How do you test a power supply feedback control system?

1 Basic setup

The basic setup for testing a power supply feedback control system consists of four main components: a power source, a power converter, a load, and a measurement device. The power source provides the input voltage or current to the power converter, which converts it to the desired output voltage or current using a feedback control system. The load represents the actual or simulated application that consumes the output power. The measurement device captures the input and output signals of the power converter and the feedback control system, such as voltage, current, frequency, duty cycle, and error signal. Depending on the type and complexity of the power converter and the feedback control system, you may need additional components, such as filters, transformers, isolators, or sensors.

2 Open-loop test

An open-loop test is a test that disables or bypasses the feedback control system and operates the power converter in a fixed mode. For example, you can set the input voltage or the switching frequency to a constant value and measure the output voltage or current. This test allows you to check the basic functionality and efficiency of the power converter and to identify any faults or defects in the circuit. However, it does not reflect the actual performance of the power supply feedback control system under dynamic or variable conditions.

3 Closed-loop test

A closed-loop test is a test that enables and adjusts the feedback control system and operates the power converter in a regulated mode. For example, you can set the reference signal to a desired value and measure the output voltage or current and the error signal. This test allows you to evaluate the performance and stability of the power supply feedback control system under various operating conditions and load variations. You can also change the reference signal or the load to simulate different scenarios and observe the response and behavior of the feedback control system.

4 Frequency response test

A frequency response test is a test that measures the gain and phase of the feedback control system as a function of frequency. For example, you can inject a small sinusoidal signal at the input or output of the power converter and measure the amplitude and phase shift of the output or input signal. This test allows you to analyze the frequency characteristics and the bandwidth of the feedback control system and to determine its stability margins and resonant frequencies. You can also use a frequency response test to design or tune the parameters of the feedback control system, such as proportional, integral, or derivative gains.

5 Transient response test

A transient response test is a test that measures the time-domain response of the feedback control system to a sudden change in the input or output signal. For example, you can apply a step change in the input voltage or the load current and measure the output voltage or current and the error signal. This test allows you to assess the transient performance and the speed of the feedback control system and to identify any overshoot, undershoot, ringing, or oscillation. You can also use a transient response test to optimize the trade-off between stability and performance of the feedback control system, such as damping, settling time, or rise time.

6 Robustness test

A robustness test is a test that measures the sensitivity and the tolerance of the feedback control system to variations or disturbances in the input or output signal. For example, you can apply a random or periodic noise or a harmonic distortion to the input voltage or the output current and measure the output voltage or current and the error signal. This test allows you to evaluate the robustness and the reliability of the feedback control system and to detect any instability or degradation. You can also use a robustness test to improve the resilience and the immunity of the feedback control system, such as filtering, compensation, or protection.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?