TNY284-290
™
TinySwitch-4
Family
Energy-Efficient, Off-Line Switcher With
Line Compensated Overload Power
Product Highlights
Lowest System Cost with Enhanced Flexibility
•
725 V rated MOSFET
•
Increases BV de-rating margin
•
Line compensated overload power – no additional components
•
Dramatically reduces max overload variation over universal
input voltage range
•
±5%
turn on UV threshold: line voltage sense with single
external resistor
•
Simple ON/OFF control, no loop compensation needed
•
Selectable current limit through BP/M capacitor value
•
Higher current limit extends peak power or, in open frame
applications, maximum continuous power
•
Lower current limit improves efficiency in enclosed
adapters/chargers
•
Allows optimum TinySwitch-4 choice by swapping devices
with no other circuit redesign
•
Tight I
2
f parameter tolerance reduces system cost
•
Maximizes MOSFET and magnetics utilization
•
ON-time extension – extends low-line regulation range/hold-up
time to reduce input bulk capacitance
•
Self-biased: no bias winding or bias components
•
Frequency jittering reduces EMI filter costs
•
Pin-out simplifies heat sinking to the PCB
•
SOURCE pins are electrically quiet for low EMI
Enhanced Safety and Reliability Features
•
Accurate hysteretic thermal shutdown protection with auto-
matic recovery eliminates need for manual reset
•
Auto-restart delivers <3% of maximum power in short-circuit
and open loop fault conditions
•
Output overvoltage shutdown with optional Zener
•
Fast AC reset with optional UV external resistor
•
Very low component count enhances reliability and enables
single-sided printed circuit board layout
•
High bandwidth provides fast turn-on with no overshoot and
excellent transient load response
•
Extended creepage between DRAIN and all other pins improves
field reliability
EcoSmart
™
– Extremely Energy Efficient
•
Easily meets all global energy efficiency regulations
•
No-load <30 mW with bias winding, <150 mW at 265 VAC
without bias winding
•
ON/OFF control provides constant efficiency down to very light
loads – ideal for mandatory CEC regulations and EuP standby
requirements
Applications
•
PC Standby and other auxiliary supplies
•
DVD/PVR and other low power set top decoders
•
Supplies for appliances, industrial systems, metering, etc
•
Chargers/adapters for cell/cordless phones, PDAs, digital
cameras, MP3/portable audio, shavers, etc.
www.powerint.com
+
+
Figure 1.
Typical Standby Application.
SO-8C (D Package)
Figure 2.
Package Options.
DIP-8C (P Package)
eSOP-12B (K Package)
Output Power Table
230 VAC ± 15%
Product
3
TNY284P/D/K
TNY285P/D
TNY285K
TNY286P/D
TNY286K
TNY287P
TNY287D
TNY287K
TNY288P
TNY288D
TNY288K
TNY289P
TNY289K
TNY290P
TNY290K
Adapter
1
6W
8.5 W
11 W
10 W
13.5 W
13 W
11.5 W
18 W
16 W
14.5 W
23 W
18 W
25 W
20 W
28 W
Peak or
Open
Frame
2
11 W
15 W
15 W
19 W
19 W
23.5 W
23.5 W
23.5 W
28 W
26 W
28 W
32 W
32 W
36.5 W
36.5 W
85-265 VAC
Adapter
1
5W
6W
7.5 W
7W
9.5 W
8W
7W
11 W
10 W
9W
14.5 W
12 W
17 W
14 W
20 W
Peak or
Open
Frame
2
8.5 W
11.5 W
11.5 W
15 W
15 W
18 W
18 W
18 W
21.5 W
19.5 W
21.5 W
25 W
25 W
28.5 W
28.5 W
Table 1. Output Power Table.
Notes:
1. Minimum continuous power in a typical non-ventilated enclosed adapter
measured at +50 °C ambient. Use of an external heat sink will increase power
capability.
2. Minimum peak power capability in any design or minimum continuous power in
an open frame design (see Key Applications Considerations).
3. Packages: P: DIP-8C, D: SO-8C, K: eSOP-12B. See Part Ordering Information.
August 2013
TNY284-290
BYPASS/
MULTI-FUNCTION
(BP/M)
REGULATOR
5.85 V
LINE UNDERVOLTAGE
25
µA
AUTO-
RESTART
COUNTER
6.4 V
RESET
FAULT
PRESENT
BYPASS PIN
UNDER-VOLTAGE
DRAIN
(D)
+
115
µA
BYPASS
-
CAPACITOR
5.85 V
SELECT AND
V
I
4.9 V
LIMIT
CURRENT
LIMIT STATE
MACHINE
LINE
COMPENSATION
CURRENT LIMIT
COMPARATOR
ENABLE
-
+
1.0 V + V
T
JITTER
CLOCK
DCMAX
THERMAL
SHUTDOWN
ENABLE/
UNDER-
VOLTAGE
(EN/UV)
1.0 V
OSCILLATOR
S
Q
R
Q
OVP
LATCH
LEADING
EDGE
BLANKING
SOURCE
(S)
PI-6639-081613
Figure 3.
Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
This pin is the power MOSFET drain connection. It provides
internal operating current for both start-up and steady-state
operation.
BYPASS/MULTI-FUNCTION (BP/M) Pin:
This pin has multiple functions:
•
It is the connection point for an external bypass capacitor for
the internally generated 5.85 V supply.
•
It is a mode selector for the current limit value, depending on
the value of the capacitance added. Use of a 0.1
μF
capaci-
tor results in the standard current limit value. Use of a 1
μF
capacitor results in the current limit being reduced to that of
the next smaller device size. Use of a 10
μF
capacitor results
in the current limit being increased to that of the next larger
device size for TNY285-290.
•
It provides a shutdown function. When the current into the
bypass pin exceeds ISD, the device latches off until the BP/M
voltage drops below 4.9 V, during a power-down or, when the
UV function is employed with external resistors connected to
the BP/UV pin, by taking the UV/EN pin current below I
UV
minus the reset hysteresis (Typ. 18.75
μA).
This can be used
EN/UV 1
BP/M 2
D Package (SO-8C)
8S
7S
6S
D4
5S
EN/UV 1
Exposed Pad (On Bottom)
Internally Connected to
SOURCE Pin
P Package (DIP-8C)
8S
7S
6S
BP/M 2
K Package
(eSOP-12B)
D4
5S
EN/UV 1
BP/M 2
N/C 3
N/C 4
D6
Figure 4.
Pin Configuration.
12 S
11 S
10 S
9S
8S
7S
PI-6577-053112
2
Rev. B 08/13
www.powerint.com
TNY284-290
to provide an output overvoltage function with a Zener
connected from the BYPASS/MULTI-FUNCTIONAL pin to a
bias winding supply.
ENABLE/UNDERVOLTAGE (EN/UV) Pin:
This pin has dual functions: enable input and line undervoltage
sense. During normal operation, switching of the power
MOSFET is controlled by this pin. MOSFET switching is
terminated when a current greater than a threshold current is
drawn from this pin. Switching resumes when the current being
pulled from the pin drops to less than a threshold current. A
modulation of the threshold current reduces group pulsing. The
threshold current is between 75
μA
and 115
μA.
The ENABLE/UNDERVOLTAGE pin also senses line
undervoltage conditions through an external resistor connected
to the DC line voltage. If there is no external resistor connected
to this pin, TinySwitch-4 detects its absence and disables the
line undervoltage function.
SOURCE (S) Pin:
This pin is internally connected to the output MOSFET source
for high-voltage power return and control circuit common.
Oscillator
The typical oscillator frequency is internally set to an average of
132 kHz. Two signals are generated from the oscillator: the
maximum duty cycle signal (DC
MAX
) and the clock signal that
indicates the beginning of each cycle.
The oscillator incorporates circuitry that introduces a small
amount of frequency jitter, typically 8 kHz peak-to-peak, to
minimize EMI emission. The modulation rate of the frequency
jitter is set to 1 kHz to optimize EMI reduction for both average
and quasi-peak emissions. The frequency jitter should be
measured with the oscilloscope triggered at the falling edge of
the DRAIN waveform. The waveform in Figure 5 illustrates the
frequency jitter.
Enable Input and Current Limit State Machine
The enable input circuit at the ENABLE/UNDERVOLTAGE pin
consists of a low impedance source follower output set at 1.2 V.
The current through the source follower is limited to 115
μA.
When the current out of this pin exceeds the threshold current,
a low logic level (disable) is generated at the output of the
enable circuit, until the current out of this pin is reduced to less
than the threshold current. This enable circuit output is
sampled at the beginning of each cycle on the rising edge of the
clock signal. If high, the power MOSFET is turned on for that
cycle (enabled). If low, the power MOSFET remains off
(disabled). Since the sampling is done only at the beginning of
each cycle, subsequent changes in the ENABLE/UNDER-
VOLTAGE pin voltage or current during the remainder of the
cycle are ignored.
The current limit state machine reduces the current limit by
discrete amounts at light loads when TinySwitch-4 is likely to
switch in the audible frequency range. The lower current limit
raises the effective switching frequency above the audio range
and reduces the transformer flux density, including the
associated audible noise. The state machine monitors the
sequence of enable events to determine the load condition and
adjusts the current limit level accordingly in discrete amounts.
Under most operating conditions (except when close to
no-load), the low impedance of the source follower keeps the
voltage on the ENABLE/UNDERVOLTAGE pin from going much
below 1.2 V in the disabled state. This improves the response
time of the optocoupler that is usually connected to this pin.
5.85 V Regulator and 6.4 V Shunt Voltage Clamp
The 5.85 V regulator charges the bypass capacitor connected
to the BYPASS pin to 5.85 V by drawing a current from the
voltage on the DRAIN pin whenever the MOSFET is off. The
BYPASS/MULTI-FUNCTION pin is the internal supply voltage
node. When the MOSFET is on, the device operates from the
energy stored in the bypass capacitor. Extremely low power
consumption of the internal circuitry allows TinySwitch-4 to
operate continuously from current it takes from the DRAIN pin.
A bypass capacitor value of 0.1
μF
is sufficient for both high
frequency decoupling and energy storage.
10
TinySwitch-4 Functional Description
TinySwitch-4 combines a high-voltage power MOSFET switch
with a power supply controller in one device. Unlike conventional
PWM (pulse width modulator) controllers, it uses a simple
ON/OFF control to regulate the output voltage.
The controller consists of an oscillator, enable circuit (sense and
logic), current limit state machine, 5.85 V regulator, BYPASS/
MULTI-FUNCTION pin undervoltage, overvoltage circuit, and
current limit selection circuitry, over-temperature protection,
current limit circuit, leading edge blanking, and a 725 V power
MOSFET. TinySwitch-4 incorporates additional circuitry for line
undervoltage sense, auto-restart, adaptive switching cycle
on-time extension, and frequency jitter. Figure 3 shows the
functional block diagram with the most important features.
PI-2741-041901
600
500
V
DRAIN
400
300
200
100
0
136 kHz
128 kHz
0
Figure 5.
Frequency Jitter.
5
Time (µs)
3
www.powerint.com
Rev. B 08/13
TNY284-290
In addition, there is a 6.4 V shunt regulator clamping the
BYPASS/MULTI-FUNCTION pin at 6.4 V when current is
provided to the BYPASS/MULTI-FUNCTION pin through an
external resistor. This facilitates powering of TinySwitch-4
externally through a bias winding to decrease the no-load
consumption to well below 50 mW.
BYPASS/MULTI-FUNCTION Pin Undervoltage
The BYPASS/MULTI-FUNCTION pin undervoltage circuitry
disables the power MOSFET when the BYPASS/MULTI-
FUNCTION pin voltage drops below 4.9 V in steady state
operation. Once the BYPASS/MULTI-FUNCTION pin voltage
drops below 4.9 V in steady state operation, it must rise back to
5.85 V to enable (turn-on) the power MOSFET.
Over Temperature Protection
The thermal shutdown circuitry senses the die temperature.
The threshold is typically set at 142 °C with 75 °C hysteresis.
When the die temperature rises above this threshold the power
MOSFET is disabled and remains disabled until the die
temperature falls by 75 °C, at which point it is re-enabled. A
large hysteresis of 75 °C (typical) is provided to prevent over-
heating of the PC board due to a continuous fault condition.
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 current limit state machine reduces the current limit
threshold by discrete amounts under medium and light loads.
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 secondary-side
rectifier reverse recovery time will not cause premature
termination of the switching pulse.
Auto-Restart
In the event of a fault condition such as output overload, output
short-circuit, or an open loop condition, TinySwitch-4 enters
PI-4098-082305
into auto-restart operation. An internal counter clocked by the
oscillator is reset every time the ENABLE/UNDERVOLTAGE pin
is pulled low. If the ENABLE/UNDERVOLTAGE pin is not pulled
low for 64 ms, the power MOSFET switching is normally
disabled for 2.5 seconds (except in the case of line undervoltage
condition, in which case it is disabled until the condition is
removed). The auto-restart alternately enables and disables the
switching of the power MOSFET until the fault condition is
removed. Figure 6 illustrates auto-restart circuit operation in the
presence of an output short-circuit.
In the event of a line undervoltage condition, the switching of
the power MOSFET is disabled beyond its normal 2.5 seconds
until the line undervoltage condition ends.
Adaptive Switching Cycle On-Time Extension
Adaptive switching cycle on-time extension keeps the cycle on
until current limit is reached, instead of prematurely terminating
after the DC
MAX
signal goes low. This feature reduces the
minimum input voltage required to maintain regulation, extending
hold-up time and minimizing the size of bulk capacitor required.
The on-time extension is disabled during the start-up of the
power supply, until the power supply output reaches regulation.
Line Undervoltage Sense Circuit
The DC line voltage can be monitored by connecting an
external resistor from the DC line to the ENABLE/
UNDERVOLTAGE pin. During power-up or when the switching
of the power MOSFET is disabled in auto-restart, the current
into the ENABLE/UNDERVOLTAGE pin must exceed 25
μA
to
initiate switching of the power MOSFET. During power-up, this
is accomplished by holding the BYPASS/MULTI-FUNCTION pin
to 4.9 V while the line undervoltage condition exists. The
BYPASS/MULTI-FUNCTION pin then rises from 4.9 V to 5.85 V
when the line undervoltage condition goes away. When the
switching of the power MOSFET is disabled in auto-restart
mode and a line undervoltage condition exists, the auto-restart
counter is stopped. This stretches the disable time beyond its
normal 2.5 seconds until the line undervoltage condition ends.
The line undervoltage circuit also detects when there is no
external resistor connected to the ENABLE/UNDERVOLTAGE
pin (less than ~2
μA
into the pin). In this case the line
undervoltage function is disabled.
TinySwitch-4 Operation
TinySwitch-4 devices operate in the current limit mode. When
enabled, the oscillator turns the power MOSFET on at the
beginning of each cycle. The MOSFET is turned off when the
current ramps up to the current limit or when the DC
MAX
limit is
reached. Since the highest current limit level and frequency of
a TinySwitch-4 design are constant, the power delivered to the
load is proportional to the primary inductance of the transformer
and peak primary current squared. Hence, designing the supply
involves calculating the primary inductance of the transformer
for the maximum output power required. If the TinySwitch-4 is
appropriately chosen for the power level, the current in the
calculated inductance will ramp up to current limit before the
DC
MAX
limit is reached.
300
200
100
0
10
V
V
DRAIN
5
0
DC-OUTPUT
0
Figure 6.
Auto-Restart Operation.
2500
5000
Time (ms)
4
Rev. B 08/13
www.powerint.com
TNY284-290
Enable Function
TinySwitch-4 senses the ENABLE/UNDERVOLTAGE pin to
determine whether or not to proceed with the next switching
cycle. The sequence of cycles is used to determine the current
limit. Once a cycle is started, it always completes the cycle
(even when the ENABLE/UNDERVOLTAGE pin changes state
half way through the cycle). This operation results in a power
supply in which the output voltage ripple is determined by the
output capacitor, amount of energy per switch cycle and the
delay of the feedback.
The ENABLE/UNDERVOLTAGE pin signal is generated on the
secondary by comparing the power supply output voltage with
a reference voltage. The ENABLE/UNDERVOLTAGE pin signal
is high when the power supply output voltage is less than the
reference voltage. In a typical implementation, the ENABLE/
UNDERVOLTAGE pin is driven by an optocoupler. The collector
of the optocoupler transistor is connected to the ENABLE/
UNDERVOLTAGE pin and the emitter is connected to the
SOURCE pin. The optocoupler LED is connected in series with
V
EN
CLOCK
DC
V
EN
CLOCK
DC
MAX
MAX
I DRAIN
I DRAIN
V DRAIN
V DRAIN
PI-2749-082305
PI-2667-082305
Figure 7.
Operation at Near Maximum Loading.
Figure 8.
Operation at Moderately Heavy Loading.
V
EN
CLOCK
DC
V
EN
CLOCK
DC
MAX
MAX
I DRAIN
I DRAIN
V DRAIN
V DRAIN
PI-2377-082305
PI-2661-082305
Figure 9.
Operation at Medium Loading.
Figure 10. Operation at Very Light Load.
5
www.powerint.com
Rev. B 08/13
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