TNY263-268
C8 680 pF
Y1 Safety
Shield
T1
D5
1N5819
L2
3.3 µ
H
1
4
8
+ 5 V
500 mA
C5
C6
C3
330 µF
16 V
100 µF
35 V
2.2 nF
R2
200 kΩ
RTN
D1
5
1N4005
D2
R8
270 Ω
1N4005
D6
1N4937
U2
LTV817
C1
3.3 µF
400 V
C2
3.3 µF
400 V
R7
100 Ω
85-265
VAC
D
S
RF1
8.2 Ω
EN/UV
BP
U1
TNY264
R9
47 Ω
R3
22 Ω
VR1
BZX79-
B3V9
TinySwitch-II
Fusible
Q1
2N3904
3.9 V
R1
1.2 kΩ
C3
0.1 µF
D3
1N4005
D4
1N4005
C7
10 µF
10 V
L1
2.2 mH
R4
R6
1 Ω
1.2 Ω
1/2 W 1/2 W
PI-2706-080404
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
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,
appliance control and ISDN or a DSL network termination.
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 fault protection. Auto-restart also saves the cost of adding
a fuse 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 does not rely on bias winding voltage. Consequently
this greatly simplifies designing chargers that must work down
to zero volts on the output.
the DRAIN pin (see Functional Description above). This
has two main benefits. First, for a nominal application, this
eliminatesthecostofabiaswindingandassociatedcomponents.
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.Forapplicationsthatrequireaverylowno-loadpower
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
thiscasewillbeclampedat6.3V.Thismethodwilleliminatethe
power draw from the DRAIN pin, thereby reducing the no-load
power consumption and improving full-load efficiency.
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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