Combination High Power LED Strobe and Continuous Light

Abstract

An LED light is operated in both continuous steady output and, as desired, a periodic high power burst of light that drives the LED beyond its rated output for short periods. A single cost effective circuit to perform both types of control delivers highly regulated output under both high power burst mode and continuous mode while maintaining maximum feedback resolution in the primary (continuous) output mode. Active elements are used to switch the signals from conventional current sensing elements through a controlled scaling network before joining the rest of the regulating circuit. This results in ability to produce a high efficiency, well-regulated, fast rise and fall, rectangular average peak value waveform, electric current pulse to power a single or combination of LEDs to a high output level, effecting a transition between a constant lighting level and a higher output, pulsed duration lighting level for photographic and motion image capture.

Claims

1. In an LED power circuit with a feedback loop for controlling power to one or more LEDs in accordance with a setpoint input level to a power regulator in the circuit, the feedback loop providing an LED power level feedback signal from a sensing element to the regulator which can regulate power output to the LEDs to meet the setpoint, by regulating power, a system for pulsing the LEDs for a brief higher-power pulse of light when desired, comprising: at least one range scaling device for driving the LEDs at a higher output for said brief higher-power pulses, the range scaling device comprising a scaling network in the circuit, receiving the feedback signal from the sensing element and scaling the feedback signal to a lower value so that the lower feedback signal goes to the power regulator which raises power output to the LEDs to produce said brief higher-power pulse, and the scaling network being activated in response to an input control signal received in the LED power circuit.

2. The LED power circuit of claim 1, wherein said input control signal is received from the opening of a camera shutter.

3. The LED power circuit of claim 2, wherein the brief higher-power pulse has a duration determined by duration of the camera's shutter opening.

4. The LED power circuit of claim 1, wherein the brief higher-power pulse has a duration of 5 milliseconds or more.

5. The LED power circuit of claim 1, wherein the brief higher-power pulse is a high efficiency, well-regulated, fast rise and fall, rectangular average peak value waveform.

6. The LED power circuit of claim 1, contained in a portable lighthead connected to a rechargeable battery pack.

7. A self-contained powered luminaire comprising an LED or LED array with regulating circuitry with switching means within the circuitry allowing the LED array to operate in a primary continuous mode up to a continuous mode maximum input power or in a pulsed mode wherein the same LED or array or a portion of the LED array is pulsed to a higher regulated output light level of pulsed duration at an input power higher than continuous mode maximum input power utilizing the circuitry while maintaining maximum feedback control resolution in the primary continuous lighting mode.

8. The luminaire of claim 7, wherein the continuous mode maximum power produces at least 5000 lumens.

9. The luminaire of claim 7, wherein the LED comprises a COB LED array.

10. The luminaire of claim 7, wherein the output light level of pulsed duration is at an input power to the LED array four or more times the continuous mode maximum.

11. The luminaire of claim 7, wherein the switching means comprises at least one scaling network in the circuit, receiving one or more feedback signals from one or more sensor elements in the circuit and scaling the feedback signal to a lower value so that the lower feedback signal goes to a power regulator of the regulating circuitry which raises the output of the LEDs to a higher output for the pulsed duration.

12. The luminaire of claim 7, wherein the pulsing of the LED or array is initiated by an input control signal.

13. The luminaire of claim 12, wherein the input control signal is from the opening of a camera shutter.

14. The luminaire of claim 7, further including a rechargeable battery contained in a battery casing that forms a handle to hold the luminaire, the casing having a receiving element that allows the battery casing and luminaire to be releasably mounted on a light stand or tripod.

15. The luminaire of claim 14, wherein the battery casing has a charging port, such that when disengaged from the luminaire the battery can be charged remotely.

16. The luminaire of claim 7, including a lighthead containing the LEDs and circuitry, which comprise a coplanar LED and driver array that is sealed from weather and including optic elements that mount to the exterior of the lighthead creating a weather tight seal when installed.

17. The luminaire of claim 7, including a lighthead containing the LEDs and circuitry, and further including a rechargeable battery pack in a weathertight casing.

18. The luminaire of claim 17, wherein the lighthead connects to the battery using a USB-C cable.

19. The luminaire of claim 17, wherein the rechargeable battery pack has a capacity of at least 30 watt-hours.

20. The luminaire of claim 17, wherein the lighthead has a perimeter bayonet mount to attach optics in close proximity to the LEDs to focus or diffuse light from the LEDs.

21. The luminaire of claim 17, wherein the lighthead has a foamed metal matrix, brazed or otherwise thermally attached to a back side of a heat conducting plate holding the LEDs and circuitry, thus providing a large surface area for air cooling of the heat sink.

22. The luminaire of claim 7, wherein pulsing of the LED or array is initiated by an input control signal from opening of a camera shutter, the circuitry being synchronized with the camera shutter using wireless communication.

23. The luminaire of claim 7, further including capacitors in the regulating circuitry that allow a higher power buildup for the higher-regulated output level, to support higher power pulsed bursts of light.

24. The luminaire of claim 7, wherein the switching means includes a signal-level active switch arrangement and network of physically smaller signal-level passive components to scale the level of the signal coming from a conventional, fixed-value sensing element, such that when the active signal-level active switch arrangement is engaged, feedback signal gains are changed, equivalent to characteristic values of the sensing element being changed.

25. The luminaire of claim 7, wherein the switching means includes electrical sense elements to create multiple signal connection tap locations, or a sense element with multiple tap connection locations, to allow signal-level switch circuitry to connect to portions of the sense element or series, to facilitate quickly changing to a feedback signal which is otherwise proportional to the signal from the whole sense element or arrangement.

26. The LED power circuit of claim 6, that has user selectable modes including continuous lighting up to a maximum rating of the LED or LED array or as determined by the available power supply, as well as a higher powered pulse mode that is initiated by a signal indicating a camera shutter or other image capture sensor activation is occurring.

Description

DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a perspective view showing an LED lighthead of the invention as mounted on a battery enclosure that can serve as a handle.

[0023] FIG. 2 is an exploded perspective view showing a face of an assembly of a driver circuit and LED as they are attached to a heat sink.

[0024] FIGS. 3 and 3A are elevation and perspective views, exploded, showing a bayonet mount and holder that mounts to the face of the lighthead.

[0025] FIG. 4 is a perspective view showing the face of the LED array and parameter driver circuit seen through the mounted optic, as part of the lighthead.

[0026] FIG. 5 is a schematic circuit diagram to illustrate a prior art LED power control circuit, without the features of the invention.

[0027] FIG. 6 is a schematic circuit diagram showing an LED power circuit according to the invention, with controlled scaling networks to change the value of feedback signals.

[0028] FIG. 7 shows a schematic prior art circuit with a boost switching regulator circuit.

[0029] FIG. 8 is a similar schematic view with features of the invention applied to a boost switching regulator circuit.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] FIG. 1 shows a lighthead 10 of the invention mounted on a tubular battery enclosure 12 that is also a handle for the light allowing it to be hand held. On the face of the light is a user mounted optic holder 14 retaining an optic that focuses the native beam from the LED light. The head shows fins 16 of a heat sink that removes heat from electronics and LED array. A power dial 18 on the back of the lighthead allows the user to adjust the output from, e.g., 500 lumens to the maximum power output. Also visible on the back side of the lighthead is a USB-c cable 20 connecting the lighthead 10 and circular battery pack 12. Adjacent to the USB-c connector as it enters the battery pack is a raised release lever 22 that when pressed allows the lighthead to slide off the battery. Visible on the bottom of the battery pack is a dovetail feature identical to the dovetail feature 24 at the base of the lighthead. These mounting features allow either the complete light and battery or the lighthead alone to mount to typical photography stands including tripods and lightstand with an interface piece. The lighthead may also include mounting features to support attaching of soft boxes or other light shaping tools.

[0031] A port 25 is provided to receive a camera shutter signal for digital burst operation.

[0032] FIG. 2 shows the face of the assembly of the driver circuit 26 and LED 28 as they attach to the face of the heat sink 30. The driver circuit 26 is mounted coplanar with the LED 28. The LED drops into a slight cavity machined in the heat sink 30 that is about one half the depth of the overall LED height. This assembly is similar to that shown in U.S. patent application Ser. No. 15/973,382, now U.S. Pat. No. ______, the disclosure of which, in regard to LED array and lighthead structure, is incorporated herein by reference. The perimeter of the driver circuit board then screws down to the heat sink 30 and presses the LED tightly against the heat sink. Two or more spring arms 32 extending from the driver circuit board extend to press the LED down as well as make electrical contact with the LED to deliver the power to control the light output. The typical assembly will include a thermal paste or film that optimizes the thermal path from the LED to the heat sink 30. The heat sink shows cavities 34 that allow space for components mounted on the underside of the heat sink. These components may include capacitors that store charge to deliver the pulse of high power as well as large components such as inductors that would interfere with the beam pattern of the LED if mounted on the face. The face of the heat sink shows a circular cavity 36 around the perimeter that receives the optic holder which mounts with a one-quarter turn engagement and creates a watertight seal for the electronics and LED when installed.

[0033] Note that a small fan can be included in the assembly to increase heat dissipation of the heat sink. Further, interchangeable lightheads can be provided to allow the user to change the light color temperature with a head swap.

[0034] FIGS. 3 and 3A show the bayonet mount holder 14 and optic 38 that mount to the face of the lighthead, so that the beam is focused depending on the type of optic mounted in the holder. The beam focus can range from 90 degrees down to a tight 12 degree beam depending on what the user is trying to light.

[0035] FIG. 4 shows the face of the LED array 28 and perimeter driver circuit 26 seen through mounted optic that employs a perimeter seal using an O-ring against the face of the bayonet. Also visible are the cooling elements 16 on the back side of the head. In another embodiment the lighthead can be remote from and wired to a battery, such as for use on a drone. Another application is that the light unit can be synchronized to flash with a drone-mounted camera.

[0036] In a further embodiment the light unit is waterproof and submersible, for use in underwater photography.

[0037] FIG. 5 shows a generalized block diagram of a circuit for an LED arrangement controlled by a generalized conventional switching power supply regulator circuit of the prior art. LEDs are indicated at 40. Signal connections 42, 44 from sense elements 46 and 48 and a feedback compensation 50 are connected to a regulator functional block portion 52 of the circuit. Power output is regulated accordingly, as indicated at 54.

[0038] FIG. 6 shows a generalized block diagram/circuit diagram utilizing a conventional switching regulator 52 controlling an LED array 40, but with features in accordance with the invention, namely, controlled scaling networks 56, 58, 60 inserted between the sense element(s) 46, 48 and the switching regulator functional block 52. As discussed above, these controlled scaling networks scale the signal from at least one sensor element (three shown here) and feed the scaled-down feedback signal(s) to the switching regulator 52 as shown. The controlled scaling networks are controlled an input control range scale command signal as indicated at 62, which can be the opening of a camera shutter. Compensation by the regulator 52 is indicated at 64, compensation being based on the scaled feedback signal. Note that when the input control 62 does not call for scaling for a high-power pulse mode, the normal continuous light mode can be active, with adjustable level control as indicated at input control level command signal 66.

[0039] Note also that multiple sensing networks are indicated because there could be one or more controlled scaling network blocks depending on the complexity of the regulating section. Often, higher power regulator circuits use multiple feedback inputs and sense elements, and in order to achieve most accurate and fastest response, more than one signal needs to be scaled. The scaling network at 60 can be used to adjust the effective characteristics of the feedback loop compensation network at 50 in order to achieve best regulating performance in the two different modes of 1) primary output level and 2) higher-power pulse duration level, because the compensation network may need to be scaled or manipulated between the two modes. It is not required, but without manipulation of the compensation network, the higher-power pulse response may be slow or not be critically damped to provide the best possible rectangular pulse power shape and best regulation response in both modes. The compensation connection point of the regulator function block is connected to a point between the feedback summing and output amplifiers internal to the conventional regulator function block.

[0040] FIG. 7 shows a block circuit diagram of a conventional boost circuit topology version as in the prior art. This is the same style implementation with a switching regulator as in FIG. 5. Some LED power controls utilize such a boost circuit. A conventional boost circuit may in some cases provide a high-power pulse in response to a pulse on the input control level command signal. However, it will have poorer control resolution in the lower, constant output level range. The current system provides for rapid switching of the dynamic range to achieve fine control resolution in the low range while still providing good response and control in the higher-power pulse regulation range. Our method of applying controlled scaling network(s) in the feedback loop(s) (or being able to switch to different proportional signal tap connections on sense elements or arrangements of elements as described above) allows rapid changing of the regulation power range for the purpose of transitioning from one primary regulated output level to a significantly higher regulated output level and back again, while maintaining maximum feedback resolution in the primary level output range. Active elements are used to switch the signals from the conventional current sensing elements through a scale changing network before joining the rest of the regulating circuit. This method results in ability to produce a high efficiency, well-regulated, fast rise and fall, rectangular average peak value waveform, electric current pulse to power a single or combination of LEDs to a high output level, effecting a transition between a constant lighting level, and a higher output, pulsed duration lighting level.

[0041] FIG. 8 shows the conventional circuit of FIG. 7, but with the scaling that works for scaling down the feedback signal from sensors.

[0042] In a conventional LED control circuit there are sense elements that might sense current if the circuit is adjusting current to affect the output, or sense voltage or feedback from a switch and inductor element to affect output. The current innovation employs a controlled scaling network to intercept and scale the signal from the sense element before the signal is received by the switching regulator. The system controls the network based on the input control range scale command signal 62 and/or the input control level command signal. 66.

[0043] For example the input control range scale command signal (FIG. 6 or FIG. 8) may react in response to a signal that the camera shutter is opening. Based on that input from the camera, the scaling network intercepts the current sense signal and scales it to trick the circuit into delivering a pulse of power that is some multiple greater than the power the current sense element is otherwise requesting. The duration of the pulse can be controlled in any of several different ways, including but not limited to detecting light back from subject; a clock timer or programmed interval signal from a programmable controller; or a camera shutter duration signal.

[0044] The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.