Transistors｜Evaluation

The Importance of the Reverse Recovery Characteristics of Switching Elements in Inverter Circuits Comparison of Losses in a PrestoMOS™ MOSFET and a Standard SJ MOSFET Using Double-Pulse Tests (Actual Measurement Results)

2023.12.14

Points of this article

・In order to evaluate reverse recovery losses in an inverter circuit, double pulse tests were used.

・In comparisons of PrestoMOS™ MOSFETs with standard SJ MOSFETs, it was confirmed that PrestoMOS™ MOSFETs, with superior reverse recovery characteristics, had smaller switching losses.

・This indicates the superiority of PrestoMOS™ MOSFETs with respect to reducing losses in inverter circuits.

The third topic, comparison of losses in a PrestoMOS MOSFET and a standard SJ MOSFET using double pulse tests, is explained based on actual measurement results.

Comparison of Losses in a PrestoMOS™ MOSFET and a Standard SJ MOSFET Using Double-Pulse Tests (Actual Measurement Results)

Fig. 12 shows the double pulse test circuit. A freewheeling current is made to flow in Q1 by turning the low side MOSFET (Q2) on and off, and switching losses are measured. The measurement procedure in double pulse tests is as follows.

  • ① Turn Q2 on, pass a current in L1, accumulate energy in L1.
  • ② Turn off Q2, so that a freewheeling current flows from L1 to the body diode of Q1, and energy accumulated in L1 is released (at this time, the Q2 turn-off loss is measured).
  • ③ Turn on Q2 during freewheeling current flow in the Q1 body diode, and measure the turn-on loss while a reverse recovery current is flowing (measured using a current probe and voltage probe).

※For details of the theory of operation of a double pulse test measurement circuit, refer to “Evaluating MOSFET Recovery Characteristics Using Double-Pulse Tests” in the Tech Web Si Power Device Evaluation topic, or refer to the application note（PDF） based on this section.

As the devices to be evaluated, the R6030JNx, a PrestoMOS™ MOSFET featuring a fast reverse recovery characteristic, and the R6030KNx, a standard SJ MOSFET, were compared. Products of other manufacturers were also evaluated and compared. Measurement conditions for the measurement circuit of Fig. 12 were as follows.

  • （1） Low side switching (freewheeling on the high side)
  • （2） Gate driving current VGS : 0 V to 12 V
  • （3） Supply voltage Vin : 280 Vdc
  • （4） Inductor L1 : 1 mH
  • （5） Steady-state drain current ID: 2 A, 4 A, 6 A, 8 A, 10 A
  • （6） Gate resistance RG(on): Changed depending on the device (in order that the di/dt at turn-on was 100 A/µs)
    • ・ PrestoMOS™ MOSFET R6030JNx： 60 Ω （3 180 Ω resistors in parallel)
    • ・ R6030KNx：180 Ω
  • （7） Gate resistance RG(off)： 22 Ω

The current waveforms at turn-on measured in double pulse tests appear in Fig. 13; the voltage waveforms are in Fig. 14. The switching current waveforms at turn-off are in Fig. 15, and Fig. 16 shows the voltage waveforms. These waveforms were measured with a steady-state drain current ID of 6 A.

Compared with the R6030KNx, we see that the turn-on reverse recovery current of the PrestoMOS™ MOSFET R6030JNx (red lines) is extremely small, and moreover the reverse recovery time is short. As a result, the turn-on loss, discussed later, can be dramatically reduced.

Next, the switching loss measurement results are shown.
Fig. 17 shows the energy EON consumed by the switch at turn-on and Fig. 18 shows the energy EOFF consumed by the switch at turn-off. As a result, as indicated by the switching waveforms in Fig. 13 and 15 above, it is clear that losses are low for the PrestoMOS™ MOSFET R6030JNx (red lines).

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