Patent Description:
A notification appliance may include a notification horn that generates a sound at predetermined intervals with a predetermined acoustic pattern. The notification appliance is typically rated at the lowest sound output and the highest input current across its specified working input voltage range. The sound output may increase in response to increasing input voltage. However, the increased sound output is typically not utilized for rating the notification appliance. Accordingly, any increase in current beyond that required to provide the lowest sound output is not efficient. Manufacturers are continually seeking to improve efficiencies in the manufacture and operation of notification appliances.

Document <CIT> discloses an audible alarm device, comprising a piezoelectric buzzer, a coil connected in parallel to the piezoelectric buzzer, switching means for adjusting a current supply period for he piezoelectric buzzer and coil, control means for controlling on/of operation of the switching means, and current limiting means for limiting a current to the coil, the current limiting means being connected in series to the coil and the piezoelectric buzzer.

Document <CIT> discloses a notification appliance circuit (NAC) comprising a plurality of notification device, each device including a strobe circuit and an energy storage device for supplying electrical energy to the strobe circuit to generate light flashes.

Document <CIT> discloses a system comprising an energy storage capacitor, means for periodically discharging the energy storage capacitor into a load, and a power supply for resupplying energy to the energy storage capacitor between discharges, and a method of controlling resupplying energy to the energy storage capacitor comprising determining a time interval between subsequent discharges of the energy storage capacitor; and regulating the energy output of the power supply to resupply energy to the energy storage capacitor over substantially the entire interval between subsequent discharges of the the energy storage capacitor.

Document <CIT> discloses a control circuit for a speaker configured to have a predetermined resonance frequency, the control circuit comprising: a speaker driver; a controller in communication with the speaker driver, the controller operable to control a drive frequency of the speaker, wherein the controller is configured to: monitor at least a sample of a current draw of the speaker in the form of a voltage signal; identify a voltage differential of the voltage signal; and adjust the drive frequency of the speaker in response to the voltage differential to maintain the resonance frequency.

A method of powering a sounder according to an exemplary embodiment of this disclosure is disclosed in claim <NUM>.

In a further embodiment of any of the foregoing methods, a power control decreases the input voltage delivered to the sound engine to reduce a sound level generated by the sound engine.

In a further embodiment of any of the foregoing methods, the power control selects from one of a several input voltage levels to provide a corresponding acoustic signal at a corresponding volume.

A notification appliance according to the invention is disclosed in claim <NUM>.

In a further embodiment of any of the foregoing notification appliances, the power control regulates the input voltage to the sound engine to provide a constant volume.

In a further embodiment of any of the foregoing notification appliances, the power control is configurable to adjust a sound level generated by the sound engine.

In a further embodiment of any of the foregoing notification appliances, the power control is configurable to select between one of several input voltage levels to provide a corresponding sound level.

A notification appliance circuit (NAC) according to the invention includes among other possible things, a plurality of notification appliances connected by circuit wiring to provide electric power, wherein at least one of the plurality of notification appliances includes a sound engine generating a sound according to an acoustic pattern, and a power control regulating input voltage from the to the sound engine that is matched to the acoustic pattern.

In a further embodiment of any of the foregoing NACs, the power control is configurable to adjust a sound level generated by the sound engine.

In a further embodiment of any of the foregoing NACs, the power control is configurable to select between one of several input voltage levels to provide a corresponding sound level.

Fire alarm and mass notification systems are used to notify the public, such as occupants of a building or campus, of the presence of fire, smoke and other potentially harmful conditions. It may be appreciated that in case of fire or other event likely to trigger use of the alarm or mass notification system, it is desirable to output sound likely to attract the attention of those within range of a notification appliance such as a sounder or horn.

Referring to <FIG>, a notification appliance circuit (NAC) <NUM> includes a control panel <NUM> that receives power from an AC power source <NUM>. The control panel <NUM> powers and controls a plurality of notification appliances <NUM> connected by a two wire circuit 18a, 18b and a termination resistor <NUM>. The control panel <NUM> may also receive power from a backup power supply <NUM>. The control panel <NUM> provides power and control signals for operation of the notification appliances <NUM>. While the example NAC <NUM> includes three notification appliances <NUM>, other numbers of notification appliances could be utilized and contemplated with the context of this disclosure. Each of the example notification appliances <NUM> include a power control <NUM> that controls power supplied to a sound engine <NUM> and a sound temporal pattern generator <NUM>.

Referring to <FIG> with continued reference to <FIG>, a portion of an example notification appliance <NUM> is schematically shown and includes the sound engine <NUM> that receives a driver current <NUM> and driver voltage <NUM> from the power control <NUM>. The sound engine <NUM> includes a transducer driver <NUM>, an electro-acoustic transducer <NUM> and an acoustic chamber <NUM> that outputs a generated sound spatial pattern <NUM>. The generated sound spatial pattern <NUM> is the sound as would be heard based on a location and orientation relative to the notification appliance <NUM>. The transducer driver <NUM> excites a piezo diaphragm and receives sound control information <NUM> from the sound temporal pattern generator <NUM>. The electro-acoustic transducer <NUM> is the piezo diaphragm and converts electrical energy into mechanical movement and acoustic energy. Although a piezo diaphragm is disclosed as an example, a sound generator of any known configuration may be utilized and is within the contemplation of this disclosure.

The sound temporal pattern generator <NUM> includes a temporal code generator <NUM>, an acoustic roughness module <NUM> and a tone generator <NUM> that supplies the sound control information <NUM> to the transducer driver <NUM>. The temporal pattern generator <NUM> generates the control information <NUM> utilized by the transducer driver <NUM> to produce sounds of different frequencies for different alarm sound patterns. A sound pattern selector <NUM> provides a signal <NUM> to the temporal code generator <NUM> and the power control <NUM>. The sound pattern selection signal <NUM> is selected by an installer at the time of installation of the appliance <NUM>. Selection of the signal <NUM> can be made by selecting one position of a four position switch to select between two sound patterns and at least two levels of sound power. It should be appreciated that other selection mechanisms could be utilized and are within the contemplation of this disclosure, including but not limited to mechanical mechanisms, and remote wireless or hardwired electronic mechanisms.

The example pattern generator <NUM> creates signals for generating sounds of different frequencies and patterns including a temporal code (T3) that provides a fire alert sound pattern. One example fire alert sound pattern provides a sound for ½ second followed by no sound for ½ second that is repeated <NUM> times followed by a delay of <NUM> second, than repeated. The temporal pattern generator <NUM> may also instruct a general alarm tone. The T3 temporal code is disclosed and explained by way of example, however, other temporal patterns could be utilized within the contemplation and scope of this disclosure including a temporal pattern that provides a Carbon Monoxide (CO) detection alert sound pattern commonly referred to as T4.

The temporal pattern generator <NUM> includes the acoustic roughness module <NUM> that generates a modulation of the sound produced that is intended to enhance the ability of the output sound pattern <NUM> to attain the attention of those being warned.

Referring to <FIG> with continued reference to <FIG>, the purpose of the sound engine <NUM>, and the output sound pattern <NUM> is to attract the attention of those within range. Accordingly, a sound waveform is selected that is effective to alert those within range. One model for the sound waveform is the human scream that provides a certain depth and amplitude modulation that is known to be effective at attracting attention. The amplitude modulation utilized to generate the desired sound is referred to as the acoustic roughness. In this disclosed example, the acoustic roughness provides a modulation frequency of around <NUM>.

The graphs shown in <FIG> show the underlying signals that generate the acoustic roughness for a fire alert sound pattern <NUM>. The fire alert sound pattern <NUM> is shown in the graph indicated at <NUM> where three periods of sound <NUM> of ½ second each are generated between ½ second intervals <NUM> of no sound. The six periods <NUM> and <NUM> are followed by a delay <NUM> of one second and then repeated again. Graphs <NUM>, <NUM> and <NUM> zoom in on one period <NUM> to show the smallest increments of actuation utilized to generate each period <NUM>. Each of the periods <NUM> comprise a number of higher frequency bursts indicated at <NUM> in graph <NUM>, and at an increased zoom in graph <NUM>. The bursts <NUM> are further generated by tones <NUM> shown in graphs <NUM> and shown in expanded form in graph <NUM>. Power indicated at <NUM> in graph <NUM> is consumed by the electro-acoustic transducer <NUM> only during the generation of tones.

The power control <NUM> receives a power control signal <NUM> from the tone generator <NUM> that predicts generation of the driver current <NUM> that powers the sound engine <NUM>. The power control <NUM> also receives the sound pattern selection signal <NUM>. Power to generate the sound pattern <NUM> is provided from the input current <NUM> from the NAC <NUM>.

If the sound engine <NUM> is configured to produce a sound at a volume that corresponds with the input voltage <NUM> from the NAC <NUM>, then any rise or change in the input voltage <NUM> from the NAC <NUM> would cause a corresponding increase in sound. Accordingly, the input voltage <NUM> from the NAC <NUM> would control the volume of the sound output from the sound engine <NUM>. As the sound power output from the sound engine <NUM> varies, so would the current input <NUM>. Performance of the notification appliance <NUM> is determined utilizing defined conditions such as input voltage and is utilized for comparison to other appliances and as a means of selecting appliances when designing and planning a NAC. The sound output and input current of the notification appliance at the defined conditions are known as that appliances rating. One example rating records a minimum sound and a maximum current across their specified operating voltage range for the appliances <NUM>. The value of the minimum sound and maximum current is identified as the rating for the appliance <NUM>. The ratings for each appliance <NUM> are used as comparison to other appliances. As appreciated, an efficient appliance minimizes the rated current required to provide the rated sound output. Sound output above the minimum sound output is not beneficial to the rating. Accordingly, increases in the input current <NUM> that result in a sound level above the minimum sound output level is a waste of current.

Referring to <FIG>, with continued reference to <FIG> and <FIG>, the example power control <NUM> includes features that control the sound output from the sound engine <NUM> and enable a constant and lower input current <NUM>. The power control <NUM> decouples the sound output from the NAC <NUM> voltage <NUM> by regulating a driver voltage <NUM> to the sound engine <NUM> to match a phase of a sound control <NUM>. The power control <NUM> includes voltage regulator functionality in the power controller <NUM> that produces a current control signal <NUM> that is used to regulate the charging current <NUM> communicated to the energy store <NUM> from a current controller <NUM>. The energy store <NUM> integrates the charging current <NUM> to provide a driver voltage <NUM> and driver current <NUM> to the sound engine <NUM>. The energy store <NUM> provides a charge level signal <NUM> to the power controller <NUM> for use in a feedback loop for determining the current control signal <NUM>.

Referring to <FIG>, with continued reference to <FIG>, the example power control <NUM> keeps the input current <NUM> constant by adjusting the current control signal <NUM> to maintain the driver voltage <NUM> at a phase <NUM> (<FIG>, graphs 56A and <NUM> B) of the voltage level selected by the sound pattern selection signal <NUM>. Graph 56A and 56B are of the same input voltage <NUM> shown in different scales to show the small variation and corresponding high and low points that correspond with the sound shown in graph <NUM>. In this example the phase <NUM> is selected to be synchronous with the transition between no sound and sound shown as phase <NUM> of graph <NUM>, however, the phase <NUM> could by any other arbitrary phase of the sound signal level cycle <NUM>. The phase <NUM> is synchronized to the power control single <NUM>. Adjustment of the current control signal <NUM> is accomplished by known methods including feed-forward, proportional integral derivative, or proportional integral controller.

The disclosed input current <NUM> is therefore constant within recognized variations which may be due to factors such as manufacturing tolerances of components, temperature variations for any one appliance, and differences in temperature between several different appliances. Additionally, the disclosed example constant input current <NUM> may also include variations that are present due to a dither between discrete levels provided as part of a digital signal. Moreover, the example constant input current <NUM> may include any additional variations that are present in any electrical device that are otherwise understood to provide a constant input current.

Referring to <FIG> with continued reference to <FIG> and <FIG>, during continuing operation (not at startup) the power controller <NUM> senses driver voltage <NUM> through its analog the charge level signal <NUM> and determines a phase <NUM> based upon power control signal <NUM>. At startup the power controller <NUM> tailors the input current to achieve ramp rates as described below, and takes initially as input a startup control signal from the startup controller <NUM> (initially the charge level signal <NUM> will be close to <NUM>, and will ramp up as charging levels increase). The power controller <NUM> regulates a selected phase <NUM> of the driver voltage <NUM> by adjusting charging current <NUM> from the current controller <NUM> through the current control signal <NUM>. Graph <NUM> illustrates sound pulses <NUM> that are provided at period <NUM>. Each sound pulse <NUM> is output for a defined duration <NUM> followed by an interval of no sound <NUM>. The power controller <NUM> regulates voltage <NUM> at a phase <NUM> shown on graphs 56A and 56B to correspond to the sound level phase shown on graph <NUM> at <NUM>.

The drive voltage <NUM> to the transducer driver <NUM> is illustrated in graphs 56A and 56B and shown as <NUM>. When the transducer <NUM> is not generating sound, it does not require energy and the current <NUM> flowing from the NAC <NUM> is stored in the energy store <NUM> (<FIG>). Storage of energy in the energy store <NUM> increases the charge level <NUM> of the energy store <NUM>. When the transducer <NUM> is active and generating sound as shown in graph <NUM>, the sound engine <NUM> receives energy from the input current <NUM> along with the energy stored in the energy store <NUM> when the transducer <NUM> was not sounding. By buffering energy in the energy store <NUM> during intervals <NUM>, the input current <NUM> shown in graph <NUM> is kept constant and creates a small ripple in the energy store charge level voltage <NUM> shown in graph 56A.

The power controller <NUM> is programmable to provide phased regulation of the input voltage <NUM> to the transducer driver <NUM>. The example input voltage <NUM> is phase matched to the acoustic pattern shown in graph <NUM>. In this example, the voltage is regulated to a phase just prior to the generation of sound indicated at <NUM> in graph <NUM>.

The example power control <NUM> is programmable to set sound power level for a specific application. A notification appliance <NUM> may need to operate at a reduced volume to accommodate smaller areas and rooms. The use of a resistor to dissipate energy does not provide an optimal decrease in input power and may therefore waste power. The example power control <NUM> is adjusted to reduce the input voltage <NUM> to provide the reduced sound power. In one disclosed example, the power controller <NUM> is programmable at the time of installation to provide several volume settings by reducing the piezo driver input voltage <NUM>. The volume settings can be implemented during installation to match volume to a specific location of installation. The selection can be with a selector switch or through other known means. The power control <NUM> may also be programmed at the manufacturing and design stage to provide modifications to sound output based on each sound pattern and sound-power combination. In one example, an input voltage <NUM> can be reduced for intermittent sound patterns as compared to the input voltage <NUM> utilized for continuous sound patterns. For example, the fire alert pattern <NUM> may require less sound power as compared to a continuous-high sound pattern.

Referring to <FIG> with continued reference to <FIG> and <FIG>, the notification appliance <NUM> is rated according to current during a running condition and during startup. During startup energy stores are charged to a predefined level prior to generation of a sound. A single fixed ramp rate at a single fixed current for all sound patterns wastes energy for all but the highest sound levels. The example power control <NUM> tailors the input current to provide different voltage ramp rates for each sound pattern. By varying the voltage ramp rates, the startup current can be maintained below the running current to provide improved current ratings. The control of charging the energy store <NUM> during startup is by the startup controller <NUM>, as different from the temporal pattern generator <NUM> which controls the charging of the energy store during running conditions.

The example graph <NUM> illustrates control of the input current <NUM> by the power control <NUM> to tailor the voltage ramp rates <NUM>, <NUM>, <NUM> and <NUM> to a corresponding sound pattern. Graph <NUM> illustrates the running voltage and ramp-rate for different sound patterns. The example ramp-rate is between <NUM> and <NUM> volts/second. In another example, the ramp-rate may be between <NUM> and <NUM> volts/second. Moreover, it is within the contemplation of this disclosure that the ramp-rate maybe between <NUM> and <NUM> volts/second. The voltage indicated at <NUM> corresponds with a continuous sound pattern with a high sound level <NUM>. The voltage indicated at <NUM> corresponds with a continuous sound pattern with a low sound level <NUM>. The voltage indicated at <NUM> corresponds with a fire alert sound pattern at high sound level. The voltage indicated at <NUM> corresponds with a fire alert sound pattern at a low sound level. Continuous sound levels may require a faster start time and therefore the voltage ramp-rates may be higher.

The start-time for the fire alert sound patterns may be lower and therefore the voltage ramp rates for these sound levels are reduced to reduce the corresponding running current rating. In this example, each voltage <NUM>, <NUM>, <NUM> and <NUM> include different ramp rates <NUM>, <NUM>, <NUM> and <NUM> that corresponds to the each individual sound pattern. By tailoring the voltage ramp rate to the power needs of each sound pattern, each of the sounds can be rated at the running current instead of a higher startup current needed for only one sound pattern.

The disclosed example appliance <NUM> includes a power control <NUM> that utilizes less current by controlling and matching the input voltage to the sound pattern. Control of the input voltage relative to the desired acoustic pattern and shunting current to an energy store <NUM> when not generating a sound enables the input current to be lower and quasi-constant to provide an overall decrease in current use by the notification appliance.

Claim 1:
A method of powering a sounder (<NUM>) comprising a sound engine (<NUM>) and an energy store (<NUM>), the method comprising:
providing a constant input current (<NUM>);
regulating an input voltage (<NUM>) of the sound engine (<NUM>) to a phase (<NUM>) corresponding with an acoustic signal generated by the sound engine; and
storing input current in the energy store (<NUM>) responsive to the sound engine not generating a sound output between phases of a sound pattern, wherein a ramp rate of the input voltage to charge the energy store is varied to correspond with the sound pattern; and
wherein the sound engine draws energy from both the constant input current and the energy store when generating the sound output.