BW6562A Datasheet, PDF (11/15 Pages) Bruckewell Technology LTD – High PFC LED Driver

BW6562A High PFC LED Driver
Example Applications
Single Stage LED Driver with PFC
One of major applications of the BW6562A is to provide a
single stage power module with high PF for LED lighting.
The following circuit, Figure 4, shows a simplified fly-back
AC-DC converter with both constant current (CC) and
constant voltage (CV) feedback from output side, to
prevent overload and also provide an over-voltage
protection facility.
This solution uses an isolated feedback with an opto-
coupler and the SQ7103 (+2.5V voltage reference and
dual Op-Amps), each one for voltage and current
regulation respectively. As LED lighting application, the
BW6562A offers the following advantages that make this
solution an appropriate method against the traditionally
PWM controller, where a good PF value is required :
●The input capacitance can be reduced to replace bulky
and expensive high voltage electrolytic capacitor (as
required by regular offline SMPS) by a small size,
cheaper film capacitor
●Transition-mode ensures low turn-on losses in MOSFET
and higher efficiency can be achieved.
●Lower parts count means lower material cost as well as
lower assembly cost for limited space.
Few details information about this, please refer separate
Application Note for details.
High PF Battery Charger
The single stage PFC can also be adopted as battery
charger. Figure 5 presents an off-line universal mains
battery charger that can drive up to 30W.
This solution also uses an isolated feedback with an opto-
coupler and the BW7103. To use the BW6562A IC in a
lead-acid battery charger circuit with high PFC, the DC
output voltage and the maximum permissible DC output
charging current needs to be decided on the basis of the
specific battery to be charged. For the lead-acid batteries
of different nominal voltages, the fixed constant-voltage,
current limited, charging mode, the typical voltage level
suggested by most lead-acid battery manufactures are as
follows :
© 2012 Bruckewell Technology Corp., Ltd.
11
Nominal
6V
12 V
24 V
48 V
Suggested
Charging
Voltage
6.9 V
13.8 V
27.6 V
55.2 V
Battery
Discharged
5.25 V
10.50 V
21.00 V
42.00 V
The maximum lead-acid battery charging current is
decided by the battery amp-hour capacity, represented
as 'C'. The lead-acid battery manufacturers in general
prefer a low battery charging current set at “C/20” Amp
for slow-charging, for improved life of the battery.
However, in case of ‘fast-charging’ and if permitted by
the battery manufacturer, the maximum battery charging
current can be set at “C/10” Amp. A charge-depleted
battery will initially draw the maximum charging current.
As the battery gradually gets charged, the charging
current will gradually reduce.
The maximum “Current Limit” therefore helps avoid a
battery getting over-heated during charging and thus
avoid damage to the battery. It is advisable to avoid
deep discharge of the lead-acid battery, to increase the
usable battery life. The secondary side feedback
network for the required CV-CC characteristics will
therefore be tailored accordingly in the application
circuit. The advanced battery chargers take into account
the battery temperature while charging the battery and
include appropriate compensation for the same, which is
not in the scope of this document.
PFC Pre-Regulator
Major application of the BW6562A is to implement a
wide-range mains input PFC pre-regulator, which will be
acting the input stage for the cascaded isolation DC-DC
converter, and can deliver above 350W in general.
Typical application circuit diagram is showed on page 1.
There are two methods; in general, to design pre-
regulator stage, one is with fixed frequency while the
other is with fixed on time.
The BW6562A can be implemented by fixed on time due
to its simplicity and less expensive, while the fixed
frequency technique is more complicated and beyond
the scope of this application note. In fixed on time mode,
the BW6562A is also working in transition mode where
the inductor current will be turn on when zero crossing is
detected. By using boost switching techniques, a PFC is
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