Abstract
Apparatuses, systems and methods for regulating the output currents of a power supply at a target output current include a buck converter module operably connected to a power source and a load. A first switch couples the power source to the buck converter module during a first period of a given operating cycle, while the buck converter module stores and provides electrical power to the load. During a second period, the buck converter may discharge the electrical power stored during the first period. A current sensor senses the currents during at least one of the first period and the second period and, over the operating cycle, the switching is adjusted so the average output current equals the target output current. Adjustments to the first and second period durations result in maximum and a minimum currents symmetrically disposed about the average current provided to the load during the operating cycle.
Claims
1. A power regulating device comprising: a buck converter module configured, during an OFF period (t.sub.OFF) of a current operating cycle (n), to provide an output current that decreases to a load until a minimum current threshold is reached, the OFF period (t.sub.OFF) including a recover period (t.sub.D) followed by a second period during which the output current corresponds to a decreasing ramp function.
2. The power regulating device of claim 1, further comprising: a driver module, coupled to the buck converter module, configured to: sense an output voltage of the buck converter module; determine the output current based on the output voltage; and end the OFF period (t.sub.OFF) when the output current reaches the minimum current threshold.
3. The power regulating device of claim 2, wherein the output voltage during the OFF period (t.sub.OFF) corresponds to a decreasing ramp function.
4. The power regulating device of claim 2, wherein the driver module further comprises: a period compare module which compares, over two or more operating cycles, an actual switching period to a target switching period; and flushes out permutations in the output current.
5. The power regulating device of claim 2, wherein, during an ON period (t.sub.ON) of the current operating cycle (n), the driver module increases the output current to the load until a maximum current threshold is reached.
6. The power regulating device of claim 5, wherein the driver module adjusts the maximum current threshold so that an operating frequency (F(n)) for the current operating cycle (n) is defined by:
F(n)=1/(t.sub.(ON(n))+t.sub.(OFF(n))).
7. The power regulating device of claim 6, wherein the operating frequency (F(n)) satisfies an electro-magnetic compatibility (EMC) requirement.
8. The power regulating device of claim 1, wherein the buck converter module comprises an inductor having an inductance (L); and wherein an operating frequency (F(n)) for the current operating cycle (n) corresponds to a ratio of an output voltage to the inductance (L).
9. The power regulating device of claim 4, wherein the load further comprises at least one light-emitting-diode (LED) unit; and wherein an LED pixel driver module, coupled to the LED unit, rapidly changes the output current demanded by the load.
10. A power regulating device, comprising: a buck converter module configured, during an OFF period (t.sub.OFF) of a current operating cycle (n), to provide an output current that decreases to a load until a minimum current threshold is reached, the buck converter module having an operating frequency (F(n)) over two or more operating cycles equal to a target switching period.
11. A system comprising: a light emitting diode (LED) unit; a power converter, coupled to the LED unit, providing an output voltage and an output current to the LED unit; and a driver module, coupled to the power converter, which: monitors the output voltage; determines, based on the output voltage, the output current; and during an OFF period (t.sub.OFF) of a current operating cycle (n) of the LED unit: decreases the output current until a minimum current threshold is reached; and terminates the OFF period (t.sub.OFF) when the output current reaches the minimum current threshold, the OFF period (t.sub.OFF) including a recover period (t.sub.D) followed by a second period during which the output current corresponds to a decreasing ramp function.
12. The system of claim 11, wherein the driver module further comprises: a current sensor comprising a sensing resistor coupled to an operational amplifier.
13. The system of claim 11, wherein, during an ON period (t.sub.ON) of the current operating cycle (n), the driver module increases the output current until a maximum current threshold is reached; and wherein the maximum current threshold corresponds to an operating frequency (F(n)) defined by:
F(n)=1/(t.sub.(ON(n))+t.sub.(OFF(n))).
14. The system of claim 13, wherein the operating frequency (F(n)) satisfies an electro-magnetic compatibility (EMC) requirement.
15. The system of claim 14, wherein the power converter further comprises: a buck converter module comprising an inductor having an inductance (L); and wherein an operating frequency (F(n)) is defined by a ratio of the output voltage to the inductance (L).
16. The system of claim 12, wherein the current sensor senses the output current during an ON period (t.sub.ON) and the OFF period (t.sub.OFF).
17. A method for providing adaptive on-time control of a light emitting diode (LED) unit, comprising: monitoring an output voltage provided to a light emitting diode (LED) unit, the LED unit including, during a given operating cycle (n), an ON time (t.sub.ON) and an OFF time (t.sub.OFF), the OFF time (t.sub.OFF) including a recover period (t.sub.D) followed by a second period during which an output current corresponds to a decreasing ramp function; determining, based on the output voltage, an output current provided to the LED unit; increasing, during the ON time (t.sub.ON), the output current until a maximum current threshold is reached.
18. The method of claim 17, wherein a buck converter module, having an inductor with an inductance (L), provides the output voltage and the output current to the LED unit; and wherein an operating frequency (F(n)) is defined by a ratio of the output voltage to the inductance (L).
19. The method of claim 17, further comprising: decreasing, during the OFF time (t.sub.OFF), the output current until a minimum current threshold is reached, the maximum current threshold being selected based on an operating frequency (fin)) defined by:
F(n)=1/(t.sub.(ON(n))+t.sub.(OFF(n))).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The features, aspects, advantages, functions, modules and components of the apparatus, systems and methods provided by the various embodiments of the present disclosure are further disclosed herein with regard to at least one of the following descriptions and accompanying drawing figures.
(2) FIG. 1 is schematic representation of a prior art approach to regulating the operation of buck converters driving LED units.
(3) FIG. 2 is a timing diagram illustrating the resulting ripple current that may be produced in conjunction with the use of the prior art approach of FIG. 1.
(4) FIG. 3 is a schematic diagram illustrating an apparatus, a driver module, for use in regulating the operation of a buck converter module, by regulating the average current produced by the buck converter module, in accordance with at least one embodiment of the present disclosure.
(5) FIG. 4A is a timing diagram illustrating the principles of operation of a first, “hi” switch used in the apparatus of FIG. 3 and in accordance with at least one embodiment of the present disclosure.
(6) FIG. 4B is a timing diagram illustrating the principles of operation of a second, “low” switch used in the apparatus of FIG. 3, and in accordance with at least one embodiment of the present disclosure.
(7) FIG. 4C is a timing diagram illustrating the regulation of the average current provided by a buck driver module to at least one LED unit, as the operation of such buck driver module is regulated per the apparatus of FIG. 3 and in accordance with at least one embodiment of the present disclosure.
(8) FIG. 5 is a schematic diagram illustrating an apparatus, a regulating module, for use in controlling the principles of operation of the driver module of FIG. 3, in accordance with at least one embodiment of the present disclosure.
(9) FIG. 6 is a schematic diagram illustrating an apparatus, a second regulating module, for use in controlling the principles of operation of the driver module of FIG. 3, in accordance with at least one embodiment of the present disclosure.
DETAILED DESCRIPTION
(10) The various embodiments described herein are directed to apparatus, systems and methods by which the average current of a direct current (DC) buck converter module may be regulated. While the various embodiments set forth herein, and as shown in the attached drawing figures, provide sufficient information for a person of ordinary skill in the art to practice one or more of the inventions, as claimed herein or as later claimed in any application claiming priority to this disclosure, it is to be appreciated that one or more embodiments may be practiced without one or more of the details provided herein. As such, the various embodiments described herein are provided by way of example and are not intended and should not be used to limit the scope of any invention claimed to any particular embodiment.
(11) As shown in FIG. 3 and for at least one embodiment of the present disclosure, a driver module 300 is provided for sensing and regulating the current, I.sub.LED, provided to one or more LED units 108a-n. Driver module 300 may include a DCDC buck converter module 104.
(12) It is to be appreciated, that current I.sub.LED will vary over time and is the same as the current produced by buck converter module 104 at any given time. Buck converter module 104 includes a coil 122 having an inductance L, a capacitor 124 having a capacitance C.sub.1, and at least one “high” switch 304 and one diode 313. It is to be appreciated that for at least one embodiment of the present disclosure, the sensing and regulating of current I.sub.LED is independent of the inductance and capacitances used for any given implementation. The inductance and capacitance values being used for the DCDC buck converter module 104 may be selected by a person of ordinary skill in the art based upon well-known electrical circuit design principles which are incorporated herein by reference and by inherency.
(13) Driver module 300 may be configured to include two switches, “hi” switch 304 and “low” switch 306, which are used to control the “on” and “off” cycles of buck converter module 104. In accordance with at least one embodiment, switches 304 and 306 may be MOSFET transistors. In FIG. 3, elements 312 and 313 respectively represent the parasitic capacitance and parasitic diode properties of low switch 306. In other embodiments, other type of transistor or other switches may be utilized. The current I.sub.SW1 across “hi” switch 304 and the current I.sub.SW2 across “low” switch 306 are sensed during their respective “on” times by respective hi current sensor module 314 and low current sensor module 316. Any known devices, modules, techniques or otherwise may be used to monitor the currents flowing across the respective hi switch 304 and low switch 306 during the respective states of operation of the driver module 300. One example of such known current sensing devices is the user of a sensing resistor. Further, it is to be appreciated that internal current sensing on one or both of the hi switch 304 and the low switch 306 may be used in one or more embodiments of the present disclosure.
(14) As further shown in FIG. 3 and as additionally shown in FIG. 5, “hi” lead 308 and “low” lead 310 couple driver module 300 with regulating module 500. At least one embodiment of regulating module 500 is described below and shown in FIG. 5. Leads 308 and 310 respectively communicate signals I.sub.sense1 and I.sub.sense2 representative of currents I.sub.SW1 and I.sub.SW2, from driver module 300 to regulating module 500.
(15) As further shown for at least the embodiment illustrated in FIG. 5, driver module 300 receives power V.sub.in from a source 102 (not shown in FIG. 3) or another power source. It is to be appreciated that driver module 300 may receive power from any source configured to provide the desired voltage or voltage ranges. Such power sources are well-known in the art and are incorporated herein by reference and inherency. In accordance with at least one embodiment of the present disclosure, V.sub.in=12 volts DC and V.sub.LED=10 volts DC may be possible values.
(16) The principles of operation of driver module 300 are shown in FIGS. 4A, 4B and 4C, where FIG. 4A shows the characteristics of current I.sub.SW1, FIG. 4B shows the characteristics of current I.sub.SW2, and FIG. 4C shows the resulting I.sub.LED current provided to the LED units by the buck converter module 104. More specifically, in FIGS. 4A, 4B and 4C, those time periods when the buck converter module 104 is considered “on” and “off” are respectively shown as times t.sub.ON and t.sub.OFF. In accordance with the present naming convention, t.sub.ON represents time period t1.sub.n to t3.sub.n, where n is an integer and represents a given cycle of operation of the buck converter module, where a single cycle includes the time period occurring from when the buck converter module is switched into an “on” state, then to an “off” state and then to immediately prior to it returning to an “on” state). More specifically, when hi switch 304 is “closed” and low switch 306 is “open”, the buck converter module is considered to be in the “on” state. Contrarily, t.sub.OFF represents the time period from t3.sub.n to t5.sub.n where t5.sub.n=t1.sub.(n+1) and t5.sub.n and t1.sub.(n+1) both represent the beginning of the next cycle for the buck converter module 104. That is t.sub.OFF occurs when hi switch 304 is open and low switch 306 is closed. It is to be appreciated that for at least one embodiment, the operating states (on/off) of hi switch 304 and low switch 306 are diametrically opposed. In accordance with other embodiments, some delay and overlap in respective “on” and “off” times may occur between the irrespective “on” and “off” states of the hi and low switches 304 and 306 respectively. For purposes of this disclosure, such delays, when arising in the Nano-Second range of 1 ηSec. to 10 ηSec. are considered to be insubstantial, such that for all practical purposes the switching “on” and “off” (and the inverse operations thereof) of the hi switch 304 and the low switches 306 res are considered to occur substantially simultaneously.
(17) In at least one embodiment, time tan, which as shown in FIG. 4A is the beginning of the t.sub.OFF period, is determined to occur when the I.sub.sense1 current reaches I.sub.MAX. Similarly, for at least one embodiment, time t5.sub.n=(t1.sub.(n+1)) is determined to occur when the I.sub.sense2 current reaches I.sub.MIN. It is to be appreciated that by adjusting the values of I.sub.MAX and I.sub.MIN the time periods t3.sub.n, and t5.sub.n (t1.sub.(n+1)) are obtained. By adjusting the values I.sub.MAX and I.sub.MIN, symmetry of I.sub.MAX and I.sub.MIN relative to a desired target current I.sub.TAR the resulting average current I.sub.AVG can be obtained and equaling a desired target current I.sub.TAR, where the target current is the desired operating current for the LED units 108a-n. It is to be appreciated that I.sub.TAR may be pre-determined, specified in advance, determined experimentally, calibrated once or repeatedly or may be otherwise identified for use in accordance with a given one or more LED units 108a-n. It is to be further appreciated that the value of I.sub.TAR may vary in accordance with the principles of operations used in conjunction with a given (if any) pixel driver module 110 used in conjunction with one or more embodiments of the present disclosure.
(18) As shown in FIG. 4A for at least one embodiment of the present disclosure, time tc represents the time period t1.sub.n to t2.sub.n used to charge the parasitic and/or additional capacitance C.sub.2 of the buck converter module 304. As discussed above, such parasitic capacitance, as represented by element 312, may arise, for example, in association with the activation of the hi switch 304 itself, or otherwise. As shown, during the charging of second capacitance, current I.sub.SW1 through hi switch 304 initially has a peak current I.sub.C2. For at least one embodiment, current I.sub.SW1 sensed during time period tc may be masked and is not used to regulate the average current provided by driver module 300 to LED units 108a-n. After time period tc current I.sub.SW1 may be sensed and generally increases from a value I.sub.SW1Min to the maximum current I.sub.MAX provided by driver module 104 to the LED units 108a-n. Accordingly, the currents sensed I.sub.SENSE1 and used by regulating module 500 to regulate the operation of driver module 300 may be expressed mathematically, for any given cycle n, as shown in Equation 1.
I.sub.SENSE1=Isw1 Equation 1:
(19) Per Equation 1, for any given cycle n, t2.sub.n is the time from when the current sensed by high current sensor 314 is representative of the coil current while the hi switch 304 is “on”, and t3.sub.n is the time at which the hi switch 304 is turned “off.”
(20) As shown in FIG. 4B for at least one embodiment of the present disclosure, after the hi switch 304 is turned off at time t3.sub.n, low switch 306 is turned on and diode 126 reverses the node of the buck converter 104 to the low switch 306. At the beginning of the “off” time t.sub.OFF, at time t3.sub.n, the sensed current I.sub.sw2 flowing through low switch 306 initially presents itself as a recovery current induced by diode 126. The recovery current generally occurs over time period t3.sub.n to t4.sub.n, which is represented in FIG. 4B by time period td. For at least one embodiment, current I.sub.SW2 sensed during time period td may be masked and may not be sampled or otherwise used to regulate the average current provided by driver module 300 to LED units 108a-n. After time period td current I.sub.SW2 may be sensed and generally decreases from a value I.sub.SW2Max to the minimum current him provided by driver module 104 to the LED units 108a-n. Accordingly, the currents I.sub.SENSE2 used by regulating module 500 to regulate the operation of driver module 300 during its “off” state may be expressed mathematically, for any given cycle n, as shown in Equation 2.
I.sub.SENSE2=Isw2 Equation 2:
(21) For any given cycle n, t4.sub.n is the time from when the current sensed by low current sensor 306 is representative of the coil current while the low switch 306 is “on”, and t1.sub.(n+1) is the time at which the low switch 306 is turned “off” and the cycle then repeats.
(22) As shown in FIG. 4C, the “on” and “off” states of the driver module 300 may be adjusted such that the I.sub.MAX and I.sub.MIN values are symmetrical around the I.sub.TAR current and the resulting current I.sub.LED provided to the LED units 108a-n can be set at the target average current I.sub.TAR. That is, the average LED current I.sub.AVG=I.sub.TAR when symmetry exists. Such symmetry may be expressed as the change in current ΔI over a cycle where the change ranges from I.sub.MAX to I.sub.MIN. It is to be appreciated that ideally, half this change
(23)
(the current adjustment) arises, respectively, above and below the average current I.sub.AVG such that symmetry exists. This relationship is expressed in Equation 3.
(24)
(25) Per Equation 3, I.sub.AVG may be expressed in terms of the peaks (which are shown in FIG. 4C as the I.sub.MAX value at time t3.sup.n) and valleys (which are shown in FIG. 4C as the I.sub.MIN value at time t1.sup.(n+1)) of the current I.sub.LED 400 provided by driver module 300 to the LED units 108a-n. This relationship may also be expressed in terms of such ΔI's, as shown in Equation 4.
(26)
(27) Further, it should be appreciated that when symmetry exists between I.sub.MAX and I.sub.MIN, I.sub.TAR does not depend on the inductance value L of coil 122. Likewise, I.sub.TAR does not depend on the voltage V.sub.in provided, for example, by a power source 102, or on the load (expressed as the output voltage V.sub.LED) needed by LED units 108a-n at any given time. Further, it should be appreciated that when symmetry exists between I.sub.MAX and I.sub.MIN around I.sub.TAR, the average LED value I.sub.AVG does not depend at all on ΔI value. It means that ΔI value is free to be controlled independently to the desired LED value I.sub.TAR.
(28) Further, it is to be appreciated that the LED current commonly presents itself, over one cycle to a next, as a constantly varying current I.sub.LED 400 whose boundaries at any given instance in time are defined by I.sub.MAX, when driver module 300 is “on”, and, by I.sub.MIN, when driver module 300 is “off”.
(29) The “on” and “off” times of driver module 300 can also be expressed in terms of the switching frequency F.sub.n of the driver module 300, where the frequency F.sub.n is inversely proportional to the time length T.sub.n of any given cycle n, where the length of any given cycle is the time period T.sub.n as shown in Equation 5.
F.sub.n=1/(t.sub.ONn+t.sub.OFFn)=1/T.sub.n. Equation 5:
(30) Accordingly, for at least one embodiment of the present disclosure, the switching frequency F.sub.n can be expressed in terms of a target switching period T.sub.TAR for driver module 300, which can also be expressed in terms of the voltages and inductance properties of a given driver module, for any given cycle n, as shown in Equation 6.
(31)
(32) In view of these expressions and relationships, and as discussed further below with reference to FIG. 5, regulating module 500 may control the I.sub.LED current at the desired I.sub.TAR=I.sub.AVG value by adjusting the I.sub.MAX and I.sub.MIN threshold limits symmetrically above and below I.sub.TAR independently of ΔI value according to Equation 4 as well as regulating module 500 may control the frequency F.sub.n of each cycle as well as the timing of when driver module 300 switches from the “on” to “off” states within any given cycle by adjusting the ΔI value according to Equation 6.
(33) Referring now to FIG. 5 for at least one embodiment of the present disclosure, a regulating module 500 for controlling the switching frequency of a driver module 300 as well as the respective “on” and “off” times of such a driver module 300 is shown. The regulating module 500 may be coupled to hi lead 308, low lead 310, target input lead 502, hi switch lead 504, and low switch lead 506. It is to be appreciated that other leads, such as power, programming, ground, clocking and others and/or other commonly used components may be utilized, but, are not shown in FIG. 5.
(34) Regulating module 500 may include a first summing module 508 coupled to each of the target input lead 502, adjustment lead 510, and max. current lead 512. First summing module 508 may be configured to sum a target current signal, I.sub.TAR, received via lead 502, with a current adjustment signal ΔI/2, received via lead 510, and output the resulting I.sub.MAX current signal via lead 512.
(35) Regulating module 500 may include a second summing module 514 coupled to each of the target input lead 502, adjustment lead 510, and min current lead 516. Second summing module 514 may be configured to sum the target current signal, I.sub.TAR, received via lead 502, with the opposite sign value of the current adjustment signal ΔI/2 received via lead 510, and output the resulting I.sub.MIN current signal via lead 516. It is to be appreciated, that while shown in the embodiment of FIG. 5 as utilizing two summing modules, 508 and 514, such modules may be provided in a single module where the value of the adjustment signal 510 varies based on the state (i.e., “on” or “off”) of the driver module 300 at any given time.
(36) As further shown for at least the embodiment depicted in FIG. 5, regulating module 500 may also be configured to include a frequency adjustment module 518, which outputs the current adjustment signal ΔI/2. For at least one embodiment, the frequency adjustment module 518 will output a stable adjustment signal ΔI/2 within a given number of pre-determined cycles following initiation of the driver module for a first cycle at time t1.sup.1. In at least one embodiment, the frequency adjustment module 518 may be replaced by any module adjusting symmetrically I.sub.MAX and I.sub.Min threshold currents versus the target average current I.sub.TAR via any regulation technique. Examples of such regulation techniques include but are not limited to proportional, integral-proportional, derivative-integral-proportional and other known techniques.
(37) It is to be appreciated that in accordance with at least one embodiment of the present disclosure, for an ideal implementation, the combinations of summing modules 508 and 514 and the signal amplitude of current adjustment signal ΔI/2 may result in I.sub.AVG commonly being equal to I.sub.TAR, with any differences, if any, not effecting the mode of operation of the LED units 108a-n. It is to be appreciated that in non-ideal implementations, pure symmetry may not arise due to, for example, current losses occurring during switching activities, comparator 534 and 524 delays, delays in sensing elements 314 and 316, errors in summing modules 508 and 514, comparator offsets in 534 and 524, delay in pre-drivers 530, 532 or in transistors 304 and 306, delay in control module 528 and the like. Generally, any such differences may result in insubstantial decreases in the performance of the LED units 108a-n. Such insubstantial differences arising within known and/or expected performance ranges for the LED units 108a-n. Further, it is to be appreciated that, for an ideal circuit, when I.sub.AVG=I.sub.TAR the LED current I.sub.LED does not need to be regulated and will instead be correctly set at the desired current.
(38) In accordance with at least one embodiment of the present disclosure, it is to be appreciated that the effective average current I.sub.EAVG may be sensed by any state-of-the-art technique not presented here. The effective average current I.sub.EAVG could be provided to each of the first and second summing modules 508 and 514 as a second order correction signal. It is to be appreciated that such a second order correction signal may allow for the apparatus to adjust for errors that otherwise arise from the use of non-ideal components.
(39) Frequency adjustment module 518 may be operably coupled, via change time period lead 520, to a period compare module 522. As further shown for at least one embodiment of the present disclosure, the period compare module 522 may be configured to determine the state of operation of the driver module 300 based, for example on detecting when the time period signal ΔT occurs. It is to be appreciated that for at least one embodiment of the present disclosure the period compare module 522 may be replaced by a module which compares an actual switching period (or frequency) to a target switching period (or frequency) over multiple cycles. Such a period compare module 522 may be utilized to flush-out permutations arising under operating conditions where the load demanded by the LED units 108a-n are rapidly changing, as may be the case, for example, when strobing, rapidly flashing or similar modes of operation may be desired. Further, it should be appreciated that the period compare module 522 may be implemented in either the analog circuit or digital circuits and processing domains.
(40) It is to be appreciated that for at least one embodiment, the period compare module 522 may compare the total time periods T or a portion thereof, such as t.sub.ON or t.sub.OFF as arising from one cycle to a next. In one embodiment, only the actual versus target “off” times for the driver module 300 are compared and for at least one embodiment ΔT=Δt.sub.OFF=t.sub.OFF.sup.(n)−t.sub.OFF(n−1). The inverse of ΔT is the desired switching frequency for the driver module 300. For at least one embodiment, the desired switching frequency is, for example, 2 MHz, and the corresponding target period is 500 ns.
(41) As further shown for at least the embodiment depicted in FIG. 5, regulating module 500 may also be configured to include a low comparator module 524 which is coupled to each of the period compare module 522 (via “set” lead 526), the second summing module 514 (via min current lead 516) and to the low current sensor module 316 (via low lead 310). Low comparator module 524 may be configured to monitor when the I.sub.SENSE2 current signal provided via the low lead 310 is equal to the I.sub.MIN threshold provided to the low comparator module 524 by the second summing module 514. As discussed previously above, when I.sub.SENSE2=I.sub.MIN a new cycle for the driver module 300 occurs. Accordingly, upon detecting I.sub.SENSE2=I.sub.MIN the low comparator module 524 outputs a “set” signal S, which designates the start of t.sub.ON and a new (n+1) cycle, to each of the period compare module 522 (via set lead 526) and to a driver control module 528.
(42) As further shown for at least the embodiment depicted in FIG. 5, the driver control module 528 may be configured, upon receiving the set signal S to initiate the closing of the hi switch 304 and the opening of the low switch 306, with the sequence of operation commencing from time periods t1.sub.n through t3.sub.n, as shown in FIG. 4A, with the “on” state.
(43) As shown for at least one embodiment of the present disclosure, driver control module 528 may be coupled via (optional) high switch module 530 and (optional) low switch module 532 to the respective hi switch 304 and low switch 306, via respective hi switch lead 504 and low switch lead 506. It is to be appreciated that the high switch module 530 and low switch module 532 are designated as optional components of regulating module 500 as the need for signal condition, including amplification, filtering or otherwise may vary based upon actual implementations of one or more of the embodiments described herein.
(44) As further shown for at least the embodiment depicted in FIG. 5, regulating module 500 may also be configured to include a hi comparator module 534. Hi comparator module 534 may be coupled to each of hi current sensor module 314 (via hi lead 308) and to first summing module 508 (via max current lead 512). Hi comparator module 534 may be configured to monitor when the I.sub.SENSE1 current signal provided via the hi lead 308 is equal to the I.sub.MAX threshold provided by the first summing module 508. As discussed previously above, when I.sub.SENSE1=I.sub.MAX the “off” portion of a given cycle n for the driver module 300 is deemed to occur. Accordingly, upon detecting I.sub.SENSE1=I.sub.MAX the hi comparator module 534 outputs a “reset” signal R, which designates the start of t.sub.OFF to the driver control module 528. It is to be appreciated that in accordance with at least one embodiment, the period compare module 522, or a second period compare module (not shown), may be utilized to provide further refinement of the I.sub.MAX currents which, when sensed by hi current sensor 314, initiate the triggering of the “off” period. That is, it is to be appreciated that the hi comparator module 534 may be configured to also communicate the reset signal R to the period compare module 522, which, in turn, determines whether any difference have occurred between the actual t.sub.OFF time and the t.sub.OFF target time and, if so, instructs the frequency adjustment module to output an adjustment signal ΔI/2 specifically targeted for increasing (or decreasing) the I.sub.MAX current signal. That is, it is to be appreciated that for one or more embodiments, separate adjustment signals ΔI/2 may be output by the adjustment module 518 so as to separately adjust the I.sub.MAX and I.sub.MIN current signals, as then being adjusted based on the then operating state of driver module 300. Such separate adjustments may be desired, for example, when adjustments to only one of the I.sub.MAX and I.sub.MIN current signals, and not both, is desired so as to provide a more precise symmetry of I.sub.MAX and I.sub.MIN with respect to I.sub.AVG. It is to be appreciated that such separate adjustment may arise in view of one or more operational, environmental or other constraints.
(45) Referring now to FIG. 6 and with respect to at least one embodiment of the present disclosure, a second regulating module 600 may be provided which may be configured for use with a single current sensing module 602. Per at least this embodiment, it is to be appreciated that the hi current sensor 314 and low current sensor 316, as shown in FIGS. 3 and 5, may be augmented and/or replaced by the single current sensing module 602. The single current sensing module 602 may desirably be positioned to sense the current across the coil 122 of the buck driver module 104 (see FIG. 3) by being positioned, for example, at the junction formed by leads extending from and coupling to each of the other the hi switch 304, low switch 306, and coil 122. It is to be appreciated that the coil current is essentially the LED current I.sub.LED flowing through the driver module 300. It is to be appreciated that for any embodiment the location of the single current sensing module 602 relative to the driver module 304 may vary provided, however, that the current provided to the LED units 108a-n during both the “on” and “off” states of any given cycle may be sensed. Further, per at least one embodiment, the single current sensing module 602 may be coupled to the low comparator module 524 (FIG. 5), to output thereto the I.sub.SENSE3 current signal via lead 604. It is to be appreciated that the I.sub.SENSE3 single sensed current signal equals I.sub.LED during all states and cycles of operation for the driver circuit 304.
(46) As further shown in FIG. 6 and with respect to at least one embodiment of the present disclosure, the hi comparator module 534 (FIG. 5) and low comparator module 524 (FIG. 5) may be replaced by a joint comparator module 601 which may be configured to operate with respect to two or more thresholds, such as the t.sub.ON and t.sub.OFF thresholds. Additionally, both the I.sub.MAX and I.sub.MIN current signals may be communicated by the first summing module 508 and the second summing module 514 to a multiplexer 606. The multiplexer 606 may be configured to communicate the corresponding I.sub.MIN or I.sub.MAX signal, as depending on the current state (“on” or “off”) then being sensed by the single current sensing module 602, to the joint comparator module 602.
(47) As further shown in FIG. 6 with respect to at least one embodiment of the present disclosure, the multiplexer 606 may be coupled to the joint comparator module 601 via lead 608 and the joint comparator module 601 may be configured to output the set signal S to multiplexer 606 via lead 610. The multiplexer 606 may be configured to toggle between the signals being provided on lead 512 and lead 516 based on the then corresponding state, “on” or “off” as represented by the set signal, of the driver module 300 for that given cycle n.
(48) Although various embodiments of the claimed invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of the claimed invention. Other embodiments are therefore contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.
