2ED21091S06F View Datasheet(PDF) - Infineon Technologies
Part Name
Description
MFG CO.
'2ED21091S06F' PDF : 26 Pages View PDF
2ED21091S06F
650 V half bridge gate driver with integrated bootstrap diode
The low ohmic current limiting resistor provides essential advantages over other competitor devices with high
ohmic bootstrap structures. A low ohmic resistor such as in the 2ED210x family allows faster recharging of the
bootstrap capacitor during periods of small duty cycles on the low side transistor. The bootstrap diode is a real
pn-diode which works with all control algorithms of modern power electronics, such as trapezoidal or sinusoidal
motor drives control.
5.9
Calculating the bootstrap capacitance CBS
Bootstrapping is a common method of pumping charges from a low potential to a higher one. With this technique
a supply voltage for the floating high side sections of the gate drive can be easily established according to Figure
17. This method has the advantage of being simple and low cost but may force some limitations on duty-cycle
and on-time since they are limited by the requirement to refresh the charge in the bootstrap capacitor. Proper
capacitor choice can reduce drastically these limitations.
Figure 17 Half bridge bootstrap circuit in 2ED210x
When the low side MOSFET turns on, it will force the potential of pin VS to GND. The existing difference between
the voltage of the bootstrap capacitor VCBS and VCC results in a charging current IBS into the capacitor CBS. The
current IBS is a pulse current and therefore the ESR of the capacitor CBS must be very small in order to avoid losses
in the capacitor that result in lower lifetime of the capacitor. This pin is on high potential again after low side is
turned off and high side is conducting current. But now the bootstrap diode DBS blocks a reverse current, so that
the charges on the capacitor cannot flow back to the capacitor CVCC. The bootstrap diode DBS also takes over the
blocking voltage between pin VB and VCC. The voltage of the bootstrap capacitor can now supply the high side
gate drive sections. It is a general design rule for the location of bootstrap capacitors CBS, that they must be placed
as close as possible to the IC. Otherwise, parasitic resistors and inductances may lead to voltage spikes, which
may trigger the undervoltage lockout threshold of the individual high side driver section. However, all parts of
the 2ED210x family, which have the UVLO also contain a filter at each supply section in order to actively avoid
such undesired UVLO triggers.
The current limiting resistor RBS according to Figure 17 reduces the peak of the pulse current during the low side
MOSFET turn-on. The pulse current will occur at each turn-on of the low side MOSFET, so that with increasing
switching frequency the capacitor CBS is charged more frequently. Therefore a smaller capacitor is suitable at
higher switching frequencies. The bootstrap capacitor is mainly discharged by two effects: The high side
quiescent current and the gate charge of the high side MOSFET to be turned on.
Datasheet
www.infineon.com/soi
14 of 26
V 2.22
2020-07-02
Share Link: 
