CS1631 datasheet(14/56 Pages) APEX

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CS1630/31

DS954F2

Figure 11. Block Diagram of Color Control System

The reference currents are the required values at TA =25ºC

and dim = 100%. They are multiplied by the appropriate gains,

and these values are passed to the final power stage. The

CS1630/31 uses polynomial approximations in one and two

dimensions to generate the color gains. These polynomials

can be up to third-order.

GAINDTR approximations create a custom temperature

compensation profile and dimming profile of the temperature-

sensitive LEDs (see Equation 1). Profiles are programmed

through the Color Polynomial Coefficient registers (see "Color

Polynomial Coefficient (P30, P20, P10, P03, P02, P01, P21,

P12, P11, P00) – Address 5 - 24" on page 29).

GAINDR approximation allows custom dimming profile of the

white LEDs (see Equation 2). The profile is programmed

through the Color Polynomial Coefficient registers (see "Color

Polynomial Coefficient (Q3, Q2, Q1, Q0) – Address 25 - 32" on

page 30).

Cirrus Logic, Inc. and its affiliates and subsidiaries generally

make no representations or warranties that the combination of

Cirrus Logic’s products with light-emitting diodes (“LEDs”),

converter materials, and/or other components will not infringe

any third-party patents, including any patents related to color

mixing in LED lighting applications, such as, for example, U.S.

Patent No. 7,213,940 and related patents of Cree, Inc. For

more information, please see Cirrus Logic’s Terms and

Conditions of Sale, or contact a Cirrus Logic sales

representative.

5.5 Dimming Signal Extraction and the

Dim Mapping Algorithm

When operating with a dimmer, the dimming signal is

extracted in the time domain and is proportional to the

conduction angle of the dimmer. A control variable is passed

to the quasi-resonant second stage to achieve 0% to 100%

output currents.

5.6 Boost Stage

The high-voltage FET in the source-follower startup circuit is

source-switched by a variable current source on the SOURCE

pin to operate a boost circuit. Peak FET switching current is

set by the PEAK_CUR register (see "Peak Current

(PEAK_CUR) – Address 51" on page 39).

In No-dimmer Mode, the boost stage begins operating when

the start threshold is reached during each rectified half line-cy-

cle and is disabled at the nominal boost output voltage. The

peak FET switching current determines the percentage of the

rectified input voltage conduction angle over which the boost

stage will operate. The control algorithm adjusts the peak FET

switching current to maximize the operating time of the boost

stage, thus improving the input power factor.

When operating in Leading-edge Mode, the boost stage

ensures the hold current requirement of the dimmer is met

from the initiation of each half-line dimmer conduction cycle

until the peak of the rectified input voltage. Trailing-edge Mode

boost stage ensures that the trailing-edge is exposed at the

correct time with the correct current.

Gain

White

dim

IWhite

Iref

White

Iref

Color

ADC

NTC

IColor

Gain

Color

where,

T = the measured normalized temperature and is 0

T1.0

D = the normalized dim value and is 0

D1.0

GAINDTR = gain of the channel based on the temperature measurement and the dim value:

where,

D = the normalized dim value and is 0

D1.0

GAINDR = gain of the channel based on the dim value

GAINDTR P30 T



P20 T



P10



P03 D



P02



P01 D



P21 T



P12 T D



P11 T D



P00

[Eq.1]

GAINDR Q3



Q2 D



Q1 D



[Eq.2]

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