Delay calibration, double pulse test must be done!
Delay calibration, double pulse test must be done!
“The primary function of conducting double-pulse testing is to acquire the switching traits of energy semiconductors, which could be mentioned to accompany the complete life cycle of energy gadgets from R&D and manufacturing to software. Many issues could be finished based mostly on the system switching waveform obtained from the double-pulse check, together with: verifying the system design scheme and proposing enchancment instructions via the evaluation of the switching course of, extracting the switching attribute parameters to make the system specification, calculating the switching loss and reverse restoration loss as the facility provide Thermal design gives knowledge help, comparability of switching traits of gadgets from completely different producers, and so on.
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(This text is reproduced from the general public account: Energy Gadget Microscope, shared with everybody for trade and studying)
The primary function of conducting double-pulse testing is to acquire the switching traits of energy semiconductors, which could be mentioned to accompany the complete life cycle of energy gadgets from R&D and manufacturing to software. Many issues could be finished based mostly on the system switching waveform obtained from the double-pulse check, together with: verifying the system design scheme and proposing enchancment instructions via the evaluation of the switching course of, extracting the switching attribute parameters to make the system specification, calculating the switching loss and reverse restoration loss as the facility provide Thermal design gives knowledge help, comparability of switching traits of gadgets from completely different producers, and so on.
Measuring the impact of delay
The measured sign will expertise two delays throughout the measurement course of, and the distinction in delay skilled by completely different indicators may have a sure impression on the measurement outcomes.
The first delay is the delay of the analog entrance finish of the oscilloscope. The distinction in delay between completely different channels of the oscilloscope is on the ps stage, and the switching strategy of the facility system on the ns stage and the us stage could be ignored.
The opposite time is the delay of the probe. The direct delay distinction of various probes is within the ns stage. Presently, it has a big impression on gadgets with quick switching speeds, particularly for SiC and GaN gadgets have a good greater impression.
We use the measurement of SiC MOSFET switching course of for example as an instance the impact of measurement delay.
Within the determine beneath, the blue waveform is the waveform obtained earlier than delay calibration is carried out on the probe (earlier than calibration), and the crimson waveform is the waveform obtained after delay calibration is carried out on the probe (post-calibration waveform).
In line with the speculation, throughout the turn-on course of, when IDS begins to rise, a voltage drop will likely be generated on the parasitic inductance of the loop, which can trigger VDS to drop. The rise of IDS and the autumn of VDS ought to begin at virtually the identical time. Within the pre-calibration waveform, when IDS begins to rise, VDS stays unchanged and begins to fall after a delay of 5.5ns. This case is clearly inconsistent with the speculation, and it may be inferred that the IDS sign leads the VDS sign right now. After calibration, this drawback was solved.
Theoretically, throughout turn-off, the height of VDS needs to be close to the zero-crossing of IDS. Within the pre-calibration waveform, VDS reaches the best worth solely after IDS zero-crosses 5.5ns. After calibration, this drawback was additionally solved.
On the identical time, we additionally sorted out the switching attribute parameters, together with: turn-on delay td(on), turn-on time tr, turn-on power Eon, turn-off delay td(off), turn-off time tf, and turn-off power Eoff. It may be seen that the turn-on delay td(on) and turn-off delay td(off) have a distinction of about 2ns earlier than and after calibration. The turn-on time tr and turn-off time tf are virtually the identical earlier than and after calibration. The turn-on power Eon earlier than calibration is 395.31uJ in comparison with 147.53 after calibration. The uJ is 1.67 occasions bigger, and the off-energy Eoff of 20.28uJ earlier than calibration is 71.3% smaller than 70.54uJ after calibration.
It may be seen that the delay has a really apparent impression on the evaluation of the switching traits of the system and the calculation of parameters. Earlier than measuring, we are able to use the next 4 strategies to carry out delay calibration.
Technique 1: Concurrently measure the oscilloscope’s personal sq. wave sign
Calibrating the delay distinction between completely different voltage probes may be very easy, simply measure the identical voltage sign on the identical time, after which calibrate based on the measurement consequence.
We will use the sq. wave sign that comes with the oscilloscope, normally on the facet panel or entrance panel of the oscilloscope. It may be seen that though each probes are measuring the oscilloscope’s personal sq. wave, the delay of the waveform displayed on the oscilloscope display is 5.6ns forward of the 1-channel measurement channel forward of the 2-channel measurement channel. Then we are able to set the delay of channel 1 to -5.6ns within the channel setting menu of the oscilloscope, or set the delay of channel 2 to +5.6ns to finish the calibration.
Technique 2: The oscilloscope’s personal operate calibration
For a hard and fast sort of voltage or present probe, the delay is principally mounted, and the delay calibration could be carried out straight so long as the probe mannequin is understood. Now the features of the oscilloscope have gotten an increasing number of highly effective, and the mannequin of the probe could be recognized via the interface of the probe, in order that the oscilloscope can straight and routinely calibrate the system delay worth.
Technique 3 Time-lapse Calibration Fixture
Following the concept of measuring the identical sign on the identical time to calibrate the delay distinction of various voltage probes in Technique 1, and measuring the voltage and present indicators that change on the identical time, the delay distinction between the voltage probe and the present probe could be calibrated. Many oscilloscope producers have launched voltage and present probe delay calibration fixtures based mostly on this concept, which is handy for engineers to make use of straight with out having to make their very own calibration sources. For instance, Tektronix’s deskew pulse generator sign supply TEK-DPG and energy measurement offset correction fixture 067-1686-03.
Technique 4 makes use of system switching traits
If restricted by the gear at hand, we are able to additionally calibrate by the traits of the system switching course of talked about above. In line with the speculation, the rise of IDS and the autumn of VDS ought to begin virtually on the identical time throughout the opening course of. Then we are able to carry out double-pulse check underneath completely different check situations, learn the delay between IDS and VDS throughout every turn-on course of, after which calibrate after averaging.
(This text is reproduced from the general public account: Energy Gadget Microscope, shared with everybody for trade and studying)
The primary function of conducting double-pulse testing is to acquire the switching traits of energy semiconductors, which could be mentioned to accompany the complete life cycle of energy gadgets from R&D and manufacturing to software. Many issues could be finished based mostly on the system switching waveform obtained from the double-pulse check, together with: verifying the system design scheme and proposing enchancment instructions via the evaluation of the switching course of, extracting the switching attribute parameters to make the system specification, calculating the switching loss and reverse restoration loss as the facility provide Thermal design gives knowledge help, comparability of switching traits of gadgets from completely different producers, and so on.
Measuring the impact of delay
The measured sign will expertise two delays throughout the measurement course of, and the distinction in delay skilled by completely different indicators may have a sure impression on the measurement outcomes.
The first delay is the delay of the analog entrance finish of the oscilloscope. The distinction in delay between completely different channels of the oscilloscope is on the ps stage, and the switching strategy of the facility system on the ns stage and the us stage could be ignored.
The opposite time is the delay of the probe. The direct delay distinction of various probes is within the ns stage. Presently, it has a big impression on gadgets with quick switching speeds, particularly for SiC and GaN gadgets have a good greater impression.
We use the measurement of SiC MOSFET switching course of for example as an instance the impact of measurement delay.
Within the determine beneath, the blue waveform is the waveform obtained earlier than delay calibration is carried out on the probe (earlier than calibration), and the crimson waveform is the waveform obtained after delay calibration is carried out on the probe (post-calibration waveform).
In line with the speculation, throughout the turn-on course of, when IDS begins to rise, a voltage drop will likely be generated on the parasitic inductance of the loop, which can trigger VDS to drop. The rise of IDS and the autumn of VDS ought to begin at virtually the identical time. Within the pre-calibration waveform, when IDS begins to rise, VDS stays unchanged and begins to fall after a delay of 5.5ns. This case is clearly inconsistent with the speculation, and it may be inferred that the IDS sign leads the VDS sign right now. After calibration, this drawback was solved.
Theoretically, throughout turn-off, the height of VDS needs to be close to the zero-crossing of IDS. Within the pre-calibration waveform, VDS reaches the best worth solely after IDS zero-crosses 5.5ns. After calibration, this drawback was additionally solved.
On the identical time, we additionally sorted out the switching attribute parameters, together with: turn-on delay td(on), turn-on time tr, turn-on power Eon, turn-off delay td(off), turn-off time tf, and turn-off power Eoff. It may be seen that the turn-on delay td(on) and turn-off delay td(off) have a distinction of about 2ns earlier than and after calibration. The turn-on time tr and turn-off time tf are virtually the identical earlier than and after calibration. The turn-on power Eon earlier than calibration is 395.31uJ in comparison with 147.53 after calibration. The uJ is 1.67 occasions bigger, and the off-energy Eoff of 20.28uJ earlier than calibration is 71.3% smaller than 70.54uJ after calibration.
It may be seen that the delay has a really apparent impression on the evaluation of the switching traits of the system and the calculation of parameters. Earlier than measuring, we are able to use the next 4 strategies to carry out delay calibration.
Technique 1: Concurrently measure the oscilloscope’s personal sq. wave sign
Calibrating the delay distinction between completely different voltage probes may be very easy, simply measure the identical voltage sign on the identical time, after which calibrate based on the measurement consequence.
We will use the sq. wave sign that comes with the oscilloscope, normally on the facet panel or entrance panel of the oscilloscope. It may be seen that though each probes are measuring the oscilloscope’s personal sq. wave, the delay of the waveform displayed on the oscilloscope display is 5.6ns forward of the 1-channel measurement channel forward of the 2-channel measurement channel. Then we are able to set the delay of channel 1 to -5.6ns within the channel setting menu of the oscilloscope, or set the delay of channel 2 to +5.6ns to finish the calibration.
Technique 2: The oscilloscope’s personal operate calibration
For a hard and fast sort of voltage or present probe, the delay is principally mounted, and the delay calibration could be carried out straight so long as the probe mannequin is understood. Now the features of the oscilloscope have gotten an increasing number of highly effective, and the mannequin of the probe could be recognized via the interface of the probe, in order that the oscilloscope can straight and routinely calibrate the system delay worth.
Technique 3 Time-lapse Calibration Fixture
Following the concept of measuring the identical sign on the identical time to calibrate the delay distinction of various voltage probes in Technique 1, and measuring the voltage and present indicators that change on the identical time, the delay distinction between the voltage probe and the present probe could be calibrated. Many oscilloscope producers have launched voltage and present probe delay calibration fixtures based mostly on this concept, which is handy for engineers to make use of straight with out having to make their very own calibration sources. For instance, Tektronix’s deskew pulse generator sign supply TEK-DPG and energy measurement offset correction fixture 067-1686-03.
Technique 4 makes use of system switching traits
If restricted by the gear at hand, we are able to additionally calibrate by the traits of the system switching course of talked about above. In line with the speculation, the rise of IDS and the autumn of VDS ought to begin virtually on the identical time throughout the opening course of. Then we are able to carry out double-pulse check underneath completely different check situations, learn the delay between IDS and VDS throughout every turn-on course of, after which calibrate after averaging.
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