CS1630/31
The buck stage is controlled by measuring current in the buck
inductor and voltage on the auxiliary winding. Quasi-resonant
operation is achieved by detecting buck inductor
demagnetization using an auxiliary winding. The digital control
algorithm rejects line-frequency ripple created on the second
stage input by the front-end boost stage, resulting in the
highest possible LED efficiency and long LED life.
configuration, and a PMOS switch is used in buck/tapped
buck configuration (see Figures 15, 16, and 17).
LED 1+
T1
VBST
C12
R15 D10
Z2
LED 1-
C9
Z3
D7
D9
VCC
_
Q
The tapped buck stage operates similar to a buck stage. The
tapped buck topology provides minimum turn-on time and
improves conversion efficiency when large input-to-output
voltage ratio is present. The tapped buck inductor behaves as
a transformer for voltage conversion and is controlled by
measuring current in the tapped inductor and voltage on the
auxiliary winding. Quasi-resonant operation is achieved by
detecting tapped inductor demagnetization using an auxiliary
winding.
D11
Q5
D
GND
LED 2+
R12
D8
R16
C10
CS1630/31
C11
Q4
13
15
GD
LED2-
IGND
FBAUX
11
FBSENSE
R13
R11
GND
12
R14
VBST
LED2+
R15 D10
C11
Z3
C9
LED 2-
D9
D8
Figure 18. Flyback Series Output Model
D11
VCC
_
Q
Q5
Similarly, a series connection in a flyback stage and buck
stage use an NMOS switch and a PMOS switch, respectively,
as shown in Figures 18 and 19.
D
GND
R12
R16
C10
LED1+
C12
LED1-
L3
LED1+
CS1630/31
VBST
IGND
Q4
13
15
C12
GD
R15
D10
LED1-
FBAUX
R13
Z3
C9
11
FBSENSE
D8
D9
VCC
GND
_
Q
D11
LED2+
Q5
D
R11
R14
GND
R12
R16
C10
12
C11
LED 2-
L3
CS1630/31
IGND
Q4
13
15
GD
Figure 17. Tapped Buck Parallel Output Model
FBAUX
R13
R14
11
FBSENSE
5.8.1 Series & Parallel Two-Channel Output
The CS1630/31 is designed to be programmed to support
series or parallel two-channel output configurations using one
set of power magnetics. Series or parallel configuration is set
by bit STRING and bit LED_ARG in the Config3 register (see
"Configuration 3 (Config3) – Address 35" on page 32). A
parallel connection for a flyback stage and buck stage are
connected differently: an NMOS switch is used in flyback
R11
GND
12
Figure 19. Buck Series Output Model
DS954F2
17
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