Abstract:
A power supply of luminous sources is disclosed comprising a first circuit configured to generate a direct voltage signal from an alternating input voltage and a second circuit having in input the direct voltage signal and configured to generate an alternating voltage signal of rectangular wave shape and null average value. The power supply comprises: a third circuit configured to generate a current signal of triangular wave shape from the alternating voltage signal, a fourth circuit configured to extract from the current signal a voltage signal of triangular wave shape and non-null average value, a fifth circuit configured to control the frequency of the alternating voltage signal based on the average value of the voltage signal extracted by the fourth circuit, a sixth circuit configured to rectify said current signal and supply the luminous sources.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure refers to a power supply of luminous sources, in particular power LED diodes. 
     2. Description of the Related Art 
     Power supplies are known for LED diodes that comprise a direct voltage source, a DC/DC converter suitable for supplying the LED diodes arranged in series or parallel to each other and at least a sense resistance. If the LED diodes are arranged in series there is uniform light due to the same current that circulates in the diodes but there is the drawback of high supply voltage. If the diodes are arranged parallel to each other the supply voltage is lower but the light of the diodes may undergo variations; further, ballast resistances are used to equalize the currents in all the diodes at the expense of efficiency. 
     On the market there are currently circuit types of the flyback type for supplying LED diodes. Said circuit types have various drawbacks in the event of use for high output power: great circuit complexity for independent adjustment for each branch of LED diodes of the light flow, significant dimensions, need for the output transformer to be made with low leaked inductance in order to contain losses, problems linked to the buzz of the cores during adjustment of the light flow and high costs. 
     BRIEF SUMMARY 
     One embodiment is a high-performance power supply of luminous sources that is more efficient than known power supplies. Said power supply is shown to be particularly useful in the case of supplying LED diodes or other luminous sources that are able to operate with supply currents up to 1.5 A and nominal operating voltages of about 3.5 V. Further, as a normal power supply has output power of approximately 100 W, the power dispensable by the power supply can be distributed between several channels to conform to regulations governing the maximum voltage permitted to supply the LED diodes. The plurality of output channels allows a light flow with chromatic variability arising from the mixture of flows operating on three basis colors, with the intensity of each being adjustable independently of the others. 
     One embodiment is a power supply for luminous sources comprising: 
     first means suitable for generating a direct voltage signal starting with an alternating input voltage, 
     second means having in input said direct voltage signal and being suitable for generating an alternating voltage signal of rectangular wave shape and null average value, 
     third means suitable for generating a current signal of triangular wave shape from the alternating voltage signal of rectangular wave shape and null average value, 
     fourth means suitable for extracting from said current signal of triangular wave shape, a voltage signal of triangular wave shape and non-null average value, 
     fifth means suitable for controlling the frequency of the alternating voltage signal of rectangular wave shape and null average value in function of the average value of the output voltage signal from said fourth means, 
     sixth means suitable for rectifying said current signal of triangular wave shape coming from said third means and being suitable for supplying the luminous sources. 
     One embodiment is a power supply for luminous sources that is very reliable and has efficiency that is greater than that of known power supplies. 
     In one embodiment, the multichannel power supply is capable of distributing the output power between several channels, each with limited supply voltage and with a stabilized output current. 
     Further, said power supply enables the output current stabilized for each channel to be selected from a wide range of values. 
     The power supply comprises a sole controller circuit intended for simultaneously stabilizing the output currents keeping the independent adjustment thereof possible. 
     The power supply is made in a simple manner and at reduced costs for each light point. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The features and advantages of the present disclosure will become clear from the following detailed description of an embodiment illustrated by way of non-limiting example in the attached drawings, in which: 
         FIG. 1  is a diagram of the power supply of luminous sources according to one embodiment; 
         FIG. 2  shows in greater detail a part of the power supply in  FIG. 1 ; 
         FIG. 3  shows the wave shapes of the signals in play in the circuit in  FIG. 2 ; 
         FIG. 4  shows in greater detail a device of the power supply in  FIG. 1 ; 
         FIG. 5  shows the wave shape of the output signal from the device in  FIG. 4 ; 
         FIGS. 6-10  show in greater detail other components of the power supply in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1-10 , there is shown a power supply  100  of luminous sources  81   dl   1 - 8   ndln , in particular LED diodes, according to one embodiment. The power supply  100  comprises ( FIG. 1 ) a first device  1  that is supplied by the mains voltage Vin and is suitable for containing conducted mains electromagnetic interference within the limits set by standards. The output voltage signal from the device  1  is corrected by the device  2 ; the corrected voltage signal Vr is an input signal to a device  3  that is suitable for providing stabilized direct voltage Vcs maintaining the network harmonics content conformant to the standards; said device  3  is, for example, a PFC device, a power factor corrector. 
     The stabilized direct voltage signal Vcs is sent to an inverting device  4  suitable for emitting an alternating voltage signal Vsr of rectangular shape with null average value; the frequency of the signal Vsr is controlled by means outside the device  4 . 
     The voltage Vsr coming from the device  4  is sent to the inductor  5  that is in series at the subsequent block  6 ; preferably, in the case of multichannel power supplies, the inductor  5  is in series also to a plurality of blocks  71  . . .  7   n  ( FIG. 2 ). The amplitude of said voltage Vsr is comprised between 200 V and 220 V. The current Isr that circulates through the inductor  5  is alternating, symmetrical, triangular in shape and the amplitude thereof, in the absence of feedback, depends on the frequency of the voltage Vsr; the wave shapes of the current Isr and of the voltage Vsr are shown in  FIG. 3 . 
     The current Isr is processed by the device  6  that uses the positive part thereof, creating a voltage V 6  that is suitable for reproducing the shape of the positive part of the current Isr ( FIG. 4 ). The device  6  comprises a diode  15  that is parallel to the series of a second diode  16  and a resistance  17 ; preferably the device  6  comprises a transformer  18 , the primary winding of which is connected between the input terminals of the block  6  and a secondary winding connected parallel to the diode  15  and to the series of the second diode  16  and of the resistance  17 . The diode  16  enables only the positive part of the current Isr received from the secondary winding of the transformer  18  to flow on the resistance  17  to form the voltage V 6  ( FIG. 5 ); the diode  15  ensures that the negative part of the current recirculates on the secondary winding of the transformer  18 . The average value Vm 6  of the voltage V 6  is detected by the device  4  that tries to maintain the average value Vm 6  constant, adjusting the operating frequency of the device  4 . The transformer  18  enables leakage on the components  15 ,  16  to be reduced, contributing to increasing the performance of the invention. 
     The device  4 , better visible in  FIG. 9 , comprises a device  41 , indicated by way of example by a switch, that is suitable for deactivating the device  4  when a voltage signal V 9  is received from a device  91 ,  92  . . .  9   n , an inverter  42  supplied by the voltage Vcs and suitable for generating the voltage Vsr and a circuit  43  for driving the inverter  42 . The circuit  43  is suitable for extracting the average value Vm 6  of the voltage V 6  generated by the device  6 ; once the average value Vm 6  of the voltage V 6  is known the maximum value Vmax 6  of the voltage is known automatically and it is possible to modify the frequency of the signal Vcs in response to the value of the maximum value Vmax 6  of the voltage V 6 . The circuit  43  tends to maintain the maximum value Vmax 6  of the voltage V 6  constant and acts on the inverter  42  to increase or decrease the frequency of the signal Vsr when the maximum valueVmax 6  exceeds or is less than a reference value Vmax 6 ref. 
     The triangular current Isr is sent to a plurality N of transformers  71  . . .  7   n  having the primary windings connected in series ( FIG. 6 ). The number of said transformers corresponds to the number of output channels from the power supply. Once the current Isr power supply of luminous sources has been stabilized (which circulates in the primary windings) the currents I 71  . . . I 7   n  power supply of luminous sources are stabilized (which circulate in the secondary windings); each of these currents can assume different values according to the respective transformation ratio K 71  . . . K 7   n  of each transformer, so also high-value output currents can be controlled by a sole low-value current, contributing to raising the performance of the device  100 . 
     The currents I 71  . . . I 7   n  are corrected and leveled by the devices  81  . . .  8   n  that comprise diodes and capacitors ( FIG. 7 ); the terminals  71   a - 71   c,    72   a - 72   c , . . .  7   na - 7   nc  are the input terminals of the respective devices  81 ,  82  . . .  8   n . The capacitors have to manage the ripple component of the currents I 71  . . . I 7   n  which, in the absence of the capacitors, would flow in the LED diodes without being productive in terms of light flow but leakage would increase, reducing the life of the LED diodes, lowering the overall performance thereof. To each device  81  . . .  8   n  a chain of LED diodes  81   dl   1  . . .  81   dln , . . .  8   ndl   1  . . .  8   ndln  is connected at the respective output terminals  81   a - 81   b ,  82   a - 82   b , . . .  8   na - 8   nb.    
     Each transformer  71  . . .  7   n  is provided with a tertiary winding  91  . . .  9   n  ( FIG. 8 ); the tertiary windings  91  . . .  9   n  have a common terminal  21  and have the other terminal connected to the series of a resistance  91   r  . . .  9   nr , a diode  91   d  . . .  92   d  and a Zener diode  91   zd  . . .  9   nzd  the anodes of which are connected together at a terminal  22 . The voltage signal V 9  located between the terminals  21 - 22  is sent to the device  4  so as to suspend operation only when one of the Zener diodes  91   zd  . . .  9   nzd  starts conducting. This event occurs when the amplitude of the voltage on a tertiary winding is greater than a preset value and also the output voltage of each channel is automatically limited, this output voltage being closely connected to the intervention voltage of the Zener diode. 
     With each device  81  . . .  8   n  there is associated a device  101  . . .  10   n  suitable for controlling the light flow independently of the other channels ( FIG. 10 ). 
     Each device  101  . . .  10   n  comprises two transistors MOS M 1  and M 2  driven by a step signal D and by the negated signal thereof; the signal D is generated from the outside at a fixed frequency of about 100 Hz, at a frequency that is not visible to the human eye. The transistors MOS M 1  and M 2  have a common conduction terminal (source terminal) connected to the central terminal  71   c ,  72   c  . . .  7   nc  of the respective secondary winding of the transformer  71  . . .  7   n  and the other conduction terminal (drain terminal) connected respectively to the cathodes of a pair of diodes D 1  and D 2  connected in turn to the terminals of the secondary winding of the respective device  71  . . .  7   n  and to the negative terminal  81   a ,  82   a , . . .  8   na  of the respective chain of LED diodes supplied by the device  71  . . .  7   n . The check is implemented by checking the duration of the step of the signal D. During the voltage step of the signal D the transistor M 2  is switched on and the transistor M 1  is switched off; the current stabilized by the respective device  81 ,  82  . . .  8   n  is sent to the respective chain of LED diodes. In the absence of a voltage step, the transistor M 1  is switched on and the transistor M 2  is switched off; the output current from the respective transformer  71 ,  72  . . .  7   n  is sent to the transistor MOS M 1  and to the respective terminal  71   c ,  72   c  . . .  7   nc . During the check or adjustment the amplitude of the triangular wave shape of the current that flows on the primary winding or on the secondary winding of the transformers is not substantially altered but only the frequency and the triangular shape; the output current of the other channels remains stable and the power leaked by the device  3  is reduced. Further, said control device does not create acoustic vibration problems for the cores of the transformer. 
     Preferably, in order to prevent slight visible frequency variations of the light flow, all the timings, i.e., the duration of the steps and the frequency of the repetition thereof, are set by a numeric control and the start of the interval in which the LED diodes are supplied is synchronized for all the channels. 
     In the case of a sole-channel power supply the current Isr coming from the device  5  will be sent to a sole device  81  suitable for correcting and leveling the current Isr; preferably, to increase the performance of the power supply, it is possible to place between the devices  5  and  81  a sole transformer  71  with a sole primary winding and a sole secondary winding. The corrected current Isr will be sent to the plurality of diodes  81   dl   1  . . .  81   dln ; the use of a sole device  91  and a sole device  101  is provided. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.