LNK584-586
LinkZero-AX
Zero Standby Consumption Integrated Off-Line Switcher
Product Highlights
Lowest System Cost with Zero Standby Consumption
•
•
•
•
•
Simple system configuration provides zero consumption standby/
+
power-down with user controlled wake up
Very tight IC parameter tolerances improves system manufacturing
yield
Suitable for low-cost clampless designs
Frequency jittering greatly reduces EMI filter cost
Extended package creepage improves system field reliability
P
IN
<0.00 W at
325 VDC in
Power Down Mode
+
DC
Output
Wide Range
High-Voltage
DC Input
LinkZero-AX
D
FB
BP/M
Advanced Protection/Safety Features
•
•
•
•
S
•
Hysteretic thermal shutdown protection – automatic recovery
Power
Down
Pulse
≥2.5 ms
Reset/Wake
Up Pulse
PI-5909-120710
reduces field returns
Universal input range allows worldwide operation
Auto-restart reduces delivered power by >85% during short-circuit
and open-loop fault conditions
Simple ON/OFF control, no loop compensation needed
High bandwidth provides fast turn on with no overshoot
C
BP
Figure 1.
Typical Application Schematic.
EcoSmart™–
Energy Efficient
•
Standby/power-down consumption less than 3 mW at
325 VDC input (Note 1)
•
Easily meets all global energy efficiency regulations with no added
components
•
ON/OFF control provides constant efficiency to very light loads
Output Power Table
230 VAC ±15%
Product
3
85-265 VAC
Open Frame
2
3W
3W
4W
4.5 W
5W
5.5 W
Open Frame
2
3W
3W
4.5 W
5W
6W
6.5 W
Applications
supplies
•
Ultra low consumption isolated or non-isolated standby and auxiliary
LNK584DG
LNK584GG
LNK585DG
LNK585GG
LNK586DG
LNK586GG
Description
LinkZero™-AX combines extremely low standby/power-down energy
use with the industry’s lowest component count standby supply
solution. Below 3 mW at 230 VAC in power-down (PD) mode meets IEC
62301 definition of zero power consumption and is immeasurable on
most power meters. LinkZero-AX is set into power-down mode using
an external signal to pull the FEEDBACK pin high for 2.5 ms. Such an
external signal can be generated by a system micro controller or
infrared controller. In power-down mode the BYPASS pin remains
regulated allowing the LinkZero-AX to be woken up with a reset pulse
to pull the BYPASS pin below a reset threshold (1.5 V). Ultra low
system consumption is therefore achieved without needing to
disconnect the input voltage with a relay.
LinkZero-AX is designed to be used in isolated or non-isolated
converters. In either, the tightly specified FEEDBACK (FB) pin voltage
reference enables universal input primary side regulated power
supplies that cost effectively replace unregulated linear transformer
and other switched mode supplies. The start-up and operating power
are derived directly from the DRAIN pin. The internal oscillator
frequency is jittered to significantly reduce both quasi-peak and
average EMI, minimizing filter cost.
Table 1. Output Power Table.
Notes:
1. IEC 62301 Clause 4.5 rounds standby power use below 5 mW to zero.
2. Maximum practical continuous power in an open frame design with adequate
heat sinking, measured at 50 °C ambient.
3. Packages: D: SO-8C, G: SMD-8C.
www.power.com
November 2015
This Product is Covered by Patents and/or Pending Patent Applications.
LNK584-586
BYPASS/
MULTI FUNCTION
(BP/M)
PU
GENERATOR
FEEDBACK REF
1.70 V
3V
+
+
+
OVERVOLTAGE
PROTECTION
5.85 V
4.85 V
REGULATOR
5.85 V
+
-
DRAIN
(D)
6.5 V
BYPASS PIN
UNDERVOLTAGE
OPEN LOOP
PULL UP
FEEDBACK
(FB)
0.9 V
+
AUTO-RESTART
COUNTER
RESET
JITTER
FAULT
CURRENT LIMIT
+
-
VI
LIMIT
CLOCK
CC CUT BACK
1.70 V - 0.9 V
ADJ
DC
MAX
S
R
Q
Q
OSCILLATOR
SYSTEM
POWER
DOWN
LEADING
EDGE
BLANKING
POWER
DOWN
COUNTER
160 f
OSC
CYCLES
RESET
PU
PI-5912-111412
SOURCE
(S)
Figure 2.
Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
The power MOSFET drain connection provides internal operating
current for both start-up, steady-state and power-down mode
operation.
BYPASS/MULTI-FUNCTIONAL (BP/M) Pin:
An external bypass capacitor, 0.1
mF
or greater for the internally
generated 5.85 V supply is connected to this pin. The minimum value
of capacitor is 0.1
mF
for internal circuit operation. Higher values may
be required to enter power-down mode (see LinkZero-AX Power-
Down (PD) Mode Design Considerations). An overvoltage protection
disables MOSFET switching if the current into the pin exceeds 6.5 mA
(I
SD
).
FEEDBACK (FB) Pin:
During normal operation, switching of the power MOSFET is
controlled by this pin. MOSFET switching is disabled when a voltage
greater than an internal V
FB
reference voltage is applied to this pin.
The V
FB
reference voltage is internally set to 1.70 V. LinkZero-AX
goes into auto-restart mode when the FEEDBACK pin voltage has
come down to 0.9 V.
SOURCE (S) Pin:
This pin is the power MOSFET source connection. It is also the
ground reference for the BYPASS and FEEDBACK pins.
G Package (SMD-8C)
BP/M
FB
1
2
8
7
6
D
4
3a
D Package (SO-8C)
1
2
8
7
6
D
4
5
S
S
S
S
BP/M
FB
S
S
S
S
5
3b
PI-5910-090810
Figure 3.
Pin Configuration.
2
Rev. C 11/15
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LNK584-586
LinkZero-AX Functional Description
LinkZero-AX comprises a 700 V power MOSFET switch with a power
supply controller on the same die. Unlike conventional PWM (pulse
width modulation) controllers, it uses a simple ON/OFF control to
regulate the output voltage. The controller consists of an oscillator,
feedback (sense and logic) controller, 5.85 V regulator, BYPASS pin
undervoltage protection, over-temperature protection, frequency
jittering, current limit protection, and leading edge blanking. The
controller includes a proprietary power-down mode that automatically
reduces standby consumption to levels that are immeasurable on
most power meters.
Power-Down Mode
The internal controller will go into power-down mode when 160
switching cycles are skipped. This can occur due to the FEEDBACK
pin being pulled high using an external power-down pulse signal or
due to a light load condition where the total loading on the
transformer (output plus feedback circuit loads) has reduced to
~0.6% of full load. The device then operates in an ultra low
consumption power-down mode where switching is disabled
completely. The controller wakes up (or is reset) when the BYPASS
pin is pulled below 1.5 V and then released to be recharged through
the internal drain connected 5.85 V regulator block (see Figure 2).
When the BYPASS capacitor recharges to the V
BP
BYPASS pin
threshold, the device starts switching and operates normally. If the
FEEDBACK pin is pulled high such that 160 cycles are again skipped,
the device returns to power-down mode operation as described
above. In applications with dynamic loads it may not be desirable to
go into power-down mode under light or no-load conditions.
Techniques to ensure this is avoided are discussed in the LinkZero-AX
power-down Mode Design Considerations section.
Oscillator
The typical oscillator frequency is internally set to an average of
100 kHz. An internal circuit senses the duty cycle of the MOSFET
switch conduction-time and adjusts the oscillator frequency so that
during long conduction intervals (low-line voltage) the frequency is
about 100 kHz and at short conduction intervals (high-line voltage)
the oscillator frequency is about 78 kHz. This internal frequency
adjustment is used to make the peak power point constant over line
voltage. Two signals are generated from the oscillator: the maximum
duty cycle signal (DC
MAX
) and the clock signal that indicates the
beginning of a switching cycle.
The oscillator incorporates circuitry that introduces a small amount of
frequency jitter, typically 6% of the switching frequency, to minimize
EMI. The modulation rate of the frequency jitter is set to 1 kHz to
optimize EMI reduction for both average and quasi-peak
measurements. The frequency jitter, which is proportional to the
oscillator frequency, should be measured with the oscilloscope
triggered at the falling edge of the DRAIN voltage waveform. The
oscillator frequency is gradually reduced when the FEEDBACK pin
voltage is lowered below 1.70 V.
Feedback Input Circuit CV Mode
The feedback input circuit reference is set at 1.70 V. When the
FEEDBACK pin voltage reaches a V
FB
reference voltage (1.70 V), a low
logic level (disable) is generated at the output of the feedback circuit.
This output is sampled at the beginning of each cycle. If high, the
power MOSFET is turned on for that cycle (enabled), otherwise the
power MOSFET remains off (disabled). Since the sampling is done
only at the beginning of each cycle, subsequent changes in the
FEEDBACK pin voltage during the remainder of the cycle are ignored.
Output Power Limiting
When the FEEDBACK pin voltage at full load falls below 1.70 V, the
oscillator frequency linearly reduces to typically 60% at the auto-
restart threshold voltage of 0.9 V. This function limits the power
supply output current and power.
5.85 V Regulator
The BYPASS pin voltage is regulated by drawing a current from the
DRAIN whenever the MOSFET is off if needed to charge up the
BYPASS pin to a typical voltage of 5.85 V. When the MOSFET is on,
LinkZero-AX runs off of the energy stored in the bypass capacitor.
Extremely low power consumption of the internal circuitry allows
LinkZero-AX to operate continuously from the current drawn from the
DRAIN pin. A bypass capacitor value of 0.1
mF
is sufficient for both
high frequency decoupling and energy storage.
6.5 V Shunt Regulator and 8.5 V Clamp
In addition, there is a shunt regulator that helps maintain the BYPASS
pin at 6.5 V when current is provided to the BYPASS pin externally.
This facilitates powering the device externally through a resistor from
the bias winding or power supply output in non-isolated designs, to
decrease device dissipation and increase power supply efficiency.
The 6.5 V shunt regulator is only active in normal operation, and
when in power-down mode a clamp at a higher voltage (typical 8.5 V)
will clamp the BYPASS pin.
BYPASS Pin Undervoltage Protection
The BYPASS pin undervoltage circuitry disables the power MOSFET
when the BYPASS pin voltage drops below 4.85 V. Once the BYPASS
pin voltage drops below 4.85 V, it must rise back to 5.85 V to enable
(turn on) the power MOSFET.
BYPASS Pin Overvoltage Protection
If the BYPASS pin gets pulled above 6.5 V and the current into the
shunt exceeds 6.5 mA a latch will be set and the power MOSFET will
stop switching. To reset the latch the BYPASS pin has to be pulled
down to below 1.5 V.
Over-Temperature Protection
The thermal shutdown circuit senses the die temperature. The
threshold is set at 142
°C
typical with a 70
°C
hysteresis. When the
die temperature rises above this threshold (142
°C)
the power
MOSFET is disabled and remains disabled until the die temperature
falls by 70
°C,
at which point the MOSFET is re-enabled.
Current Limit
The current limit circuit senses the current in the power MOSFET.
When this current exceeds the internal threshold (I
LIMIT
), the power
MOSFET is turned off for the remainder of that cycle. The leading
edge blanking circuit inhibits the current limit comparator for a short
time (t
LEB
) after the power MOSFET is turned on. This leading edge
blanking time has been set so that current spikes caused by
capacitance and rectifier reverse recovery time will not cause
premature termination of the MOSFET conduction.
Auto Restart
In the event of a fault condition such as output short-circuit,
LinkZero-AX enters into auto-restart operation. An internal counter
clocked by the oscillator gets reset every time the FEEDBACK pin
voltage exceeds the FEEDBACK pin auto-restart threshold voltage
(V
FB(AR)
typical 0.9 V). If the FEEDBACK pin voltage drops below V
FB(AR)
for more than 145 ms to 170 ms depending on the line voltage, the
power MOSFET switching is disabled. The auto-restart alternately
enables and disables the switching of the power MOSFET at a duty
cycle of typically 12% until the fault condition is removed.
3
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Rev. C 11/15
LNK584-586
Open-Loop Condition on the FEEDBACK Pin
When an open-loop condition on the FEEDBACK pin is detected, an
internal current source pulls up the FEEDBACK pin to above the V
FB
(1.70 V), the part stops switching and after 160 clock cycles goes into
latched power-down mode.
voltage (1.70 V) is exceeded. When the voltage on the FEEDBACK pin
falls below the disable threshold (1.70 V), switching cycles are
re-enabled. By adjusting the ratio of enabled to disabled switching
cycles the output voltage is regulated. At increased loads, beyond
the output peak power point, where all switching cycles are enabled,
the FEEDBACK pin voltage begins to reduce as the power supply
output voltage falls. Under this condition the switching frequency is
also reduced to limit the maximum output overload power. When the
FEEDBACK pin voltage drops below the auto-restart threshold
(typically 0.9 V on the FEEDBACK pin), the power supply enters the
auto-restart mode. In this mode, the power supply will turn off for
approximately 1.2 s and then turn back on for approximately 145 ms.
The auto-restart function reduces the average output current during
an output short-circuit condition.
The LinkZero-AX device is self biased through the DRAIN pin. An
optional external bias, can be derived either from a third winding or
from an output voltage rail in non-isolated designs. By providing an
external supply current in excess of I
S2
(310
mA
for the LNK584) the
internal 5.85 V regulator circuit is disabled providing a simple way to
reduce device temperature and improve efficiency, especially at
high-line.
A clampless primary circuit is achieved due to the very tight tolerance
current limit device, plus the transformer construction techniques
used. The peak drain voltage is therefore limited to typically less than
550 V at 265 VAC, providing significant margin to the 700 V minimum
drain voltage specification (BV
DSS
).
Output rectification and filtering is achieved with output rectifier D6
and filter capacitor C6. Due to the auto-restart feature, the average
Applications Example
The circuit shown in Figure 4 is a typical non-isolated 5 V, 300 mA
output auxiliary power supply using LinkZero-AX. Isolated
configurations are also fully compatible with the LinkZero-AX where
the FEEDBACK pin receives a signal from a primary feedback/bias
winding or through an optocoupler. The circuit of Figure 4 is typical
of auxiliary supplies in white goods where isolation is often not
required. AC input differential filtering is accomplished by the
π
filter
formed by C1, C2 and L3. The proprietary frequency jitter feature of
the LinkZero-AX eliminates the need for any Y capacitor or common-
mode inductor. Wire-wound resistor RF1 is a fusible, flame proof
resistor which is used as a fuse as well as to limit inrush current.
Wire wound types are recommended for designs that operate
>132 VAC to withstand the instantaneous power dissipated when AC
is first applied.
The output voltage is directly sensed through feedback resistors R3
and R9, and regulated by LinkZero-AX (U1) via the FEEDBACK pin.
Capacitor C7 provides high frequency filtering on the FEEDBACK pin
to filter noise and to avoid switching cycle pulse bunching. The
controller in U1 receives feedback from the output through feedback
resistors R9 and R3. Based on that feedback, it enables or disables
the switching of its integrated MOSFET to maintain output regulation.
Switching cycles are skipped once the FEEDBACK pin threshold
C4
R8 220 pF
5.1
Ω
100 V
L3
1 mH
R2
4.7 kΩ
D1
1N4007
D2
1N4007
1
10
T1
3 EE16 8
D6
SS15
L4
1.8
µH
C6
220
µF
25 V
C8
R13 56
µF
510
Ω
16 V
5 V, 300 mA
RTN
RF1
10
Ω
2W
C1
3.3
µF
400 V
C2
3.3
µF
400 V
D
C9
330 nF
50 V
LinkZero-AX
U1
LNK584DG
FB
BP/M
S
R9
1 kΩ
1%
85 - 265
VAC
Q1
MMBT3904
R16
750
Ω
R11
100
Ω
R12
20 kΩ
R10
20 kΩ
PD Set
D3
1N4007
D4
1N4007
C5
150 nF
25 V
C10
47
µF
25 V
C7
1 nF
50 V
R3
511
Ω
1%
SW1
Q2
MMBT3904
R4
10 kΩ
R14
2 kΩ
PD Reset
RTN
PI-6121-101210
Figure 4.
Schematic of Non-Isolated 1.5 W, 5 V, 300 mA, 0.00 W Standby Consumption Power Supply.
4
Rev. C 11/15
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LNK584-586
short-circuit output current is significantly less than 1 A, allowing low
current rating and low cost rectifier D6 to be used. Output circuitry is
designed to handle a continuous short-circuit on the power supply
output. In this design a preload resistor R13 is used at the output of
the supply to prevent automatic triggering of the power-down mode
when the load is removed.
Layout Considerations
LinkZero-AX Layout Considerations
Layout
See Figure 5 for a recommended circuit board layout for LinkZero-AX
(U1).
Single Point Grounding
Use a single point ground (Kelvin) connection from the input filter
capacitor to the area of copper connected to the SOURCE pins.
Bypass Capacitor (C
BP
), FEEDBACK Pin Noise Filter Capacitor
(C
FB
) and Feedback Resistors
To minimize loop area, these two capacitors should be physically
located as near as possible to the BYPASS and SOURCE pins, and
FEEDBACK pin and source pins respectively. Also note that to
minimize noise pickup, feedback resistors R
FB1
and R
FB2
are placed
close to the FEEDBACK pin.
Primary Loop Area
The area of the primary loop that connects the input filter capacitor,
transformer primary and LinkZero-AX should be kept as small as
possible.
Primary Clamp Circuit
An external clamp may be used to limit peak voltage on the DRAIN
pin at turn off. This can be achieved by using an RCD clamp or a
Zener (~200 V) and diode clamp across the primary winding. In all
cases, to minimize EMI, care should be taken to minimize the circuit
path from the clamp components to the transformer and LinkZero-AX
(U1).
Thermal Considerations
The copper area underneath the LinkZero-AX (U1) acts not only as a
single point ground, but also as a heat sink. As it is connected to the
quiet source node, this area should be maximized for good heat
sinking of U1. The same applies to the cathode of the output diode.
Y Capacitor
The placement of the Y-type capacitor (if used) should be directly
from the primary input filter capacitor positive terminal to the
common/return terminal of the transformer secondary. Such a
placement will route high magnitude common-mode surge currents
away from U1. Note: If an input π EMI filter is used, the inductor in
the
π
filter should be placed between the negative terminals on the
input filter capacitors.
Output Diode (D
O
)
For best performance, the area of the loop connecting the secondary
winding, the output diode (D
O
) and the output filter capacitor (C
O
)
should be minimized. In addition, sufficient copper area should be
provided at the anode and cathode terminals of the diode for heat
sinking. A larger area is preferred at the electrically “quiet” cathode
terminal. A large anode area can increase high frequency conducted
and radiated EMI. Resistor R
S
and C
S
represent the secondary side
RC snubber.
LinkZero-AX Power-Down (PD) Mode
Design Considerations
LinkZero-AX goes into power-down mode when 160 consecutive
switching cycles have been skipped. This condition occurs when the
output load is low or the FEEDBACK pin is pulled high (for example
through Q1 and R16 in Figure 4). The value of the BYPASS pin
capacitor must be high enough to sustain enough current through
R16 for more than the period of 160 switching cycles to successfully
trigger the power-down mode. At low-line input voltage (90 VAC) the
160 switching cycle period is ~1.6 ms as the internal oscillator
frequency is 100 kHz. However as the input line voltage increases,
the internal oscillator frequency is gradually reduced to keep the
maximum output power relatively constant. At high-line (265 VAC)
therefore, the internal oscillator frequency can be as low as 78 kHz
(see parameter table Note C). Therefore to provide sufficient margin
to ensure power-down mode is triggered it is recommended that the
power-down pulse (see Figure 1) is 2.5 ms (200 switching cycles at
80 kHz). LinkZero-AX stops switching once the power-down mode is
triggered. The IC does not resume switching until the BYPASS pin is
pulled below 1.5 V using the reset/wake up pulse (see Figure 1) and
then allowed to recharge back up to 5.85 V through the drain
connected 5.85 V regulator block. Transistor Q2 or mechanical switch
SW1 can be used for resetting the power-down mode either
electronically or mechanically.
It is important to design the power supply to ensure that load
transients and other external events do not unintentionally trigger
power-down mode by causing 160 consecutive switching cycles to be
skipped. It is recommended that a preload resistor is added to draw
~2% of the full load current (12 mA at 5 V in a 3 W power supply).
Although this reduces full load efficiency slightly, it has no influence
on the power consumption during power-down mode since the power
supply output is fully discharged under this condition. Low value
feedback resistors may also be used as a preload too. Recommended
value of the feedback resistors is such that they should draw ~1% of
full load current. Finally a capacitor in parallel to the high side
feedback resistor can be used to increase the speed of the loop (C9
in Figure 4).
These recommendations apply for full load to zero load transients.
For applications with more limited load range, the preload and the
capacitor in parallel to the high side feedback resistor may not be
necessary.
5
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Rev. C 11/15
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