IRS26302DJPBF Datasheet, PDF (31/51 Pages) International Rectifier – FULLY PROTECTED 3-PHASE BRIDGE PLUS ONE GATE DRIVER

IRS26302DJ
DC+ BUS
Figure 27: Three phase inverter
Q1
ON
I_U
V_S1
Q2
D2
OFF
DC- BUS
Figure 28: Q1 conducting
Figure 29: D2 conducting
Also when the V phase current flows from the inductive load back to the inverter (see Figures 30 and 31), and Q4
IGBT switches on, the current commutation occurs from D3 to Q4. At the same instance, the voltage node, V_S2,
swings from the positive DC bus voltage to the negative DC bus voltage.
Figure 30: D3 conducting
Figure 31: Q4 conducting
However, in a real inverter circuit, the V_S voltage swing does not stop at the level of the negative DC bus, rather it
swings below the level of the negative DC bus. This undershoot voltage is called “negative V_S transient”.
The circuit shown in Figure 32 depicts one leg of the three phase inverter; Figures 33 and 34 show a simplified
illustration of the commutation of the current between Q1 and D2. The parasitic inductances in the power circuit from
the die bonding to the PCB tracks are lumped together in L_C and L_E for each IGBT. When the high-side switch is on,
www.irf.com
© 2009 International Rectifier
31