Level 2
The active free-wheeling reduces the power losses in the free-wheeling MOSFET during the PWM operation (pulse width modulation), therefore reducing costs at system level:
- allowing the usage of smaller MOSFETs and/or smaller MOSFET packages
- reducing the required PCB cooling surface of the free-wheeling MOSFET
Title: Current flow during off-phase of the PWM period – Active free-wheeling (with low-side PWM)
Title: Current flow during off-phase of the PWM period – Passive free-wheeling (with low-side PWM)
Example: ILOAD @70 % duty cycle = 15A, VF = 1V, RDSON = 7 mOhm
Title: Example of power dissipation in the freewheeling MOSFET with active and passive free-wheeling
In this example, the active free-wheeling decreases the average power dissipation in the free-wheeling MOSFET by 4 W.
Assuming a junction-to-ambient thermal resistance (RTH-JAMB) of 25 K/W, the active free-wheeling control scheme reduces the average FW MOSFET temperature by 100 K, compared to a passive free-wheeling scheme.
- allowing the usage of smaller MOSFETs and/or smaller MOSFET packages
- reducing the required PCB cooling surface of the free-wheeling MOSFET
Title: Current flow during off-phase of the PWM period – Active free-wheeling (with low-side PWM)
Title: Current flow during off-phase of the PWM period – Passive free-wheeling (with low-side PWM)
Example: ILOAD @70 % duty cycle = 15A, VF = 1V, RDSON = 7 mOhm
Title: Example of power dissipation in the freewheeling MOSFET with active and passive free-wheeling
In this example, the active free-wheeling decreases the average power dissipation in the free-wheeling MOSFET by 4 W.
Assuming a junction-to-ambient thermal resistance (RTH-JAMB) of 25 K/W, the active free-wheeling control scheme reduces the average FW MOSFET temperature by 100 K, compared to a passive free-wheeling scheme.
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