IRS26310DJPBF_15 Datasheet, PDF (31/44 Pages) International Rectifier – HIGH VOLTAGE 3 PHASE GATE DRIVER IC WITH DC BUS OVER –VOLTAGE PROTECTION

IRS26310DJPbF
Figure 28: D3 conducting
Figure 29: 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 30 depicts one leg of the three phase inverter; Figures 31 and 32 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,
V_S1 is below the DC+ voltage by the voltage drops associated with the power switch and the parasitic elements of the
circuit. When the high-side power switch turns off, the load current momentarily flows in the low-side freewheeling
diode due to the inductive load connected to V_S1 (the load is not shown in these figures). This current flows from the
DC- bus (which is connected to the COM pin of the HVIC) to the load and a negative voltage between V_S1 and the
DC- Bus is induced (i.e., the COM pin of the HVIC is at a higher potential than the V_S pin).
Figure 30: Parasitic Elements
Figure 31: V_S positive
Figure 32: V_S negative
In a typical motor drive system, dV/dt is typically designed to be in the range of 3-5 V/ns. The negative V_S transient
voltage can exceed this range during some events such as short circuit and over-current shutdown, when di/dt is
greater than in normal operation.
International Rectifier’s HVICs have been designed for the robustness required in many of today’s demanding
applications. The IRS26310D has been seen to withstand large negative V_S transient conditions on the order of -50 V
for a period of 50 ns. An illustration of the IRS26310D’s performance can be seen in Figure 33. This experiment was
conducted using various loads to create this condition; the curve shown in this figure illustrates the successful
operation of the IRS26310D under these stressful conditions.
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