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PDF MT7930 Data sheet ( Hoja de datos )
| Número de pieza | MT7930 | |
| Descripción | AC-DC LED Driver | |
| Fabricantes | Maxic Technology | |
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Maximizing IC Performance
MT7930
Single Stage, High PFC, AC-DC LED Driver
DESCRIPTION
MT7930 is a single-stage，primary side control
AC-DC LED driver with high power factor. With
MAXIC patent pending technology, the LED
current can be regulated accurately through
sensing the primary side information with few
external components without the need of an
opto-coupler.
MT7930 integrates power factor correction
function and works in DCM and constant OFF
time mode. A small harmonic current emission
(THD) is achieved.
MT7930 is also implemented with various
protections, such as over-current protection
(OCP), over-voltage protection (OVP),
short-circuit protection (SCP) and
over-temperature protection (OTP), etc, to
ensure a reliable system.
FEATURES
Wide input voltage range from AC85V to
AC265V
Highly accurate constant LED current
(+/-3%)
Up to 50W power drivability.
Primary-side current sensing and regulation
without an opto-coupler
Leading edge blanking (LEB) technique
Cycle-by-cycle current limiting
Under-voltage lockout (UVLO) protection
VDD and output over voltage protection
Adjustable constant current and output
power setting
Power on soft-start
Available in SOP8 package
APPLICATIONS
AC/DC LED driver applications
General purpose constant current source
Signal and decorative LED lighting
E14/E27/PAR30/PAR38/GU10 LED lamp
Typical Application Circuit
MT7930 Rev. 1.30
www.maxictech.com
Copyright © 2011 Maxic Technology Corporation
Page 1
1 page  
Maximizing IC Performance
MT7930
Single Stage, High PFC, AC-DC LED Driver
waveform information, as the auxiliary winding
voltage is proportional to the output voltage
(secondary winding voltage) during the OFF time
period. The auxiliary winding voltage is sampled
by DSEN pin, one LEB (Leading Edge Blanking)
time right after DRV signal is turned off.
Fig.1 Start up sequence
DRV
Power Factor Correction
The primary side current increases linearly from
zero to peak value, as sensed by the current
sensing pin CS, during the external MOSFET
on-time. When the primary current reaches the
threshold, MT7930 turns off the power MOSFET
immediately. After a constant OFF time, TOFF,
MT7930 turns on the power MOSFET again. The
peak current threshold is regulated by MAXIC
proprietary technique and follows the rectified
sinusoidal-shape of main line voltage. As a result,
the envelope of the inductor current is
sinusoidal-shaped, high power factor is therefore
achieved in this way.
Fig.2 Power Factor Correctioin
Auxiliary Sensing
MT7930 features over-voltage protection (OVP),
short-circuit protection (SCP), and over-current
protection (OCP) functions. Those protections
are triggered by sensing the auxiliary winding
Aux
LEB time
Fig.3 Auxiliary Signal Sensing
Over-voltage Protection
MT7930 is implemented with two over-voltage
protection schemes: (1) If DSEN pin’s voltage is
detected above 3.2V for three times (refer to
Auxiliary Sensing section), MT7930 turns off
the PWM switching signal, and VDD voltage
gradually drops to UVLO threshold, and the
system will be re-started. The threshold voltage
of over-voltage protection VOUT_OV, can be easily
defined as (refer to the application circuit in page
1):
VOUT_OV
3.2 (1
R5)
R6
Ns
Na
VD8
Where Ns is the secondary winding, Na is
auxiliary winding, VD8 is the forward bias of the
secondary side rectifier diode.
(2) If VDD pin’s voltage exceeds 19.2V three
times, MT7930 turns off the PWM switching
signal, and VDD gradually drops to UVLO
MT7930 Rev. 1.30
www.maxictech.com
Copyright © 2011 Maxic Technology Corporation
Page 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MT7930.PDF ] | |
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