CN107134818B - Notification apparatus and method thereof - Google Patents

Notification apparatus and method thereof Download PDF

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Publication number
CN107134818B
CN107134818B CN201610113338.7A CN201610113338A CN107134818B CN 107134818 B CN107134818 B CN 107134818B CN 201610113338 A CN201610113338 A CN 201610113338A CN 107134818 B CN107134818 B CN 107134818B
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circuit
notification
energy
input
value
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CN107134818A (en
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任瑞亭
沈雪松
谭建
陈立国
向阳
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Siemens Schweiz AG
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B7/00—Signalling systems according to more than one of groups G08B3/00 - G08B6/00; Personal calling systems according to more than one of groups G08B3/00 - G08B6/00
    • G08B7/06—Signalling systems according to more than one of groups G08B3/00 - G08B6/00; Personal calling systems according to more than one of groups G08B3/00 - G08B6/00 using electric transmission, e.g. involving audible and visible signalling through the use of sound and light sources

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
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Abstract

The invention provides a notification device in a fire fighting system and a method thereof. The notification device comprises an input (210), a notification element (240), a boost circuit (320), a tank circuit (230) and a control circuit (350), wherein the control circuit (350) sends a control signal (PWM) to said boost circuit (320), the control signal being indicative of a duty cycle (D) of said boost circuit (320) such that the tank circuit (230) is periodically charged substantially throughout a non-notification period (Toff), wherein said duty cycle (D) is determined in dependence on a value of said input voltage (Vin) and an energy value (Ec) to be stored in the tank circuit. The current limiting function can be realized without a separate current limiting circuit by adopting the notification device.

Description

Notification apparatus and method thereof
Technical Field
The present invention generally relates to the field of Fire alarm (Fire alarm), and more particularly to a Notification apparatus (Notification application) capable of issuing a visual alarm (visual alarm) in a Fire protection system.
Background
FIG. 1 shows a schematic diagram of a typical fire alarm system. As shown in fig. 1, in the fire alarm system, a fire alarm Control device (Control Panel)160 is connected to a plurality of fire detectors 170, notification devices 180, or manual alarms 190, etc. distributed in a building. The fire detector 170, the notification device 180, and the manual alarm 190 may be collectively referred to as a Peripheral device (Peripheral device). These peripheral devices may be connected in parallel to a two-wire network that is connected to a fire alarm Control device (Control Panel)160 and obtains power from the fire alarm Control device 160. In the fire alarm system shown in fig. 1, the notification device 180 may, for example, emit an audible alarm (e.g., using a buzzer or speaker) or may emit a visual alarm (e.g., using a strobe) that is observable by the person.
The strength of the alert signal varies accordingly for different application environments. For example, for a baby room, the intensity of the visual alert and the intensity of the audible alert should be set relatively low, while in a noisy mall a stronger visual or audible alert is required. For example, the notification device preferably needs to provide an alerting light of e.g. at least 4 different light intensity settings, e.g. 15 candela, 30 candela, 75 candela and 110 candela, where candela is an international light intensity unit, denoted cd.
Fig. 2 is a schematic diagram showing a structure of a conventional notification apparatus. As shown in fig. 2, the notification device 200 includes an input 210, a boost circuit 220, a tank circuit 230, and a notification element 240 having a notification function. The input 210 receives power from the line, which powers the entire notification device 200. A boost circuit 220 is coupled to the input 210 and boosts the input voltage at the input, the boosted voltage being higher than the input voltage in order to provide driving energy for the following notification element. The tank circuit 230 is coupled to the boost circuit 220 and is charged by the boosted voltage. The notification element 240 is coupled to the energy storage 230 and issues a notification signal when powered by the energy storage element 230. Here, the booster circuit is, for example, a switching circuit including an inductor. The tank circuit 230 includes, for example, a capacitor. The notification element 240 may be an optical alarm component, an acoustic alarm component, or other similar notification device.
In the notification device shown in fig. 2, the current flowing in sequence from the input 210 to the voltage boost circuit, the tank circuit and the notification element causes a change in the current on the mains line connected to the input 210. To reduce this effect, a current limiting circuit 270 is also provided in the example shown in fig. 2. The current limiting circuit 270 senses the magnitude of the current flowing from the input terminal 210 to the voltage boosting circuit 220 and provides it to a comparing unit 260. The comparison unit 260 compares the sensed current with a threshold value Ref. If the sensed current exceeds the threshold Ref, the comparing unit 260 controls the boosting circuit 220 to stop working, and if not, the boosting circuit 220 continuously stores energy. It can be seen that in the prior art the current contribution of the notification device to the mains line (trunk for short) is limited by a separate current limiting circuit.
Disclosure of Invention
An object of the present invention is to provide a notification device in a fire fighting system, which is capable of limiting the magnitude of current flowing into the notification device without requiring a current limiting circuit. Another object of the present invention is to provide a notification device in a fire fighting system, which is capable of controlling the amount of current drawn from a main line by the notification device according to a change in an input voltage. It is a further object of the present invention to provide a notification device in a fire fighting system that is capable of controlling the amount of current drawn by the notification device from a main line based on the amount of energy consumed at the notification element.
According to one aspect of the present invention, there is provided a notification apparatus for use in a fire fighting system, comprising: an input to receive an energy supply to the notification device; a notification element capable of issuing a notification signal; a boost circuit connected to the input terminal to achieve a boost by storing energy received from the input terminal; a tank circuit charged by the booster circuit and driving the notification element for a notification period; a control circuit which sends a control signal to the boost circuit, the control signal indicating a tank time or duty cycle for each cycle of the boost circuit (tank time and duty cycle for each cycle being equivalent concepts) to cause the tank circuit to charge periodically substantially throughout the non-notification period, wherein the tank time or duty cycle is determined in dependence on the value of the input voltage at the input and the value of the energy to be stored in the tank circuit.
Therefore, the notification device according to the embodiment of the invention can control the duty ratio D or the energy storage time t of the booster circuit when the energy storage element is chargedonTo ensure that the energy storage element is periodically charged throughout the non-notification period Toff. This allows the notification device to minimize the current drawn from the input during energy storage without requiring a separate current limiting circuit and without requiring feedback to control the boost circuit. Therefore, the circuit structure provided by the invention is simpler.
Preferably, the value of the input voltage Vin is a real-time value detected by the control circuit. Obviously, in the embodiment of the present invention, the control circuit may further adjust the duty ratio D or the energy storage time ton of the voltage boosting circuit according to the change of the input voltage Vin, so as to obtain sufficient energy. In this way, the boost circuit can be flexibly adjusted along with the fluctuation of the input voltage, so that the current drawn from the input end is small, and the energy storage circuit obtains enough energy.
More preferably, the energy value is obtained by the control circuit and corresponds to the energy currently consumed by the notification element. Preferably, the notification device further comprises a setting circuit that receives an external input signal and selects an energy value from a plurality of available energy values as the energy currently consumed by the notification element based on the external input signal.
In this embodiment of the present invention, the control circuit may further control the duty ratio D or the energy storage time t of the voltage boost circuitonThe amount of energy drawn from input 210 is adjusted so that only the amount of energy just needed to satisfy the operation of the notification element is drawn. The energy obtained from the input end is further reduced, the purpose of energy saving is achieved, and the size of the current pulled from the input end is reduced.
Preferably, the control circuit determines the energy storage time t of the boosting circuit in each period according to the following formulaonOr its duty cycle D:
Figure GDA0002312468390000031
wherein,
l is an inductance value of the boost circuit;
f is the working frequency of the booster circuit;
η is the conversion efficiency of the boost circuit;
ec is the energy value to be stored in the energy storage circuit;
toff is a non-notification period;
vin is the input voltage;
k is a margin factor.
The energy storage time or the duty ratio of the booster circuit in each period can be calculated by adopting the formula. The capacitance value does not exist in the calculation formula, so the influence caused by the capacitance itself (such as aging or capacitance value fluctuation) can be ignored by adopting the formula. The boost circuit always ensures that the tank circuit obtains sufficient energy Ec to drive the notification element.
Preferably, the notification element is a flashing light element, more preferably an LED. The notification element may also be a sound element.
Preferably, the control signal is a pulse width modulation signal (PWM). Using a PWM signal as a control signal may convey both the operating frequency and the duty cycle. The PWM signal may be generated by a hardware module of the control circuit itself.
According to another aspect of the invention, the invention also proposes a method for a notification device in a fire protection system, wherein the notification device comprises an input, a voltage boost circuit, a tank circuit, a notification element and a control circuit. The method comprises the following steps: obtaining an input voltage at an input end and an energy value to be stored in the energy storage circuit; determining a tank time or duty cycle that the boost circuit should have based on the input voltage and the energy value such that the tank circuit is periodically charged substantially throughout a non-notification period; a control signal is sent to the boost circuit indicating the energy storage time or duty cycle.
Preferably, the input voltage is a real-time value detected by the control circuit. Optionally, the energy value is obtained by the control circuit and corresponds to the energy currently consumed by the notification element.
Preferably, the method further comprises: receiving an external input signal; an energy value is selected from a plurality of available energy values as the energy currently consumed by the notification element in accordance with the external input signal.
Preferably, in the method, the energy storage time or the duty ratio of the boost circuit is determined according to the following formula:
Figure GDA0002312468390000041
wherein,
l is an inductance value of the boost circuit;
f is the working frequency of the booster circuit;
η is the conversion efficiency of the boost circuit;
ec is the energy consumption value to be stored in the energy storage circuit;
toff is a non-notification period;
vin is the input voltage;
k is a margin factor.
The method can control the charging and discharging process of the booster circuit without a feedback loop, and ensures that the current drawn by the notification equipment from the input end reaches the minimum value without a separate current limiting circuit. Furthermore, the invention proposes a method in which the energy delivered by the voltage booster circuit to the storage circuit over the entire non-notification period is exactly the same as the energy consumed at the notification element. This further reduces the amount of energy drawn from the input and also reduces the amount of current drawn from the input. Moreover, by adopting the method provided by the invention, the control circuit can flexibly adjust the duty ratio D or the energy storage time ton of the booster circuit according to the fluctuation of the input voltage Vin so as to obtain enough energy.
The above features, technical features, advantages and modes of realisation of the device will be further explained in the following, in a clearly understandable manner, with reference to the accompanying drawings, illustrating preferred embodiments.
Drawings
The following drawings are only schematic illustrations and explanations of the present invention, and do not limit the scope of the present invention.
Fig. 1 shows a typical fire alarm system.
Fig. 2 shows a circuit schematic of a prior art notification device.
Fig. 3 shows a block diagram of a notification apparatus according to an embodiment of the invention.
Fig. 4 shows a graph of the voltage waveform of the energy storage element in the notification device.
Fig. 5 shows a circuit schematic of a notification device according to a further embodiment of the invention.
Fig. 6A shows an equivalent circuit during the energy storage phase of the boost circuit.
Fig. 6B shows an equivalent circuit in the discharge phase of the booster circuit.
Fig. 7 exemplarily shows an operation flowchart of the control circuit.
Detailed Description
In order to more clearly understand the technical features, objects and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals indicate the same or structurally similar but functionally identical elements.
"exemplary" means "serving as an example, instance, or illustration" herein, and any illustration, embodiment, or steps described as "exemplary" herein should not be construed as a preferred or advantageous alternative.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, for simplicity and clarity of understanding, only one of the components having the same structure or function is schematically illustrated or labeled in some of the drawings.
In this document, "one" means not only "only one" but also a case of "more than one". In addition, in this document, "first", "second", and the like are used only for distinguishing one from another, and do not indicate the degree of importance, the order, and the like thereof.
Fig. 3 exemplarily shows a block diagram of a notification apparatus according to an embodiment of the present invention. In fig. 3, the same components as those in the previous drawings are denoted by the same reference numerals and have the same functions, and are not described again. As shown in fig. 3, the notification device 300 includes an input 210, a boost circuit 320, a tank circuit 230, a notification element 240, and a control circuit 350. Unlike fig. 2, a separate current limiting circuit is not used in fig. 3, but current limiting is achieved by controlling the energy delivered to the tank circuit 230 by the boost circuit 320. In other words, the control circuit 350 controls the boost circuit 320 such that the tank circuit 230 is periodically charged substantially throughout the non-notification period Toff.
The working principle of the notification device shown in fig. 3 will be described below by taking an optical alarm as an example. As shown in fig. 3, storeThe energy circuit 230 generally includes a capacitor capable of storing energy, which is charged during the non-notification period (no alarm) Toff and discharged during the notification period (alarm) Ton to drive the notification element 240 to issue an alarm notification. Fig. 4 shows a waveform of the voltage V across the capacitor in the tank circuit 230 in the circuit of fig. 3. In fig. 4, the duty cycle of the notification element 240 is T, e.g., 1s, which includes a non-notification period Toff (e.g., 900ms) and a notification period Ton (e.g., 100 ms). As shown in fig. 4, in the non-notification period Toff, the voltage V across the capacitor is changed from the residual voltage VC1Is charged to a peak voltage VC2Wherein the residual voltage VC1Should be greater than the forward voltage drop of the notification element (e.g., LED). During the notification period Ton, the capacitor is discharged, and the voltage across it is changed from the peak voltage VC2Down to a residual voltage VC1. Here, in order to ensure that the notification element can obtain enough energy to complete the notification action (e.g. flashing light), it should be ensured that the capacitor is full before the non-notification period Toff expires, with a certain margin, e.g. 1% -5%, being reserved in practical applications.
The energy stored on the tank circuit 230 is preferably greater than or equal to the energy consumed to drive the notification element, which may be expressed as Ec-1/2C (V)C2-VC1)2Where C is a capacitance value. Ec is an energy value that represents the energy that needs to be stored on the tank circuit 230. Preferably, Ec is exactly equal to the energy consumed on the notification element, and therefore Ec may also be referred to as energy consumption value. The energy on the capacitor, viewed from the charging side, comes from the input, whereby Ec can also be expressed as:
Ec＝Vin*I*t， (1)
wherein Vin is the magnitude of the input voltage,
i is the average current value of the current drawn from input 210 during charging of the capacitor,
t is the effective charging time on the capacitor.
Based on equation (1), the inventors of the present invention have pointed out that, assuming that Ec and Vin are substantially constant, the longer the effective charging time t of the capacitor in the tank circuit, the smaller the average current value I. Referring again to fig. 4, it can be further seen that the maximum value of the effective energy storage time t of the capacitor is Toff. When t is Toff, the average current value I reaches a minimum value. For this reason, the inventors of the present invention propose: the control circuit 350 may control the boost circuit 320 such that the tank circuit 230 is periodically charged substantially throughout the non-notification period Toff to limit the current magnitude, as shown in fig. 3.
The boost circuit 320 may itself be considered a switching power supply in fig. 3, for example, the boost circuit 320 may include a switch and an inductor that periodically stores energy and releases energy at a relatively high frequency to achieve a boost of the input voltage. The charging and discharging time of the boost circuit 320 is related to the energy required to be delivered. Assuming that the conversion efficiency of the boost circuit 320 is 100% in an ideal case, the boost circuit 320 needs to obtain the energy Ec from the input terminal 210 as well. In fig. 3, the control circuit 350 sends a control signal, preferably a pulse width modulated signal PWM, to the boost circuit 320. The control signal PWM can indicate the duty ratio D of charging and discharging the boost circuit 320 or the energy storage time t of the boost circuit in each periodon. Of course, the control signal may be other signals sufficient to indicate the energy storage time tonOr a signal of duty ratio D, such as a predetermined level signal, etc. Duty cycle D and energy storage time t in each periodonIn fact, are equivalent concepts. The pulse width modulation signal PWM is selected to transmit the working frequency and the duty ratio of the booster circuit in the pulse signal at the same time. Here, the energy storage time tonIs determined based on the input voltage Vin and the energy value Ec. In an ideal case, the input voltage Vin and the energy value Ec may be assumed to be substantially constant, e.g., both preset default values. With such a circuit as shown in fig. 3, the current limiting function can be achieved without a separate current limiting circuit and without a feedback control (i.e., sampling the output of the voltage boosting circuit) of the voltage boosting circuit, and thus the circuit itself as shown in fig. 3 is simpler.
Preferably, in the circuit shown in fig. 3, the control circuit 350 also samples the voltage Vc across the capacitor in the tank circuit 230. When Vc reaches VC2Thereafter, the control circuit 350 instructs the boost circuit 320 to stop operating so as not to overcharge. Here, Vc is not used as feedback to control the duty cycle of the boost circuit 320.
In practical applications, the input voltage Vin is not usually a constant value, but fluctuates between 16-32V, for example. To this end, the control circuit 350 may preferably also detect a real-time value of the present input voltage Vin at the input 210 in real time. Furthermore, the control circuit 350 can determine the energy storage time t of the voltage boost circuit 320 according to a predetermined energy value Ec and the detected input voltage Vinon. In this way, the boost circuit 320 can transfer appropriate energy to the tank circuit 230 even if the input voltage Vin fluctuates due to external causes. For example, assuming that the non-notification period Toff is 900ms and the duty cycle of the boost circuit 320 is 50kHz, the control circuit 350 may update the value of the input voltage Vin every 5-15 ms and update the energy storage time tonOr duty cycle D.
More preferably, the energy required to be stored by the tank circuit 230 is exactly equal to the energy consumed by the notification element 240, i.e. Ec is the energy consumption value actually required to be consumed. Moreover, Ec also varies depending on the alarm level. As described above, in different application scenarios, the alarm levels of the notification elements are different, and the energy consumption of the corresponding notification elements is also different. For example, for a noisy store, the flash intensity of the visual notification device is set at 110 candela, whereas in a baby room the flash intensity is only at 30 candela. In one embodiment of the present invention, the control circuit 350 in the notification device further obtains a current setting or a currently used Ec, and determines the duty ratio D or the energy storage time t of the voltage boost circuit 320 according to the current setting Ec and the input voltage Vinon。
Optionally, the notification apparatus 300 further comprises a setting circuit 380, which receives an external Input signal Input and selects a currently set energy value Ec from a plurality of available energy values according to the external Input signal Input. The control circuit 350 further determines the control signal PWM according to the currently set energy value Ec and the input voltage Vin. Here, the input voltage Vin may be a preset value or a real-time sensing value of the control circuit 350. For an addressable notification device, the setting circuit 380 is connected to the line, and the Input signal Input may be the alarm level of the notification device 300 obtained from the line, which corresponds to a certain energy value Ec. For non-addressable notification devices, the setting circuit 380 may be a dial switch on the notification device 300, through which an operator sets the alarm level of the notification device 300, i.e., the energy value Ec.
Fig. 5 exemplarily shows a specific circuit of the notification apparatus. As shown in FIG. 5, the input terminals I +, I-obtain the input voltage Vin from the line. The booster circuit 520 includes an inductor L and a switching element S. The inductance L has one end connected to the positive input terminal I + and the other end connected to one end of the switching element S. The other terminal of the switching element S is connected to the negative input terminal I-. The switching element S is turned on or off under the control of the control signal PWM from the control circuit 550, thereby controlling the energy storage time ton of the voltage boost circuit 520. The tank circuit 530 includes a diode D in series with an inductor L and a capacitor C. One end of the capacitor C is connected to the cathode of the diode D, and the other end is connected to the negative input end I-. The notification element 540 may be considered a load R, illustratively shown as a Light Emitting Diode (LED). In fig. 5, the switching element S is periodically turned on and off under the control of the control circuit 550 to realize the charging and discharging of the inductor L. Assume that the operating frequency of the switching element S is f. The time when the switching element S is closed is the energy storage time t of the inductor LonThe turn-off time of the switching element S is the release time t of the electric energy on the inductor L to the capacitoroff. Duty ratio D of operation of switching element S is ton*f。
Fig. 6A and 6B show the circuit shown in fig. 5 in two operating states, switching element S on and off, respectively. As shown in fig. 6A, the switching element S is closed (energy storage time t)on) The following tank circuit 530 and notification element 540 are shorted. At this time, the inductor L stores energy, and the potential on the inductor L is shown as "+, -". As shown in fig. 6B, the switching element S is turned off (release time t)off) The electric energy stored in the inductor L is transmitted to the subsequent tank circuit 530 and the load R. At this time, the potential across the inductor L is shown as "+, -" in FIG. 6B. This is a cycle in this way and then the process is repeated periodically, for example at a frequency of 50 kHz. Thereby, the switching element S is turned on and offThe resultant alternating current, the inductor L, due to its ability to block the current, can boost the input voltage Vin to a higher value in order to drive the load R.
As mentioned above, the switching element S is controlled by the PWM signal from the control circuit 550, and its duty ratio D or tonIs determined based on the input voltages Vin and Ec. In particular, within each ton, the energy E stored on the inductance LLCan be expressed as:
Figure GDA0002312468390000081
wherein L is the inductance value, ILIs the peak current flowing through the inductor.
At the end of ton, ILCan be expressed as:
Figure GDA0002312468390000082
where Vin is the input voltage value.
At toffIn this case, the boost circuit 520 delivers energy to the capacitor C in the tank circuit 530. the conversion efficiency η of the boost circuit is taken into accountoffThe energy internally converted to the capacitance C may be denoted as Ec η EL. The number of charging and discharging times of the boost circuit 520 is f × Toff during the whole non-notification period Toff, and accordingly the total energy transferred to the capacitor C can be represented as Etotal＝f*Toff*η*EL。EtotalPreferably exactly equal to the energy Ec desired to be stored on the capacitor C. Thus, the method can obtain the product,
Figure GDA0002312468390000083
t can be further calculated based on the formula (2)on：
Figure GDA0002312468390000084
In the practical application of the method, the air conditioner,
Figure GDA0002312468390000085
where k may be a margin factor, which may be set empirically.
Accordingly, the duty cycle of the PWM control signal can then be expressed as:
d ═ f × k × ton, where k may be a margin factor, which may be set empirically, and the margin factor k may be selected to be a suitable value, for example, between 0.75 and 1.
Thus, according to the formula (3), the control circuit can calculate the PWM control signal for controlling the voltage boosting circuit 520 according to the change of the input voltage Vin and the change of the energy to be stored in the capacitor.
Fig. 7 schematically illustrates an operational flow 700 of the control circuit 550. As shown in fig. 7, in step S710, the control circuit obtains the input voltage Vin at the input end 210 and the energy value Ec to be stored in the tank circuit 230. The input voltage Vin and the energy Ec may be preset default values. Alternatively, the input voltage Vin and the energy value Ec may also be variable values. For example, optionally, in step S702, the control circuit may detect the actual input voltage value at the input 210 in real time, for example, updating the input voltage Vin every 5 milliseconds. As another example, the energy value Ec may alternatively be a value obtained by the control circuit and corresponding to the current notification element consumed energy. For example, optionally, in step S701, an external Input signal Input is received. In step S703, one energy value Ec is selected from a plurality of available energy values according to the external Input signal Input, as the energy currently consumed by the notification element. In particular, assume that the notification device has 4 different alert levels. The external input signal indicates the alarm level of the current notification device, and then the corresponding energy value is selected according to the alarm level.
Further, in step S720, the energy storage time t that the boost circuit should have is determined based on the input voltage Vin and the energy value EconOr duty cycle D, such that the tank circuit 230 is periodically charged substantially throughout the non-notification period Toff. Here, step S720This can be done by calculation according to the aforementioned formula 3, or by looking up a table. For example, a corresponding table is stored in advance, and the energy storage time and the duty ratio corresponding to different input voltages and energy values are listed in the corresponding table. After Vin and Ec are obtained, the current energy storage time and duty ratio are determined by looking up this correspondence table.
Finally, a control signal, e.g., a pulse width modulation signal PWM, is sent to the boost circuit at step S730, indicating the determined energy storage time and duty cycle.
Next, a case where an LED is used as a flash light element will be described as an example. Assuming that the flash light needs to reach a light intensity of 110 candela, 1.0 joule of energy needs to be consumed on the LED. Further assume that: the inductance L in the booster circuit is 330 muH, the working frequency of the booster circuit is 50kHz, and the conversion efficiency of the booster circuit is 70%. If the input voltage Vin is a fixed value, i.e. Vin is 24V, the capacitor C is 1000 μ F, i.e. the charging time Tc is 1000ms, then the energy storage time t of the boost circuit can be calculated according to the formula (3)on5.72 μ S. If it is assumed that the flash light only needs to reach a light intensity of 30 candela, and energy of, for example, 0.4 joule needs to be consumed on the LED, the energy storage time t of the booster circuit in the circuit of the above parameterson＝3.74μS。
Similarly, when the input voltage Vin fluctuates around 24V, the control circuit may also determine the energy storage time ton of the corresponding boost circuit according to the detected actual Vin. For example, when Vin is sensed to be 22V, the energy storage time of the boost circuit is t for the light intensity requirement of 110 candelaon6.24 μ S. When Vin is detected to be 26V, the energy storage time of the booster circuit is t for the light intensity requirement of 110 candelaon＝5.28μS。
Therefore, the notification device according to the embodiment of the invention controls the duty ratio D or the energy storage time t of the boost circuit when the energy storage element is chargedonTo ensure that the energy storage element is periodically charged throughout the non-notification period Toff. This allows the notification device to minimize the current drawn from the input during energy storage without the need for a separate current limiting circuit. Further, it is possible to prevent the occurrence of,in the embodiment of the invention, the control circuit can also control the duty ratio D or the energy storage time t of the booster circuitonThe amount of energy drawn from input 210 is adjusted so that only the amount of energy just needed to satisfy the operation of the notification element is drawn. This further reduces the amount of energy drawn from the input and also reduces the amount of current drawn from the input. Furthermore, in the embodiment of the present invention, the control circuit may further adjust the duty ratio D or the energy storage time ton of the voltage boosting circuit according to the change of the input voltage Vin, so as to obtain sufficient energy. In this way, the boost circuit can be flexibly adjusted with the fluctuation of the input voltage to ensure that the current drawn from the input end is small.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications such as combinations, divisions or repetitions of features, which do not depart from the technical spirit of the present invention, should be included in the scope of the present invention.

Claims (12)

1. A notification device for use in a fire protection system, comprising:
an input (210) receiving a power supply to the notification device;
a notification element (240) capable of issuing a notification signal;
a boost circuit (320) coupled to said input (210) to boost by storing energy received from said input (210);
a tank circuit (230) charged by the boost circuit (320) and driving the notification element (240) for a notification period (Ton);
a control circuit (350) which sends a control signal to said boost circuit (320) indicating a duty cycle (D) of said boost circuit (320) to cause the tank circuit (230) to be periodically charged throughout a non-notification period (Toff), wherein said duty cycle (D) is determined in dependence on the value of the input voltage (Vin) at said input (210) and the value of the energy (Ec) to be stored in the tank circuit.
2. The notification device according to claim 1, wherein the value of the input voltage (Vin) is a real-time value detected by the control circuit (350).
3. The notification device of claim 1, wherein the energy value (Ec) is obtained by the control circuit (350) and corresponds to an energy currently consumed by the notification element (240).
4. The notification device according to claim 3, further comprising a setting circuit (380) receiving an external Input signal (Input) and selecting an energy value (Ec) from a plurality of available energy values as the energy currently consumed by said notification element in dependence on said external Input signal (Input).
5. The notification apparatus according to any of claims 1-4, wherein the control circuit (350, 550) determines the duty cycle of the boost circuit (320,520) according to the following formula:
Figure FDA0002312468380000011
D＝f*ton
wherein,
l is an inductance value of the boost circuit (320);
f is the operating frequency of the boost circuit (320);
η is the conversion efficiency of the boost circuit (320);
ec is the energy value to be stored in the tank circuit (230);
toff is a non-notification period;
vin is the input voltage;
k is a margin factor;
and D is the duty cycle.
6. The notification device according to any of claims 1-4, wherein the notification element (240) is an LED element, or a sound element.
7. The notification device according to any of claims 1-4, wherein said control signal is a pulse width modulated signal.
8. A method for a notification device in a fire protection system, wherein the notification device includes an input (210), a boost circuit (320), a tank circuit (230), a notification element (240), and a control circuit (350), the method comprising:
obtaining an input voltage (Vin) at an input terminal (210) and an energy value (Ec) to be stored in the tank circuit (230);
determining a duty cycle (D) that the voltage boost circuit (320) should have based on the input voltage (Vin) and the energy value (Ec) such that the tank circuit (230) is periodically charged throughout a non-notification period (Toff);
-sending a control signal to said boost circuit (320) indicating said duty cycle (D).
9. The method of claim 8, wherein the input voltage (Vin) is a real-time value detected by a control circuit (350).
10. The method of claim 8, wherein the energy value (Ec) is obtained by the control circuit (350) and corresponds to an energy currently consumed by the notification element (240).
11. The method of claim 10, further comprising:
receiving an external Input signal (Input);
an energy value (Ec) is selected from a plurality of available energy values as the energy currently consumed by the notification element in dependence on the external Input signal (Input).
12. The method according to any of claims 8-11, wherein the duty cycle (D) of the boost circuit (320) is determined according to the following formula:
Figure FDA0002312468380000021
D＝f*ton
wherein,
l is an inductance value of the boost circuit (320);
f is the operating frequency of the boost circuit (320);
η is the conversion efficiency of the boost circuit (320);
ec is the energy consumption value to be stored in the tank circuit (230);
toff is a non-notification period;
vin is the input voltage;
k is a margin factor;
and D is the duty cycle.
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CN108312962A (en) * 2018-01-16 2018-07-24 安徽航途智能科技有限公司 A kind of automotive natural gas leakage monitoring device
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