Safety circuit for a gas burner

Abstract

Safety circuit (10) for a gas burner (12) supplied with gas via a gas valve (16), wherein a magnetic coil (18) of the gas valve (16) is supplied with sufficient energy by a thermocouple (20) near the gas burner (12) to keep the gas valve (16) open when a temperature at the thermocouple (20) exceeds a predetermined limit value, wherein the safety circuit (10) has an electronic current flow blocking device (31-42) for blocking the current flow from the thermocouple (20) through the magnetic coil (18) of the gas valve (16) with a controller (34), characterized in that the safety circuit (10) comprises a series circuit comprising the thermocouple (20) and the magnetic coil (18) of the gas valve (16); and the current flow blocking device (31-42) has a series circuit comprising a first switching element (31) and a second switching element (32), wherein the switching states of the first and second switching elements (31, 32) can be controlled and monitored independently of one another by the controller (34), wherein the series circuit comprising the first and second switching elements (31, 32) is connected in parallel to the magnetic coil (18) of the gas valve (16) and the current flow through the magnetic coil (18) of the gas valve (16) can be blocked by closing the two switching elements (31, 32).

Description

[0001] The present invention relates to a safety circuit for a gas burner, in particular a gas burner of a gas cooking area of ​​a gas hob.

[0002] Gas burners are typically supplied with gas via a gas valve from a gas supply line. A thermocouple is also often positioned near the gas burner. This thermocouple generates electrical energy from heat through a thermoelectric effect, making it suitable for temperature measurement. However, it is also possible to use the thermocouple to power a solenoid coil of the gas valve, keeping the gas valve open when the gas burner generates sufficient temperature at the thermocouple, as described, for example, in EP 3 534 069 A1.

[0003] In addition to controlling the gas valve to supply the gas burner with gas, depending on the application, a safety measure is often also necessary to block the gas supply, for example, in the event of a malfunction in the gas burner system. While such a safety measure was usually implemented by mechanical devices in conventional systems, there is an increasing need for electronic safety measures due to, for example, electronic control devices and electronically controlled gas valves. US 6,959,876 B2 discloses an electronic current flow blocking device with a control for blocking the flow of current from a thermocouple to a solenoid coil of a gas valve.

[0004] It is an object of the invention to provide an improved electronic safety measure for a gas burner with a gas valve controlled by a thermocouple.

[0005] This object is achieved by a safety circuit having the features of claim 1. Particularly advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0006] According to the invention, a safety circuit is proposed for a gas burner supplied with gas via a gas valve, wherein a solenoid coil of the gas valve is supplied with sufficient energy by a thermocouple near the gas burner to keep the gas valve open when a temperature at the thermocouple exceeds a predetermined limit value, wherein the safety circuit has an electronic current flow blocking device for blocking the current flow from the thermocouple through the solenoid coil of the gas valve. According to the invention, the safety circuit additionally has a series circuit comprising the thermocouple and the solenoid coil of the gas valve, and the electronic current flow blocking device has a series circuit comprising a first switching element and a second switching element, wherein the switching states of the first and second switching elements can be controlled and monitored independently of one another by the controller.Furthermore, according to the invention, the series circuit comprising the first and second switching elements is connected in parallel to the solenoid coil of the gas valve, so that the current flow through the solenoid coil of the gas valve can be blocked by closing the two switching elements.

[0007] The use of an electronic current flow blocking device enables a simple and reliable safety measure for the gas burner system. By using two switching elements in series, whose switching states can be controlled and monitored independently by the control system, reliable operation of the safety circuit can be ensured and the operation of the current flow blocking device itself can also be reliably monitored, thus increasing the operational safety of the gas burner.

[0008] Within the scope of the invention, the safety circuit can contain one or more thermocouples for supplying power to the solenoid coil of the gas valve and / or a series circuit of two or more switching elements. MOSFETs, preferably low-resistance MOSFETs, are preferably used as the first and second switching elements. The switching elements of the current flow blocking device are preferably identical, but different switching elements can also be used. The control system is designed, for example, as a microcontroller.

[0009] In one embodiment of the invention, the controller of the current flow blocking device has a first control output for controlling the first switching element and a second control output for controlling the second switching element. The use of two separate control outputs for the two switching elements promotes the independent control of the switching elements.

[0010] In one embodiment of the invention, the controller has a voltage level input connected to a connection point between the first and second switching elements, and the controller is configured to detect a voltage level between the first and second switching elements in order to monitor the switching states of the first and second switching elements based on the detected voltage level. Preferably, the controller further comprises an analog-to-digital converter, and the voltage level input of the controller is connected to this analog-to-digital converter. Preferably, the connection point between the first and second switching elements is also coupled to a mains voltage via a resistor.This embodiment of the invention enables, on the one hand, a reliable monitoring of the switching states of the switching elements and, on the other hand, enables this by a relatively uncomplicated method, so that, for example, a simple class B software can be sufficient.

[0011] In one embodiment of the invention, the controller has at least one processor and at least one memory, wherein the memory contains software, preferably of class B, which, when executed by the at least one processor, causes the at least one processor to control and monitor the switching states of the first and second switching elements independently of one another.

[0012] The safety circuit of the invention described above can, in principle, be used in conjunction with any gas burner. The safety circuit according to the invention can be advantageously used in household appliances such as gas stoves or cooktops with one or more gas burners.

[0013] The above and other features and advantages of the invention will become more apparent from the following description of preferred, non-limiting embodiments with reference to the accompanying drawings, which show, mostly schematically: Fig. 1 is a block diagram of an embodiment of a safety circuit which is not the subject of the invention defined in the claims; and Fig. 2 a block diagram of a safety circuit according to an embodiment of the present invention.

[0014] In Fig. 1 illustrates an alternative variant of a safety circuit by way of example, on the basis of which the basic structure and the basic function of the safety circuit according to the invention are explained.

[0015] The safety circuit 10 serves a gas burner 12, which is supplied with gas from a gas supply line 14 via a gas valve 16. The gas valve 16 is designed in the form of an electromagnetic valve having a magnetic coil 18 for controlling a valve element to open and close a passage. A thermocouple 20 is also arranged near the gas burner 12. After the gas burner 12 starts operating, the thermocouple 20 is exposed to a high temperature and accordingly generates electrical energy due to a thermoelectric effect. The magnetic coil 18 of the gas valve 16 is electrically connected to the thermocouple 20, so that the thermocouple 20 supplies the magnetic coil with current, in particular with sufficient current to keep the gas valve 16 open when the temperature generated at the thermocouple 20 by the gas burner 12 is sufficiently high.

[0016] In addition to this series connection of the thermocouple 20 and the solenoid coil 18 of the gas valve 16, the safety circuit 10 also contains a current flow blocking device that blocks the current flow from the thermocouple 20 through the solenoid coil 18 when necessary to close the gas valve 16, for example, as a safety measure due to any malfunction in the gas burner system. The current flow blocking device contains, in particular, a series connection of a first switching element 31 in the form of a preferably low-resistance MOSFET and a second switching element 32, also in the form of a preferably low-resistance MOSFET. In the embodiment of Fig. 1, this series connection of the two switching elements 31, 32 is connected in series to the magnetic coil 18, so that the current flow from the thermocouple 20 through the magnetic coil 18 can be blocked by opening one, preferably both switching elements 31, 32.

[0017] As in Fig. As shown in Figure 1, the current flow blocking device also includes a controller 34, for example, in the form of a microcontroller. The controller 34 contains one or more processors 35 and a memory 36. The memory 36 preferably contains Class B software, which, when executed by the processor 35, triggers the control and monitoring of the switching states of the two switching elements 31, 32. The controller 34 also includes an analog-to-digital converter 37.

[0018] The controller 34 has a first control output 38 connected to the processor 35 and the first switching element 31 to control the first switching element 31 to open or close it, and a second control output 39 connected to the processor 35 and the second switching element 32 to control the second switching element 32 to open or close it. The two switching elements 31, 32 can thus be controlled independently of each other by the controller 34.

[0019] In addition, the controller 34 includes a voltage level input 41, which is connected on the one hand to the analog-to-digital converter 37 and on the other hand to a connection point 40 between the two switching elements 31, 32. The connection point 40 between the two switching elements 31, 32 is also coupled to a mains voltage VCC via a resistor 42. By measuring the voltage level between the two switching elements 31, 32, the controller 34 can thus easily monitor the switching states of the two switching elements 31, 32 independently of one another by generating various switching state combinations of the switching elements 31, 32 via the control outputs 38, 39 and then checking the respective voltage levels.Since any malfunction in the components of the current flow blocking device causes a change in the voltage level, a malfunction of the current flow blocking device can be easily detected, in which case the gas valve can be closed and / or a warning signal can be issued for safety reasons.

[0020] In Fig. 2 shows an example of a safety circuit according to an embodiment of the invention. The same or analogous components are identified by the same reference numerals as in Fig. 1 marked.

[0021] The safety circuit 10 according to the invention differs from that in Fig. 1 shown embodiment by the configuration of the current flow blocking device. As shown in Fig. As illustrated in Figure 2, the series connection of the two switching elements 31, 32 is connected in parallel to the solenoid coil 18 of the gas valve 16, so that the current flow from the thermocouple 20 can be bypassed by closing both switching elements 31, 32. To achieve this short-circuit effect, the two switching elements 31, 32 are preferably designed as low-resistance MOSFETs.

[0022] Otherwise, the structure and functioning of the current flow blocking device and the safety circuit of the embodiment according to the invention correspond to Fig. 2 total those based on Fig. 1 explained variant. REFERENCE NUMBER LIST 10 Safety circuit 12 gas burners 14 Gas supply line 16 Gas valve 18 Solenoid coil 20 thermocouple 31 first switching element 32 second switching element 34 Control 35 processor 36 storage 37 analog-to-digital converters 38 first control output 39 second control output 40 connection point 41 Voltage level input 42 Resistance VCC mains voltage

Claims

[1] Safety circuit (10) for a gas burner (12) supplied with gas via a gas valve (16), wherein a magnetic coil (18) of the gas valve (16) is supplied with sufficient energy by a thermocouple (20) near the gas burner (12) to keep the gas valve (16) open when a temperature at the thermocouple (20) exceeds a predetermined limit value, wherein the safety circuit (10) has an electronic current flow blocking device (31-42) for blocking the current flow from the thermocouple (20) through the magnetic coil (18) of the gas valve (16) with a controller (34), characterized by , that the safety circuit (10) comprises a series circuit comprising the thermocouple (20) and the magnetic coil (18) of the gas valve (16); and the current flow blocking device (31-42) has a series circuit comprising a first switching element (31) and a second switching element (32), wherein the switching states of the first and second switching elements (31, 32) can be controlled and monitored independently of one another by the controller (34), wherein the series circuit comprising the first and second switching elements (31, 32) is connected in parallel to the magnetic coil (18) of the gas valve (16) and the current flow through the magnetic coil (18) of the gas valve (16) can be blocked by closing the two switching elements (31, 32). [2] Safety circuit according to claim 1, wherein the controller (34) has a first control output (38) for controlling the first switching element (31) and a second control output (39) for controlling the second switching element (32). [3] Safety circuit according to one of the preceding claims, wherein the controller (34) has a voltage level input (41) connected to a connection point (40) between the first and the second switching element (31, 32), and the controller (34) is designed to detect a voltage level between the first and the second switching element (31, 32) in order to monitor the switching states of the first and the second switching element (31, 32) based on the detected voltage level. [4] Safety circuit according to claim 3, wherein the controller (34) has an analog-digital converter (37) and the voltage level input (41) of the controller (34) is connected to the analog-digital converter (37). [5] Safety circuit according to claim 3 or 4, wherein the connection point (40) between the first and the second switching element (31, 32) is also coupled to a mains voltage (VCC) via a resistor (42). [6] Safety circuit according to one of the preceding claims, wherein the first and second switching elements (31, 32) are MOSFETs. [7] Safety circuit according to one of the preceding claims, in which the controller (34) has at least one processor (35) and at least one memory (36), wherein the memory (36) contains a class B software which, when executed by the at least one processor (35), causes the at least one processor (35) to control and monitor the switching states of the first and the second switching element (31, 32) independently of one another. [8] Household appliance with a gas burner (12) which is supplied with gas via a gas valve (16), wherein a magnetic coil (18) of the gas valve (16) is supplied with sufficient energy by a thermocouple (20) near the gas burner (12) to keep the gas valve (16) open when a temperature at the thermocouple (20) exceeds a predetermined limit, and a safety circuit (10) according to one of the preceding claims.

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