Control circuit for detecting interruption of input power

Abstract

There is provided a control circuit for use with a device (40) having a power supply unit (PSU) that receives an input power (AC) and provides an output voltage (VBUS) to a variable load (LED), the control circuit comprising: a detection circuit adapted to detect a drop in the output voltage (VBUS) and determine an interruption of the input power (AC) accordingly; and a configuration circuit adapted to configure the device according to the determined interruption of the input power (AC), characterized in that the detection circuit is adapted to detect a power level of the load (LED); and determining an interruption of the input power if the output voltage (VBUS) falls below a first threshold value (Vth1), with the power level of the load being at a first level (25%); determining an interruption of the input power if the output voltage (VBUS) falls below a second threshold (Vth2), with the power level of the load being at a second level (50%); wherein the first level (25%) and the second level (50%) are different, and the first threshold value (Vth1) and the second threshold value (Vth2) are different.

Description

Technical Field

[0001] The present invention relates to the field of power electronics. Background Art

[0002] Many lighting devices do not have any mechanical control components to configure them. They may have a wireless control interface, where the user can configure it via a wireless terminal (such as a smartphone). But configuring it via a smartphone is often a bit inconvenient. Therefore, many lighting devices, whether or not they have a control interface, have the additional ability to detect interruptions in the input power, and configure the lighting device via the number of interruptions in the input power. This interruption (and restoration) of the input power is called switching. The user can switch the input power by turning off and on a switch connected to the lighting device, and the lighting device receives this power switch. Today, configuring the state of a device has become an important method, such as setting a lighting device to exchange its light state, such as brightness, color temperature, etc., among multiple available states, or even resetting the lighting device to factory defaults.

[0003] Figure 1A typical architecture of an LED lighting device is shown, which can control the brightness of an LED based on power switching. AC is the AC main input power. A switch 12 (such as a wall switch) is connected between the AC main input power and the LED lighting device 10. The LED lighting device 10 has a power supply unit PSU for receiving the AC main input power and converting the AC main input power to an output voltage VBUS on a bus. Typically, the PSU has a large output capacitor C at its output to the bus to smooth the output voltage. The LED lighting device LED is connected to the bus and is optionally powered by the output voltage via a current regulator not shown, because the LED is preferably current driven. A controller, shown as an MCU, generates a pulse width modulation PWM signal to control the frequency at which the LED is powered by the output voltage, thereby adjusting the brightness of the LED. Finally, a control circuit, shown as an operational amplifier, compares the output voltage VBUS on the bus with a certain threshold value Vth. As shown in the figure, the output voltage VBUS is located at the non-inverting input of the operational amplifier, and a certain threshold value Vth is located at the inverting input of the operational amplifier, so that when the output voltage VBUS is lower than a certain threshold value Vth, the operational amplifier will output a high signal, and the device determines that the input power has been interrupted and will notify the controller. The user switches the switch to the off state and keeps it in the off state to allow the output voltage VBUS to drop below the threshold, and the interruption can be detected, and then the user can switch the switch to the on state. Optionally, the operational amplifier can also detect when the output voltage VBUS is restored. Moreover, this interruption and recovery constitute a complete turn-off and turn-on, that is, power switching. Therefore, the controller adjusts its PWM signal from the previous state to the next state. For example, before switching, the duty cycle of PWM is 50% to set the lighting device at a medium brightness level. After switching, the MCU sets the duty cycle of PWM to 25% to set the lighting device at a low brightness level. And the next time the switch is detected, the MCU sets the duty cycle of PWM to 0% to set the lighting device to standby. The reason why the output voltage VBUS is used to determine the interruption of input power instead of using the AC input of the PSU to determine the interruption of input power is because it is difficult to detect and process the AC side signal through the controller on the DC side, but it is easy to detect and process the DC side signal VBUS because the controller is on the same side / ground relative to the DC side signal VBUS.

[0004] The inventors have found that at different load power levels of the LED lighting device, the time for the output voltage VBUS to reach such a threshold varies greatly, and it is difficult to achieve consistent user behavior at different load power levels.

[0005] The reason is that for the output capacitor C, if the load power level is different, the load consumes energy in the output capacitor C at different rates. The LED lighting device set at a 25% duty cycle consumes power at a rate that is approximately half that of the LED lighting device set at a 50% duty cycle. Therefore, the time required for the output voltage VBUS to reach the threshold Vth in the 25% duty cycle case is twice that of the 50% duty cycle case. Figure 2 As shown, when the switch 12 is turned on at time zero in the case of the original heavy load operation (50% duty cycle), for example, the LED lighting device operating under the heavy load quickly draws power from the output capacitor C, and the output voltage VBUS is relatively fast to reach the threshold value Vth at time T. When the switch is turned on at time zero in the case of a small load (for example, at a 25% duty cycle), or even in the standby state where the LED lighting device does not emit light, the output capacitor C is slowly discharged through the small load, and the output voltage VBUS may take a longer time to reach the threshold value at T'.

[0006] In an embodiment, if the threshold is set low, it is OK to determine the interruption under heavy load; but when the system is working under light load, the user needs to switch the switch to the off state for a very long time to allow the output voltage to drop below the threshold. First, such a long time may be unbearable; second, the user's interaction with the switch is different under heavy load and light load, and this is particularly unfriendly. If the threshold is set high, the fluctuation of the output voltage under heavy load is often large, and even if the input power is not interrupted, the output voltage may drop below the high threshold and falsely trigger the threshold. It is difficult to find an appropriate threshold.

[0007] EP3125650A1 discloses a solution for detecting excess output based on a voltage drop at the output, and the extent of the voltage drop may be determined by the capacitance in the device. Summary of the invention

[0008] The invention is defined by the claims.

[0009] The basic idea of ​​the present invention is to provide adjustability for the threshold value, determining the interruption of the input power according to the actual load power level. If the load is a heavy load, the output voltage drops more when the input power is lost / turned off, and a lower threshold is configured; and if the load is a light load, the output voltage drops less when the input power is interrupted / turned off, and a higher threshold is configured. In this way, no matter what the load level is, the user can keep the switch off for the same duration to allow the output voltage to drop below the threshold and trigger a successful determination of the interruption. The voltage will drop below the corresponding threshold with more confidence, and the switching can be accurately determined.

[0010] In a first aspect of the present invention, a control circuit is provided for use with a device having a power supply unit adapted to be connected to and receive input power and adapted to provide an output voltage to a power variable load, the control circuit comprising: a detection circuit adapted to detect a drop in the output voltage and correspondingly determine an interruption of the input power; and a configuration circuit adapted to configure the device according to the determined interruption of the input power, characterized in that the detection circuit is adapted to: detect the power level of the load; determine an interruption of the input power if the output voltage drops below a first threshold when the detected power level of the load is at a first level, and determine an interruption of the input power if the output voltage drops below a second threshold when the detected power level of the load is at a second level; wherein the first level and the second level are different, and the first threshold and the second threshold are different.

[0011] The first aspect uses different thresholds for output voltages at different load power levels. Therefore, the speed of reduction of the output voltage at different load power levels is taken into account, and the interruption of input power can be accurately detected regardless of the power level of the load. Therefore, the present application can support a wide operating range of the load.

[0012] In another embodiment, the first level is less than the second level, and the first threshold is higher than the second threshold. For light load conditions, the threshold is set higher; for heavy load conditions, the threshold is set lower. The time required for the output voltage to drop below the corresponding threshold is similar, so the user only needs to switch the switch to the off state for a similar time regardless of the power level of the load. This provides acceptable and consistent operating times to the user and is user-friendly.

[0013] In another embodiment, the sizes of the first threshold and the second threshold are designed so that when the input power is interrupted, the output voltage drops below the first threshold for a certain duration when the load is at a first level, and the output voltage drops below the second threshold for substantially the same certain duration when the load is at a second level.

[0014] In this embodiment, the time required for the output voltage to drop below the corresponding threshold value is substantially the same, which is consistent and user-friendly for the user.

[0015] In another embodiment, the detection circuit includes: a comparison circuit for comparing the output voltage with a reference; a first circuit for detecting a power level of the load; and a second circuit for setting a first threshold or a second threshold as a reference for the comparison circuit according to the detected power level of the load.

[0016] This embodiment provides a detailed implementation of the detection circuit.

[0017] In another embodiment, the first circuit includes: a current detector for detecting a current from the power supply unit to the variable power load; and a processing circuit for determining a power level of the load based on the detected current.

[0018] The current from the power supply is related to the load power level: when the load power level is large, the (average / mean) current must be large; vice versa. Therefore, the current can indicate the load power level.

[0019] In an alternative embodiment, the controller of the device already knows the current load power level and can inform the second circuit to set the corresponding threshold.

[0020] In another embodiment, the configuration circuit is adapted to configure the device in one of a plurality of settings based on a number of times an interruption in input power is detected.

[0021] In this embodiment, the number of interruptions in the interruption sequence and the return to normal state when there are no more interruptions determine how to configure. For example, three consecutive switching / interruptions and returning to normal (no more interruptions) control the device to change its load power level to medium; four consecutive switching / interruptions and returning to normal control the device to a small load power level; five consecutive switching / interruptions and returning to normal control the device to a standby load power level; and six consecutive switching / interruptions and returning to normal control the device to a factory default load power level.

[0022] In a more detailed embodiment, the configuration circuit is adapted to: start counting interrupts when an interrupt is detected for the first time; time a cycle, and if an interrupt occurs within the cycle, count the interrupt, and repeat the timing and counting; stop counting if no interrupt occurs within the last cycle; and configure the device in a setting based on the number of interrupts counted.

[0023] In this embodiment, the cycle can be timed by a timer to determine if there are incoming interrupts, and the interrupts are counted and the cycle is reset to detect future interrupts. If there are no interrupts during the last cycle, it is determined that this is the end of the interrupt, and the device is configured according to the number of times the interrupt was counted. The advantage of this embodiment is that the user can quickly configure the device to the desired settings by entering the corresponding interrupt sequence.

[0024] In an alternative embodiment, the configuration circuit is adapted to configure the device to the next setting in the sequence of settings each time an interruption in input power is detected.

[0025] This alternative embodiment controls the device to change its state each time an interrupt is received. This is an alternative switching control of the device. The advantage of this embodiment is that the user does not need to remember the specific power interrupt sequence corresponding to the desired setting, but the device will automatically change to the next setting and the user can stop once the device enters the desired setting.

[0026] In a second aspect of the present invention, there is provided an LED driving device, which includes a power supply unit and a control unit according to the above aspects and embodiments.

[0027] In a third aspect of the present application, an LED lighting device is provided, which includes the LED driving device according to the second aspect and an LED lighting device as a variable load.

[0028] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] For a better understanding of the invention, and to show more clearly how it may be effected, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0030] Figure 1 The general architecture of the LED lighting device and the switch used to configure the LED lighting device are shown;

[0031] Figure 2 The threshold value in the prior art and the waveform of the output voltage under heavy load and light load conditions are shown;

[0032] Figure 3 shows a general architecture of an LED lighting device according to an embodiment of the present application and a switch for configuring the LED lighting device; and

[0033] Figure 4 Waveforms of the threshold value configured by the embodiment of the present invention and the output voltage under heavy load and light load conditions are shown. DETAILED DESCRIPTION

[0034] The present invention will be described with reference to the accompanying drawings.

[0035] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, system and method, are intended only for illustration and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus, system and method of the present invention will become better understood through the following description, the appended claims and the accompanying drawings. It should be understood that these figures are merely schematic and not drawn to scale. It should also be understood that in these figures, the same reference numerals are used to indicate the same or similar components.

[0036] Figure 3 The architecture of an LED lighting device 40 according to an embodiment of the present application is shown, which is capable of controlling the brightness of an LED based on power conversion. AC is the AC main input power. A switch 12 (such as a wall switch) is connected between the AC main input power and the LED lighting device 40. The LED lighting device 40 has a power supply unit PSU, which is used to receive the AC main input power and convert the AC main input power to an output voltage VBUS on a bus. Typically, the PSU can be an AC-DC power supply (or alternatively a DC-DC power supply if the input power is DC), and has a large output capacitor C at its output to the bus to smooth the output voltage. The LED lighting device LED is connected to the bus and is optionally powered by the output voltage VBUS via a current regulator not shown, because the LED is preferably current driven.

[0037] Most importantly, the device 40 includes a control circuit for determining the interruption of the input power. The control circuit includes:

[0038] a detection circuit adapted to detect a drop in the output voltage VBUS and accordingly determine an interruption of the input power AC, and

[0039] The configuration circuit is adapted to configure the device according to the determined interruption of the input power AC. It can be implemented in the following way: the controller shown as MCU generates a pulse width modulation PWM signal to control the frequency of the LED powered by the output voltage, thereby adjusting the brightness of the LED.

[0040] Wherein, the detection circuit is suitable for:

[0041] When the load is at a first level, if the output voltage VBUS drops below a first threshold value Vth1, an interruption of the input power is determined;

[0042] When the load is at a second level, if the output voltage VBUS drops below a second threshold value Vth2, an interruption of the input power is determined;

[0043] The first level and the second level are different, and the first threshold value Vth1 and the second threshold value Vth2 are different.

[0044] exist Figure 3 In the embodiment shown, the detection circuit includes:

[0045] The comparison circuit 41 is used to compare the output voltage VBUS with a reference.

[0046] A first circuit 40 is used to detect the power level of the load, and

[0047] The second circuit 42 is used to set the first threshold value or the second threshold value as a reference for the comparison circuit according to the detected power level of the load.

[0048] More specifically, the comparison circuit 41 is, for example, an operational amplifier 41, which compares the output voltage VBUS on the bus with a threshold value dynamically set to Vth1 or Vth2. As shown in the figure, the output voltage VBUS is located at the non-inverting input of the operational amplifier, and the threshold Vth is located at the inverting input of the operational amplifier, so that when the output voltage VBUS is lower than the threshold, the operational amplifier outputs a high signal, and the device determines that the input power has been interrupted and will notify the configuration circuit / controller MCU. Optionally, the operational amplifier can also detect when the output voltage VBUS is restored. Moreover, this interruption and recovery constitutes a complete shutdown and connection, that is, power switching.

[0049] The configuration circuit / controller MCU adjusts its PWM signal from the previous state to the next state. For example, before switching, the duty cycle of the PWM is 50% to set the lighting device at a medium brightness level. After switching, the MCU sets the duty cycle of the PWM to 25% to set the lighting device at a small brightness level. And the next time a switching is detected, the MCU sets the duty cycle of the PWM to 0% to set the lighting device to standby mode.

[0050] More specifically, the first level is less than the second level, and the first threshold value Vth1 is higher than the second threshold value Vth2. More preferably, the threshold value is set so that: when the load is at the first level, the output voltage VBUS drops below the first threshold value Vth1 for a certain duration T, and when the load is at the second level, the output voltage drops below the second threshold value Vth2 for substantially the same certain duration T.

[0051] Figure 4 The threshold value configured by the embodiment of the present invention and the waveform of the output voltage under heavy load and light load conditions are shown. Taking 25% brightness as the first load power level, when the switching switch 12 is turned on at zero with this load power level (25% duty cycle) under the original operation, for example, the LED lighting device slowly draws power from the output capacitor C, and the output voltage VBUS reaches the threshold value Vth1 / drops below the threshold value Vth1 at time T. Taking 50% brightness as the second load power level, when the switching switch 12 is turned on at zero with this load power level (50% duty cycle) under the original operation, for example, the LED lighting device draws power faster from the output capacitor C, and the output voltage VBUS reaches the threshold value Vth2 / drops below the threshold value Vth2 at the same time T.

[0052] Therefore, regardless of the load power level, the user can switch the switch to the off state and keep it in the off state for the same duration longer than T, so that the output voltage drops below the corresponding threshold, and switch the switch to the on state again. The comparison circuit detects this drop below the threshold and notifies the configuration circuit of this interruption of input power. Therefore, the user can control the device with a single and consistent off / on timing beat (or rhythm) of the switching, and the user experience is friendly.

[0053] Table 1 below provides more examples of thresholds corresponding to different load power levels. Assume that before the interruption, under normal operation, VBUS is 16V.

[0054] Table 1

[0055]

[0056] For example, assuming the switch off time is 3 seconds, the threshold is 0.5V for detecting interruption at full load 20W; and the threshold is 7V for detecting interruption at light load 2W. The detection circuit can maintain / pre-store such a mapping table and select the threshold corresponding to the load power level in real time. More importantly, when the load power level and the corresponding threshold are not explicitly written into the table, the detection circuit can insert the threshold for the load power level based on the available data in the table.

[0057] Alternatively, a formula for calculating the threshold value from the load power level may be stored in the detection circuit, and the detection circuit may use the formula to determine the threshold value corresponding to the load power level.

[0058] The first circuit 40 has many implementations: it can be a current detector between the power supply unit PSU and the load LED, and is used to detect the average current provided to the load LED. A larger average current means a larger load power level; and vice versa.

[0059] Alternatively, the first circuit 40 can access and analyze the PWM signal provided to the load by the controller MCU. The higher the duty cycle of the PWM signal, the greater the load power level; and vice versa. In addition, alternatively, the controller MCU can directly inform the first circuit 40 which output power level the LED lighting device is at.

[0060] The present invention can be used with different handover configuration schemes, such as progressive handover or sequential handover.

[0061] The gradual switching is: each time an interruption of input power is detected, the configuration circuit gradually changes to the next setting in the setting sequence. When the current setting is the last setting in the sequence, the configuration circuit returns to the first setting of the sequence and starts again. For example, when the LED lighting device is powered on, the output is configured to 100%; each time it is interrupted, the configuration circuit reduces the output by 25%, in order of 100%, 75%, 50%, 25%, and 0% (standby). The next setting of 0% is 100% again, and it repeats.

[0062] The sequential switching is: the configuration circuit recognizes the interrupt sequence and configures the LED lighting device according to one of the multiple settings corresponding to the sequence. For example, a sequence with only one interruption (meaning that there is no interruption after the first interruption within a sufficiently long detection cycle) can be mapped to 100% output. A sequence of two consecutive interruptions (meaning that there is a second interruption after the first interruption within the detection cycle starting from the first interruption, and there is no interruption after the second interruption within the detection cycle starting from the second interruption) can be mapped to 75% output. A sequence of three interruptions is mapped to 50%; a sequence of four interruptions is mapped to 25%; a sequence of five interruptions is mapped to 0% (standby). A sequence of six consecutive interruptions can be mapped to reset the lighting device to factory defaults. In this case, assuming that the lighting device is at 50% output and the user wants to quickly change it to 100% output, the user can only toggle the switch once to enter a single interruption.

[0063] The control circuit may be implemented entirely in an MCU running firmware that performs the functions defined above. Alternatively, the control circuit may be implemented in whole or in part by discrete circuits, with the remainder (if any) being implemented by an MCU running firmware that performs the remaining functions. Those skilled in the art will appreciate that there are many ways to implement embodiments of the present invention.

[0064] The above embodiment uses LED lighting equipment as an example. The present application is not limited to this application. As long as the device needs to determine the interruption of input power, the present application can be used.

[0065] The input power is not limited to AC mains power, but may also be AC ​​power from an inverter powered by a DC power source (such as a solar panel or battery), or may be DC power from a DC power source powered by an AC power source or a DC power source. The DC power source powered by the AC power source may be similar to a low voltage 48V AC-DC power source powered by an AC mains power source, such as for a 48V track light system. The DC power source powered by the DC power source may be a DC-DC converter powered by a battery or a solar panel. In all of these applications, an interruption of the input power into the device may be used to command the device, and the present application may be used to determine the interruption.

[0066] By studying the drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments while practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0067] 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.

[0068] If the term "suitable for" is used in the claims or the specification, note that the term "suitable for" is intended to be equivalent to the term "configured to". If the term "device" is used in the claims or the specification, note that the term "device" is intended to be equivalent to the term "system" and vice versa.

[0069] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A control circuit for use with a device (40) having a power supply unit (PSU) adapted to be connected to and receive input power (AC) and to provide an output voltage (VBUS) to a power variable load (LED), the control circuit comprising: a detection circuit adapted to detect a drop in the output voltage (VBUS) and accordingly determine an interruption of the input power (AC), and a configuration circuit adapted to configure the device (40) according to the determined interruption of the input power (AC), It is characterized in that The detection circuit is suitable for: detecting a power level of the load (LED); determining the interruption of the input power (AC) if the output voltage (VBUS) drops below a first threshold value (Vth1) when the detected power level of the load is at a first level (25%), and determining the interruption of the input power (AC) if the output voltage (VBUS) drops below a second threshold value (Vth2) when the detected power level of the load is at a second level (50%); Wherein the first level (25%) and the second level (50%) are different, and the first threshold value (Vth1) and the second threshold value (Vth2) are different. 2 . The control circuit according to claim 1 , wherein the first level (25%) is smaller than the second level (50%), and the first threshold value ( Vth1 ) is higher than the second threshold value ( Vth2 ).

3. A control circuit according to claim 1 or 2, wherein the first threshold value (Vth1) and the second threshold value (Vth2) are determined so that when the input power (AC) is interrupted, the output voltage (VBUS) drops below the first threshold value (Vth1) for a certain duration (T) when the load is at the first level, and the output voltage (VBUS) drops below the second threshold value (Vth2) for substantially the same certain duration (T) when the load is at the second level.

4. The control circuit according to claim 1 or 2, wherein the detection circuit comprises: A comparison circuit (41) for comparing the output voltage (VBUS) with a reference, a first circuit (40) for detecting the power level of the load, and A second circuit (42) for setting the first threshold value (Vth1) or the second threshold value (Vth2) as the reference for the comparison circuit (41) according to the detected power level of the load.

5. The control circuit according to claim 4, wherein the first circuit (40) comprises: a current detector for detecting a current from the power supply unit to the power variable load, and processing circuitry for determining the power level of the load based on the detected current; Alternatively, said first circuit (40) comprises an interface to a controller of said device for receiving said power level of said load.

6. The control circuit of claim 1, wherein the configuration circuit is adapted to configure the device (40) into one of a plurality of settings based on a number of times an interruption in the input power is detected.

7. The control circuit according to claim 6, wherein the configuration circuit is adapted to: When the interruption is detected for the first time, starting to count the interruption; timing a period, and if an interruption occurs during the period, counting the interruption and restarting the timing and the counting; If no interrupt occurs in the last cycle, counting stops; as well as Based on the number of interruptions counted, the device is configured in the setting.

8. The control circuit of claim 1, wherein the configuration circuit is adapted to configure the device to a next setting in a sequence of settings each time the interruption of the input power is detected.

9. An LED driving device comprising a power supply unit (PSU) and a control circuit according to any one of claims 1 to 8.

10. An LED lighting device (40), comprising the LED driving device according to claim 9 and an LED lighting device (LED) as a variable load.

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