Bode 100 Application Note
直流模块电源环路稳定性分析DC/DC Converter Stability Measurement
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Table of Contents
1Introduction (3)
泥条盘筑2Measurement Setup (4)
2.1 The Circuit under Test (4)
2.2 Selecting the Injection Point (5)
2.3 Connecting the Bode 100 (6)
2.4 Pha Margin and Gain Margin (8)
3Device Configuration (9)
4Measurement & Results (10)
4.1 Calibration (10)
4.2 Shaped Level (12)
4.3 Injection Level (14)
4.4 Supply Voltage Influence (15)
4.5 Load Current Influence (15)
5Conclusion (16)
1 Introduction
足智多谋的反义词In this application note we show how to analyze the stability respectively the control loop behavior of a step-down DC/DC converter.
To minimize the influence of supply voltage variations and load changes on the output voltage of a DC/DC converter, a compensating controller is necessary. The quality of this control circuit determines the stability and dynamic respon of the entire DC/DC converter system. The following pages show you how you can measure the loop respon of such control systems using the Bode 100 vector network analyzer in combination with the B-WIT 100 wideband injection transformer.
For the characterization of the loop we measure the open loop gain by using the voltage injection method. This method is commonly ud to analyze the stability of voltage regulators such as switched mode power supplies.
The following points are discusd in this document:早点大全各种做法
洗衣机清理方法
∙How to choo the correct injection point to measure the loop gain
∙Determining gain margin and pha margin from the frequency respon
∙How do supply voltage and load current influence the systems dynamics
∙Using the shaped level feature of the Bode 100 to improve the measurement results
2 Measurement Setup
2.1 The Circuit under Test
The demo board 481A is a step-down converter featuring the LT1976. The output is optimized for at
a load current of . The following figure shows the schematics of the demo board 481A. Detailed information on the demo circuit can be found at
Figure 1: LT 481A demo board schematics
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2.2 Selecting the Injection Point时代在召唤
In order to measure the loop gain of a voltage feedback loop we need to break the loop at a suitable point and inject a disturbance signal at this point. The disturbance signal will be distributed around the loop and depending on the loop gain the signal will be amplified or attenuated and shifted in pha. The Bode 100 output will provide the disturbance signal whereas the inputs will measure the transfer function of the loop.
To ensure that the measured loop gain equals the real loop gain we need to find a point where the loop is restricted to one single path and where the impedance looking in the direction of the loop is much bigger than the impedance looking backwards.积极向上的
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The following figure shows the feedback loop of the circuit and indicates the suitable injection point. The impedance looking backwards equals the output impedance of the converter which is very low (in the range of veral ). The impedance looking in direction of the loop is formed by the compensator and the voltage divider and is in the range of veral .
Figure 2: Feedback loop and injection point
