Aficionados of BLHeli call out the benefits of “damped light” and “active freewheeling”, terms coined by BLHeli’s author.
Since these are terms invented by BLHeli, so you might wonder whether they are truly innovative or just marketing hype for existing techniques.
Lets go to the BLHeli manual for an explanation.
Pwm damped light mode adds loss to the motor for faster retardation. Damped light mode always uses high pwm frequency. In damped light mode, two motor terminals are shorted when pwm is off
Taking the last statement first, in fact, what happens that as that during the OFF phase of the PWM drive, the high side FETs at both ends of the winding are turned ON. One FET is on for the whole phase, and the other one switches on a short time after its corresponding low side FET turns off. The short time is to allow the low side FET to cease conducting, otherwise both high and low side FETs would conduct at the same time, a current from battery +ve to -ve via the two FETs. There is a corresponding pause at the end of the PWM phase. The time delays allowed depend on the driver circuitry and FET performance, they are specified in the firmware for a specific and don’t necessarily apply to a pin compatible ESC.
This technique is known in the wider community as COMPLEMENTARY PWM, a very standard technique. Continue reading BLHeli 14.8 damped light and active freewheeling