Flexible DC-DC converter

Abstract

A driver circuit (110) configured to provide output power (PWR) at a plurality of outputs to drive a plurality of light emitting diodes (30, 200) includes a power input port, at least one digital input port, a decoder, and one or more DC-DC power converters. The driver circuit further includes a first power controller circuit, a second power controller circuit, and an internal power bus (INTP) to provide an input to the DC-DC power converter. The light emitting diodes (30, 200) are conveniently driven to display an animation.

Description

TECHNICAL FIELD

[0001] The inventive concept described herein relates generally to the field of electronic circuit arrangements for operating light sources. More specifically, the embodiments described herein relate to the design of DC-DC converters for driving LEDs, in particular arrays of LEDs. BACKGROUND

[0002] For proper operation, LED lighting systems need to be driven correctly. The forward voltage of an LED varies inversely with temperature, resulting in an LED trying to draw more current as the temperature rises. This can result in thermal runaway and damage to the LED. Therefore, the proper amount of power needs to be provided in the form of a precise balance of current and voltage. Different types of LEDs or different configurations of groups or arrays of LEDs require different types of drivers to provide the correct balance of voltage and current to provide the power.

[0003] Therefore, drivers exist in the form of constant current LED drivers, while other drivers are constant voltage LED drivers. The system designer has to choose which of these two types of drivers is most suitable for their LED lighting system or LED display. For example, in a system where LEDs are connected in series, it is advantageous to use constant current LED drivers, while for a system where LEDs or groups of LEDs are mostly connected in parallel to each other, it is advantageous to use constant voltage LED drivers.

[0004] LED drivers usually have one or more microcontrollers to facilitate control of the output. The advantage of using a microcontroller is that it provides flexibility and ease of programming. However, the inclusion of a microcontroller in the driver can have a significant impact on the cost of the driver. Furthermore, when a microcontroller is used, the debugging of the driver application program can become complex and the application program can be vulnerable to hacking by unscrupulous third parties. Therefore, it is an object of the present invention to produce a cost-effective, flexible and reliable LED driver. SUMMARY

[0005] There is a need for a cost-effective, flexible, reliable, configurable DC-DC converter for providing power and control signals to an LED driver to drive a plurality of LEDs, preferably in an array or similar configuration to allow LED animations to be implemented.

[0006] To this end, according to one aspect, a driver circuit is disclosed, the driver circuit being configured to provide output power at a plurality of power output terminals to drive a plurality of light emitting diodes, the driver circuit comprising: a power input port for receiving input power and converting to provide the output power; at least one digital input port for receiving digital commands and / or communication signals for controlling the driving of the plurality of light emitting diodes; a decoder configured to receive and decode digital commands and / or communication signals from the digital input port to provide an internal command bus comprising one or more digital command lines; one or more DC-DC power converters configured to provide power via at least one of the plurality of power outputs of the driver circuit at substantially constant current; one or more DC-DC power converters configured to provide power via at least one remaining one of the plurality of power outputs of the driver circuit at substantially constant voltage; characterized in that the driver circuit further comprises: a first power controller circuit configured to receive a digital power input, the value of the digital power input being dependent on the level of input power received at the power input port; and to provide a first internal multipurpose input / output bus for conveying a first internal multipurpose bus encoding value dependent on the state of the internal command bus and the value of the digital power input; a second power controller circuit configured to provide a second internal multipurpose input / output bus for conveying a second internal multipurpose bus encoding value dependent on the state of the internal command bus; and an internal power supply bus for providing input to the DC-DC power converters.

[0007] The power input received at the power input port can be from a battery or other suitable power source. The power input can be a voltage source or a current source, i.e. it can be from a power source capable of providing a substantially constant voltage or a substantially constant current. According to a preferred embodiment, when used in automotive applications, the power input can be from an automotive battery. The control input can be from a CAN bus.

[0008] Although there is a trend towards the widespread use of microcontrollers, it can be advantageous to dispense with the use of microcontrollers and instead provide a robust and cost-effective solution tailored to a specific use, as discussed in the present disclosure. Embodiments of the invention allow for faster execution of instructions compared to known drivers which require interpretation of instructions by a general purpose microcontroller or the like. BRIEF DESCRIPTION OF DRAWINGS

[0009] The inventive concepts described herein will be better understood with the following detailed description and the non-limiting examples given by way of illustration of embodiments of the inventive concepts described herein, namely: Figure 1 A hardware system in which embodiments of the present invention can be deployed is shown; Figure 2 An example of a first type of constant current source implemented within a driver circuit according to embodiments of the present invention is shown; Figure 3 An example of a second type of constant current source implemented within a driver circuit according to embodiments of the present invention is shown; Figure 4 An example of a third type of constant current source implemented within a driver circuit according to embodiments of the present invention is shown; and Figure 5 An example of a constant voltage source implemented within a driver circuit according to embodiments of the present invention is shown. DETAILED DESCRIPTION

[0010] Figure 1 A system 100 for driving a network of multiple light emitting diodes (LEDs) is shown, as indicated by block 30. The multiple LEDs 30 can be arranged in series or in parallel, or in any predetermined arrangement that combines both series and parallel configurations. In example embodiments, the multiple LEDs 30 can be arranged on a headlight or a taillight of an automotive vehicle to perform one or more of a daytime running light (DRL) function, a parking light (PL) function, a turn indicator light (TI) function, a low beam light (LB) function, a high beam light (HB) function, or to create animations using these LEDs. According to embodiments of the present invention, the multiple LEDs 30 can be connected to an LED driver 20 that receives power and / or control signals from a driver circuit 110. The driver circuit 110 is configured to convert input power PWR from a given source 10 to provide one or more power outputs that provide a substantially constant current CCn and at least one power output that provides a substantially constant voltage CVn. The driver circuit 110 can also provide analog outputs as well as one or more control signals, such as low side switches LSSn or high side switches HSSn. The driver circuit can also receive control inputs to control different power outputs and derive control outputs (such as low side switches and high side switches) and / or control or derive analog outputs. According to certain embodiments, the driver circuit can provide multiple stepper motor outputs for driving one or more stepper motors. Such a system can be used in an automotive environment, for example, to control various LED lights or LED light arrays in a vehicle. The power and control signals can come from a body control module BCM 10, for example, as part of a CAN bus.

[0011] According to an embodiment, the driver circuit 110 includes one or more regulators for providing power at a substantially constant current. Figure 2 An example of a first-type DC-DC converter configured to provide a substantially constant current CC1 is shown, which can be used to drive multiple LEDs in an LED display or other arrangements of LEDs. Figure 2 A first type of constant current source that can be deployed within a driver circuit 110 according to an embodiment of the invention is shown. Figure 2 The diagram also illustrates a portion of a load 200 that can be driven by a constant current source of a driver circuit. In an embodiment, the load 200 may correspond to an LED string. In this case, CC1 is a constant current driven to the load, and CC1' may be a return current returning from the load or an additional output current provided in parallel with the load, depending on the settings of the switches controlled by MPION and MPION+1. According to an embodiment of the invention, such a converter may be available within the driver circuit 110.

[0012] The driver circuit 110 may have a decoder (not shown) for decoding control signals (e.g., signals present on a CAN bus, which...). Figure 1 The internal power bus (INTP) can be sourced from an external power input located at the power input port PWR of the driver circuit 110. The power input port can be electrically connected to the vehicle battery terminal or another suitable power source from the vehicle. According to an embodiment, the internal power bus can be alternately connected to and disconnected from the power port based on control signals from or derived from the internal command bus COM.

[0013] The internal power bus INTP can be fed to a first buck-boost converter 122 in the driver circuit 110 to provide power at one of the power output ports 22 of the driver circuit 110 at a substantially constant current CC1. The first buck-boost converter 122 can be controlled using an internal command bus COM. In example embodiments, the internal command bus COM signal can be provided by a body control module (BCM) (not shown in the figures) located external to the driver circuit 110. The substantially constant current output CC1 can be provided to an LED or LED chain or other LED array via the first buck-boost converter 122. According to embodiments, return current from the plurality of LEDs can reach the port 24 of the driver circuit 110. According to embodiments, the command bus COM signal from the BCM is fed to an analog-to-digital converter (not shown in the figures) of the driver circuit 110, and the output of the analog-to-digital converter is provided as a control input to the first power controller circuit 112. According to embodiments, the driver circuit 110 can be configured to convert the analog-to-digital converter output ADCn, ADCn+1 according to the state of the control signal CTL, and generate high-side and low-side control signals to control high-side and low-side switches, the high-side and low-side control signals being derived from either of the first internal multipurpose input / output bus or the second internal multipurpose input / output bus. The two control signals from within the driver circuit 110 (e.g., high-side switch control HSS1 and low-side switch control LSS2) can be used to control whether the return current is routed to ground or re-routed to the constant current output port 22, effectively providing on / off control for any LED driven by the constant current output. It should be noted that the LED 200 is controlled by the power controller 112 without the need to modify the output power from the first buck-boost converter 122. Thus, the constant current output CC1 from the first buck-boost converter 122 remains constant regardless of load conditions. Further, the input power to the power controller 112 is independent of the output power of the first buck-boost power converter 122.

[0014] Figure 3An example of a second type of DC-DC converter configured to provide a substantially constant current CC2 is shown, which converter can be used to drive one or more LEDs in an LED display or other LED arrangement. In this type of DC-DC converter, a second buck-boost converter 124 can be used to provide power at one of the power output terminals 25 of the driver circuit 110 at a substantially constant current CC2. The second buck-boost converter 124 can be controlled using the internal command bus COM. The return current path via the port 26 can be controlled using a low-side switch control signal MPIOn to block or allow return current to ground. The low-side switch control signal MPIOn can originate from the internal command bus COM via the second power controller circuit 114 (similar to the circuit (112) used in Figure 2

[0015] Figure 4 An example of a third type of DC-DC converter configured to provide a substantially constant current CC3 is shown. This is similar to the converter shown in Figure 2 , with the difference that the third type uses a boost converter 125 followed by a buck converter 126. The power controller 116 is similar to the controller used in Figure 2 .

[0016] Figure 5 An example of a DC-DC converter configured to provide a substantially constant voltage is shown. This circuit uses a buck converter 128 designed to provide a substantially constant output voltage CV1, which is controlled by a power controller 118. The constant voltage According to an embodiment, the output of the analog-to-digital converter can preferably be brought to one or more output pins of the driver circuit 110 via one of the power controller circuits 122, 114, 116 and 118. According to another embodiment, one or more of the internal command bus signals can preferably be routed to one or more analog outputs of the driver circuit 110 via one of the power controller circuits. According to an embodiment, one or more of the low-side switch control signals or high-side switch control signals can preferably be brought to one or more output pins of the driver circuit 110 via one of the power controller circuits.

[0017] According to an embodiment, a plurality of outputs of the driver circuit 110 are provided for driving one or more stepper motors. The stepper motor outputs can originate from one or more multipurpose input / output lines, which in turn can originate from one or more internal command buses.

[0018] ​The car in which embodiments of the present application can be deployed can comprise a main controller or engine control unit, ECU. Signals from this controller, located outside the driver circuit of the present application, can reach the driver circuit via the car's CAN bus. The CAN transceiver on the driver circuit can receive the CAN signals from the car's main controller, and these signals can be used by one or more of the first and second power controllers in the driver circuit to turn on and / or off respective LEDs in the LED display arrangement. According to an embodiment, the power controllers can be configured to operate the switches via the HSS1 and LSS1 signals to operate the LEDs. According to another embodiment, either of these power controllers can be used to directly activate a load, for example to drive the ADC port.

Claims

1. A driver circuit configured to provide output power at a plurality of output terminals to drive a plurality of light emitting diodes, the driver circuit comprising: a power input port to receive input power and convert to provide the output power; at least one digital input port to receive digital commands and / or communication signals for controlling the driving of the plurality of light emitting diodes; a decoder configured to receive and decode digital commands and / or communication signals from the digital input port to provide an internal command bus comprising one or more digital command lines; one or more DC-DC power converters configured to provide power at a substantially constant current via at least one of the plurality of output terminals of the driver circuit; one or more DC-DC power converters configured to provide power at a substantially constant voltage via at least one remaining output terminal of the plurality of output terminals of the driver circuit; characterized in that the driver circuit further comprises: a first power controller circuit configured to receive a digital power input whose value is a function of the level of input power received at the power input port and to provide a first internal multipurpose input / output bus for conveying first internal multipurpose bus encoding values that are a function of the state of the internal command bus and the value of the digital power input; a second power controller circuit configured to provide a second internal multipurpose input / output bus for conveying second internal multipurpose bus encoding values that are a function of the state of the internal command bus; and an internal power supply bus to provide input to the DC-DC power converters.

2. The driver circuit of claim 1, wherein, the internal power supply bus is configured to be alternately connected to and disconnected from the power input port of the driver circuit as a function of the state of at least one digital signal from one of the internal multipurpose input / output buses.

3. The driver circuit of any one of claims 1 or 2, having one or more digital output terminals whose values are a function of the state of one or more lines of the first internal multipurpose input / output bus.

4. The driver circuit according to any one of the preceding claims, wherein, at least one of the DC-DC power converters configured to provide power at a substantially constant current comprises a buck-boost converter configured to convert power at the internal power supply bus as a function of the digital power input value and the state of a plurality of lines of the first internal multipurpose input / output bus to provide the power at a substantially constant current via the plurality of output terminals of the driver circuit.

5. The driver circuit according to any one of the preceding claims, wherein, At least one of the DC-DC power converters configured to provide power at a substantially constant voltage comprises a step-down converter configured to convert power at the internal power bus according to a digital value on the internal command bus and a state of one or more lines of the second internal multipurpose input / output bus to provide the power at a substantially constant voltage via at least one of the outputs of the driver circuit.

6. The driver circuit according to any one of the preceding claims, wherein, At least one of the DC-DC power converters configured to provide power at a substantially constant voltage comprises a step-down converter configured to convert power at the internal power bus according to a digital value on the internal command bus and a state of one or more lines of the second internal multipurpose input / output bus to provide the power at a substantially constant voltage via at least one of the outputs of the driver circuit.

7. The driver circuit according to any of the preceding claims, further comprising a third power controller circuit configured to provide a third internal multipurpose input / output bus having a digital value according to a digital value on the internal command bus; wherein the driver circuit comprises one or more further digital outputs having a value according to a state of one or more lines of the third internal multipurpose input / output bus.

8. The driver circuit according to claim 7, further comprising a further DC-DC power converter configured to provide power at a substantially constant current at a further plurality of outputs of the driver circuit according to a digital value on the internal command bus and a state of one or more lines of the third internal multipurpose input / output bus.

9. The driver circuit of any one of claims 7 or 8, wherein, The further DC-DC power converter configured to provide power at a substantially constant current comprises a step-up converter configured to step up the internal power bus to an intermediate internal power level and at least one step-down converter configured to convert the intermediate internal power level according to a digital value on the internal command bus and a state of one or more lines of the third internal multipurpose input / output bus to provide the power at a substantially constant current via a plurality of outputs of the driver circuit.

10. The driver circuit according to any of the preceding claims, further comprising a digital output configured to reflect a state of the internal command bus.

11. The driver circuit according to any of the preceding claims, further comprising an analog-to-digital converter configured to convert an analog signal on the power input port to provide the digital power input value.

12. The driver circuit according to any one of the preceding claims, further comprising one or more analog output ports, wherein, One or more signals from any of the multipurpose input / output buses are available at the digital output port.

13. The driver circuit according to any of the preceding claims, further comprising one or more additional digital outputs, said one or more additional digital outputs originating from one or more lines included in any of the internal multipurpose input / output buses, said additional outputs being available as high side or low side control signals for controlling one or more switches.

14. The driver circuit according to any of the preceding claims, further comprising a plurality of outputs for driving one or more stepper motors, said additional plurality of outputs originating from the internal command bus.

15. The driver circuit according to any one of the preceding claims, wherein, The internal power bus is connectable to a power input port of the driver circuit.

Images