How to test the switching frequency of a switching power supply?
The switching frequency of a switching power supply refers to the frequency at which the power supply switches between on and off, and is one of the important parameters for evaluating the performance and reliability of a switching power supply. Switching frequency can control the magnitude of output current and improve stability. In addition, a high switching frequency can reduce losses and improve the efficiency of the switching power supply. However, the higher the switching frequency, the better. As the switching frequency increases, electromagnetic interference and noise will also increase. Therefore, it is necessary to choose the appropriate switching frequency according to the application scenario and requirements.
Testing method for switching frequency
The switching frequency test calculates the frequency by measuring the switching time and interval time of the switching power supply. Generally, the calculation formula is:
Switching frequency=number of switching cycles/unit time
Among them, the number of switching cycles refers to the number of times the switching power supply switches per unit time.
1. Phase difference
This method detects the switching frequency of a switching power supply by measuring the phase difference of the signal
A. Input the switch signal to the oscilloscope and adjust it to X-Y mode;
B. Adjust the trigger level and trigger mode of the oscilloscope to display the switch signal as a diagonal line;
C. Turn on the power to start the test, observe the diagonal line, measure the switch time and interval time.
2. Pulse counting
A. Input switch signal to pulse counter;
B. Start testing, read and record the number of pulses within a certain period of time;
C. Obtain the switching frequency of the switching power supply based on the number of pulses and testing time.
3. Oscillators
A. Input the switch signal to the oscillator and adjust the oscillator frequency to match the switch frequency;
B. Input the output signal of the oscillator to the frequency counter;
C. Start measuring, observing and recording the count values within a certain period of time;
D. Determine the switching frequency of the switching power supply based on the count value and testing time.
