EVAL-IH-R5IPB-A-V1 Evaluation board
User Guide
Experimental results
(c)
Figure 13
INN voltage change: (a) in overtemperature warning (OTW) operation and (b) in
overtemperature shutdown (OTS) (1 V/div – 100 µs/div); (c) schematic of the INN voltage
sense
5.2
Performing EMC tests on the board
The most stressful situations for the SEPR-based induction cooking systems occur when the grid voltage
experiences sudden changes. In fact, this leads to an increase in the bus voltage and finally, due to the voltage
resonant operation, to a significant increase of the peak-collector current and the peak collector-emitter voltage
of the IGBT. In order for an induction cooking system to be reliable and usable in the market, it has to fulfill the
electromagnetic compatibility (EMC) requirements, which comprises, among other things, system testing under
sudden variations of the grid voltage. The IEC 61000-4 norm [8] provides guidelines on how to test the reliability
of a system against grid transients. Among the different tests considered, two are of major interest to show how
the IEWS20R5135IPB could improve system reliability: test of instantaneous AC power supply interruption and
surge tests. These tests have been performed by using the test generators presented in section 2.2, and the
results are addressed in the next sections. Before addressing the details of each test, it is important to mention
that the system is only properly protected by means of the IEWS20R5135IPB, which is only guaranteed if the
device can sense accurately the collector-emitter voltage and the collector current. The general
recommendation provided in section 4.1 should guarantee the best and most reproducible behavior of the
device.
5.2.1
Test during an AC instantaneous supply interruption
Instantaneous interruption of the AC supply (i.e., loss of supply voltage during a time shorter than 30 cycles) can
occur because of damages to the electrical grid that cannot be immediately compensated by the utility
infrastructure. In the case of an induction cooker that is based on the SEPR topology, the effect of an
instantaneous AC loss can be catastrophic, as it may ultimately lead to the failure of the IGBT. This is because
during a short interruption of the main supply, the bus capacitor, which feeds the energy to the resonant inverter,
is rapidly discharged and then charged again. By the effect of the resonance between the bus capacitance and
the input filter inductance, the voltage on the bus capacitor can exceed the input voltage, as shown in Figure 14.
Application Note
20 of 34
V 1.1
2019-11-25
