CS1610/11/12/13

2

DS929F3

1. INTRODUCTION

Figure 1. CS1610/11/12/13 Block Diagram

A typical schematic using the CS1610/11 for flyback

applications is shown on the previous page.

Startup current is provided from a patent-pending, external

high-voltage source-follower network. In addition to providing

startup current, this unique topology is integral in providing

compatibility with digital dimmers by ensuring VDD power is

always available to the IC. During steady-state operation, an

auxiliary winding on the boost inductor back-biases the

source-follower circuit and provides steady-state operating

current to the IC to improve system efficiency.

The rectified input voltage is sensed as a current into pin IAC

and is used to control the adaptive dimmer compatibility

algorithm and extract the phase of the input voltage for output

dimming control. During steady-state operation, the external

high-voltage, source-follower circuit is source-switched in

critical conduction mode (CRM) to boost the input voltage.

This allows the boost stage to maintain good power factor,

provides dimmer compatibility, reduces bulk capacitor ripple

current, and provides a regulated input voltage to the second

stage.

The output voltage of the CRM boost is sensed by the current

into the boost output voltage sense pin (BSTOUT). The quasi-

resonant second stage is implemented with peak-current

mode primary-side control, which eliminates the need for

additional components to provide feedback from the

secondary and reduces system cost and complexity.

Voltage across an external user-selected resistor is sensed

through pin FBSENSE to control the peak current through the

second stage inductor. Leading-edge and trailing-edge

blanking on pin FBSENSE prevents false triggering.

Pin FBAUX is used to sense the second stage inductor

demagnetization to ensure quasi-resonant switching of the

output stage.

When an external negative temperature coefficient (NTC)

thermistor

is

connected

to

the

eOTP

pin,

the

CS1610/11/12/13 monitors the system temperature, allowing

the controller to reduce the output current of the system. If the

temperature reaches a designated high set point, the IC is

shutdown and stops switching.

POR

+

-

Voltage

Regulator

14

VDD

11

FBSENSE

+

-

15

FBAUX

+

-

13

GD

2

IAC

DAC

+

-

Peak

Control

Second Stage ZCD

+

-

Output Open

12

GND

OLP

+

-

16

BSTOUT

MUX

OCP

+

-

1

BSTAUX

Boost ZCD

3

CLAMP

V

FB ZCD(th)

9

4

SGND

5

SOURCE

+

-

+

-

VDD

V

CONNE CT(th )

10

FBGAIN

8

IPK

eOTP

15k

ADC

MUX

15k

VDD

I

CLA MP