RC latch for a connected light bulb optimized for low standby power

Abstract

The present invention is a driver for driving a lighting load, comprising a rectifier adapted to receive an alternating current (AC) input voltage and to supply a rectified voltage, a converter adapted to convert the rectified voltage into an output voltage for the lighting load, a controller for controlling the converter and the switching element, and a latch circuit adapted to receive the AC input voltage or the rectified voltage, the latch circuit including a resistor, a capacitor and a series combination of the switching element, wherein the controller sets the converter to an active mode and a standby mode, and when the controller sets the converter to the active mode, the switching element is closed, and when the controller sets the converter to the standby mode, the switching element is opened.

Description

Technical Field

[0001] The present invention relates to a driver. The present invention further relates to an illumination system. The present invention further relates to a method.

Background Art

[0002] The awareness of the energy efficiency of lighting products has been increasing year by year. Hitherto, much attention has been paid to the efficiency of lamps in the active mode. New regulations require lamps to be more efficient. With the spread of radio wireless control LED lamps, the standby power of wireless LED lamps has received more attention. These lamps are controlled by a wireless switch, sensor or application and are always connected to the main power supply voltage. In a typical household, dozens of such wireless lamps may be found, and therefore, the energy consumption of these lamps in the standby mode may be quite important because the lamps are in the standby state for a significant amount of time during the day. Current laws require a standby power of less than 0.5 W, which may mean continuous standby power of several watts or more than 10 W in a household. In order to further reduce the energy consumption of lighting products, it is desirable to provide a further reduction in the standby power of lamps.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to provide a driver that requires less power during standby operation.

Means for Solving the Problems

[0004] In a first aspect of the present invention, there is provided a driver for driving an illumination load, a rectifier adapted to receive an alternating current (AC) input voltage and to supply a rectified voltage, A converter adapted to convert the rectified voltage into an output voltage for the lighting load; A controller for controlling the converter and the switching element; A driver having a latch circuit adapted to receive the AC input voltage or the rectified voltage, the latch circuit including a resistor, a capacitor and a series combination of the switching element; wherein the controller sets the converter to an active mode and a standby mode, closes the switching element when the controller sets the converter to the active mode, and opens the switching element when the controller sets the converter to the standby mode, is provided.

[0005] The driver has a converter that converts the AC input voltage into a voltage that can be used by the lighting load. The rectifier rectifies the AC voltage into a rectified voltage. The driver has a latch circuit that can be used to improve compatibility with a phase cut dimmer. The latch circuit also has a series connection of a resistor, a capacitor, and a switching element. The driver has a controller that is used to control the converter and the switching element. The controller can put the converter into an active mode and a standby mode. In the active mode, the converter may supply power adjusted to the lighting load. In the standby mode, the converter may be inactive, i.e., no power is supplied to the lighting load. The AC input voltage is supplied by the phase cut dimmer. The latch circuit supplies additional current when the phase cut dimmer becomes active, i.e., additional current is drawn when the voltage to the driver rises at the phase angle. This improves the compatibility of the driver with the phase cut dimmer. However, the latch circuit also provides additional losses. When the controller sets the converter to the standby mode, the latch circuit can also be disconnected. Therefore, the controller opens the switching element when the converter is set to the standby mode. The latch circuit draws no current at all, and therefore, the latch circuit dissipates no power at all. At this point, the phase cut dimmer may not operate properly, but since this operation is not visible to the user, this is no longer relevant. When the converter is set to the active mode, it is desirable to have compatibility with the phase cut dimmer; otherwise, this may be reflected in the light output of the lighting load, the switching element is closed, enabling the latch circuit to become active.

[0006] In a further example, the latch circuit is adapted to receive the AC input voltage, the latch circuit has a further rectifier, the switching element is a semiconductor direct current (DC) switch, coupled to the output of the further rectifier and configured to shunt the output of the further rectifier.

[0007] For improving the effect on the compatibility with the phase cut dimmer, the latch circuit may be arranged in front of the rectifier and coupled to the AC input voltage. A further rectifier may be provided to supply a rectified voltage to the switching element. In that case, the switching element may be a semiconductor that can operate safely only with a DC voltage, such as a MOSFET. Since the switching element is arranged within a DC operating regime and thus does not require any adaptation to AC voltage operation at all, the controller can supply a control signal to the switching element. In that case, the switching element is used to shunt the output of the further rectifier.

[0008] In a further example, the latch circuit is adapted to receive the AC input voltage and the switching element is a relay.

[0009] The relay provides galvanic isolation between the control input and the switching input. The relay may be any type of relay, such as an electromechanical relay or a solid state relay, for example. In this situation, a further rectifier is not required and the controller can supply a control signal directly to the control input.

[0010] In a further example, the driver further has an auxiliary power supply for powering the controller.

[0011] Preferably, an auxiliary power supply is provided to supply power to the controller. When the converter is in the standby state, it may still be desirable to continue to supply power to the controller. This allows the controller to receive and process information that may be used, for example, to set the converter to the active mode. The auxiliary power supply may only need to supply a small amount of power to the controller compared to the power that needs to be supplied to the lighting load. Further, in the standby mode, the phase cut dimmer may not operate properly, but this does not affect the power supply to the controller.

[0012] In a further example, the input of the auxiliary power supply is coupled to the switching element, and the auxiliary power supply is configured to provide a conduction path for current to flow through the resistor and the capacitor when the switching element is open.

[0013] The auxiliary power supply may receive its power through the resistor and capacitor of the latch circuit. Therefore, the switching element needs to be opened so that the auxiliary power supply can provide a conduction path for current to flow at least through the capacitor. In that case, this current is used by the auxiliary power supply to supply an auxiliary output voltage that can be used, for example, by the controller. The auxiliary power supply provides a conduction path when the switching element is open.

[0014] In a further example, the driver further has a phase cut dimmer detection circuit adapted to detect the presence of a phase cut in the AC input voltage.

[0015] It may be desirable to detect the presence of a phase cut dimmer. This may enable the implementation of additional functions, such as enabling phase cut dimming or determining the type of phase cut dimmer.

[0016] In a further example, the controller is further configured to close the switching element in the active mode when the phase cut dimmer detection circuit detects a phase cut in the AC input voltage.

[0017] To reduce power loss during operation of the driver and when the converter is active, when the phase cut dimmer is detected, the switching element can be closed when the controller sets the converter to the active mode. If the phase cut dimmer is not detected, the latch circuit may not be required. Therefore, it is desirable to close the switch only when the phase cut dimmer is detected and the converter is active.

[0018] In a further example, the controller is configured to receive a wireless control command for controlling the converter. The controller may receive a control command for controlling the converter and, therefore, may also receive a control command for controlling the light generated by the lighting load. Preferably, the control command is transmitted wirelessly, which provides easy communication between remote control devices such as mobile phones or remote control units. When the converter is in the standby state, the controller may still receive the wireless control command.

[0019] In a further example, the converter is a switch mode power supply.

[0020] The converter may be a switch mode power supply (SMPS) that can be easily set to the active mode and the standby mode. Further, the SMPS is very energy efficient and is therefore desirable for use in lighting applications.

[0021] In a further example, the auxiliary power supply is a switch mode power supply.

[0022] Similar to the converter, it is desirable to make the auxiliary power supply an SMPS. Since the auxiliary power supply only needs to supply a relatively small amount of power compared to the converter, the auxiliary power supply can be relatively small.

[0023] In another example, there is provided a lighting system having a driver according to the present invention and the lighting load.

[0024] Preferably, the driver is part of the lighting system. The introduced driver enhances the energy efficiency of the entire lighting system.

[0025] In another example, the lighting load is a solid-state lighting load.

[0026] The solid-state lighting load requires a small amount of power compared to conventional lighting loads. The reduction in power consumption of the driver already has a significant impact on the total power consumption of the lighting system. The solid-state lighting load can be, for example, any of an LED, a laser diode, or a vertical-cavity surface-emitting laser (VCSEL).

[0027] In another example, a converter adapted to convert a rectified voltage into an output voltage for a lighting load, a controller for controlling the converter and the switching element, a method for controlling a driver having a latch circuit adapted to receive an AC input voltage or the rectified voltage, the latch circuit including a series combination of a resistor, a capacitor, and the switching element, the method including: setting the converter to an active mode; setting the converter to a standby mode; when the converter is in the active mode, closing the switching element, or when the converter is in the active mode and a phase cut is detected, closing the switching element; When the converter is in the standby mode, a method is provided that includes the step of opening the switching element.

[0028] The method enables controlling the driver according to the present invention by setting the converter to the active mode and the standby mode. When the converter is in the active mode, the switching element is closed, and when the converter is in the standby mode, the switching element is opened.

Brief Description of the Drawings

[0029] Here, examples of the present invention will be described with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0030] The present invention will be described with reference to the figures.

[0031] The detailed description and specific examples illustrate exemplary embodiments of the apparatus, system, and method, but are for illustrative purposes only 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 from the following description, the appended claims, and the accompanying drawings. It is to be understood that the figures are merely schematic and are not drawn to scale. It is also to be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0032] FIG. 1 shows a driver known from the prior art. The driver is coupled to a phase cut dimmer that provides a phase cut at the main power supply voltage. A rectifier 5 rectifies the AC input voltage and is used to supply a rectified voltage between the outputs of the rectifier 5. The rectified voltage is supplied to a converter 1. The converter 1 converts the rectified voltage into an output voltage coupled to the lighting load LED. A controller 3 is provided to control the converter 1. The controller 3 can set the converter 1 to an active mode and a standby mode. A latch circuit is used to improve the compatibility between the driver and the phase cut dimmer. When the phase cut dimmer is active, a sudden rise in the input voltage occurs. This is the rising edge of the input voltage. At this instant, the triac in the phase cut dimmer is closed. In order for the triac to close properly, a large current, also known as the latch current, is required at the instant the triac closes. If the current is too low, the triac may open again, and no voltage is supplied to the driver, which may result in unstable output power. The latch circuit has a series combination of a resistor R1 and a capacitor C1 that draws current at the highest instant when the triac turns on. This additional current enables the triac to start properly. When the converter 1 is in the standby mode, the latch circuit remains active, and therefore, power is also lost in the latch circuit.

[0033] Figure 2 shows another example of a driver as known in the state of the art. The basic structure of the driver is the same as that of the driver in Figure 1. The latch circuit is arranged after the rectifier 5 and is coupled to the rectified voltage. The latch circuit still performs the same function, but has a low effect of supplying the latch current and the holding current to the triac dimmer.

[0034] Figure 3 shows an example of a driver according to the present invention. The driver has a rectifier 5 that rectifies an AC input voltage and supplies a rectified voltage at the output of the rectifier 5. The rectified voltage is supplied to a converter 1. The converter converts the rectified voltage into an output voltage that is supplied to the lighting load LED. A controller 3 is used to control the converter 1. The controller 3 is configured to set the converter 1 to an active mode and a standby mode. When the converter 1 is in the active mode, the output voltage can be supplied to the lighting load LED so that the lighting load LED is powered. When the converter 1 is in the standby mode, the converter 1 does not supply the output voltage to the lighting load LED, thereby preventing the lighting load LED from emitting light. In the example shown, the latch circuit 4 has a series combination of a resistor R1, a capacitor C1, and a switching element M1. The latch circuit 4 is arranged at the output of the rectifier 5 and receives the rectified voltage. The controller 3 supplies a control signal to the switching element M1. When the converter 1 is set to the active mode, the controller 3 supplies a control signal for closing the switching element M1. When the converter 1 is active, the latch circuit is also active. As long as the phase cut dimmer operates properly, the converter 1 can supply an appropriately adjusted output voltage to the lighting load LED. When the converter 1 is in the standby state, the controller 3 supplies a control signal for opening the switching element M1 to the switching element M1. When the converter 1 is not active, for example, in the standby state, its compatibility with the phase cut dimmer is no longer relevant. Therefore, the latch circuit 4 is disconnected by opening the switching element M1 so that current cannot flow through the resistor R1 and the capacitor C1. There is no power loss in the latch circuit 4 during standby of the converter 1. The arrangement of the latch circuit 4 in the DC path coupled to the rectified voltage has the advantage that the switching element M1 can be easily controlled. The control signal supplied by the controller 3 can be directly coupled to the switching element M1. In this example, the switching element can be any type of switching element that can be controlled by an electrical signal.Examples of such a switching element M1 can be semiconductor switches such as MOSFETs, IGBTs or bipolar transistors.

[0035] Figure 4 shows another example of a driver. The driver has similar characteristics to the driver of Figure 3. The latch circuit 4 is arranged in front of the rectifier 5 and coupled to the AC input voltage. The resistor R1 and the capacitor C1 may be the same as the resistor and capacitor as shown in Figure 3. However, for the circuit to function properly, the capacitor C1 needs to be divided into two parts, C1 and C1', as shown in Figure 4. This is because of the fact that the rectifier 5 and the further rectifier 6 share the same ground. The capacitor C1' prevents a DC path that could result in a high current due to the phase difference between the two rectifiers. The switching element M1 is coupled to the resistor R1 and the capacitors C1, C1' via the further rectifier 6. The further rectifier supplies another rectified voltage at its output. The switching element M1 is coupled between the outputs of the further rectifier 6 such that the output of the further rectifier 6 is shunted when the switching element M1 is closed. The use of the further rectifier 6 enables the control of the switching element 6 in the same way as the switching element M1 as shown in Figure 3. The controller 3 can supply a control signal to the switching element M1.

[0036] Figure 5 shows another example of a driver. The driver has similar characteristics to the drivers of Figures 3 and 4. The latch circuit 4 is arranged in front of the rectifier 5 and is coupled to the AC input voltage. The resistor R1 and the capacitor C1 may be the same as the resistor and capacitor as shown in Figures 3 and 4. The switching element U1 is a relay having an input for a relay control signal and a relay switching element that can be opened and closed based on the relay control signal. The input for the relay control signal is galvanically isolated from the relay switching element. This allows the relay switching element to be directly coupled to the resistor R1 and the capacitor C1. The input for the relay control signal is directly coupled to the controller 3 and can receive the control signal. The relay can operate in a similar manner to the switching element shown in Figures 3 and 4. When the relay switching element is closed, the latch circuit 4 is operable. When the relay switching element is open, the latch circuit 4 is not operable. Examples of relays are electromechanical relays and solid-state relays.

[0037] In the example shown, an auxiliary power supply 2 may be provided to supply power to the controller 3. The auxiliary power supply 2 may remain active when the converter 1 is in the standby mode. This allows the controller 3 to continue to be powered even when the converter 1 is in the standby state. In that case, the controller 3 can still transmit and receive information that can be used to control the driver.

[0038] In FIG. 6, an example of a driver in which the auxiliary power supply 2 is coupled to the switching element M1 is shown. The switching element M1 is connected in the same manner as the switching element shown in FIG. 4. The switching element M1 is coupled to the resistor R1, the capacitor C1, and the capacitor C1' via a further rectifier 6. The further rectifier supplies another rectified voltage at its output. The switching element M1 is coupled between the outputs of the further rectifier 6 such that the output of the further rectifier 6 is shunted when the switching element M1 is closed. The use of the further rectifier 6 makes it possible to control the switching element 6 in the same manner as the switching element M1 as shown in FIG. 3. The controller 3 can supply a control signal to the switching element M1. The auxiliary power supply 2 is coupled across the switching element M1. This means that the switching element M1 also shunts the input of the auxiliary power supply 2 when the switching element M1 is closed. When the switching element M1 is open, the converter 1 is in the standby mode, and the voltage across the switching element M1 is supplied to the auxiliary power supply 2. In this example, the latch circuit 4 can perform a different function when the converter 1 is in the standby mode, i.e., provide a low-power path to the auxiliary power supply 2. When the converter 1 is active and the switching element M1 is closed, the auxiliary power supply 2 can be powered via another power source. The converter 1 can supply power to the auxiliary power supply 2, for example, via an auxiliary winding of the transformer / inductor of the converter 1. In other examples, when the converter 1 is active, the switching element M1 may be open, in which case the auxiliary power supply 2 can receive current from the resistor R1 and the capacitor C1 such that the latch circuit 4 remains operable during the active mode of the converter 1. In that case, the switching element M1, in combination with the circuit within the auxiliary power supply 2 that enables the latch circuit 4 to be active, can be regarded as the switching element M1 according to the present invention that opens and closes based on a control signal from the controller 3.

[0039] Figure 7 shows a method for controlling a driver according to the present invention. The driver can be any of the drivers shown and described in FIGS. 3, 4, 5, and 6. The method has a step of turning on the driver at startup. This can be, for example, when the input voltage is supplied for the first time. When turning on the driver or immediately after turning on the driver, the latch circuit 4 is turned on. This is done by closing the switching element M1. After the operation of the latch circuit 4, the lamp is turned on by turning on the converter 1, and power is supplied to the lighting load LED so that light is generated. When the lighting load LED is turned off, i.e., when the converter 1 is set to the standby mode, the latch circuit 4 is disconnected by opening the switching element M1. Further, the circuit detects whether a dimmer exists. As long as the lighting load LED is not turned off and a dimmer is detected, the latch circuit 4 remains active, i.e., the switching element M1 remains closed.

[0040] The driver is preferably used in an illumination system. The illumination system has the driver and the lighting load LED. Preferably, the lighting load LED is a solid-state lighting load.

[0041] The illumination system can be connected to a phase-cut dimmer. In the example shown, the illumination system needs to be adapted to the phase-cut dimmer, which means that during the operation of the lighting load LED, the phase-cut dimmer needs to operate properly, preferably without any faults. The driver provides the active latch circuit 4 when the converter 1 is active and the lighting load LED is powered. When the illumination system enters the standby state, the converter 1 is in the standby state and the lighting load LED is turned off. In that case, the latch circuit 4 is also turned off so that the standby power of the illumination system is kept as low as possible.

[0042] In the example shown, the auxiliary power supply 2 and / or the converter 1 may be a switched-mode power supply. Examples of switched-mode power supplies are boost converters, buck converters, buck-boost converters, flyback converters, and LLC converters.

[0043] In the example shown, the driver may have a phase-cut dimming detector circuit. The phase-cut dimming detector circuit can detect the phase cut in the AC input voltage. This detection can be further used to close the switching element M1 based on the detection of the phase-cut dimming device. If there is no phase-cut dimming device, in order to provide a more energy-efficient driver, the driver does not require the active latch circuit 4 when the converter 1 is active. Therefore, the switching element M1 can only be closed when the converter 1 is active and a phase-cut dimming device is detected.

[0044] Those skilled in the art can understand and achieve other modifications to the disclosed embodiments from the study of the drawings, the description, and the appended claims in the implementation of the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the singular form does not exclude the plural. Merely the fact that certain means are recited in mutually different dependent claims does not indicate that these means cannot be used advantageously in combination. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. It is a driver for driving lighting loads. A rectifier adapted to receive an AC input voltage and to supply a rectified voltage, A converter adapted to convert the rectified voltage into an output voltage for the lighting load, A controller configured to control the converter and the switching element, A driver comprising a latch circuit adapted to receive the aforementioned AC input voltage or the aforementioned rectified voltage, the latch circuit including a series combination of a resistor, a capacitor and the switching element, The aforementioned controller The converter is set to active mode and standby mode, When the controller sets the converter to the active mode, the switching element is closed. A driver configured to open the switching element when the controller sets the converter to the standby mode.

2. The driver according to claim 1, wherein the latch circuit is adapted to receive the AC input voltage, the latch circuit has a further rectifier, the switching element is a semiconductor DC switch coupled to the output of the further rectifier and configured to shunt the output of the further rectifier, and the capacitor is configured as two separate capacitors, each connected to one of the input terminals of the further rectifier.

3. The driver according to claim 1, wherein the latch circuit is adapted to receive the AC input voltage, and the switching element is a relay.

4. The driver according to claim 1, further comprising an auxiliary power supply for supplying power to the controller.

5. The driver according to claim 4, wherein the input of the auxiliary power supply is coupled to the switching element, and the auxiliary power supply is configured to provide a conductive path for current to flow through the capacitor when the switching element is open.

6. The driver according to any one of claims 1 to 5, further comprising a phase-cut dimmer detection circuit adapted to detect the presence of a phase cut in the AC input voltage.

7. The driver according to claim 6, wherein the controller is further configured to close the switching element in the active mode when the phase cut dimmer detection circuit detects a phase cut in the AC input voltage.

8. The driver according to claim 1, wherein the controller is configured to receive wireless control commands for controlling the converter.

9. The driver according to claim 1, wherein the converter is a switch-mode power supply.

10. The driver according to either claim 4 or 5, wherein the auxiliary power supply is a switch-mode power supply.

11. A lighting system comprising a driver according to any one of claims 1 to 5 and the lighting load.

12. The lighting system according to claim 11, wherein the lighting load is a solid-state lighting load.

13. A converter adapted to convert a rectified voltage into an output voltage for a lighting load, A controller for controlling the converter and switching elements, A method for controlling a driver having a latch circuit adapted to receive an AC input voltage or the rectified voltage, the latch circuit including a series combination of a resistor, a capacitor and the switching element, The steps include setting the converter to active mode, The steps include setting the converter to standby mode, When the converter is in the active mode, the switching element is closed, or when the converter is in the active mode and a phase cut is detected, the switching element is closed. A method comprising the step of opening the switching element when the converter is in the standby mode.

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