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Feature Article
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Issue #206 September
2007
Smart Power
An Intelligent Power Supply for Embedded Systems
by Alexander Popov & Jordan Popov
Start | Hardware | Software | Calibration | Voltage Presets | Slowly Rising Voltage | Slowly Falling Voltage | Short Time Test | Periodcal Linear Voltage | Periodical Voltage Drops | Future Development | Sources & PDF
PERIODICAL LINEAR VOLTAGE
The preset can be used for different purposes. With a small period, such as the one in Photo 6, the tested circuit input capacitors can be evaluated. Do they provide enough filtering to the hum from the mains power net or to the other periodical disturbances? Since the waveform of the voltage is triangular, not sinusoidal, the introduced hum has more harmonics, providing a better test to the filtering part of the circuit than a pure sinusoidal signal.
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| Photo 6—Periodical linear voltage can be used to test the filtering efficiency of the input capacitors. |
Another application of the preset is testing the linear voltage regulator’s behavior in the entire operating range of input voltages. Some LDOs may become unstable under some conditions (input voltage and load) or stop stabilizing the input voltage, feeding it to the output! This can destroy all the integrated circuits powered by the LDO. That is why a test for voltage stability should be performed. The preset is useful for doing it.
Since it is a more complex waveform than the previous presets, this one is configured with more parameters: T_RISE, the duration of the voltage rising, T_FALL, the duration of the voltage falling, and V_FALL, the voltage to fall to.
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