IRS211(7,71,8)(S)

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© 2008 International Rectifier

11

A common problem in today’s high-power switching converters is the transient response of the switch node’s

voltage as the power switches transition on and off quickly while carrying a large current. A typical half bridge

circuit is shown in Figure 5; here we define the power switches and diodes of the inverter.

If the high-side switch (e.g., Q1 in Figures 6 and 7) switches off, while the current is flowing to a load, a current

commutation occurs from high-side switch (Q1) to the diode (D2) in parallel with the low-side switch of the

DC bus voltage.

Q1

Q2

D1

D2

DC+ BUS

DC- BUS

Input

Voltage

To

Load

Figure 5: Half Bridge Circuit

Q1

OFF

Q2

OFF

D1

D2

DC+ BUS

DC- BUS

Figure 6: Q1 conducting

Figure 7: D2 conducting

Also when the current flows from the load back to the inverter (see Figures 8 and 9), and Q2 switches on, the

DC bus voltage to the negative DC bus voltage.