During the test, set the oscilloscope's TIME/DIV file to 10uS/div and the bandwidth to 20MHz. Read the peak-to-peak value of the output voltage displayed on the oscilloscope, which is the output ripple voltage (the peak-to-peak value including glitches is ripple + noise).

1) The input voltage of the DC regulated power supply is adjusted to the nominal voltage, and the output current is adjusted to the rated current.

2) DC regulated power supply ripple is generally expressed in peak-to-peak terms. The main testing method.

DC regulated power supply ripple and noise are AC components superimposed on the DC output voltage. The ripple and noise are measured at rated load and normal temperature. For switching AC/DC DC regulated power supplies, the output ripple voltage is a small pulse with high frequency content, so the peak-to-peak value is usually measured instead of the effective value (RMS). The measurement value is expressed in millivolt peak-to-peak value (mVp-p). For example, when the ripple peak-to-peak value of an AC/DC DC regulated power supply is 50mV, its RMS value is very low, only 5mV. However, whether it can be used in a certain system requires further consideration.

Due to the high-frequency weight contained in the measured ripples, special measurement techniques must be used to obtain accurate measurement results. In order to measure all high-frequency harmonics in the ripple peak, an oscilloscope with a bandwidth of 20MHz is generally used.

Secondly, when performing ripple measurements, great care must be taken to avoid introducing erroneous signals into the test equipment. It is necessary to remove the probe ground clamp when measuring, because in a high-frequency radiation field, the ground clamp will absorb noise like an antenna and interfere with the measurement results. Use a probe with a grounding ring to eliminate interference.

It is a method of measuring the output ripple voltage of a DC regulated power supply using a 50Ω coaxial cable. The coaxial cable connects directly to the oscilloscope. To reduce noise, an aluminum or copper ground plate should be used during measurements. The measured value is 1/2 of the actual value.

Using the double-grain line measurement method

Place the DC regulated power supply 25mm above the ground plate. The ground plate is made of aluminum or copper plate. The output common terminal and AC input ground terminal of the DC regulated power supply are directly connected to the ground plate. The ground wire should be very thick and no longer than 50mm.

DC regulated power supply ripple and noise are AC components superimposed on the DC output voltage. The ripple and noise are measured at rated load and normal temperature. For switching AC/DC DC regulated power supplies, the output ripple voltage is a system of small pulses with high frequency weight.