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TYN256P Schematic ( PDF Datasheet ) - Power Integrations Inc.

Teilenummer TYN256P
Beschreibung Energy Efficient/ Low Power Off-line Switcher
Hersteller Power Integrations Inc.
Logo Power Integrations  Inc. Logo 




Gesamt 20 Seiten
TYN256P Datasheet, Funktion
TNY256
TinySwitch TM Plus
Energy Efficient, Low Power Off-line Switcher
®
Product Highlights
TinySwitch Plus Features
Extended power range
Fully integrated auto-restart reduces short circuit current
Line under-voltage sense eliminates turn-off glitches
Frequency jittering dramatically reduces EMI (5 to 10 dB)
TO-220 package option
Lowest Cost, Low Power Switcher Solution
Lower cost than RCC, discrete PWM and other integrated/
hybrid solutions
Cost effective replacement for bulky linear adapters
Lowest component count
Simple ON/OFF control no loop compensation components
No bias winding simpler, lower cost transformer
Designed to work with low cost external components
Extremely Energy Efficient
Consumes only 30/60 mW at 115/230 VAC with no load
Meets Blue Angel, Energy Star, Energy 2000 and
200mW European cell phone requirements for standby
Saves $1 to $4 per year in energy costs (at $0.12/kWHr)
compared to bulky linear adapters
Ideal for cellular phone chargers and adapters
High Performance at Low Cost
High voltage powered ideal for charger applications
High bandwidth provides fast turn on with no overshoot
Current limit operation rejects line frequency ripple
Built-in current limit and thermal protection
Description
The TNY256 extends the power range of the TinySwitch family
of energy efficient, low power off-line switchers. TinySwitch
devices use a breakthrough design to provide the lowest cost,
high efficiency, off-line switching solution for low power
applications. They integrate a 700 V power MOSFET, oscillator,
high voltage switched current source, current limit and thermal
shutdown circuitry into a single, monolithic device. The devices
start-up and operate on power derived from the DRAIN voltage,
eliminating the need for a transformer bias winding and associated
circuitry. TinySwitch's low operating current allows power
supply no-load consumption to be kept under 100 mW, even at
265 VAC input.
+
Optional
UV Resistor
Wide-Range
HV DC Input
D
TinySwitch Plus
S
EN/UV
BP
Figure 1. Typical Standby Application.
+
DC Output
PI-2363-022699
OUTPUT POWER CAPABILITY*
ORDER
PART
NUMBER
PACKAGE
230 VAC or
115 VAC
w/Doubler
85-265
VAC
TNY256P
TNY256G
TNY256Y
DIP-8
SMD-8
TO-220-7B
8-15 W
8-19 W
5-10 W
5-11 W
Table 1. * The low end of the power ranges shown represent enclosed
adapters with minimal heat sinking whereas, the high end of the power
ranges represent open frame power supplies with adequate heat
sinking, both measured at an ambient of 50 oC. Please refer to the Key
Application Considerations section for more details.
The TinySwitch Plus incorporates auto-restart, line under-voltage
sense, and frequency jittering features. The auto-restart circuit
safely limits output power during fault conditions such as output
short or open loop. The auto-restart circuit is fully integrated and
does not require external timing components. The line under-
voltage sense threshold can be externally programmed using a line
sense resistor. During start-up, this feature keeps the TNY256 off
until the input line voltage reaches the under-voltage threshold.
When the input line voltage is removed, the line under-voltage
circuit prevents auto-restart attempts after the output goes out of
regulation. This eliminates power down glitches caused by the
slow discharge of input storage capacitors present in applications
such as standby supplies. A single resistor is used to implement
this feature, eliminating what normally takes five to six components.
The line sense resistor is optional. The TNY256 operating frequency
of 130 kHz is jittered (frequency modulated) to reduce both quasi-
peak and average EMI, minimizing filtering costs.
August 1999






TYN256P Datasheet, Funktion
TNY256
200
100 VDC-BUS
0
400
300
200 VDRAIN
100
0
0 .5
Time (s)
Figure 10. Normal Power-down Timing.
1
power MOSFET will switch for 32 ms after the output loses
regulation. The power MOSFET will then remain off without
any glitches since the under-voltage function prohibits restarts
when the line voltage is low.
Figure 10 illustrates a typical power-down timing waveform of
TNY256. Figure 11 illustrates a very slow power-down timing
waveform of TNY256 as in standby applications. The external
resistor (2 M) is connected to the EN/UV pin in this case to
prevent restarts.
The TNY256 does not require a bias winding to provide power
to the chip, because it draws the power directly from the DRAIN
pin (see Functional Description above). This has two main
benefits. First, for a nominal application, this eliminates the
cost of an extra bias winding and associated components.
Secondly, for charger applications, the current-voltage
characteristic often allows the output voltage to fall to low
values while still delivering power. This type of application
normally requires a forward-bias winding which has many
more associated components, none of which are necessary with
the TNY256.
Current Limit Operation
Each switching cycle is terminated when the DRAIN current
reaches the current limit of the TNY256. For a given primary
inductance and input voltage, the duty cycle is constant.
However, the duty cycle does change inversely with the input
voltage providing voltage feed-forwardadvantages: good
line ripple rejection and relatively constant power delivery
independent of the input voltage.
BYPASS Pin Capacitor
The BYPASS pin uses a small 0.1 µF ceramic capacitor for
decoupling the internal power supply of the TNY256.
200
100 VDC-BUS
0
400
300
200
V
DRAIN
100
0
0 2.5
Time (s)
Figure 11. Slow Power-down Timing with External (2 M)
Resistor Connected to EN/UV Pin.
Application Example
5
The TNY256 is ideal for low cost, high efficiency power
supplies in a wide range of applications such as PC standby,
cellular phone chargers, AC adapters, motor control, appliance
control and ISDN network termination. The 130 kHz operation
allows the use of a low cost EE16 core transformer while still
providing good efficiency. The frequency jitter in TNY256
makes it possible to use a single inductor (or two small resistors
if lower efficiency is acceptable) in conjunction with two input
capacitors for input EMI filtering up to the 10W level. The
auto-restart function allows the design to be optimized for
maximum efficiency without consideration for short-circuit
current on the secondary. For applications requiring under-
voltage lockout (UVLO), the TNY256 eliminates several
components and saves cost.
As an example, Figure12 shows a 9 V, 0.6 A, AC adapter
operating from a universal input range (85-265 VAC). The AC
input is rectified and filtered by D1-D4, C1 and C2 to create a
high voltage DC bus which is connected to T1. Inductor L1
forms a pi-filter in conjunction with C1 and C2. The resistor R1
damps resonance in inductor L1. The frequency jitter in
TNY256 allows it to meet worldwide conducted EMI standards
using a simple pi-filter in combination with a small value
Y1-capacitor C5 and a shield winding between primary and
secondary windings inside transformer T1. Diode D5, capacitor
C3 and resistor R3 form an RCD clamp circuit that limits the
turn-off voltage spike to a safe value on the TNY256 DRAIN
pin.
The secondary winding is rectified and filtered by D6, C6 and
C7 to provide the 9 V output. Additional filtering is provided
by L3 and C8. The output voltage is determined by the resistor
network R7 and R8. Resistor R9 maintains a bias current
6B
8/99

6 Page









TYN256P pdf, datenblatt
TNY256
D EN/UV
SS
SS
S BP
2 M
0.1 µF
470
5W
S2
470
S1
150 V
10 V
50 V
NOTE: This test circuit is not applicable for current limit or output characteristic measurements.
PI-2352-011899
Figure 14. TinySwitch General Test Circuit.
t2
HV
90%
t1
90%
DRAIN
VOLTAGE
0V
D = t1
t2
10%
Figure 15. TinySwitch Duty Cycle Measurement.
PI-2048-050798
DCMAX
(internal signal)
tP
EN/UV
VDRAIN
1
t=
P fOSC
tEN/UV
Figure 16. TinySwitch Output Enable Timing.
PI-2364-012699
12 B
8/99
1.3 tLEB (Blanking Time)
1.2
1.1
1.0
0.9
0.8
0.7
0.6 IINIT(MIN)
0.5 ILIMIT(MAX) @ 25 ˚C
0.4 ILIMIT(MIN) @ 25 ˚C
0.3
0.2
0.1
0
0 1 23 45 678
Time (µs)
Figure 17. Current Limit Envelope.

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