Discharge switching device for ignition excitation system

Abstract

Discharge switching device (108), which includes: a comparator section (210) configured to compare an input voltage value with a reference voltage value; and a trigger section (212) configured to discharge stored energy when the input voltage value exceeds the reference voltage value, characterized by the fact that the discharge switching device (108) further comprises a temperature compensation diode (220) which is configured to reduce a change in the reference voltage value; the trigger section (212) comprises a trigger device and a discharge device; wherein the trigger device includes a trigger metal oxide semiconductor field effect transistor (MOSFET) (222) and a trigger transformer (216).

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This invention claims priority over provisional patent application SN 61 / 745971, entitled “DISCHARGE SWITCH DEVICE FOR IGNITION EXCITATION SYSTEM”, filed on December 26, 2012. BACKGROUND

[0002] The field of the invention relates generally to discharge switching devices and more specifically to a discharge switching device for an ignition excitation system.

[0003] DE 696 26 728 T2 describes a method and a device for the controllable generation and shaping of sparks in a spark-generating device with a discharge switching device, which has the features of the preamble of claim 1.

[0004] US 5,585,748 A describes a voltage-to-frequency converter with an integrator circuit for integrating an input voltage signal in both positive and negative directions. A first comparator is used to switch the integration direction of the integrator circuit, and a second comparator is used to compare an integration output signal with a threshold signal. A delay circuit delays one of the rising or falling edges of an output signal from the second comparator, which is used as the threshold signal. The second comparator compares the delayed signal with a reference signal that changes with temperature and generates an output signal from the second comparator that switches the integration direction. Diodes are provided to compensate for temperature changes in the reference voltage supplied to the first comparator.

[0005] At least some known ignition exciters contain spark gap switching devices that serve to discharge energy stored in a storage capacitor to an ignition device. Such spark gap devices usually contain radioactive materials, e.g., krypton-85 (Kr85), to achieve a consistent ionization level and uniform operation. Therefore, concerns have recently been raised regarding the use of such radioactive materials in relation to the environment, health, and safety. In fact, no commercially available, economically viable and dimensionally efficient alternative to such spark gap devices exists.

[0006] Furthermore, spark gaps have several disadvantages compared to excitation applications: (1) they are components with a limited lifespan; (2) their voltage varies from spark to spark (usually in the range of + / - 100 volts); and (3) their zero-slip voltage changes over their service life. Each of these factors contributes to the fact that the spark energy level provided by the ignition system to the ignition device is not consistent throughout the system's lifetime. A significant disadvantage of this characteristic is that it makes it difficult to determine replacement intervals for the ignition device, since each ignition device will have experienced different levels of discharge stress depending on the age and condition of the excitation stage spark gap.

[0007] Previously, zero-switching diodes were used to set a trigger voltage to provide gate triggering for thyristor devices. However, these devices exhibit large temperature coefficients and are unable to maintain a stable tank voltage across varying temperatures. SHORT DESCRIPTION

[0008] According to the invention, a discharge switching device is provided, comprising a comparator section, a temperature compensation diode, and a trigger section. The comparator section is configured to compare an input voltage value with a reference voltage value. The temperature compensation diode is configured to reduce any deviation of the reference voltage value. The trigger section is configured to discharge stored energy when the input voltage value exceeds the reference voltage value. The trigger section includes a trigger device and a discharge device, wherein the trigger device comprises a trigger metal-oxide-semiconductor field-effect transistor (MOSFET) and a trigger transformer.

[0009] Particularly preferred embodiments of the invention are specified in the dependent claims. DRAWINGS Fig. Figure 1 shows a diagram of an exemplary AC voltage ignition exciter circuit. Fig. Figure 2 shows an exemplary circuit diagram of the in Fig. 1 discharge switching device shown. DETAILED DESCRIPTION

[0010] The following detailed description illustrates embodiments of the invention by means of examples and is not intended to be limiting. The description enables a person skilled in the art to readily manufacture and use the invention and describes several embodiments, adaptations, modifications, alternatives, and uses of the invention, including the method currently considered best for carrying out the invention. The description is presented in connection with use in one embodiment, i.e., in systems and methods for discharging energy in ignition systems. However, it is considered that this description may be used more generally in ignition systems for industrial, commercial, and domestic applications.

[0011] In the sense used here, the mention of an element or step in the singular, preceded by the indefinite article, should not be understood as excluding the plurality of elements or steps, unless such exclusion is expressly stated. Furthermore, reference to "an embodiment" of the present invention should not be interpreted as excluding the existence of additional embodiments that also embody the listed features.

[0012] Fig. Figure 1 shows a circuit diagram of an exemplary AC ignition excitation system 100. In this embodiment, the system 100 comprises: an electromagnetic interference (EMI) filter and transient protection circuit 102, an input voltage converter 104, a storage capacitor 106 (a "tank / power resonant circuit" capacitor), a discharge switching device 108, and a pulse shaping network 110. The system 100 is connected to a voltage source 112, which provides an input AC voltage. The input voltage converter 104 converts the input voltage from the voltage source 112 into a high-level voltage for storage in the tank capacitor 106. The discharge switching device 108 has "tank positive" and "tank negative" terminals 114 and 116. The discharge switching device 108 supplies energy stored in the tank capacitor 106 from the tank positive terminal 114 to the tank negative terminal 116 and then to the pulse shaper network 110.The pulse shaper network 110 amplifies and shapes a discharge pulse and then outputs the discharge pulse to an ignition device 118.

[0013] Fig. Figure 2 shows an exemplary circuit diagram of the (in Fig. (1 shown) discharge switching device 108. The discharge switching device 108 is a direct replacement element for known spark gap switches. In the exemplary embodiment, the discharge switching device 108 is connected to the (in Fig. The discharge switching device is connected to system 100 (as shown in Figure 1) and the tank positive and tank negative terminals 114 and 116. It is designed to operate in a temperature range between approximately -55°C and +125°C and can operate during short temperature fluctuations up to 150°C.

[0014] As the tank positive voltage in system 100 increases during an initial charging cycle, current flows through a first and a second divider circuit 200 and 202 of the discharge switching device 108. The first divider circuit 200 charges using the tank positive voltage and, upon reaching a threshold, is used to supply current to a positive input of a comparator 204. While the tank positive voltage increases before reaching the threshold, the current at a node 206 is insufficient to operate or "wake up" the comparator 204. During the period before the comparator "wakes up," a metal-oxide-semiconductor field-effect transistor (MOSFET) 208 blocks the tank feedback voltage during the initial charging cycle to protect the comparator 204 until the input voltage is provided to operate it.For example, the MOSFET 208 protects the comparator 204 from damage or from premature triggering of the comparator.

[0015] In this embodiment, the discharge switching device 108 draws a small current (i.e., about 400 µA) during the initial charging cycle to operate a comparator section 210 and a trigger section 212 of the discharge switching device 108. The comparator section 210 is configured to compare an input voltage value with a reference voltage value. The trigger section 212 is configured to discharge stored energy when the input voltage value exceeds the reference voltage value. A Zener diode 214 provides a positive input voltage V cc at the comparator 204. The diode 214 also sets a voltage level that is used to operate the trigger section 212. A reference Zener diode 218 sets the reference voltage value for the comparator 204.

[0016] The comparator section 210 activates when the tank positive voltage reaches a voltage threshold of approximately 1500 volts during the initial charging cycle. When this voltage threshold is reached, diodes 214 and 218 become conductive and the comparator section 210 begins operating.

[0017] Diode 220 is connected in series with reference diode 218 as a temperature compensation diode. The temperature compensation diode 220 is designed to reduce deviations in the reference voltage value. More specifically, the temperature compensation diode 220 is matched to diode 218 to shift the Zener diode voltage change across the temperature range and ensure a stable tank voltage.

[0018] As soon as comparator section 210 becomes operational, the tank-plus feedback voltage at the positive input of comparator 204 is monitored and compared with a negative input signal of comparator 204. If the reference level, output by reference diode 218 at the negative input of comparator 204, is exceeded, an output signal of comparator 204 assumes the logic value HIGH and sends a discharge signal to trigger section 212. Trigger section 212 contains a trigger device and a discharge device. The trigger device includes a trigger MOSFET 222 and a trigger transformer 216. Specifically, comparator 204 supplies current to a trigger MOSFET 222. The energy stored in a capacitor 224 is discharged via a primary winding of the trigger transformer 216. The trigger transformer 216 outputs a gate trigger pulse to a thyristor 226.In this embodiment, the thyristor 226 is a semiconductor-controlled rectifier. The thyristor 226 becomes conductive and discharges energy stored in the (in . Fig. 1 shown) tank capacitor 106 is stored, to which (in Fig. 1 shown) pulse shaper network 110.

[0019] The exemplary methods described here relate to a discharge switching device for an ignition excitation system. More specifically, the embodiments relate to a semiconductor spark gap replacement switching device for use in high-energy and / or high-stress ignition systems. The device can also be used as a quickly replaceable element retrofitted to spark gap devices in field excitation stages. Unlike spark gap devices, this device features temperature compensation to maintain the consistency of a discharge setting point across different temperatures.

[0020] The present description uses examples to describe the invention, including the best mode, and also to enable any person skilled in the art to put the invention into practice, for example, to manufacture and use any devices and systems, and to carry out any related processes. The patentable scope of the invention is defined by the claims and may include other examples that may occur to a person skilled in the art. Such other examples shall fall within the scope of the claims if they have structural elements that do not differ from the literal content of the claims, or if they contain equivalent structural elements with insignificant differences from the literal content of the claims. Reference symbol list: 100 Ignition excitation system 102 Transient protection circuit 104 Input voltage converters 106 Tank condenser 108 Discharge switching device 110 Impulse-former network 112 Voltage source 114 Tank positive terminal 116 Tank negative terminal 118 Ignition device 200 first divider circuit 202 second divider circuit 204 Comparator 206 knots 208 MOSFET 210 Comparator section 212 Trigger section 214 Zener diode 216 Trigger transformer 218 Reference Zener diode 220 temperature compensation diode 220 diode 222 Trigger MOSFET 224 Capacitor 226 Thyristor

Claims

[1] Discharge switching device (108), which includes: a comparator section (210) configured to compare an input voltage value with a reference voltage value; and a trigger section (212) configured to discharge stored energy when the input voltage value exceeds the reference voltage value, characterized by , that the discharge switching device (108) further comprises a temperature compensation diode (220) which is configured to reduce a change in the reference voltage value; the trigger section (212) comprises a trigger device and a discharge device; wherein the trigger device includes a trigger metal oxide semiconductor field effect transistor (MOSFET) (222) and a trigger transformer (216). [2] Discharge switching device according to claim 1, wherein the comparator section (210) is also configured to send a discharge signal to the trigger section (212) when the input voltage value exceeds the reference voltage value. [3] Discharge switching device according to claim 1, wherein the trigger device is configured to perform the following steps: The trigger MOSFET (222) is switched on when the input voltage value exceeds the reference voltage value; and Discharging the energy stored in a first storage capacitor (224) via a primary winding of the trigger transformer (216). [4] Discharge switching device according to claim 3, wherein the trigger transformer (216) is configured to output a trigger pulse signal to the discharge device. [5] Discharge switching device according to claim 1, wherein the discharge device includes a thyristor (226). [6] Discharge switching device according to claim 5, wherein the thyristor (226) is configured to discharge the stored energy when it receives the trigger pulse signal from the trigger transformer (216). [7] Discharge switching device according to claim 1, wherein the discharge switching device (108) is a direct replacement element for existing spark gap devices. [8] Discharge switching device according to claim 1, further comprising a voltage protection device configured to protect the section of the comparator (204) during an initial charging cycle from a feedback voltage from a tank capacitor (106) holding the stored energy.

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