WO2013026037A2

WO2013026037A2 - Current regulated power supply with dynamic voltage control

Info

Publication number: WO2013026037A2
Application number: PCT/US2012/051475
Authority: WO
Inventors: Michael Creighton
Original assignee: BIAS POWER Inc
Current assignee: BIAS POWER Inc
Priority date: 2011-08-17
Filing date: 2012-08-17
Publication date: 2013-02-21
Anticipated expiration: 2014-02-17
Also published as: WO2013026037A3

Abstract

Systems and apparatus for adaptive voltage output control. In one aspect, a system includes four circuits, the first circuit being a pulse-by-pulse current control circuit, the second circuit configured to signal the first circuit enabling the first circuit to maintain a constant output voltage, a third circuit providing a voltage reference, and a fourth circuit providing feedback to the second circuit, such that the system as a whole maintains a constant voltage and current output in the face of changes in the load.

Description

CURRENT REGULATED POWER SUPPLY WITH DYNAMIC VOLTAGE

CONTROL

TECHNICAL FIELD OF THE INVENTION This present invention relates to voltage control devices, and more particularly to voltage control devices for providing an acceptable voltage level to electrical devices having varying voltage demand requirements.

BACKGROUND

LED (Light Emitting Diode) lighting is becoming increasingly desirable as compared to traditional incandescent and/or florescent lighting due to its pleasing light qualities and low energy consumption. However, unlike traditional incandescent and/or florescent lighting. LED lighting or the LED components of the LED lighting requires a constant current to function properly. That is. an LED requires a constant current regardless of the the LED^*s forward

In this regard, it should be noted for most LEDs. the forward voltage will be dependent upon the temperature of the LED. As such, as the ambient temperature of the LED varies, so does the forward voltage required by the LED. But achieving a constant

of the LED is achieved maintaining the current at a constant value. Additionally, failing to maintain a constant current to the LED either shortens the life of the LED or reduces the luminosity of the LED.

The manufactures of lighting products will often design various groups (families) of lighting products, such as lighting fixtures, lamps, cabinet lights and the like, that have a similar style and can be intended to be used together in a lighting application. For example, a manufacture of lighting cabinets may design a family of lighting around a specific cabinet style, such as an under-cabinet lighting fixture. The family of cabinets may include one model that includes four LEDs. another model that includes six LEDs and still another model that includes ten LEDs. The family of lighting products could include a multitude of different light fixture designs with each light fixture design having its own desired light output level determined by the number of LEDs that the fixture contains. As such, each of the particular fixture models of the family may require a different number of LEDs with hich the fixture generates the light.

The goal of maintaining a constant current in conjunction with the differing number of LEDs require the manufacture of the family of light products to stock and

I utilize various different power supplies. For example, a light fixture with two LEDs might require a first power supply or driver while a light fixture with four LEDs would require a different power suppl and while a light fixture with eight LEDs will require still yet a different power supply.

in the applicant^'s experience, the typical power suppl (driver) has an effective range of about two to one. such that a first model LED may work w ell for a fixture having eight LEDs. but would not work well for an LED having, for example, three of four LEDs. As such the manufacturer would need to employ a different model power supply- to handle the four LED device. Thus the manufacture is forced to stock varying power supplies to accommodate all the models of a particular family of fixtures.

Additionally, the amount of space required for the power supply with which to power the LEDs also varies with different models of power supplies, thereby further complicating the design of families of light fixtures. Further, requiring the use and purchase of different drivers may prevent the manufacturer from realizing cost savings that are achieved by large quantity purchases, since the manufacture is forced to order and purchase her drivers in smaller batches of different drivers rather than purchasing her drivers in larger batches of a common driver.

SUMMARY

This specification describes technologies relating to. generally. AC-to-DC power conversion and particularly to current-regulated power supplies such as constant-current LED drivers.

In accordance with one embodiment, a current-regulated AC-to-DC power supply for loads having different voltage drops includes an AC voltage source, and an AC-to-DC converter coupled to said AC source for producing a controllable DC voltage. A current regulating circuit receives the DC voltage and includes a pair of load terminals for connecting the current-regulating circuit to a load. The current-regulating circuit supplies a regulated DC current output to the load connected to said terminals. A voltage-sensing circuit is coupled between the converter and one of the load terminals for dynamically adjusting the DC voltage according to the voltage drop across the load.

In one implementation, the current-regulating circuit includes a transistor connected to the same load terminal as the voltage-sensing circuit provides a controllable impedance in series with the load connected to the load terminals for regulating the DC current supplied to the load. The voltage-sensing circuit senses the voltage across the transistor.

In general, one innovative aspect of the subject matter described in this specification can be embodied in devices that include the capability of recharging batteries, performing electro-chemical plating such as silver plating, chrome plating, or nickel plating, and encouraging salts and metal deposits upon conductive frames such as used to create surfaces from wire meshes immersed in sea water.

Other embodiments of the technical material described in this application include corresponding systems and apparatus configured to include 4 circuits and a load; the first circuit being a pulse-by-pulse current control circuit and comprising at least one application specific integrated circuit configured to switch a first MOSFET on and off: the second circuit configured to signal the at least one application specific integrated circuit causing the first circuit to maintain an constant output voltage: the third circuit configured to provide a voltage reference: and the fourth circuit serving to provide feedback to the second circuit and the feedback based at least in part on a current flow in a second MOSFET.

These and other embodiments can each optional!} include one or more of the following features. The load can be a rechargeable batters, a collection of LEDs connected in series, a metal salt bath configured in a container to enable the plating of a metal onto the conductive surface of an item immersed w ithin the salt bath, and the like. The second circuit can be configured to signal the at least one application specific integrated circuit upon detecting a threshold level of voltage at a cathode of a diode. The third circuit can comprise a second MOSFET. an amplifier, and an application specific integrated circuit. In some implementations, the third circuit can have a resister that serves as a proxy for the load, enabling a reference voltage to be measured across the resister. Further.

In some implementations, the s\ stems and apparatus can contain a dimming circuit capable of prompting a decrease in a current applied to the load. In some of these implementations, the dimming circuit is part of the fourth circuit and interacts to with the third and second circuits.

Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. Implementations of the subject matter described can help a manufacture reduce the complexity of stocking LED light fixture drivers. Further implementations of the subject matter described can help a manufacture reduce the complexity in designing a family of light fixtures by standardizing the amount of space in the fixture that must be allocated to the driver. Also, implementations of the subject matter described can help a manufacture reduce costs associated with a family of light fixtures by enabling the manufacture to order larger batches of a common driver rather than multiple and smaller batches of differing drivers.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompany ing drawings and the description below.

Other features, aspects, and advantages of the subject matter v\ ill become apparent from the description, the draw ings. and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a logical representation of an adaptive voltage output control and diinmable circuit.

FIG.2 is a schematic of an example implementation of the first two control loops of an adaptive voltage output control and dimmable circuit.

FIG.3 is a schematic of an example implementation of the third and fourth control loops of an adaptive voltage output control and dimmable circuit.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

Before the present methods, implementations and systems are disclosed and described, it is to be understood that this invention is not limited to specific methods, specific components, implementation, or to particular compositions or configurations, and as such mav. of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations onlv and is not intended to be limiting.

As used in the specification and the claims, the singular forms "a," "an" and "the" include plural referents unless the context clearlv dictates otherwise. Ranges mav be expressed in ways including from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another implementation may include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, for example by use of the antecedent "about." it will be understood that the particular value forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint. and independently of the other endpoint.

"Optional" or "optionally" means that the subsequent!}, described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. Similarly, "typical^" or ^"typically^" means that the subsequently described event or circumstance occurs often although it may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

FIG. I is a logical representation 100 of an adaptive voltage output control (AVOC) and dimmable circuit I 10. The AVOC and dimmable circuit 110 can be explained as consisting of four control loops 120. 130. 140. and 150. The control loop 120 is a pulse-b) -pulse current control circuit comprising an Application Specific Integrated Circuit (ASIC) 112. a Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET) 114. a capacitor 116. and a resistor 118. The ASIC 112 has inputs of TA 122. AC 124. AC 126. VCC 128. GD 132. CS 134. and Gnd 136. The pulse-by-pulse current control is provided by the ASIC 112.

When the ASIC 112 turns on the MOSFET 114. current begins to flow from the capacitor 116. through the primary transformer 138. through the MOSFET 114 and through the resistor 118. The ASIC 112 measures the voltage drop across the resistor 118. The ASIC 112 shuts off the MOSFET 114 when the voltage drop across the resistor 118 reaches a predetermined level. As explained, this is a common and well understood method within the art to avoid saturation of the magnetic material of the transformer 138.

The ASIC 112 can be designed to operate at a variety of switching frequencies. For example. ASIC 112 can be designed to operate the MOSFET 114 at a nominal switching frequency of 100kHz. As designed, the switching of the MOSFET 114 will continue until either the continues until either the TA 122 is pulled high or a predetermined number of sw itching pulses have been completed. In one implementation, the TA 122 line can be pulled high by the action of an optcoupler 142. Note that the cycle will repeat every half-cycle of the Alternating Current supplied by lines 144 and 146.

The control loop 130 comprises a zener diode 148. a diode I 52. and the optocoupler 142. The control loop 130 monitors the output voltage of the converter at the cathode of diode 152 and through the optocoupler 1 2. prov ides a signal to the ASIC 112. The ASIC 112 interprets the supplied signal as a shutdown command of gate pulses from the ASIC 112 w hen the output voltage of the converter is at the designed predetermined level. In other words, the control loop 130 works to set a constant output voltage of the AC to DC converter portion of the circuit. In function, the ASIC 112 w orks to switch on and off the MOSFET 114 as long as the zener diode 148 does not conduct current. Upon conducting current, the optocoupler 1 2 then fires off pulling the TA 122 line high, turning the ASIC 112 off (stops the switching on and off of the MOSFET 114 by ASIC 112).

The control loop 140 comprises a MOSFET 154. an amplifier 156. an ASIC 162. and resistors 158. 168.170. The ASIC 162 functions to pro ide a precision reference and supplies a set point voltage for the amplifier 156. This loop functions to provide a constant current through the load 164 (portrayed as a string of LEDs). Note, while the load is portrayed as a sting of LEDs. the load can be any device or series of devices that require a constant load. For example, the load 164 could be a battery charger. The resistors 168 and 170 divide the voltage across them, proportionally to their respective resistance, enabling an accurate setting of the voltage applied to the amplifier 156. The voltage across resister 158. serving as a proxy for the load 164. modifies the error amplifier 156. enabling the MOSFET 154 to be driven at the desired level.

The control loop 150 comprises a zener diode 166. the optocoupler 142. a resistor

168. and the MOSFET 154. The control loop 150 provides dynamic voltage control (DVC ) to maintain voltages at predetermined level under a w ide range of values for the load 164. For example, w hen the voltage at the drain of the MOSFET 154 rises above the level set by the voltage characteristic of the zener diode 166. caused by maintaining a constant current through the load 164. the zener diode 166 conducts current. The current, the magnitude of which set by the resistor 168. causes the optocoupler 142 to turn on. This in turn causes the TA 132 line to raise to VCC. limiting the output voltage of the converter to a level such that current through the load 164 is limited to approximately 350 mA and that the voltage drop across the transistor 142 and the resistor 158 is at a predetermined value.

In operations, the control loop 150 generally works as follows: the circuitry to the gate of the MOSFET 1 4 varies or controls the voltage across the MOSFET 154. By varying the voltage across the MOSFTET 1 4. the difference from the constant voltage from the drive from the input, as supplied control loop 140. minus the voltage across the MOSFET 1 4 is the voltage across the load 164. The voltage across the load 164 determines the current through the load 164. By measuring the current through the load 164. the drive current of the MOSFET 154 can be altered accordingly, so that a constant current can be maintained through the load 164.

It should be noted that varying the set point of the current that is applied to the MOSFET 154 will thus vary the amount of current that will flow across the load 164. But this has the effect of varying the amount of voltage across the load 164. Reducing the voltage across the load 164 has the undesired effect of increasing the voltage dissipated across the MOSFET 1 4. Even though the current applied to the MOSFET 154 is reduced, the power across the MOSFET 154 thus increases.

To prevent the increase in power across the MOSFET 154. the circuit 110 in response to the increase in voltage across the MOSFET 154 varies the AC to DC converter (control loops 120 and 130) via control loop 150 to keep the voltage across the MOSFET 154 constant. In this way. the circuit 110 can be made to function like a dimmer and enable the diming of LEDs (the load 164). Alternative!}'. In effect, zener diode 166 serves the same purpose as zener diode 148 and w hen the zener diode 166 conducts current, the optocoupler 142 then fires off pulling the TA 122 line high, and turning the ASIC 112 off (stops the sw itching on and off of the MOSFET 114 by ASIC 112).

For example, consider a seven LED string as the load 164. the string requires a voltage of 21 VDC. ith each LED having a forward voltage of 3 VDC. Having the output voltage of the volt sensing, self-regulating and dimmable circuit 110 be two volts higher (e.g.23 VDC) leaves 2 VDC across the transistor 154 and resistor 158.

Configured for a typical LED drive current of 250 iiiA requires a dissipation of 700mW across the transistor 1 4 and resistor 158.

Shortening the string to 4 LEDs leads to a voltage drop across the transistor 154 and resistor 158 of 11 VDC (23 - (4 X 3)). This in turn, w ithout volt sensing and self- regulation, requires a dissipation of 3.850 mW. However, w ith volt sensing and self- regulation, the voltage output of the circuit is dynamically reduced to 13 VDC. reducing the dissipation across the transistor 154 and resistor 158 to 700m W.

FIG.2 is a schematic 200 of an exemplar implementation of the first two control loops of an adaptive voltage output control and dimmable circuit 110. FIG.2 is a more complete representation of the first control loop 120 and the second control loop 130 of the adaptive voltage output control (AVOC) and dimmable circuit 110 than is portrayed in the logical representation presented in FIG.1. As in FIG.1. the control loop 120 is a is a pulse-by-pulse current control circuit comprising an ASIC 212. a OSFET 214. a capacitor 216. and a resistor 218. The ASIC 212 has inputs of ^'FA 122. AC 124. AC 126. VCC 128. GD 132. CS 134. and Gnd 136.

As in FIG.1. the control loop 130 comprises a zener diode 148. a diode 152. and the optocoupler 142. The explanation for FIG.1 of the control loops 120 and 130 suffices.

FIG.3 is a schematic 300 of an example implementation of the third and fourth control loops of an adaptive voltage output control and dimmable circuit 110. FIG.3 is a more complete representation of the control loop 140 and the control loop 150 of the adaptive voltage output control (AVOC) and dimmable circuit 110 than is portrayed in the logical representation presented in FIG.1. As in FIG. 1. the control loop 140 comprises a MOSFET 154. an amplifier 156. an ASIC 162. and resistors 158. 168, 170.

As in FIG. 1. the control loop 150 comprises a zener diode 166. the optocoupler 142. a resistor 168. and the MOSFET 154. The explanation for FIG. 1 of the control loops 140 and 150 suffices.

While this specification contains

specific implementation details, these should not be construed as limitations on the scope of any inventions or of w hat may be claimed, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing ma be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products.

Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

Claims

What is claimed is:

1. A driver circuit (110) comprising::

a first circuit (120). the first circuit (120) being a pulse-by-pulse current control circuit, the first circuit (120) comprising:

at least one application specific integrated circuit (112). the at least one application specific integrated circuit configured to switch a first MOSFET (114) on and off:

a second circuit, the second circuit configured to signal the at least one application specific integrated circuit ( I 12) causing the first circuit ( 120) to maintain a constant output voltage;

a third circuit (140) configured to provide a voltage reference:

a fourth circuit (150). the fourth circuit serving to provide feedback to the second circuit (130) and the feedback based at least in part on a current flow in a second MOSFET (154): and

a load (164).

2. The driver circuit (110) of claim 1. wherein the load (164) is one or more light emitting diodes connected in series.

3. The driver circuit ( 110) of claim 1. wherein the load ( 164) is a rechargeable battery. 4. The driver circuitf 110) of claim 1. \\ herein the second circuit ( 130) is configured to signal the at least one application specific integrated circuit (112) upon detecting a threshold level of voltage at a cathode of a diode (152).

5. The driver circuit (110) of claim 1. wherein the third circuit (140) of the driver circuit comprises

the second MOSFET (1 4):

an amplifier ( 156): and

a second application specific integrated circuit (162).

6. The driver circuit (110) of claim 5. wherein the third circuit ( 140) has a resister ( 158) serving as a proxy for the load ( 164).

7. The driver circuit (110) of claim 3. wherein the second circuit (130) monitors the output voltage of a cathode of a diode ( 152).

8. The driver circuit (110) of claim 1. wherein the fourth circuit comprises:

a zener diode ( 166):

an optocoupler ( 1 2):

the second MOSFET(154).

9. The driver circuit ( 110) of claim 1. further comprising a dimming circuit (150), the dimming circuit capable of prompting a decrease in a current applied to the load (164).

10. A svstem of providing dimmable light from a series connected string of LEDs, the svstem comprising:

an AC power source ( 144. 146):

a load (164):

an adaptive voltage output control circuit (110). the adaptive voltage output control circuit (110) comprising:

at least one application specific integrated circuit (112). the at least one application specific integrated circuit (112) configured to switch a first MOSFET ( 114) on and off:

a second circuit ( 130). the second circuit ( 130) configured to signal the at least one application specific integrated circuit (112) causing the first circuit ( 120) to maintain an constant output voltage:

a third circuit (140) . the third circuit (140) configured to provide a voltage reference:

I 1 a fourth circuit (150). the fourth circuit ( 1 0) serving to provide feedback to the second circuit (130) and the feedback based at least in part on a current flow in a second MOSFET (154):

wherein the AC power source (144.146) supplies AC power to the adaptive voltage output control circuit (110) and the adaptive voltage output control circuit (110) supplies DC power to the load (164) at a predetermined voltage and current.

I I . The system of claim 10. wherein the load ( 164) is one or more light emitting diodes connected in series.

12. The system of claim 10. wherein the second circuit (130) of the adaptive voltage output control circuit ( 110) is configured to signal the at least one application specific integrated circuit (112) upon detecting a threshold level of voltage at a cathode of a diode (152).

13. The system of claim 10. wherein the adaptive voltage output control circuit (110) further comprises a dimming circuit (150). the dimming circuit (150) capable of prompting a decrease in a current applied to the load ( 164). 14. The system of claim 13. wherein the decrease in a current applied to the load (164) is not accompanied with an increase in a power dissipation required of the fourth circuit (150).