SSL152x
SMPS ICs for mains LED drivers
Rev. 3 — 17 September 2010
Product data sheet
1. General description
The SSL152x family is a Switched Mode Power Supply (SMPS) controller IC that operate
directly from the rectified universal AC mains. It is implemented in the high-voltage Easy
High Voltage Silicon-On-Insulator (EZ-HV SOI) process, combined with a low-voltage
Bipolar Complementary Metal Oxide Semiconductor (BiCMOS) process. The device
includes a high-voltage power switch and a start-up circuit that operates directly from the
rectified mains voltage.
A dedicated circuit for valley switching is built in, which makes a very efficient slim-line
electronic concept for solid state lighting applications possible.
The SSL152x family can operate in applications with a power range of up to 15 W.
Applications in the range between 15 W and 25 W are more suited to the SSL1623PH.
LED powers above 25 W are more suited to the SSL1750.
In the most basic applications, the SSL152x family act as a voltage source. Here, no
additional secondary electronics are required. A combined voltage and current source can
be realized with minimum costs for external components. Implementation of the SSL152x
family renders an efficient and low cost power supply system for mains LED drivers.
2. Features and benefits
Designed for mains LED drivers up to 15 W
Integrated power switch:
SSL1522T: 12
Ω;
650 V
SSL1523P: 6.5
Ω;
650 V
Operates from universal AC mains supplies (80 V to 276 V)
Adjustable frequency for flexible design
RC oscillator for load insensitive regulation loop constant
Valley switching for minimum switch-on loss
Low standby power (< 100 mW) with frequency reduction at low power outputs
Adjustable overcurrent protection
Undervoltage protection
Temperature protection
Short-circuit winding protection
Simple application with both primary and secondary (opto) feedback
Available in DIP8 and SO14 packages
NXP Semiconductors
SSL152x
SMPS ICs for mains LED drivers
8. Functional description
The SSL152x family is the heart of a compact flyback converter, with the IC placed at the
primary side. The auxiliary winding of the transformer can be used for indirect feedback to
control the isolated output. This additional winding also powers the IC. A more accurate
control of the output voltage and/or current can be implemented with an additional
secondary sensing circuit and optocoupler feedback.
The SSL152x family uses voltage mode control. The switching frequency is determined by
the maximum transformer demagnetizing time and the frequency of the oscillator. In the
first case, the converter operates in the Self Oscillating Power Supply (SOPS) mode. In
the latter case, it operates at a constant frequency, which can be adjusted with external
components R
RC
and C
RC
. Furthermore, a primary stroke is started only in a valley of the
secondary ringing. This can use constant power or constant current mode to drive LEDs.
The valley switching principle minimizes capacitive switch-on losses.
8.1 Start-up and undervoltage lockout
Initially, the IC is self-supplying from the rectified mains voltage. The IC starts switching as
soon as the voltage on pin V
CC
passes the V
CC(startup)
level. The supply is taken over by
the auxiliary winding of the transformer as soon as V
CC
is high enough and the supply
from the line is stopped for high efficiency operation.
If the auxiliary supply is not sufficient, the high-voltage supply also supplies the IC. As
soon as the voltage on pin V
CC
drops below the V
CC(stop)
level, the IC stops switching and
restarts from the rectified mains voltage.
8.2 Oscillator
The frequency of the oscillator is set by the external resistor and capacitor on pin RC. The
external capacitor is charged rapidly to the V
RC(max)
level and, starting from a new primary
stroke, it discharges to the V
RC(min)
level. Because the discharge is exponential, the
relative sensitivity of the duty factor to the regulation voltage at low duty factor is almost
equal to the sensitivity at high duty factors. This results in a more constant gain over the
duty factor range compared to systems with a linear sawtooth oscillator. Stable operation
at low duty factors is easily realized. For high efficiency, the frequency is reduced as soon
as the duty factor drops below its low power threshold. This is accomplished by increasing
the oscillator charge time.
To ensure that the capacitor can be charged within the charge time, the value of the
oscillator capacitor should be limited to approximately 1 nF.
8.3 Duty factor control
The duty factor is controlled by the internal regulation voltage and the oscillator signal on
pin RC. The internal regulation voltage is equal to the external regulation voltage (minus
2.5 V) multiplied by the gain of the error amplifier (typically 20 dB).
SSL152X
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Product data sheet
Rev. 3 — 17 September 2010
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