Electronic load

An electronic load is a device or assembly that is used as a replacement for a conventional (ohmic) load resistance (input resistance, terminating resistance, external resistance). In the circuit diagram it is shown like a resistor component with a rectangle and is usually referred to as 'R' without an index, which stands for any unspecified load.

electronic AC load

As a counterpart to the power source , the electronic load is a current sink . While only a certain load current can be set at a certain resistance value when loading a power source with a fixed resistor, the special feature of the electronic load is that the load current can be set in a defined range, it is electronically regulated.

The power consumed by the electronic load electric power is mostly in heat converted, for cooling and removal of the exhaust fan or water cooled elements are used. Feeding back into the public power supply network is also possible under certain conditions. Electronic loads are used in various applications, especially for testing of power and control devices , batteries , fuel and solar cells , generators . AC loads are used to test transformers , uninterruptible power supplies ( UPS ), or on- board electrical systems.

The performance and equipment spectrum of these devices begins with the simplest circuits, which essentially consist of a potentiometer for setpoint adjustment and a load circuit. The load circuit is formed from a power MOSFET , for example , which converts the power consumed into heat. With advanced electronic loads, there are several modes of operation, mostly constant current, voltage, power and resistance. In addition, the ability to be controlled via analog or digital control signals from a control device such as a programmable logic controller or PC is now part of the operating scope. This means that special load types such as short-term pulse loads or certain switch-on behavior with different load profiles can be reproduced by consumers. Setpoint values and measured parameters such as input voltage and the actual load current analog or digital display or received via the control interface.

Function example

schematic circuit diagram of an electronic load

The circuit diagram opposite is intended to illustrate the functional principle of an electronic load: An emitter voltage is set with the potentiometer at the base of the transistor , so that a certain current flows through the load resistance.

If, for example, the load resistor has an ohmic resistance of and an emitter voltage of is set , which is also applied to the load resistor, a current of flows through it . ${\displaystyle R=1\,\Omega }$ ${\displaystyle U=1\,\mathrm {V} }$ ${\displaystyle I={\tfrac {U}{R}}={\tfrac {1\,\mathrm {V} }{1\,\Omega }}=1\,\mathrm {A} }$

Based on this scheme, real electronic loads can be created, which, however, have a control to stabilize the load . Stabilizing the load is often useful, e.g. B. to compensate for the temperature dependence of the resistor and the electronics.

Individual evidence

1. ↑ Power MOSFET is core of regulated-dc electronic load. In: EDN network. Retrieved May 25, 2013 .