![]() ![]() You can disconnect the battery, and hold the stored energy in your hand for a “human perceptible” amount of time - seconds, minutes, even hours or days. A large capacitor charged from a battery stores the energy as a static electric charge. Capacitors are easier for many students to grasp (literally), at least in terms of energy storage. There are reasons for this, but for understanding power conversion, there is merit to starting with capacitors. Side note - A quick survey of switching regulators will reveal that the vast majority involve inductors, rather than capacitors. One such technique is “switched-capacitor” voltage conversion, and conceptually involves little more than capacitors, switches, and some form of control to the switches. ![]() This is where other techniques must be employed. Reduce a high voltage to a lower voltage any more efficiently than could be achieved with a power resistor in series with the supply, at an equivalent output current. Linear regulators have widespread application and are well deserving of their own activity, but there are some things that a linear regulator just can't do: This is done by adjusting the drive to a power transistor, such that the voltage drop across the transistor results in the correct output voltage. An LM7805 will provide a stable, 5V source when powered from a 9V battery. This particular situation can be remedied with a linear voltage regulator, supplied with a voltage higher than the regulated output voltage. But what if the only supply you have available is nominally the correct voltage, but varies over time or temperature - your 9V-battery powered op-amp circuit may work fine when you first power it up, but begin to fail in new and interesting ways as the battery voltage drifts down to 8V, 7V, 6V, 5V, etc. If you have never had a circuit fail because of a power integrity issue, it is likely because you are starting with a high-quality power supply. ![]() A high quality power supply is essential for nearly any electronic circuit. ![]()
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