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.
Various embodiments relate to a dimmer circuit and an LED lighting device having said dimmer circuit.
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 in
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.
In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being replaced upon illustrating the principles of the disclosure. In the following description, various embodiments of the disclosure are described with reference to the following drawings, in which:
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.
In this case, the compensation signal generating unit 42 acquires a first signal S6 characterizing the sampled signal S3 through the sampling unit 41 described above and generates the compensation signal S4 in accordance with a comparison result between the first signal S6 and a threshold value. The compensation module 4 supplies the control module 2 with the compensation signal S4, when the sampled signal S3 represents a dimming boundary state of the dimmer circuit 100, viz. when reaching the lower limit of the dimming range.
The compensation unit 422, as shown in
In an unshown embodiment, a plurality of Zener diodes connected in series can be used as voltage stabilizing element.
wherein V2 represents the voltage at the node K421, VD5 represents the voltage of the voltage stabilizing element D5, Vsense, viz. the compensation signal S4, represents the voltage between the eighth resistor R8 and the third resistor R3.
By comparing the schematic diagrams of output current of a dimmer circuit 100 respectively shown in
While the disclosed embodiments have been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosed embodiments as defined by the appended claims. The scope of the disclosed embodiments is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.
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