What does DC power supply mean
A DC power supply is a device that maintains a constant voltage and current in a circuit. Such as dry batteries, storage batteries, DC generators, etc.
The DC power supply has two electrodes, positive and negative. The potential of the positive electrode is high, and the potential of the negative electrode is low. When the two electrodes are connected to the circuit, a constant potential difference can be maintained between the two ends of the circuit, thereby forming an external circuit from the positive electrode to the negative electrode. negative current. A DC power supply is an energy conversion device that converts other forms of energy into electrical energy supply circuits to maintain a steady flow of current.
A constant water flow cannot be maintained solely by the difference in water level, but a constant water level difference can be maintained by means of a water pump to continuously send water from a low place to a high place to form a steady water flow. Similar to this, the electrostatic field generated by the charge alone cannot maintain a constant current, but with the help of a DC power supply, the non-electrostatic effect (referred to as "non-electrostatic force") can be used to move the positive charge from the negative electrode with a lower potential. Return to the positive electrode with higher potential through the power supply to maintain the potential difference between the two electrodes, thus forming a stable current.
The non-electrostatic force in a DC power supply is directed from the negative pole to the positive pole. When the DC power supply is connected to the external circuit, a current from the positive pole to the negative pole is formed outside the power supply (external circuit) due to the promotion of the electric field force. And inside the power supply (internal circuit), the action of non-electrostatic force makes the current flow from the negative pole to the positive pole, so that the flow of charge forms a closed cycle.
An important characteristic of the power supply itself is the electromotive force of the power supply, which is equal to the work done by the non-electrostatic force when the unit positive charge moves from the negative pole to the positive pole through the interior of the power supply. When the internal resistance of the power supply is negligible, it can be considered that the electromotive force of the power supply is approximately equal in magnitude to the potential difference or voltage between the two poles of the power supply.
In order to obtain a higher DC voltage, DC power supplies are often used in series. At this time, the total electromotive force is the sum of the electromotive forces of each power supply, and the total internal resistance is also the sum of the internal resistances of each power supply. Due to the increased internal resistance, it can generally only be used in circuits that require a smaller current intensity. In order to obtain a larger current intensity, DC power supplies with equal electromotive force can be used in parallel. At this time, the total electromotive force is the electromotive force of a single power supply, and the total internal resistance is the parallel value of the internal resistance of each power supply.
There are many types of DC power sources. In different types of DC power sources, the nature of the non-electrostatic force is different, and the process of energy conversion is also different. In chemical batteries (such as dry batteries, storage batteries, etc.), the non-electrostatic force is a chemical action associated with the dissolution and deposition of ions. When a chemical battery is discharged, chemical energy is converted into electrical energy and Joule heat in a thermoelectric power supply (such as a metal thermoelectric power supply). Couple, semiconductor thermocouple), the non-electrostatic force is the diffusion effect associated with the temperature difference and the concentration difference of electrons. When the thermoelectric power supply provides power to the external circuit, the heat energy is partially converted into electrical energy. In the DC generator, the non-electrostatic force is electromagnetic induction. When the DC generator supplies power, the mechanical energy is converted into electrical energy and Joule heat. In photovoltaic cells, the non-electrostatic force is the function of the photovoltaic effect. When the photovoltaic cell is powered, light energy is converted into electrical energy and Joule heat.
