HV9919DB1 Supertex, HV9919DB1 Datasheet - Page 3

• Manufacturer Part Number: HV9919DB1
• Description: LED Lighting Development Kits SINGLE HI CURR LED DRIVER DEMOBOARD
• Manufacturer: Supertex

The design exercise of an HV9931 LED driver revolves
around establishing component values for (1) the input and
output stage inductors, (2) a value for the bus capacitor, and
(3) a value for switching cycle OFF time, which together
result in (1) acceptable current ripple at the output stage
(say 30%), (2) an acceptable bus voltage ripple (say 5%),
and (3) an input stage which maintains DCM operation over
the desired line and load voltage range.
For a given HV9931 design, the bus voltage rises and falls
with like changes in line and load voltage. This is unlike a
two stage design having two transistors and control ICs,
where the bus voltage can be set independent of line and
load voltage variation. If the desired ranges of line and load
voltage are particularly large then the latter topology may be
preferable so as to avoid large variation in bus voltage.
The design of an HV9931 based LED driver is not further
discussed here, except for noting that a semi-automatic
design tool is available in Mathcad form, based on behavioral
Simplified Schematic Diagram
Note on Inductors:
This board was fitted with standard (COTS) inductors. These
are not necessarily an optimal choice but present an expedi-
ent way to go when evaluating a design. Custom engineered
parts generally give better performance, particularly with re-
spect to efficiency.
Drum core style inductors, whether in radial or axial leaded
versions, are popular for their ready availability and low cost.
Drum core styles have particularly simple construction and
AC2
AC1
BZX84C43
Supertex inc.
250mA
F11
Overvoltage Protection
10kΩ
ROV
ZOV
Optional Output
C11
47nF
2.2mH
L11
C
A
C12
47nF
THROV
BT168GW
1
2
4
3
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
BR11
RH06-T
2.2mH
L21
2.43kΩ
270mΩ
75kΩ
C21
47nF
R61
R62
R68
1.2mH
L31
2
3
CS1
STTH108A
6.8kΩ
simulation, which, allows components to be adjusted in an
iterative manner, starting from an initial guess. The tool allows
quick evaluation of nine standard test cases, exercising the
design over line voltage variation and tolerance variation of
three component parameters.
Mathcad design data can be found at the end of this
document. The data tends to be in good agreement with the
actual demo board despite the omission of switching losses
in the model. For this design we can see that the calculated
efficiency is off by say 5 percent likely due underestimation
of switching losses and inductor core and winding losses.
A Simplified Version of the Design
The demo board can be simplified significantly. Below is a
schematic showing the essential elements of the driver.
Contact Supertex Applications Engineering for guidance in
simplifying the design or for adding functions such as triac
dimmability.
STTH108A
can be wound for lowest cost without coil former (bobbin).
They may serve well during the development stage, but may
not be the best choice for final design. Keep these type of
inductors away form any metallic surface such as heatsinks,
PCB copper planes, metallic enclosures, and capacitors, as
these unshielded parts can create high eddy current losses
in these parts. For tightly packaged designs or where induc-
tor losses are an issue, drum core style inductors are not
recommended.
R37
D32
D31
100pF
GND
C37
VIN
1
3
●
HV9931LG
Tel: [phone]
M31
SPA02N80C3
GATE
22μF
4
+
IC51
VDD
E31
6
205kΩ
C51
10µF
R51
STTH1R06A
PWM
RT
D41
5
8
●
www.supertex.com
CS2
D42
STTH1R06A
2.67kΩ
HV9931DB2v1
R72
7
3.9mH
L41
R73
75kΩ
C
A
R71
680mΩ
CAT
ANO