CS1630-FSZ datasheet(12/56 Pages) APEX

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CS1630/31

DS954F2

5. GENERAL DESCRIPTION

5.1 Overview

The CS1630 and CS1631 are high-performance offline AC/DC

LED drivers for dimmable and high color rendering index (CRI)

LED replacement lamps and luminaires. They feature Cirrus

Logic’s

proprietary

digital

dimmer

compatibility

control

technology and digital correlated color temperature (CCT) control

system that enables two-channel LED color mixing. The CS1630

is designed for 120VAC line voltage applications, and the

CS1631 is optimized for 230VAC line voltage applications.

The CS1630/31 integrates a critical conduction mode (CRM)

boost converter, providing power factor correction and superior

dimmer compatibility with a primary-side regulated quasi-

resonant second stage, which is configurable for isolated and

non-isolated topologies. The digital CCT control system provides

the ability to program dimming profiles, such as constant CCT

dimming and black body line dimming. The CS1630/31

optimizes LED color mixing by temperature compensating LED

current with an external negative temperature coefficient

(NTC) thermistor. The IC controller is also equipped with power

line calibration for remote system calibration and end-of-line

programming. The CS1630/31 provides a register lockout

feature for security against potential access to proprietary

registers.

5.2 Startup Circuit

An external, high-voltage source-follower circuit is used to

deliver startup current to the IC. During steady-state operation,

an auxiliary winding on the boost inductor biases this circuit to

an off state to improve system efficiency, and all IC supply

current is generated from the auxiliary winding. The patent

pending technology of the external, high-voltage source-

follower circuit enables system compatibility with digital

dimmers (dimmers containing an internal power supply) by

providing a continuous path for a dimmer’s power supply to

recharge during its off state. During steady-state operation,

high-voltage FET Q1 is source-switched by a variable internal

current source on the SOURCE pin to create the boost circuit.

A Schottky diode with a forward voltage less than 0.6V is

recommended for D5. Schottky diode D5 will limit inrush current

through the internal diode, preventing damage to the IC.

5.3 Dimmer Switch Detection

The CS1630/31 dimmer switch detection algorithm determines

if the solid-state lighting system is controlled by a regular switch,

a leading-edge dimmer, or a trailing-edge dimmer. Dimmer

switch detection is implemented using two modes: Dimmer

Learn Mode and Dimmer Validate Mode. These assist in

limiting the system power losses. Once the IC reaches UVLO

start threshold VST(th) and begins operating, the CS1630/31 is

in Dimmer Learn Mode, allowing the dimmer switch detection

circuit to set the operating state of the IC to one of three modes:

No-dimmer Mode, Leading-edge Mode, or Trailing-edge Mode.

5.3.1 Dimmer Learn Mode

In Dimmer Learn Mode, the dimmer detection circuit spends

approximately two line-cycles learning whether there is a

dimmer switch and, if present, whether it is a trailing-edge or

leading-edge dimmer. A modified version of the leading-edge

algorithm is used. The trailing-side slope of the input line

voltage is sensed to decide whether the dimmer switch is a

trailing-edge dimmer. The dimmer detection circuit transitions to

Dimmer Validate Mode once the circuit detects that a dimmer is

present.

5.3.2 Dimmer Validate Mode

During normal operation, CS1630/31 is in Dimmer Validate

Mode. This instructs the dimmer detection circuit to periodically

validate that the IC is executing the correct algorithm for the

attached dimmer. The dimmer detection algorithm periodically

verifies the IC operating state as a protection against incorrect

detection. As additional protection, the output of the dimmer

detection algorithm is low-pass filtered to prevent noise or

transient events from changing the IC’s operating mode. The IC

will return to Dimmer Learn Mode when it has determined that

the wrong algorithm is being executed.

5.3.3 No-dimmer Mode

Upon detection that the line is not phase cut with a dimmer, the

CS1630/31 operates in No-dimmer Mode, where it provides a

power factor that is in excess of 0.9. The CS1630/31

accomplishes this by boosting in CRM and DCM mode. The

peak current is modulated to provide link regulation. The

CS1630/31 alternates between two settings of peak current. To

regulate the boost output voltage, the CS1630/31 uses a peak

current set by register PEAK_CUR (see "Peak Current

(PEAK_CUR) – Address 51" on page 39). The time that this

current is used is determined by an internal compensation loop

to regulate the boost output voltage. The internal algorithm will

reduce the peak current of the boost stage to maintain output

voltage regulation and obtain the desired power factor.

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