Highly efficient direct mains power supply for connected LED drivers

Abstract

The present invention relates to a power supply having a rectifier for receiving an alternating current (AC) input voltage and providing a rectified voltage, a switched-mode power supply adapted to receive the rectified voltage and provide a regulated output voltage to a load, a first sensor for sensing the rectified voltage and providing a first control signal, and a controller for controlling the switched-mode power supply, the controller configured to enable and disable the switched-mode power supply, the controller configured to enable the switched-mode power supply when the first control signal is below a threshold level and to disable the switched-mode power supply when the first control signal is above the threshold level.

Description

[Technical field]

[0001] The present invention relates to a power supply.The present invention further relates to a lighting device.The present invention further relates to a method for controlling a power supply. [Background technology]

[0002] In connected direct mains LED driver applications, a separate low-voltage power supply is needed to supply the controller and communication circuitry. The low-voltage power supply is needed to power the controller and communication circuitry continuously, regardless of whether the LED driver is running or in standby. The communication must always be able to listen to the remote sender and detect the wake-up signal for the LED driver. The low-voltage power supply typically needs only about 50mW of supply power, while LEDs can generally be driven with a few watts or more of power. The resulting standby power in the LED driver contributes significantly to the standby losses of the LED driver or lighting device. Today, the efficiency is around 20-30%. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide a power supply with improved efficiency. [Means for solving the problem]

[0004] To provide this power supply, in a first aspect of the invention the power supply comprises: a rectifier for receiving an alternating current (AC) input voltage and providing a rectified voltage; a switched mode power supply adapted to receive the rectified voltage and to provide a regulated output voltage to a load; a first sensor for sensing the rectified voltage and providing a first control signal; a controller for controlling the switched mode power supply; the controller is configured to enable and disable the switched mode power supply; The controller is configured to enable the switched-mode power supply when the first control signal is below a threshold level and to disable the switched-mode power supply when the first control signal is above the threshold level.

[0005] The power supply receives an AC voltage. This AC voltage may be a normal mains voltage, such as the well-known examples 220-230V at 50Hz or 110-120V at 60Hz. This AC voltage is rectified by a rectifier. This rectified voltage is fed to a switched-mode power supply, which converts the rectified voltage into a regulated output voltage for a load. The rectified voltage is also fed to a first sensor. The first sensor senses the rectified voltage and provides a first control signal based on the sensed rectified voltage. A controller is used to control the switched-mode power supply. The controller is used to enable and disable the switched-mode power supply. The controller receives the first control signal and compares it to a threshold level. If the first control signal is below the threshold level, the controller enables the switched-mode power supply. If the first control signal is above the threshold level, the controller disables the switched-mode power supply. This means that the switched-mode power supply is enabled based on whether the rectified voltage is above or below a predefined value. The switched-mode power supply may be powered by this rectified voltage when it is below the predetermined value, and the switched-mode power supply may also be powered via another power source when the rectified voltage is above the predetermined value.

[0006] In another example, the switched mode power supply is a self-oscillating switched mode power supply.

[0007] Preferably, the switched mode power supply is a self-oscillating switched mode power supply, since this can be enabled and disabled very quickly.

[0008] In another example, the switch mode power supply is a buck converter or a flyback converter.

[0009] Buck converters are likely to benefit most from this invention because they already supply a low voltage, e.g., 3.3 V, while only receiving a low input voltage, which allows the ratio of input voltage to output voltage to be kept close to 1.

[0010] In another example, the switched mode power supply includes a second sensor for sensing the regulated output voltage and generating a second control signal, the controller being configured to receive the second control signal.

[0011] A second sensor may be used to sense the regulated output voltage. The second sensor provides a second control signal based on the sensed regulated output voltage. The controller receives the second control signal. Based on the second control signal the threshold level may be determined. This may mean that a change in the regulated output voltage may result in a change in the threshold level. This may also mean that the threshold level may be increased when the regulated output voltage decreases, for example due to an increase in power consumption by the load. Additionally or instead the threshold level may be decreased when the regulated output voltage increases, for example due to a decrease in power consumption by the load.

[0012] In another example, the threshold level is based on a power required by the load, and the controller: The threshold level is configured to increase based on an increase in the power required by the load and to decrease based on a decrease in the power required by the load.

[0013] Preferably, the threshold level can be varied. The threshold can be increased or decreased based on the amount of power required by the load. If the load power increases, the threshold level may be raised and if the load power decreases, the threshold level may be lowered. This may allow the switched mode power supply to operate at a single operating point and allow the switched mode power supply to operate more efficiently over the range of power required by the load.

[0014] In another example, the controller is part of the load.

[0015] Preferably, the load is a low power consumption load. This low power consumption may occur, for example, when the power supply is in standby. When the power supply is in active mode, the load may consume more power. The load may include the controller. The controller may also require more power during operation mode than during standby mode.

[0016] In a second aspect, the lighting device comprises: A power supply according to any of the previous examples; a further power source for powering a further load; The load; and the further load.

[0017] A lighting device may have a power supply for powering components that require low voltage and / or low power. A further power supply may be used to power another load, which may have power requirements that are much higher than the power requirements of the load powered by the power supply.

[0018] In a further example, the further load is a lighting load.

[0019] Preferably, the further load is a lighting load. The power supply supplies power to the load and the further power supply supplies power to the lighting load.

[0020] In a further example, the lighting load comprises a light emitting diode (LED).

[0021] Preferably, the lighting load is an LED load. An LED load is an efficient light source.

[0022] In a further example, the controller includes a wireless communication module configured to receive wireless signals, and the controller is configured to enable or disable the further power source based on the received wireless signals.

[0023] Preferably, the lighting device is capable of receiving control signals from an external device. The lighting device may therefore comprise a wireless communication module that allows the controller to receive control signals via the wireless communication module. The controller may then enable or disable the further power source so that the lighting device can be in standby mode or active mode. During standby, the controller does not need to control and / or power the further power source. This means that the controller may require less power to operate.

[0024] In a further example, the further power supply comprises a further controller. The further power supply may have its own dedicated controller, which may also be powered by the power supply.

[0025] In a further example, the controller is configured to control the switched mode power supply and the further power supply.

[0026] The controller may be used to control the switched mode power supply and the further power supply, in which case the controller may be a single control unit such as a microcontroller.

[0027] In a third aspect, the method comprises: using a rectifier for receiving an alternating current (AC) input voltage and providing a rectified voltage; using a first sensor for sensing the rectified voltage and providing a first control signal; using a controller for controlling a switched mode power supply for powering a load; enabling the switched mode power supply when the first control signal is below a threshold level; and Disabling the switched mode power supply when the first control signal is above the threshold level.

[0028] Similar to the power supply previously described, the method provides a way of controlling the switched mode power supply by disabling it when a threshold level is exceeded, the threshold level being representative of the input voltage, which may be the AC mains voltage.

[0029] In a further example, the method further comprises: increasing the threshold level when the power required by the load increases; and Lowering the threshold level when the power required by the load decreases.

[0030] Preferably, the threshold level increases when the power required by the load increases, and may decrease when the power required by the load decreases. [Brief description of the drawings]

[0031] Examples of the invention will now be described with reference to the accompanying drawings, in which: [Figure 1] An example of a power source is shown. [Diagram 2] 1 illustrates an example of a controller for controlling the power supply. [Diagram 3] 4 shows a graph illustrating the operating window of the power supply. [Figure 4] 4 shows a graph depicting an expanded graph of the operating window of the power supply. [Diagram 5] 1 shows an example of a lighting device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present invention will be described with reference to the drawings.

[0033] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the devices, systems and methods of the present invention will become better understood from the following description, appended claims and accompanying drawings. It should also be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to denote the same or similar parts.

[0034] In FIG. 1 an example of a power supply is shown. The power supply has a rectifier 3 which receives an AC voltage. The AC voltage can be any AC voltage, but is preferably a mains voltage, for example 230V at 50Hz or 120V at 60Hz. The rectifier 3 receives this AC voltage and provides a rectified voltage. The rectified voltage is provided to a switched mode power supply 1. The switched mode power supply 1 converts the rectified voltage into a regulated output voltage that can be used by a load. The rectified voltage is sensed by a first sensor 4. This first sensor 4 may be a voltage sensor with a first resistor R1 and a second resistor R2. The rectified voltage is then stepped down to a level that can be used by further circuits. The first sensor 4 receives the rectified voltage and uses this rectified voltage to provide a first control signal. This first control signal is provided to a controller 2. The controller 2 may generate a threshold level that can be used as a reference level. The first control signal is compared to this threshold level. The threshold level is used to represent the voltage level of the rectified mains. This results in the controller providing an indirect comparison of the rectified voltage with a voltage threshold level. If the first control level is below the threshold level, this may be interpreted as the rectified voltage being below a predetermined value. The controller 2 may provide a control signal to control the switched-mode power supply 1. The control signal is represented in FIG. 1 as an arrow from the controller 2 to the switched-mode power supply 1. If the first control level is below the threshold level, the controller 2 may enable the switched-mode power supply 1. If the first control level is above the threshold level, the controller 2 may disable the switched-mode power supply 1. The switched-mode power supply 1 receives a rectified voltage below the threshold level and provides a regulated output voltage to the load. The switched-mode power supply 1 also receives a voltage above the threshold level, but does not provide a regulated output voltage to the load. In other words, the threshold level is used to determine whether the switched-mode power supply 1 is enabled or disabled.

[0035] The main advantage of enabling and disabling the switched-mode power supply 1 in this manner is that it allows the switched-mode power supply 1 to operate at input voltage levels that remain relatively low. The switched-mode power supply 1 converts more efficiently at such lower voltage levels, e.g. at the peak of the mains voltage level. Preferably, the switched-mode power supply 1 is a buck converter that converts the rectified input voltage to a voltage lower than the regulated output voltage. The load may then receive this lower voltage. The output voltage may be between 1V and 10V, more preferably between 1V and 5V. The controller 2 may be part of the load and may require a lower voltage, such as 3.3V or 5V.

[0036] The switched mode power supply 1 may also be any other type of converter, such as, for example, a boost converter, a buck-boost converter, a flyback converter or a resonant converter. Preferably, the switched mode power supply 1 is of the self-oscillating type. This type of switched mode power supply 1 responds to enable and disable signals faster than, for example, an IC-based switched mode power supply. The load may be any kind of load that preferably requires low voltage and / or low power.

[0037] The power supply may have a second sensor 5 that may be used to sense the regulated output voltage. The second sensor 5 may have a first resistor R3 and a second resistor R4 to divide the voltage to create the second control signal. Because the regulated output voltage may be relatively low, a voltage divider may not be needed and the second sensor 5 may directly sense the regulated output voltage and forward it directly as the second control signal. The second control signal may be provided to the controller 2. The controller 2 may use this second control signal as a feedback signal to control the regulated output voltage. The controller may additionally or alternatively use the second control signal to determine if the power requirements of the load have changed. When the load suddenly draws more or less power, this affects the regulated voltage for a very short time. If the load requires more power and therefore draws a larger current, the regulated output voltage may have a very short voltage drop until the controller 2 regulates the output voltage back to its desired level. If the load requires less power and therefore draws less current, the regulated output voltage may have a very short voltage spike until the controller 2 regulates the output voltage back to its desired level. This voltage drop or voltage spike may be detected by the second sensor 5. The controller 2 may then receive the detection of the voltage drop or voltage spike and respond accordingly.

[0038] For example, when the controller 2 detects a voltage drop, the controller 2 may increase the threshold level to allow the switched-mode power supply 1 to supply power for a longer period of time. Increasing the threshold level allows the controller 2 to enable the switched-mode power supply 1 for a longer period of time, i.e., until the AC input voltage reaches a higher voltage level. The switched-mode power supply 1 may then supply more power during a mains cycle, allowing it to supply more power to the load.

[0039] For example, when the controller 2 detects a voltage spike, the controller 2 may lower the threshold level to allow the switched-mode power supply 1 to supply power for a shorter period of time. The lowering of the threshold level allows the controller 2 to enable the switched-mode power supply 1 for a shorter period of time, i.e., until the AC input voltage reaches a lower voltage level. The switched-mode power supply 1 then supplies less power during the mains cycle, allowing it to supply less power to the load.

[0040] Alternatively, or in addition, the switched mode power supply 1 or the load may provide the required load power as a feedback signal to the controller 2 so that the controller can respond directly to changes in the required load power.

[0041] FIG. 2 shows an example of a controller 2. The controller receives a first control signal as described above. Optionally, the controller 2 may receive a second control signal as described above. The controller 2 may have a signal generator 7 that provides an enable signal used to enable and disable the switched mode power supply. The signal generator 7 may generate a threshold level and provide the threshold level to a comparator U1. The comparator U1 compares the first control signal with the threshold level. In this example, when the first control signal is greater than the threshold level, the comparator provides a low output signal. This low output signal may indicate to the signal generator 7 that the AC input voltage is greater than a predetermined value. The signal generator 7 may then disable the switched mode power supply 1. In this example, when the first control signal is less than the threshold level, the comparator provides a high output signal. This high output signal may indicate to the signal generator 7 that the AC input voltage is less than a predetermined value. The signal generator 7 may then enable the switched mode power supply 1. It is clearly understood that in this example, the inputs to comparator U1 can be switched so that the result of the comparison is the inverse compared to the previous example.

[0042] Another comparator U2 may be used to compare a second control signal with a reference voltage Vref2. When the second control signal is greater than the reference voltage Vref2, the comparator may provide a low output signal indicating that the regulated output voltage to the load exceeds a predetermined value. The comparator may be used, for example, in a feedback loop of the switched mode power supply 1 to appropriately adjust the regulated output voltage.

[0043] Alternatively, or in addition, comparator U2 may be used to determine whether the regulated output voltage has a voltage spike or dip that indicates a change in the power requirements of the load. This may provide information to signal generator 7 to raise or lower the threshold level. Signal generator 7 may then adjust the threshold level based on the power required by the load, i.e., the voltage behavior of the regulated output voltage.

[0044] The signal generator 7 may also receive an additional input signal from the communication module 5. Preferably, the communication module 5 is a wireless communication module. The wireless communication module 5 may use any commonly known protocol, such as ZigBee, WiFi, Bluetooth or LiFi (Light Fidelity). The wireless communication module 5 may provide additional control commands to the signal generator 7, such as a standby signal. When a standby signal is provided to the signal generator 7, the power supply may need to provide only a small amount of power to continue to operate in standby. In that case, the signal generator 7 may decide to lower the threshold level. When an activation signal is provided to the signal generator 7, the power supply may need to provide a relatively large amount of power to continue to operate in activated mode. In that case, the signal generator 7 may decide to raise the threshold level. This method of changing the threshold level may be performed as an alternative to or together with the threshold level control based on the comparison of the reference voltage Vref2 with the second control signal.

[0045] The main advantage of changing the threshold level by raising or lowering it is that the switched-mode power supply 1 can operate closer to a single operating point. Instead of adapting, for example, the operating frequency or current amplitude to adjust the regulated output voltage, the period during which the switched-mode power supply 1 is active can be used as a control parameter. In that case, the frequency and / or current adjustment may not need to have a wide operating range and can even preferably be kept constant.

[0046] FIG. 3 shows an example of a mains periodic cycle. The mains periodic cycle is represented as a rectified sinusoidal voltage waveform. FIG. 3 also shows the current flowing through the load. This current is supplied by the switched-mode power supply 1. It can be clearly seen that the switched-mode power supply 1 can only operate when the mains voltage is close to zero. The mains voltage has a peak voltage of about 320V, which corresponds to a root-mean-square voltage of 230V. In this example, the threshold levels are set at levels that represent an AC input voltage amplitude of about 140V. In this example, the thresholds are symmetrically located before and after the zero crossing of the AC input voltage. It should be understood that the threshold levels may differ from each other, for example such that the switched-mode power supply 1 operates from a zero crossing of the AC input voltage to a threshold level that in this example represents an AC input voltage of about 140V.

[0047] Figure 4 shows an enlarged view of a portion of the mains cycle of Figure 3. The enlarged area is focused on a zero crossing of the AC input voltage. The switching of the switched-mode power supply 1 can be seen in more detail.

[0048] Fig. 5 shows a simplified example of a system having a power supply. Preferably, the system is a lighting device. The lighting device may have a power supply as defined above.

[0049] The lighting device has a rectifier 3 which rectifies the AC input voltage and supplies the rectified voltage to the switched-mode power supply 1 and to the further power supply 6. The further power supply 6 may be used to power a further load LED, which in this example is a LED lighting load LED. The LED lighting load LED may be used to provide general lighting. The further power supply 6 may have the same components as described in the previous example. The switched-mode power supply 1 supplies power to the load. In this example, the controller 2 is part of the load. The switched-mode power supply 1 may also supply additional power to a further controller which is used to control the further power supply 6. The controller 2 and the further controller may also be integrated into a single controller unit, with the switched-mode power supply 1 supplying power to the single controller unit. In this example, the controller 2 is also used to control the further power supply 6. The power supply may be any other type of power supply, such as, for example, a buck converter, a boost converter, a buck-boost converter, a flyback converter or a resonant converter. The controller 2 may have a wireless communication module 5 as specified in the previous example. This wireless communication module 5 may be used to receive a signal that allows the lighting device to enter a standby mode or an operating mode. When the lighting device is set to standby mode, the further power supply 6 may be completely switched off and require no power or significantly less power compared to the operational mode. The controller 2 may then also require less power to power the power supply and the further power supply 6. This may enable the signal generator 7 to lower the threshold level so that the switched mode power supply 1 in the power supply supplies less power to the load, which in this example includes at least the controller 2. As defined above, the signal generator 7 may perform this lowering of the threshold level based on a voltage spike detected in the regulated output voltage to the controller 2 or by receiving a standby signal from the wireless communication module 5.

[0050] The wireless communication module 5 may also receive an operating signal. This sets the lighting device in an operating mode. During the operating mode, the further power supply 6 supplies a controlled amount of power to the LED lighting load LED. In this situation, the controller 2 may require more power than in the standby mode. Compared to the standby mode, the signal generator 7 may increase the threshold level to allow the switched mode power supply 1 to supply power for a longer period of time.

[0051] Those skilled in the art can understand and achieve other variations to the disclosed embodiments in the practice of the claimed invention, from a study of the drawings, the specification and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and the singular does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. A rectifier that receives an AC input voltage and supplies a rectified voltage, A switch-mode power supply adapted to receive the rectified voltage and supply a regulated output voltage to a load, A first sensor for detecting the rectified voltage and supplying a first control signal, A power supply having a controller for controlling the switch-mode power supply, The controller is configured to enable and disable the switch-mode power supply, The controller is configured to enable the switch-mode power supply when the first control signal falls below a threshold level, and to disable the switch-mode power supply when the first control signal exceeds the threshold level. The aforementioned switch-mode power supply is a power supply in which the power supply is a buck converter or a flyback converter.

2. The power supply according to claim 1, wherein the switch-mode power supply is a self-oscillating switch-mode power supply.

3. The power supply according to claim 1, wherein the switch-mode power supply has a second sensor for detecting the adjusted output voltage and generating a second control signal, and the controller is configured to receive the second control signal.

4. The threshold level is based on the power required by the load, and the controller, The power supply according to claim 1 or 2, configured to raise the threshold level based on an increase in the power required by the load and to lower the threshold level based on a decrease in the power required by the load.

5. The aforementioned controller The change in the adjusted output voltage is detected, Based on the decrease in the adjusted output voltage, the threshold level is increased. The power supply according to claim 3, configured to lower the threshold level based on an increase in the adjusted output voltage.

6. The power supply according to any one of claims 1 to 3, wherein the controller is part of the load.

7. The power supply according to claim 1, Further power sources to supply power to further loads, The aforementioned load and, A lighting device having the aforementioned further load.

8. The lighting device according to claim 7, wherein the further load is a lighting load.

9. The lighting device according to claim 8, wherein the lighting load has a light-emitting diode.

10. The lighting device according to any one of claims 7 to 9, wherein the controller has a wireless communication module configured to receive a wireless signal, and the controller is configured to enable or disable the further power supply based on the received wireless signal.

11. The lighting device according to any one of claims 7 to 9, wherein the further power supply has a further controller.

12. The lighting device according to any one of claims 7 to 9, wherein the controller is configured to control the switch-mode power supply and the further power supply.

13. A method for controlling a switch-mode power supply, wherein the switch-mode power supply is a buck converter or a flyback converter, A rectifier is used to receive an AC input voltage and supply a rectified voltage. A first sensor is used to detect the rectified voltage and supply a first control signal. Using a controller to control the switch-mode power supply for supplying power to the load, When the first control signal falls below a threshold level, the switch-mode power supply is enabled, and A method comprising disabling the switch-mode power supply when the first control signal exceeds the threshold level.

14. When the power required by the load increases, the threshold level is raised, and The method according to claim 13, further comprising lowering the threshold level when the power required by the load decreases.

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