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PDF MT7963 Data sheet ( Hoja de datos )
| Número de pieza | MT7963 | |
| Descripción | Dual Winding PSR AC-DC LED Driver | |
| Fabricantes | Maxic Technology | |
| Logotipo |  |
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Maximizing IC Performance
MT7963
High Accuracy, Dual Winding PSR AC-DC LED Driver
DESCRIPTION
MT7963 is a PWM controller for AC-DC LED
lighting. With primary side sensing and
regulation technology, no secondary side
feedback circuit is needed. Further, the loop
compensation components are also eliminated
while maintaining system stability. Integrated
with 650V power switch simplifies the system
design and improves the reliablity.
With Maxic’s proprietary current regulation
technique, the MT7963 achieves ±5% accuracy
of LED current along with excellent line
regulation and load regulation.
MT7963 provides plenty of protections, such as
such as over current protection(OCP), short
circuit protection (SCP)，over voltage protection
(OVP) and over temperature protection(OTP),etc,
to ensure system reliability.
FEATURES
Build in 650V power MOSFET
No auxiliary winding needed
Supporting 85V to 265V AC line voltage
range
Primary side sensing and regulation, no
need of secondary side feedback
High precision constant LED current (+/-5%)
Cycle-by-cycle peak current control
LED short-circuit protection
VDD under voltage lock-out protection
Over temperature protection
Available in SOP8 package
APPLICATION
LED bulb, Spotlight
LED lighting application
General purpose constant current source
Typical Application Circuit
NP:NS
LED+
Vin_ac
CBUS
CVCC RCS
MT7963
3 VCC
1
CS
4 SW
2
GND
8
NC
NC 7
DRAIN 6
5
DRAIN
LED-
MT7963 Rev. 1.15
www.maxictech.com
Copyright © 2015 Maxic Technology Corporation
Page 1
1 page  
Maximizing IC Performance
MT7963
High Accuracy, Dual Winding PSR AC-DC LED Driver
The primary side peak current is given by:
I P _ PK
500 (mA)
RCS
where RCS is the peak current sensing resistor
(refer to the Typical Application Circuit)
The LED current can be calculated by the
following equation:
I LED
I P _ PK
4
NP
NS
500
4 RCS
NP
NS
(mA)
where NP is the turns of the primary winding, NS
is the turns of the secondary winding, IP_PK is the
primary side peak current. Shown in the above
equation, the output current is determined by the
turns ratio of the transformer and the current
sense resistor value, insensitive to the
inductance of the transformer.
Switching Frequency
MT7963 is designed to operating in
discontinuous conduction mode and no external
loop compensation is needed for stability. The
maximum duty cycle is limited to 42%. It’s highly
recommended to limit the maximum switching
frequency less than 75kHz and the minimum
switching frequency more than 20kHz.
The switching frequency can be set by formula:
fSW
N
2
P
VLED
8
N
2
S
Lp
I
LED
where, NP is the turns of the primary winding, NS
is the turns of the secondary winding, Lp is the
transformer primary winding inductance.
Designing the switching frequency between
60kHz to 70kHz by properly set the transformer
parameters.
Protection Features
MT7963 provides various protections, such as
LED short / open-circuit protection, CS resistor
short-circuit protection, VCC under-voltage
protection and over temperature protection, etc.
When the LED is open-circuited, MT7963
immediately triggers over voltage protection logic,
ceasing switch toggling, the VCC voltage
gradually drops and reaches to the
under-voltage protection threshold, the system
will be re-started.
When the LED is short-circuited, the switching
frequency is only 5kHz, achieves low power
consumption.
Over-Current Protection
MT7963 immediately turns off the power
MOSFET once the voltage at CS pin exceeds
500mV. This cycle by cycle current limitation
scheme prevents the relevant components, such
as power MOSFET, transformer, etc. from
damage.
PCB Layout
The following rules should be followed in
MT7963 PCB layout:
Bypass Capacitor
The bypass capacitor on VCC pin should be as
close as possible to the pin.
Ground Path
The ground path for capacitor CVCC must connect
to the chip ground directly, without any noise
ground between them, such as SW capacitor
ground, the power ground path for RCS, etc.
Other small signal ground path also should
connect to the chip ground pin. The chip ground
and the SW capacitor ground should separately
connect to the power ground path for current
sense resistor RCS. Keep the power ground path
short and thick. Finally, all ground path connect
to the bulk capacitor CBUS ground terminal.
The Area of Power Loop
The area of main current loop should be as small
as possible to reduce EMI radiation, such as the
primary current loop, the snubber circuit and the
secondary rectifying loop.
MT7963 Rev. 1.15
www.maxictech.com
Copyright © 2015 Maxic Technology Corporation
Page 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MT7963.PDF ] | |
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