What Is Electronic Load?
An Electronic Load is a device that is connected to the device under test and functions as a load resistor.
Conventionally, a resistor was connected to the device under test and used as the load, but the resistor had to be replaced every time the resistance value was changed. The advantage of an Electronic Load is that the load size can be set arbitrarily.
By using an external controller, the load setting can be switched at high speed. In addition, there are functions such as constant-current mode, in which a constant current is applied from the device under test, and constant-voltage mode, in which the output voltage of the device under test is maintained at a constant level, making it suitable for a variety of measurements and tests.
Applications of Electronic Loads
Electronic Loads are used for performance evaluation tests and product inspections of electronic circuits, power supplies, batteries, and other devices. Specifically, the following are some of the uses of electronic loads:
- Driving capability of Electronic Loads in electronic circuits.
- Load characteristic testing of power supplies.
- Charge/discharge testing of batteries.
In addition, since the load can be controlled by an external controller, it can be used to automate testing, such as by changing the load conditions to suit the purpose.
Functions of Electronic Load
Electronic Load has a built-in amplifier composed of a bipolar transistor or FET that controls the current (load current) drawn into it. The characteristic functions are described below.
1. Power Consumption/Conversion Method
The method of power consumption and conversion depends on the type of Electronic Load.
Thermal Conversion Type Electronic Load
The power consumed in Electronic Load is converted into heat by the semiconductor elements that make up the amplifier. This is apparently the same effect as when current flows through a resistor, but since the semiconductor elements generate heat, a heat dissipation mechanism is required.
Power Regenerative Electronic Load
Electric power input into an Electronic Load is converted into alternating current by an inverter. Since the converted current is returned to the power distribution network, power consumption is small and heat dissipation is relatively simple. However, since the regenerated power energy is returned to the power grid, it is limited to environments where grid-connected operation is possible.
2. Electronic Load Operating Modes
In general, Electronic Loads are equipped with the following four modes, and the most appropriate mode is selected according to the purpose of the test:
Constant Current Mode
In this mode, the Electronic Load operates with a set constant current, regardless of its input voltage. The Electronic Load is adapted so that the load current remains constant even when the output voltage of the device under test fluctuates.
Constant Resister Mode
In this mode, the set resistance value is held constant like a fixed resistance. It is characterized by maintaining the set resistance value except during the transient period immediately after power-on. This mode is useful for conducting capacity tests on batteries, star-tup tests for electronic equipment, and other scenarios where load current needs to vary linearly with input voltage.
Constant Voltage Mode
This mode maintains the output voltage of the device under test at a constant value. When the output voltage of the device under test fluctuates, the Electronic Load changes the load current to maintain a constant output voltage. As a result, the output voltage of the device under test remains constant, although the load current fluctuates.
It is often used for testing fuel cells and battery chargers, among other. In battery charger testing, complex battery voltage behavior can be reproduced and tested with Electronic Loads.
Constant Power mode
In this mode, the Electronic Load works to consume the set power. First, the voltage of the device under test is measured, the current value is calculated based on that voltage and the set power value, and the current is drawn accordingly.
How to Select an Electronic Load
Electronic Loads are indispensable in the development and production of power sources such as power supplies and batteries when testing the performance of each device. The following are some considerations when selecting an Electronic Load device:
1. Power Capacity and Withstand Voltage
If the device under test is a power supply, it should, in principle, have a power capacity that covers its maximum output power. The withstand voltage specification must also be greater than or equal to the voltage that may actually be applied to the device.
2. Minimum Voltage That an Electronic Load Device Can Handle
Electronic Loads are generally difficult to use in the lower voltage range, and the minimum voltage that an Electronic Load can handle is called the minimum operating voltage. As mentioned above, Electronic Loads control the current that flows through an amplifier composed of a bipolar transistor or FET. Therefore, if the voltage is below the voltage at which that amplifier operates, the Electronic Load will not operate properly.
As a result, the current cannot be drawn at a lower voltage than a certain voltage. That is, if the voltage at both ends of the Electronic Load is lower than the minimum operating voltage, it will not operate.
3.Ambient Temperature and Time
For Electronic Loads, attention should be paid to the specifications of the ambient temperature that guarantees the maximum load. In particular, it must be taken into account that thermally-converted Electronic Loads are limited to use at high temperatures because the ambient temperature rises due to their own heat generation.
In addition, there may be a limit to the time that the maximum load can be maintained, so it is necessary to check the descriptions in catalogs and spec sheets in advance.