HA17431 Series
AC characteristic determination: This refers to the determination of the gain frequency characteristic of
the shunt regulator as an error amplifier. Taking the configuration in figure 2, the error amplifier
characteristic is as shown in figure 3.
G1
f1 fAC
G2 When R5 ≠ 0
When R5 = 0
f2
fOSC Frequency f (Hz)
* fOSC : PWM switching frequency
Figure 3 HA17431 Error Amplification Characteristic
In Figure 3, the following formulas are obtained:
Gain
G1 = G0 ≈ 50 dB to 60 dB (determined by shunt regulator)
G2
=
R5
R3
Corner frequencies
f1 = 1/(2π C1 G0 R3)
f2 = 1/(2π C1 R5)
G0 is the shunt regulator open-loop gain; this is given by the reciprocal of the reference voltage fluctuation
∆Vref/∆VKA, and is approximately 50 dB.
Rev.1, Sep. 2002, page 18 of 24