The present invention relates to horns. More particularly, the present invention relates to a system and a method to enhance efficiency and lifetime of a horn.
A horn is an electro-mechanical device which produces sound due to oscillations of a diaphragm. This sound is generated when the oscillations are produced by the diaphragm during ON-OFF cycle. During ON-OFF cycle, a coil in a contactor assembly is energized and de-energized respectively. A conventional electromechanical horn consists of a disc type diaphragm as shown in Fig. 1. Initially the diaphragm is in a stationary position. When the switch is closed, it allows current to flow through the coil thereby energizing the coil and creating a magnetic field. This magnetic field magnetizes an anchor bolt due to which an armature gets attracted towards it. A spring placed in between the anchor bolt and the armature is thus compressed when the diaphragm moves towards the coil. The said coil and the spring comprise a contactor assembly. The movement of the contactor assembly is controlled by action of the spring wherein the contactor movement opens/closes the electro-mechanical switch. The coil in the contactor assembly energizes and de-energizes during the ON-OFF cycle. During the ON period the coil gets energized and magnetic energy gets stored in the inductor and gets de-energized during OFF period. The magnetic energy stored in the inductor which could not be converted into mechanical/sound energy has to be removed before the next ON period, otherwise the coil would get saturated and not be able to hold any voltage. In such a case, the coil would behave like a resistor and not an inductor. Therefore, during the OFF cycle, the stored energy in the inductor is dissipated in the form of heat or arcs produced between the contacts. Thus, energy is lost during operation of the horn, The existing systems and methods to some extent utilize the stored energy of the inductor but have limited efficiency. Further systems and methods that form arcs in between the contacts create ozone which is highly corrosive, resulting into limited life of conventional contactor assembly in case of electro-mechanical horn. Also, the usage of expensive MOSFETs, TVS diodes to dissipate energy during turn off cycle in conventional electronic horn makes the system expensive and also the heat dissipation is a form of energy wastage. Thus, there is a need to devise a mechanism that mitigates the above mentioned drawbacks.
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It is an object of the present invention to provide a system and method that enhances efficiency of the horn.
It is another object of the present invention to provide a system and method that reduces heating and improves reliability of the horn.
It is yet another object of the present invention to provide a system and method that reduces or eliminates generation of arc between contacts in a horn.
It is still another object of the present invention to provide a system and method that eliminates the need of clamping or dissipating high energy across semiconductor switch based horn.
It is still another object of the present invention to provide a system and method that leads to a generation of economical horns.
The present invention relates to a system and a method to enhance efficiency and lifetime of a horn. The present invention discloses a hom including a fist coil and a second coil for transferring the magnetic energy; a buffer/storage capacitor for storing the magnetic energy; and a means to transfer stored energy into the first coil and produce sound. The present invention increases the efficiency of the hom by storing energy that Is not used in the capacitor during the OFF cycle and re-using the same In the next ON cycle, instead of just wasting It in the form of heat.
In one aspect of the invention, the system for Improving efficiency and lifetime of a horn comprises a first power supply for switching the horn between ON and OFF modes; a first inductor coupled to the first power supply means through a first diode; a transient-voltage-suppression (TVS) diode coupled to the first inductor; a storage capacitor coupled to the first
inductor through the TVS diode; and a second inductor coupled to the first inductor through a second diode wherein the second diode is reverse biased during ON mode of the horn and forward biased during OFF mode of said hom such that the magnetic energy stored In said first inductor during ON mode Is transferred to the storage capacitor during the OFF mode, which is then used in next ON mode of said horn.
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In another aspect of the invention, a method for improving efficiency and lifetime of a horn is disclosed. The method, according to the invention, comprises the steps of a) supplying power to a first inductor of the horn through a first power supply and first diode, to switch the horn between ON and OFF modes; b) energizing the first inductor during ON mode of the horn; polarizing a second inductor through the first inductor; d) de-energizing the first inductor during OFF mode by transferring energy stored in the first inductor to the second inductor; and e) transferring energy from the second inductor to the storage capacitor through a second diode.
In yet another aspect, the first inductor of the system includes bifilar windings of same diameter with lesser or equal number of turns to charge the storage capacitor during OFF mode.
In still another aspect, the diodes used in the system are Schottky diodes for reducing the diode power loss during energy transfer to the storage capacitor.
The accompanying drawings constitute a part of the description and are used to provide further understanding of the present invention. Such accompanying drawings illustrate the embodiments of the present invention which are used to describe the principles of the present invention together with the description.
Figure 1 illustrates a conventional electro-magnetic horn with disc type diaphragm;
Figure 2 illustrates circuit diagram of an electro-magnetic hom including the system for improving the efficiency and lifetime of the horn, according to an embodiment of the present invention; and
Figure 3 illustrates the schematic view of an electro-magnetic horn with disc type diaphragm including the system for improving the efficiency and lifetime of the hom, according to an embodiment of the present invention.
Figure 4 illustrates a flowchart of the various steps involved in a method for improving the efficiency and lifetime of a horn, according to an embodiment of the invention.
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The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present mvention may be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the pxirpose of providing a thorough understanding of the present mvention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
Figure 2 illustrates circuit diagram of a horn including the system for improving the efficiency and lifetime of the horn according to an embodiment of the present invention. According to an embodiment of the present invention, the objects of the invention are
achieved by including a second coil (L2) for transferring the magnetic energy; a buffer capacitor (CI) for storing the magnetic energy; and a means to transfer stored energy into the main coil and produce sound. In the present invention, the energy is stored in the capacitor and is reused in the next cycle, instead of just wasting it in the form of heat. According to an embodiment of the present invention, the efficiency of the electronic horn is increased by the means of an additional coil (L2) known as a flyback coil, and a storage capacitor (CI). The system according to an embodiment of the present invention includes a first main power supply (VI) for switching the horn between ON and OFF modes. The system further includes a first diode (Dl) connected to a first inductor (LI). The first inductor (LI) is connected to the first power supply (VI) through the first diode (Dl). a first inductor (LI) coupled to said first power supply means through a first diode (Dl). The first diode (Dl) is used for reverse polarity protection of the electric horn. The system farther includes a transient-voltage-suppression (TVS) diode (D3) coupled to said first inductor (LI); a storage capacitor (Cl) coupled to the first inductor through the TVS diode; and a second inductor (L2) coupled to the first inductor (LI) through a second diode (D2). The primary objective of the mvention is to store the energy stored in the first inductor (LI) in the capacitor (Cl) rather than dissipating it as heat and using it back in next cycle. The energy stored in the first inductor (LI) is transferred to the capacitor (Cl) through the second inductor (L2) and the second diode (D2), which is coupled to the first inductor (LI). However, the coupling in the second

coil can not be 100% efficient, it can be somewhere around 98% in best conditions. The remaining 2% is still in the first inductor (LI), which needs to be dissipated as heat before next cycle starts. The TVS diode helps in dissipating that 2% energy stored in the first inductor (LI). In another embodiment, the system also includes a third diode (D4) connected to the TVS diode (D3), to avoid the forward biasing of the TVS diode during ON mode.
During turn ON mode, the current though the inductor LI (Horn Coil) rises, and energy is stored in it. During this period, dotted end of both inductors are positive with respect to their respective non-dotted ends. Hence, at this time the diode D2 is reverse biased along with diode D4.
At the moment of turn OFF i.e. during OFF mode, the polarity of voltage changes in first inductor (LI). This tries to maintain the current in the first inductor (LI) in the same direction (as per Lenz's law), and so in the second inductor (L2). Thus, the second diode (D2) gets forward biased, and conducts to transfer the stored magnetic energy in the capacitor. By doing so, the voltage across the capacitor increases.
1 -, 1
~~* L* I = -— * C*V
2 2
The above mentioned equation decides the change in capacitor voltage above its input voltage, and helps to select the capacitor for desired voltage rise. The uncoupled energy in the second inductor (L2) can be dissipated in the parallel TVS diode (D3) or any other conventional method. Being a bifilar winding, most of the energy is coupled to the second inductor (L2) and gets transferred to the capacitor.
In another embodiment, the invention uses another bifilar windings of same diameter with lesser or equal number of turns, to charge the storage capacitor during turn OFF. Thus the stored energy in the magnetic field is transferred in the capacitor and is utilized in the next turn ON cycle. The number of turns together with the value of capacitor, in the secondary winding gives us the flexibility of maximum clamped voltage and current to be handled but within the constraint of OFF mode only. The use of bifilar windings is well known to achieve maximum coupling between the inductors. The present invention may use other known ways of achieving better coupling.
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The only losses in the process are leakage energy in the uncoupled magnetic field; copper loss in the second coil; forward drop loss in the second diode (D2); and loss in the Equivalent Series resistance (ESR) of capacitor. All these losses are non-significant as compared to that in the conventional horn. The losses can be further minimized by using bifilar winding as mentioned for better coupling; increasing diameter of wire for lesser copper loss in the coil; use of Schottky diode to reduce diode power loss during energy transfer in the capacitor; and use of higher value of capacitance to have lower ESR and hence reduce losses in the capacitor.
In the next turn ON cycle, the coil takes energy from storage capacitor, till the capacitor
voltage drops to that of input voltage. Thus, as the energy is taken from the storage capacitor energy is saved during operation of the electronic horn and the object of the invention is achieved.
In another embodiment, the first inductor (LI) is coupled to at least two resistors (Rl, R2) through a switch (Ml) and the at least two resistors (Rl, R2) are connected to a second power supply (V2). The second power supply provides Pulse- width modulation (PWM) to the switch (Ml), and thereby controls the said switch (Ml). In a preferred embodiment, the switch (Ml) is a MOSFET. The switch (Ml) is used to connect and disconnect the first inductor (LI).
Figure 3 illustrates the cross-sectional view of the horn including the system for improving
the efficiency and lifetime of the horn according to an embodiment of the invention. In the embodiment, the storage capacitor and second diode are connected to the first coil. The coil is provided with bifilar winding of same diameter with lesser or equal number of turns, to charge the storage capacitor during turn OFF.
Figure 4 illustrates the various steps involved in the method for improving the efficiency of the electromagnetic horn. In an embodiment, the method includes the following steps: at first, the first power supply provides power to the horn so as to switch it between the ON and OFF modes (Step 402). During the ON mode, as the current Is supplied to the first inductor, energy Is stored in the said Inductor (Step 404). Hence, the second inductor (L2) coupled to the first inductor (L2) is polarised (Step 406). When the power is switched off through the switch (Ml) i.e. during OFF mode, the first inductor is de-energised and the energy stored in
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the first inductor is directed or transferred to the second inductor, which causes the second diode to be forward biased (Step 408). Due to the forward biasing of the second diode (D2), energy from the second inductor (LI) is transferred to the storage capacitor (CI) (Step 410). Thus the energy from the first inductor, instead of being dissipated in the form of heat, is stored in the capacitor, which can be used in the next ON cycle of the horn. It is however found that since the coupling of the first inductor (LI) and the second inductor (L2) is not always 100% efficient, and a residual energy is always left in the first inductor, it is imperative that this residual energy is also transferred or dissipated. This dissipation of the residual energy is done by the TVS diode (D3), which are connected in parallel to the first inductor (LI).

We claims:-
1. A system for improving efficiency and lifetime of a horn comprising:
a first power supply (VI) for switching said horn between ON and OFF modes;
a first inductor (LI) coupled to said first power supply means through a first diode
(Dl);
a TVS diode (D3) coupled to said first inductor (LI);
a storage capacitor (CI) coupled to said first inductor through said TVS diode; and
a second inductor (L2) coupled to said first inductor (LI) through a second diode
(D2); wherein said second diode (D2) is reverse biased during ON mode of said horn and forward biased during OFF mode of said horn such that the magnetic energy stored in said first inductor (LI) during ON mode is transferred to said storage capacitor (CI) during the OFF mode, which is then used in next ON mode of said horn.
2. The system as claimed in claim I, wherein said first inductor (Li) includes bifilar windings of same diameter with lesser or equal number of turns to charge said storage capacitor (CI) during OFF mode.
3. The system as claimed in claim 1, wherein the diodes used in said system are Schottky diodes for reducing the diode power loss during energy transfer to said storage capacitor (CI).
4. A method for improving efficiency and lifetime of a horn comprising the steps of:

a) supplying power to a first inductor (LI) of said horn through a first power supply (VI) and first diode (Dl), to switch said horn between ON and OFF modes;
b) energizing said first inductor (LI) during ON mode of said horn;
c) polarizing a second inductor (L2) through said first inductor (LI);
d) de-energizing said first inductor (LI) during OFF mode by transferring energy
stored in said first inductor (LI) to said second inductor(L2); and
e) transferring energy from said second inductor (L2) to a storage capacitor (CI)
through a second diode (D2).

5. The method as claimed in claim 4, wherein the energy transferred to said storage capacitor (CI) is used in next ON cycle of said horn.
6. The method as claimed in claim 4, wherein said first inductor (LI) is connected to a TVS diode (D3) for dissipating residual energy in said first inductor (LI).
7. The method as claimed in claim 4, wherein said first inductor (LI) includes bifilar windings of same diameter with lesser or equal number of turns to charge said storage capacitor (CI) during OFF mode.