SSL1523A
SMPS ICs for mains LED drivers
Rev. 1 — 25 April 2012
Product data sheet
1. General description
The SSL1523A 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 SSL1523A can operate in applications with a power range of up to 15 W.
In the most basic applications, the SSL1523A 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 SSL1523A
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: 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
Simple application with both primary and secondary (opto) feedback
Available in a DIP8 package
NXP Semiconductors
SSL1523A
SMPS ICs for mains LED drivers
3. Applications
Retro-fit LED lamps
LED ballasts
Contour lighting
Channel letter lighting
Commercial lighting, such as cabinet or freezer lights
Other lighting applications
4. Quick reference data
Table 1.
Symbol
V
DRAIN
R
DSon
Quick reference data
Parameter
voltage on pin DRAIN
drain-source on-state
resistance
Conditions
DMOS power transistor; T
j
> 0
°C
I
source
=
−0.50
A
T
j
= 25
°C
T
j
= 100
°C
V
CC
f
osc
I
DRAIN
supply voltage
oscillator frequency
current on pin DRAIN
V
DRAIN
> 60 V
no auxiliary supply
with auxiliary supply
-
-
1.5
30
2
125
mA
μA
continuous
-
-
−0.4
10
6.5
9.0
-
100
7.5
10.0
+40
200
Ω
Ω
V
kHz
Min
−0.4
Typ
-
Max
+650
Unit
V
5. Ordering information
Table 2.
Ordering information
Package
Name
SSL1523AP
DIP8
Description
plastic dual in-line package; 8 leads (300 mil)
Version
SOT97-1
Type number
SSL1523A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Product data sheet
Rev. 1 — 25 April 2012
2 of 17
NXP Semiconductors
SSL1523A
SMPS ICs for mains LED drivers
6. Block diagram
V
CC
1
SUPPLY
8
DRAIN
VALLEY
SSL1523AP
7
n.c.
GND
2
LOGIC
100 mV
stop
3
RC
OSCILLATOR
THERMAL
SHUTDOWN
PROTECTION
LOGIC
POWER - UP
RESET
blank
6
SOURCE
low freq
F
1.8
U
10
x
4
REG
2.5 V
overcurrent
0.5 V
5
AUX
aaa-002488
Fig 1.
Block diagram
7. Pinning information
7.1 Pinning
V
CC
GND
RC
REG
1
2
8
7
DRAIN
n.c.
SOURCE
AUX
SSL1523AP
3
4
aaa-002489
6
5
Fig 2.
Pinning diagram (DIP8)
SSL1523A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Product data sheet
Rev. 1 — 25 April 2012
3 of 17
NXP Semiconductors
SSL1523A
SMPS ICs for mains LED drivers
7.2 Pin description
Table 3.
Symbol
V
CC
GND
RC
REG
AUX
SOURCE
n.c.
DRAIN
Pin description
Pin (DIP8)
1
2
3
4
5
6
7
8
Description
supply voltage
ground
frequency setting
regulation input
input for voltage from auxiliary winding for timing (demagnetization)
source of internal MOS switch
not connected
drain of internal MOS switch; input for start-up current and valley
sensing
8. Functional description
The SSL1523A 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 SSL1523A 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
SSL1523A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Product data sheet
Rev. 1 — 25 April 2012
4 of 17
NXP Semiconductors
SSL1523A
SMPS ICs for mains LED drivers
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).
8.4 Valley switching
A new cycle is started when the primary switch is switched on (see
Figure 3).
After a
certain time (determined by the oscillator voltage RC and the internal regulation level), the
switch is turned off and the secondary stroke starts. The internal regulation level is
determined by the voltage on pin REG.
After the secondary stroke, the drain voltage shows an oscillation with a frequency
approximately equal to the value given by
Equation 1:
1
---------------------------------------------
-
2
× π × (
L
p
×
C
p
)
where:
L
p
= primary self-inductance
C
p
= parasitic capacitance on drain node
As soon as the oscillator voltage becomes high again and after the secondary stroke has
ended, the circuit waits for a low drain voltage before starting a new primary stroke.
Figure 3
shows the drain voltage together with the valley signal, the signal indicating the
secondary stroke and the RC voltage.
The primary stroke starts some time before the actual valley at low ringing frequencies,
and some time after the actual valley at high ringing frequencies.
(1)
SSL1523A
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Product data sheet
Rev. 1 — 25 April 2012
5 of 17
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