

https://www.infineon.com/cms/en/product/power/gate-driver-ics/

Isolated Gate driver solutions are available for the systems voltages >250V and might be overrated for your application.

Isolation may not be mandatory for the 48V systems as it comes under low voltage category. But if you still wish to have an isolation between control and power section, we would need few more details from you to suggest the right driver

1. Type of isolation required: Functional or Reinforced?

2. Maximum withstand voltage required?

3. Type of protection features required in the gate driver ( Ex: I/P & O/P UVLO, Short circuit protection, active clamping etc.,)

Kindly provide above details so that we can provide appropriate suggestion.

Regards

Meghana R

Attachments are accessible only for community members.

## Re: Half Bridge for switching Motor with PWM Signal.

Level 1
Level 1

Find in attechment the Motor Data Sheet. The maximum operating ambient temperature is 50°C. When the Motor is used, the user starts the Motor and run. After 10 seconds the Motor stops. The Working peridod over one day is maybe 3-4 hours. Not at one time. The Motor Stop and runs shortly. This is why I want to use MOSFETs.

Further I send you the schematic of the Application.

With the Isolation, I thought about the protection the processor. In an older project with Power Mosfets I have designed a Full Bridge. After Power Up the Circuit works 10 seconds and then burn down the Mosfet and the Processor. I stopped designing drivers after this project.

This is my First Project with Power Mosfets. So I have no experience.

Best regards.

## Re: Half Bridge for switching Motor with PWM Signal.

Moderator
Moderator

Hello @User18636 ,

Single supply of +24V would be sufficient to drive the motor using a full bridge. Can you please let me know the purpose of using two supplies for this application?

There are integrated motor drive solutions which may suit your application. These components shall include the switches and their gate control circuits in a single IC. You may check out  IFX9201SG, an industrial grade integrated full bridge driver IC for DC motor application. It comes with configurable current limit upto 6A. It also includes inbuilt protection features like SCB, SCG etc., If you wish to have higher current range, you may consider TLE8209-2SA. You may explore other integrated full bridge driver solutions using below link.

https://www.infineon.com/cms/en/product/power/motor-control-ics/brushed-dc-motor-driver-ics/integrat...

Above integrated solution would reduce PCB size and also simplify the design complexity.

Or, if you still prefer to go with discrete solutions, please consider below points.

Peak starting current in this application would be 24/1.2ohm = 20A, which is much higher than the nominal continuous current. We can follow two approaches here.

1. Choose switch with lower current rating just based on the continuous current value and limit the starting current through control. There are two challenges in this solution
1. Controlling the starting current would slow down the system response.
2. Current sensing and the control loop sample time should be carefully designed so that the current does not exceed the chosen switch ratings
2. If system cost can be compromised, then we can choose a switch rated for this starting current. This shall allow us to achieve faster system response.

Please let us know your preference. If you wish to go ahead with first approach in discrete solution, please specify the current limit that you would set in the control loop. Based on that we can suggest you the switches.

Regards

Meghana R

## Re: Half Bridge for switching Motor with PWM Signal.

Level 1
Level 1

Dear Meghana,

see my PDF Document - "MotorControl.pdf" above. I can't use a full bridge, because there are many Systems in use to change the System Structure.

The Motor is only connected by one side to the Half bridge. The other Side is connected to  a multi Point. In the End Application there are 6 Motors installed. I have to build 6 Half Bridge Drivers to control each Motor.

In the Last years I used a normal Relais to control the direction of Rotation and trimmed down the Power Supply. This is bad, because all Motors see the Supply Voltage. So when I work with the Machine I have to trim all the time.

The New concept is to use a Joystick and control the Half Brdige with a PWM Signal.

Regards

## Re: Half Bridge for switching Motor with PWM Signal.

Moderator
Moderator

Hello @User18636 ,

If you are going for the discrete solution, we need to select the switches which can withstand both the starting current as well as stall current.

Starting current is a single pulse with a known time constant, hence can be considered as pulse current rating of the MOSFET.

But we need to know the duration for which the stall current has to be withstand by the MOSFET. Do you have blocked rotor detection implemented in your design? If yes, what is the response time for this detection and failure reaction?

If there is no such feature, then this stall current has to be considered as worst case continuous current, based on which we can consider  100V, 30A rated switch for this application.

We have below solutions which meet above requirements

1. IRSM005-301MH - Integrated half bridge + gate driver

2.  Discrete switches with half bridge gate driver :   ISZ230N10NM6 or ISC230N10NM6 can be used along with 2EDF7275K half bridge driver if functional isolation is sufficient

or

ISZ230N10NM6 or ISC230N10NM6 can be used along with 2EDF8275F id reinforced insulation is needed.

You can also use discrete drivers for this application, but this may consume more layout space. If you still wish to evaluate that option, please let us know, we can suggest the devices.

Gate driver suggestion is provided based on the isolation request. It can be further optimized if you have clear understanding of the required protection features and isolation requirements.

Regards

Meghana R