A power supply may show a perfectly acceptable DC voltage on a multimeter, but that doesn’t always mean the output is truly \u201cclean.\u201d<\/p>\n\n\n\n
Hidden on top of the DC voltage can be a small unwanted AC variation called ripple voltage<\/strong>.<\/p>\n\n\n\n For example, a power supply might provide around 12V DC<\/strong>, while the actual voltage continuously moves slightly above and below 12V. That unwanted variation is ripple.<\/p>\n\n\n\n For simple circuits, a small amount of ripple may not cause noticeable problems. But in sensitive electronics, audio amplifiers, microcontrollers, communication equipment, and precision circuits, excessive ripple can create serious issues.<\/p>\n\n\n\n Let’s understand what ripple voltage is, where it comes from, how to measure it, and how to reduce it.<\/p>\n\n\n\n Ripple voltage is the remaining periodic AC component present on a DC power supply output<\/strong>.<\/p>\n\n\n\n Ideally, a DC power supply would look like this:<\/p>\n\n\n\n 12V \u2192 12V \u2192 12V \u2192 12V \u2192 12V<\/strong><\/p>\n\n\n\n In reality, the voltage may look more like:<\/p>\n\n\n\n 12V \u2192 11.8V \u2192 12.1V \u2192 11.9V \u2192 12.05V<\/strong><\/p>\n\n\n\n That small fluctuation is ripple.<\/p>\n\n\n\n In technical terms:<\/p>\n\n\n\n Ripple voltage is the unwanted AC variation remaining after AC has been converted into DC.<\/strong><\/p>\n<\/blockquote>\n\n\n\n It is usually measured as Vpp (peak-to-peak voltage)<\/strong>, mV RMS<\/strong>, or sometimes as a percentage of the DC output.<\/p>\n\n\n\n The most common source is a rectifier-based power supply<\/strong>.<\/p>\n\n\n\n The basic process looks like this:<\/p>\n\n\n\n AC Mains \u2192 Transformer \u2192 Rectifier \u2192 Filter Capacitor \u2192 Regulator \u2192 DC Output<\/strong><\/p>\n\n\n\n The rectifier converts AC into pulsating DC.<\/p>\n\n\n\n The capacitor then charges when the rectified voltage rises and discharges when the voltage falls.<\/p>\n\n\n\n This charging and discharging process produces the remaining ripple.<\/p>\n\n\n\n After rectification, the waveform is still strongly pulsating.<\/p>\n\n\n\n The capacitor fills the gaps between the peaks and produces a much smoother DC voltage.<\/p>\n\n\n\n However, the capacitor cannot hold the voltage perfectly constant.<\/p>\n\n\n\n That remaining variation is ripple voltage<\/strong>.<\/p>\n\n\n\n The filter capacitor is one of the most important components in reducing ripple.<\/p>\n\n\n\n Think of it like a small reservoir.<\/p>\n\n\n\n When the rectifier provides energy, the capacitor stores it.<\/p>\n\n\n\n When the rectified voltage drops, the capacitor releases some of its stored energy to the circuit.<\/p>\n\n\n\n So instead of the voltage falling sharply between peaks, the capacitor keeps supplying current.<\/p>\n\n\n\n However, the capacitor gradually discharges between charging peaks.<\/p>\n\n\n\n That creates the characteristic ripple waveform.<\/p>\n\n\n\n For a simple capacitor-filtered power supply, ripple can be approximately estimated using:<\/p>\n\n\n\n Vr \u2248 I \/ (f \u00d7 C)<\/strong><\/p>\n\n\n\n Where:<\/p>\n\n\n\n For a full-wave rectifier:<\/p>\n\n\n\n f = 2 \u00d7 mains frequency<\/strong><\/p>\n\n\n\n So with a 50 Hz AC supply:<\/p>\n\n\n\n Ripple frequency = 100 Hz<\/strong><\/p>\n\n\n\n For a half-wave rectifier:<\/p>\n\n\n\n Ripple frequency = 50 Hz<\/strong><\/p>\n\n\n\n Suppose a power supply has:<\/p>\n\n\n\n Then:<\/p>\n\n\n\n Vr \u2248 1 \/ (100 \u00d7 0.01)<\/strong><\/p>\n\n\n\n Vr \u2248 1V<\/strong><\/p>\n\n\n\n So the approximate ripple voltage is around 1V peak-to-peak<\/strong> under those simplified conditions.<\/p>\n\n\n\n This shows an important relationship:<\/p>\n\n\n\n Higher capacitance \u2192 Lower ripple<\/strong><\/p>\n\n\n\n Higher load current \u2192 Higher ripple<\/strong><\/p>\n\n\n\n This is one of the most important things to understand.<\/p>\n\n\n\n Imagine a power supply working at a light load.<\/p>\n\n\n\n The capacitor doesn’t need to provide much current between charging peaks, so its voltage doesn’t drop very much.<\/p>\n\n\n\n Now connect a heavier load.<\/p>\n\n\n\n The circuit demands more current.<\/p>\n\n\n\n The capacitor discharges faster.<\/p>\n\n\n\n The voltage therefore falls further before the next charging cycle.<\/p>\n\n\n\n Result:<\/p>\n\n\n\n This is why a power supply can appear stable with no load but show significant ripple when connected to a demanding circuit.<\/p>\n\n\n\n Ripple isn’t just a measurement on an oscilloscope. Too much ripple can affect the circuit itself.<\/p>\n\n\n\n In audio amplifiers, power-supply ripple can enter the amplifier’s signal path and create an unwanted 50\/100 Hz hum<\/strong> or related harmonics.<\/p>\n\n\n\n This can be especially noticeable in high-gain audio equipment.<\/p>\n\n\n\n Digital circuits may become unreliable if their supply voltage contains excessive noise or ripple.<\/p>\n\n\n\n Symptoms can include:<\/p>\n\n\n\n A regulator has to deal with the input voltage supplied to it.<\/p>\n\n\n\n Excessive ripple can increase the amount of voltage the regulator must continuously dissipate, potentially increasing heat.<\/p>\n\n\n\n Precision amplifiers, sensors, ADCs and measurement circuits can be particularly sensitive to power-supply noise.<\/p>\n\n\n\n Even when the circuit continues operating, excessive ripple can reduce the quality and stability of the overall system.<\/p>\n\n\n\n Not exactly.<\/p>\n\n\n\n They are related, but ripple and noise are not identical<\/strong>.<\/p>\n\n\n\n Ripple<\/strong> is generally a periodic variation associated with the power conversion process.<\/p>\n\n\n\n Noise<\/strong> is a broader term covering unwanted electrical disturbances, which may come from switching circuits, EMI, digital electronics, transformers, motors and many other sources.<\/p>\n\n\n\n A power supply can therefore have:<\/p>\n\n\n\n DC + Ripple + High-Frequency Noise<\/strong><\/p>\n\n\n\n This distinction becomes particularly important when designing modern switching power supplies.<\/p>\n\n\n\n The best instrument for observing ripple is an oscilloscope<\/strong>.<\/p>\n\n\n\n A multimeter can measure DC voltage, but it may not clearly show the actual ripple waveform.<\/p>\n\n\n\n With an oscilloscope, you can see:<\/p>\n\n\n\n If you’re checking a DC power supply, connect the oscilloscope across the output and observe the AC component.<\/p>\n\n\n\n For low-level ripple measurements, proper probing technique is important. Long ground leads can themselves pick up unwanted noise and make the waveform appear worse than it really is.<\/p>\n\n\n\n Some multimeters have an AC voltage mode<\/strong>, but this isn’t always reliable for measuring small ripple on top of a DC voltage.<\/p>\n\n\n\n The result depends on the meter’s design and bandwidth.<\/p>\n\n\n\n For example, a power supply may have:<\/p>\n\n\n\n 12V DC + 50mV ripple<\/strong><\/p>\n\n\n\n A basic multimeter may simply display something close to 12V and hide the details.<\/p>\n\n\n\n An oscilloscope gives you a much clearer picture.<\/p>\n\n\n\n There are several ways to reduce ripple.<\/p>\n\n\n\n Increasing the value of the smoothing capacitor generally reduces ripple.<\/p>\n\n\n\n For example:<\/p>\n\n\n\n 2200 \u00b5F \u2192 4700 \u00b5F \u2192 10,000 \u00b5F<\/strong><\/p>\n\n\n\n However, bigger isn’t automatically better.<\/p>\n\n\n\n The capacitor must have suitable:<\/p>\n\n\n\n A regulator can significantly reduce the remaining ripple.<\/p>\n\n\n\n Common linear regulators include the 78xx family<\/strong>, such as:<\/p>\n\n\n\n A properly designed regulator stage can provide a much cleaner DC output than a capacitor-filtered rectifier alone.<\/p>\n\n\n\n For demanding applications, designers may use:<\/p>\n\n\n\n Capacitor \u2192 Resistor \u2192 Capacitor<\/strong><\/p>\n\n\n\n This is known as an RC filter<\/strong>.<\/p>\n\n\n\n Another option is:<\/p>\n\n\n\n Capacitor \u2192 Inductor \u2192 Capacitor<\/strong><\/p>\n\n\n\n known as an LC filter<\/strong>.<\/p>\n\n\n\n These techniques can provide additional ripple attenuation.<\/p>\n\n\n\n The ESR, or Equivalent Series Resistance<\/strong>, of a capacitor affects its ability to filter changing currents.<\/p>\n\n\n\n Lower ESR can be beneficial in many power-supply applications, particularly where high ripple currents or switching frequencies are involved.<\/p>\n\n\n\n However, the correct capacitor depends on the circuit design; simply choosing the lowest-ESR capacitor is not always the complete answer.<\/p>\n\n\n\n Two capacitors can have the same capacitance and voltage rating but behave differently in a real power supply.<\/p>\n\n\n\n For example:<\/p>\n\n\n\n 10,000 \u00b5F 25V<\/strong><\/p>\n\n\n\n doesn’t tell you everything.<\/p>\n\n\n\n Other specifications can include:<\/p>\n\n\n\n For power-supply applications, ripple-current capability<\/strong> and ESR<\/strong> can be particularly important.<\/p>\n\n\n\n A capacitor that is poorly suited to the application may heat up, lose performance, or fail prematurely.<\/p>\n\n\n\n Don’t confuse ripple voltage<\/strong> with ripple current<\/strong>.<\/p>\n\n\n\n Ripple voltage is the unwanted voltage variation across the power supply.<\/p>\n\n\n\n Ripple current is the AC component of current flowing through a capacitor or other component.<\/p>\n\n\n\n When ripple current flows through a capacitor’s ESR, it generates heat.<\/p>\n\n\n\n That is why capacitor datasheets specify a maximum ripple-current rating<\/strong>.<\/p>\n\n\n\n Exceeding that rating can shorten capacitor life.<\/p>\n\n\n\n In practical electronics, achieving absolutely zero ripple is extremely difficult.<\/p>\n\n\n\n Even high-quality power supplies contain some amount of:<\/p>\n\n\n\n The goal is not always to eliminate every unwanted signal.<\/p>\n\n\n\n The goal is to reduce it to a level that is safe and acceptable for the application<\/strong>.<\/p>\n\n\n\n A power supply for a simple relay circuit may tolerate considerably more ripple than a precision measurement system.<\/p>\n\n\n\n Ripple behaves differently depending on the type of power supply.<\/p>\n\n\n\n Typical structure:<\/p>\n\n\n\n Transformer \u2192 Rectifier \u2192 Capacitor \u2192 Linear Regulator<\/strong><\/p>\n\n\n\n The main ripple is often associated with the AC mains frequency and its rectified harmonics.<\/p>\n\n\n\n Typical structure:<\/p>\n\n\n\n Rectifier \u2192 Switching Stage \u2192 Transformer\/Inductor \u2192 Rectifier \u2192 Filter \u2192 Output<\/strong><\/p>\n\n\n\n Switching power supplies can have high-frequency ripple and switching noise.<\/p>\n\n\n\n They can be extremely efficient, but filtering and PCB layout become very important.<\/p>\n\n\n\n Ripple voltage is one of those problems that can remain hidden until you know where to look.<\/p>\n\n\n\n Your multimeter may show:<\/p>\n\n\n\n 12.0V DC<\/strong><\/p>\n\n\n\n But an oscilloscope could reveal that the supply is actually fluctuating continuously.<\/p>\n\n\n\n Understanding ripple helps you choose the correct:<\/p>\n\n\n\n And most importantly, it helps you understand why a circuit that has the \u201ccorrect voltage\u201d can still behave incorrectly<\/strong>.<\/p>\n\n\n\n More load \u2192 More ripple<\/strong><\/p>\n\n\n\n More capacitance \u2192 Generally less ripple<\/strong><\/p>\n\n\n\n Better filtering \u2192 Cleaner DC<\/strong><\/p>\n\n\n\n Poor capacitor selection \u2192 Possible reliability problems<\/strong><\/p>\n\n\n\n Ripple voltage is the unwanted AC variation remaining on a DC power supply output after rectification and filtering.<\/p>\n\n\n\n It is commonly caused by the charging and discharging of filter capacitors in rectifier-based power supplies.<\/p>\n\n\n\n Generally, yes. Increasing capacitance reduces the voltage drop between charging peaks, resulting in lower ripple, assuming the capacitor is suitable for the circuit.<\/p>\n\n\n\n Excessive ripple can cause noise, instability, overheating, measurement errors and other performance problems depending on the circuit.<\/p>\n\n\n\n An oscilloscope is generally the best tool because it allows you to see both the ripple amplitude and waveform.<\/p>\n\n\n\n A power supply isn’t truly \u201cgood\u201d just because the multimeter shows the correct voltage.<\/strong><\/p>\n\n\n\n The quality of that voltage matters too.<\/p>\n\n\n\n The next time you troubleshoot an unstable circuit, don’t only ask:<\/p>\n\n\n\n \u201cIs the voltage correct?\u201d<\/strong><\/p>\n\n\n\n Ask:<\/p>\n\n\n\n \u201cHow clean is the voltage?\u201d<\/strong><\/p>\n\n\n\n That small difference can lead you straight to the real problem.<\/p>\n","protected":false},"excerpt":{"rendered":" A power supply may show a perfectly acceptable DC voltage on a multimeter, but that doesn’t always mean the output is truly \u201cclean.\u201d Hidden on top of the DC voltage can be a small unwanted AC variation called ripple voltage. For example, a power supply might provide around 12V DC, while the actual voltage continuously…<\/p>\n","protected":false},"author":1,"featured_media":1513,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[344,346,356],"tags":[351,494,347,357],"class_list":["post-1512","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-knowledge-based","category-voltage","tag-blog","tag-blog-capkit","tag-knowledge","tag-ripple-voltage"],"_links":{"self":[{"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/posts\/1512","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/capkit.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1512"}],"version-history":[{"count":1,"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/posts\/1512\/revisions"}],"predecessor-version":[{"id":1514,"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/posts\/1512\/revisions\/1514"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/capkit.in\/index.php?rest_route=\/wp\/v2\/media\/1513"}],"wp:attachment":[{"href":"https:\/\/capkit.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1512"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/capkit.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1512"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/capkit.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1512"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\n\n\n\nWhat Exactly Is Ripple Voltage?<\/h2>\n\n\n\n
\n
\n\n\n\nWhere Does Ripple Come From?<\/h2>\n\n\n\n
Without a Filter Capacitor<\/h3>\n\n\n\n
With a Filter Capacitor<\/h3>\n\n\n\n
\n\n\n\nWhy Is the Capacitor So Important?<\/h2>\n\n\n\n
\n\n\n\nThe Basic Ripple Voltage Formula<\/h2>\n\n\n\n
\n
Example<\/h3>\n\n\n\n
\n
\n\n\n\nWhat Happens When the Load Increases?<\/h2>\n\n\n\n
More load \u2192 More ripple<\/strong><\/h3>\n\n\n\n
\n\n\n\nWhy Excessive Ripple Is a Problem<\/h2>\n\n\n\n
1. Audio Noise<\/h3>\n\n\n\n
2. Microcontroller Problems<\/h3>\n\n\n\n
\n
3. Voltage Regulator Heating<\/h3>\n\n\n\n
4. Sensitive Analog Circuits<\/h3>\n\n\n\n
5. Reduced Circuit Performance<\/h3>\n\n\n\n
\n\n\n\nRipple Voltage vs Noise: Are They the Same?<\/h2>\n\n\n\n
\n\n\n\nHow Do You Measure Ripple Voltage?<\/h2>\n\n\n\n
\n
Typical Measurement<\/h3>\n\n\n\n
\n\n\n\nCan a Multimeter Measure Ripple?<\/h2>\n\n\n\n
\n\n\n\nHow Can You Reduce Ripple Voltage?<\/h2>\n\n\n\n
1. Increase Filter Capacitance<\/h3>\n\n\n\n
\n
\n\n\n\n2. Use a Voltage Regulator<\/h3>\n\n\n\n
\n
\n\n\n\n3. Use Additional Filtering<\/h3>\n\n\n\n
\n\n\n\n4. Use Low-ESR Capacitors Where Appropriate<\/h3>\n\n\n\n
\n\n\n\nWhy Capacitor Quality Matters<\/h2>\n\n\n\n
\n
\n\n\n\nWhat Is Ripple Current?<\/h2>\n\n\n\n
\n\n\n\nIs Zero Ripple Possible?<\/h2>\n\n\n\n
\n
\n\n\n\nRipple in Linear vs Switching Power Supplies<\/h2>\n\n\n\n
Linear Power Supply<\/h3>\n\n\n\n
Switching Power Supply<\/h3>\n\n\n\n
\n\n\n\nThe Big Takeaway<\/h2>\n\n\n\n
\n
Remember:<\/h3>\n\n\n\n
\n\n\n\nFrequently Asked Questions<\/h2>\n\n\n\n
What is ripple voltage in a power supply?<\/h3>\n\n\n\n
What causes ripple voltage?<\/h3>\n\n\n\n
Does a larger capacitor reduce ripple?<\/h3>\n\n\n\n
Can ripple damage electronics?<\/h3>\n\n\n\n
What is the best way to measure ripple?<\/h3>\n\n\n\n
\n\n\n\nFinal Thought<\/h2>\n\n\n\n