A control circuit for a digital pulse igniter

Abstract

The invention discloses a control circuit of a digital pulse igniter, belonging to the technical field of igniters, wherein an ignition module comprises an energy storage capacitor and a high-voltage package; a feedback input terminal of a driving control module is electrically connected to the ignition module, and the driving control module is used to adjust the duty cycle of a PWM signal in real time according to the actual voltage of the energy storage capacitor; a PWM signal output terminal of the driving control module is electrically connected to a control terminal of a boost module, and the boost module is electrically connected to the energy storage capacitor, and the driving control module is also used to control the boost module to charge the energy storage capacitor through a PWM signal; a TRI signal output terminal of the driving control module is electrically connected to a control terminal of a trigger discharge module, and the trigger discharge module is electrically connected to the energy storage capacitor, and the driving control module is also used to control the trigger discharge module to discharge the energy storage capacitor through a TRI signal. The invention solves the problems of low ignition power, inaccuracy, and inability to arbitrarily adjust the charging target voltage of the energy storage capacitor in the existing pulse igniter.

Description

Technical Field

[0001] The invention relates to the technical field of igniters, in particular to a control circuit of a digital pulse igniter. Background Art

[0002] At present, the igniters used in household gas stoves and gas water heaters are basically electronic, based on the pulse principle, and use analog control circuits. The analog control circuit is usually composed of a self-excited oscillation module, a trigger module, and an ignition module. Take the common gas water heater igniter circuit as an example, Figure 1 As shown, the self-excited oscillation module includes a diode D, transistors Q1, Q2, a resistor R, and a transformer T1. The core component of the trigger module is a trigger tube or a thyristor. The ignition module includes an energy storage capacitor C and a high-voltage package T2. When the transistor Q2 is turned on, the self-excited oscillation module is powered on, the secondary winding of the transformer T1 will output an oscillation waveform, and the energy storage capacitor C will be charged through the diode D during the positive half-wave stage of the oscillation waveform. Figure 1 As shown, the direction of arrow 100 is the current direction when the self-excited oscillation module charges the energy storage capacitor C. When the energy storage capacitor C is charged to a certain voltage value that meets the trigger condition of the trigger module, the trigger module is turned on and the energy storage capacitor C is discharged instantly. Figure 1 As shown, the direction of arrow 200 is the current direction when the energy storage capacitor C discharges to the primary winding of the high-voltage package T2. While discharging, the secondary winding of the high-voltage package T2 will induce a high voltage oscillating waveform, which will then break through the air and form an arc.

[0003] Household pulse igniters generally use DC power supply, with an input voltage range of 2.1-5V and a trigger voltage range of 150-200V. According to the formula P=C*U*U*f / 2, where C is the capacitance of the energy storage capacitor, U is the charging target voltage of the energy storage capacitor (i.e., the trigger voltage), and f is the discharge frequency, the ignition power of household pulse igniters is generally lower than 0.3W. In addition, household pulse igniters use analog control circuits, and the parameters of their electronic components are fixed, so the ignition power of the igniter cannot be changed at will. If the ignition power needs to be increased, it will affect the entire system, which is equivalent to a redesign. In addition, due to the error in the trigger voltage of the trigger module of the igniter, this will affect the accuracy of its ignition power and ultimately affect the performance of the igniter (including output high voltage, discharge frequency, discharge energy, etc.). During mass production, if the manufacturer checks the performance parameters of each igniter, this will involve a lot of man-hours, which will increase costs and reduce production efficiency; if the manufacturer does not check the performance parameters of each igniter, it may affect the user experience of some users, such as difficulty in igniting. Summary of the invention

[0004] In view of the above defects, the purpose of the present invention is to provide a control circuit for a digital pulse igniter, which solves the problems of low ignition power and inaccuracy of the existing pulse igniter and the inability to arbitrarily adjust the charging target voltage of the energy storage capacitor.

[0005] To achieve this purpose, the present invention adopts the following technical solutions: a control circuit of a digital pulse igniter, including a drive control module, a boost module, an ignition module, a voltage acquisition module and a trigger discharge module;

[0006] The ignition module includes an energy storage capacitor and a high-voltage package, the energy storage capacitor is electrically connected to the primary coil of the high-voltage package, and the secondary coil of the high-voltage package is electrically connected to the ignition needle;

[0007] The feedback input terminal of the drive control module is electrically connected to the ignition module through the voltage acquisition module, and the drive control module is used to adjust the duty cycle of the PWM signal in real time according to the actual voltage of the energy storage capacitor;

[0008] The PWM signal output end of the drive control module is electrically connected to the control end of the boost module, the boost module is electrically connected to the energy storage capacitor, and the drive control module is further used to control the boost module to charge the energy storage capacitor through the PWM signal;

[0009] The TRI signal output end of the drive control module is electrically connected to the control end of the trigger discharge module, and the trigger discharge module is electrically connected to the energy storage capacitor. The drive control module is also used to control the trigger discharge module to discharge the energy storage capacitor through the TRI signal.

[0010] It is worth noting that the boost module includes a power inductor, and the power inductor is electrically connected to the energy storage capacitor through a rectifier diode;

[0011] The boost module is used to enable the power inductor to store energy when the PWM signal output by the drive control module is at a high level; the boost module is also used to enable the power inductor to release energy when the PWM signal output by the drive control module is at a low level, thereby charging the energy storage capacitor.

[0012] Specifically, the driving control module is used to control the boost module to operate in a discontinuous conduction mode through the PWM signal.

[0013] Preferably, it further comprises a voltage acquisition module, the input end of the voltage acquisition module is electrically connected to the energy storage capacitor, and the output end of the voltage acquisition module is electrically connected to the VOL signal input end of the drive control module;

[0014] The voltage acquisition module is used to collect the voltage of the energy storage capacitor and transmit it to the drive control module through the VOL signal input terminal;

[0015] The drive control module is also used to perform analog-to-digital conversion on the voltage of the energy storage capacitor in real time.

[0016] It is worth noting that a power supply module is also included, the input end of the power supply module is electrically connected to the power supply, the output end of the power supply module is electrically connected to the power inductor, and the power supply module is used to supply power to the boost module.

[0017] Optionally, the control end of the power supply module is electrically connected to the PWR signal output end of the drive control module;

[0018] The drive control module is also used to control the power supply module to stop supplying power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor exceeds a preset charging target voltage; and is also used to control the power supply module to supply power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor does not exceed a preset charging target voltage.

[0019] Specifically, it also includes an overcurrent detection module, the input end of the overcurrent detection module is electrically connected to the power supply, the output end of the overcurrent detection module is electrically connected to the input end of the power supply module, and the control end of the overcurrent detection module is electrically connected to the TST signal input end of the drive control module;

[0020] The overcurrent detection module is used to input a TST effective level to the TST signal input terminal of the drive control module when the power supply circuit has an overcurrent;

[0021] The drive control module is used to control the power supply module to stop supplying power to the boost module through the PWR signal output terminal when the voltage of the energy storage capacitor is lower than a preset lower limit threshold and / or when the TST effective level is received.

[0022] Preferably, it further comprises an automatic power-off module, the input end of the automatic power-off module is electrically connected to the control end of the overcurrent detection module, and the output end of the automatic power-off module is electrically connected to the control end of the power supply module;

[0023] The automatic power-off module is used to output a power-off signal to the control end of the power supply module when receiving the TST effective level;

[0024] The power supply module is used to stop supplying power to the boost module after receiving the power-off signal.

[0025] It is worth noting that it also includes a buck-stabilizing module, the input end of the buck-stabilizing module is electrically connected to the power supply, the output end of the buck-stabilizing module is electrically connected to the power supply input end of the drive control module, and the buck-stabilizing module is used to step down the voltage of the power supply to power the drive control module.

[0026] Optionally, the drive control module is a microcontroller MCU, the drive control module uses a system clock with a frequency of 8 MHz, and the PWM signal is an 8-bit PWM signal.

[0027] One of the above technical solutions has the following beneficial effects:

[0028] 1. In the control circuit of the digital pulse igniter, a digital circuit is formed by the drive control module, the boost module, the ignition module and the trigger discharge module. By controlling the drive control module to control the boost module and the trigger discharge module, the energy storage capacitor of the ignition module can be quickly charged, and the charging target voltage and the charge and discharge cycle of the energy storage capacitor can be adjusted at will. The ignition power can be changed by only changing the parameters in the preset program of the drive control module, so that the control circuit of the digital pulse igniter can be applied to various equipment and devices that require ignition function, and has wide adaptability.

[0029] 2. In the control circuit of the digital pulse igniter, the drive control module can realize high-precision control of the charging target voltage, and the drive control module can also realize high-precision control of the charge and discharge cycle, thereby realizing high-precision control of the ignition power. In batch production, there is no need to modify the parameters of the electronic components according to the factory inspection standards, which greatly improves the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is an analog pulse igniter circuit of the prior art;

[0031] Figure 2 A control circuit of a digital pulse igniter according to an embodiment of the present invention;

[0032] Figure 3 It is a control signal timing diagram of a control circuit of a digital pulse igniter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0034] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] The disclosure below provides many different embodiments or examples for realizing different structures of embodiments of the present invention. In order to simplify the disclosure of embodiments of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the present invention. In addition, embodiments of the present invention may repeat reference numerals and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0036] like Figure 2 and 3As shown, a control circuit of a digital pulse igniter includes a drive control module, a boost module, an ignition module, a voltage acquisition module and a trigger discharge module; the ignition module includes an energy storage capacitor and a high-voltage package, the energy storage capacitor is electrically connected to the primary coil of the high-voltage package, and the secondary coil of the high-voltage package is electrically connected to the ignition needle; specifically, the high-voltage package is a step-up transformer for generating a high voltage of more than 12kV, and the energy storage capacitor is preferably a CBB energy storage capacitor. The feedback input end of the drive control module is electrically connected to the ignition module through the voltage acquisition module, and the drive control module is used to adjust the duty cycle of the PWM signal in real time according to the actual voltage of the energy storage capacitor; specifically, the frequency of the PWM signal is fixed, that is, the period is fixed. According to the volt-second formula V1*T1=V2*T2, V1 is the voltage difference between the two ends of the inductor during the energy storage period of the power inductor, and its value is equivalent to the input voltage under the ideal circuit model, T1 is the duration of the high level of the PWM signal, and the ratio of T1 to the PWM period is the duty cycle of the PWM signal, V2 is the voltage difference between the two ends of the inductor during the energy release period of the energy storage capacitor, and its value is equivalent to the difference between the voltage value of the energy storage capacitor and the input voltage under the ideal circuit model, and T2 is the duration of the energy release of the energy storage capacitor. Because the input voltage is fixed, that is, V1 is unchanged, as the voltage of the energy storage capacitor increases, V2 will increase. If the duty cycle of the PWM signal remains unchanged, that is, T1 is unchanged, T2 will decrease. In order to increase the size of the charging current to speed up the charging speed, it is necessary to make full use of the entire PWM signal cycle, increase T2 by increasing T1, so that the sum of T1 plus T2 always tends to be equal to the period value of the PWM signal, so the duty cycle of the PWM signal will increase with the increase of the energy storage capacitor voltage V2. The PWM signal output end of the drive control module is electrically connected to the control end of the boost module, the boost module is electrically connected to the energy storage capacitor, and the drive control module is also used to control the boost module to charge the energy storage capacitor through the PWM signal; the TRI signal output end of the drive control module is electrically connected to the control end of the trigger discharge module, the trigger discharge module is electrically connected to the energy storage capacitor, and the drive control module is also used to control the trigger discharge module to discharge the energy storage capacitor through the TRI signal. Specifically, the boost module is a Boost type boost circuit.

[0037] In the control circuit of the digital pulse igniter, the drive control module, the boost module, the ignition module and the trigger discharge module constitute a digital circuit. By controlling the drive control module to control the boost module and the trigger discharge module, the energy storage capacitor of the ignition module can be quickly charged, and the charging target voltage and the charge and discharge cycle of the energy storage capacitor can be adjusted at will, so that the control circuit of the digital pulse igniter can be applied to various equipment and devices that require ignition functions, and has wide adaptability. In addition, the drive control module can achieve high-precision control of the charging target voltage through its internal analog-to-digital converter, and the drive control module can achieve high-precision charge and discharge cycle control through its internal timer, thereby achieving high-precision ignition power control. There is no need to modify the parameters of electronic components according to the factory inspection standards during mass production, which greatly improves production efficiency.

[0038] Compared with the analog scheme of the traditional household pulse igniter, the embodiment of the present invention can adjust the charging target voltage (that is, the trigger voltage value) of the energy storage capacitor at will by adjusting the drive control module, thereby changing the ignition power, and has wider adaptability. In addition, the accuracy of the charging target voltage can reach the level of 1%, so that the accuracy of the ignition power reaches the level of 5%, and the accuracy of the ignition power is higher than that of the traditional igniter using analog circuits. For example, in the embodiment of the present invention, a drive control module with a 10-bit or 12-bit analog-to-digital converter ADC is selected, and it is only necessary to ensure that the high 7 bits of the analog-to-digital conversion result are accurate. Assuming that the resistor voltage divider ratio of the voltage acquisition module is 45, and the drive control module is powered by 5V, the input voltage range of the port for analog-to-digital conversion of the drive control module is up to 5V, and the error is less than 1LSB, and 1LSB (least significant bit) represents 45*5 / (2^7)=1.76V. For a trigger discharge voltage of 200V, 1.76V is equivalent to 0.88%, so the control accuracy of the charging target voltage by the drive control module can reach the level of 1%. When a 12-bit analog-to-digital converter ADC is actually used, the number of accurate bits is larger than 7 bits, and the accuracy can be even higher. However, for an igniter using an analog circuit, even if an imported trigger tube is used as the core component of the trigger module, the error of its trigger voltage is ±5%, which is much larger than the error of the present invention. In addition, in the embodiment of the present invention, the control of the charge and discharge cycle by the drive control module mainly depends on the accuracy of its system clock. If an external crystal oscillator solution is used, its error can be regarded as 0; if an internal oscillator solution is used, it can be achieved at room temperature. ±2%. For an igniter using an analog circuit, its discharge frequency is related to both the input power and the output power. Figure 1The error is very large, and being able to achieve ±10% is already outstanding. Assuming that the capacitance error of the energy storage capacitor is ±1%, according to the calculation formula of the ignition power P=C*U*U*f / 2, in the worst case, 1.01*1.01*1.01*1.02=1.051, that is, the error of the present invention can be controlled within ±5.1%, while the igniter using the analog circuit, 1.01*1.05*1.05*1.10=1.225, the error can only be controlled within ±22.5%.

[0039] It is worth noting that the boost module includes a power inductor, which is electrically connected to the energy storage capacitor through a rectifier diode; the boost module is used to enable the power inductor to store energy when the PWM signal output by the drive control module is at a high level; the boost module is also used to enable the power inductor to release energy when the PWM signal output by the drive control module is at a low level, thereby charging the energy storage capacitor.

[0040] In one embodiment, the duty cycle of the PWM signal remains unchanged and is large enough to make the boost module work in a continuous conduction mode. It is worth noting that the continuous conduction mode is CCM mode, i.e., ContinuousConduction Mode. During the period when the power inductor releases energy, before the current flowing through the rectifier diode drops to 0, the PWM signal immediately enters the next PWM cycle. According to the volt-second formula V1*T1=V2*T2, when V1 and T1 are fixed, T2 decreases as V2 increases. In order to ensure the charging speed in the later stage of charging, T2 cannot be too small, so T1, that is, the duty cycle of the PWM signal, cannot be too small. However, V2 is close to 0 in the early stage of charging, so T2 is very large, so that the sum of T1 plus T2 is greater than the PWM cycle. In other words, the energy storage inductor enters the energy storage stage again before it has time to release all the energy, so that the decrease amplitude of the current flowing through the power inductor in the energy release stage is less than the increase amplitude of the current in the energy storage stage, resulting in the rapid superposition and increase of the current flowing through the power inductor. Although the charging speed of this embodiment is particularly fast, the decrease in the current flowing through the power inductor during the energy release stage changes continuously with the change of V2, making it difficult for the drive control module to control the magnitude of the current flowing through the power inductor. Only power inductors with particularly large rated currents can be used, which means particularly high component costs.

[0041] In one embodiment, the duty cycle of the PWM signal increases with the increase of the actual voltage of the energy storage capacitor, and the duty cycle of the PWM signal is large enough to make the boost module work in a continuous conduction mode, that is, the sum of T1 plus T2 in the volt-second formula V1*T1=V2*T2 is equal to the period of the PWM signal. In another embodiment, the duty cycle of the PWM signal increases with the increase of the actual voltage of the energy storage capacitor, and the inductance of the power inductor used is large enough to make the boost module work in a continuous conduction mode.

[0042] In some embodiments, the drive control module is used to control the boost module to operate in a discontinuous conduction mode through the PWM signal. It is worth noting that the discontinuous conduction mode is a DCM mode, i.e., a DiscontinousConduction Mode. During the period when the power inductor releases energy, the current flowing through the rectifier diode drops to 0 before the PWM signal enters the next PWM cycle.

[0043] In one embodiment, the duty cycle of the PWM signal increases with the increase of the actual voltage of the energy storage capacitor, and the duty cycle of the PWM signal is small enough to make the boost module work in a discontinuous conduction mode. In another embodiment, in the early stage of charging, the duty cycle of the PWM signal increases with the increase of the actual voltage of the energy storage capacitor, and the duty cycle of the PWM signal is small enough. In the late stage of charging, the PWM signal remains unchanged, so that the boost module works in a discontinuous conduction mode and limits the current flowing through the power inductor. Although the charging speed is slower, in some applications, the control circuit can use a power inductor with a smaller rated current to reduce component costs.

[0044] According to the volt-second formula V1*T1=V2*T2, no matter which embodiment is used, once the boost module is operated in the continuous conduction mode, the drive control module needs to control T1 with the change of V2, otherwise it will cause the problem of current superposition and rise. It is the most reasonable control scheme to make the sum of T1 plus T2 just equal to the PWM period. However, this is not much different from the embodiment in which the boost module is operated in the discontinuous conduction mode and the sum of T1 plus T2 tends to be equal to the period of the PWM signal. If a more complex control scheme is used, first in the early stage of charging, the sum of T1 plus T2 is made greater than the period of the PWM signal, and then in the later stage of charging, the sum of T1 plus T2 is made equal to the period of the PWM signal. In some applications, it may be possible to make fuller use of the rated current of the power inductor and speed up the charging speed of the energy storage capacitor. However, considering the huge workload brought by the optimization of each application and the influence of program complexity on system reliability, these control methods that make the boost module work in the continuous conduction mode are not obvious. The effect is not the preferred solution.

[0045] Specifically, it also includes a voltage acquisition module, the input end of the voltage acquisition module is electrically connected to the energy storage capacitor, and the output end of the voltage acquisition module is electrically connected to the VOL signal input end of the drive control module; the voltage acquisition module is used to collect the voltage of the energy storage capacitor and transmit it to the drive control module through the VOL signal input end; the drive control module is also used to perform analog-to-digital conversion on the voltage of the energy storage capacitor in real time. The drive control module, the boost module, the trigger discharge module and the voltage sampling module are the core parts of digital charge and discharge management, which are used to replace the traditional analog circuit solution based on the self-excited oscillation principle for charging and based on the trigger voltage or current for automatic discharge. First, the drive control module controls the boost module to charge the energy storage capacitor at a working frequency of more than 31.25kHz through its own PWM peripherals, and then performs real-time analog-to-digital conversion on the signal fed back by the voltage acquisition module at a conversion rate of more than 31.25kHz through its own ADC peripherals. The drive control module will also send the result of the analog-to-digital conversion to a dedicated algorithm unit to adjust the duty cycle of the PWM signal in real time to ensure that the peak current flowing through the inductor during the energy storage period does not exceed the rated use conditions. The energy storage capacitor is charged to the target voltage value at the fastest speed. Then, the drive control module discharges the energy storage capacitor through the trigger discharge module, thereby forming a discharge arc.

[0046] Preferably, it further comprises a power supply module, the input end of the power supply module is electrically connected to the power supply, the output end of the power supply module is electrically connected to the power inductor, and the power supply module is used to supply power to the boost module. Specifically, the power supply is a DC power supply.

[0047] Optionally, the control end of the power supply module is electrically connected to the PWR signal output end of the drive control module; the drive control module is also used to control the power supply module to stop supplying power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor exceeds the preset charging target voltage; and is also used to control the power supply module to supply power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor does not exceed the preset charging target voltage. In one embodiment, before each charging of the energy storage capacitor, the drive control module will first check the voltage of the energy storage capacitor. If it is found that the voltage of the energy storage capacitor is greater than a certain value, such as the voltage of the energy storage capacitor is too high, such as the voltage of the energy storage capacitor is higher than 25V when the input is 12V, it proves that the input voltage is too high, which will affect the control of the maximum value of the charging current by the PWM algorithm, and then prove that the power supply line of the boost module has failed, and the drive control module will stop the ignition task and alarm. If the drive control module finds that the voltage of the energy storage capacitor is not abnormal, the drive control module will output a high-level PWR signal to the power supply module to connect the power supply module.

[0048] Specifically, it also includes an overcurrent detection module, the input end of the overcurrent detection module is electrically connected to the power supply, the output end of the overcurrent detection module is electrically connected to the input end of the power supply module, and the control end of the overcurrent detection module is electrically connected to the TST signal input end of the drive control module; the overcurrent detection module is used to input the TST effective level to the TST signal input end of the drive control module when the power supply line is overcurrent; the drive control module is used to control the power supply module to stop supplying power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor is lower than the preset lower limit threshold and / or when the TST effective level is received. In one embodiment, if the voltage of the energy storage capacitor is too low, for example, the voltage of the energy storage capacitor is less than 15V when the input is 12V, it proves that either the input voltage is too low or there is an abnormality in the subsequent circuit. When the input voltage is too low, the charging current cannot reach the design value, and the discharge frequency cannot be guaranteed; when the subsequent circuit is abnormal, such as the switch tube of the boost module and the thyristor of the trigger discharge module, as long as one of them is short-circuited, the voltage of the energy storage capacitor is zero, and the drive control module needs to cut off the DC power supply to prevent the power supply from being short-circuited. In this embodiment, the TST effective level is a low level. If the control end output of the overcurrent detection module outputs a low-level TST effective level, it can be basically determined that the switch tube of the boost module or the thyristor of the trigger discharge module is short-circuited. Whether there is an abnormality in the voltage of the energy storage capacitor or the control end output of the overcurrent detection module outputs a low-level TST effective level, the drive control module will immediately output a low-level PWR signal to cut off the power supply module after confirming the fault, stop the ignition task and alarm.

[0049] In some embodiments, an automatic power-off module is further included, wherein the input end of the automatic power-off module is electrically connected to the control end of the overcurrent detection module, and the output end of the automatic power-off module is electrically connected to the control end of the power supply module; the automatic power-off module is used to output a power-off signal to the control end of the power supply module when receiving the TST effective level; the power supply module is used to stop supplying power to the boost module after receiving the power-off signal. When the control end output of the overcurrent detection module outputs a low-level TST effective level, in addition to cutting off the power supply module through the drive control module, the power supply module can also be cut off through the automatic power-off module, and dual-line control improves reliability.

[0050] It is worth noting that it also includes a step-down and voltage stabilizing module, the input end of the step-down and voltage stabilizing module is electrically connected to the power supply, the output end of the step-down and voltage stabilizing module is electrically connected to the power supply input end of the drive control module, and the step-down and voltage stabilizing module is used to step down the voltage of the power supply and then supply power to the drive control module. In order to speed up the charging speed, the boost module tends to use a higher voltage power supply. The operating voltage of the drive control module is lower than the voltage of the boost module, so it is necessary to use the step-down and voltage stabilizing module to step down the voltage. In addition, the step-down and voltage stabilizing module also has the function of voltage stabilization, so that the voltage input to the drive control module remains stable, thereby ensuring that the drive control module can work stably.

[0051] Optionally, the drive control module is a microcontroller MCU, the 8MHz oscillator of the drive control module is used to drive the system clock, and the PWM signal is an 8-bit PWM signal. According to the relationship between the voltage and current of the inductor U=L*(di / dt), U is the voltage difference between the two ends of the inductor during the energy storage period of the power inductor, and its value is equal to the input voltage under the ideal circuit model, L is the inductance value of the power inductor, di is the change value of the current flowing through the power inductor during the energy storage period, dt is the duration of the high level of the PWM signal, and the ratio of dt to the PWM period is the duty cycle of the PWM signal. It can be inferred that when the boost module operates in the discontinuous conduction mode, the initial current flowing through the power inductor during the energy storage period is 0, and the peak current is Ip. When Ip is constant, di is constant, L decreases with the decrease of dt, and the decrease of dt means that T1 decreases, and T2 will also decrease, so the period of the PWM signal is also reduced, that is, the higher the operating frequency of the PWM signal, the smaller the required inductance, and the lower the cost of the inductor. In this embodiment, a PWM frequency as high as possible is selected. Similarly, for cost considerations, the control circuit of the digital pulse igniter of the embodiment of the present invention uses a low-end microcontroller MCU. The low-end microcontroller MCU has an 8MHz oscillator for the system clock, and the maximum operating frequency of the 8-bit PWM signal is 8000000 / (2^8)=31.25kHz. Reducing the number of bits of the PWM signal can obtain a higher PWM frequency, but it is necessary to sacrifice the control accuracy. Selecting a microcontroller MCU with a higher frequency can also increase the PWM frequency, but the cost will be higher. In addition, 31.25kHz is equivalent to 32us, and the instruction cycle of the low-end microcontroller MCU with an 8MHz oscillator is often 0.5us. 32us is only enough to execute 64 instructions at most. When it involves a judgment statement that needs to jump, an additional instruction cycle is required, and the number of instructions that can be executed is even less. In addition, the in-and-out interrupt also consumes time, which requires programmers to write highly optimized software code with a very fast execution speed. When the control circuit of the digital pulse igniter of the embodiment of the present invention uses a low-end microcontroller MCU with an 8MHz oscillator, a PWM frequency of 31.25kHz is already the optimal choice. If the frequency is further increased, the reduction in inductance cost is not obvious, and it is difficult to adjust the duty cycle once per PWM cycle.

[0052] like Figure 2 and 3In the embodiment shown, the principle of the control circuit of the digital pulse igniter is as follows: the drive control module will output a PWM signal to control the boost module to charge the energy storage capacitor, and the VOL signal input terminal of the drive control module will track the voltage of the energy storage capacitor in real time through the voltage acquisition module until the energy storage capacitor is charged to the target voltage value. Next, the drive control module will first stop the output of the PWM signal, that is, turn off the boost module, and then the drive control module will output a low-level PWR signal to cut off the power supply module, and then the TRI signal output terminal of the drive control module will output a TRI trigger signal with a fixed high-level duration to the trigger discharge module, thereby triggering the energy storage capacitor to discharge instantly, thereby forming a discharge arc. Among them, Figure 2 The arrow in the figure indicates the direction of signal transmission.

[0053] The reaction speed of the TST effective level generated by the overcurrent detection module is faster than the speed at which the drive control module detects the VOL signal. The use of the TST effective level together with the VOL signal for circuit self-check can enhance the reliability of the system.

[0054] The low level duration of the PWR signal of this embodiment is also controlled. The drive control module uses its own timer to time the discharge frequency. For example, if the charging time is 4ms and the discharge frequency is required to be 200Hz, the low level duration of the PWR signal is about 1ms. If the discharge frequency is required to be 100Hz, the low level duration of the PWR signal is about 6ms. This also means that the control circuit of the digital pulse igniter of this embodiment can increase or decrease the discharge frequency simply by modifying the configuration of the timer. Of course, the core of adjusting the discharge frequency at will is that the charging speed is fast enough, which mainly depends on the power supply voltage and the inductance selected by the boost module, and is also related to the PWM control algorithm of the drive control module. The control circuit of the digital pulse igniter of this embodiment can achieve a shorter charging time and a higher discharge frequency by replacing the inductance selected by the boost module and adjusting the algorithm unit in the program through the relevant calculation formula. For example, under 24V input, a 1016 package 150uH I-shaped inductor can be selected to achieve an ignition power of more than 10W.

[0055] The more stable the trigger voltage, the more stable the maximum ignition distance of the igniter, which is the core parameter of the pulse igniter. The trigger voltage value of the traditional trigger tube discharge solution is relatively fixed, and the accuracy can only reach 5%. The specific trigger voltage value mainly depends on the model of the selected trigger tube, such as Littelfuse's K1800 corresponds to 175V, and K1500 corresponds to 150V; the batch consistency of the trigger voltage value of the traditional thyristor discharge solution is even worse. Whether it is a trigger circuit based on the reverse breakdown voltage of 1N4148 or a trigger circuit based on a voltage regulator, because the circuit is connected in series with a resistor, the specific trigger voltage value is also affected by the trigger current parameter of the thyristor. Various parameter errors will be superimposed and easily affected by the ambient temperature. In addition, when the ignition power needs to be increased, thanks to the digital control technology, the control circuit of the digital pulse igniter in the embodiment of the present invention is quite flexible, and the ignition power can even be doubled by changing the software without changing the hardware circuit. For analog circuits to increase the ignition power, the entire circuit parameters need to be recalculated and adjusted, and adjusting the transformer and switching circuit often involves redesigning the PCB. The whole process is quite complicated and the cost will only be higher.

[0056] Compared with the solution that also uses PWM technology based on the flyback principle to charge the energy storage capacitor through a transformer boost, the embodiment of the present invention can achieve the same ignition power by using a common small-sized I-shaped inductor. The I-shaped inductor has a simple manufacturing process and strong versatility, and its price is much lower than that of a step-up transformer such as EE13, and its reliability is also higher. In addition, because the I-shaped inductor has only one winding and is non-isolated, only one feedback signal is needed to complete the circuit self-test on the low-voltage side and the high-voltage side, while the transformer has two windings, which are isolated from each other and require two feedback signals. Therefore, when using the transformer boost solution to perform circuit self-test, the circuit will be more complicated, and the resources required for the drive control module will also be more.

[0057] In addition, the prior art also has an alternative technical solution for improving the ignition power, which uses 24V power supply, first boosts the voltage to more than 200V through the Boost type switch circuit controlled by the drive control module, and then generates an oscillating square wave with an amplitude of 200V and a duty cycle of 50% through the high-voltage switch tube controlled by the drive control module, and then charges the energy storage capacitor through a resistor during the high voltage period of the square wave, and finally discharges the energy storage capacitor through the thyristor controlled by the drive control module. The charging and discharging of this solution are all controlled by the drive control module. Although it solves the problem of non-ignition caused by the failure to reliably cut off the trigger discharge circuit when the discharge frequency of the traditional analog circuit is too high, and as long as the voltage value after the boost is stable and accurate, the trigger voltage value is also accurate, but this solution has many disadvantages. First, it can only be used for charging for half of the time, and second, the method of charging the energy storage capacitor through a resistor is very inefficient. The higher the ignition power, the more serious the resistance heating, and third, the circuit is complex, the cost is high and the reliability is low. Therefore, it is difficult for this solution to achieve an ignition power of more than 3W. Compared with the existing solution, the embodiment of the present invention has a simpler circuit structure, and the charging part only needs one high-voltage component, and the resource requirements of the drive control module are lower, and a single PWM is sufficient. The existing solution requires multiple high-voltage components and two PWMs, one for boosting and the other for forming a square wave. To achieve the same ignition power, the control circuit of the digital pulse igniter of the embodiment of the present invention is more efficient and is not limited by the RC charging time constant.

[0058] It is worth mentioning that the existing scheme uses 24VDC power supply and uses Boost type switching circuit to directly charge the energy storage capacitor, but the conduction of the trigger tube at the moment of discharge can easily cause the power supply to short-circuit. Designers have to use a very large I-shaped inductor with a large inductance that needs to be specially customized, and a trigger tube with a holding current of up to 150mA, and then hope that the cut-off speed of the trigger tube is fast enough. This scheme will definitely have problems when the discharge time is longer and the actual holding current of the trigger tube is lower. According to the formula U=L*(di / dt), it only takes 12.5us for the inductor current to rise from 0 to 30mA at 24V input and 10mH inductance, and the first cycle of the discharge high voltage is usually greater than 12us. As long as the actual holding current of the trigger tube is lower than 30mA, the trigger tube will not be able to cut off and the power supply will be short-circuited. In addition, this scheme uses a trigger tube with a faster cut-off speed than the thyristor, but the trigger tube can usually only work below 60Hz, so this existing scheme is also difficult to achieve 3W level ignition power. Moreover, the trigger voltage of this existing solution is still based on the specifications of the components themselves, and has limited accuracy. Compared with the existing solution, the embodiments of the present invention do not have the risk of short-circuiting the power supply, the ignition power is not limited by the specifications of the trigger tube, and the ignition power has higher accuracy. The control circuit of the digital pulse igniter only requires a low-cost 220uH I-shaped inductor in a 0810 package, and can achieve an ignition power of 4W with an accuracy of 5% at a 12V input. Compared with traditional pure analog circuit pulse igniters, the present invention achieves more than 10 times the ignition power with a small total cost difference and a smaller PCB size.

[0059] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0060] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0061] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A control circuit of a digital pulse igniter, characterized in that: It includes a drive control module, a boost module, an ignition module, a voltage acquisition module and a trigger discharge module; The ignition module includes an energy storage capacitor and a high-voltage package, the energy storage capacitor is electrically connected to the primary coil of the high-voltage package, and the secondary coil of the high-voltage package is electrically connected to the ignition needle; The feedback input terminal of the drive control module is electrically connected to the ignition module through the voltage acquisition module, and the drive control module is used to adjust the duty cycle of the PWM signal in real time according to the actual voltage of the energy storage capacitor; The PWM signal output end of the drive control module is electrically connected to the control end of the boost module, the boost module is electrically connected to the energy storage capacitor, and the drive control module is further used to control the boost module to charge the energy storage capacitor through the PWM signal; The TRI signal output terminal of the drive control module is electrically connected to the control terminal of the trigger discharge module, the trigger discharge module is electrically connected to the energy storage capacitor, and the drive control module is also used to control the trigger discharge module to discharge the energy storage capacitor through the TRI signal; The boost module includes a power inductor, and the power inductor is electrically connected to the energy storage capacitor through a rectifier diode; The boost module is used to make the power inductor store energy when the PWM signal output by the drive control module is at a high level; the boost module is also used to make the power inductor release energy when the PWM signal output by the drive control module is at a low level, thereby charging the energy storage capacitor; The input end of the voltage acquisition module is electrically connected to the energy storage capacitor, and the output end of the voltage acquisition module is electrically connected to the VOL signal input end of the drive control module; The voltage acquisition module is used to collect the voltage of the energy storage capacitor and transmit it to the drive control module through the VOL signal input terminal; The drive control module is also used to perform analog-to-digital conversion on the voltage of the energy storage capacitor in real time.

2. The control circuit of a digital pulse igniter according to claim 1, characterized in that: The driving control module is used to control the boost module to operate in a discontinuous conduction mode through the PWM signal.

3. The control circuit of a digital pulse igniter according to claim 1, characterized in that: It also includes a power supply module, the input end of the power supply module is electrically connected to the power supply, the output end of the power supply module is electrically connected to the power inductor, and the power supply module is used to supply power to the boost module.

4. The control circuit of a digital pulse igniter according to claim 3, characterized in that: The control end of the power supply module is electrically connected to the PWR signal output end of the drive control module; The drive control module is also used to control the power supply module to stop supplying power to the boost module through the PWR signal output terminal when the voltage of the energy storage capacitor exceeds a preset charging target voltage; It is also used to control the power supply module to supply power to the boost module through the PWR signal output end when the voltage of the energy storage capacitor does not exceed the preset charging target voltage.

5. The control circuit of a digital pulse igniter according to claim 4, characterized in that: It also includes an overcurrent detection module, the input end of the overcurrent detection module is electrically connected to the power supply, the output end of the overcurrent detection module is electrically connected to the input end of the power supply module, and the control end of the overcurrent detection module is electrically connected to the TST signal input end of the drive control module; The overcurrent detection module is used to input a TST effective level to the TST signal input terminal of the drive control module when the power supply line has an overcurrent; The drive control module is used to control the power supply module to stop supplying power to the boost module through the PWR signal output terminal when the voltage of the energy storage capacitor is lower than a preset lower limit threshold and / or when the TST effective level is received.

6. The control circuit of a digital pulse igniter according to claim 5, characterized in that: It also includes an automatic power-off module, wherein the input end of the automatic power-off module is electrically connected to the control end of the overcurrent detection module, and the output end of the automatic power-off module is electrically connected to the control end of the power supply module; The automatic power-off module is used to output a power-off signal to the control end of the power supply module when receiving the TST effective level; The power supply module is used to stop supplying power to the boost module after receiving the power-off signal.

7. The control circuit of a digital pulse igniter according to claim 1, characterized in that: It also includes a step-down and voltage stabilizing module, the input end of the step-down and voltage stabilizing module is electrically connected to the power supply, the output end of the step-down and voltage stabilizing module is electrically connected to the power supply input end of the drive control module, and the step-down and voltage stabilizing module is used to step down the voltage of the power supply to supply power to the drive control module.

8. The control circuit of a digital pulse igniter according to claim 1, characterized in that: The drive control module is a microcontroller MCU, the drive control module uses a system clock with a frequency of 8 MHz, and the PWM signal is an 8-bit PWM signal.

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