Dimmer circuit and LED lighting device having said dimmer circuit

A dimmer circuit may include: a rectification module, a control module and an output module, wherein the control module receives an input signal rectified through the rectification module and controls the output module to supply a load with an output signal in accordance with the input signal, and a compensation module which collects sampled signals characterizing dimming state of the dimmer circuit between the control module and the output module, and supplies the control module with a compensation signal in accordance with the sampled signals, the control module changing the value of the output signal according to the input signal and the compensation signal.

RELATED APPLICATIONS

This application claims priority to Chinese Patent Application Serial No. 201320112025.1, which was filed Mar. 12, 2013, and is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Various embodiments relate to a dimmer circuit and an LED lighting device having said dimmer circuit.

BACKGROUND

With rapid development of lighting devices, particularly the development of LED lighting devices having high efficiency and requiring low power, various luminaires applying LED technique are widely applied to every aspect of daily life, for example, indoor lighting or public lighting. Consequently, the requirements of users on electrical performance, mechanical performance and lighting effect of LED lighting devices are increased. At the present, a PSR type LED driver circuit that works based on the phase cut dimming principle is widely applied due to the requirement of the market on product cost. Moreover, higher and higher requirements on dimming range of LED lighting devices having such a driver circuit are made by users, for example, it is required that such an LED lighting device can provide a wider dimming range, and particularly, a deep dimming is further required when said LED lighting device is regulated to the lower limit of the dimming range. Considering these requirements, improvements are provided in the prior art.

In a solution of the prior art, it is provided that an LED lighting device can have a further deep dimming in a situation of reaching the lower limit of the dimming range by adding dissipative elements, such as adding a bleeder circuit, wherein said bleeder circuit is enabled to share partial electrical energy of the whole driver circuit, so as to achieve the object of performing a deep dimming, and the dimming effect thereof is shown inFIG. 1. However, in a situation that a deep dimming might be allowed, a large quantity of unnecessary power dissipation is resulted from such a solution, which renders that a large quantity of electrical energy is consumed and wasted. Moreover, in order to achieve said object, extra dissipative elements have to be added in the circuit. In this case, not only cannot save electrical energy, but also unnecessary cost consumption is generated in such a circuit design.

SUMMARY

In order to solve the above mentioned technical problem, various embodiments provide a novel dimmer circuit. According to various embodiments, a deep dimming is further realized when the LED lighting device is regulated to reach a relatively low dimming level, so as to satisfy the requirements of users on dimming. Moreover, as said dimmer circuit does not perform a deep dimming by utilizing dissipative elements, the power dissipation of the dimmer circuit per se is reduced, and such a dimmer circuit further has the advantages of simple structure and low cost. In addition, various embodiments further relate to an LED lighting device having the dimmer circuit mentioned above.

According various embodiments, said dimmer circuit includes a rectification module, a control module and an output module, wherein the control module receives an input signal f rectified through the rectification module, and controls the output module to supply a load with an output signal in accordance with the input signal, characterized by further comprising a compensation module which collects sampled signals characterizing dimming state of the dimmer circuit between the control module and the output module, and supplies the control module with a compensation signal in accordance with the sampled signals, the control module then changes the value of the output signal according to the input signal and the compensation signal. Through the addition of a compensation module in the dimmer circuit, the control over the driver circuit is realized and the possibility for a further deep dimming is provided, even in a situation that the dimmer circuit reaches to the lower limit of the dimming range, viz. its phase cut angle reaches the minimum value. The term “deep dimming” in the scope of the present disclosure means e.g. increase of the dimming range, or further decrease of the value of the phase cut angle, or decrease of the value of an input signal (e.g. current).

In an embodiment of the present disclosure, the compensation module supplies the control module with the compensation signal when the sampled signal represents a dimming boundary state of the dimmer circuit. In this case, such a design provides the dimmer circuit with a specific dimming mode, which enables a corresponding regulation of the control module in accordance with the condition characterized by the sampled signal, so as to realize the possibility of a deep dimming. It is identified through the sampled signal whether the driver circuit reaches its lower limit of the dimming range, if so, the compensation module begins to work, and supplies the control module with the compensation signal, so as to realize the desired “deep dimming”.

In a preferable embodiment according to the present disclosure, the compensation module comprises a sampling unit and a compensation signal generating unit, which acquires a first signal characterizing the sampled signal through the sampling unit and generates the compensation signal in accordance with a comparison result between the first signal and a threshold value. In this case, the compensation module selectively determines whether the dimmer circuit is in the dimming boundary state, so as to decide whether it is necessary to send the compensation signal to the control module.

It is preferable that the compensation signal generating unit comprises a trigger unit and a compensation unit, the trigger unit acquires the first signal through the sampling unit and starts to supply the compensation unit with a trigger signal when the first signal is less than a DC power voltage as the threshold value, while the compensation unit supplies the control module with the compensation signal in accordance with the trigger signal. In this case, through the interaction between the trigger unit and the compensation unit, a signal for further control can be supplied to the control module in accordance with the signal of the sampling unit, so as to effectively and simply regulate the dimming effect of the driver circuit.

It is preferable that the trigger unit comprises a first transistor that turns on and outputs the trigger signal when the first signal is less than the DC power voltage as the threshold value. As core component of the trigger unit, the first transistor simply compares the threshold value and the first signal, and functions in the form of a switching element according to the comparison result, so as to discontinuously supply trigger signals.

It is preferably that the trigger unit further comprises a shunt branch, the reference electrode of the first transistor is in connection with the DC power voltage, the control electrode is in connection with the output of the sampling unit, and the working electrode is grounding through the shunt branch. Said shunt branch provides the trigger unit with environment for stable operation, which assures the safety of said trigger unit and simultaneously ensures the stability of electrical signals.

It is preferable that the shunt branch comprises a first resistor, a second resistor and a first capacitor, the first resistor and the first capacitor connected that are in series are connected in parallel with the second resistor, wherein the output of the trigger unit is located between the first resistor and the first capacitor. Said first and second resistors provide the unit, in which they are present, with electrical signals after current limiting, and realize normal operation of the transistor and ensure the operation safety of the circuit, while the first capacitor has the function of filtering signals to assure the stability of electrical signals.

It is preferable that the compensation unit comprises a second transistor as an amplifier. As core component of the compensation unit, said second transistor supplies proper and stable control signals to a downstream unit according to signals from the upstream unit.

It is preferable that the compensation unit further comprises a voltage stabilizing element, the anode of the voltage stabilizing element is in connection with the control electrode of the second transistor, and the cathode is in connection with the output of the trigger unit. As another core component of said compensation unit, said voltage stabilizing component stabilizes the voltage of said compensation unit, and said compensation unit supplies a downstream unit with electrical signals according to said stabilized voltage.

It is preferable that the voltage stabilizing element is at least one Zener diode. Zener diode is a simple and effective voltage stabilizing element. Thus, one or more Zener diodes connected in series can be selected as voltage stabilizing element according to actual situation.

It is preferable that the compensation unit further comprises a third resistor, one end of the third resistor is in connection with the reference electrode of the second transistor, while the other end is in connection with the control module to provide the compensation signal. The third resistor influences the strength of electrical signals provided by the second transistor for a downstream unit, and the value of the compensation signal can be changed by changing the value of the third resistor.

It is preferable that the sampling unit comprises a voltage dividing branch formed by a fourth resistor and a fifth resistor connected in series, one end of the voltage dividing branch is connected between the control module and the output module, while the other end is grounding. A desired dimming effect can be achieved by properly selecting the values of the fourth and fifth resistors.

It is preferable that the sampling unit further comprises a first diode, the anode of the first diode is connected between the fourth resistor and the fifth resistor, while the cathode of the first diode is in connection with the DC power voltage, and a node between the anode of the first diode and the fifth resistor forms the output of the sampling unit. The first diode defines the flow direction of the electrical signals at this part, and it is prevented thereby that the DC power voltage of high potential flows to the voltage dividing branch.

It is preferable that the sampling unit further comprises a second capacitor which is connected in parallel with the fifth resistor. The second capacitor is capable of filtering unnecessary electrical signals out, and assuring working stability of said sampling unit, so that the downstream compensation unit can work effectively and stably.

It is preferable that the control module comprises an IC controller, wherein the input signal and the compensation signal are respectively inputted into a first input and a second input of the IC controller, and the output of the IC controller supplies the control module with a control signal. According to said control signal, the output current of the output module can have further changes, in particular, can be further lessened.

It is preferable that the output module comprises a third transistor and a transformer, the control electrode of the third transistor is in connection with the output of the IC controller, the working electrode is in connection with a primary coil of the transformer, the reference electrode is on one hand in connection with the second input through a eighth resistor and on the other hand in connection with ground through a sixth resistor. Said third transistor can be a field effect transistor, which, as a core component of said output module, controls the value of signal output of said module, so as to realize variation of output current of the driver circuit.

Various embodiments further provide an LED lighting device. Said LED lighting device includes an LED component as load, and further comprises the dimmer circuit according to the above description. Said dimmer circuit allows the LED lighting device to have a further deep dimming, even when reaching the lower limit of the dimming range.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description refers to the accompanying drawing that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced.

FIG. 2shows a schematic block diagram of a dimmer circuit100according to the present disclosure. As shown inFIG. 2, said novel dimmer circuit100can be modularized into a plurality of units for realizing different functions, for example: a rectification module1, a control module2, an output module3and a compensation module4. The control module2receives an input signal S1from a power network after being rectified through the rectification module1, and controls the output module3to supply a load with an output signal S2in accordance with the input signal S1. Moreover, in order to achieve the object of the present disclosure, said dimmer circuit100further comprises the compensation module4, which collects sampled signals S3characterizing dimming state of the dimmer circuit100between the control module2and the output module3, and supplies the control module2with a compensation signal S4in accordance with the sampled signal S3, the control module2then changes the value of the output signal S2according to the input signal S1and the compensation signal S4. Hereby, the object for a deep dimming of the dimmer circuit100is achieved.

FIG. 3shows the circuit diagram of an embodiment of the dimmer circuit100according to the present disclosure. As shown inFIG. 3, the compensation module4comprises a sampling unit41and a compensation signal generating unit42. Said sampling unit41comprises a first diode D1, a fourth resistor R4, a fifth resistor R5and a second capacitor C2. The second capacitor C2and the fifth resistor R5form a bypass circuit after being connected in parallel with each other, wherein the effect of filtering undesired communication signals out can be achieved and the working stability of the sampling unit is assured. The anode of the first diode D1is connected between the fourth resistor R4and the fifth resistor R5, and the cathode of the first diode D1is in connection with a DC power voltage VCC, and a node between the anode of the first diode D1and the fifth resistor R5forms the output K41of the sampling unit41. Moreover, a voltage dividing branch is formed by the fourth resistor R4and the fifth resistor R5that are connected in series, one end of said voltage dividing branch is connected between the control module2and the output module3, while the other end is grounding.

In this case, the compensation signal generating unit42acquires a first signal S6characterizing the sampled signal S3through the sampling unit41described above and generates the compensation signal S4in accordance with a comparison result between the first signal S6and a threshold value. The compensation module4supplies the control module2with the compensation signal S4, when the sampled signal S3represents a dimming boundary state of the dimmer circuit100, viz. when reaching the lower limit of the dimming range.

FIG. 3further shows that the compensation signal generating unit42further comprises a trigger unit421and a compensation unit422. The trigger unit421comprises a first transistor Q1, a first resistor R1, a second resistor R2and a first capacitor C1. The first transistor Q1turns on and outputs a trigger signal S7, when the first signal S6is less than the DC power voltage VCC as the threshold value. Moreover, the first resistor R1, the second resistor R2and the first capacitor C1form a shunt branch, in particular, the first resistor R1and the first capacitor C1that are connected in series are connected in parallel with the second resistor R2, wherein the output K421of the trigger unit421is located between the first resistor R1and the first capacitor C1. The reference electrode of the first transistor Q1is in connection with the DC power voltage VCC, the control electrode is in connection with the output K41of the sampling unit41, and the working electrode is grounding through the shunt branch. The trigger unit421acquires the first signal S6through the sampling unit41and opens to supply the compensation unit422with the trigger signal S7when the first signal S6is less than the DC power voltage VCC as the threshold value, while the compensation unit422supplies the control module2with the compensation signal S4in accordance with the trigger signal S7.

The compensation unit422, as shown inFIG. 3, comprises a second transistor Q2, a voltage stabilizing element and a third resistor R3. As an amplifier, the second transistor Q2supplies the downstream unit, viz. the control module2, with a proper and stable compensation signal S4according to the trigger signal S7from the upstream unit, viz. the trigger unit42. Moreover, one Zener diode D5is used here as voltage stabilizing element, the anode of said voltage stabilizing element is in connection with the control electrode of the second transistor Q2, and the cathode is in connection with the output K421of the trigger unit421. Furthermore, the third resistor R3functioning for current limiting has one end in connection with the reference electrode of the second transistor Q2, and the other end in connection with the control module2to provide the compensation signal S4.

In an unshown embodiment, a plurality of Zener diodes connected in series can be used as voltage stabilizing element.

FIG. 3further shows a detailed drawing of the control module2and the output module3. The control module2comprises an IC controller IC, wherein the input signal S1and the compensation signal S4are respectively inputted into a first input K1and a second input K2of the IC controller IC, and the output K3of the IC controller IC supplies the control module3with the control signal S5. The output module3comprises a third transistor Q3and the transformer TX1, the control electrode of the third transistor Q3is in connection with the output K3of the IC controller IC, the working electrode is in connection with a primary coil P1of the transformer TX1, the reference electrode is on one hand in connection with the second input K2through a eighth resistor R8and on the other hand in connection with ground through a sixth resistor R6. In this way, through the third resistor R3, the compensation unit422can supply the control module2with the compensation signal S4combined with the eighth resistor R8, so as to realize further control over the output module3, specifically, can influence the main current of the transistor Q3of the output module3for instance.

Ip=(V⁢⁢2-VD⁢⁢5-Vsense)*R⁢⁢8R⁢⁢3+VsenseR⁢⁢6,
wherein V2represents the voltage at the node K421, VD5represents the voltage of the voltage stabilizing element D5, Vsense, viz. the compensation signal S4, represents the voltage between the eighth resistor R8and the third resistor R3.

By comparing the schematic diagrams of output current of a dimmer circuit100respectively shown inFIG. 1(the prior art) andFIG. 4(in accordance with the present disclosure), the effect of “deep dimming” realized by the dimmer circuit100according to the present disclosure can be clearly identified. For example, during a dimming process, in a situation of the same input voltage, the value of the output current Io1of the dimmer circuit according to the prior art is relatively larger, as shown inFIG. 1; while the value of the output value Io2of the dimmer circuit100with the compensation module4according to the present disclosure is less with respect to Io1, as shown inFIG. 4. Through the comparison between the output currents Io1and Io2ofFIGS. 1 and 4, it can be determined that a less output current can be obtained in the embodiment of the dimmer circuit100according to the present disclosure, compared with a dimmer circuit without a compensation module.

LIST OF REFERENCE SIGNS