Circuit for preventing backflash in power failure

Abstract

The utility model discloses a circuit 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 utility model 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 power supply state of the conventional drive is cut off through the closing of the switch. Therefore, the electric energy stored in the conventional driving power supply is not released in a loop at the power-off moment, and the flashback caused by false triggering at the power-off moment is prevented.

Description

Technical Field

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

[0002] In traditional two-wire detection circuits, the two-wire detection chips used in the market include domestic chips such as QW2886 / QW2889 / WS5921S and ZK4068. These chips all have inherent defects, which means they can only be used in low-power AC drives. Because the power is low, 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 insufficient 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 flicker momentarily. During use, it not only affects the user experience, but also affects the service life of the lamp. Utility Model Content

[0004] The technical problem solved by the utility model is: how to provide a circuit to prevent 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, 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 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 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 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 transistor 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 a two-wire emergency lighting fixture with neutral and live wire identification.

[0013] 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

[0014] Figure 1 This is a logic principle diagram of the latter circuit of the present utility model;

[0015] Figure 2 This is another logical principle diagram of the latter stage circuit of the present utility model;

[0016] Figure 3 This is a schematic diagram of the overall circuit for preventing power-off flashback according to the present invention;

[0017] Figure 4 This is a schematic diagram of the sampling results before the rectifier bridge of the utility model;

[0018] Figure 5 This is a schematic diagram of the sampling results after the rectifier bridge described in the present invention. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions 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 the embodiments. Example 1

[0020] For the two-wire detection chips 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 set 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 bridge's withstand voltage is greater than 1000V, the peak voltage is transmitted from the conventional drive circuit through the negative pole to the input end of the power supply, thereby causing an unnecessary false triggering of the two-wire detection chip circuit, causing the light source part to flicker momentarily.

[0021] To completely solve the above problems, refer to Figure 1-2 As shown in FIG. 1 , this embodiment proposes a circuit for preventing flashback during power failure, which is applied to a two-wire emergency lighting fixture with neutral and live wire identification, including a rectifier bridge module 100, a post-stage circuit 200, a drive circuit 300, and a control circuit 400, which 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, and 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, 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.

[0022] 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 circuit 200 is connected to the output end of the rectifier bridge module 100, and the subsequent circuit 200 and the rectifier bridge module 100 form a loop. At the same time, the input end of the driving circuit 300 is connected to the output end of the subsequent 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 circuit 200. The subsequent circuit 200 is used to supply power for sampling of the driving circuit 300, that is, the driving circuit 300 is controlled by the subsequent circuit 200, and the input signal of the driving circuit 300 is more stable after filtering by the subsequent circuit 200, thereby improving the stability of the circuit.

[0023] Figure 2Different 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 both achieve the prevention of light source flashback in this embodiment.

[0024] In the conventional wiring method, the driving 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 driving 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 driving circuit 300 is placed after the rectifier bridge module 100, and the AL end of the driving circuit 300 is connected to the positive voltage of the rectifier bridge module 100, and the AN end of the driving 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 driving 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 driving circuit 300.

[0025] The control circuit 400 includes a first control switch K1, whose two terminals are connected to the AN terminal of the driver circuit 300 and the negative voltage of the rectifier bridge module 100, respectively, to control the connection and disconnection between the AN terminal and the rectifier bridge module 100. In this embodiment, the first control switch K1 is a relay. When the relay is closed, the normal drive AN is connected to the negative voltage of the rectifier, thereby providing power to the normal drive. Regarding the connection method of the control circuit 400, this embodiment includes methods such as directly connecting the first control switch K1 to the AN terminal, or connecting the second control switch K2 via a transistor control method. The first control switch K1 and the second control switch K2 are independently controlled and do not affect or interfere with each other, but can only be in a single switch control state. In this embodiment, the first control switch K1 and the second control switch K2 are implemented in different ways, and can both use relays, mechanical switches, high-power MOS MOSFETs, or thyristors. Example 2

[0026] Reference Figure 3 To more clearly illustrate the circuit of this embodiment, Figure 3 The diagram shows a schematic diagram of the circuit structure 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, as well as its application to other component circuits in a two-wire emergency lighting fixture with neutral and live wire identification.

[0027] More specifically, the application circuit includes a power supply part, 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 is an existing mature technical means, and those skilled in the art can fully refer to the existing technology to implement it.

[0028] Refer again Figure 3 The 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 charging and discharging control and management of the lamp and belong to the existing technology. Therefore, it should be noted that for the circuit for preventing power-off flashback proposed in this embodiment, its core 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 actual applications, they all belong to the existing very mature existing technologies. As for the modules themselves that make up the above-mentioned circuit, whether it is the specific connection of the various components involved in the circuit diagram, or how to implement control, two-wire detection, etc., technical personnel in this field should be able to fully realize it according to existing technical means. Refer to the implicitly disclosed part, which will not be described in detail here.

[0029] Furthermore, the rectifier bridge module 100 includes a positive terminal V+ and a negative terminal V-. The post-stage circuit 200 includes three parallel branches: a branch comprising a first inductor L1, a branch comprising a second inductor L3, and a branch comprising a first resistor R3. A first capacitor C2 and a second capacitor C3 are provided on the first inductor L1, respectively, at opposite ends of the first inductor L1. The input ends of the three branches converge to form a first node P1, which is located behind and connected to the positive terminal V+. The output ends of the three branches converge to form a second node P2. The three parallel branches form a π-type filter circuit that filters the signal output by the rectifier bridge module 100 and samples and controls the power supply to the driver circuit 300. The AL terminal of the driver circuit 300 is connected to the second node P2, and the AN terminal of the driver circuit 300 is connected to the negative terminal V- of the rectifier bridge module 100 via a third node P3. 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 existing technologies and will not be described in detail here.

[0030] The control circuit 400 is a switching circuit provided between the third node P3 and the AN terminal, and includes 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 using a relay. When it receives a momentary power-off signal, it is disconnected, thereby cutting off the loop between the third node P3 and the AN terminal, thereby preventing the electric energy stored in the drive circuit 300 from triggering the two-line detection chip circuit by the negative electrode, 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, achieving the purpose of powering the conventional drive, and the light source part operates 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 3 Schematically, 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.

[0031] Therefore, the implementation principle of this embodiment is as follows: the post-stage circuit 200 is arranged after the rectifier bridge, and the post-bridge sampling method is adopted to supply power to the conventional drive, and the control circuit 400 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.

[0032] 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 from before the rectifier bridge and after the rectifier bridge for comparison. Figure 4 It shows that when AC100V is input, under the same power conditions, the peak voltage obtained by sampling before the bridge 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

[0033] 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, including the following steps:

[0034] S1: Connect the input end of the subsequent circuit 200 to the positive voltage of the rectifier bridge module 100;

[0035] 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;

[0036] 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;

[0037] S4: The control circuit 400 controls the power supply circuit of the driving circuit 300 by closing or opening the power supply circuit.

[0038] After the above steps are completed, the following control methods are also included:

[0039] Connect the rectifier bridge module 100 to the power supply;

[0040] Under normal power supply conditions, 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 the 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. At this time, the light source part is working normally, that is, the lamp is lighting normally.

[0041] 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 operate and then disconnect, and cuts 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 electrical energy stored in the energy storage element therein cannot be released, thereby preventing flashback caused by false triggering at the moment of power failure.

[0042] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. 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 may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the claims of the present invention.

Claims

1. A circuit for preventing flashback during power failure, 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 AC voltage into positive voltage and negative voltage; The driving circuit includes 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 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 flashback after power failure 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 flashback during power failure 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 flashback after power failure according to claim 4, characterized in that: 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.

6. The circuit for preventing flashback after power failure according to claim 2, characterized in that: The post-stage circuit is a π-type filter circuit, which is used to filter out the interference signal output by the rectifier bridge module.

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

Images