JP2019091727A - Dimmable lighting system - Google Patents

Abstract

To provide a lighting system for operation with a dimmer circuit 1 including a triac TR1 connected to a load.SOLUTION: A load includes a driver circuit for supplying current to a light source including one or more LEDs (LED 1 to 4). The current is determined at least in a part by an adjusted set-point value. A system further includes a set-point filter circuit 20 for obtaining a dimmer set-point value 21 determined at least in a part by setting of the dimmer circuit 1, and for generating an adjusted set-point value 24. Sensitivity of the adjusted set-point value for change in the dimmer set-point value is low at low values of the dimmer set-point value.SELECTED DRAWING: Figure 1

Description

 The present invention relates to a dimmer triggering circuit for low load applications, such as, for example, LED based light sources. The invention further relates to a dimmer system comprising such a dimmer trigger circuit.

 In general, a phase-controlled dimmer also has an AC triode, also called a triac. A triac is a bi-directional switch that can flow current in either direction when triggered or turned on. It can be triggered by applying a positive or negative voltage to the gate electrode, ie a small current is applied to its gate. This current only needs to be supplied for a short time, ie, on the order of microseconds. In other words, the triac needs to be triggered or "fired". Once triggered, the device will continue to conduct until the current through it has dropped below some threshold, such as the end of the half cycle of the alternating current (AC) mains supply (also referred to as the zero crossing) . As a result, after that, the TRIAC "turns off".

 These dimmers work well to dim incandescent bulbs that carry relatively high currents. Various problems are encountered when these dimmers are used with smaller loads, such as light sources based on light emitting diodes (LEDs). This is a particular problem when replacing a standard incandescent bulb with an LED retrofit bulb, in the situation where a conventional TRIAC dimmer is installed for use with the bulb.

 The LED light source may not draw enough current to allow the TRIAC in the dimmer to turn on as needed, resulting in inability to dim the light or dimmer instability Make it work. The small resistive load of the dimmer may result in less than accurate dimming operation and cause voltage oscillations at the dimmer output caused by the multiple firings of the triac. At low dimmer settings, the LED drive circuit may cause a short flash of light from the LED light source to toggle on and off. Furthermore, the human eye senses the light intensity according to a logarithmic curve as a whole, whereas the LED has a nearly linear response, and the intensity of the light emitted is approximately proportional to the current flowing through the LED . When operated with a conventional dimmer, the LED light source will not appear to be smooth and dark. Also, the change in sensed intensity is not directly related to the dimmer knob position. Small changes in the supply voltage may result in noticeable flickering of the light emitted by the LED light source.

 The present invention seeks to solve these problems in various ways according to various embodiments. According to an aspect, the invention relates to a lighting system for cooperating with a dimmer circuit having a triac connected to a load. The load has a drive circuit that supplies current to a light source having one or more LEDs. The current is at least partially determined by the adjusted setpoint value. The system further comprises a setpoint filter circuit that obtains a dimmer setpoint value determined at least in part by the settings of the dimmer circuit and generates an adjusted setpoint value. The sensitivity of the adjusted setpoint value to changes in the dimmer setpoint value is low at low values of the dimmer setpoint value.

 The setpoint filter circuit may be configured to increase the adjusted setpoint with a low proportion of low value of dimmer setpoint value and a high proportion of high value of dimmer setpoint value. The change in adjusted setpoint value in response to a change in dimmer setpoint value desirably approximates an exponential response. The setpoint filter circuit desirably generates a full range of adjusted setpoint values less than the full range of dimmer setpoint values, and desirably, a adjusted setpoint value having a minimum value greater than 0. Generate

 The setpoint filter circuit has a first substantially constant value in a first portion of the range of dimmer setpoint values and is low in a second portion of the range of dimmer setpoint values Increase in proportion and increase in high proportion during the third part of the range of dimmer setpoint values, and second substantially constant value during the fourth part of the range of dimmer setpoint values And may be configured to generate adjusted set points.

 The set point filter circuit may further include a second or higher order low pass filter for filtering the received dimmer set point value. The set point filter circuit may include a differential amplifier that generates an intermediate set point value. It controls the transistor to generate an adjusted setpoint value.

 The drive circuit may be designed with a voltage control circuit and a current control circuit. The voltage control circuit controls the voltage at the output of the drive circuit according to the voltage set point. The current control circuit corrects the voltage setpoint according to the current setpoint. The current control circuit may be designed to operate within a predetermined range. The voltage set point is maintained at the boundary value when the current control circuit is at the boundary of its operating range.

 The setpoint filter circuit may derive the dimmer setpoint value from the voltage at the output terminal of the dimmer circuit. Alternatively, the setpoint filter circuit may derive the dimmer setpoint value from the dimmer triac firing angle. The dimmer setpoint value may be derived from the time delay between the triac's first trigger and the zero crossing of the supply voltage after the zero crossing point.

 The lighting system may further include a dimmer trigger circuit for triggering of the dimmer triac. The dimmer setpoint value is at least partially determined by the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimmer trigger circuit or voltages associated with the rising and falling edges May be determined. Thus, the dimmer setpoint value is at least partially determined by the time delay between the rising and falling edges of the current flowing through the dimmer trigger circuit, or the voltage associated with the rising and falling edges. It may be determined. The lighting system of the present invention may be designed to operate when the current through the dimmer circuit is less than the holding current of the dimmer triac when the dimmer triac is on.

 The lighting system may further include a dimmer trigger circuit for triggering of the dimmer triac. The dimmer trigger circuit is configured to detect a voltage level detector for detecting whether the input voltage of the dimmer trigger circuit is less than a threshold, and a current when the voltage detected by the voltage level detector is less than the threshold. It may include a bipolar current source circuit that is supplied and otherwise deactivated. The lighting system may be designed such that the maximum current due to the dimmer trigger circuit is less than the holding current of the dimmer triac. When the dimmer triac is on or the dimmer triac is off, the current through the dimmer trigger circuit is less than the holding current of the triac. The dimmer trigger circuit is designed to consume less than 100 mW of average power in operation.

 In another aspect, the invention is used in a lighting system having a triac dimmer circuit, a light source having one or more LEDs, and a drive circuit for supplying current to one or more LEDs. The present invention relates to a set point filter circuit. The current is at least partially determined by the adjusted setpoint value. The setpoint filter circuit has an input circuit for obtaining a dimmer setpoint value determined at least in part by the setting of the dimmer circuit, and an adjusting circuit for generating the adjusted setpoint value. . The sensitivity of the adjusted setpoint value to changes in the dimmer setpoint value is low at low values of the dimmer setpoint value.

 The setpoint filter circuit may be designed to increase the adjusted setpoint at a low percentage of low value of dimmer setpoint value and a high percentage of high value of dimmer setpoint value. Also, changes in the adjusted set point value in response to changes in the dimmer set point value may approach an exponential response. The adjustment circuit may be configured to generate a full range of adjusted setpoint values less than the full range of dimmer setpoint values, or a adjusted setpoint value having a minimum value greater than 0. It may be configured to generate. The input circuit may have a second or higher order low pass filter for filtering the received dimmer setpoint value. The adjustment circuit may have a differential amplifier that generates an intermediate setpoint value. It controls the transistor to generate an adjusted setpoint value.

The setpoint filter circuit may derive the dimmer setpoint value from the voltage at the output terminal of the dimmer circuit. The dimmer setpoint value may be derived from the start angle of the dimmer triac. Also, this may be achieved by deriving the dimmer setpoint value from the time delay between the triac's first trigger and the zero crossing of the supply voltage after the zero crossing point.

 In yet another aspect, the invention relates to a lighting system for cooperating with a dimmer circuit having a triac. The system comprises: a light source having one or more LEDs; a load having a dimmer trigger circuit for triggering the dimmer triac and a drive circuit for supplying current to the one or more LEDs. Have. The current supplied by the drive circuit is at least partially determined by the dimmer setpoint value. The dimmer setpoint value is derived at least in part from the start angle of the dimmer triac.

 The drive circuit desirably derives the dimmer setpoint value from the time delay between the triac's first trigger and the zero crossing of the supply voltage after the zero crossing point. The dimmer setpoint value is at least partially determined by the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimmer trigger circuit or voltages associated with the rising and falling edges May be determined. The dimmer setpoint value is at least partially determined by the time delay between the rising and falling edges of the current flowing through the dimmer trigger circuit or the voltage associated with the rising and falling edges. May be

 The drive circuit may include a voltage control circuit and a current control circuit. The voltage control circuit controls the voltage at the output of the drive circuit by the voltage set point. The current control circuit corrects the voltage setpoint by the current setpoint. The current control circuit desirably operates within a predetermined range. The voltage set point is maintained at the boundary value when the current control circuit is at the boundary of its operating range. The lighting system may be configured such that the current through the dimmer circuit when the dimmer triac is on is less than the holding current of the dimmer triac. The maximum current due to the dimmer trigger circuit may be less than the holding current of the dimmer triac. The lighting system may be configured such that the current through the dimmer trigger circuit is less than the holding current of the triac when the dimmer triac is on and the dimmer triac is off. The lighting system may comprise a setpoint filter circuit for generating adjusted setpoint values from the dimmer setpoint values. The sensitivity of the adjusted setpoint value to changes in the dimmer setpoint value is low at low values of the dimmer setpoint value.

 A further aspect of the invention relates to a lighting system for cooperating with a dimmer circuit having a triac. The system comprises: a light source having one or more LEDs; a load having a dimmer trigger circuit for triggering the dimmer triac and a drive circuit for supplying current to the one or more LEDs. Have. The drive circuit has a power factor correction circuit. The current supplied by the drive circuit is at least partially determined by the dimmer setpoint value. The dimmer setpoint value is derived at least in part from the start angle of the dimmer triac.

FIG. 1 schematically shows a conventional dimmer connected to an incandescent lamp. FIG. 2A is a diagram of a waveform example of an AC applied voltage through the dimmer circuit. FIG. 2B is a diagram of an example waveform of voltage across dimmer loads of different dimmer settings. FIG. 2C is a diagram of an example waveform of voltage across dimmer loads of different dimmer settings. FIG. 3 is a schematic view of a lighting system according to an embodiment of the invention that includes a dimmer trigger circuit connected to an LED light source. FIG. 4 is a schematic diagram showing additional details of a dimmer trigger circuit used in a lighting system according to an embodiment of the present invention. FIG. 5 is a schematic diagram of another embodiment of a dimmer trigger circuit. FIG. 6 is a simplified circuit diagram of an embodiment of a dimmer trigger circuit. 7A is a diagram of voltage-current operation across the terminals of the dimmer trigger circuit of FIG. 6; FIG. 7B is a diagram of voltage-to-current operation between terminals of an embodiment of a dimmer trigger circuit including a microprocessor. FIG. 8 is a simplified circuit diagram of an embodiment of a set point filter circuit. FIG. 9A is a diagram showing an example of the change of adjusted set point with two slopes. FIG. 9B is a diagram showing an example of the change of the adjusted set point approximating the exponential response. FIG. 10 is a simplified circuit diagram of the secondary side of an embodiment of the LED drive circuit. FIG. 11A is a diagram of an example of a dimmer output voltage when the dimmer triac current is on the holding current of the triac. FIG. 11B is a diagram of an example of the dimmer output voltage when the dimmer triac current is discontinuous or less than or equal to the holding current of the triac. FIG. 6 is a simplified circuit diagram of the second stage of another embodiment of the LED drive circuit.

 The following is a description of one embodiment of the present invention given by way of example only. FIG. 1 schematically shows a conventional dimmer 1 connected to a load 3, typically an incandescent bulb. The dimmer 1 includes a series-connected variable resistor R1 and a triac TR1 connected in parallel with a capacitor C1. In this description, the combination of resistor R1 and capacitor C1 will be referred to as an RC circuit or a timer circuit. In addition, the dimmer has a trigger component (ie a component suitable for triggering the triac TR1). In general, diodes for alternating current (diacs) are used for this purpose. A diac is a bi-directional trigger diode that conducts current after exceeding a diac threshold voltage called a diac trigger voltage. The diac continues to conduct. On the other hand, the current flowing therethrough is maintained above the threshold current. If the current decreases below the threshold current, the diac changes to a high resistance state. These characteristics are well adapted as trigger switches for triacs.

 The dimmer 1 of FIG. 1 has a diac D1. The diac D1 is connected between the variable resistor R1 and the capacitor C1 at a first end, and is connected to the gate of the triac TR1 at a second end. The dimmer 1 has two terminals (ie, terminals T1 and T2). The dimmer 1 and its load 3 are connected in series through an AC power supply.

 As mentioned above, if the current through the triac TR1 drops below its threshold, the triac TR1 turns off. Once the zero crossing of the AC power supply has passed, the RC circuit will "see" the actual AC power supply voltage and charge C1. Note that this charging current flows further through the incandescent bulb 3. Once the voltage through C1 reaches the trigger voltage of diac D1, diac D1 begins to source and supply current to the gate of TR1. On the other hand, the capacitor C1 discharges. As a result, the triac TR1 triggers and turns on. Current begins to flow through the triac TR1. The capacitor C2 is discharged.

 By adjusting the resistance of R1 (eg, by operating the dimmer knob or potentiometer), the time required to reach the diac trigger voltage through C1 can be set. The higher value of resistor R1 will result in a longer time required to reach the diac trigger voltage on C1. Therefore, the conduction interval of the TRIAC TR1 will be short. It will be understood by adjusting the time that the current is flowing through the TRIAC TR1. It is possible to adjust the power supplied to the light bulb 3, that is, its illuminance.

 Components may be added to the basic dimmer circuit described above for filtering of the electromagnetic interference (EMI) generated by the switching of the TRIAC TR1. For example, capacitor C2 may be included via inductor L1 connected in series to TRIAC TR1 and TRIAC TR1. These additional components are useful to reduce EMI, and capacitor C2 through the triac flows through dimmer 1 (and load 3) to charge capacitor C1 and trigger the triac It will increase the current you command. This is because this current must charge both capacitors C1 and C2.

 FIG. 2A is a diagram showing a waveform of an AC applied voltage through the dimmer 1 through the terminals T1 to T3. FIGS. 2B and 2C show the waveforms of the voltage developed across the load (terminals T2-T3), with resistive switch 3 and different dimmer settings of variable resistor R1. The AC applied voltage becomes zero at the zero crossing point t0 of a half cycle. At this point, the TRIAC stops conducting and the voltage across the load 3 is close to zero. The voltage across the load 3 is not exactly zero since some current (eg, the current that charges the capacitors C1 and C2) continues to flow through the series connected dimmer 1 and load 3.

 As shown in FIG. 2B, at time t1, the capacitor C1 becomes fully charged, triggering the diac D1, which in turn triggers the triac TR1. The voltage across load 3 rises substantially to the supply voltage, and the current through load 3 increases significantly. If the load is high enough, the TRIAC continues to survive until the next zero crossing point t0. Thus, during each half cycle period A, the triac is off and the capacitor C1 is charging. The charging rate of C1 and the length of time of period A depend on the dimmer setting, ie the resistance of the variable resistor R1 as set by the dimmer knob. During period B, the TRIAC turns on, the load 3 is connected via the supply voltage, and normal operating current is flowing through the dimmer and the load. As seen by the waveform in FIG. 2B, the average voltage during each half cycle shrinks slightly, resulting in a small decrease in current flowing through the resistive load. It is visible as slight dimming when the load is a light valve.

 In FIG. 2C, the dimmer setting is changed to increase the resistance of variable resistor R1, which further darkens the light. At time t2, the capacitor C1 is fully charged, triggering the diac D1 and the triac TR1. The triac continues to survive until the next zero crossing point t0. Therefore, during a long period C, the triac turns off, and during a short period D, the triac turns on. Thus, for each half cycle, the waveform of FIG. 2C has an average voltage. It can be seen as a large amount of dimming when the load is a light valve, which is greatly reduced, resulting in a large reduction in the current flowing through the load. It can be seen that the dimmer performs phase control by adjusting the delay after a zero crossing after the triac turns on, which is referred to as the triac's starting angle.

 If the TRIAC is off and they are used to dim a load, such as an incandescent bulb, which exhibits a sufficiently high load and produces a sufficient current, when charging the capacitors C1 appropriately, A dimmer such as dimmer 1 functions properly. That is, after the zero crossing of the supply voltage, the current flowing through the load needs to be high enough to allow charging of the capacitor C1 in the RC circuit (and C2). If a high enough current does not flow through Load 3, the triac TR1 will not trigger at all or will not trigger only if the dimmer knob is set so that the resistance of R1 is low enough . A typical result is that the dimming function of the dimmer 1 does not work, ie the light may not get dark.

 A load such as an incandescent lamp of sufficient power provides a current path to charge the RC circuit as a condition for the dimmer 1 to function properly. Recently, however, there are low load and discontinuous applications (e.g. built-in rectifiers and capacitors) that do not provide enough current to enable the proper functioning of the dimmer 1. That is, after the zero crossing of the supply voltage, there is insufficient current through the load for proper charging of the RC circuit.

 A well-known example of low load applications is an LED light source that includes an electronic coupling circuit that drives one or more light emitting diodes (LEDs) that require DC current. The LED circuit 13 generally comprises one or more LEDs, a rectifier and one or more smoothing capacitors, and thus may be a discontinuous load. In this description, embodiments of the present invention will be further described in combination with LED circuits. However, embodiments of the present invention allow other low load or discontinuous load applications (i.e., a dimmer such as dimmer 1 schematically illustrated in FIG. 1 to function properly). It should be understood that it may be used in conjunction with an application that can not supply the necessary charging current to the RC timer circuit of the dimmer. The load that keeps the rectifier front end with a smoothing capacitor can be considered as a discontinuous load application.

 FIG. 3 schematically shows a dimmer system 10 according to an embodiment of the invention connected to an LED circuit 13. The dimmer system comprises a dimmer 1 and a dimmer trigger circuit (DTC) 12 connected in series via an AC applied voltage. The LED circuit 13 is connected in series to the dimmer 1 and connected in parallel to the DTC 12. The combination of loads such as the DTC 12 and the LED circuit 13 may be referred to as a dimmable device.

 4 and 5 schematically show the DTC 12 in more detail. The DTC 12 has a voltage level detector 15 and a bipolar current source circuit 18 including a current source circuit 17 and a rectifier 19. The voltage level detector 15 is connected to the current source circuit 17. Both the voltage level detector 15 and the current source circuit 17 are connected to the DC terminal of the rectifier 19.

 The voltage level detector 15 is arranged to detect whether the absolute value of the voltage difference between the terminals T2 and T3 (ie the output of the rectifier 19) is below a threshold. Bipolar current source circuit 18 is arranged to be activated if the voltage detected by voltage level detector 15 is maintained below the threshold value, or otherwise deactivated. Thus, the bipolar current source circuit 18 in the DTC 12 is a voltage dependent current source. Also, the DTC 12 as a whole can be considered to act as a bipolar voltage-dependent current source. Such DTC 12 can be designed to consume an average power of less than 100 mW, as described in more detail below. In embodiments of the good aspect, the DTC 12 may consume an average power of 10-50 mW. Desirably, the consumption of DTC 12 is approximately 30 mW. Many conventional dimmers of such consumption can operate as intended.

 The voltage level detector 15 may have a microprocessor. The microprocessor is arranged to detect whether the absolute value of the input voltage of the dimmer trigger circuit 12 is below a threshold. If the input voltage of the dimmer trigger circuit 12 is below the threshold value, the microprocessor may provide a signal that commands the bipolar current source circuit 18 to supply current. In some embodiments, as described in more detail in FIG. 5B, the microprocessor may command the bipolar current source circuit 18 to supply current after the zero crossing of the input voltage.

 Voltage level detector 15 may include a comparator to detect whether the rectified input voltage is below a threshold. The comparator comprises two inputs and one output, as schematically shown in FIG. The first input is connected to a reference potential, ie a potential equal to the threshold (30 V in this example). The second input is arranged to receive the input voltage of the dimmer trigger circuit 12. If the input voltage of the dimmer trigger circuit 12 at the second input of the comparator is less than the threshold of the first input of the comparator, the output of the comparator is a current such as the bipolar current source circuit 18 discussed above. May be supplied. An operational amplifier or voltage comparator may be used to implement the comparator as would be understood by one skilled in the art.

 The rectifier 19 has an AC side (ie, terminals connected to terminals T2 and T3 respectively) and a DC side (ie, the other in DTC 12 such as current source circuit 17 in voltage level detector 15 and bipolar current source circuit 18). And a terminal connected to the reference potential. Voltage level detector 15 and current source circuit 17 form a unipolar circuit. The rectifier 19 is arranged to allow the current generated by the current source circuit 17 to be supplied to the dimmer as a bipolar current.

 The DTC 12 allows the dimmer 1 to work as if it were loaded by a regular incandescent light bulb. If the AC applied voltage is sufficiently low, that is, less than the above-mentioned threshold, the DTC 12 is activated to allow sufficient current to flow into the RC circuit of the dimmer 1. If the AC applied voltage is high enough, ie above the threshold, then the DTC 12 is deactivated and does not carry any sufficient amount of current, thereby minimizing wasted power. It should be noted that only an absolute threshold is necessary so that the voltage level detector 15 is located on the DC side of the rectifier 19. This means that the DTC 12 is activated in the range of 30V to + 30V when the threshold is 30V.

 In some embodiments of the DTC 12, when used for a 50 Hz, 230 V main power system, the threshold is located between 3 V and 50 V. In another embodiment of the DTC 12, the minimum threshold is 10V. The threshold may be located between 3 V and 25 V if the DTC 12 is connected to a 120 V mains power system at 60 Hz, for example as used in the United States.

 For example, as schematically illustrated in FIG. 1 with respect to the triac TR1 triggered by the diac D1, the current provided by the DTC 12 is the voltage across the load until the triac in the dimmer triggers. Efficiently maintain at zero. As soon as the TRIAC switches on, the voltage at terminal T2 increases by a large amount. As a result, the current source circuit 17 in the DTC 12 is inactivated.

 Thus, if the voltage at T2 exceeds the threshold, otherwise the DTC acts like an open circuit, the DTC ideally only conducts current. However, in practice, some current will flow through the DTC while being deactivated. Desirably, the current provided by the current source circuit 17 in the DTC 12 upon deactivation can be ignored. The current may be considered negligible if the current is at least two orders of magnitude less than the maximum current that the current source circuit 17 of the DTC 12 can provide. For example, if the maximum current provided by the current source circuit 17 in the DTC 12 is 15 mA, the current is considered negligible if its value remains below 100 μA.

 If, after the zero crossing, there is simply a non-continuous load (ie a load carrying a non-continuous current such that the current is zero for some part of the voltage cycle), the DTC 12 will Acts complementarily to the state of the triac. That is, when the DTC is on, the triac in the dimmer is off and vice versa. A bridge rectifier with a capacitor at the output is one example of a discontinuous load.

 On the other hand, after the zero crossing has passed, in addition to the discontinuous load, if there is another load, then if the input voltage of the DTC 12 exceeds the previously described threshold, then the DTC 12 will Both the DTC 12 and the triac in the light fixture 1 may turn on simultaneously. In such a case, the DTC 12 and triac in the dimmer 1 do not act completely complementary. For a fraction of a millisecond, power is consumed if both the DTC and the triac are on. However, this consumed power may be negligible. For example, for a current source circuit 17 arranged to supply a threshold of 30 V and a current of 20 mA, the peak power will typically not exceed 0.6 W (this peak power is very small Only for the interval). Also, the average power will not exceed 30 mW.

Generally, if the zero crossing is passed, the triac turns off (if it is on) and the DTC 12 remains. When the TRIAC turns on, the DTC 12 turns off. Thus, the DTC 12 is arranged to supply current if the absolute voltage of T2 is below the threshold. This current only needs to be sufficient to allow the charging of the capacitor in the RC circuit of the dimmer, the holding of the triac or the hypostatic current or the dimmer in question. It has nothing to do with the minimum load. If the DTC is activated (if the TRIAC is off) and if the DTC is deactivated (if the TRIAC is on), then the current of the DTC 12 may be less than the holding current of the dimmer triac. This provides the advantage that DTC 12 can be used in conjunction with a triac having a holding current greater than the maximum current provided by DTC 12. Thus, even though DTC 12 can supply a maximum current of, for example, 20 mA, a dimmer including a triac with a holding current of, for example, 100 mA, greater than 120 mA enables dimming of low load applications It can be used for

 In order to enable proper functioning of the DTC 12 in the lighting system, for example, when connected to the LED circuit 13 as shown in FIG. , Preferably minimized. Preferably, no additional capacitance is present between the terminals T2 and T3.

 Thus, the DTC 12 may be used to provide a method of triggering a dimmer in an alternating current circuit. Such method would include detecting if the absolute value of the DTC's input voltage is below a threshold. Subsequently, if the sensed voltage is below the threshold, current is provided by the current source circuit. The current flows through the DTC and the dimmer. If the sensed voltage is not below the threshold, only negligible current flows through the DTC and the dimmer. Prior to sensing the value of the DTC input voltage, the input voltage may be generated by adjusting the alternating voltage of the alternating circuit. Subsequently or alternatively, the input voltage may be converted to a voltage suitable for sensing. Finally, the current provided by the current source circuit may be limited.

 FIG. 6 shows a simplified circuit diagram of an embodiment of a DTC, such as DTC 12 shown in FIGS. It should be understood that this embodiment is an example of one possible implementation of the invention. As those skilled in the art will appreciate, many implementations are possible. For example, instead of the bipolar NPN transistor, other switches such as a bipolar PNP transistor, an integrated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET) may be used. In this embodiment, the bipolar current source circuit 18 further includes a current source circuit 17 and a rectifier 19. The rectifier 19 comprises a full wave diode bridge rectifier. The current source circuit 17 includes two resistors R2, R3 and two NPN transistors Q1, Q2. Voltage level detector 15 includes an NPN transistor Q3 and two resistors R4 and R5.

 In this embodiment, the DC power supply V1 is connected to the collector of the transistor Q3 of the voltage level detector 15. Resistor R6 is chosen such that the desired base current may be applied to Q1 when Q3 is off. The DC power supply V1 may be an external power supply. It should be understood that instead of the DC power supply V1 and the resistor R6, further current sources may be used to obtain the desired base current. Resistors R4 and R5 are designed as if the voltage at T4 is below the threshold, the voltage at T7 is as if Q3 were off to form a voltage divider.

The collector of Q1 in this embodiment of the current source circuit 17 is connected to the terminal of the rectifying diode bridge, denoted as T4. The base of Q1 is connected to the collector of Q2 and to the collector of Q3 in the voltage level detector 15. If the voltage at T4 is less than the aforementioned threshold, Q3 is off. Also, R6 will now supply current to the base of Q1. As a result, the voltage of T6 is increased to turn on Q1. As a result, Q1 conducts current. Also, the voltage at T4 decreases even more depending on the impedance of the source. It results in an even lower voltage at T7. Thus, the switch off time of Q3 is limited. If the current through Q1 exceeds a certain value, then the base voltage of Q2 exceeds its switch on voltage. Also, Q2 conducts and thereby stabilizes the potential at T6. Therefore, it controls the collector current passing through Q1. Resistors R2 and R3 design a current source with appropriate characteristics. That is, if the emitter current through transistor Q1 exceeds a certain value (eg, a nominal current in the range of 10 to 20 mA), transistor Q2 will begin to conduct. Thus, the combination of transistor Q2 and resistors R2 and R3 provides a feedback circuit that effectively limits the collector current of transistor Q1. R3 sets the current to approximately 0.6 / R3. When the TRIAC starts, R2 functions to protect Q2. The combination of transistors Q1 and Q2 and resistors R2 and R3 form a stable current source circuit 17 for a voltage T4 higher than approximately 1 V with respect to the negative terminal of the rectifier 19. If the voltage on T4 goes below approximately 1 V, the collector current will decrease. A 220Ω resistor meets EMI requirements, limits the current slope at low voltage levels, and may be added in series with the collector of Q1.

 The current source circuit 17 is activated when the voltage level detector 15 detects that the voltage of T4 becomes lower than a predetermined threshold, and is deactivated when the voltage of T4 becomes higher than the predetermined threshold again. Be done.

 In order to obtain a DTC 12 designed to supply a current of 15 mA when the voltage of T2 is between -30 V and 30 V, the standard values of the components shown in Fig. 6 are: R2 R4 = 6.6 MΩ (generally constructed by locating two resistors with a value of 3.3 MΩ in series); R5 = 100 kΩ; R6 = 47 kΩ; Q1 = FMMT 458; Q2 = BC817; Q3 = BC817; V1 = 10V. The current provided in FIG. 6, provided by the DTC 12 and provided with components with the aforementioned values during activation, will be approximately 20 mA. On the other hand, during deactivation, the ideal current would be only approximately 49 μA. Adding a leakage current through transistor Q1 may add several μA.

FIG. 7A shows a graph of the calculation of the behavior of the current I _DTC (ie the current through the DTC) as a function of the voltage V _DTC (ie the voltage through the DTC). In this calculation, the DTC of FIG. 6 is used such that the standard values described above are used for each component. Thus, if the voltage across the DTC falls below the 30 V threshold, the DTC is arranged to supply an absolute value of 20 mA for the maximum current. By means of the rectifier, current may be supplied to the dimmer in the opposite direction.

It can be noted that if V _DTC is near 0, I _DTC equals 0, and the value of V _DTC rises quickly to the design current, in which case I _DTC does not exceed 20 mA. The low current near 0 of V _DTC only causes current source circuit 17 to supply current as needed, ie (during the higher current directly on the grid) dimmer 1 has its timer Due to the fact that it only limits the current charging the circuit. The shape of the curve shown in FIG. 7A (which relates to the current source circuit 17 schematically depicted in FIG. 5) is the result of the transistor Q1 being saturated at low voltage.

 FIG. 7B schematically shows a graph of voltage-current operation across the terminals of the embodiment of the dimmer trigger circuit of FIG. 4 including a microprocessor or a sensitive component of direction. As shown in FIG. 7B, the DTC 12 may switch on while the TRIACs in the dimmer 11 may simultaneously turn on just prior to the crossing of the zero crossing. As a result, power is consumed for a short period of time, ie, the time required for the voltage through DTC 12 to go from the threshold to zero. In embodiments that include a microprocessor as voltage level detector 15, the microprocessor may be programmed such that it only allows bipolar current source circuit 18 to be activated after the zero crossing has passed. As a result, the voltage-current operation between the terminals of the DTC 12 is as schematically shown in FIG. 7B.

In FIG. 7B, it can be easily understood that I _DTC experiences a kind of hysteresis. That is, the value of _{I DTC} at a _{V DTC is} determined by the previous value of _{V DTC.} The portion of the graph where I _DTC is determined by the past values of V _DTC is schematically illustrated by the gray line. The portion of the graph where I _DTC is determined by the past values of V _DTC is schematically illustrated by the black line. Arrows indicate the direction of change of V _DTC .

[Set point filter circuit]
In the lighting system as depicted in FIG. 3, the LED drive circuit in the load 13 includes a current controller that supplies DC current to the LED and a DC current, so the light intensity of the LED is the power supply voltage They are typically arranged so as not to be dependent. The current controller controls the LED current within the range of the system. As a result, any change in power supply voltage will not produce a change in LED current. The LED current is controlled by the setpoint. Different current levels are due to different set point values. In some embodiments of the present invention, the average rectified voltage measured by the voltage level detector 15 of the DTC 12 may be used in the drive circuit as a set point. Set point filter circuits may be used to further optimize the dimming of the load. This optimization may result in dimming the load to a different extent than the dimmer setting. As a result, the full range of adjusted set points is generated over the full range of dimmer settings (i.e., dimmer set point values). For example, the circuit may change the drive circuit set point by generating 0-100% or more adjusted set points corresponding to a series of 30-80% dimmer knob settings.

 Optimization is more sensitive to darkening in low intensity regions (i.e. 1-10% within the set intensity range) and darkening in high intensity regions (e.g. 10-100% within the set intensity range) It may take a form that senses a little. Where the lighting system includes an LED light source, the setpoint filter circuit uses it to produce a selected intensity at a sensed intensity that is closer (that is, selected by the dimmer knob setting) can do. A typical incandescent lamp typically uses electrical power to heat the tungsten filament so that it converts about 10% of the consumed electrical energy to visible light, causing it to emit light. An incandescent lamp exhibits a progressive response curve. The light generation from the light bulb is approximately proportional to the effective voltage on the third power (cubic response). It should be noted that in the case of a phase controlled voltage waveform, the RMS voltage has a non-linear relationship with the effective voltage.

 The human eye generally perceives the light intensity by means of a logarithmic curve. Thus, if the load current is changed linearly due to the adjustment of the dimmer, the cubic response of the incandescent light will match fairly well with the logarithmic response of the human eye. Also, light dimming is considered to be relatively linear and smooth. However, LEDs exhibit a nearly linear response rather than a three dimensional response. Here, the intensity of the emitted light is approximately proportional to the current flowing through the LED. Thus, if the load current is changed linearly, the change in perceived light intensity has no intuitive relationship to the dimmer knob position.

  The setpoint filter circuit is used by the drive circuit to generate a setpoint with a progressive response approximating an exponential change when the dimmer setting is changed Can be used to adjust the set point being FIG. 8 shows a circuit diagram of an embodiment of a setpoint filter circuit for the generation of an approximation of the exponential change for the setpoint case. The circuit includes a low pass filter (LPF) that includes a resistor R10-R13 and a capacitor C10. The input 20 to the LPF may be derived, for example, from the output of the rectifier of the DTC 12 shown in FIG. 6 or from another point in time to provide a rectified voltage across the load.

  This LPF circuit achieves a substantially ripple-free set point for the LED current controller during unstable dimmer performance due to false triac starting which may occur at starting angles between 0 and 90 degrees And serve as a low pass filter to remove light source fluctuations and serve as a barrier between the low voltage circuit and the high voltage input of the LED drive circuit, serving a dual purpose. A first order filter, or a third order or higher order filter may be used, but a second order LPF is preferably used to measure the rectified supply voltage and to determine its average voltage. This filter is used when the DC capacitor charges when the hiccup mode (drive circuit starts at low input voltage (above low input voltage) and switches off again due to lack of supply current. It may be provided at some time to maintain a filtered terminal voltage below the hysteresis threshold, while repeating again until sufficient supply is available, such as switching on again.

If the dimmer is to dim the load, the triac should turn off until after an appropriate phase delay according to the dimmer setting, for example, during period C of FIG. 2C.
If the TRIAC starts during 90-170 degrees during a half cycle, the TRIAC start is generally stable and predictable. However, if the TRIAC starts, it will charge the DC link capacitor (the capacitor on the DC side of the drive circuit's rectifier) in a very short time after no more current will flow. The triac will then turn off as the current falls below the triac's holding current (usually only a few hundred microseconds after triggering). In the absence of current flow, the voltage across the drive circuit will follow the supply voltage (e.g., the voltage of T2 will follow the voltage of T1).

  At triac starting angles between 0-90 degrees, dual (or multiple) starting of the triac may occur. Or, some starts may be skipped. If the dimmer is connected to a resistive load that is too small to maintain the load current on the triac's holding current, so that the triac turns off again after start-up, double start may occur. However, it is too large to draw enough current through the dimmer circuit to charge capacitor C1 and retrigger the triac. If the DC link voltage is lower than the current value of the supply voltage, a skipped start may occur since the triac simply switches on. If the trigger pulse comes early (closes to the zero crossing), the triac will be triggered. However, the input rectifier will not start as it does not allow negative current. Suitable values for the components of the LPF in this embodiment are: 10 MΩ for R10 and R11, 3.9 MΩ for R12 and R13, 22 μF for C10. The LPF is designed as a second-order filter that filters out the erroneous switching of the dimmer triac.

 The output from the LPF is supplied to the integrated operational amplifier U10. Also, the output 22 from U10 is an intermediate set point value representing a coarse dimmer knob setting. This is used to drive the gate of transistor Q10, which has a threshold voltage of about 2V and manages a progressive function. The source terminal of Q10 is connected to a voltage divider comprising resistors R18, R19 and R20. Further, the drain terminal is connected to the reference voltage Vref drawn from the standard integral voltage reference U11. The resulting signal 24 at the source terminal of Q10 may then be used as an input to the current controller of the LED drive circuit.

 As the dimmer settings are changed to dim the load, the lower average voltage across the load results in the reduced reference voltage Vref. If the output of U10 is low, transistor Q10 is turned off and the value of the adjusted setting signal 24 is determined by the output of U10 and the voltage divider R18 / R19 / R20. If the output of U10 rises sufficiently to turn off transistor Q10, the adjusted setting signal 24 is determined by the output of U10 and resistors R19 and R20. In this example, after the faster section is activated from 40-305 mA (approximately 130 V and 175 V), a slow change range between 10-40 mA (average input between approximately 70 V and 130 V), or The gate-source threshold voltage of Q10 is utilized to achieve the other required maximum values. The appropriate values for the embodiment of the circuit of FIG. 8 are as follows: R14 = 278 kΩ; R15 = 680 kΩ; R16 = 470 kΩ; R17 = 39 kΩ; R18 = 270 kΩ; R19 = 33 kΩ; R20 = 1.72 kΩ; C12 = 100 nF; C13 = 10 nF; C14 = 100 nF. For U10, a dual operational amplifier LM358ADR from Texas Instruments may be used. For Q10, a 2N 7002 N-channel enhancement mode field effect transistor from Fairchild Semiconductor may be used. Also for U11, adjustable precision shunt regulators from Zetex Semiconductor or Texas Instruments may be used.

 The output 24 of the setpoint filter is used as a reference so that the LED current controller darkens approximately smoothly for the user. Since the human eye has a logarithmic sense of luminance, "low gear" and "high gear" setpoint shapers are implemented. As shown in the example in FIG. 9A, the setpoint filter circuit produces a tuned setpoint change with two slopes. In the example shown in FIG. 9A, the actual dimmer settings SP1 are plotted on the horizontal axis. Also, the adjusted set point SP2 output by the set point filter is plotted on the vertical axis. As shown, the adjusted set point remains at a very low value 34 to the break point for the first part of the range of dimmer settings (0-20% in this example), and For the second part (20-50% in this example), it rises at a low rate 31 and for the third part of the range (50-80% in this example), it rises at a high rate 32, For the part (80 to 100% in this example), the high value 35 (100% not dimmed in this example) remains. Thus, the setpoint filter produces a tuned dimmer setpoint with progressive response of "two gears". It approaches an exponential response. This progressive movement of the adjusted setpoint results in a perceived smooth change in brightness due to the logarithmic response of the human eye, so that the dimmer setting is linearly increased Generate a progressive response that corresponds to the intensity of light from the

 This progressive response greatly reduces the sensitivity to changes in the dimmer start angle (ie, changes in the turn on delay of the triac after a zero crossing) at low light settings. Changes in the dimmer start angle occur, for example, as a result of changes in the AC applied voltage. These changes cause visible flickering of the dimmed light source, especially at low light dimmer settings. The adjusted set points generated by the set point filter circuit shown in FIG. 9A reduce the sensitivity of the illumination system to these changes, reduce or eliminate flicker, low dimmer setting plane 34 and shallow tilt It has 31.

 The dual slope adjusted set point curve shown in FIG. 9A is an approximation of the ideal exponential response as shown in FIG. 9B. The adjusted set point curve with three, four or more slopes may be implemented to more closely approximate the exponential curve using techniques known to those skilled in the art. A microprocessor may also be used to generate adjusted set points that follow an ideal exponential response.

 The adjusted setpoint generated by the setpoint filter circuit is used as a setpoint input to the current controller to drive the LED. FIG. 10 shows a simplified circuit on the second stage of the transformer T10 of the LED drive circuit. As described above, the setpoint filter circuit of FIG. 8 generates the adjusted setpoint voltage 24 through R 20 in a partially linear manner as a function of the output of integrating amplifier U 12. The adjusted set point 24 is input to the operational amplifier U12 via the resistor R21. If the voltage across the second shunt resistor R24 is equal to the voltage across R20, the integrator circuit is unstable. The shunt resistor R24 is connected in series with the LEDs 1-4 connected in series. An amplifier U12 coupled with R20-24 and C15 forms a current controller circuit 27.

 The output of U12 provides a feedback signal to shunt regulator U11 and optocoupler U13 via resistor R22 and voltage dividers R25, R26. The optocoupler U13 supplies a feedback signal to the flyback controller on the primary side of T10. This part of the circuit forms a voltage controller circuit 26. The output of U12 can be considered as a reference value for the voltage controller around U11. If the current through R24 is too low, voltage feedback from U12 will cause a higher voltage control setpoint. This will reduce the current through optocoupler U13 and signal the flyback controller to increase its power flow so that the commanded reference supply is obtained and the required LED current is realized. If the current through R24 is too high, the feedback signal causes a low voltage set point. The flyback controller will reduce power flow to secondary in response to reducing the LED current.

 Values suitable for the embodiment of the circuit of FIG. 10 are as follows. R20 = 1.72 kΩ, R21 = 4.7 kΩ, R22 = 8.2 kΩ, R23 = 2.7 kΩ, R24 = 39 Ω, R25 = 12 kΩ, R26 = 2.49 kΩ, R27 = 2.7 kΩ, C15 = 1 nF, C16 = 3 μF. For U12, a dual operational amplifier LM358ADR from Texas Instruments may be used. Also, for U13, a PS2801C-1 photocoupler from NEC may be used. For the PWM controller, the UCC 28600 from Texas Instruments may be configured and used to operate in a constant output voltage suppressed mode.

[Time-based setpoint control]
If the power supply signal driving the LED and the information signal setting the intensity of the LED are both embodied in the same signal, and the average voltage is through the load, the lighting system described above can be considered as a system . This arrangement generally depends on the voltage across the load, depending on the dimmer knob settings. If this is not the case, the dimming of the load does not necessarily coincide with the setting of the dimmer, in particular due to the operation of the dimmer with a low load or a discontinuous load.

 As discussed above, the lighting system described herein may operate with a load below the dimmer triac holding current. The DTC described above will deliver sufficient current to guarantee triac triggering. Once triggered, the DTC will emit negligible current and deactivate. For small loads and in the case of a rectifier with a DC link capacitor load, the dimmer will drop below the holding current of the dimmer triac. If the load / drive circuit keeps the active power factor correction on the front end, then the load acts more like a resistor, possibly charging and starting the dimmer circuit as shown in FIG. 11B. Each may bring.

 FIG. 11A, as described above, if the dimmer setting is due to the starting of the TRIAC at time t1 after the zero crossing point t0 of each half cycle, and the TRIAC flashes through the dimmer triac 5 is a graph showing the waveform of the voltage across the load (e.g., terminals T2-T3 of the circuit of FIG. 3) when the load immediately after being a charge DC link capacitor and the combined current divided by the DTC are zero.

 FIG. 11B shows an example of a voltage waveform at the same dimmer setting when the dimmer is connected to a small resistive load that is too small to maintain the load current on the triac's holding current. A small resistive load of this kind may be present in the drive circuit with a modified active power factor on the front end that drives a DC circuit with low power consumption.

 At time t1, the triac is triggered and the voltage rises quickly. However, the current flowing through the triac is not sufficient to maintain the triac in the conducting state, the triac turns off again, and the voltage across the load drops due to the resistive characteristics of the load. Because the voltage through the dimmer is increasing, the RC circuit in the dimmer recharges even though the DTC is always activated and does not trigger the dimmer triac again. right. As a result, the triac is triggered in multiples during each half cycle as shown in FIG. 11B. The TRIAC-based dimmer is connected to a low power resistive load so that the active power factor correction circuit boosts the converter with discontinuous switching for DC link drive or direct drive of the LED. If so, such multiple triggering of the triac may occur.

As can be seen by comparing the average voltage of each half cycle in FIGS. 11A and 11B, this multiple trigger results in a very disturbing voltage across the load and a lower average voltage. If this voltage is used to derive a setpoint that controls the intensity of the LED, it will result in an oscillating setpoint. If an average (or RMS) voltage is used to set the LED light source intensity in this situation, false dimming with unstable light output will occur.

 The solution to this problem is to use time information to control the LED light source intensity rather than voltage level information. The time delay from the zero crossing point to the first trigger of the triac following the zero crossing may be used to derive a control value of the LED light source intensity (which is also referred to as a start angle or phase control value). This time delay value varies depending on the charge time of the RC circuit of the dimmer (which depends on the dimmer knob setting) and is not affected by multiple Triac starts that may occur later in a half cycle .

 A microprocessor may be used to derive the LED intensity setpoint value from the time delay value. One way to implement this is to measure when the rising and falling edges of the current through the DTC occur, or to measure the voltages associated with these rising and falling edges. The rising and falling edges of these currents are for example shown in FIG. 7B and correspond to moments. When the TRIAC turns off at the zero crossing, the DTC is activated (rising edge). If the TRIAC is triggered, the DTC is deactivated (falling edge). The time between two rising edges indicates the cycle time between the zero crossings of the supply voltage. The time between the rising edge and the falling edge indicates the time delay between the zero crossing and the start time of the first triac. From these measurements, the triac starting angle can simply be calculated. This can be conveniently done in the embodiments shown in FIGS. 3 and 6 by measuring the rising and falling edges of the voltage at T6 at the base of the transistor Q1 of the current source circuit 17 of the DTC 12. In the embodiment described above, this voltage will be about 0.5 V when the DTC is activated and Q3 is on, and when the DTC is inactivated and Q3 is off. It will be about 1.5V.

 The time between associated rising / falling edges can be measured using a clock. It starts when an edge is detected and is stopped when the next relevant edge is detected. The time between the rising edge of the DTC current and the next falling edge of the DCT current can be determined and divided by the time between the two rising edges to determine the triac off duty cycle. The triac on duty cycle is then (1-off duty cycle). Progressive features can be used to derive the current setpoint for the LED. Also, this function can be an exponential function with saturation. Such clock and advanced features can be implemented using a microprocessor or microcontroller, as understood by one of ordinary skill in the art.

 With this solution, the system is designed for applications in dimmable circuits with universal power inputs (eg 90 V to 240 V AC supply voltage) for use in countries with different AC voltages can do. Because the light source intensity control value is not a voltage value but a time delay value, the input voltage value and the resulting average load voltage do not change as a function of the AC applied voltage. This allows a single design to be used everywhere in the world, thereby reducing manufacturing costs by a large savings in scale.

[Hysteresis and minimum current]
A dimmer without an "off" switch acts like a series capacitor when set at the minimum (i.e., turn off the light source) position. AC current will flow through this "capacitor" to charge the DC side of the rectifier in the LED drive circuit. This may be sufficient to activate the controller chip in the LED drive circuit after a short period of time. This may discharge the DC link to flash the LED briefly. Then the under voltage will be detected. The controller will switch off. Also, the cycle will start over again. To prevent this unwanted flushing, the current control circuit may be provided with some positive feedback to generate hysteresis. Thus, the current controller will receive a zero set point until the average input voltage exceeds a certain limit. The current set point is then switched to a low value (eg, about 30 mA). By returning the dimmer knob back to a lower setting, the LED current may then be reduced (eg, to about 10 mA). Thus, in this low dimmer setting, the LED may be on or off depending on the previous dimmer setting.

Minimal current flow through the LED is preferred to avoid changes in light intensity, due to the dimmer circuit interaction, at near no load (i.e., low dimmer setting). Nearly no load, the DC side voltage of the rectifier in the LED drive circuit is increased by the LC filter inside the dimmer (eg, inductor L1 and capacitor C2 included in the dimmer circuit of FIG. 1) Tend. This increase raises the measured average load voltage which raises the LED current. This rise in current will lower the DC voltage. Also, the LED current will decrease again. As a result, the LED current oscillates. This problem can generally be avoided by maintaining the LED current at or above the minimum of at least 5 mA. If the start angle of the dimmer triac approaches 180 degrees, the circuit will stop driving and a failure mode will occur. However, due to the hysteresis, no light will be generated. It is similar to what an incandescent bulb does.

 Hysteresis and minimum current may be implemented in the embodiment shown in FIG. 10 by adding resistors R30 and R31 and capacitor C17 as shown in FIG. R30 and R23 produce positive feedback around amplifier U12. If the LED is controlled, the output of U12 is about 2.5V. Also, when the LED is off, the output of U12 is about 8V. Thus, a hysteresis of about 10 mV will appear at node 24. The minimum current is determined by the resistor and its hysteresis through Q10 (not shown), which raises reference 24 from ground. If the LED is off and the reference 24 is rising, U12 will toggle as soon as the input of U12 rises above the + input. After toggling, the + input drops to about 10 mV, thereby increasing the set point by about 10 mV / R24 = 30 mA. Suitable values are: R30 = 1.2 MΩ; R31 = 4.7 kΩ; C17 = 10 nF.

[Over and under voltage protection]
The secondary circuit of the LED drive circuit preferably acts as a current source only for a certain range (for example, an output voltage between 8.3 V and 17.3 V) and aims to use voltage control outside this range ing. If the current setpoint for the LED is zero, the drive circuit must still be valid. Thus, to make this possible, the output of the drive circuit is a controlled voltage to avoid under voltage lockout of the flyback controller chip. For voltages on the current control range, the drive circuit is in voltage control mode in order to avoid over-voltage in the circuit (especially the power transistor on the primary side of the drive circuit) in case of LED disconnection or open circuit failure. to go into. The current control range is set by the value of the resistor and a reference power chip can be used to achieve very low tolerance. The built-in over-voltage protection present in some flyback controller chips is rather not used due to its too high tolerance.

 Thus, the present invention has been described by reference to certain embodiments discussed above. The elements and components in one embodiment may be used in other embodiments. The embodiments described above include DTCs, which can be omitted. Moreover, various features of the drive circuitry or set point filter circuitry described in the context of various embodiments may be omitted from those embodiments or included in other embodiments. It will be clear.

 It will be appreciated that the described embodiments can accept various modifications and alternatives well known to those skilled in the art. For example, instead of using a DTC with a full wave rectifier, such as a diode rectifier bridge, two DTCs with half wave rectifiers may be used. In the latter case, one DTC will be used in one direction of the AC current. Also, another DTC will be used in the opposite direction. The circuits described may be designed with bipolar transistors or MOSFETs S or other types of switching elements. The terms "base", "collector" and "emitter" and "gate", "drain" and "source" refer not only to the connection of bipolar transistors or FETs, but also to other types of transistors It should be noted that it should be broadly interpreted as referring also to connections. Furthermore, embodiments of the present invention have been described with respect to a lighting system. However, the invention may relate to circuits for still other types of applications.

Claims (53)

A lighting system for cooperating with a dimmer circuit connected to a load, comprising:
The system has the load;
The load comprises a drive circuit for supplying current to a light source comprising one or more LEDs,
The current is at least partially determined by the adjusted setpoint value,
The system further comprises a setpoint filter circuit that obtains a dimmer setpoint value at least partially determined by the setting of the dimmer circuit and generates an adjusted setpoint value.
Sensitivity of the adjusted setpoint value to changes in the dimmer setpoint value, rather low at low values of the dimmer setpoint value, the adjusted setpoint value increases discontinuously, lighting system. The lighting system according to claim 1, wherein the adjusted set point value remains at a constant value from a break point. The lighting system according to claim 1, wherein the adjusted set point value remains at a constant value up to a break point. The lighting system of claim 1, wherein the adjusted set point value changes by two slopes.  The setpoint filter circuit is configured to increase the adjusted setpoint at a low percentage of the low value of the dimmer setpoint value and a high percentage of the high value of the dimmer setpoint value. The lighting system of claim 1. 6. The lighting system of claim 5, wherein the change in the adjusted setpoint value in response to the change in the dimmer setpoint value approximates an exponential response .  The lighting system of any one of the preceding claims, wherein the setpoint filter circuit generates a full range of the adjusted setpoint values that is less than a full range of the dimmer setpoint values.  The lighting system of any one of the preceding claims, wherein the setpoint filter circuit generates an adjusted setpoint value having a minimum value greater than zero.  The setpoint filter circuit has a first substantially constant value in a first portion of the range of dimmer setpoint values, and a second portion of the range of dimmer setpoint values. Increasing at a low rate and increasing at a high rate during the third part of the range of dimmer setpoint values, and during the fourth part of the range of dimmer setpoint values A lighting system according to any one of the preceding claims, configured to generate the adjusted setpoint having a substantially constant value.  The lighting system of any one of the preceding claims, wherein the setpoint filter circuit comprises a second or higher order low pass filter for filtering the received dimmer setpoint value. The set point filter circuit comprises a differential amplifier for generating an intermediate set point value,
The lighting system of any one of the preceding claims, which controls a transistor to generate the adjusted setpoint value. The drive circuit comprises a voltage control circuit and a current control circuit,
The voltage control circuit controls the voltage at the output of the drive circuit according to a voltage set point,
The lighting system of any one of the preceding claims, wherein the current control circuit modifies the voltage setpoint according to a current setpoint. The current control circuit operates within a predetermined range,
13. The lighting system of claim 12 , wherein the voltage set point is maintained at a boundary value when the current control circuit is at the boundary of its operating range.  The lighting system of any one of the preceding claims, wherein the setpoint filter circuit derives the dimmer setpoint value from a voltage at an output terminal of the dimmer circuit. Any one illumination system of the setpoint filter circuit, which leads to the dimmer setpoint value from the starting angle of the triac which the dimmer has claim 1-12. 16. The lighting system of claim 15 , wherein the setpoint filter circuit derives the dimmer setpoint value from a time delay between the first trigger of the triac and a zero crossing of the power supply voltage after a zero crossing point. Further comprising a dimmer triggering circuit adjustment for the triac triggering of the dimmer,
The dimmer set point value may be due to the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimmer trigger circuit, or the voltage associated with the rising and falling edges. 17. The lighting system of claim 15 or 16 , wherein at least a part is determined.  The dimmer set point value is at least one of a time delay between a rising edge and a falling edge of current flowing through the dimmer trigger circuit, or a voltage associated with the rising edge and the falling edge. The lighting system of claim 17, wherein a part is determined. Any one of the illumination system of the regulating current by the dimmer circuit when the triac is on the optical device is a triac less than the holding current of the dimmer, previous claims. Further comprising a dimmer triggering circuit adjustment for triac triggering of the dimmer,
The dimmer trigger circuit
A voltage level detector for detecting whether the input voltage of the dimmer trigger circuit is less than a threshold;
A bipolar current source circuit that supplies current if the voltage sensed by the voltage level detector is below the threshold, otherwise deactivated.
A lighting system according to any one of the preceding claims, comprising. 21. The lighting system of claim 20 , wherein the maximum current through the dimmer trigger circuit is less than the holding current of the dimmer triac. If the triac of the dimmer is ON, current due to the dimmer triggering circuit, the less than triac holding current, the lighting system of claim 20 or 21. If the triac of the dimmer is off, current by the dimmer triggering circuit, the less than triac holding current, one of the illumination system of one of claims 20-22. Any one of the illumination system of the dimmer triggering circuit, in operation, which consumes an average power of less than 100 mW, claims 20-23. Dimmer circuit,
A light source comprising one or more LEDs,
Drive circuitry for supplying current to one or more LEDs,
A set point filter circuit for use in a lighting system comprising
The current is at least partially determined by the adjusted setpoint value,
The set point filter circuit is
An input circuit for obtaining a dimmer set point value at least partially determined by the setting of the dimmer circuit;
An adjustment circuit that generates an adjusted set point value;
Equipped with
Sensitivity of the adjusted setpoint value to changes in the dimmer setpoint value, rather low at low values of the dimmer setpoint value, the adjusted setpoint value increases discontinuously, set Point filter circuit. 26. The setpoint filter circuit of claim 25 , wherein the adjusted setpoint increases at a low rate of a low value of the dimmer setpoint value and a high rate of a high value of the dimmer setpoint value. 27. The setpoint filter circuit of claim 25 or 26 , wherein the change in the adjusted setpoint value in response to a change in the dimmer setpoint value approximates an exponential response . 28. The set point filter circuit of any one of claims 25 to 27 , wherein the adjustment circuit generates a full range of the adjusted set point values that is less than the full range of the dimmer set point values. The adjusting circuit generates an adjusted setpoint value having a greater than zero minimum value, one of the setpoint filter circuit of claim 25-28. 30. The set point filter circuit of any one of claims 25 to 29 , wherein the input circuit comprises a second or higher order low pass filter for filtering the received dimmer set point value. The adjustment circuit comprises a differential amplifier generating an intermediate setpoint value,
31. The setpoint filter circuit of any one of claims 25 to 30 , which controls a transistor to generate the adjusted setpoint value. The dimmer setpoint value is obtained from the voltage at the output terminal of the dimmer circuit, one of the setpoint filter circuit of claim 25-31. The dimmer setpoint value, derived from the triac starting angle of the dimmer, one of the setpoint filter circuit of claim 25-31. 34. The setpoint filter circuit of claim 33 , wherein the dimmer setpoint value is derived from the time delay between the first trigger of the triac and the zero crossing of the supply voltage after a zero crossing point. A lighting system for cooperating with a dimmer circuit comprising a TRIAC, comprising:
The lighting system is
A light source comprising one or more LEDs,
A dimmer triggering circuit for the triac triggering of the dimmer, the load having a driving circuit for supplying a current to the one or more LED,
Equipped with
The current supplied by the drive circuit is at least partially determined by the adjusted set point value,
A lighting system, wherein the dimmer setpoint value is at least partially derived from the starting angle of the dimmer triac, and the adjusted setpoint value increases discontinuously . 36. The lighting system of claim 35 , wherein the drive circuit derives the dimmer setpoint value from a time delay between a zero crossing followed by a first trigger of the triac and a zero crossing of a power supply voltage. The dimmer set point value may be due to the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimmer trigger circuit, or the voltage associated with the rising and falling edges. 37. The lighting system of claim 35 or 36 , wherein at least a part is determined. The dimmer set point value is at least one of a time delay between a rising edge and a falling edge of current flowing through the dimmer trigger circuit, or a voltage associated with the rising edge and the falling edge. The lighting system of claim 37 , wherein a part is determined. The drive circuit comprises a voltage control circuit and a current control circuit,
The voltage control circuit controls the voltage at the output of the drive circuit according to a voltage set point,
The current control circuit modifies the voltage setpoint according to the current set point, claim 35 - 38 one of the illumination system of the. The current control circuit operates within a predetermined range,
40. The lighting system of claim 39 , wherein the voltage set point is maintained at a boundary value when the current control circuit is at the boundary of its operating range. Any one of the illumination system of the regulating current by the dimmer circuit when the triac is on the optical device is a triac less than the holding current of the dimmer, claims 35-40. The dimmer trigger circuit
A voltage level detector that detects whether the input voltage of the dimmer trigger circuit is less than a threshold;
A bipolar current source circuit that supplies current if the voltage sensed by the voltage level detector is below the threshold, otherwise deactivated.
42. A lighting system as claimed in any one of claims 35 to 41 . 43. A lighting system as claimed in any one of claims 35 to 42 , wherein the maximum current by the dimmer trigger circuit is less than the holding current of the triac of the dimmer. If the triac of the dimmer is ON, current due to the dimmer triggering circuit, the less than triac holding current, one of the illumination system of one of claims 35-43. If the triac of the dimmer is off, current by the dimmer triggering circuit, the less than triac holding current, one of the illumination system of one of claims 35-44. The dimmer triggering circuit, in operation, consumes an average power of less than 100 mW, any one illumination system of claim 35 to 45. Further comprising a setpoint filter circuit for generating an adjusted setpoint value from said dimmer setpoint value;
The sensitivity of the adjusted setpoint value is lower at lower values of the dimmer setpoint value, claim 35 to changes in the dimmer setpoint value - 46 any one illumination system of. The setpoint filter circuit is configured to increase the adjusted setpoint at a low percentage of the low value of the dimmer setpoint value and a high percentage of the high value of the dimmer setpoint value. 48. A lighting system according to claim 47 . 49. A lighting system as claimed in claim 47 or 48 , wherein the change in the adjusted setpoint value in response to a change in the dimmer setpoint value approximates an exponential response . Any one illumination system of the setpoint filter circuit, for generating the full range of the adjusted setpoint value of less than the full range of the dimmer setpoint value, claims 47-49. 51. A lighting system as claimed in any one of claims 47 to 50 , wherein the setpoint filter circuit generates an adjusted setpoint value having a minimum value greater than zero. The setpoint filter circuit has a first substantially constant value in a first portion of the range of dimmer setpoint values, and a second portion of the range of dimmer setpoint values. Increasing at a low rate and increasing at a high rate during the third part of the range of dimmer setpoint values, and during the fourth part of the range of dimmer setpoint values 52. A lighting system according to any one of claims 47 to 51 , configured to generate the adjusted set point having a substantially constant value. A lighting system for cooperating with a dimmer circuit comprising a TRIAC, comprising:
The lighting system is
A light source comprising one or more LEDs,
A dimmer triggering circuit for the triac triggering of the dimmer, the load having a driving circuit for supplying a current to the one or more LED,
Equipped with
The drive circuit comprises a power factor correction circuit,
The current supplied by the drive circuit is at least partially determined by the dimmer setpoint value,
A lighting system, wherein the dimmer setpoint value is at least partially derived from the starting angle of the dimmer triac, and the adjusted setpoint value increases discontinuously .

Images