ST AN2063 Application note
AN2063
Obsolete Product(s) - Obsolete Product(s) Obsolete Product(s) - Obsolete Product(s)
®
- APPLICATION NOTE
VIPower: LOW CONSUMPTION
STAND-BY POWER WITH VIPerX2A FAMILY
GENERAL FEATURES
■ ULTRA LOW STANDBY POWER DISSIPATION
■ BURST MODE OPERATION IN STAND-BY
■ 72% TYPICAL EFFICIENCY
■ CURRENT MODE CONTROLLER
■ OUTPUT SHORT CIRCUIT PROTECTION
■ THERMAL SHUT DOWN PROTECTION
1. INTRODUCTION
The new regulations on t he power supply stand-by consumption f or the battery charger are becoming
more stringent. Thanks to VIPerX2A family low power consumption, it is possible to build a battery
charger with a power consumption in stand-by mode with no-load of 100mW.
In table 1 this charger solution with VIPer12A is presented.
Tab le 1: Operation cond itions
Parameters Limits
Input voltage range 90 to 264VAC
Input frequency range 50-60Hz
Output voltage 5V
Output current 800mA
Output power 4W
Efficiency 72% typical
Line regulation 0.5%
Load regulation 1%
Output ripple voltage 30mVpp
Safety Short circuit protection
2. VIPer12A DESCRIPTION
VIPer12A is a high voltage integrated circuits intended to be used on off line power supply as a primary
side switch. in a monolithic structure housed in DIP-8 or SO-8 package it includes a PWM driver, a
Power MOSFET with 730V breakdown voltage, a start-up c ircuit and several protection c ircuit. It takes
advantage from minimizing the external part count, reducin g the products size and power consum ption.
The application note describes the results obtained when VIPer12A is used in mobile charger
application.
October 2004 1/10
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AN2063 - APPLICATION N OTE
3. PCB LAY-OUT
The layout of the switching power supply is very important in order to minimize noise and interference.
The high switching current loop areas should be kept as small as possible to reduce the radiated
electromagnetic emissions. Figure 1 shows the board layout.
In order to meet safety agencies' requirements, there needs to be an adequate clearance of about 6mm
between the high and low voltage sides of the circuit.
The power grounds need to be separated from the small signal grounds. The current in the power ground
changes very quickly in time; resulting in large transient that induces voltage shifts, which in turn can
disturb critical, sensitive small signal currents. Any disturbance or shift of ground in the small signal
ground will upset c ritical reference pat hs. Therefore, poor g rounding rout ing can ma nifest itself as poor
load regulation, or excessive switching noises on the output.
Figure 1: Demo board bottom foil (not in scale)
4. GENERAL CIRCUIT DESCRIPTION
This board is a fly-back regulator delivering 0.8A at 5V. The AC input is rectified and filtered by the diode
D1, D2, D3, D4, the bulk capacitor C1, and C2 to generate the high voltage DC bus applied to the
primary winding of the transformer, TR1. C1, L1, and C2 provide EMI filtering for the circuit.D9, D10 form
the snubber circuit needed to reduce the leakage spike and voltage ringing on the drain pin of VIPer12A.
The output voltage is reg ulated with a TL431 (U3) via an optocoupler (U2) to the feedback pin. The
output voltage ripple is controlled with the capacitor, C7, with an additional LC PI filter configuration made
up of L2 and C8. It is possible to modify the output voltages by changing the transformer turns ratio and
modifying the resistance values of R6 and R7 in the feedback loop.
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Figure 2: Application schematic
D
AN2063 - APPLICATION N OTE
R0
1N4007
D3
10
1N4007
D1
1N4007
D4
400V
4.7µ
C1
400V
4.7µ
C2
50V
33µ
C5
10µ
33V
C6
47n
C4
PC817
U2
SOURCE
FB
CONTRO L
VDD
1N4148
DRAIN
D7
Opti on E
VIPer12A
U1
1N4007
D2
680µ
L1
Opti on A
1N4148
D6
Opti on C
STTH1L06
D9
P6KE180
D10
R2
0
Opti on B
C111n1kV
TL431
U3
PC817
U2
Opti on E
1.5k
100n
C10
43k
R6
R4
43k
R7
220
R1
0
T1
1N5822
D8
470µ
16V
C7
R3
4.7µ
L2
220µ
10V
C8
C
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