Moderator
Paralleling power devices is of interest to flexibly increase the power rating of inverter systems. Since the ongoing chip development leads to increasingly rising nominal current ratings in the high power workhorse, the IHV module with 140x190 mm footprint (e.g. for 3.3 kV: 1200A --> 1500 A --> 2400 A), a fine tuned diversification of output current and output power gets more and more into focus.
The modular semiconductor concept of the XHP™ 2 and XHP™ 3 modules takes this into account. Both modules are shown in figure 1. These modules support a new, flexible type of converter design.
An easy scalability can be achieved by placing the required number of XHP™ devices side by side as shown in figure 2 for four devices FF550XTR33T3E4 delivering 2x2200 A nominal current. Lower or higher current ratings can easily achieved by removing or adding further XHP™ modules.
Paralleling has always been seen as critical regarding the parameter matching of the paralleled devices. Without further measures, randomly chosen devices may have an uneven current distribution as show in figure 3.
Differences in the static electrical module parameters Vcesat and Vf lead to such maldistribution of currents between the paralleled devices, therefore to uneven conduction as well as uneven switching losses.
Beyond that differences in the dynamic electrical module parameters turn-off delay tdoff and pinch-off voltage Vp can lead to a staggered turn-off between the paralleled devices, therefore to circulating currents, differences in switching losses and deviations in the diode peak power values.
Of course, the occurrence of such unbalances, resulting in differences in losses and uneven junction temperatures between the devices, usually requires a current derating to keep the data sheet limits and stay below the maximum allowed junction temperature in worst case operation.
To achieve symmetric switching and conduction behavior as shown in figure 4 and to abandon the need of a derating to be foreseen by the inverter developer, Infineon offers grouped XHP™ modules for which strict selection rules are applied.
- Modules are grouped and delivered based on a set of static and dynamic parameters.
- Parameter distribution of the devices in one group are extremely tight. The grouped modules have similar, well fitted static and dynamic parameters.
- Customers receive grouped modules as a bundled set. The modules belonging to one group are marked individually.
The advantages are obvious:
- The unbalance in current sharing is minimized.
- There is no or just a minimal de-rating required, resulting in highest output current and output power for the paralleled modules.
- No further efforts for device selection are required from customer side.
How does the grouping work?
XHP™ modules for paralleling can be ordered as selected and grouped devices. These groups can be identified
Modules selected for paralleling are marked with the extension “_Pn”, e.g. groups of two have the annex _P2: FF450R33T3E3_P2.
Be aware, that each module type (available are _P2…_P6) has a different part number. Order the accordant part number with its specific annex and you will receive the correct set. Of course, the minimum order quantity depends on the grouping; e.g. order 6 pieces _P6 modules to get one set.
For further information on the selection process itself, have a look into the paper Demystifying the Paralleling of IGBT Modules.
More hints about handling and mounting of the XHP™ modules are given in the application note AN2018-07 XHP Application and Mounting Instructions.
