Preliminary

TS19453

AC/DC Programmable Current WLED Driver

w/PWM Dimming Control

3/7

Version: Preliminary

Function Description

The TS19453 is a PWM peak current controller for controlling a buck converter topology in continuous conduction

mode (CCM). The output current is of converter that can be programmed by a single external resistor (Rsense), for

the purpose of driving a string of LED, an external enable input (PWMD) is provided that can be utilized for PWM

dimming of an LED string.

When the input voltage of 20~400V appears at the Drain pin, the internal high-voltage linear regulator seeks to

maintain a voltage of 7.5VDC at the VDD pin. Until this voltage exceeds the internally programmed under-voltage

threshold, the output switching MOSFET is non-conductive. When the threshold is exceeded, the integrated high-

voltage switch turns on, pulling the Drain low, A 200mV hysteresis is incorporated with the undervoltage

comparator to prevent oscillation.

When the voltage at Rsense exceeds 0.47V(typ), the switch turns off and the Drain output becomes high

impedance, at the same time, a one shot circuit is activated that determines the off-time of the switch.

A “blanking” delay of 300nS is provided that presents false triggering of the current sense comparator due to the

leading edge spike caused by circuit parasitic.

Application Information

The TS19453 is specifically designed for driving multi LED strings. It can be operated from either universal AC line

range of 85~264VAC or 20~400VDC, and drives up to tens of high brightness LEDs. All LEDs can be run in series

and this device regulates at constant current, yielding uniform illumination.

Selecting L1 and D1

There is a certain trade-off to be considered between optimal sizing of the output inductor L1 and the tolerated

introduces a peak-to-average error in the output current setting that needs to be accounted for. Due to constant off-

time control technique used in the TS19453, the ripple current is independent of the input AC or DC line voltage

variation. Therefore, the output current will remain unaffected by the varying input voltage.

Adding a filter capacitor across the LED string can reduce the output current ripple even further, thus permitting a

reduced value of L1. However, one must keep in mind that the peak-to-average current error is affected by the

Another important aspect of designing an LED driver with TS19453 is related to certain parasitic elements of the

circuit, including distributed coil capacitance of L1, junction capacitance and reverse recover of the rectifier diode

elements affect the efficiency of the switching converter and could potentially cause false triggering of the current

sense comparator if not properly managed. Minimizing these parasitic is essential for efficient and reliable

operation.

Coil capacitance of inductors is typically provided in the manufacturer’s data books either directly or in terms of the

self-resonant frequency (SRF).