Switched Mode Power Supply Output Monitoring

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The global Switched Mode Power Supply (SMPS*) market has been increasing over the years and is expected to grow at a Compound Annual Growth Rate (CAGR) of 2% from 2020 to 2027.

SMPS manufacturers are differentiating themselves from their competitors by offering new models that are more efficient in power usage and power conversion, more lightweight and compact size to meet rising demand. Engineers need to perform complex measurement test to ensure the reliability, stability, compliance, and safety of the new SMPS design.

* A power supply that stabilizes the output by controlling the on / off time ratio of semiconductor switch elements.


There are many tests needed for SMPS design, such as power quality, inrush current, and MOSFET switching testing. One of the key tests is to monitor and record the SMPS output current characteristics when connected to different loads at a high sampling rate for a long period of time. Any change in output current due to the dynamic load conditions is monitored and saved for further analysis. To perform this test, engineers need an instrument that can meet the following requirements:

lSMPS output voltage and current measurement
lIsolated input channels
lHigh A/D convertor resolution 
lHigh speed data sampling rate
lLong period of recording time (a few minutes to an hour)
lData can be saved easily to the instrument internal storage


Solution and benefit

Yokogawa DL950 ScopeCorder is a standalone instrument with the following capabilities that meet user’s requirements.

lIsolated input modules

Each channel is isolated from others. The 4ch 10MS/s 16bit resolution module (720256) can be used with the DL950.

lHigh sampling rate

The DL950 supports the new high speed module, 2ch 200MS/s 14bit (720212).

lVarious Math and Analysis functions

The DL950 can calculate various parameters, such as frequency, period, and RMS in real time. In addition, it has power and harmonic analysis function (/G05 option).


The DL950 captures SMPS output current data over a long period of time with high sampling rate. The long time data is easily saved to the instrument’s internal SSD memory. The DL950 can be used with a high resolution and high voltage module whose channels are isolated from each other.

The DL950 can be used as a normal oscilloscope to conduct other tests such as power quality, inrush current, and MOSFET switching testing (amplitude, duty cycle, frequency). Also, it can be used as a recorder by switching oscilloscope/recorder mode. Users can use the DL950 in a measuring instrument mode they are familiar with.

New Modules

High-speed 200MS/s 14bit Isolated Module 720212

Number of channels: 2

Sample rate: 200MS/s

Bandwidth: DC to 40 MHz

Max. input voltage:

1000 V(DC+ACpeak)*

Resolution: 14 bit

4CH 10MS/s 16bit Isolated Module

Number of channels: 4

Sample rate: 10MS/s

Bandwidth: DC to 3 MHz

Max. input voltage:

600 V(DC+ACpeak)*

Resolution: 16 bit