Circuit and method for preventing backflash during power failure

Abstract

The invention discloses a circuit and a method for preventing backflash during power failure. The circuit comprises a rectifier bridge module, a driving circuit and a control circuit which are sequentially connected to form a loop, the rectifier bridge module is used for converting an alternating voltage into a positive voltage and a negative voltage; the AL end is connected with a positive voltage of the rectifier bridge module, and the AN end is connected with a negative voltage of the rectifier bridge module through the control circuit to form a loop; and the control circuit is used for controlling the connection and disconnection of the negative electrode voltage of the rectifier bridge module and the AN end of the driving circuit. The beneficial effects of the invention are that the post-stage circuit is arranged behind the rectifier bridge, the post-bridge sampling mode is adopted to supply power to the conventional drive, the control circuit is arranged on the negative voltage loop of the conventional drive power supply, and the state of the conventional drive power supply is cut off through the closing of the switch, so that the electric energy stored by the conventional drive power supply is not released by the loop at the moment of power failure; flashback caused by false triggering at the moment of power failure is prevented.

Description

Technical Field

[0001] The invention relates to the technical field of flashback of a light source of a lamp at the moment of power failure, and in particular to a circuit and method for preventing flashback at the moment of power failure. Background Art

[0002] In the traditional two-wire detection circuit, the two-wire detection chips used in the market include QW2886 / QW2889 / WS5921S and ZK4068. The above chips have inherent defects, that is, they can only be used in low-power AC drives. Because of the low power, the capacitors and inductors used in front of the bridge are small. Therefore, at the moment of power failure, the capacitors and inductors have no storage capacity and are not enough to trigger the two-wire detection chip circuit. Most of the above are for low-power lighting fixtures.

[0003] However, for high-power lighting fixtures, since the front-stage circuit uses large-capacity capacitors and inductors, at the moment of power failure, these energy storage elements store a large amount of electrical energy and must have a release circuit. Therefore, the two-wire detection chip circuit is invisibly triggered uselessly, causing the light source to flash momentarily, which not only affects the user experience during use, but also affects the service life of the lamp. Summary of the invention

[0004] The technical problem solved by the invention is: how to provide a circuit and a method for preventing flashback during power failure.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a circuit for preventing power-off flashback, characterized in that: it includes a rectifier bridge module, a drive circuit and a control circuit that are connected in sequence to form a loop; the rectifier bridge module is used to convert AC voltage into positive voltage and negative voltage; the drive circuit includes an AL terminal and an AN terminal, the AL terminal is connected to the positive voltage of the rectifier bridge module, the AN terminal is connected to the negative voltage of the rectifier bridge module through the control circuit to form a loop, and the drive circuit is used to drive the device to work normally; the control circuit is used to control the connection and disconnection of the negative pole voltage of the rectifier bridge module and the AN terminal of the drive circuit.

[0006] Preferably, it also includes a post-stage circuit for circuit sampling, holding and controlling power supply; the input end of the post-stage circuit is connected to the positive voltage of the rectifier bridge module, and the output end of the post-stage circuit is connected to the negative voltage of the rectifier bridge module to form a loop.

[0007] Preferably, the AL terminal of the driving circuit is connected to the forward voltage of the rectifier bridge module via the subsequent circuit, and the subsequent circuit is used to supply power for sampling of the driving circuit.

[0008] Preferably, the control circuit comprises a first control switch, and two ends of the first control switch are respectively connected to the AN end of the drive circuit and the negative electrode voltage of the rectifier bridge module.

[0009] Preferably, the first control switch is a relay, a mechanical switch, a high-power MOS or a thyristor, and the control method is direct control or triode control.

[0010] Preferably, the post-stage circuit is a π-type filter circuit, which is used to filter out interference signals output by the rectifier bridge module.

[0011] Preferably, a two-wire detection circuit is further included, and the two-wire detection circuit is arranged at the front end of the rectifier bridge module and directly connected to the power supply.

[0012] Preferably, it is applied to two-wire emergency lighting with zero and live wire identification.

[0013] The present invention also provides the following technical solution: a method for preventing flashback during power failure of a circuit, comprising a circuit for preventing flashback during power failure as described above, and further comprising the following steps: connecting the input end of the subsequent circuit to the positive voltage of the rectifier bridge module; connecting the AL end of the drive circuit to the output end of the subsequent circuit, or directly connecting to the positive voltage of the rectifier bridge module without passing through the AL end; connecting the AN end of the drive circuit to the negative voltage of the rectifier bridge module, and arranging a control circuit between the AN end and the negative voltage of the rectifier bridge module; the closing or opening of the control circuit controls the power supply circuit of the drive circuit.

[0014] Preferably, the following control steps are included: connecting the rectifier bridge module to a power supply; under normal power supply, closing the control circuit, connecting the AN end of the drive circuit to the negative voltage of the rectifier bridge module; after connection, the rectifier bridge module, the subsequent circuit, the drive circuit and the control circuit form a loop, and the subsequent circuit samples and supplies power to the drive circuit normally; at the moment of power failure, the control circuit is disconnected, cutting off the AN end of the drive circuit from the negative voltage of the rectifier bridge module; the drive circuit cannot form a loop, and the electrical energy stored in the energy storage element therein cannot be released.

[0015] The beneficial effects of the present invention are as follows: the post-stage circuit is arranged after the rectifier bridge, and the conventional drive is powered by a post-bridge sampling method, and a control circuit is arranged on the negative pressure circuit of the conventional drive power supply. The conventional drive power supply state is cut off by closing the switch, so that at the moment of power failure, the electric energy stored in the conventional drive power supply has no circuit to release, thereby preventing flashback caused by false triggering at the moment of power failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a logic principle of the subsequent circuit of the present invention; Figure 2 Another logic principle schematic diagram of the subsequent circuit of the present invention; Figure 3 This is a schematic diagram of the overall circuit diagram for preventing power-off flashback according to the present invention; Figure 4 This is a schematic diagram of the sampling results before the rectifier bridge of the present invention; Figure 5 This is a schematic diagram of the sampling results after the rectifier bridge described in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Example 1

[0018] For the two-wire detection chip currently used in the market, for high-power lighting fixtures, the conventional wiring method is to sample in front of the bridge and control the operating status of the conventional drive circuit. The two-wire detection chip and the conventional drive circuit are both arranged in front of the bridge and directly connected to the power supply. The conventional drive circuit is used to drive high-power lamps. The capacitors and inductors used in front of the bridge have a large storage capacity. At the moment of power failure, a large amount of electrical energy stored in the capacitors and inductors in the conventional drive circuit will be released. Since the withstand voltage of the bridge is greater than 1000V, the peak voltage is transmitted from the conventional drive circuit through the negative electrode to the input end of the power supply, thereby causing a useless false triggering of the two-wire detection chip circuit, causing the light source part to flicker momentarily.

[0019] To completely solve the above problems, refer to Figure 1-2 As shown in the figure, this embodiment proposes a circuit for preventing power-off flashback, which is applied to two-wire emergency lamps with zero and live wire identification, including a rectifier bridge module 100, a post-stage circuit 200, a drive circuit 300 and a control circuit 400 that are connected in sequence to form a loop. Specifically, the input end of the rectifier bridge module 100 is connected to the power supply part, which is used to convert the AC voltage input by the power supply part into a positive voltage and a negative voltage. The drive circuit 300 is an AC conventional drive circuit, which adopts an existing conventional drive circuit, for example, it can be a 45W conventional drive circuit, which includes an inductor, a capacitor and a switch circuit, etc., for realizing the control of emergency lighting using a wall switch. Those skilled in the art can refer to the existing technology for implementation, and this part will not be described in detail.

[0020] The post-stage circuit 200 is a π-type filter circuit after the rectifier bridge, which is used for circuit sampling, controlling the power supply of the driving circuit 300, and filtering out the interference signal output by the rectifier bridge module to maintain the stability of the circuit. Figure 1 and Figure 2 There are two different wiring methods. Figure 1 In the figure, the input end of the subsequent stage circuit 200 is connected to the output end of the rectifier bridge module 100, and the subsequent stage circuit 200 and the rectifier bridge module 100 form a loop, and at the same time, the input end of the driving circuit 300 is connected to the output end of the subsequent stage circuit 200, that is, the AL end of the driving circuit 300 is connected to the forward voltage of the rectifier bridge module 100 after passing through the subsequent stage circuit 200, and the subsequent stage circuit 200 is used to supply power to the sampling of the driving circuit 300, that is, the driving circuit 300 is controlled by the subsequent stage circuit 200, and the input signal of the driving circuit 300 is more stable after filtering by the subsequent stage circuit 200, thereby improving the stability of the circuit.

[0021] Figure 2 Different connection methods are given in the figure. The driving circuit 300 is directly connected to the positive voltage of the rectifier bridge module 100, that is, the current signal does not need to pass through the subsequent circuit 200, and the output of the rectifier bridge module 100 directly enters the driving circuit 300. Two different methods can achieve the prevention of light source flashback in this embodiment.

[0022] In the conventional wiring method, the drive circuit 300 is directly located in front of the rectifier bridge module 100 and connected to the power supply part, which can directly drive the lamp to turn on and off, but it also causes the electric energy in the drive circuit 300 to be released to the two-wire detection chip circuit which is also connected to the power supply part at the moment of power failure, causing the light source to flash back. In this embodiment, the drive circuit 300 is placed behind the rectifier bridge module 100, the AL end of the drive circuit 300 is connected to the positive voltage of the rectifier bridge module 100, and the AN end of the drive circuit 300 is connected to the negative voltage of the rectifier bridge module 100, and the control circuit 400 is set on the negative circuit of the drive circuit 300 and the rectifier bridge module 100 to control the connection and disconnection of the negative voltage of the rectifier bridge module 100 and the AN end of the drive circuit 300.

[0023] The control circuit 400 includes a first control switch K1, the two ends of which are respectively connected to the AN end of the drive circuit 300 and the negative voltage of the rectifier bridge module 100, and are used to control the connection and disconnection between the AN end and the rectifier bridge module 100. In this embodiment, the first control switch K1 adopts a relay. When the relay is energized, the conventional drive AN is connected to the rectifier negative electrode to achieve the purpose of supplying power to the conventional drive. As for the connection mode of the control circuit 400, in this embodiment, it includes a mode such as the first control switch K1 directly connected to the AN end, or a mode such as the second control switch K2 connected in a triode control mode. The first control switch K1 and the second control switch K2 are independently controlled from each other, and do not affect or interfere with each other, but can only be in a state of switch control. In this embodiment, the first control switch K1 and the second control switch K2 are different implementation modes, and both can adopt relays, mechanical switches, high-power MOS or thyristors. Example 2

[0024] Reference Figure 3 To more clearly illustrate the circuit of this embodiment, Figure 3 The schematic diagram is a circuit structure schematic diagram for preventing power-off flashback proposed in this embodiment, including a rectifier bridge module 100, a post-stage circuit 200, a drive circuit 300 and a control circuit 400, and its application to other component circuits in a two-wire emergency lighting fixture with zero and live wire identification.

[0025] More specifically, the application circuit includes a power supply portion, including a live AC L and neutral line AC N, rectifier bridge module 100 through the live wire AC L and neutral line AC N is connected to the power supply part and is located at the front end of the rectifier bridge module 100. The two-line detection chip circuit is also connected to the power supply part. Its function is to identify the neutral and live wires of the power supply. In this embodiment, the chip uses CW2889F, and it can also be a two-line detection chip such as QW2886 / QW2889 / WS5921S and ZK4068. The two-line detection chip circuit belongs to the existing mature technical means, and those skilled in the art can fully refer to the existing technology to achieve it.

[0026] Refer again Figure 3The right side of the two-wire detection chip circuit includes the charging control circuit module and the charging circuit of the lamp's charging power supply, which are used for the charging and discharging control and management of the lamp and belong to the prior art. Therefore, it should be noted that the core of the circuit for preventing power-off flashback proposed in this embodiment lies in the structural arrangement between the rectifier bridge module 100, the post-stage circuit 200, the drive circuit 300 and the control circuit 400. As for other two-wire detection chip circuits, charging control circuit modules and charging circuits required in practical applications, they all belong to the existing very mature prior art. As for the modules themselves that constitute the above-mentioned circuit, whether it is the specific connection of the components involved in the circuit diagram, or how to implement the control, two-wire detection, etc., technical personnel in this field should be able to fully realize it according to the existing technical means, and refer to the implicitly disclosed part, which will not be described in detail here.

[0027] Further, the rectifier bridge module 100 includes a positive terminal V+ and a negative terminal V-, and the post-stage circuit 200 includes three parallel branches, which are respectively provided with a branch of a first inductor L1, a branch of a second inductor L3, and a branch of a first resistor R3, and a first capacitor C2 and a second capacitor C3 are respectively provided at both ends of the first inductor L1 on the branch of the first inductor L1, and the input ends of the three branches converge into a first node P1, the first node P1 is provided behind the positive terminal V+ and connected, and the output ends of the three branches converge into a second node P2, and the three parallel branches constitute a π-type filter circuit, which filters the signal output by the rectifier bridge module 100, and samples and controls the power supply to the drive circuit 300. The AL end of the drive circuit 300 is connected by the second node P2, and the AN end of the drive circuit 300 is connected by the third node P3 to the negative terminal V- of the rectifier bridge module 100, and the third node P3 is directly connected to the negative terminal V- of the rectifier bridge module 100. The driving circuit 300 is a conventional AC control circuit, which includes common-mode inductors, capacitors, resistors and other components. It is implemented with reference to the prior art and will not be described in detail here.

[0028] The control circuit 400 is a switch circuit disposed between the third node P3 and the AN terminal, including a first control switch K1 and a diode D4. The first control switch K1 is connected to the negative electrode circuit, and the diode D4 is grounded. At the same time, the first control switch K1 is connected to the charging control circuit below the circuit by a relay, and is disconnected when receiving a signal of instantaneous power failure, thereby realizing the cutting off of the loop between the third node P3 and the AN terminal, so as to prevent the electric energy stored in the drive circuit 300 from being triggered by the negative electrode of the two-line detection chip circuit, thereby causing flashback. Under normal circumstances, the first control switch K1 is energized, and the conventional drive AN is connected to the rectifier negative electrode, so as to achieve the purpose of powering the conventional drive, and the light source part works normally. For another implementation of the control circuit 400, that is, if the second control switch K2 is connected in a triode control manner, Figure 3It is shown that the second control switch K2 and the first control switch K1 are in parallel structure, and the principle is the same as that of the first control switch K1, which will not be described in detail.

[0029] Therefore, the implementation principle of this embodiment is as follows: the post-stage circuit 200 is arranged after the rectifier bridge, and the conventional drive is powered by post-bridge sampling. A control circuit 400 is arranged on the negative pressure circuit of the conventional drive power supply, and the conventional drive power supply state is cut off by closing the switch, so that at the moment of power failure, the electric energy stored in the conventional drive power supply has no circuit to release, thereby preventing flashback caused by false triggering at the moment of power failure.

[0030] Reference Figure 4-5 In this embodiment, the circuit is applied to a two-wire emergency lamp with zero and live wire identification, and samples are taken before and after the rectifier bridge for comparison. Figure 4 It shows that when the AC power is 100V, under the same power condition, the peak voltage obtained by the bridge sampling is 160V. Figure 5 It is shown that when the AC power is 100V, under the same power conditions, the peak voltage obtained by sampling after the bridge is 128V. It is obvious that the voltage sampled from the back of the bridge is much lower than the voltage sampled from the front of the bridge. The circuit proposed in this embodiment is not enough to trigger the two-wire detection circuit. The sampling method from the back of the bridge reduces the voltage by 30V, which can minimize the triggering of the two-wire detection circuit. At the same time, combined with the switch control method, it can completely avoid the flashback caused by false triggering at the moment of power failure. Example 3

[0031] Based on the circuit for preventing flashback after power failure in the above embodiment, this embodiment provides a method for preventing flashback after power failure in a circuit, comprising the following steps: S1: Connect the input end of the subsequent circuit 200 to the positive voltage of the rectifier bridge module 100; S2: Connect the AL terminal of the driving circuit 300 to the output terminal of the subsequent circuit 200, or directly connect it to the positive voltage of the rectifier bridge module 100 without passing through the AL terminal; S3: Connect the AN terminal of the driving circuit 300 to the negative voltage of the rectifier bridge module 100, and set the control circuit 400 between the AN terminal and the negative voltage of the rectifier bridge module 100; S4: The control circuit 400 controls the power supply circuit of the driving circuit 300 by closing or opening.

[0032] After the above steps are completed, the following control methods are also included: Connect the rectifier bridge module 100 to a power source; Under normal power supply, the first control switch K1 in the control circuit 400 is closed, and the AN terminal of the drive circuit 300 is normally connected to the negative voltage of the rectifier bridge module 100; after connection, the rectifier bridge module 100, the subsequent circuit 200, the drive circuit 300 and the control circuit 400 form a loop, and the subsequent circuit 200 normally samples and supplies power to the drive circuit 300. The drive circuit 300 is in a normal operating state, and the light source part works normally at this time, that is, the lamp is illuminated normally; At the moment of power failure, the charging control part in the circuit inputs a signal into the control circuit 400, controls the first control switch K1 to be actuated and then disconnected, thereby cutting off the AN end of the drive circuit 300 from the negative voltage of the rectifier bridge module 100. The drive circuit 300 cannot form a loop, and the electric energy stored in the energy storage element therein cannot be released, thereby preventing flashback caused by false triggering at the moment of power failure.

[0033] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A circuit for preventing power-off flashback, characterized in that: It includes a rectifier bridge module, a drive circuit and a control circuit which are connected in sequence to form a loop; The rectifier bridge module is used to convert the AC voltage into a positive voltage and a negative voltage; The driving circuit comprises an AL terminal and an AN terminal, wherein the AL terminal is connected to the positive voltage of the rectifier bridge module, and the AN terminal is connected to the negative voltage of the rectifier bridge module through the control circuit to form a loop, and the driving circuit is used to drive the device to work normally; The control circuit is used to control the connection and disconnection between the negative electrode voltage of the rectifier bridge module and the AN terminal of the drive circuit.

2. The circuit for preventing power-off flashback according to claim 1, characterized in that: It also includes a post-stage circuit for circuit sampling, holding and controlling power supply; The input end of the subsequent circuit is connected to the positive voltage of the rectifier bridge module, and the output end of the subsequent circuit is connected to the negative voltage of the rectifier bridge module to form a loop.

3. The circuit for preventing power-off flashback according to claim 2, characterized in that: The AL terminal of the driving circuit is connected to the forward voltage of the rectifier bridge module via the subsequent circuit, and the subsequent circuit is used to supply power for sampling of the driving circuit.

4. The circuit for preventing power-off flashback according to any one of claims 1 to 3, characterized in that: The control circuit includes a first control switch, and two ends of the first control switch are respectively connected to the AN end of the drive circuit and the negative electrode voltage of the rectifier bridge module.

5. The circuit for preventing power-off flashback according to claim 4, characterized in that: The first control switch adopts a relay, a mechanical switch, a high-power MOS or a thyristor, and the control method adopts direct control or triode control.

6. The circuit for preventing power-off flashback according to claim 5, characterized in that: The post-stage circuit is a π-type filter circuit, which is used to filter out interference signals output by the rectifier bridge module.

7. The circuit for preventing power-off flashback according to claim 5 or 6, characterized in that: It also includes a two-wire detection circuit, which is arranged at the front end of the rectifier bridge module and directly connected to the power supply.

8. The circuit for preventing power-off flashback according to claim 7, characterized in that: Applicable to two-wire emergency lighting with neutral and live wire identification.

9. A method for preventing circuit power failure flashback, characterized in that: The circuit for preventing power-off flashback as claimed in claims 1 to 8 further comprises the following steps: Connect the input end of the subsequent circuit to the positive voltage of the rectifier bridge module; Connect the AL terminal of the driving circuit to the output terminal of the subsequent circuit, or directly connect it to the positive voltage of the rectifier bridge module without passing through the AL terminal; Connecting the AN terminal of the driving circuit to the negative voltage of the rectifier bridge module, and arranging the control circuit between the AN terminal and the negative voltage of the rectifier bridge module; The closing or opening of the control circuit controls the power supply circuit of the drive circuit.

10. The method for preventing circuit power failure flashback according to claim 9, characterized in that: The control steps include: Connecting the rectifier bridge module to a power source; Under normal power supply, the control circuit is closed, and the AN terminal of the drive circuit is connected to the negative voltage of the rectifier bridge module; After being turned on, the rectifier bridge module, the subsequent circuit, the drive circuit and the control circuit form a loop, and the subsequent circuit samples and supplies power to the drive circuit normally; When the power is turned off, the control circuit is disconnected, and the AN terminal of the drive circuit is cut off from the negative voltage of the rectifier bridge module; The driving circuit cannot form a loop, and the electric energy stored in the energy storage element therein cannot be released.

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