UCC28180
SLUSBQ5A –NOVEMBER 2013–REVISED NOVEMBER 2013
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The voltage transfer function, GVL(f) contains the product of the voltage feedback gain, GFB, and the gain from the
pulse width modulator to the power stage, GPWM_PS, which includes the pulse width modulator to power stage
pole, fPWM_PS. The plotted result is shown in Figure 33.
RFB2
GFB
=
R
FB1 + RFB2
13kW
GFB
=
= 0.013
1MW +13kW
(105)
1
fPWM _ PS
=
=
K12.5RSENSEVO3UTCOUT
2p
KFQM1M2V2
IN(nom)
1
fPWM _ PS
= 1.479Hz
7 ´ 2.5 ´0.032W ´390V3 ´ 270mF
2p
V
8.475ms ´0.539´1.392 ´115 V2
ms
(106)
M3VOUT
M1M2 ´1V
GPWM _ PS(f) =
s(f)
1+
2pfPWM_ PS
(107)
(108)
GVL(f) = GFBGPWM _ PS(f)
GVLdB(f) = 20log G (f)
(
VL
)
100
80
0
PWM to Power Stage Gain
Total Open Loop Gain
Total Open Loop Phase
±10
±20
±30
±40
±50
±60
±70
±80
±90
±100
60
40
20
0
±20
±40
±60
±80
±100
0.01
0.1
1
10
100
1000
Frequency (Hz)
C008
Figure 34. Bode Plot of the Open Voltage Loop without Error Amplifier
36
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