Timeline for DC motor PWM control and flyback diode question
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 10, 2022 at 14:39 | history | edited | JRE | CC BY-SA 4.0 |
deleted 4 characters in body; edited title
|
| Apr 10, 2022 at 14:01 | answer | added | Russell Gunn | timeline score: 1 | |
| Oct 19, 2020 at 16:21 | vote | accept | User | ||
| Oct 19, 2020 at 16:21 | vote | accept | User | ||
| Oct 19, 2020 at 16:21 | |||||
| Oct 19, 2020 at 16:20 | vote | accept | User | ||
| Oct 19, 2020 at 16:21 | |||||
| Apr 21, 2020 at 14:49 | comment | added | user16324 | @KevinWhite Fair point. There is no mention of PWM freq in the question so ... | |
| Apr 21, 2020 at 14:25 | comment | added | Kevin White | @BrianDrummond - In a normal PWM motor control system the frequency of the PWM is such that the diode conduction spike is the full length of the off-cycle so the back-emf never keeps the diode reverse biased as the next on-cycle will drive forward current into the motor and reverse bias the diode again before that happens. Although the effect you're describing would happen at a low-frequency PWM, that is not the normal scenario. | |
| Apr 21, 2020 at 11:46 | comment | added | user16324 | @KevinWhite Not quite. You are correct there will be a brief conduction spike but that's only from the motor's inductance. The braking in the question is from the back EMF which has the same polarity as the applied EMF keeping the diode reverse biased : therefore no braking as per your answer. Two separate phenomena, but often confused with each other. | |
| Apr 20, 2020 at 22:45 | answer | added | Kevin White | timeline score: 2 | |
| Apr 20, 2020 at 22:44 | comment | added | Kevin White | @BrianDrummond - no - when the transistor turns off the inductance results in current flowing forward through the diode. | |
| Apr 20, 2020 at 18:52 | comment | added | user16324 | Unless you reverse the motor, the back EMF keeps the diode reverse biased. | |
| Apr 20, 2020 at 15:43 | answer | added | Andy aka | timeline score: 3 | |
| Apr 20, 2020 at 15:22 | history | asked | User | CC BY-SA 4.0 |