Application Note- 300

What is an Electronic Load?

Loads can be resistive, inductive, or capacitive. Real load behavior is typically more complex. They can be dynamic, constant current, constant voltage, crest factor, power factor or short circuit loads, etc. Prodigit DC Electronic Load can emulate constant current (CC), constant resistance (CR), constant voltage (CV), Dynamic and short circuit load; Prodigit AC Electronic Load can emulate constant current (CC),constant resistance(CR),crest factor (CF),power factor(PF)and short circuit load. Prodigit's Electronic Loads use Active components (such as Operation Amplifier and Power MOSFET) to sink power from power source. All Prodigit AC & DC Electronic Loads are equipped with Voltage/Current meter,GPIB (IEEE-488), RS-232C interface. The load can be controlled by software program, and Voltage/Current can be read back via GPIB/RS232 interface. These important features make Automatic Test System (ATE) integration more user friendly and flexible.

Following are definitions and applications for an Electronic Load's operating mode.

1. Constant Current (CC) mode: (AC/DC) Definition:

In the constant current mode Prodigit's Electronic Loads will sink a current in accordance with the programmed value regardless of input voltage.

Application:

The CC mode can be used to test voltage sources, and load regulation of DC & AC power supply. Load regulation is a power supply's ability to provide a stable output voltage under load variations. It is specified as a percentage deviation from normal output at a fixed input voltage and is calculated using the following formula:

2. Constant Resistance (CR) mode: (AC/DC) Definition:

In the constant resistance mode Prodigit's Electronic Loads will sink a current linearly proportional to the input voltage in accordance with the programmed resistance.

Application:

The CR mode can be used to test either voltage or current sources, and is normally used in testing power source start up and current limit.

3. Constant Voltage (CV) mode: (DC) Definition:

In the constant Voltage mode Prodigit's Electronic Loads will sink enough current (if available) to control the source voltage to the programmed value.

Application:

The CV mode can be used to test current source. It is frequently used to test current limit characteristic of power supplies. It can also be used for testing battery chargers where CV mode load can emulate a battery's terminal voltage.

4. Dynamic Load: (DC) Definition:

Dynamic load operation causes Prodigit's Electronic Loads to periodically switch between two load levels. A power supply's regulation and transient response can be evaluated by monitoring its output voltage under varying combination of Load High/Low current levels, High/Low current level duration, and Rise/Fall slew rate. The 3310 series Electronic Load offer CC mode only when using Dynamic mode.

Application:

Dynamic mode can be used to test the transient response of a power supply. Most commonly used loads are dynamic; for example, in a computer the disk drive draws varying amounts of current. The dynamic mode can simulate this condition.