The power supply is not just a small box; it functions as the heart of any active device, providing a consistent energy source to its components. The quality of the power supply directly influences the performance and reliability of the system it powers. To ensure that power supplies meet required standards, rigorous testing is conducted during design, manufacturing, and quality control phases. This involves using advanced electronic equipment to simulate various power supply characteristics (such as voltage regulation, stability, and noise) and verifying them before deployment.
Engineers must consider several key parameters when designing or evaluating power supplies:
1. **Input Voltage Effects on Output Voltage**
- **Absolute Voltage Regulation Coefficient (K):** Measures the change in output DC voltage (ΔU0) relative to the input voltage variation (ΔUi) at a constant load. K = ΔU0 / ΔUi.
- **Relative Voltage Regulation Coefficient (S):** Indicates the relative change in output voltage (ΔUo/Uo) compared to the relative change in input voltage (ΔUi/Ui). S = (ΔUo/Uo) / (ΔUi/Ui).
- **Grid Adjustment Rate:** Refers to the relative change in output voltage when the input voltage varies by ±10% from its rated value.
2. **Load Effects on Output Voltage**
- **Load Regulation Rate:** Measures the maximum relative change in output voltage when the load current changes from 0 to full capacity. It’s usually expressed as a percentage.
- **Output Resistance (Ro):** Calculated as Ro = |ΔUo / ΔIL|, where ΔUo is the change in output voltage and ΔIL is the change in load current.
3. **Ripple Voltage Indicators**
- **Maximum Ripple Voltage:** The peak-to-peak or RMS value of the ripple at rated output conditions.
- **Ripple Coefficient (Y%):** The ratio of the ripple RMS voltage (Urms) to the DC output voltage (Uo), expressed as Y = Urms / Uo × 100%.
- **Ripple Suppression Ratio:** The ratio of the input ripple (Ui~) to the output ripple (Uo~), indicating how well the power supply suppresses ripple.
4. **Inrush Current**
The maximum current drawn by the power supply immediately after being turned on, typically ranging from 20A to 30A.
5. **Overcurrent Protection**
Designed to protect both the power supply and the connected load from damage due to excessive current, including short circuits. The threshold is generally set between 110% and 130% of the rated current.
6. **Overvoltage Protection**
Prevents damage caused by excessive output voltage. Typically set at 130% to 150% of the rated output voltage.
7. **Undervoltage Protection**
Activates when the output voltage drops below a certain level (usually 80% to 30% of the rated voltage), shutting down the power supply and triggering an alarm.
8. **Overheating Protection**
Stops the power supply and sends an alarm if internal temperature rises beyond safe limits.
9. **Temperature Drift and Coefficients**
- **Absolute Temperature Coefficient:** The change in output voltage per degree Celsius (e.g., mV/°C).
- **Relative Temperature Coefficient:** The relative change in output voltage per degree Celsius.
10. **Drift**
A slow change in output voltage over time due to component parameter variations, even under stable input and load conditions.
11. **Response Time**
The time it takes for the power supply to stabilize after a sudden change in load current.
12. **Distortion**
Specific to AC regulators, this refers to waveform imperfections in the output.
13. **Noise**
High-frequency disturbances present in the output, often measured in peak-to-peak values.
14. **Input Noise**
External noise that may be superimposed on the input voltage, affecting the power supply's operation.
15. **Surge Protection**
Tests the power supply’s ability to withstand high-voltage surges without failure.
16. **Static Noise**
Repeated pulse-like static electricity that must not interfere with normal operation.
17. **Stability**
The maximum allowable change in output voltage under normal operating conditions.
18. **Electrical Safety Requirements (GB 4943-90)**
Includes insulation requirements, dielectric tests, leakage current limits, and safety certifications such as UL, CSA, VDE, and IEC.
19. **Radio Disturbance (GB 9254-1998)**
Limits on conducted and radiated electromagnetic interference from the power supply.
20. **Electromagnetic Compatibility (EMC) Testing**
Ensures the power supply can function properly without causing or being affected by electromagnetic interference. Includes tests for immunity to magnetic fields, electrostatic discharge, power transients, radiation, and conduction.
21. **Environmental Testing**
Evaluates the power supply’s performance under various environmental conditions, including temperature extremes, humidity, vibration, and mechanical stress.
These specifications ensure that power supplies are reliable, efficient, and safe for use in a wide range of applications, from consumer electronics to industrial systems.
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