U.S. patent application number 14/046459 was filed with the patent office on 2015-01-22 for using an led die to measure temperature inside silicone that encapsulates an led array.
This patent application is currently assigned to Bridgelux, Inc.. The applicant listed for this patent is Bridgelux, Inc.. Invention is credited to Michael Neal Gershowitz, Babak Imangholi, R. Scott West.
Application Number | 20150021629 14/046459 |
Document ID | / |
Family ID | 52342860 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150021629 |
Kind Code |
A1 |
Gershowitz; Michael Neal ;
et al. |
January 22, 2015 |
Using An LED Die To Measure Temperature Inside Silicone That
Encapsulates An LED Array
Abstract
An LAM/ICM assembly comprises an integrated control module (ICM)
and an LED array member (LAM). The ICM includes interconnect
through which power from outside the assembly is received. In a
first novel aspect, active circuitry is embedded in the ICM. In one
example, the circuitry monitors LED operation, controls and
supplies power to the LEDs, and communicates information into and
out of the assembly. In a second novel aspect, a lighting system
comprises an AC-to-DC converter and a LAM/ICM assembly. The
AC-to-DC converter outputs a substantially constant current or
voltage. The magnitude of the current or voltage is adjusted by a
signal output from the LAM/ICM. In a third novel aspect, the ICM
includes a switching DC-to-DC converter. An AC-to-DC power supply
supplies a roughly regulated supply voltage. The switching
converter within the LAM/ICM receives the roughly regulated voltage
and supplies a regulated LED drive current to its LEDs.
Inventors: |
Gershowitz; Michael Neal;
(San Jose, CA) ; West; R. Scott; (Pleasanton,
CA) ; Imangholi; Babak; (Livermore, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bridgelux, Inc. |
Livermore |
CA |
US |
|
|
Assignee: |
Bridgelux, Inc.
Livermore
CA
|
Family ID: |
52342860 |
Appl. No.: |
14/046459 |
Filed: |
October 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61856552 |
Jul 19, 2013 |
|
|
|
Current U.S.
Class: |
257/88 |
Current CPC
Class: |
H01L 25/167 20130101;
H05B 45/48 20200101; H01L 2224/48137 20130101; H05B 47/19 20200101;
H05K 2201/10106 20130101; H01L 2924/181 20130101; F21V 23/02
20130101; H05B 45/10 20200101; H05B 45/50 20200101; H05K 1/142
20130101; F21K 9/20 20160801; F21Y 2105/10 20160801; F21V 23/006
20130101; H01L 2924/181 20130101; H05B 45/00 20200101; H01L
2924/00012 20130101; H01L 2924/00014 20130101; H01L 33/507
20130101; H05B 45/37 20200101; H05B 45/44 20200101; H01L 2224/73265
20130101; H05K 3/0061 20130101; H05B 45/46 20200101; H01L
2224/48091 20130101; H01L 33/54 20130101; H01L 25/0753 20130101;
F21V 29/70 20150115; H01L 33/62 20130101; F21Y 2115/10 20160801;
H01L 2224/48091 20130101; H01L 33/486 20130101 |
Class at
Publication: |
257/88 |
International
Class: |
H01L 25/16 20060101
H01L025/16 |
Claims
1. An assembly comprising: an integrated control module (ICM) that
defines a central opening, wherein the central opening has a
substantially circular upper peripheral edge and a substantially
rectangular lower peripheral edge, wherein the substantially
circular upper peripheral edge has smaller periphery than the
substantially rectangular lower peripheral edge, wherein the ICM
comprises at least one active electronic component; and an LED
(Light Emitting Diode) array member (LAM) comprising a substrate
member, a plurality of LED dice disposed on the substrate member,
and an amount of luminescent material disposed over the LED dice,
wherein the substrate member includes an interconnect layer and a
plurality of LAM contact pads, wherein the LAM contact pads are
disposed on an upper surface of the LAM, wherein the LAM fits up
into the central opening in the ICM and is attached to the ICM, and
wherein the LED dice are controlled by the active electronic
component.
2. The assembly of claim 1, wherein the substrate member of the LAM
has a rectangular upper peripheral edge that is substantially the
same size as the rectangular lower peripheral edge of the central
opening of the ICM.
3. The assembly of claim 1, wherein the ICM includes a multi-layer
printed circuit board, and wherein the active electronic component
is mounted to the multi-layer printed circuit board.
4. The assembly of claim 1, wherein the ICM includes an
interconnect layer of patterned sheet metal, and wherein the active
electronic component is mounted to the patterned sheet metal.
5. The assembly of claim 1, wherein the ICM includes an
interconnect layer of a flexible printed circuit, and wherein the
active electronic component is mounted to the flexible printed
circuit.
6. The assembly of claim 1, wherein the ICM comprises an amount of
encapsulant that forms an upper surface of the ICM, and wherein the
amount of encapsulant also contacts and covers the active
electronic component.
7. The assembly of claim 1, wherein the ICM has an upper surface,
and wherein the upper surface has a substantially circular outer
peripheral edge.
8. The assembly of claim 1, wherein the ICM defines at least two
cylindrical openings, wherein the two cylindrical openings are
located outside the central opening on opposite sides of the
central opening, and wherein each of the cylindrical openings
extends from a bottom surface of the ICM to an upper surface of the
ICM.
9. The assembly of claim 1, wherein the active electronic component
is a microcontroller.
10. The assembly of claim 1, wherein the active electronic
component includes an amount of digital logic.
11. The assembly of claim 1, wherein the active electronic
component is a part of an RF (Radio Frequency) transmitter.
12. The assembly of claim 1, wherein the active electronic
component is disposed within an electronic package, and wherein a
part of the electronic package forms a part of a bottom surface of
the ICM.
13. The assembly of claim 1, wherein the ICM comprises a first
power terminal and a second power terminal, wherein a current flows
into the assembly through the first power terminal and flows out of
the ICM through the second power terminal.
14. The assembly of claim 13, wherein the ICM further comprises a
third terminal, wherein a digital signal is communicated out of the
ICM through the third terminal.
15. The assembly of claim 1, wherein power is supplied to the LED
dice through the active electronic component.
16. An integrated control module (ICM) comprising: an insulative
substantially circular upper layer of a molded encapsulant
material; an insulative substantially circular lower layer of the
molded encapsulant material, wherein the upper layer of encapsulant
material and the lower layer of encapsulant material are formed
such that the ICM defines a central opening, wherein the central
opening has a substantially circular upper peripheral edge at an
upper surface of the upper layer of the encapsulant material and
has a substantially rectangular lower peripheral edge at a lower
surface of the lower layer of the encapsulant material; a first
power terminal disposed on an upper surface of the ICM; a second
power terminal disposed on the upper surface of the ICM; and LED
(Light Emitting Diode) control circuitry that is at least in part
encapsulated by the molded encapsulant material, wherein the ICM
comprises no LED, and wherein the LED control circuitry is coupled
to be powered via the first and second power terminals.
17. The ICM of claim 16, further comprising: a third terminal
through which digital signals are communicated out of the ICM.
18-20. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.119
from U.S. Provisional Application No. 61/856,552, entitled "LED
Array Member and Integrated Control Module Assembly," filed on Jul.
19, 2013, the subject matter of which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates generally to packaging of
light-emitting diodes.
BACKGROUND INFORMATION
[0003] A light emitting diode (LED) is a solid state device that
converts electrical energy to light. Light is emitted from active
layers of semiconductor material sandwiched between oppositely
doped layers when a voltage is applied across the doped layers. In
order to use an LED chip, the chip is typically enclosed along with
other LED chips in a package. In one example, the packaged device
is referred to as an LED array. The LED array includes an array of
LED chips mounted onto a heat conducting substrate. A layer of
silicone in which phosphor particles is embedded is typically
disposed over the LED chips. Electrical contact pads are provided
for supplying current into the LED array and through the LED chips
so that the LED chips can be made to emit light. Light emitted from
the LED chips is absorbed by the phosphor particles, and is
re-emitted by the phosphor particles so that the re-emitted light
has a wider band of wavelengths. Making a light fixture or a
"luminaire" out of such an LED array, however, typically involves
other components. The LED array generates heat when used. If the
temperature of the LED array is allowed to get too high,
performance of the LED array may suffer and the LED array may
actually fail. In order to remove enough heat from the LED array so
as to keep the LED array adequately cool, the LED array is
typically fixed in some way to a heat sink. In addition, power must
somehow be supplied to the LED array. Power supply circuitry is
typically required to supply current to the LED array in a desired
and suitable fashion. Optical components are also generally
employed to direct and focus the emitted light in a desired
fashion. There are many considerations involved in packaging an LED
array so that it the array can be used effectively in an overall
luminaire. Ways of packaging LED arrays for use in luminaires are
sought.
SUMMARY
[0004] An LAM/ICM assembly comprises an integrated control module
(ICM) and an LED array member (LAM). In one example, the ICM is a
thick, washer-shaped, molded plastic member that fits over an upper
surface of the LAM and holds the LAM so that a bottom surface of
the LAM is held in good thermal contact against a heat sink. The
ICM has holes through which threaded screws or bolts can extend.
The screws or bolts extend through the holes in the ICM and engage
corresponding threaded holes in the heat sink, thereby pulling the
washer-shaped ICM toward the heat sink. The ICM in turn presses
downward on the top of the LAM and causes the bottom surface of the
LAM to be pressed against the heat sink.
[0005] In addition, the ICM includes terminals and an interconnect
layer through which power from outside the assembly is received
onto the assembly and is supplied through the ICM, and through
mating sets of contact pads of the ICM and LAM, and to the LAM so
that the LEDs of the LAM can be powered and emit light. The ICM
does not cover the LEDs of the LAM, but rather a central circular
opening in the washer-shaped ICM allows light emitted from the LEDs
to pass upward through the central opening and away from the heat
sink.
[0006] In accordance with a first novel aspect, the washer-shaped
ICM includes circuitry involving active electronic components. The
circuitry monitors LAM operation, controls and supplies power to
the LAM, and communicates information into and out of the assembly.
In one example, the circuitry monitors the voltage disposed across
a string of LEDs of the LAM, monitors the current flowing through
the string of LEDs of the LAM, and monitors the temperature of the
LED array. In one example, the ICM includes a printed circuit board
to which this circuitry is mounted. The circuitry and the printed
circuit board are encapsulated in injection molded plastic.
Injection molded plastic overmolds almost all of the printed
circuit board including the periphery of the printed circuit board,
the upper surface of the printed circuit board, and the lower
surface of the printed circuit board. There are, however, exposed
contacts on the bottom of the printed circuit board that extend
around in the bottom of the inside lip of the central opening in
the ICM. When the LAM is fitted up into place into the central
opening in the ICM, LAM contact pads on the peripheral edge of
upper surface of the LAM make electrical contact with corresponding
ICM contact pads on the bottom of the inside lip of the ICM. Power
is supplied through the ICM and to the LAM through these contacts,
and LAM operation is monitored by the ICM through these
contacts.
[0007] In accordance with a second novel aspect, a lighting system
comprises an AC-to-DC converter and a LAM/ICM assembly, where the
LAM/ICM supplies a control signal back to the AC-to-DC converter.
The AC-to-DC converter receives a supply voltage from an AC voltage
source such as a 110 VAC voltage source. The AC-to-DC converter
outputs a substantially constant and regulated current or voltage,
where the substantially constant current or voltage has an
adjustable magnitude. The level to which the current or voltage is
regulated can be changed by appropriate control of the control
signal (for example, a zero volts to ten-volt control input signal)
to the AC-to-DC converter. If the ICM determines that more power
should be received, then the ICM increases the level of the zero to
ten volt control signal. If the ICM determines the less power
should be received, then the ICM decreases the level of the zero to
ten volt control signal. The AC-to-DC converter responds by
increasing or decreasing the current or voltage level to which it
regulates, as instructed by the control signal.
[0008] In the case where the adjustable AC-to-DC converter outputs
a regulated constant current, a FET of the LAM/ICM assembly simply
turns on or off current flow through the LAM. If LAM current flow
is on, then the magnitude of the current flowing from the AC-to-DC
converter is determined by the feedback zero volts to ten-volt
control signal that the LAM/ICM supplies back to the AC-to-DC
converter. Since the AC-to-DC converter output cannot normally be
turned fully off by the zero to 10 volt control signal, and because
the circuitry of the ICM requires a supply voltage at all times to
operate, the ICM includes a semiconductor switch that is operable
in the saturated mode as an "on-off" switch to the LAM. The ICM
also includes circuitry that controls the semiconductor switch so
that when it is desired to have the LAM produce no light
whatsoever, the switch is turned "off" interrupting all current
flow to the LAM, but leaving voltage output from the AC-to-DC
converter at the ICM which can be used to continue to power the
circuitry of the ICM while the LAM is "off".
[0009] In the case where the adjustable AC-to-DC converter outputs
a regulated constant voltage, the ICM of the LAM/ICM assembly
receives power from the AC-to-DC converter and supplies power the
LEDs of the LAM. The ICM includes a semiconductor switch that is
operable in the linear mode. The ICM also includes circuitry that
controls the semiconductor switch in the linear mode such that the
ICM receives the substantially constant voltage from the AC-to-DC
converter and causes a controlled DC current to flow through the
LAM. Linear operation of the semiconductor switch is controlled to
fine tune the magnitude of the DC current flowing through the LEDs.
The circuitry also outputs a control signal that is supplied out of
the LAM/ICM assembly and back to the AC-to-DC converter. This
control signal is the zero-volt to ten-volt control input signal
that controls the AC-to-DC converter. Using this control signal,
the circuitry of the LAM/ICM assembly controls the AC-to-DC
converter so that the LED voltage at which the LEDs of the LAM are
driven is close to (for example, within ten percent of) the voltage
at which the constant current is supplied by the AC-to-DC converter
to the LAM/ICM assembly. Because the voltages are close, power
dissipation of the semiconductor switch in the ICM is low enough
that it can perform its regulating function without overheating. In
one example, the semiconductor switch is disposed in a
semiconductor package, where the semiconductor package of the
switch extends from a bottom surface of the ICM and is a good
thermal contact with the heat sink.
[0010] In accordance with a third novel aspect, a lighting system
comprises an AC-to-DC converter and a LAM/ICM assembly. The
AC-to-DC converter receives a supply voltage from an AC voltage
source such as a 110 VAC voltage source. The AC-to-DC converter in
the third novel aspect outputs a substantially constant voltage.
The ICM of the LAM/ICM assembly includes a switching DC-to-DC
converter. The switching DC-to-DC converter of the ICM receives the
substantially constant DC voltage from the AC-to-DC converter and
supplies a substantially constant and regulated LED DC drive
current to the LAM.
[0011] The switching DC-to-DC converter that is embedded in the ICM
may be a step down converter whose input voltage is higher than its
output voltage, or the switching DC-to-DC converter that is
embedded in ICM may be a step up converter whose input voltage is
lower than its output voltage, or the switching DC-to-DC converter
that is embedded in the ICM may be a combination converter whose
incoming input voltage can be higher or lower than the converter
output voltage. In one specific example, the switching DC-to-DC
converter of the ICM is a step-down buck converter that is switched
at about 10 MHz. In other examples, the switching DC-to-DC
converter of the ICM is one of a step-up boost converter, a SEPIC
converter, and a boost/buck combination converter operating at
switching frequencies that may be substantially higher than 10 MHz
to keep the physical size of electronic components small.
[0012] In one example, the LAM includes a plurality of strings of
LEDs. The ICM includes a plurality of buck converters, where all
the buck converters are controlled by a common microcontroller that
is a part of the ICM. Each string of LEDs is supplied with an
independently controlled LED drive current by a corresponding one
of the plurality of buck converters. In some embodiments, multiple
such LAM/ICM assemblies are driven in parallel by the same AC-to-DC
converter, where the AC-to-DC converter outputs only a roughly
regulated constant voltage. Within each LAM/ICM, the
microcontroller monitors the voltage supplied to each LED string,
monitors the current flowing through each LED string, and monitors
the temperature of the LED array. The microcontroller controls the
current supplied to each string independently of the currents
supplied to the other strings. The microcontroller may control the
current supplied to each string of LEDs by controlling the
switching DC-to-DC converter or converters of the ICM that supply
the drive currents to the strings of LEDs. In some examples, the
ICM includes an RF (Radio Frequency) transceiver that the
microcontroller uses to communicate information to and from other
RF transceivers located outside the LAM/ICM assembly. The ICM also
includes a terminal through which the microcontroller can
communicate digital information into and out of the LAM/ICM
assembly. The communication interface can be a wired one through
this terminal, or the communication interface can be a wireless one
provided by the RF communication link.
[0013] Further details and embodiments and techniques are described
in the detailed description below. This summary does not purport to
define the invention. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, where like numerals indicate like
components, illustrate embodiments of the invention.
[0015] FIG. 1 is a perspective view of the connector side of the
top of an LED array member (LAM)/integrated control module (ICM)
assembly.
[0016] FIG. 2 is a perspective view of the top of an LED array
member (LAM)/integrated control module (ICM) assembly from the side
opposite the connector.
[0017] FIG. 3 is a perspective view of the bottom of the LAM/ICM of
FIGS. 1 and 2.
[0018] FIG. 4 is a cross-sectional, top-down view of the LAM/ICM
assembly of FIGS. 1 and 2.
[0019] FIG. 5 is top-down view of one example of a LAM usable with
the ICM of FIGS. 1 and 2.
[0020] FIG. 6 is cross-sectional view showing how the LAM fits up
and into the central opening in the ICM.
[0021] FIG. 7 is a diagram showing one example of an ICM contact
pad disposed on the inside lip of the ICM.
[0022] FIG. 8 is a more detailed diagram showing how a LAM contact
pad on the peripheral edge of upper surface of the LAM makes
contact with a corresponding ICM contact pad in the bottom of the
inside lip of the ICM.
[0023] FIG. 9 is a cross-sectional view taken along line A-A' of
the LAM/ICM of FIG. 4.
[0024] FIG. 10 is a cross-sectional view taken along line B-B' of
the LAM/ICM of FIG. 4.
[0025] FIG. 11 is a cross-sectional view taken along line C-C' of
the LAM/ICM of FIG. 4.
[0026] FIG. 12 is a cross-sectional view taken along line D-D' of
the LAM/ICM of FIG. 4.
[0027] FIG. 13 is a circuit diagram of the LAM/ICM assembly in
accordance with a second novel aspect, in an example in which the
AC-to-DC converter outputs a regulated constant current and the
AC-to-DC converter receives a control signal back from the LAM/ICM
assembly.
[0028] FIG. 14 is a diagram of a lighting system that includes the
LAM/ICM assembly of FIG. 13.
[0029] FIG. 15 is a circuit diagram of the LAM/ICM assembly in
accordance with the second novel aspect, in an example in which the
AC-to-DC converter outputs a regulated constant voltage.
[0030] FIG. 16 is a top-down diagram of another example of a LAM
that can be used with the ICM of FIGS. 1 and 2.
[0031] FIG. 17 is a circuit diagram of the LAM/ICM assembly in
accordance with a third novel aspect.
[0032] FIG. 18 is a circuit diagram of a buck converter suitable
for use in the LAM/ICM assembly of FIG. 17.
[0033] FIG. 19 is a table that sets forth parameters and components
characteristics of the buck converter of FIG. 18.
[0034] FIG. 20 is a diagram illustrating a first way to drive
multiple LED strings with multiple buck converters, where the
multiple buck converters are parts of the ICM.
[0035] FIG. 21 is a diagram illustrating a second way to drive
multiple LED strings with multiple buck converters, where the
multiple buck converters are parts of the ICM.
[0036] FIG. 22 is a diagram of a lighting system that includes the
LAM/ICM assembly of FIG. 17.
DETAILED DESCRIPTION
[0037] Reference will now be made in detail to background examples
and some embodiments of the invention, examples of which are
illustrated in the accompanying drawings.
[0038] FIG. 1 is a perspective view of the top of an LED assembly
member/integrated control module assembly (LAM/ICM assembly) 1.
There are two parts of the LAM/ICM assembly: a LED assembly member
2 (FIG. 3) and an integrated control module 3. The LED assembly
member 2 is hereinafter referred to as the LAM. The integrated
control module 3 is hereinafter referred to as the ICM. As
illustrated in the diagram, the LAM/ICM assembly 1 is a disk-shaped
structure that has a circular upper outer peripheral edge 4.
Reference numeral 5 identifies the upper surface of the LAM/ICM
assembly 1. The upper surface 5 is a surface of a molded plastic
encapsulant 40 (FIG. 6). Two sets of two holes 6-9 are provided
through which threaded screws or bolts (not shown) can extend to
fix the LAM/ICM assembly 1 to a heat sink. The disk-shaped shaded
object in the center in the illustration is a disk-shaped amount of
silicone 11. The silicone 11 has phosphor particles embedded in it.
This silicone with the embedded phosphor particles overlies an
array of light emitting diodes (LEDs). The LEDs are not seen in the
diagram because they are disposed under the silicone. The LAM/ICM
assembly 1 further includes a header socket 12 and ten header pins,
such as pins 13, 14, 15 and 16. Pin 13 is a power terminal through
which a supply voltage or a supply current is received into the
LAM/ICM assembly 1. Pin 14 is a power terminal through which the
current returns and passes out of the LAM/ICM assembly. Pin 14 is a
ground terminal with respect to the power terminal 13. Pin 15 is a
data signal terminal through which digital signals are communicated
into and/or out of the LAM/ICM assembly. Pin 16 is a signal ground
for the data signals communicated on pin 15. The illustrated
example of the LAM/ICM assembly that has ten header pins is but one
example. In other examples, fewer or more header pins are provided
in the header socket 12, and assignment of power or signals to the
pins can be on different positions than illustrated herein. If the
LEDs underneath silicone 11 are powered and emitting light, then
the light passes upward through the central circular opening 17 in
upper surface 5, and is transmitted upward and away from the
LAM/ICM assembly 1.
[0039] FIG. 2 is a perspective view of the top of the LAM/ICM
assembly, taken from the other side of the LAM/ICM assembly
opposite header socket 12.
[0040] FIG. 3 is a perspective view of the bottom of the LAM/ICM
assembly 1. Reference numeral 18 identifies the circular lower
outer peripheral edge of the LAM ICM assembly. Whereas the shape of
central opening 17 at the upper surface 5 of the ICM is circular as
pictured in FIG. 1, the shape of the central opening 17 at the
bottom surface 19 of the ICM as pictured in FIG. 3 is square. The
LAM 2 is disposed in the central opening 17 so that the bottom
surface 20 of the LAM 2 protrudes just slightly from the plane of
the bottom surface 19 of the ICM 3. From the perspective of the
illustration of FIG. 3, the bottom surface 20 of the LAM is
slightly higher than is the bottom surface 19 of the ICM. The
bottom surface 20 of the LAM is actually the bottom surface of a
substrate member 57 of the LAM (FIG. 6).
[0041] FIG. 4 is a cross-sectional, top-down diagram of the LAM/ICM
assembly 1. The round circle identified by reference numeral 17A is
the edge of circular central opening 17 at the upper surface of the
ICM. The dashed square identified by reference numeral 17B is the
edge of the square-shaped central opening 17 at the bottom surface
of the ICM. The four dashed squares 21-24 identify where four LED
dice are disposed underneath the silicone 11.
[0042] FIG. 5 is a simplified top-down diagram of one example of
LAM 2, where the silicone and solder mask layers are not shown so
that the metallization patterns of die attachment of LED dice 21-24
can be seen. There are five areas of metal 25-29 disposed on an
insulative layer 30, where the insulative layer 30 in turn is
disposed on the substrate member 57. The insulative layer 30
insulates each of the metal areas from the substrate member 57 of
the LAM. The substrate member 57 in this case is a square piece of
aluminum sheet. The four LED dice 21-24 are lateral LED dice that
are die-attached to the central metal area 29. The LED dice are
wire bonded to form two parallel strings. An LED drive current can
flow through the first string by flowing from metal area 25,
through LED die 21, through LED die 23, and to metal area 28. An
LED drive current can flow through the second string by flowing
from metal area 25, through LED die 22, through LED die 24, and to
metal area 28. Reference numeral 31 identifies one of the bond
wires. In addition to LED dice 21-24, LAM 2 includes a temperature
sensing GaN diode die 32. In one example, this GaN diode die 32 is
of identical construction to the LED dice. In the illustrated
example, it is of identical construction except for the fact that
it is a smaller die. The anode of GaN diode 32 is coupled via a
bond wire to metal area 26. The cathode of GaN diode 32 is coupled
via another bond wire to metal area 27. The dashed line 33
identifies the circular outer periphery of a rim 34 that retains
the silicone 11. As can be seen from FIGS. 1, 2 and 4, this rim 34
is of a diameter that is just smaller than the inside diameter of
the central opening 17 in the upper surface of the ICM. The
outwardly extending portions of the metal areas at the corners of
the LAM of FIG. 5 are referred to as LAM contact pads because these
areas of metal are exposed, and are not covered with soldermask.
Reference numerals 35-38 identify these LAM contact pads in the
illustration of FIG. 5.
[0043] FIG. 6 is a cross-sectional diagram that shows how the LAM 2
fits up into the central opening 17 in the ICM 3. ICM 3 includes an
interconnect structure 39, a plurality of electronic components
that are mounted to the interconnect structure, and the amount of
insulative molded plastic encapsulant 40 that encases and
encapsulates the interconnect structure and the electronic
components. In the illustrated example, the interconnect structure
39 is a multi-layer printed circuit board (PCB). One of the
electronic components 41 of the circuitry is seen in cross-section
as a rectangle. Not all of the printed circuit board is actually
encapsulated, but rather the bottom of the inside lip 42 of the
central opening 17 is not covered with encapsulant so that portions
of metallization on this lip 42 can serve as ICM contact pads. Each
of the LAM contact pads on the top of the LAM 2 is soldered to
corresponding one of the ICM contact pads on the downward facing
inside lip 42 of the ICM. In this example, amounts 43 and 44 of
solder paste are disposed on the LAM contact pads, and the LAM 2 is
moved up and into contact with the ICM 3, and then the assembly is
heated in a reflow soldering process to solder the LAM contact pads
to the ICM contact pads. Other soldering and mechanical/electrical
interface methods such as conductive adhesives could be used
instead of reflow soldering with solder paste as described
herein.
[0044] FIG. 7 is a view of the bottom of the ICM 3. Metal traces of
the printed circuit board 39 extend to the inside lip 42 and
connect to ICM contact pads through conductive vias. For example,
trace 45 contacts ICM contact pad 46 through conductive via 47.
Trace 48 contacts ICM contact pad 49 through conductive via 50.
[0045] FIG. 8 is a view that shows how LAM contact pad 36 is
coupled via solder 44 to the corresponding ICM contact pad 46 on
the inside lip of the ICM. The PCB 39 includes three metal layers
51, 52 and 53 and three fiberglass layers 54, 55 and 56. The
substrate member 57 of the LAM 2 is covered by insulative layer 30.
Electrical contact is made from metal area 26, a part of which is
LAM contact pad 36, up through solder 44, to ICM contact pad 46,
and through a conductive via in the PCB, and to metal interconnect
layer 51 of the PCB 39. The interconnect structure described herein
is that of a conventional FR-4 PCB; however, other structures such
as Kapton "flex circuit" or metal clad PCB circuits can also be
used for this interconnect structure.
[0046] FIG. 9 is a cross-sectional view of the LAM/ICM assembly 1
of FIG. 4 taken along sectional line A-A' (shown on a heat sink
60). Bolts 58 and 59 extend through holes 6-7, and hold the bottom
surface 20 of LAM 2 in good thermal contact with the heat sink 60
through a layer 61 of a thermal interface material (TIM). There are
no LAM contact pads or ICM contact pads in the cross-section
illustrated. Reference numerals 62 and 63 identify additional
electronic components of the circuitry mounted on PCB 39. The
circuitry is overmolded by the injection molded plastic encapsulant
40.
[0047] FIG. 10 is a cross-sectional view of the LAM/ICM assembly 1
of FIG. 4 taken along sectional line B-B' (shown on a heat sink).
Solder 43 couples LAM contact pad 37 to ICM contact pad 64. Solder
44 couples LAM contact pad 36 to ICM contact pad 46.
[0048] FIG. 11 is a cross-sectional view of the LAM/ICM assembly 1
of FIG. 4 taken along sectional line C-C' (shown on heat sink 60).
Electronic components of the circuit as seen in cross-section
include a communication integrated circuit 65, a microcontroller
integrated circuit 66, and a FET switch 67. Each of these three
components is a packaged device that is in turn overmolded by the
plastic encapsulant 40 of the ICM. In the case of the FET switch
67, a surface of the package forms a part of the bottom surface of
the ICM so that when the ICM is pressed against the heat sink 60
(with the TIM 61 in between), the bottom surface of the FET switch
package makes good thermal contact with the heat sink 60. The FET
switch package may, for example, be a DCB-isolated SMPD (direct
copper bonded isolated surface mount power device) package whose
downward facing surface is a heat-dissipating substrate that is
intended to be pressed against a heat sink.
[0049] FIG. 12 is a cross-sectional view of the LAM/ICM assembly 1
of FIG. 4 taken along sectional line D-D' (shown on a heat
sink).
[0050] FIG. 13 is a diagram of the LAM/ICM assembly 1 in accordance
with a second novel aspect. The LAM/ICM assembly 1 is illustrated
with the heat sink 60 and with optics 68 denoted as blocks. The
microcontroller 66 monitors the temperature of the LAM 2 via a
temperature interface circuit 69. Temperature interface circuit 69
includes a constant current source that supplies a constant current
70 to the temperature sensing GaN die 32 via ICM contact pad 46,
LAM contact pad 36, LAM contact pad 38 and ICM contact pad 49. The
temperature interface circuit 69 also includes a voltage amplifier
that amplifies the sensed voltage across LAM contact pads 36 and 38
and supplies the resulting amplified voltage signal T 72 to the
microcontroller 66 via conductor 73. In addition, microcontroller
66 monitors the voltage V with which the LEDs of LAM 2 are driven.
This LED drive voltage is the voltage between LAM contact pads 35
and 37. A current and voltage measuring interface circuit 78
measures this voltage via conductors 79 and 80. In addition,
microcontroller 66 monitors the LED drive current 74 flowing
through the LEDs of the LAM 2. This current 74 flows from pin 13,
through ICM contact pad 75, through LAM contact pad 35, through the
LEDs, through LAM contact pad 37, through ICM contact pad 64,
through current sense resistor 77, through FET switch 67, out of
the LAM/ICM assembly via pin 14. The current and voltage measuring
interface circuit 78 detects the LED drive current 74 as the
voltage dropped across the current sense resistor 77. This voltage
is detected across conductors 80 and 81. The voltage and current
measuring interface circuit 78 receives the voltage sense and
current sense signals, low pass filters them, amplifies them, and
performs level shifting and scaling to generate a voltage sense
signal V 82 and a current sense signal I 83. The voltage and
current sense signals 82 and 83 are supplied to the microcontroller
66 via conductors 84 and 85, respectively.
[0051] The T signal 72, the V signal 82, and the I signal 83 are
converted into digital values by the analog-to-digital converter
(ADC) 86 of the microcontroller. A main control unit (MCU) 87 of
the microcontroller executes a program 71 of processor-executable
instructions. The I, V and T signals, as well as information
received from communication integrated circuit 65, are used by the
MCU 87 to determine how to control FET switch 67. In the present
example, the MCU 87 can control the FET switch to be nonconductive,
thereby turning off the LEDs. The MCU 87 can control the FET switch
to be fully conductive, thereby turning on the LEDs to a brightness
proportional to the current supplied by the AC-DC converter as
controlled by the zero to ten volt signal also produced by the MCU
as directed by the control program. As explained in further detail
below, the ICM 3 receives a substantially constant current via pins
13 and 14 from an AC-to-DC power supply circuit 88 (see FIG. 14).
The AC-to-DC power supply circuit 88 has a constant current output,
the magnitude of the constant current being controllable by a zero
to ten volt signal received by the AC-to-DC power supply circuit.
The voltage that results across pins 13 and 14 when this constant
current is being supplied to the LAM/ICM assembly 1 is about 50
volts. The microcontroller 66 controls the FET switch 67 to be
fully on with nearly zero voltage across it when the LAM is to be
illuminated. To accomplish control for a desired LED brightness
(desired amount of current flow through the LEDs of the LAM), the
microcontroller 66 sends a zero to ten voltage dimming control
signal 89 back to the AC-to-DC power supply circuit 88 via
conductor 90, and data terminal 15. The microcontroller 66 uses
this control signal 89 to increase and to decrease the magnitude of
the constant current 74 being output by the AC-to-DC power supply
circuit 88. The circuit components 69, 78, 66 and 65 are powered
from a low DC supply voltage such as 3 volts DC. A component
voltage supply circuit 91 generates this 3 volt supply voltage from
the 50 volts across pins 13 and 14. The 3 volt supply voltage is
supplied onto voltage supply conductor 90. Conductor 93 is the
ground reference conductor for the component supply voltage.
Because only a small amount of power is required to power the
circuitry embedded in the ICM, the component voltage supply circuit
91 may be a simple linear voltage regulator.
[0052] FIG. 14 is a system level diagram of a lighting system 94.
Lighting system 94 includes the power supply circuit 88, the
LAM/ICM assembly 1, and internet connectivity circuitry 95. The
LEDs of the LAM can be monitored and controlled remotely by
communicating across the internet 96. Information can be
communicated from the internet 96, across an ethernet connection
97, through the internet connectivity circuitry 95, from antenna 98
of the internet connectivity circuitry 95 to the antenna 98 of the
LAM/ICM assembly 1 in the form of an RF transmission, through
transceiver 163 of the communication integrated circuit 65, and to
the MCU 87 of the microcontroller 66. Information can also be
communicated in the opposite direction from the MCU 87 of the
microcontroller 66, through the transceiver 163 of the
communication integrated circuit 65, from antenna 99 in the form of
an RF transmission to antenna 98, through the internet connectivity
circuitry 95, across ethernet connection 97, to the internet 96.
The lighting system 94 is typically part of a luminaire (light
fixture) that is powered by ordinary 110 VAC wall power. Symbol 100
represents a source of 110 VAC wall power for the luminaire.
[0053] FIG. 14 shows that if the AC-to-DC supply is a constant
voltage supply, the MCU 87 can control the FET switch to operate in
the FET's linear mode in order to control the magnitude of the
constant current 74 supplied to the LEDs of the LAM, thereby
adjusting the brightness of the LEDs. When operating in this linear
mode way, the voltage drop across the FET switch should be about
two volts. As explained in further detail below, the ICM 3 receives
a substantially constant voltage via pins 13 and from an AC-to-DC
power supply circuit that has a constant voltage output, the
magnitude of the constant voltage being controllable by a zero to
ten volt signal received by the AC-to-DC power supply circuit. The
voltage that results across pins 13 and 14 when this constant
current is being supplied to the LAM/ICM assembly 1 is about 50
volts (or more accurately about 2 volts greater than the forward
voltage of the LAM). The microcontroller 66 controls the FET switch
67 to fine tune the amount of current supplied to the LEDs of the
LAM by adjusting the voltage drop across the FET switch to that
amount required to achieve the necessary current flow. The voltage
drop across FET switch 67 is about two volts or less depending on
the current required, it will be nearest zero when maximum current
is flowing and nearest 2 volts when minimum current is flowing.
Note that to turn the LEDs off, the FET switch will be turned off,
and the voltage across it will be much greater than 2 volts, but
since no current is flowing through the FET, no power will be
generated within the FET. To prevent excessive power dissipation by
the FET when operating in the linear region, the voltage applied to
the ICM must be within two volts of the forward voltage required to
illuminate the LED. To accomplish this for a desired LED brightness
(desired amount of current flow through the LEDs of the LAM), the
microcontroller 66 sends a zero to ten voltage dimming control
signal 89 back to the AC-to-DC power supply circuit 88 via
conductor 90, and data terminal 15. The microcontroller 66 uses
this control signal 89 to increase and to decrease the magnitude of
the constant voltage being output by the AC-to-DC power supply
circuit 88. The circuit components 69, 78, 66 and 65 are powered
from a low DC supply voltage such as 3 volts DC. A component
voltage supply circuit 91 generates this 3 volt supply voltage from
the 50 volts across pins 13 and 14. The 3 volt supply voltage is
supplied onto voltage supply conductor 90. Conductor 93 is the
ground reference conductor for the component supply voltage.
Because only a small amount of power is required to power the
circuitry embedded in the ICM, the component voltage supply circuit
91 may be a simple linear voltage regulator.
[0054] FIG. 16 is a top-down diagram of another example of a LAM
usable with the ICM. In this example, there are multiple LAM
contact pads in each corner of the LAM, and there are multiple
separately controllable strings of LED dice. One of these strings
includes LED dice 101-110. An LED drive current can be supplied to
this string via LAM contact pad 111 and LAM contact pad 112. There
are six such separately controllable strings of the LED dice. The
GaN temperature sensing diode is identified by reference numeral
32. The LAM contact pads through which the GaN temperature sensing
diode 32 is driven and monitored are LAM contact pads 113 and 114.
Reference numeral 34 identifies the rim that retains the silicone
that covers the LED dice. The silicone is not illustrated in FIG.
16 so that the LED dice disposed under it can be seen in the
illustration.
[0055] FIG. 17 is a diagram of an LAM/ICM assembly 115 in
accordance with a third novel aspect. The LAM/ICM assembly 115 is
similar to the LAM/ICM assembly 1 of FIG. 13 explained above,
except that: 1) the LAM/ICM assembly 115 of FIG. 17 does not output
a 0-10 volt dimming control signal, and 2) the LAM/ICM assembly 115
includes a switching DC-to-DC converter 116. In the example of FIG.
17, the switching DC-to-DC converter is a buck converter.
[0056] FIG. 18 is a more detailed diagram of the buck converter
116. The buck converter 116 includes a programmable oscillator 117,
a switch 118, a diode 119, and inductor 120, and a capacitor 121.
Programmable oscillator 117 supplies a rectangular wave digital
drive signal 122 to the switch 118. This drive signal causes the
switch to turn on and off in a cyclical fashion. The 50-volt supply
voltage from pin 13 is received between conductor 123 and conductor
124. From this 50 volts supply voltage, the buck converter 116
generates and outputs the LED drive current 74 at about 48 volts to
the LAM via conductor 125. Microcontroller 66 adjusts the frequency
and/or duty cycle of signal 112 by sending multi-bit digital
control information 126 to the oscillator 116 across conductors
127. By adjusting the frequency and/or duty cycle of signal 112,
the microcontroller 66 controls the magnitude of the nominal output
current 74 that the buck converter 116 supplies on conductor 125 to
the LEDs of the LAM.
[0057] FIG. 19 is a table that sets forth parameters of operation
for the buck converter 116 using 10 MHz nominal switching frequency
for the purpose of this explanation. The switching frequency can be
substantially higher, as required by the voltages and currents of a
particular LAM.
[0058] FIG. 20 is a diagram illustrating a first way to drive
multiple LED strings with multiple buck converters, where the
multiple buck converters are parts of the ICM. In the example of
FIG. 20, the buck converter block 116 of FIG. 17 actually includes
multiple buck converters 128-133. In addition, the LAM includes
multiple strings 134-139 of LEDs that can be driven independently.
Microcontroller 66 controls each of the buck converters separately
by sending each buck converter different digital control
information across different control lines. The microcontroller 66
controls the frequency and/or duty cycle output by each buck
converter's programmable oscillator 117 separately. The
microcontroller 66 monitors current flow through each string of
LEDs one at a time using the same single current sense resistor 77.
Providing multiple buck converters in this way reduces the physical
size of the inductors of the buck converters as indicated in the
right column of FIG. 19. Where six LED strings are separately
driven, each by a separate buck converter, the approximate physical
size of the inductor of each buck converter is 2.5 mm by 2.5 mm by
1.0 mm. This small inductor size facilitates encapsulation in a
slim ICM profile. While it has been illustrated that each buck
converter could be controlled by individual control signals, it is
equally possible to implement the system where a single oscillator
is used to drive multiple buck converter circuits composed only of
the switch 118, diode 119, inductor 120 and capacitor 121, thus
further saving on the amount of components required while keeping
the physical size of the components as small as possible.
[0059] FIG. 21 is a diagram illustrating a second way to drive
multiple LED strings with multiple buck converters, where the
multiple buck converters are parts of the ICM. In this case, each
string of LEDs has a corresponding dedicated current sense resistor
and FET switch. Current sense resistor 140 and FET switch 146 are
for the first LED string 134. Current sense resistor 141 and FET
switch 147 are for the second LED string 135. Current sense
resistor 145 and FET switch 151 are for the sixth LED string
139.
[0060] FIG. 22 is a diagram of a lighting system 152 that includes
multiple instances of the LAM/ICM assembly 115 of FIG. 17 in
accordance with the third novel aspect. Lighting system 152
includes an AC-to-DC power supply 153, multiple LAM/ICM assemblies
154-159 of the type shown in FIG. 17, and internet connectivity
circuitry 95. Bidirectional communication between each of the
LAM/ICM assemblies and the internet 96 via internet connectivity
circuitry 95 is the same as described above in connection with FIG.
14. Unlike the AC-to-DC power supply 88 of the embodiment of FIG.
14 that outputs a regulated substantially constant current (the
magnitude of which is adjustable), the AC-to-DC power supply 153 of
the embodiment of FIG. 22 outputs a substantially constant voltage
that is only roughly regulated. This roughly regulated voltage, in
the example of FIG. 22, is 50 volts. This roughly regulated voltage
is supplied in parallel to the many LAM/ICM assemblies via
conductors 161 and 162 as shown. The control of the amount of LED
drive current supplied to the LEDs of an individual LAM/ICM
assembly is controlled by the switching DC-to-DC converter (for
example, a buck converter) within the LAM/ICM assembly itself. Each
LAM/ICM assembly controls the amount of LED drive current being
supplied to its own LEDs. The AC-to-DC power supply 153 therefore
can output a supply voltage that is only roughly regulated. The
AC-to-DC power supply 153 need not receive any 0-10 volt control
signal to control its output.
[0061] Although an ICM having an embedded DC-to-DC converter is
described above in connection with a specific example in which the
switching DC-to-DC converter embedded in the ICM is a step-down
buck converter, this is but one example. In other examples, the
embedded switching DC-to-DC converter is a boost converter whose
input voltage is lower than its output voltage. The voltage as
received by the embedded boost converter is lower than the voltage
(LEDDC) at which the LED array is driven. In other examples, the
embedded switching DC-to-DC converter is a combination boost/buck
converter whose incoming input voltage can be either higher or
lower than the converter output voltage. The voltage as received by
the embedded boost/buck converter may be higher or lower than the
voltage (LEDDC) at which the LED array is driven. The embedded
switching DC-to-DC converter may also be a Single-Ended
Primary-Inductor Converter) SEPIC converter whose output voltage
can be less than, equal to, or greater than its input voltage. Any
DC-to-DC converter topology whose characteristics are suitable for
the ICM application can be employed.
[0062] Although certain specific embodiments are described above
for instructional purposes, the teachings of this patent document
have general applicability and are not limited to the specific
embodiments described above. Accordingly, various modifications,
adaptations, and combinations of various features of the described
embodiments can be practiced without departing from the scope of
the invention as set forth in the claims.
* * * * *