METHOD AND APPARATUSES FOR REGULATING THE OUTPUT VOLTAGE OF A VOLTAGE REGULATOR

Abstract

A method supplies a lighting device with electrical energy, wherein the lighting device includes at least two integrated circuits with at least one LED group by a current source associated with this LED group. The method includes generating a supply voltage by a voltage regulator, adjusting a LED group current passing the LED groups by one of the respective current sources, detecting the voltage drops across the current sources, selecting one voltage drop of each integrated circuit as a characteristic voltage drop, generating a control value of the respective integrated circuit, according to the characteristic voltage drop, reducing the control voltage when the control voltage is greater than a control value of the respective integrated circuit, and controlling the output voltage in accordance with the control voltage and/or in accordance with a control bus voltage derived from the control voltage.

Claims

1. A method for regulating an output voltage at an output of a voltage regulator for supplying a lighting device with electrical energy, wherein the lighting device comprises at least two integrated circuits, each integrated circuit comprises at least one LED group, wherein the lighting device is supplied with the electrical energy by a current source belonging to the LED group, the method comprising: generating an output voltage (V.sub.0) by the voltage regulator at the output; setting a LED group current respectively through each of the LED groups by the respective current source of each of the LED groups; detecting respective voltage drops across the respective current sources of each of the respective LED groups as the respective voltage drop value of these respective current sources within the respective integrated circuit; selecting a respective voltage drop value of one of the current sources of each integrated circuit from the voltage drop values of the current sources of this respective integrated circuit (IC1, IC2) as a characteristic voltage drop value of the integrated circuit (IC1, IC2) and generating a control value signal at a node of the respective integrated circuit (IC1, IC2) corresponding to the characteristic voltage drop value of the respective integrated circuit (IC1, IC2); reducing an amount of a control voltage by the respective integrated circuit (IC1, IC2) if the amount of the control voltage is greater than an amount of the control value signal at the node of the respective integrated circuit (IC1, IC2); and regulating the output voltage of the voltage regulator at the output as a function of the control voltage and/or a control bus voltage derived from the control voltage.

2. A device for supplying at least two LED groups with electrical energy comprising: a voltage regulator, at least two integrated circuits, and a control bus, wherein each of the integrated circuits has at least one LED connection for at least one LED group, and each of the integrated circuits has at least one LED driver per LED group for the energy supply of the LED group via the LED connection associated with one of these LED groups, and each of the integrated circuits (IC1, IC2) has at least one measuring device of the integrated circuit (IC1, IC2) for detecting voltage differences between potentials of the LED connections of the integrated circuit (IC1, IC2) and a reference potential, and each of the integrated circuits comprises a local controller, wherein the local controller selects a voltage drop value as a characteristic voltage drop value of the integrated circuit out of the voltage drop values of the current sources of the respective integrated circuit detected by its measuring device, and wherein the local controller generates a control value signal at a node of the integrated circuit according to the characteristic voltage drop value of the integrated circuit, and wherein the local controller reduces an amount of a control voltage with the use of a transistor if the amount of the control voltage is greater than an amount of the control value signal of the relevant integrated circuit at the node of the integrated circuit, and the output voltage of the voltage regulator depends on the control voltage or a control bus voltage derived from the control voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] FIG. 1 shows an exemplary device for regulating a voltage regulator for supplying at least two LED groups.

[0074] FIG. 2 shows an exemplary device for regulating a voltage regulator for supplying at least two LED groups, including a filter for PWM modulation on the control bus (RB)

DESCRIPTION

[0075] FIG. 1 shows an exemplary device according to the preceding description. The device is supplied with energy via a supply voltage connection (VS) and the reference potential (GND). The voltage regulator (VREG) is connected to the supply voltage connection (VS) via its voltage input (VIN). At the voltage regulator output (V.sub.out) the voltage regulator (VREG) supplies an output voltage (V.sub.0) against the reference potential (GND). For a better overview the exemplary integrated circuit in FIG. 1 comprises only a first integrated circuit (IC1) and a second integrated circuit (IC2).

[0076] The first integrated circuit (IC1) receives electrical current out of the voltage regulator output (V.sub.out) via a first LED driver (LED-DRV) and a first LED group (LED.sub.1a) and via another LED driver (LED-DRV) and another first LED group (LED.sub.1b).

[0077] The second integrated circuit (IC2) also receives electrical current from the voltage regulator output (V.sub.out) of the voltage regulator (VREG) via a second LED driver (LED-DRV) and a second LED group (LED.sub.2). As described, the LED drivers (LED-DRV) are typically power sources.

[0078] A first analog-to-digital converter (ADC) of the first integrated circuit (IC1) detects the voltage drops across the LED drivers of the first integrated circuit (IC1). A first controller (RA) of the first integrated circuit (IC1) uses these measured values measured by the first analog-to-digital converter (ADC) of the first integrated circuit (IC1) to generate a first control value signal at the first node (K1). A first differential amplifier (OP1) of the first integrated circuit (IC1) compares the potential of this first node (K1) and thus the value of the first control value signal with the potential on the control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4). If the potential on the control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4) is higher than the potential of the first control value signal at the first node (K1), the first differential amplifier (OP1) reduces the potential of this control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4) via the first transistor (T1). In order to do so, the first differential amplifier (OP1) opens the first transistor (T1), so electrical current can pass from the control bus (RB) to the reference potential (GND). The output voltage of the first differential amplifier (OP1) can be understood as the first reference voltage of a voltage-dependent transistor current source that is formed by the first transistor (T1).

[0079] A second analog-to-digital converter (ADC) of the second integrated circuit (IC2) detects the voltage drops across the LED drivers of the second integrated circuit (IC2). Using these values measured by the analog-to-digital converter (ADC) a second regulator (RA) of the second integrated circuit (IC2) generates a second control value signal at the second node (K2). A second differential amplifier (OP2) of the second integrated circuit (IC2) compares the potential of this second node (K2), and thus the value of the second control value signal, with the potential on the control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4). If the potential on the control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4) is higher than the potential of the second control value signal at the second node (K2), the second differential amplifier (OP2) uses the second transistor (T2) to reduce the potential of this control bus (RB) in the form of the control voltage (V.sub.R) at the fourth resistor (R4). In order to do so, the second differential amplifier (OP2) opens the second transistor (T2), so electrical current can pass from the control bus (RB) to the reference potential (GND). The output voltage of the second differential amplifier (OP2) can be used as a second reference voltage of a voltage-dependent transistor current source, which is formed by the second transistor (T2).

[0080] If the amount of the control voltage (V.sub.R) at the fourth resistor (R4) is equal to or lower than the potential of the second control value signal at the second node (K2), the second differential amplifier (OP2) closes the second transistor (T2), so a larger proportion of the constant current (I.sub.bias) of the bias current sources (IQ) of the integrated circuit (IC1, IC2) passes through the fourth resistor (R4) and thus increases the control voltage (V.sub.R) across the fourth resistor (R4). However, this only works if in another circuit the amount of the control voltage (VR) at the fourth resistor (R4) is smaller than the potential of the control value signal of this other integrated circuit at its node.

[0081] In this construction, the absolute lowest control value signal, i.e., the integrated circuit of the integrated circuits (IC1, IC2) with the lowest potential at its respective node (K1 to Kn), always determines the control voltage (V.sub.R) at the fourth resistor (R4) and thus the control bus voltage (V.sub.RB).

[0082] Via the control method the individual integrated circuits (IC1, IC2) can be excluded via switches (SW1, SW2) by means of external data bus commands via a not shown communication bus, which preferably connects all integrated circuits (IC1, IC2), or the individual integrated circuits (IC1, IC2) exclude themselves via the switches (SW1, SW2) from the control method. This is necessary if none of the LED groups (LED.sub.1a, LED.sub.1b, LED.sub.2) of the integrated circuit in question is operated.

[0083] Constant current sources (IQ), which are each part of the integrated circuits (IC1, IC2), feed a constant current (I.sub.bias) into the control bus (RB). The total current of the respective constant currents fed in by the integrated circuits (IC1, IC2) drops across the fourth resistor (R4) as a control voltage (V.sub.R) if the total current is not derived, typically partially derived, via one or more of the transistors (T1, T2) within the integrated circuits (IC1, IC2) against the reference potential (GND).

[0084] In the example of FIG. 1, the voltage signal on the control bus (RB), i.e., the control voltage (VR), is filtered to control bus voltage (V.sub.RB) by an exemplary low pass consisting of a filter capacitance (Cf) and a Filter resistance (Rf)

[0085] A voltage-to-current converter (VC-C), consisting of a third resistor (R3), a zeroth transistor (T0) and a zeroth differential amplifier (OP0), converts the control bus voltage (V.sub.RB) into an additional current (I.sub.ADJ) of a voltage control signal (VCTR). This additional current (I.sub.ADJ) passes the first resistor (R1) of the feedback voltage divider (R1, R2) of the voltage regulator (VREG) and thus warps the control input (ADJ) of the voltage regulator (VREG) in dependence of the control bus voltage (V.sub.RB) and thus from the control voltage (V.sub.R).

[0086] FIG. 2 shows an exemplary device according to the preceding description and FIG. 1. In contrast to FIG. 1, the integrated circuits (IC1, IC2) of FIG. 2 are provided with a filter (F) in order to perform PWM modulation on the control bus (RB).

[0087] A device according the disclosure allows a regulation of the voltage regulator (VREG) in a simple manner in order to supply more complex LED arrangements supplied with electrical energy from several integrated circuits. According to the disclosure, it was recognized that this is particularly easy with a current-controlled voltage regulator. Here, the total current (I.sub.s) through the fourth resistor (R4) is the actual value signal and the input of the voltage-to-current converter (VC-C) is the exemplary input of a current controlled voltage regulator advanced by a said component (VREG, RI, R2, VC-C). In contrast to the state of the art, the construction is particularly robust against EMC radiation and potential offset due to the current-controlled signal.

LIST OF ABBREVIATIONS (Not in the Figures)

[0088] IC3 third integrated circuit [0089] IC4 fourth integrated circuit [0090] ICn n-th integrated circuit [0091] I.sub.s total current of the fed-in bias currents (I.sub.bias) of all integrated circuits (IC1 to ICn) connected with the standard bus (RB) [0092] K3 third node within the third integrated circuit (IC3) [0093] The potential difference between the third node and the reference potential (GND) represents the reference voltage for the third transistor (T3) of the third integrated circuit (IC3), which sets the current through the third transistor (T3) of the third integrated circuit (IC3). [0094] K4 fourth node within the fourth integrated circuit (IC4) [0095] The potential difference between the fourth node and the reference potential (GND) represents the reference voltage for the fourth transistor (T4) of the fourth integrated circuit (IC4), which sets the current through the fourth transistor (T4) of the fourth integrated circuit (IC4). [0096] Kn n-th node within the n-th integrated circuit (ICn) [0097] The potential difference between the n-th node and the reference potential (GND) represents the reference voltage for the n-th transistor (Tn) of the n-th integrated circuit (ICn), which sets the current through the n-th transistor (Tn) of the n-th integrated circuit (ICn). [0098] LED3 third group of LEDs whose current is regulated by the third integrated circuit (IC3) [0099] LED4 fourth LED group whose current is regulated by the fourth integrated circuit (IC4) [0100] LED.sub.n n-th LED=n-th LED group whose the current is regulated by the n-th integrated circuit (ICn) [0101] OP3 third differential amplifier of the third integrated circuit (IC3) [0102] OP4 fourth differential amplifier of the fourth integrated circuit (IC4) [0103] OPn n-th differential amplifier of the n-th integrated circuit (ICn) [0104] T3 third transistor of the third integrated circuit (IC3) [0105] T4 fourth transistor of the fourth integrated circuit (IC4) [0106] Tn n-th transistor of the n-th integrated circuit (ICn)

LIST OF ELEMENT REFERENCES

[0107] ADC analog-to-digital converter, also known as measuring equipment [0108] ADJ Control input of the voltage regulator (VREG) for the voltage control signal (VCTR) [0109] Cf filter capacity [0110] F filter [0111] GND reference potential [0112] I.sub.ADJ additional current [0113] I.sub.Bias Constant current of the respective bias current source (IQ), which is supplied via the control bus connection of the respective integrated circuit (IC1, IC2) is fed into the control bus (RB). The bias current is preferably a current that is constant over time for setting the operating point of the proposed device. [0114] IC1 first integrated circuit [0115] IC2 second integrated circuit [0116] IQ constant current source of an integrated circuit of the integrated circuits (IC1, IC2 to ICn) [0117] I.sub.LED1a Current through the first LED (LED.sub.1a) of the first LED group (LED.sub.1) [0118] I.sub.LED1b Current through the second LED (LED.sub.1b) of the first LED group (LED.sub.1) [0119] I.sub.LED2 Current through the first LED (LED.sub.2a) and the second LED (LED.sub.2b) of the second LED group (LED.sub.2) [0120] K1 first node within the first integrated circuit (IC1) [0121] The potential difference between the first node (K1) and the reference potential (GND) represents the reference voltage for the first transistor (T1) of the first integrated circuit (IC1), which sets the current through the first transistor (T1) of the first integrated circuit (IC1). [0122] K2 second node within the second integrated circuit (IC2) [0123] The potential difference between the second node (K2) and the reference potential (GND) represents the reference voltage for the second transistor (T2) of the second integrated circuit (IC2), which sets the current through the second transistor (T2) of the second integrated circuit (IC2). [0124] LED.sub.1 first group of LEDs whose current is regulated by the first integrated circuit (IC1) [0125] LED.sub.1a first LED of the first LED group (LED.sub.1) [0126] LED.sub.1b second LED of the first LED group (LED.sub.1) [0127] LED.sub.2 second group of LEDs whose current is regulated by the second integrated circuit (IC2) [0128] LED.sub.2a first LED of the second LED group (LED.sub.2) [0129] LED.sub.2B second LED of the second LED group (LED.sub.2) [0130] LED0 first LED connection of an integrated circuit [0131] LED1 second LED connection of an integrated circuit [0132] LED DRV LED integrated circuit driver of the integrated circuits (IC1, IC2 to ICn) [0133] OP0 zeroth differential amplifier [0134] OP1 first differential amplifier of the first integrated circuit (IC1) [0135] OP2 second differential amplifier of the second integrated circuit (IC2) [0136] R1 first resistance [0137] R2 second resistance [0138] R3 third resistor [0139] R4 fourth resistor [0140] RA controller of the respective integrated circuit [0141] RB control bus [0142] Ri internal control signal of the respective integrated circuit [0143] Rf resistance of filter (F) [0144] SW1 switch of the first integrated circuit (IC1) [0145] SW2 switch of the second integrated circuit (IC2) [0146] T0 zeroth transistor [0147] T1 first transistor of the first integrated circuit (IC1) [0148] T2 second transistor of the second integrated circuit (IC2) [0149] V.sub.0 Output voltage of the voltage regulator (VREG) at his voltage regulator output (V.sub.out) against the reference potential (GND) [0150] V.sub.ADJ Voltage value of the voltage control signal (VCTR) against a reference potential (GND) [0151] VC-C voltage-to-current converter (external voltage to current converter), which is preferably not part of the integrated circuits (IC1, IC2) and/or the voltage regulator (VREG) and which can consist, for example, of a zeroth transistor (T0), an amplifier (OP0) and a third resistor (R3). [0152] VCTR voltage control signal [0153] VIN voltage input of the voltage regulator (VREG) [0154] V.sub.out voltage regulator output of the voltage regulator (VREG) [0155] V.sub.R Control voltage at the fourth resistor (R4) [0156] V.sub.RB control bus voltage [0157] VREG voltage regulator [0158] VS Supply voltage connection of the voltage regulator (VREG) LIST OF REFERENCED CITED [0159] DE 10318780 A1 [0160] DE 102005028403 B4 [0161] DE 102006055312 A1 [0162] EP 1499165 B1 [0163] EP 600695 B1 [0164] U.S. Pat. No. 7,157,866 B2 [0165] U.S. Pat. No. 83,194,49 B2 [0166] U.S. Pat. No. 8,519,632 B2 [0167] US 2007/0139317 A1 [0168] US 2008/0122383 A1 [0169] US 2009/0230874 A1 [0170] US 2010/0026209 A1 [0171] US 2010/0201278 A1 [0172] US 2011/0012521 A1 [0173] US 2011/0043114 A1 [0174] US 2012/0268012 A1 [0175] WO 2013/030047 A1