C1 must also not be too large that charging is too slow and the voltage level does not rise sufficiently to keep the MOSFET on. "A large enough capacitance must be chosen for C1 so that it can supply the charge required to keep Q1 on for all the time. For simplicity I am posting the capacitor related section here: You can find it in the paragraph right below Fig. I have talked about the capacitor in the article/tutorial. The ceramic capacitor is not required if the bootstrap Since we’re using anĮlectrolytic capacitor, a ceramic capacitor should be used in parallel with Like 30kHz to 50kHz, I use between 4.7 ♟ and 22 ♟. For low frequencies suchĪs 50Hz, I use between 47 ♟ and 68 ♟ capacitance. So, I just estimate the required capacitance. Involved, some of which we may not know – for example, the capacitor leakageĬurrent. Yes, there are formulaeĪvailable for calculating the capacitance. The higher the dutyĬycle, the higher the required capacitance for C1. The frequency, the higher the required capacitance for C1. The higher the on time, the higher the required capacitance. Slow and the voltage level does not rise sufficiently to keep the MOSFET on. C1 must also not be too large that charging is too A large enoughĬapacitance must be chosen for C1 so that it can supply the charge required to Source level of Q1 to drive the Q1 in high-side configuration.
The C1 and C2 is used to add the extra voltage – VB in this case – above the When LIN = 1 and Q2 is on, C1 and C2 get charged to the level on VB, D1, C1 and C2 along with the IR2110 form the bootstrapĬircuitry.