I'm using below circuit for driving a motor with relay control.
so this circuit is designed for both a relay as well as buzzer but right now im using it as relay control In that case, there are below changes:
R77 is DNP.
LS1 is DNP. else as it is
so I'm controlling relay; this max coil current is 65 mA, 24V and im driving the motor of 24V 5A problem that i faced is MOSFET getting burned after some time, so please let know what the problem is and what other things I can improve in this circuit for better protection and performance run without failure.
@jim-p and @PaulRB One more thing: I was thinking, which is good for motors, solenoids, and actuators, high or low side switching? and need your validation, which is good for automotive applications with user safety, then I search on ChatGPT, and there are the answers.
So please let me know if he/she is saying it correctly.
ChatGPT answers
Why High-Side Switching ?
1. Safety Considerations (Major Concern in Automotive & Industrial Applications)
Low-side switching causes a floating load when OFF, meaning that the load (actuators, motors, or lights in the BCU) stays at battery voltage even when it's "turned off."
In contrast, high-side switching ensures the load is fully disconnected from power and remains at ground potential when OFF, eliminating leakage currents or unintended activation due to ground loops.
Risk of ground loops: In low-side switching, if there's a poor ground connection in the vehicle’s chassis, it could cause erratic behavior or even permanent damage to electronic modules.
2. Industry Standards (Automotive & Agricultural Equipment Follow High-Side Switching)
Most automotive and off-road vehicle manufacturers strictly use high-side switching for controlling loads like motors, actuators, and solenoids because of its reliability and safety.
Example: ECU designs by Bosch, Continental, and NXP for automotive body control modules (BCMs) always use high-side switches.
This is a key point to convince your senior—following industry best practices ensures reliability and compliance with automotive design standards.
3. Ground Reference Stability (Critical for BCU Sensors and Modules)
In low-side switching, when the switch (MOSFET) is OFF, the load is still connected to V+ but has no direct ground. This can cause floating ground issues, leading to false triggering or malfunctioning of sensors, CAN communication modules, and microcontrollers.
In high-side switching, the load is always referenced to ground when OFF, preventing these stability issues.
Important for BCU: Since the BCU is handling multiple power signals for actuators and sensors, ensuring a clean and stable ground is essential to avoid noise and communication errors.
4. Reliability & Protection Against Short Circuits
Low-side switching exposes the load to potential short circuits to ground. If the actuator’s wire touches the chassis, it creates a direct short circuit, leading to failure.
High-side switching provides better fault protection because even if a wire touches the chassis, there’s no direct path to complete the circuit unless the MOSFET is ON.
In automotive applications, short-circuit robustness is a must, and high-side switching is more fault-tolerant.
5. Better Control Over Inductive Loads (Motors, Solenoids, Relays in BCU)
The BCU will likely control solenoids, actuators, or motors (e.g., for hydraulic functions Electric Quick Lift).
Inductive loads generate back EMF (voltage spikes) when turned off, which can damage electronics if not managed properly.
In high-side switching, the freewheeling diode can be placed in a more efficient way, allowing the inductive energy to dissipate safely, reducing stress on MOSFETs and extending their lifespan.
Low-side switching exposes the MCU directly to back EMF noise, increasing the risk of failure.
6. Ease of Implementing Overcurrent and Thermal Protection
Automotive high-side driver ICs (like Infineon BTS50055, ST VNH7070, or TI’s high-side switches) have built-in current sensing and thermal shutdown.
These protect against overcurrent conditions and prevent overheating, improving the overall reliability of the BCU.
Low-side MOSFETs don’t offer the same level of integrated protection, requiring additional components (sensors, protection circuits) to achieve similar reliability.
Depends on the motor,solenoid and actuator and what devices you have for controlling them and how they need to be controlled.
Is cost and availability also a factor?
Post the data sheet for the devices you plan to use.
Is this circuit to be used in a vehicle of some sort?
If so, then high side switching is generally to be preferred since many devices use the vehicle chassis as ground (negative earth).
Otherwise, for a relay coil, low side switching is usually a better/simpler choice.
DNP in your schematic probably means Do Not Populate so omit R78. Also consider using a zener diode and balance the voltage divider to prevent Vgs(max) being exceeded for your P Channel mosfet.
See post #3
Depends on the motor,solenoid and actuator and what devices you have for controlling them and how they need to be controlled.
Is cost and availability also a factor?
Post the data sheet for the devices you plan to use.
