ISL6269_06 Datasheet, PDF (16/17 Pages) Intersil Corporation – High-Performance Notebook PWM Controller with Bias Regulator and Audio-Frequency Clamp

ISL6269
T(s)=G_COMP(s) + G_VOVC(s)
V_REF
+
−
G_COMP(s)
V_COMP
V_o
G_VOVC(s)
FIGURE 6. SYSTEM CONTROL BLOCK DIAGRAM
Vcomp to Vo Transfer Function Gvovc(s)
120
90
100
60
80
30
60
0
40
30
20
60
0
90
20
120
40
10
150
100
1 ^.10³
1 ^.10⁴
1 ^.10⁵
1 ^.10⁶
Frequency (Hz)
Gain (Gvovc)
Phase (Gvovc)
FIGURE 7. OPEN LOOP TRANSFER FUNCTION
The compensator zero fz1 is written as:
ω_z1
=
---------------------¹----------------------
R_comp • C_comp2
(EQ. 19)
f_z1
=
ω_-----z---1-
2•π
The compensator pole fp1 is written as:
ω_p1 =
----------¹----------- + ----------¹----------- • --------¹---------
C_comp1 C_comp2 R_comp
(EQ. 20)
(EQ. 21)
f_p1
=
ω_-----p---1-
2•π
The compensator gain is written as:
ω_i
=
--------------------------------------¹--------------------------------------
R_comp • [C_comp1 + C_comp2]
The compensator transfer function is written as:
G_comp(s)
=
-^ω----ⁱ--^•-----¹-----+------^ω-------^{s--z------1-----}
s•
1 + ----^s-----
ω_p1
(EQ. 22)
(EQ. 23)
(EQ. 24)
C_COMP1
120
100
80
60
40
20
0
20
40
10
Voltage Loop Gain T(s)
100
1 ^.10³
1 ^.10⁴
1 ^.10⁵
90
75
60
45
30
15
0
15
30
1 ^.10⁶
Gain (Tv)
Phase (Tv)
Frequency (Hz)
FIGURE 8. CLOSED LOOP TRANSFER FUNCTION
C_COMP2
R_COMP
R_BOTTOM
FB
−
V_REF
ERROR
AMPLIFIER
COMP
FIGURE 9. SYSTEM CONTROL BLOCK DIAGRAM
16
FN9177.1
August 7, 2006