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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
VOLTAGE PRESETS
Now that the power supply has been brought to life, it’s time to see its real strength, the capability of voltage presets to simulate different problems in the power supply to test the behavior of the system being powered.
The first preset is used to supply a constant voltage to the connected device. Despite being the simplest of all presets, it does have the features common to all of them: regulated voltage down to 0 V, programmable current protection, and self-restoring short-circuit protection. You can observe the output current and power on the LCD. These features distinguish the power supply from the common solution of the embedded systems enthusiast, a simple linear voltage regulator powered from a mains-connected adapter.
The real value that the power supply offers is its ability to simulate the undesirable conditions of the embedded system’s voltage supply.
BROWN-OUT
One of the most common problems every embedded system has to deal with is short-voltage drop (brown-outs), which is usually caused by commutating large loads to the mains power lines (see Photo 2). Almost every microcontroller has a built-in brown-out detection circuit that provides an internal reset when the supply voltage drops below a certain threshold. Often, there is a need for a system-wide reset, which is where stand-alone brown-out detection ICs are used. The preset is configured with two parameters: T_BO (the duration) and V_BO (the voltage to fall to during brown-out condition).
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| Photo 2—Brown-out test: How long and how deep of a voltage drop could the circuit sustain without resetting itself? |
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