AC/DC electronic loadAs the core equipment for power testing, it can accurately evaluate power performance by simulating real load conditions. Its typical application modes include constant current (CC), constant voltage (CV), constant resistance (CR), constant power (CP), and dynamic load mode, suitable for multiple scenarios such as battery testing, power verification, and industrial equipment aging. The following analysis will be conducted from three aspects: principles, application scenarios, and practical skills:
1、 Constant current mode (CC): Battery discharge and power current limiting test
principle
In constant current mode, electronic loads adjust the conductivity of internal power devices (such as MOSFETs) to maintain the input current at the set value regardless of voltage changes. If the voltage of the tested power supply exceeds the allowable range of the load, the overvoltage protection mechanism will trigger and turn off the input.
Typical application scenarios
Battery capacity test: Discharge at a constant current, record the voltage drop curve over time, and calculate the stored energy of the battery. For example, the 18650 lithium-ion battery is discharged at 0.5C (1250mA) to a cut-off voltage of 2.5V, and the capacity is calculated based on the discharge time.
Power supply current limiting capability verification: Test the current limiting characteristics of the power supply when overloaded. For example, set the power supply to the highest voltage, gradually reduce the load resistance, and observe whether the output current is stable within the preset value (such as 5A) to avoid damaging the tested equipment.
Practical skills
Range selection: The current setting should select a low range within the overlapping area of the load range to improve resolution. If the set value exceeds the range, the load will automatically adjust to the maximum value within the range.
Cut off voltage protection: Set the discharge cut-off voltage (such as 2.5V) to prevent battery damage caused by over discharge.
2、 Constant Voltage Mode (CV): Verification of Power Output Stability
principle
In constant voltage mode, the load controls the power supply voltage at the set value by consuming current, while setting current limits. When the output current reaches the limit value, the load automatically switches to constant current mode and the output voltage drops.
Typical application scenarios
Charging pile test: Simulate the battery charging process and verify the current limiting ability of the charging pile during the constant voltage stage (such as 4.2V).
LED driver test: Keep the output voltage of the driver stable, observe the current changing with the load, and evaluate the dimming performance of the driver.
Practical skills
Current limit setting: Set reasonable current limits based on the output capacity of the tested power supply to avoid load overload.
Voltage stability monitoring: Use a multimeter or oscilloscope to monitor output voltage fluctuations and ensure they meet standards (such as ± 1%).
3、 Constant Resistance Mode (CR): Simulating Linear Load and Slow Start Test
principle
In constant resistance mode, the current consumed by the load is proportional to the input voltage, simulating pure resistance characteristics. The resistance value can be programmed in three ranges: high, medium, and low, and the load automatically selects the range with the highest resolution.
Typical application scenarios
Communication power supply slow start test: Simulate the linear load characteristics of the power supply during startup, and verify whether the output voltage rise time meets the specifications.
Load testing of automotive thermostat: Simulate the current consumption of the thermostat at different voltages to evaluate its control accuracy.
Practical skills
Range matching: Select the appropriate resistance range based on the voltage range of the tested power supply to avoid errors caused by range overflow.
Dynamic response observation: Use an oscilloscope to capture voltage/current transient changes and analyze power response speed.
4、 Constant Power Mode (CP): UPS Battery and DC-DC Converter Testing
principle
In constant power mode, the load adjusts the input current according to the set power value, so that the product of input voltage and current remains constant. This mode is commonly used to simulate the power consumption changes during battery voltage decay.
Typical application scenarios
UPS battery testing: Simulate the automatic adjustment of current when the voltage drops during battery discharge to verify the continuous power supply capability of UPS under low voltage.
DC-DC converter efficiency test: Keep the input power constant (such as 85W), and measure whether the converter efficiency is stable at 97% or above by changing the input voltage (such as 18V → 9V).
Practical skills
Power range selection: Choose the appropriate load model (such as 0-1000kW) based on the power of the tested equipment to avoid overload.
Efficiency calculation: By measuring the input/output voltage and current, calculate the converter efficiency (output power/input power x 100%).
5、 Dynamic Load Mode: Transient Response Test of Power Supply
principle
The dynamic load mode simulates the transient response capability of a power supply in actual use by programming to output rapidly changing load curves (such as pulses and steps).
Typical application scenarios
Server power test: Simulate the transient switching of the server from low power consumption (50% load) to high power consumption (100% load), and observe whether the output voltage fluctuation is within the allowable range (such as ± 15mV).
Motor driver testing: Simulate the current surge during motor startup to verify the overcurrent protection function of the driver.
Practical skills
Waveform settings: Use the built-in waveform library of the load (such as pulse, slope) to generate dynamic loads, or customize waveforms through SCPI commands.
Response time measurement: Use an oscilloscope to capture voltage transients and measure the time it takes for the power supply to recover from load changes to stability (e.g.<50 μ s).