Hybrid switched capacitor circuit with automatic charge balancing

Abstract

An electronic module comprises an input capacitor (C3) connected between a first node and a second node (N1, N2); a first switch and a second switch (swH, swL) connected in series between said first node and said second node (N1, N2) and said second node (N2), in parallel with the input capacitor (C3), and defining at their interconnection an intermediate node (N3); a voltage regulator (VR) configured for receiving power from said input capacitor (C3) and for providing an output power at a configurable voltage (out) between an output node (N6) and said second node (N2). A multi-output power supply system comprising three such modules. An LED driver comprising such a module. A multi-color LED driver comprising three modules. A solid state lighting device comprising three modules and three LEDs. A display device.

Description

Technical Field

[0001] This invention generally relates to the field of power converter circuits and LED driver circuits, and more specifically to hybrid switched capacitor circuits (H-SCC) for driving at least three light-emitting diodes (LEDs), and to integrated chips (modules) for constructing multi-LED systems, and to multi-LED systems, methods for constructing multi-LED systems, and methods for powering multi-LED systems. Background of the Invention

[0003] DC-DC converters for generating output voltages higher or lower than the input voltage are known in the art. Examples include linear converters, buck converters, switched capacitor circuits (SCC), switched inductor circuits (SIC), and hybrid circuits using two or more of the above converters. Each of these circuits has advantages and disadvantages in terms of power efficiency, maximum power dissipation, level of integration (e.g., single chip, single package, PCB with multiple discrete components), maximum switching frequency, reliability, and modularity. DC-DC converters exist in many forms. It should be understood that DC-DC converters for high-power applications (e.g., for converting kilowatts or megawatts, such as those generated by wind turbines or solar panels) are entirely different from DC-DC converters for powering low-power devices from batteries. This invention primarily relates to the latter type, where the power consumption of each load to be powered is less than 25 watts.

[0004] The present invention also relates to light-emitting diodes, abbreviated as LEDs. Basic knowledge of LEDs is sufficient to understand the principles of the present invention. A good introduction to LEDs and LED drivers can be found in Chapter 2 of the main paper “Hybrid switched converters for CMOS integrated LED drivers” by Castellanos Rodriguez, JC (2018), Technische Universiteit Eindhoven, which is incorporated herein by reference in its entirety and referred to as [1] or “the paper”.

[0005] This paper also describes hybrid switched capacitor circuits for driving multi-LED systems. While these circuits are very promising, they still have some challenges, such as balancing the input voltages of different modules, and issues related to compactness, integration, and consequently cost. However, the solutions proposed in this invention are not limited to light-emitting devices but can also be used in other circuits that require the generation of multiple voltages.

[0006] There is always room for improvement or alternatives. Summary of the Invention

[0007] The purpose of embodiments of the present invention is to provide electronic circuits (also referred to herein as “modules”) as building blocks for multi-power supply systems (e.g., multi-voltage DC-DC converters) comprising at least three such modules.

[0008] Another objective of embodiments of the present invention is to provide a multi-power supply system.

[0009] The purpose of embodiments of the present invention is to provide a system comprising at least one module, or at least two modules, or at least three modules, wherein each module is capable of providing a configurable output voltage or output current.

[0010] The purpose of embodiments of the present invention is to provide a system in which the output voltage (or output current) of some or all of the modules can be configured individually and independently of other output voltages (or output currents).

[0011] The purpose of embodiments of the present invention is to provide a multi-LED driver circuit capable of driving at least two light-emitting diodes (LEDs), and / or which can be embedded in a single integrated circuit (e.g., a single semiconductor substrate), or which can be embedded in a single package (e.g., in the form of a packaged semiconductor device).

[0012] The purpose of embodiments of the present invention is to provide a multi-LED driver circuit capable of independently driving at least two light-emitting diodes (LEDs).

[0013] The purpose of embodiments of the present invention is to provide a multi-LED driver circuit capable of driving at least two light-emitting diodes (LEDs), the LEDs being configured to emit light of different colors or wavelengths.

[0014] The purpose of this invention is to provide a multi-LED driver circuit that can dim the light generated by an LED.

[0015] The purpose of embodiments of the present invention is to provide an electronic device comprising multiple LED driver circuitry and at least two light-emitting diodes (LEDs), for example, in the form of a single chip or in the form of a single package comprising one or more semiconductor dies.

[0016] The purpose of embodiments of the present invention is to provide a single chip or a single package comprising: a three-color LED driver circuit and three LEDs of different colors or different wavelengths.

[0017] The purpose of embodiments of the present invention is to provide modules (e.g., in the form of a single chip) for constructing such multi-LED driver circuits in a modular manner, for example by using three such modules and a small number of discrete components, such as at most two capacitors and three inductors and three LEDs.

[0018] The purpose of embodiments of the present invention is to provide such a multi-LED driver circuit and / or such a module, which is capable of driving the aforementioned multiple LEDs with, for example, at a high efficiency of at least 85%, at least 90%, at least 92%, or at least 94%.

[0019] The purpose of embodiments of the present invention is to provide modules in the form of a more compact single chip (i.e., semiconductor die).

[0020] The purpose of this invention is to provide a module implemented using standard CMOS technology (e.g., 0.18 micrometers).

[0021] The purpose of embodiments of the present invention is to provide a module configured to be powered by a voltage ranging from about 5.0V to about 7.0V.

[0022] The purpose of embodiments of the present invention is to provide a system configured to be powered by a DC power supply voltage in the range of about 7.5V to about 10V, or about 7.5V to about 24V, or about 7.5V to about 50V, or about 7.5V to about 200V.

[0023] According to a first aspect, the present invention provides an electronic circuit comprising: an input capacitor connected between a first node and a second node; a first switch and a second switch connected in series between the first node and the second node, connected in parallel with the input capacitor, and defining an intermediate node at their interconnection; and a voltage regulator configured to receive power from the input capacitor and to provide output power at a configurable voltage between an output node and the second node; wherein the first switch and the second switch are configured to be switched at a frequency of at least 2 MHz, or at least 3 MHz, or at least 4 MHz, or at least 5 MHz, or at least 6 MHz, or at least 7 MHz, or at least 8 MHz, or at least 9 MHz, or at least 10 MHz.

[0024] The advantage of this module is that it can be used to build LED driver circuits in various series and / or parallel configurations, where each individual LED can be controlled to any power level.

[0025] The main advantage of this module is that it allows for easy “automatic balancing” and thus enables cost-effective large-scale pixelation.

[0026] In one embodiment, the electronic circuit further includes an output capacitor connected between the output node and the second node, the output capacitor being used to stabilize the output voltage.

[0027] In one embodiment, the electronic circuit further includes a control unit configured to receive a switch control signal via a fourth node, and to generate a first switch signal to control a first switch, and to generate a second switch signal to control a second switch.

[0028] In one embodiment, the control unit includes a finite state machine and / or a level shifter.

[0029] In one embodiment, the electronic circuit further includes a fifth node for transmitting a switch control signal or a signal derived therefrom to another electronic circuit.

[0030] In one embodiment, the control unit is further configured to receive an output control signal via a fourth node and provide the output control signal or a signal derived therefrom to a voltage regulator to control a configurable voltage.

[0031] The control unit may include a serial interface for receiving the aforementioned output control signals, and may include a PWM generator for providing pulse width modulation signals to the voltage regulator or a digital-to-analog converter for providing analog voltage signals to the voltage regulator to control the output voltage to be generated.

[0032] In one embodiment, the electronic circuitry further includes a light-emitting diode connected to the output of the voltage regulator.

[0033] Advantageously, each LED is provided with its own driver and is fully or almost fully integrated (except for a few discrete components) in standard low-voltage and low-cost IC processes (such as standard CMOS processes).

[0034] In one embodiment, the voltage regulator is a linear voltage regulator.

[0035] In one embodiment, the voltage regulator is a switched inductor converter (SIC).

[0036] In one embodiment, the voltage regulator is a resonant switched capacitor converter or a hybrid switched capacitor converter.

[0037] In one embodiment, the voltage regulator is a resonant switched capacitor converter or a hybrid switched capacitor converter, which includes at least one capacitor and at least one inductor connected in series with the capacitor, wherein the capacitor has a value in the range of 400 pF to 1.4 nF; and wherein the inductor has a value in the range of 40 nH to 160 nH.

[0038] In one embodiment, the voltage regulator is a resonant switched capacitor converter or a hybrid switched capacitor converter comprising at least two switches, configured to switch at frequencies ranging from 20 MHz to 60 MHz.

[0039] According to a second aspect, the present invention also provides a system comprising: a first module, a second module, and a third module according to a first aspect, wherein a first node of the second module is connected to a second node of the first module, and wherein an intermediate node of the second module is connected to a second node of the third module; and wherein an intermediate node of the first module is connected to a first node of the third module; and wherein at least a first switch and a second switch of the first module and the second module are switched at a balanced frequency of at least 2 MHz in such a manner that: during a first time period, the first switch of the first module and the second module is configured to be closed, while the second switch of the first module and the second module is configured to be open, and during a second time period, the first switch of the first module and the second module is configured to be open, while the second switch of the first module and the second module is configured to be closed, thereby causing a charge distribution among the input capacitors of the first module, the second module, and the third module.

[0040] This embodiment can be considered a "power distribution system" capable of providing power at three different voltages. When used to drive LEDs, the circuit can be considered a "multi-LED driver".

[0041] The advantage of switching is that the power supply voltage applied to the first node of the first module is distributed substantially equally across the three modules. This technique is referred to herein as "automatic balancing" and is one of the fundamental principles of this invention.

[0042] One advantage is that the switching frequency is not important, as long as the switching frequency is high enough (e.g., at least 2MHz).

[0043] Another advantage is that the duty cycle of the signal supplied to the switch does not have to be 50%, but can be, for example, a value in the range of 10% to 40%.

[0044] In one embodiment, each module includes a light-emitting diode.

[0045] This embodiment is a "multi-LED system," for example, if the three LEDs are of different colors, it is a three-color LED system.

[0046] In a preferred embodiment, the system is integrated into a single package. This package may include three chips corresponding to the three modules, and only a small number of discrete components, such as two discrete capacitors (e.g., Figure 1a C1 and C2 in the middle) and optionally three inductors (e.g. Figure 6 Lx or Figure 8 Lx).

[0047] The advantage of this system is that the LED drivers are interconnected (e.g., stacked) in such a way that the available system power supply voltage is automatically and equally distributed across all modules or stacked chips or LEDs, even when using LEDs of different types or manufacturers, and even when the power of each LED is significantly different.

[0048] In one embodiment, the system further includes at least three discrete light-emitting diodes, each of which is connected to the output (N6) of a module.

[0049] This embodiment is a "multi-LED system," for example, if the three LEDs are of different colors, it is a three-color LED system.

[0050] In one embodiment, the system further includes a system controller configured to provide a switching control signal of at least 2 MHz to at least the first module and the second module.

[0051] In one embodiment, the system controller is further configured to provide a first output control signal to a first module, a second output control signal to a second module, and a third output control signal to a third module.

[0052] The output control signal can be a single digital bit stream containing at least three digital values ​​that define the outputs of the first module, the second module, and the third module.

[0053] According to a third aspect, the present invention also provides a method for constructing a solid-state light-emitting device, comprising the following steps: a) providing at least a first module, a second module, and a third module according to the first aspect; b) connecting a first node of the second module to a second node of the first module; c) connecting an intermediate node of the second module to a second node of the third module; d) connecting an intermediate node of the first module to a first node of the third module.

[0054] According to a fourth aspect, the present invention also provides a method for powering three light-emitting diodes using the system according to the second aspect, the method comprising the steps of: a) providing a power supply voltage at a first node of a first module and a second node of a second module; b) switching at least a first switch and a second switch of at least the first module and the second module at a balanced frequency of at least 2 MHz such that: during a first time period, the first switch of the first module and the second module is configured to be closed while the second switch of the first module and the second module is configured to be open, and during a second time period, the first switch of the first module and the second module is configured to be open while the second switch of the first module and the second module is configured to be closed; thereby causing a redistribution of charge among the input capacitors of the first module, the second module and the third module.

[0055] The power supply voltage (for a 3-module system) can be in the range of 6.0V to 10.0V.

[0056] According to a fifth aspect, the present invention also provides a display device comprising a plurality of pixels organized in rows and columns, the display device comprising a plurality of systems according to a second aspect, each system forming a pixel of the aforementioned display device.

[0057] These and other aspects of the invention will become apparent and elucidated with reference to the embodiments described below. Attached Figure Description

[0058] Figure 1(a) shows an illustrative block diagram of a multi-output power supply system having at least one “floating” output according to an embodiment of the present invention. Figure 1(b) shows the charge distribution during the first stage. Figure 1(c) shows the charge distribution during the second stage.

[0059] Figure 2 The simulation results of “voltage balance” for the circuit of Figure 1(a) with the first set of equal loads (5Ω / / 1μF) are shown when a 7.5V supply voltage is applied, a switching frequency of 20MHz and a duty cycle of approximately 25%. Figure 4(a) shows the voltages across the three input capacitors. Figure 4(b) shows the control signals applied to the switches.

[0060] Figure 3 The simulation results of “voltage balance” for the circuit of Figure 1(a) with three different loads (load 1 = 5Ω / / 1μF, load 2 = 10Ω / / 1μF, and load 3 = 15Ω / / 1μF) are shown when a 7.5V supply voltage is applied, a switching frequency of 2MHz (10 times lower than the module’s 20MHz switching frequency) and a duty cycle of about 25% are used.

[0061] Figure 3 (a) shows the voltage across the three input capacitors.

[0062] Figure 3 (b) shows the control signals applied to the voltage balancing switch (swnH, swnL, nε{1..3}).

[0063] Figure 4(a) illustrates an electronic circuit or module according to an embodiment of the present invention, wherein three are used in the multi-output power supply system of Figure 1(a).

[0064] Figure 4(b) shows a variation of the module of Figure 4(a) according to an embodiment of the present invention, which further includes a light-emitting diode (LED).

[0065] Figure 4(c) shows a variant of the module in Figure 4(a) according to an embodiment of the present invention, further including control circuitry.

[0066] Figure 4(d) shows a variant of the module of Figure 4(c) according to an embodiment of the present invention, which further includes a light-emitting diode (LED).

[0067] Figure 5(a) shows a block diagram of a multi-LED driver circuit according to an embodiment of the present invention, comprising three modules as shown in Figure 4(b), each module being connected to an LED.

[0068] Figure 5(b) shows a block diagram of a multi-LED driver circuit according to an embodiment of the present invention, comprising the three modules shown in Figure 4(d).

[0069] Figure 6 A simplified circuit diagram of the proposed switching inductor voltage regulator circuit, which can be used in the modules and multi-output power supply systems of Figures 1 through 5, is shown.

[0070] Figure 7 Showing the target Figure 6 The simulation results of the circuit.

[0071] Figure 8 It shows Figure 6 The voltage regulator circuit shown is a variant in which the tank circuit is tuned to a higher harmonic resonant frequency.

[0072] Figure 9 Showing the target Figure 8 The simulation results of the circuit.

[0073] The accompanying drawings are illustrative only and not restrictive. In the drawings, for illustrative purposes, some elements may be enlarged and not drawn to scale. Detailed Implementation

[0074] This invention relates to DC-DC converter circuits, and more specifically to hybrid switched capacitor circuits capable of powering at least two or at least three electrical loads. Providing a reliable circuit that is both compact and energy efficient is a challenge.

[0075] The present invention also relates to LED driver circuits and multi-LED driver circuits, as examples of such circuits, wherein the load is a light-emitting diode (LED). The LEDs should be individually dimmable to allow the generation of a variety of colors.

[0076] As described in the background section, the PhD thesis [1] describes various circuits and sub-circuits that can be used in such modules or systems. Chapter 6 of the thesis describes a multi-LED driver circuit consisting of multiple hybrid switched capacitor modules connected in parallel or in series. As stated in paragraph 6.3.2, balancing the different modules remains a technical challenge that has not been solved.

[0077] By using at least three modules with input capacitors and a first pair of switches to provide automatic balancing technology, the present invention provides a solution to this problem, which will be mainly shown in Figures 1 to 12. Figure 3 The module is shown in the diagram. It further includes a voltage regulator powered by an input capacitor. In principle, any type of voltage regulator can be used.

[0078] Figures 4 and 5 illustrate the modular approach proposed in this invention, which surprisingly facilitates the implementation of embodiments of the invention. Furthermore, this modular approach allows for a significant reduction in design and testing efforts.

[0079] In some embodiments of the invention, the voltage regulator is a switched inductor circuit (SIC) that includes a second pair of switches and a resonant circuit, for example, in... Figure 6 and Figure 7 The diagram is shown. In this case, a zero-current switching (ZCS) operating mode is preferably used. In a zero-current switch (ZCS), the switch is commutated at zero current. This soft-switching technology reduces switching losses in the switch and thus improves power efficiency.

[0080] The invention also provides embodiments in which the voltage regulator within the module is a switched inductor circuit (SIC) containing a resonant circuit configured to resonate at an integer multiple of the switching frequency of the second pair of switches (e.g., M = 3), for example, at... Figure 8 and Figure 9 It is shown in the middle.

[0081] Now refer to the attached diagram.

[0082] Figure 1(a) shows a simplified block diagram of the stacked or series connection of the three modules M1, M2, and M3 that form the multi-output power supply system 100.

[0083] In the example of Figure 1(a), the stack comprises three modules M1, M2, and M3, indicated by dashed lines. However, the invention is not limited to systems containing only three modules and will also apply to systems with more than three modules. Each module Mi has a voltage regulator VRi. In this example of Figure 1, each module also includes a load as part of the module, but this is not strictly necessary, and the load can also be external to the module. Figure 1aIn the example, each load is a capacitor connected in parallel with a resistor, but the invention is not limited thereto. In some embodiments of the invention, the resistor is replaced by a light-emitting diode (LED), as will be described further. The module can be implemented as a discrete 7V IC, meaning it is designed to be powered by a voltage of up to 7V.

[0084] Figures 1(a) to 1(c) The main purpose is to illustrate the principle of the "load balancing" proposed in this invention, which is achieved by adding three capacitors C1, C2, and C3 and at least two pairs of switches before the voltage regulators. Specifically, a first capacitor C1 and a first pair of switches sw1H and sw1L are added before the first voltage regulator VR1 of the first module M1; a second capacitor C2 and a second pair of switches sw2H and sw2L are added before the second regulator VR2 of the second module M2; and a third capacitor C3 is added before the third voltage regulator VR3 of the third module M3. It should be noted that the third module M3 may also have a pair of switches sw3H and sw3L, but these switches are not used in practice and can be omitted (e.g., in a dedicated implementation).

[0085] As shown in Figure 1(a), capacitors C1 and C2 of the first module M1 and the second module M2 are connected in series between the power supply voltage VCC and ground GND, while the terminal of capacitor C3 of the third module M3 is connected to node “y” defined by the interconnection of switches sw1H and sw1L of module M1 and node “z” defined by the interconnection of switches sw2H and sw2L of module M2.

[0086] According to an aspect of the invention, voltage balance across capacitors C1, C2, and C3 is achieved by switching the first module and the second modules M1 and M2 at a frequency of at least 10 MHz (e.g., at a frequency in the range of 10 MHz to 20 MHz, such as about 11 MHz, or about 12 MHz, or about 13 MHz, or about 14 MHz, or about 15 MHz, or about 16 MHz, or about 17 MHz, or about 18 MHz, or about 19 MHz). The switches need to be switched in the following manner:

[0087] i) During the first time period (or phase), the high-side switches sw1H and sw2H of the first module M1 and the second module M2 are closed, while the low-side switches sw1L and sw2L are open, as shown in Figure 1(b). It can be seen that in this configuration, the capacitor C3 of the third module M3 is connected in parallel to the capacitor C1.

[0088] ii) During the second time period (or phase), the high-side switches sw1H and sw2H of the first module M1 and the second module M2 are open, while the low-side switches sw1L and sw2L are closed, as shown in Figure 1(c). It can be seen that in this configuration, the capacitor C3 of the third module M3 is connected in parallel to the capacitor C2.

[0089] If the capacitance values ​​of C1, C2, and C3 are equal, this switching results in a redistribution of charge among the three capacitors C1, C2, and C3, such that the voltage across each of these capacitors is substantially equal. Preferably, the switching frequency of the input capacitors is high enough (e.g., at least 2 MHz, or at least 5 MHz, or at least 10 MHz) to limit or reduce losses caused by relatively large voltage imbalances.

[0090] Therefore, for example, if the power supply voltage Vcc equals 10V, the balancing scheme ensures that the voltage across C1, C2, and C3 is essentially equal to 10V / 2 = 5V. As another example, if the power supply voltage Vcc equals 7.5V, the balancing scheme ensures that the voltage across C1, C2, and C3 is essentially equal to 7.5V / 2 = 3.75V.

[0091] This can be understood as follows: Module M1, which generates "out1", presents an effective impedance "r1" across nodes "in" and "x", and is connected in series with module M2, which generates "out2". Module M2 itself presents an effective impedance "r2" across node "z" and ground. Therefore, the voltage across capacitors C1 and C2 stabilizes at Vcc.r2 / (r1+r2). When the power control on "out1" and "out3" is set to arbitrary values, the effective impedances "r1" and "r2" will not be equal, and the voltage at node "x" will be different from the expected 5V (50% of the 10V supply voltage) required for correct independent operation. By adding a third module M3 fed from capacitor C3, and by rapidly connecting C3 back and forth between nodes (in, x) and (x, ground), the voltage on C3 is forced to equal the voltage on C1, then the voltage on C2, then the voltage on C1 again, and so on. Finally, the three voltages must be equal. Since the sum of the voltages across C1 and C2 equals the supply voltage Vcc, which is 10V in this example, the voltages across the three modules M1, M2, and M3 stabilize at approximately 5V in steady state. By choosing a sufficiently high switching frequency (e.g., at least 10MHz) and by choosing sufficiently low capacitor impedances relative to r1 and r2, it can be ensured that the capacitors do not discharge significantly between the two switching phases. Note that the lower the voltage imbalance, the less energy is lost during capacitive charging / discharging.

[0092] For completeness, it can be seen that switches sw3H and sw3L of the third module M3 can be omitted, but in the modular approach, these switches will exist in each module. In one embodiment, both switches sw3H and sw3L can remain open at all times (which can reduce switching losses), but because the intermediate node of the third module M3 is not connected to any of the capacitors C1, C2, and C3, switches sw3H and sw3L can also be switched together with the switches of other modules.

[0093] Figure 2 The simulation results of “voltage balance” for the circuit of Figure 1(a) with a first set of equal loads (5Ω / / 1μF) are shown when a 7.5V supply voltage is applied, using a switching frequency of 2MHz for switches sw1H, sw1L, sw2H, sw1L and a duty cycle of approximately 25%. Input capacitors C1, C2, and C3 are 1μF. Figure 2 (a) shows the voltage across the three input capacitors. Figure 2 (b) shows the control signal applied to the switching switch. In this simulation, the voltage regulator block is switched at 20 MHz, as evidenced by the ripple on the output voltage.

[0094] like Figure 2 As shown, the voltage balancing works surprisingly well. The three output voltages (chosen here to be essentially equal to 2.5V) are balanced to their nominal values ​​within approximately 800ns. The maximum steady-state error between the outputs is approximately 45mV.

[0095] Figure 3 The simulation results of “voltage balance” for the circuit in Figure 1(a) are shown when a 7.5V supply voltage is applied, using a switching frequency of 2MHz for switches sw1H, sw1L, sw2H, and sw1L and a duty cycle of approximately 25%, for three different loads (load 1 = 5Ω / / 1μF, load 2 = 10Ω / / 1μF, and load 3 = 15Ω / / 1μF). Input capacitors C1, C2, and C3 are 1μF. Figure 3 (a) shows the voltage across the three input capacitors. Figure 3 (b) shows the control signal applied to the switch.

[0096] from Figure 3 As can be seen, even with a 3:1 load imbalance, voltage balancing still works surprisingly well. The three output voltages (again chosen to be essentially equal to 2.5V) are again balanced to their nominal values ​​within approximately 800ns. In this example, the final uncorrected voltage error is approximately 90mV. This error can be reduced by selecting larger input capacitors C1, C2, C3 and / or by increasing the switching frequency.

[0097] Because the parallel connection of capacitors (called "parallel capacitors") results in near-instantaneous charge balance, the duty cycle of the switching signal does not need to be 50%. In fact, the on-resistance of the switch and the time constant of the total capacitance determine the length of the minimum charging interval. Somewhat surprisingly, a duty cycle of approximately 10% seems to essentially minimize the output voltage difference. It can be found that the output voltage difference is negligible with a duty cycle of 25%.

[0098] From the above, it can be understood that the "automatic balancing principle" allows modules (e.g., chips) to be interconnected in such a way that the available system power supply voltage is automatically and evenly distributed across all modules (e.g., stacked chips) to power various loads (e.g., LEDs), even when using LEDs of different types or manufacture and / or when the power of each LED differs significantly. However, the invention is not limited to LEDs, and other loads (e.g., sensors, detectors, or converters) can also be used.

[0099] Preferably, the modules are manufactured using a low-voltage process, such as a 7V process. The scheme of Figure 1 also allows modules (e.g., stacked chips) to communicate directly via a wired bus (e.g., a serial bus) manufactured in the same 7V process.

[0100] Referring back to Figure 1(a), it can be understood that the balancing scheme will be used for various voltage regulators VR. In embodiments of the invention, modules M1, M2, and M3 include linear voltage regulators, or switched capacitor circuits (SCC), or switched inductor circuits (SIC), or any other suitable voltage regulator. Depending on the type of voltage regulator, different control signals will be applied to the control port “mod” of the voltage regulator. In the example of Figure 1(a), this control signal is represented as a DC voltage, which may be generated, for example, by a (local) digital-to-analog converter (DAC, not shown), but the invention is not limited thereto, and other control signals for controlling the voltage regulator to regulate the output voltage may also be used, such as pulse width modulation (PWM) signals (not shown). This analog voltage or PWM signal may be generated, for example, by the control circuit shown in Figure 4(c) or Figure 4(d). The control signal may be an analog circuit, or a digital circuit, or a hybrid circuit (having analog and digital parts), and may include, for example, a finite state machine (FSM). The actual “settings” or “configurations” or “commands” for the output power (or output voltage) of each module can, for example, come from a system controller outside the multi-power system, as shown in Figure 5(a) or Figure 5(b).

[0101] Referring again to Figure 1(a), it can be understood that the switches sw1H and sw1L of the first module M1 and the switches sw2H and sw2L of the second module M2 need to be switched synchronously. This can be achieved, for example, by providing a switch control signal to the second module M2 (e.g., via the aforementioned system controller), which is locally converted into two complementary signals for controlling local switches, and which are optionally daisy-chained to the first module M1 via the third module M3.

[0102] In the embodiment shown in Figure 1, a single control line is daisy-chained from module to module (e.g., from chip to chip). This line can (digitally) transmit different values ​​to each module. Alternatively, the line can provide a synchronization charge balance signal switched at a frequency below 25 MHz, for example, in the range of 2 MHz to 20 MHz, or in the range of 10 MHz to 20 MHz.

[0103] The modularity of the system in Figure 1(a) will be described in more detail next.

[0104] As described above, the multi-power supply system of Figure 1(a), or variations thereof, such as those shown in Figures 5(a) and 5(b), can be constructed using multiple modules M1, M2, and M3, each containing at least three identical modules. Although the block diagram of Figure 1(a) indicates that capacitors C1, C2, and C3 are located outside of modules M1, M2, and M3, the inventors recognize that the capacitors can actually be integrated into the modules themselves. This provides a significant advantage because it reduces the number of discrete components.

[0105] Figure 4(a) shows a block diagram of an exemplary "building block" or "module" proposed in this invention. This module is preferably implemented as a single chip with as few external components as possible. Module 410 includes:

[0106] - First node N1;

[0107] - Second node N2;

[0108] - Input capacitor C3 connected between nodes N1 and N2;

[0109] - The high-side switch swH and the low-side switch swL are connected in series between nodes N1 and N2, and an intermediate node N3 is defined between the two switches;

[0110] - Voltage regulator VR has an input port connected to node N1, a sink (or ground) port connected to node N2, a power output port "out" (node ​​N6), and a control input "mod";

[0111] - Optionally, an output capacitor C4 is connected between the output of the voltage regulator VR and node N2. Note that this output capacitor may be omitted depending on the load to be connected to the voltage regulator VR;

[0112] - A control voltage generator (schematically represented by circles with plus and minus signs), located inside the module, is used to control the voltage regulator VR of that particular module. The control voltage generator may, for example, include a digital-to-analog converter (not shown) connected to control logic (not shown). The signal generated by the control voltage generator may, for example, be set by an external processor (not shown);

[0113] As mentioned above, in principle, any type of voltage regulator can be used, such as a linear regulator, a switched inductor circuit (SIC), or a switched capacitor circuit (SCC). The advantage of a linear regulator is that it can be fully integrated on a semiconductor die (without external components), and its output voltage can be easily controlled using analog voltage; however, it has the disadvantage of not being optimal in power efficiency. The same advantages and disadvantages apply to switched capacitor circuits (SCC). However, in a preferred embodiment, the voltage regulator is a switched inductor circuit (SIC) with a relatively small inductance. Specific examples will be provided later. Figure 6 It is described in more detail in the middle.

[0114] Switches swH and swL are controlled by one or two control lines (not shown in detail, but schematically represented by dashed lines extending between nodes N4 and N5). Preferably, based on the switch control signals daisy-chained between different modules, individual control signals for each switch are generated within the module in a manner known per se in the art.

[0115] Figure 4(b) shows a block diagram of module 420, which is similar to module 410 in Figure 4(a), and the module further includes a light-emitting diode (LED), which is preferably integrated in the module or connected (e.g., soldered) to the module.

[0116] Figure 4(c) shows a block diagram of module 430, which can be considered a variant of module 410 of Figure 4(a). Module 430 further includes control circuitry (e.g., analog or digital or mixed analog and digital circuitry) configured to receive the aforementioned “switch control signal” and / or the aforementioned “output control signal”, and configured to provide a first signal to the high-side switch swH, a second signal to the low-side switch swL, a third signal to the voltage regulator, and a fourth signal to node N4.

[0117] Figure 4(d) shows a block diagram of module 440, which is similar to module 430 in Figure 4(c). Module 440 further includes a light-emitting diode (LED), which is preferably integrated into the module in the form of a semiconductor die or connected (e.g., soldered) to the module.

[0118] Figure 5(a) shows a block diagram of a multi-LED driver circuit 510, comprising three modules as shown in Figure 4(b), each module being arranged to connect to a corresponding LED. If LEDs are present, the circuit in Figure 5(a) within the dashed rectangle represents a solid-state lighting device, or a multi-LED system 510, such as a tri-color LED system. It can be seen that the input capacitor of the first module M1 is labeled "C1," and the input capacitor of the second module M2 is labeled "C2."

[0119] In one embodiment, the multi-LED system 510 includes three modules M1, M2, and M3 fully integrated on a single semiconductor die (therefore, the single die comprises three modules), which are connected to three discrete LEDs. The semiconductor die and the three LEDs are interconnected and packaged into a single package (i.e., a packaged assembly). As shown, this multi-LED system can be easily connected to a voltage source VCC and a system controller external to the multi-LED system. In such a system, the light output (intensity) and color can be set by the external system controller.

[0120] In this variant, the three modules, apart from the three inductors, are almost entirely integrated onto a single semiconductor die. These inductors can be implemented as discrete components or as conductive traces (e.g., copper traces) electrically connected to a substrate (e.g., a printed circuit board) on the single semiconductor die. The substrate with the inductors or with inductive traces can be packaged into a single package (i.e., a packaged component).

[0121] Figure 5(b) shows a block diagram of a multi-LED system according to an embodiment of the present invention, comprising the three modules shown in Figure 4(d). This system is a variation of the system shown in Figure 5(a), wherein the LEDs are integrated into the modules, for example, implemented on corresponding semiconductor dies that constitute the remainder of the modules.

[0122] In one embodiment, the multi-LED system 520 includes three modules M1, M2, and M3 that are fully integrated onto a single semiconductor die (therefore, a single die includes three modules). As shown, the multi-LED system can be easily connected to a voltage source VCC and a system controller external to the multi-LED system.

[0123] In this variant, the three modules, apart from the three inductors, are almost entirely integrated onto a single semiconductor die. These inductors can be implemented as discrete components or as conductive traces (e.g., copper traces) electrically connected to a substrate (e.g., a printed circuit board) of the single semiconductor die.

[0124] Therefore, Figure 5(b) shows a fully integrated on-chip or in-package LED driver with integrated inductors and capacitors using the H-SCC method (“integrated” means: embedded in a semiconductor substrate or packaged in a package).

[0125] Figure 6 A simplified circuit diagram of the proposed switched-inductor voltage regulator circuit, which can be used in the system described above, is shown. For clarity, the automatic balancing switch is not shown. Note that in a practical implementation, a transistor can be used to implement a diode; details are not shown here.

[0126] Capacitor C8 and inductor L1 connected in series with C8 form a tank circuit. The quality factor Qm of the tank circuit can be selected (during design) as a value in the range of approximately 0.33 to approximately 1.0. Based on the quality factor Qm, the values ​​of other components, such as... Figure 6 As shown.

[0127] Figure 6 The circuit is a resonant switched capacitor circuit (ReSC), which is similar to the resonant switched capacitor circuit presented in Figure 4.1 on page 60 of [1], but uses zero-current switching (ZCS) switches sw4 and sw5 at essentially the resonant frequency of the resonant slot. The switch duty cycle is kept constant. Note that the PWM circuit in this simulation is used to find the optimal value of the wrt circuit tolerance, but it can also be used as an “analog” controller.

[0128] Figure 6 The driver internally uses an automatic synchronous zero-current switch at frequencies greater than 25MHz. If the driver is used in module #i of the system, the output #i of the system can be controlled by fully turning the converter on or off over integer Ni clock cycles.

[0129] Since the switching frequencies of switches sw4 and sw5 are set to approximately 25 MHz in this example, very high-resolution dimming can be achieved by completely turning each LED on or off within an integer number of switching cycles. This has the added advantage that the driver efficiency is optimal across the entire power range and can be easily achieved even for much higher switching frequencies (e.g., up to 100 MHz). In addition to the on / off scheme, the LEDs can be fine-tuned within a limited range in an analog manner by varying the switching frequency. This does not degrade power efficiency when the switches are driven in a discontinuous ZCS mode, i.e., when the switching frequency is kept below the resonant frequency of the resonant slot.

[0130] For the sake of completeness, attention should be paid to Figure 6 The circuit shown differs primarily in topology from the circuit in the paper (Figure 4.1) in that the inductor is connected in series with the load, rather than with a capacitor. Furthermore, in that paper, a complex form of PWM is used to regulate the LED current, whereas in this invention… Figure 6 In the circuit, the voltage converter is always in ZCS, slightly in discontinuous mode (i.e., f sw (Below the resonant tank frequency) to further reduce inductor size and less rely on component tolerances. Furthermore, in Figure 6 In this approach, the output is preferably controlled by fully turning the converter on for multiple cycles and then turning it off for another cycle (“subharmonic PWM”). Its advantage is that it operates in a discontinuous mode and uses a switching control mode instead of attempting to regulate the current for each cycle (which is more complex).

[0131] Figure 7 The tank current (i.e., the current flowing through the tank) is shown. Figure 6 The current of the inductor Lx) and Figure 6 Simulation of the voltage of the proposed switching inductor circuit. Figure 7 The top trace of (a) shows an exemplary waveform of the current passing through the switch. Figure 7 The bottom trace of (c) indicates an expected efficiency of approximately 98.5%, assuming a 100mΩ switch. This is a major advantage of the circuit. Figure 7 The trace in (b) shows the voltage across capacitor C8 and the current flowing through inductor Lx as a function of time. It can be seen that the peak-to-peak voltage across capacitor C8 is approximately 9V, and the current is approximately 1200mA.

[0132] This operating mode allows for fine-tuning or regulation of the output voltage via the switching frequency rather than the duty cycle. With an LED load, only very small voltage and therefore frequency variations are required due to the exponential behavior of the current flowing through the LED relative to the voltage across it. For larger output power variations, it is recommended, for example, to disconnect the voltage regulator circuitry over an integer number of switching cycles by providing a logic '0' to the gates of both switches sw4 and sw5.

[0133] In addition to the high energy efficiency of this scheme Figure 6 Another major advantage of this voltage regulator is that the on-chip resonant capacitor Cs is only 444pF (for a resonant frequency of 20MHz and Qm=1), instead of the 7.75nF required in prior art circuits (at 18MHz), resulting in a 17-fold reduction in chip area (e.g., requiring only about 0.2mm²). 2 Assuming the technology provides 2.2 fF / μm 2 Instead of the 220nH external inductor required in the prior art circuit [1], the circuit proposed herein requires only an inductor with an Lx of 150nH. Such an inductor may be implemented as a discrete inductor (outside the semiconductor die), or an internal inductor (e.g., using parasitic junction line inductance), or as a copper trace in the form of a loop (also outside the semiconductor die), or in any other suitable manner.

[0134] Note that operating with Qm=1 means the voltage across the internal capacitor Cs can become 24Vpp (peak-to-peak). If Qm is chosen to be equal to 0.33, the peak-to-peak voltage across the internal capacitor Cs can be reduced to 7Vpp with a capacitance three times larger, Cs = 1.35nF (requiring approximately 0.6mm²). 2 At the cost of this, it has the advantage of having three times the inductance Lx = 50nH (smaller internal or external components).

[0135] However, this invention is not limited to Qm values ​​equal to 0.33 or 1.0, but those skilled in the art can select other Qm values ​​in the range of 0.33 to 1.0.

[0136] This type of voltage regulator, in the form of a resonant switched capacitor (ReSC) circuit, can be implemented as a single chip in CMOS technology, requiring only one external component, namely an inductor Lx, with a value ranging from about 50 nH to about 150 nH. However, as mentioned above, according to the technology, an internal bonding wire inductor can replace the external inductor, thereby reducing the number of external components.

[0137] Figure 8 It shows Figure 6The illustrated variant of the voltage regulator circuit shows the tank circuit tuned to a higher harmonic frequency, for example, the third harmonic frequency (M=3). When M=3, both the capacitor Cs and the inductor Lx are reduced by a factor of three, to Cs=150pF and Lx=50nH, respectively. However, the voltage across Cs will become 27Vpp, and may become even higher as the peak current increases to compensate for lower output power. Importantly, the reduced tank component values ​​make a very small and cost-effective IC possible. The downside is that a higher switching current is required for the same output power.

[0138] This voltage regulator, in the form of a resonant switched capacitor circuit (ReSC) operating at the third harmonic, can be implemented using CMOS or GaN technology, requiring only one external component, an inductor Lx, with a value of approximately 40 to 60 nH, for example, approximately 50 nH. Furthermore, depending on the technology, an internal junction line inductor can replace this external inductor.

[0139] A minor drawback of the switch-controlled mode is the higher current ripple, resulting in a larger output capacitor of about 100 nF, but this is still much smaller than the 10 μF output capacitor used in [1].

[0140] It should be noted that Figure 6 and Figure 8 The output of the resonant circuit can be fully turned on for a first predetermined time period (by switching the switches) or fully turned off for a second predetermined time period (by turning off both switches sw4 and sw5). These time periods can be counted as the entire number of oscillation cycles, thus allowing for a fully digital, high-resolution switching control scheme. This results in high energy efficiency (the ratio of light to power consumption). By selecting appropriate first and second predetermined time periods, any desired duty cycle can be generated, and therefore, the light intensity level can be generated. It should be noted that the duty cycle can be selected substantially independently of the switching frequencies of the balanced switches sw1H, sw1L, sw2H, and sw2L described in Figure 1(a). Furthermore, since the on and off periods can be arbitrarily distributed across the update cycle (“jitter”), visual aberrations can be reduced.

[0141] Figure 9 Show Figure 8 The behavior of the voltage regulator.

[0142] Figure 9 (a) shows a voltage swing from about +17.5V to about -7.5V, resulting in the aforementioned 27Vpp. Figure 9 (b) shows when using Figure 8 An example of light emission during circuitry. Figure 9 (c) shows the voltage regulator P. inThe instantaneous input power and instantaneous power efficiency η(eta) are both. Figure 9 (d) shows the voltage across the two regulator switches and the current through the two regulator switches, which is a measure of switching losses.

[0143] While the invention has been described with reference to specific embodiments, it is not limited thereto, and those skilled in the art will understand and implement other variations of the disclosed embodiments by studying the drawings, the disclosure and the appended claims when practicing the claimed invention.

[0144] For example, although most figures show three modules, each driving its own load, the invention is also applicable to systems with three modules but only two loads. In this case, the third module will not drive the load but will instead be used to balance the input voltage.

[0145] Although the three loads in one example are three resistors and in another example are three LEDs, the invention is not limited to the same type of load and can also be used to drive different types of loads, such as LEDs that emit visible light, UV LEDs, LiFi, radar or other detectors or sensors.

[0146] In some of the embodiments described above, the modules, particularly the voltage regulator, are described as being controlled via a wired connection; however, this is not always necessary, and the voltage regulator can also be controlled wirelessly. In this case, the control circuitry further includes transceiver circuitry (not shown), such as based on Bluetooth, ZigBee, or any other wireless communication standard.

[0147] In the above embodiment, the three modules are interconnected such that the power supply voltage is divided by 2. In this configuration, the input capacitors C1 and C2 of the first and second modules are connected in series, and the input capacitor C3 of the third module is alternately connected to the input capacitors of the first and second modules. However, the invention is not limited to a system with three modules, and a system according to the invention can also have more than three modules, such as five modules. In this case, the input capacitors of the three modules will be connected in series (first stage), and the input capacitors of the second stage modules will be configured to be alternately connected to two adjacent modules of the first stage. In particular, the input capacitor of the fourth module will be alternately connected to one of the two upper modules of the first stage, and the input capacitor of the fifth module will be alternately connected to the two lower modules of the first stage.

[0148] This principle is not limited to just 5 modules (3 in the first stage + 2 in the second stage), but can be extended to systems with a larger number of modules, such as 19 modules (in which case the power supply voltage will be divided by 10) or 39 modules (in which case the power supply voltage will be divided by 20). Typically, a system using this topology will have 2N-1 modules, that is, N modules in the first stage and (N-1) modules in the second stage. In this way, systems, such as solid-state lighting devices, can be formed that are powered by a single DC power supply with a voltage ranging from about 7.5 to 24V, or from 7.5V to about 50V, or from 7.5 to 200V, or from 7.5V to 400V, or from 7.5V to 600V, for example, for street lighting applications.

[0149] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. The fact that certain measures are recited in mutually different dependent claims does not mean that combinations of these measures cannot be used advantageously. Any reference numerals in the claims should not be construed as limiting their scope.

Claims

1. A circuit system, comprising: - a first module (M1), a second module (M2) and a third module (M3), each module comprising an electronic circuit, the electronic circuit comprising: - an input capacitor (C3) connected between a first node (N1) and a second node (N2); - a first switch (swH) and a second switch (swL) connected in series between the first node (N1) and the second node (N2), the first switch and the second switch being in parallel with the input capacitor (C3) and defining an intermediate node (N3) at their interconnection; - a voltage regulator (VR) configured for receiving power from the input capacitor (C3) and for providing output power at a configurable voltage (out) between an output node (N6) and the second node (N2); wherein the first node (N1) of the second module (M2) is connected to the second node (N2) of the first module (M1), and wherein the intermediate node (N3) of the second module (M2) is connected to the second node (N2) of the third module (M3); and wherein the intermediate node (N3) of the first module (M1) is connected to the first node (N1) of the third module (M3); and wherein the circuit system further comprises a system controller configured for providing at least the first module (M1) and the second module (M2) with a switching control signal of at least 2 MHz, wherein the first switch and the second switch of at least the first module and the second module are switched at a balancing frequency of at least 2 MHz in the following way: during a first time instant, the first switch (swH) of the first module (M1) and the second module (M2) is configured to be closed, while the second switch (swL) of the first module (M1) and the second module (M2) is configured to be open, and during a second time instant, the first switch (swH) of the first module (M1) and the second module (M2) is configured to be open, while the second switch (swL) of the first module (M1) and the second module (M2) is configured to be closed, thereby causing a charge distribution between the input capacitors of the first module, the second module and the third module.

2. The circuit system according to claim 1, wherein the electronic circuit further comprises an output capacitor (C4) connected between the output node (N6) and the second node (N2), the output capacitor for stabilizing the output voltage (out).

3. The circuit system according to claim 1 or 2, wherein the electronic circuit further comprises a control unit configured for receiving a switching control signal via a fourth node (N5) and for generating a first switching signal to control the first switch (swH) and for generating a second switching signal to control the second switch (swL).

4. The circuitry according to claim 3, wherein the control unit is further configured to receive an output control signal via a fourth node (N5) and for providing the output control signal or a signal derived from the output control signal to the voltage regulator (VR) for controlling the configurable voltage (out).

5. The circuitry according to any of claims 1, 2, 4, further comprising a light emitting diode (LED) connected at the output (N6) of the voltage regulator (VR).

6. The circuitry according to any of claims 1, 2, 4, wherein the voltage regulator (VR) is a linear voltage regulator; or wherein the voltage regulator (VR) is a switched inductor converter (SIC), or wherein the voltage regulator (VR) is a resonant switched capacitor converter or a hybrid switched capacitor converter.

7. The circuitry according to claim 6, wherein the voltage regulator (VR) is a resonant switched capacitor converter or a hybrid switched capacitor converter, the hybrid switched capacitor converter comprising at least one capacitor (Cs) and at least one inductor (Lx) connected in series with the capacitor (Cs), wherein the capacitor has a value in the range from 400 pF to 1.4 nF; wherein the inductor has a value in the range from 40 nH to 160 nH.

8. The circuitry according to claim 6, wherein the voltage regulator (VR) is a hybrid switched capacitor converter or a resonant switched capacitor converter comprising at least two switches (sw4, sw5) configured to switch at a frequency in the range from 20 MHz to 60 MHz.

9. The circuitry according to claim 8, wherein each module comprises a light emitting diode; or wherein the circuitry further comprises at least three discrete light emitting diodes, each connected to the output (N6) of one module.

10. The circuitry according to any of claims 1, 2, 4, 7-9, wherein the system controller is further configured for providing a first output control signal to the first module (M1) and a second output control signal to the second module and a third output control signal to the third module (M3).

11. A display device comprising a plurality of pixels organized in rows and columns, the display device comprising a plurality of the circuitry according to any of claims 1-10, each system forming one pixel of the display device.

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