ripple voltage[′rip·əl ‚vōl·tij]
The time-varying part of a voltage that is ideally time-invariant. Most electronic systems require a direct-current voltage for at least part of their operation. An ideal direct-current voltage is available from a battery, but batteries are impractical for many applications. To obtain a direct-current voltage from the alternating-current power mains requires using some type of power supply.
A typical linear power supply system configuration (see illustration) consists of a transformer to change the voltage at the mains to the desired level, a rectifier to convert the alternating-current input voltage v1 to a pulsating direct-current voltage v2, followed by a low-pass filter. The output voltage vout of the filter consists of a large direct-current voltage with a superimposed alternating-current voltage. This remaining superimposed alternating-current voltage is called the ripple voltage.
Practical linear power supplies often include a voltage regulator between the low-pass filter and the load. The voltage regulator is usually an electronic circuit that is specifically designed to provide a very stable dc output voltage even if large variations occur in the input. Nonlinear power supplies, which are often termed switching power supplies or switched-mode power supplies, are becoming increasingly popular as a practical alternative for producing a low-ripple dc output. See Electronic power supply, Rectifier