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
•
•
•
+
DC
Output
+
•
•
•
•
•
•
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
Wide-Range
High-Voltage
DC Input
TinySwitch-4
D
EN/UV
BP/M
S
PI-6578-020915
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
Enhanced Safety and Reliability Features
•
•
•
•
•
•
Accurate hysteretic thermal shutdown protection with automatic
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
bias winding
•
Easily meets all global energy efficiency regulations
•
No-load <30 mW with bias winding, <150 mW at 265 VAC without
•
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.
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.
www.power.com
August 2016
This Product is Covered by Patents and/or Pending Patent Applications.
TNY284-290
BYPASS/
MULTI-FUNCTION
(BP/M)
REGULATOR
5.85 V
LINE UNDERVOLTAGE
25
µA
AUTO-
RESTART
COUNTER
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
-
+
ENABLE/
UNDER-
VOLTAGE
(EN/UV)
1.0 V + V
T
JITTER
CLOCK
DCMAX
THERMAL
SHUTDOWN
1.0 V
OSCILLATOR
S
Q
R
Q
6.4 V
OVP
LATCH
LEADING
EDGE
BLANKING
SOURCE
(S)
PI-6639-072115
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
capacitor 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 to provide an output overvolt-
age function with a Zener connected from the BYPASS/MULTI-
FUNCTIONAL pin to a bias winding supply.
D Package (SO-8C)
EN/UV 1
BP/M 2
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-6577-021015
2
Rev. D 08/16
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TNY284-290
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.
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 trans-
former 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.
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.
SOURCE (S) Pin:
This pin is internally connected to the output MOSFET source for
high-voltage power return and control circuit common.
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.
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.
PI-2741-021015
600
500
V
DRAIN
400
300
200
100
0
136 kHz
128 kHz
0
5
Time (µs)
10
Figure 5.
Frequency Jitter.
3
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Rev. D 08/16
TNY284-290
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 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-
PI-4098-021015
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.
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 a Zener diode across the DC output voltage
to be regulated. When the output voltage exceeds the target
regulation voltage level (optocoupler LED voltage drop plus Zener
voltage), the optocoupler LED will start to conduct, pulling the
ENABLE/UNDERVOLTAGE pin low. The Zener diode can be replaced
by a TL431 reference circuit for improved accuracy.
ON/OFF Operation with Current Limit State Machine
The internal clock of the TinySwitch-4 runs all the time. At the
beginning of each clock cycle, it samples the ENABLE/UNDERVOLTAGE
pin to decide whether or not to implement a switch cycle, and based
on the sequence of samples over multiple cycles, it determines the
appropriate current limit. At high loads, the state machine sets the
current limit to its highest value. At lighter loads, the state machine
sets the current limit to reduced values.
At near maximum load, TinySwitch-4 will conduct during nearly all of
its clock cycles (Figure 7). At slightly lower load, it will “skip”
additional cycles in order to maintain voltage regulation at the power
supply output (Figure 8). At medium loads, cycles will be skipped and
the current limit will be reduced (Figure 9). At very light loads, the
current limit will be reduced even further (Figure 10). Only a small
300
200
100
0
10
5
0
V
DC-OUTPUT
V
DRAIN
0
Figure 6.
Auto-Restart Operation.
2500
5000
Time (ms)
4
Rev. D 08/16
www.power.com
TNY284-290
percentage of cycles will occur to satisfy the power consumption of
the power supply.
The response time of the ON/OFF control scheme is very fast
compared to PWM control. This provides tight regulation and
excellent transient response.
Power-Up/Down
The TinySwitch-4 requires only a 0.1
μF
capacitor on the BYPASS/
MULTI-FUNCTION pin to operate with standard current limit.
Because of its small size, the time to charge this capacitor is kept to
an absolute minimum, typically 0.6 ms. The time to charge will vary
in proportion to the BYPASS/MULTI-FUNCTION pin capacitor value
when selecting different current limits. Due to the high bandwidth
of the ON/OFF feedback, there is no overshoot at the power supply
output. When an external resistor (4 MW) is connected from the
positive DC input to the ENABLE/UNDERVOLTAGE pin, the power
MOSFET switching will be delayed during power-up until the DC line
voltage exceeds the threshold (100 V). Figures 11 and 12 show the
power-up timing waveform in applications with and without an
external resistor (4 MW) connected to the ENABLE/UNDERVOLTAGE
V
EN
CLOCK
DC
MAX
V
EN
CLOCK
DC
MAX
I
DRAIN
I
DRAIN
V
DRAIN
V
DRAIN
PI-2749-021015
PI-2667-021015
Figure 7.
Operation at Near Maximum Loading.
Figure 8.
Operation at Moderately Heavy Loading.
V
EN
CLOCK
DC
MAX
V
EN
CLOCK
DC
MAX
I
DRAIN
I
DRAIN
V
DRAIN
V
DRAIN
PI-2377-021015
PI-2661-021015
Figure 9.
Operation at Medium Loading.
Figure 10. Operation at Very Light Load.
5
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Rev. D 08/16
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