How Can I Measure the Reverse Recovery Time of Power Rectifiers?

Avtech model AVR-EB4-B is ideal for performing tRR measurements on fast power diodes. The AVR-EB4-B is capable of generating pulsed forward bias currents of up to +2A (for up to 10 us), followed by a reverse bias pulse of up to -4A (again, for up to 10 us). The transition time from forward bias to reverse bias is less than 3 ns, allowing ultra-fast rectifiers to be tested. The device under test (DUT) is connected in series with a 50 Ohm resistor. The voltage across the resistor may be monitored to observe the diode current waveform. The general connection scheme is illustrated below:

AVR-EB4-B Diode Reverse Recovery (tRR) Measurement Set-up

The 50 Ohm resistor provides a partial termination for the coaxial line connecting the AVR-EB4-B to the test jig. That is, it is a proper termination when the diode is forward biased, but it is not a proper termination when the diode stops conducting in the reverse direction. However, by keeping the coaxial cable length less than 8 inches (20 cm), the impedance-mismatch reflections are minimal.
Some results for different diodes are shown below. In all cases, the forward bias is +100V (+2A), and the reverse bias is -200V (-4A), approximately. The top waveform is the input to the test jig, and the bottom waveform is the output. The "CH2 -Width" measurement at the right is a measure of the width of the waveform at the 10% reverse voltage point (-20V), which can be interpreted as tRR.

The first waveform shows the results obtained with an On Semiconductor 1N4937 diode. It displays the classis reverse recovery waveform, with a reasonably fast tRR of 154 ns:

1N4937 (40 ns/div)

tRR measurements for the 1N4937

The next waveform shows the results obtained with a Motorola 1N4004 diode. This is a dramatically slower diode, with a tRR of 1.2 us:

1N4004 (200 ns/div)

tRR measurements for the 1N4004

The third waveform shows the results obtained with a Diodes Incorporated UF1007 diode. This is a faster diode diode, but with a relatively sharp turn-off transient:

UF1007 (20 ns/div)

tRR measurements for the UF1007

The last waveform shows the results obtained with an International Rectifier HFA08TB120S diode. This diode is noteworthy for it fast, but very "soft" (i.e., gradual) turn-off transient:

HFA08TB120S (40 ns/div)

tRR measurements for the HFA08TB120S

These waveforms demonstrate the versatility of the AVR-EB4-B. However, if the AVR-EB4-B doesn't meet your needs, send us your special testing requirement!

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