Acceptable ripple voltage is typically around 100mV peak to peak.
Understanding Acceptable Ripple
The amount of ripple voltage considered "acceptable" in a power supply output isn't a single fixed value and can vary depending on the specific application and the sensitivity of the connected electronics. However, general guidelines and typical figures provide a good starting point.
Based on common standards and practices:
- A widely cited acceptable ripple voltage is approximately 100mV peak to peak. This means the voltage fluctuation between the highest and lowest points of the ripple waveform should not exceed this value.
- Many good quality linear power supplies boast significantly better performance, often achieving ripple and noise figures of better than 10mV rms.
- Switching Mode Power Supplies (SMPS) can also achieve low ripple, with figures of 50mV or less being possible.
These lower figures (10mV rms, 50mV SMPS) represent performance often better than the barely acceptable level of 100mV peak to peak, indicating a higher quality power source.
Factors Influencing Acceptability
While 100mV peak to peak is a general benchmark for what might be tolerated in some applications, the actual acceptable level is influenced by several factors:
- Sensitivity of the Load: Highly sensitive circuits, such as precision analog instrumentation, audio equipment, or digital logic with low noise margins, require much lower ripple than, for example, a simple DC motor or heating element.
- Application Type: Different applications have varying requirements.
- Analog circuits (especially audio or measurement) are highly susceptible to ripple noise.
- High-speed digital circuits can also suffer from ripple affecting voltage levels and timing.
- Less sensitive loads might tolerate higher ripple.
- Load Current: As noted, higher current supplies are often associated with slightly higher ripple values. The design challenges increase with current.
- Peak vs. RMS vs. Noise: Ripple is often measured in peak-to-peak voltage, but noise (often higher frequency spikes) is also present and contributes to the overall unwanted signal. RMS values provide a different perspective on the total ripple/noise energy.
Here's a summary of values based on typical power supply characteristics:
| Measurement Type | Value | Context |
|---|---|---|
| Peak-to-Peak | ~100mV | Generally Acceptable |
| RMS | Better than 10mV | Good Quality Linear PS |
| Peak-to-Peak | 50mV or less | Possible for SMPS |
Why Ripple Matters
Excessive ripple can lead to various issues in electronic circuits, including:
- Noise: Introducing unwanted signals into analog circuits.
- Voltage Fluctuations: Causing instability or incorrect operation in digital logic.
- Increased Heat: Inefficient power delivery.
- Reduced Component Lifespan: Stress on components sensitive to voltage variations.
Lower ripple is almost always preferable, especially when powering sensitive or critical electronics. Designing or selecting a power supply involves balancing performance requirements against cost and complexity.
