TNY264/266-268
C8 680 pF
Y1 Safety
Shield
T1
L2
D5
3.3
1N5819
µH
1
4
8
5
+ 5 V
C6
100 µF
35 V
500 mA
C3
2.2 nF
C5
330 µF
16 V
R2
200 kΩ
RTN
D1
1N4005
D2
1N4005
R8
270 Ω
D6
1N4937
U2
LTV817
R7
100 Ω
C1
3.3 µF
400 V
C2
3.3 µF
400 V
85-265
VAC
RF1
8.2 Ω
D
S
EN/UV
BP
U1
TNY264
TinySwitch-II
R9
47 Ω
Q1
2N3904
R3
22 Ω
Fusible
R1
1.2 kΩ
VR1
BZX79-
B3V9
C3
D3
1N4005
D4
1N4005
0.1 µF
C7
10 µF
10 V
3.9 V
L1
2.2 mH
R4
R6
1.2 Ω 1 Ω
1/2 W 1/2 W
PI-2706-052301
Figure 14. 2.5 W Constant Voltage, Constant Current Battery Charger with Universal Input (85-265 VAC).
The TinySwitch-II 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 a bias winding and associated components.
Secondly, for battery charger applications, the current-voltage
characteristic often allows the output voltage to fall close to
zero volts while still delivering power. This type of application
normally requires a forward-bias winding which has many
more associated components. With TinySwitch-II, neither are
necessary. For applications that require a very low no-load
power consumption (50 mW), a resistor from a bias winding to
the BYPASS pin can provide the power to the chip. The
minimum recommended current supplied is 750 µA. The
BYPASS pin in this case will be clamped at 6.3 V. This method
will eliminate the power draw from the DRAIN pin, thereby
reducing the no-load power consumption and improving full-
load efficiency.
Application Examples
The TinySwitch-II is ideal for low cost, high efficiency power
supplies in a wide range of applications such as cellular phone
chargers, PC standby, TV standby, AC adapters, motor control,
appliancecontrolandISDNoraDSLnetworktermination. The
132 kHz operation allows the use of a low cost EE13 or EF12.6
core transformer while still providing good efficiency. The
frequency jitter in TinySwitch-II makes it possible to use a
singleinductor(ortwosmallresistorsforunder3Wapplications
if lower efficiency is acceptable) in conjunction with two input
capacitors for input EMI filtering. The auto-restart function
removes the need to oversize the output diode for short circuit
conditions allowing the design to be optimized for low cost and
maximum efficiency. In charger applications, it eliminates the
need for a second optocoupler and Zener diode for open loop
faultprotection.Auto-restartalsosavesthecostofaddingafuse
or increasing the power rating of the current sense resistors to
survive reverse battery conditions. For applications requiring
under-voltage lock out (UVLO), such as PC standby, the
TinySwitch-II eliminates several components and saves cost.
TinySwitch-II is well suited for applications that require
constant voltage and constant current output. As TinySwitch-II
is always powered from the input high voltage, it therefore
doesnotrelyonbiaswindingvoltage.Consequentlythisgreatly
simplifiesdesigningchargersthatmustworkdowntozerovolts
on the output.
Current Limit Operation
Each switching cycle is terminated when the DRAIN current
reaches the current limit of the TinySwitch-II. Current limit
operation provides good line ripple rejection and relatively
constant power delivery independent of input voltage.
BYPASS Pin Capacitor
The BYPASS pin uses a small 0.1 µF ceramic capacitor for
decoupling the internal power supply of the TinySwitch-II.
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POWERINT [ Power Integrations ]
