Arrangement and method for delivering a current-controlled voltage

Abstract

An arrangement involving printed conductive traces includes at least a voltage source (V.sub.supply) and at least one target component, preferably a light-emitting component such as an LED. The arrangement is adapted to produce a current-controlled voltage (V.sub.OUT2, V.sub.out) originating from the voltage source, the current-controlled voltage being coupled to the at least one target component, wherein said voltage is dependent on the current (I.sub.R,LED, I.sub.LED) that is being passed through the target component and said voltage is adaptable to a varying resistance of the arrangement and its features.

Claims

1. An arrangement including printed conductive traces, the arrangement comprising: a first voltage source (V.sub.supply); a current sense amplifier configured to produce a first output voltage; at least one target component, the arrangement being configured to produce a current-controlled voltage (V.sub.OUT2, V.sub.out) originating from the first voltage source, the current-controlled voltage being coupled to the at least one target component, wherein said current-controlled voltage of the first voltage source is varied in response to a change in the first output voltage of the current sense amplifier, such that the current-controlled voltage is dependent on a current (I.sub.R,LED, I.sub.LED) that is being passed through the at least one target component; and at least one of each of a measuring circuit and a voltage regulation circuit, wherein the measuring circuit is configured to detect a current (I.sub.R,LED) that is at least indicative of the current being passed through the at least one target component, wherein the measuring circuit is additionally configured to control the voltage regulation circuit to produce a second output voltage (V.sub.OUT2) that is dependent on said detected current, the second output voltage (V.sub.OUT2) being the produced current-controlled voltage that is coupled to the target component, wherein the target component comprises at least one LED, wherein the measuring circuit comprises at least the current sense amplifier and a first resistor and the voltage regulation circuit comprises at least a first transistor and a voltage regulator, wherein the current sense amplifier is configured to detect a current passed through the first resistor, which is the current (I.sub.R,LED) that is at least indicative of the current being passed through the at least one target component, with the first output voltage (V.sub.OUT1) of the current sense amplifier being dependent on said detected current, said first output voltage controlling the first transistor by the first output voltage being lead to a base of the first transistor, and the first transistor controlling the second output voltage (V.sub.OUT2) of the voltage regulator by an impedance of the first transistor determining the second output voltage through adjusting an adjustment voltage (V.sub.adj) of the voltage regulator, the second output voltage being the produced current-controlled voltage that is coupled to the at least one target component.

2. The arrangement of claim 1, wherein the arrangement additionally comprises at least one transistor circuit, the transistor circuit comprising at least a second transistor, a third transistor, and a control voltage source (V.sub.MCU), wherein the arrangement is configured to control the second transistor with a voltage produced by the control voltage source being lead to a base of the second transistor, a collector current of the second transistor being passed to a base of the third transistor, an emitter of which is coupled to the first voltage source, while a collector of the third transistor is coupled to the at least one target component, and the current-controlled voltage (V.sub.out) is thus delivered to the at least one target component.

3. The arrangement of claim 1, wherein the arrangement is configured to adjust the produced current-controlled voltage in order to attain a target value of the current being passed through the at least one target component.

4. The arrangement of claim 1, wherein the arrangement is provided as or at least comprises an integrated system on a chip (SoC) or system on a package (SoP).

5. A method for delivering a current-controlled voltage to at least one target component, the method comprising at least the steps of: providing a target component, providing printed conductive traces, providing a first voltage source (V.sub.supply), providing a current sense amplifier configured to produce a first output voltage, producing a current-controlled voltage (V.sub.OUT2, V.sub.out) from the first voltage source, wherein the current-controlled voltage of the first voltage source is varied in response to a change in the first output voltage of the current sense amplifier, such that the current-controlled voltage is dependent on a current (I.sub.R,LED, I.sub.LED) that is being passed through the target component, coupling said current-controlled voltage to the target component, providing a measuring circuit and a voltage regulation circuit and detecting a current (I.sub.R,LED) with the measuring circuit, the current being at least indicative of the current that is being passed through the target component, wherein producing the current-controlled voltage comprises steps of: setting the first output voltage (V.sub.OUT1) according to said detected current, delivering said first output voltage to the voltage regulation circuit, setting a second output voltage (V.sub.OUT2) of the voltage regulation circuit according to said first output voltage, and coupling said second output voltage to the target component, wherein the target component comprises at least one LED, providing a first resistor to be comprised in the measurement circuit, providing the current sense amplifier to be comprised in the measurement circuit, providing a first transistor to be comprised in the voltage regulation circuit, providing a voltage regulator to be comprised in the voltage regulation circuit, wherein the detecting of the current is carried out through the first resistor and the current sense amplifier and the first output voltage is provided by the current sense amplifier, controlling the first transistor through the first output voltage, adjusting the adjustment voltage of the voltage regulator through the first transistor, and producing, with the voltage regulator, the second output voltage that is coupled to the target component, the second output voltage being dependent on the detected current.

6. The method of claim 5, wherein the method additionally comprises steps of: providing a second transistor, providing a third transistor, providing a control voltage source (V.sub.MCU), controlling the second transistor with a voltage produced by the control voltage source by leading the voltage to the base of the second transistor, passing a collector current of the second transistor to a base of the third transistor, coupling a collector of the third transistor to the target component, and coupling the first voltage source to an emitter of the third transistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

(2) FIG. 1 illustrates an exemplary arrangement according to one embodiment of the invention,

(3) FIG. 2 gives a second exemplary arrangement according to one other embodiment of the invention,

(4) FIG. 3 gives a third exemplary arrangement according to a further embodiment of the invention,

(5) FIG. 4 illustrates steps that may be performed in a method according to an embodiment of the invention,

(6) FIG. 5 gives further steps that may be performed in one other method according to an embodiment of the invention, and

(7) FIG. 6 gives further steps that may be performed in yet one other method according to an embodiment of the invention.

DETAILED DESCRIPTION

(8) In FIG. 1 an exemplary arrangement 100 is depicted. The conductive traces in embodiments of the arrangement 100, e.g. those depicted as lines in FIG. 1 that connect the various components comprised in an arrangement 100, may be printed traces comprising ink. Any of all of the traces in an arrangement 100 may be printed. For example, some of the traces may printed, while others are etched. A measurement circuit is configured to measure or detect a current and in FIG. 1, the measuring circuit comprises at least a first resistor 102 and a current sense amplifier 104. The first resistor R1 102 may be utilized as a current sense resistor to measure the current I.sub.R,LED passing through it, where the current I.sub.R,LED is the same current (or at least indicative of the current) that is passed through an LED 106. The component that the current I.sub.R,LED may pass through may also be any other current-operated device. The purpose of the arrangement 100 may be to deliver or produce an appropriate driving voltage to a target component, such as a radiation-emitting semiconductor element, e.g. LED, in order to have a desired current passing through the target component 106.

(9) An arrangement 100 also comprises a voltage source, here a first power supply V.sub.supply, that may be used to power the voltage regulation circuit and the target component 106. V.sub.supply may for instance be 12V.

(10) The current I.sub.R,LED may be measured by measuring a voltage drop across the resistor R1 102, which may be carried out through the current sense amplifier 104. The current sense amplifier 104 may, for instance, be a common-mode zero-drift topology current-sensing amplifier such as an INA199-Q1 available from Texas Instruments Incorporated. The voltage drop across the first resistor 102 may be measured by detecting the voltages V.sub.IN+ and V.sub.IN by the current sense amplifier 104.

(11) As may be comprehended by a skilled person, the current sense amplifier 104 may then produce a first output voltage V.sub.out1 which is dependent on the sensed voltage drop (i.e. current). Such as with typically employed measurement circuits of the kind discussed here and involving the aforementioned current sense amplifier, the measurement circuit may additionally comprise a bypass capacitor 108 and a second power supply V.sub.supply,2. The bypass capacitor may for instance have a capacitance of 100 nF and a second power supply V.sub.supply,2 may e.g. supply a voltage of 5V that is utilized to power the current sense amplifier 104. The current sense amplifier 104 which is used in the embodiment of FIG. 1 comprises also a reference pin REF, a ground pin GND, and supply voltage pin V+.

(12) This first output voltage V.sub.out1 may then be delivered to a voltage regulation circuit. In the embodiment of FIG. 1, a voltage regulation circuit comprises at least a first transistor 110 and a voltage regulator 112. The voltage V.sub.out1 may be delivered to the first transistor 110, which may be utilized to control the output voltage of the voltage regulator 112. The first transistor 110 may be a PNP bipolar silicon transistor such as BC857BLT1G and the voltage regulator 112 may be an adjustable low-dropout (LDO) regulator with a floating output, for example NCV317, both of which are available through Semiconductor Components Industries, LLC. The voltage regulator 112 may be powered by the voltage source V.sub.supply through the pin V.sub.IN. The output voltage of the linear regulator, the second output voltage V.sub.out2, will be dependent on the first output voltage V.sub.out1 and thus, dependent on the current I.sub.R,LED, as will be discussed below.

(13) The voltage regulation circuit may additionally comprise a second resistor R2 114 and a third resistor R3 116, an input capacitor 118, and an output capacitor 120. The second resistor R2 114 may be configured to limit the current to the base of the first transistor 110 in order to deliver a small current to the base of the first transistor 110 in order to deliver such a current that may be used to control the transistor 110, as may be appreciated by a skilled person.

(14) The third resistor R3 116, input capacitor 120, and output capacitor 122 may be comprised in a typical circuit configuration for an adjustable voltage regulator 112, the output voltage of which may be in a typical circuit controlled by the third resistor 116 and an adjustment resistor, which in such a typical circuit would reside in place of the transistor 110. An exemplary typical circuit involving a voltage regulator 112 may for instance be found in a datasheet for an NCV317 voltage regulator.

(15) The voltage regulator 112 may be configured to keep a fixed voltage, such as 1.25 V, between the second output voltage V.sub.OUT2 and the adjustment voltage V.sub.adj. In a conventional use scenario (not involving a transistor), the second output voltage V.sub.OUT2 may then be adjusted by adjusting the resistance of an adjustment resistor, for example by using a variable resistor.

(16) Cleverly, in the embodiment of FIG. 1, the adjustment voltage V.sub.adj and thus the second output voltage V.sub.OUT2 is altered, instead of using a variable resistor, by varying the impedance of the first transistor 110 through adjustment of its base current, which in turn is adjusted through V.sub.OUT1.

(17) If there is a need to increase the current to the target component 106, this may be achieved through increasing the second output voltage V.sub.OUT2. Thus, as can be comprehended from the above and FIG. 1, the current I.sub.R,LED that is passed through the target component 106 may be set to a desired value or kept at a constant value despite varying voltage losses occurring in the circuit.

(18) For instance, the current I.sub.R,LED may vary as the load or impedance of the circuit is changed. It may be understood that a variance occurring in the circuit materials may account for such a change and accordingly a change in the current. For example bending or stretching of materials comprised in the circuit may lead to said change in current. The change may be for instance gradual as the materials exhibit transformations progressively with use of the circuit.

(19) From the circuit configuration of FIG. 1 the following may be derived:
V.sub.OUT2.sub.VOUT2,VadjV.sub.eb,1=V.sub.qb,1,(1)

(20) where .sub.VOUT2,Vadj is the voltage between V.sub.OUT2 and V.sub.adj, which is here 1.25 V, V.sub.eb,1 is the voltage between the emitter and base of the first transistor 110 (a saturation voltage of 0.7 V is used in this example), and V.sub.qb,1 is the voltage between the collector and base of the first transistor 110,
(V.sub.OUT1V.sub.qb,1)/R2=I.sub.b,1,(2)

(21) where V.sub.OUT1V.sub.b,1 is the voltage difference between the first transistor 110 base and the first output voltage, R2 is the resistance of the second resistor 114, and I.sub.b,1 is the current passing through the base of the first transistor 110. In this example, the resistance R2 is chosen to be 110 k. Additionally,
(.sub.VOUT2,Vadj/R3)/H.sub.fe,1=I.sub.b,1,(3)

(22) where R3 is the resistance of the third resistor 116 (which is chosen as 124 ) and H.sub.fe,1 is the current-gain of the first transistor 110. From equation (1),
V.sub.OUT21.25V0.7V=V.sub.qb,1(4)
.fwdarw.V.sub.OUT2=V.sub.qb,1+1.95 V,(5)

(23) and from equation (2):
V.sub.qb,1=V.sub.OUT1+I.sub.b,1*100k(6)

(24) By combining (5) and (6) and inserting I.sub.b from (3):

(25) $\begin{array}{cc}{V}_{\mathrm{OUT}2}=V_{\mathrm{OUT}1}+100k*\left(\left(1.25V/124\right)/H_{\mathrm{fe},1}\right)+1.95V=V_{\mathrm{OUT}1}+1008/H_{\mathrm{fe},1}+1.95V& \left(7\right)\end{array}$

(26) The DC current gain of the first transistor 110 that has been mentioned here as BC857BLT1G by way of example, may in this case be taken as 200 A at 5V, giving:
V.sub.OUT2=V.sub.OUT1+5.04V+1.95V(8)
.fwdarw.V.sub.OUT2=V.sub.OUT1+6.99V.

(27) Thus, from (8) it can be seen that the second output voltage V.sub.OUT2 will, with the components that are utilized in this example, be dependent only on the first output voltage V.sub.OUT1 and, consequently, the detected current I.sub.R,LED. Using an exemplary value of 5V for V.sub.supply,2 here, in the case that the current I.sub.R,LED is at its maximum value, the first output voltage V.sub.OUT1 may be 5V, leading to V.sub.OUT2 reaching 11.99V. This is the theoretical maximum value for V.sub.OUT2, in practice V.sub.OUT2 may be smaller, as some voltage is converted to heat in the voltage regulator.

(28) In FIG. 2, a second arrangement 200 is given according to one other embodiment of the invention. Also here (as with all embodiments of this invention), any or all of the traces may be printed ink traces. The second arrangement 200 comprises a target component 106, which is an LED, a voltage source V.sub.supply, and a transistor circuit comprising a control voltage V.sub.MCU, a second transistor 224, a fourth resistor R4 226, and a third transistor 228.

(29) A control voltage V.sub.MCU may be delivered to the base of the second transistor 224, which may be may be an NPN bipolar silicon transistor such as BC846B. The control voltage V.sub.MCU may be set by a microcontroller unit (MCU). The control voltage V.sub.MCU may for example vary between 0V and 5V, and the control voltage may be set to a predetermined value.

(30) The collector current of the second transistor 224 is passed to the base of the third transistor 228, which may be an PNP bipolar power transistor MJD210. The collector side of the third transistor 228 may be coupled to the target component 106, while the emitter side of the third transistor 228 is coupled to the voltage source V.sub.IN.

(31) Thus, the current passing to the base of the third transistor 228 is constant, and a change in the current I.sub.LED (for instance through a change in the resistance of materials comprised in the circuit) will lead to a change in the voltage that is drawn from the voltage source V.sub.IN, which will then accordingly also change the voltage V.sub.out, which is the voltage that may drive the target component 106.

(32) The predetermined value of the control voltage along with the value of the fourth resistor 226 determine a maximum current that may be passed through the target component 106.

(33) From the circuit configuration of FIG. 2, it may be derived that the current I.sub.b,2 at the base of the second transistor 224 is
I.sub.b,2=(V.sub.MCUV.sub.bc,2)/R4,(9)

(34) where V.sub.bc,2 is the voltage between the base and collector of the second transistor 224, and R4 is the resistance of the fourth resistor. The current passing through the second transistor, I.sub.c,2, is
I.sub.c,2=I.sub.b,2*H.sub.fe,2,(10)

(35) where H.sub.fe,2 is the current-gain of the second transistor 224, while the base current I.sub.b,3 at the base of the third transistor 228 is
I.sub.b,3=I.sub.c,2.(11)

(36) The maximum current I.sub.LED,max that may be passed through the target component 106 is then
I.sub.LED,max=H.sub.fe,3*I.sub.b,3(12)

(37) Through combining (9), (10), (11), and (12):
I.sub.LED,max=H.sub.fe,3*H.sub.fe,2*(V.sub.MCUV V.sub.bc,2)/R4.(13)

(38) The voltage V.sub.out that is being delivered to the target component 106 is
V.sub.out=V.sub.f,LED*I.sub.LED,(14)

(39) where V.sub.f,LED is the forward voltage of the LED 106. Thus, there is produced a current-controlled voltage that is coupled to the target component 106.

(40) It may be noted that the embodiment of FIG. 2 may also be used for other purposes such as a high-side switch.

(41) In FIG. 3, a third arrangement 300 is given according to a further embodiment of the invention. The third arrangement 300 may constitute a combination embodiment that comprises at least parts of the arrangement 100 and the second arrangement 200 and at least some of the functionalities of both said arrangements. The third arrangement 300 of FIG. 3 comprises a measurement circuit and a voltage regulation circuit as disclosed in connection to the arrangement 100 of FIG. 1 and additionally a transistor circuit disclosed in connection to the second arrangement 200 of FIG. 2.

(42) The components and partial circuits in FIG. 3 function as disclosed previously, with the distinction that the measuring circuit now measures a current I.sub.R,LED that may not directly be the current that is passing through a target component 106, but is indicative of it. The voltage regulation circuit now produces a voltage V.sub.OUT2 that will act as a voltage source for the rest of the circuit that is essentially equivalent to the second arrangement 200 in FIG. 2. The partial circuit that corresponds to the second arrangement 200 may then be used to vary the voltage V.sub.OUT2 in order to for instance account for a change that may occur in the current I.sub.LED, which is the current that is being passed through a target component 106.

(43) Further embodiments may comprise a measuring circuit and voltage regulation circuit as disclosed above, and a plurality of transistor circuits that may each be coupled to a target component 106, the arrangement then comprising a plurality of target components 106. In these embodiments, the current I.sub.R,LED may be a current that is being passed to an LED matrix. Each of the LEDs in the matrix may then be associated with a transistor circuit each comprising a current I.sub.LED that may then be a current that is being passed through each of the target components 106, thus providing a method of fine-tuning the current through each target component 106. In an embodiment, the number of transistor circuits that may be used or required in connection with an LED matrix may depend, for instance, on the number of rows and/or columns that the LED matrix is configured to comprise.

(44) FIG. 4 illustrates steps that may be taken in a method according to the present invention. A (at least one) target component 106 is provided 402, printed conductive traces are provided 404, and a voltage source V.sub.supply is provided 406. At 408, a current-controlled voltage that is dependent on a current through the target component 106 is produced, while at 410, the produced current-controlled voltage is coupled to the target component 106.

(45) FIG. 5 shows further steps that may be taken in one other method according to an embodiment of the present invention. In 502 a measuring circuit and voltage regulation circuit are provided. Step 504 involves providing a first resistor 102 and current sense amplifier 104, which are to be comprised in the measuring circuit. Still at 504, a first transistor 110, such as a PNP transistor, and voltage regulator 112 are further provided and are to be comprised in the voltage regulator circuit. The steps of providing a target component 106, printed conductive traces, and a voltage source V.sub.supply are omitted in FIG. 5.

(46) At 506 a current is detected through utilizing the measuring circuit. A current I.sub.R,LED which is passed through the first resistor and may be passed through the target component 106 is detected with the current sense amplifier 104, after which a first output voltage of the measuring circuit (here the first output voltage V.sub.OUT1 of the current sense amplifier 104) is set according to the detected current in 508.

(47) At step 510, the first output voltage V.sub.OUT1 is delivered to the voltage regulation circuit. At 512, the delivered first output voltage is used to control the first transistor 110, while the first transistor 110 is used in 514 to adjust the adjustment voltage V.sub.adj of the voltage regulator 112. At 516, a second output voltage of the voltage regulation circuit (V.sub.OUT2 here in the exemplary embodiment, which will vary with V.sub.adj) is set (or produced) according to the first output voltage. As is easily comprehended by what is disclosed above relating to FIG. 1, this second output voltage will be dependent on the detected current and is thus the current-controlled voltage that is coupled to the target component 106.

(48) In FIG. 6, further steps that may be taken in yet one other embodiment of the invention are shown. A second transistor 224 such as a PNP transistor, third transistor 228 such as an NPN transistor, and control voltage source V.sub.MCU are provided 602 (in addition to providing a target component 106, printed conductive traces, and a voltage source V.sub.supply, which are omitted in FIG. 6). The second transistor 224 is controlled 604 with the control voltage source through the base of the second transistor. At 606, a current is passed from the collector of the second transistor 224 to the base of the third transistor 228. The collector of the third transistor 228 is coupled 608 to the target component 106, while at 610, the emitter of the third transistor 228 is coupled to the voltage source.

(49) The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of inventive thought and the following patent claims.

(50) The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated.