NF FRA51602, Инструкция по эксплуатации

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4.2 Simple operation for the first use
4
-
6
FRA 51602
4.2.2 Measuring loop gain
The results of measuring the loop characteristics (loop gain characteristic) of a negative feedback loop are
phase margin and gain margin, which are indicators of negative feedback loop stability. The basic
connections for measuring the loop gain are illustrated below.
Figure 4-1 Connections for loop gain measurement
The set up and measurement method for a typical DC-DC converter are explained below.
Figure 4-2 Example of connections for measuring the loop gain of a DC-DC converter
The injection resistance in the above diagram is inserted to prevent an open loop if the measurement probe
is removed from the circuit being measured. The resistance value is several tens of ohms or less and
sufficiently smaller than R1.
y
β
Ａ
u
+
-
～ 1 2
PWM
SW RECT
～
1
2
ERROR
AMP
VREF
R1
OUTPUT
FRA51602
Injection resistance
Several
10Ω (<<R1)