The Ripple Effect in Power Supplies

Ultimately, the power supply is only part of a larger system. Therefore, besides being concerned about the effect of noise and ripple on the converter itself, we need to worry about its effect on the rest of the system. The good news is that if the system were excessively noise sensitive, no one would have touched switchers with a ten-foot pole (or a lOdB zero) in the first place. They would have been using those low-noise, power-guzzling LDOs (linear regulators) instead ... 

September 2000 Hi, I have been designing my power supply with the 2595, in continuous mode of operation for 1A of load current. I am expecting that my load can drop to 5mA at some points during the operation. It may stay at 5mA for a while. What effect will the low load have on my output voltage ripple, and can the output voltage oscillate ... 

The intensity I(t) of a cw laser is not completely constant, but shows periodic and random fluctuations and also, in general, long-term drifts. The reasons for these fluctuations are manifold and may, for example, be due to an insufficiently filtered power supply, which results in a ripple on the discharge current of the gas laser and a corresponding intensity modulation. Other noise sources are instabilities of the gas discharge, dust particles diffusing through the laser beam inside the resonator, and vibrations of the resonator mirrors. In multimode lasers, internal effects, such as mode competition, also contribute to noise. In cw dye lasers, density fluctuations in the dye jet stream and air bubbles are the main cause of intensity fluctuations. 

The limits of sensitivity and signal to noise are primarily determined by the lamp. One observes a change in a light level, so any unsteadiness in the lamp will be directly reflected into the signal. Lamp fluctuations set the lower limit to the size of a signal that can be observed. This is particularly true at times greater than a millisecond where the frequency of mechanical vibrations and power supply ripple on the lamp overlap the time of the measurement. Even with a perfect lamp, there is quantum noise - the effect of photon nature of... 

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