IR3086AMPBF 查看數據表（PDF） - International Rectifier
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IR3086AMPBF Datasheet PDF : 33 Pages
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IR3086APbF
VOLTAGE LOOP COMPENSATION
The adaptive voltage positioning (AVP) is usually adopted in the computer applications to improve the transient
response and reduce the power loss at heavy load. Like current mode control, the adaptive voltage positioning loop
introduces extra zero to the voltage loop and splits the double poles of the power stage, which make the voltage
loop compensation much easier.
Resistors RFB and RDRP are chosen according to Equations (13) and (14), and the selection of compensation types
depends on the output capacitors used in the converter. For the applications using Electrolytic, Polymer or AL-
Polymer capacitors and running at lower frequency, type II compensation shown in Figure 8(a) is usually enough.
While for the applications using only ceramic capacitors and running at higher frequency, type III compensation
shown in Figure 8(b) is preferred.
For applications where AVP is not required, the compensation is the same as for the regular voltage mode control.
For converter using Polymer, AL-Polymer, and ceramic capacitors, which have much higher ESR zero frequency,
type III compensation is required as shown in Figure 8(b) with RDRP and CDRP removed.
CCP1
VO+
RFB
VDRP
RDRP
CCP1
RCP
CCP
FB -
EAOUT
VDAC +
EAOUT
RFB
VO+
RFB1 CFB
VDRP
RDRP
CDRP
RCP
CCP
FB
VDAC
-
EAOUT
+
EAOUT
(a) Type II compensation
(b) Type III compensation
Figure 8. Voltage loop compensation network
Type II Compensation for AVP Applications
Determine the compensation at no load, the worst case condition. Choose the crossover frequency fc between 1/10
and 1/5 of the switching frequency per phase. Assume the time constant of the resistor and capacitor across the
output inductors matches that of the inductor, and determine RCP and CCP from Equations (25) and (26), where LE
and CE are the equivalent inductance of output inductors and the equivalent capacitance of output capacitors
respectively.
RCP
=
(2π
∗ fC )2 ∗ LE ∗ CE ∗ RFB ∗VPWMRMP
VO * 1 + (2π * fC * C * RC )2
(25)
CCP
10 ∗
=
LE ∗ CE
RCP
(26)
CCP1 is optional and may be needed in some applications to reduce the jitter caused by the high frequency noise. A
ceramic capacitor between 10pF and 220pF is usually enough.
Type III Compensation for AVP Applications
Determine the compensation at no load, the worst case condition. Assume the time constant of the resistor and
capacitor across the output inductors matches that of the inductor, the crossover frequency and phase margin of the
voltage loop can be estimated by Equations (27) and (28), where RLE is the equivalent resistance of inductor DCR.
fC1
=
2π
* CE
RDRP
∗ GCS * RFB
∗ RLE
Page 18 of 33
(27)
9/30/04
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