How does a programmable DC power supply work?
With the continuous development of various electronic devices, they also have higher requirements for DC power supply. Compared with electronic equipment, there is no way to meet the power supply requirements with a single DC power supply, so different DC power supplies are needed. Power electronic equipment. A programmable DC power supply is one such. In production testing, the wide-range voltage output of the programmable DC power supply is suitable for testing and analyzing the characteristics of components, circuits, modules and complete machines. Today, Antai Test will introduce the working principle of programmable DC power supply.
Programmable DC Power Supply Introduction
The non-electrostatic force in a programmable DC power supply points from negative to positive. When the programmable DC power supply is connected to the external circuit, due to the force of the electric field, a current from the positive pole to the negative pole will be formed outside the power supply (external circuit). In 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 charge forms a closed loop flow.
An important characteristic of a programmable DC power supply is its electromotive force, which is equal to the work done by the non-electrostatic force when a unit of positive charge moves from negative to positive through the interior of the power supply. When the power supply provides energy to the circuit, the provided power P is equal to the product of the electromotive force E of the power supply and the current I, P=EI. Another characteristic quantity of the power supply is its internal resistance (internal resistance for short) R0. When the current through the power supply is I, the thermal power lost in the power supply (that is, the Joule heat generated per unit time) is equal to R0I.
When the positive and negative poles of the power supply are not connected, the power supply is in an open circuit state, and the potential difference between the two electrodes of the power supply is equal to the electromotive force of the power supply. In the open circuit state, there is no mutual conversion between non-electric energy and electric energy. When the load resistor is connected to the two poles of the power supply to form a closed loop, the current flowing through the power supply flows from the negative pole to the positive pole. At this time, the power EI provided by the power supply is equal to the sum of the power UI (U delivered to the external circuit (U is the potential difference between the positive and negative poles of the power supply) and the thermal power R0I lost in the internal resistance, EI=UIR0I. Therefore, when the power supply When supplying power to the load resistance, the potential difference between the two poles of the power supply is U=E-R0I.
When another power source with a larger electromotive force is connected to a power source with a smaller electromotive force, the positive pole is connected to the positive pole, and the negative pole is connected to the negative pole (for example, a DC generator is used to charge the battery pack), and the current flows from the positive pole to the negative pole in the power supply with a small electromotive force . At this time, the external input electric power UI is equal to the sum of the energy EI stored in the power supply per unit time and the thermal power R0I lost in the internal resistance, and UI=EIR0I. Therefore, when an external power supply is input to the power supply, the external voltage applied between the two poles of the power supply should be U=ER0I.
When the internal resistance of the programmable DC power supply can be ignored, it can be considered that the electromotive force of the power supply is approximately equal to the potential difference or voltage between the two poles of the power supply.
In order to obtain higher DC voltages, programmable DC power supplies are often used in series. At this time, the total electromotive force is the sum of all power supply electromotive forces, and the total internal resistance is also the sum of all power supply internal resistances. Due to the increased internal resistance, it can only be used in circuits with low current strength. In order to obtain greater current intensity, programmable DC power supplies with equal electromotive forces 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 connection value of the internal resistance of each power supply.
