A second pulse interference filtering device

Abstract

A pulse-per-second interference filtering device belongs to the field of electrical physics, and includes a low-pass filter, a feedback network, a comparator, a glitch filter, a pulse-per-second detection device, and a digital-to-analog converter; the input port of the low-pass filter receives a pulse-per-second signal with glitch interference, the output port of the low-pass filter is respectively connected to the feedback network and the input port one of the comparator, the output port of the comparator is connected to the input port of the glitch filter, the output port one of the glitch filter is connected to the input port of the pulse-per-second detection device, the output port two of the glitch filter is connected to the input port of the digital-to-analog converter, and the output port of the digital-to-analog converter is connected to the input port two of the comparator. The present invention utilizes hardware resources to filter interference signals, reduces the device's dependence on the computing resources of an embedded processor, and greatly improves the filtering rate of interference glitch signals on the pulse-per-second signal line, so that the interference glitch signals cannot reach the input detection device.

Description

Technical Field

[0001] The invention belongs to the field of electrical physics, and in particular relates to a pulse-per-second interference filtering device. Background Art

[0002] At present, the pulse-per-second signal line in passenger cars is installed together with other communication signal lines. Under the interference of high current line speed and high-speed data line speed, the pulse-per-second signal line is prone to crosstalk signals and ground voltage fluctuations and other burr interference signals. The pulse-per-second input detection device often mistakenly regards the interference signal as a pulse-per-second signal, resulting in inaccurate trigger time, which seriously affects the input device's judgment of the true pulse-per-second signal.

[0003] The current solution is to use the input device to test the pulse width of the second pulse signal to determine the validity of the signal. In the case of frequent interference signals, the input device needs to consume a lot of computing resources to identify the real second pulse signal. There are certain requirements for the processing power of the embedded processor, see Figure 1 Not only that, but it will also cause incorrect output. Summary of the invention

[0004] The purpose of the present invention is to propose a second pulse interference filtering device, which uses hardware resources to filter interference signals, reduces the device's dependence on the computing resources of an embedded processor, and greatly improves the filtering rate of interference glitch signals on the second pulse signal line, so that the interference glitch signals cannot reach the input detection device, allowing the real second pulse signal to pass through the device.

[0005] The technical solution adopted by the present invention is:

[0006] A second pulse interference filtering device, comprising a low-pass filter, a feedback network, a comparator, a burr filter, a second pulse detection device, and a digital-to-analog converter;

[0007] The input port of the low-pass filter receives a pulse-per-second signal with glitch interference, the output port of the low-pass filter is respectively connected to the feedback network and the input port 1 of the comparator, the output port of the comparator is connected to the input port of the glitch filter, the output port 1 of the glitch filter is connected to the input port of the pulse-per-second detection device, the output port 2 of the glitch filter is connected to the input port of the digital-to-analog converter, and the output port of the digital-to-analog converter is connected to the input port 2 of the comparator;

[0008] The narrow pulse width glitch interference signal is filtered by the low pass filter.

[0009] The narrow pulse width crosstalk spurs are weakened by the first-order low-pass filter and the level peak is below the threshold of the comparator and cannot be recognized by the comparator, forming the first filtering effect.

[0010] Furthermore, the feedback network includes a resistor R1, one end of which is connected to the output port of the low-pass filter, and the other end is respectively connected to the input port 1 of the comparator, resistor R2, and resistor R3, the other end of the resistor R2 is connected to the input port of the glitch filter, and the other end of the resistor R3 is grounded.

[0011] Furthermore, the comparator is a variable threshold comparator, and the medium pulse width burr interference signal is filtered by setting the variable threshold comparator. The comparator forms a second filtering effect.

[0012] Furthermore, the variable threshold comparator adjusts the output voltage of the digital-to-analog converter To adjust the rising edge and falling edge thresholds, the adjustment methods are:

[0013] The rising edge threshold calculation formula is:

[0014] ;

[0015] When the input signal voltage exceeds After that, the comparator output voltage Jump from 0 to 1;

[0016] The falling edge threshold calculation formula is:

[0017] ;

[0018] When the input signal voltage is lower than After that, the comparator output voltage Transitions from 1 to 0.

[0019] When the glitch signal filter frequently detects glitch interference, it will issue instructions to control the output value of the digital-to-analog converter in the variable threshold comparator. , indirectly changing the threshold level and , thereby improving the efficiency of filtering glitch noise.

[0020] Furthermore, for a large pulse width glitch interference signal, neither the low-pass filter nor the variable threshold comparator can filter it. The large pulse width glitch interference signal enters the glitch filter, and the glitch filter samples the input signal through a high-frequency clock. When the level of the input signal remains unchanged for N sampling cycles, it is considered to be a valid second pulse signal. , thereby effectively filtering out the strong interference signals that cannot be filtered by the first two stages (i.e., low-pass filter and variable threshold comparator).

[0021] Furthermore, the N value is in the range of 0 to 100. By setting the N value, a third filtering effect is formed in the burr filter.

[0022] Furthermore, the pulse width of the narrow pulse width glitch interference signal is less than 50 μs, the pulse width of the medium pulse width glitch interference signal is in the range of 50-500 μs, and the pulse width of the large pulse width glitch interference signal is greater than 500 μs and less than 10 ms.

[0023] Beneficial effects of the present invention:

[0024] The present invention detects the frequency of burr interference through an automatic feedback system to automatically adjust the filtering threshold level, and then adjusts the threshold of the comparator through a digital-to-analog converter. and , to filter the medium pulse width interference; by adjusting the internal sampling effective value N of the glitch filter to filter the interference signal of the larger pulse width. That is, the filtering system of the present invention is composed of three stages, the low-pass filter suppresses the narrow pulse width interference burr, the variable threshold comparator suppresses the medium pulse width interference burr, and the glitch filter suppresses the interference signal of the larger pulse width. The three-stage filtering device greatly improves the filtering accuracy.

[0025] Compared with the existing solution of directly filtering interference burrs by testing the pulse-period through a pulse-per-second detection device, the present invention has a higher filtering success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the current burr interference filtering system;

[0027] Figure 2 : is a circuit structure diagram of the device of the present invention, in which U1 is a comparator, and + and - respectively represent the in-phase input terminal and the reverse input terminal of the comparator;

[0028] Figure 3 It is a flow chart of the device of the present invention. DETAILED DESCRIPTION

[0029] like Figure 2 and Figure 3 As shown, a second pulse interference filtering device includes a low-pass filter, a feedback network, a comparator, a burr filter, a second pulse detection device, and a digital-to-analog converter;

[0030] The input port of the low-pass filter receives a second pulse signal with glitch interference, the output port of the low-pass filter is respectively connected to the feedback network and the input port one of the comparator, the output port of the comparator is connected to the input port of the glitch filter, the output port one of the glitch filter is connected to the input port of the second pulse detection device, the output port two of the glitch filter is connected to the input port of the digital-to-analog converter, and the output port of the digital-to-analog converter is connected to the input port two of the comparator; the narrow pulse width glitch interference signal is filtered by the low-pass filter.

[0031] The feedback network includes a resistor R1, one end of which is connected to the output port of the low-pass filter, and the other end is respectively connected to the input port 1 of the comparator, resistor R2, and resistor R3, the other end of the resistor R2 is connected to the input port of the glitch filter, and the other end of the resistor R3 is grounded.

[0032] The comparator is a variable threshold comparator, and the medium pulse width burr interference signal is filtered by setting the variable threshold comparator.

[0033] The variable threshold comparator adjusts the output voltage of the digital-to-analog converter by To adjust the rising edge and falling edge thresholds, the adjustment methods are:

[0034] The rising edge threshold calculation formula is:

[0035] ;

[0036] When the input signal voltage exceeds After that, the comparator output voltage Jump from 0 to 1;

[0037] The falling edge threshold calculation formula is:

[0038] ;

[0039] When the input signal voltage is lower than After that, the comparator output voltage Transitions from 1 to 0.

[0040] When the glitch signal filter frequently detects glitch interference, it will issue instructions to control the output value of the digital-to-analog converter in the variable threshold comparator. , indirectly changing the threshold level and , thereby improving the efficiency of filtering glitch noise.

[0041] For the large pulse width glitch interference signal, the low-pass filter and the variable threshold comparator cannot filter it. The large pulse width glitch interference signal enters the glitch filter. The glitch filter samples the input signal through the high-frequency clock. When the level of the input signal remains unchanged for N sampling cycles, it is considered to be a valid second pulse signal. , thereby effectively filtering out the strong interference signals that cannot be filtered by the first two stages (ie, the low-pass filter and the variable threshold comparator). In this embodiment, the N value is 100.

[0042] The pulse width of the narrow pulse width burr interference signal is less than 50 μs, the pulse width of the medium pulse width burr interference signal is in the range of 50-500 μs, and the pulse width of the large pulse width burr interference signal is greater than 500 μs and less than 10 ms.

[0043] After the pulse-per-second signal with glitch interference passes through the low-pass filter, the narrow pulse width glitch interference is suppressed to below the trigger threshold and filtered, forming the first filtering effect; the medium pulse width glitch interference is then filtered out by the variable threshold comparator; the larger pulse width glitch interference will pass through the comparator and its feedback network, and then enter the glitch filter through the output port of the comparator, and perform high-speed sampling inside the glitch filter. When the high-speed sampling clock inside the glitch filter has multiple rising edges that are sampled to the same level, it is considered to be a valid jump edge, and a valid signal can be output, thereby filtering out the larger pulse width glitch interference. When the glitch filter detects frequent interference entering, the glitch filter will issue a command to adjust the voltage of the digital-to-analog converter. , raising or lowering the threshold of the comparator, allowing fewer interference pulse signals to pass through the comparator, forming a feedback filtering system.

Claims

1. A pulse-second interference filtering device, characterized in that: It includes low-pass filter, feedback network, comparator, glitch filter, pulse-per-second detection device, and digital-to-analog converter; The input port of the low-pass filter receives a pulse-per-second signal with glitch interference, the output port of the low-pass filter is respectively connected to the feedback network and the input port 1 of the comparator, the output port of the comparator is connected to the input port of the glitch filter, the output port 1 of the glitch filter is connected to the input port of the pulse-per-second detection device, the output port 2 of the glitch filter is connected to the input port of the digital-to-analog converter, and the output port of the digital-to-analog converter is connected to the input port 2 of the comparator; the narrow pulse width glitch interference signal is filtered by the low-pass filter, and the pulse width of the narrow pulse width glitch interference signal is less than 50μs; The feedback network includes a resistor R1, one end of which is connected to the output port of the low-pass filter, and the other end of which is respectively connected to the input port 1 of the comparator, the resistor R2, and the resistor R3, the other end of which is connected to the input port of the glitch filter, and the other end of which is grounded; The comparator is a variable threshold comparator, and the medium pulse width burr interference signal is filtered by setting the variable threshold comparator, and the pulse width of the medium pulse width burr interference signal is in the range of 50-500 μs; The variable threshold comparator adjusts the output voltage of the digital-to-analog converter by To adjust the thresholds of the rising edge and the falling edge, the adjustment methods are: The rising edge threshold calculation formula is: ， When the input signal voltage exceeds After that, the comparator output voltage Jump from 0 to 1; The falling edge threshold calculation formula is: ， When the input signal voltage is lower than After that, the comparator output voltage Transitions from 1 to 0.

2. A pulse-per-second interference filtering device as claimed in claim 1, characterized in that: For the large pulse width glitch interference signal, the low-pass filter and the variable threshold comparator cannot filter it. The large pulse width glitch interference signal enters the glitch filter. The glitch filter samples the input signal through the high-frequency clock. When the level of the input signal remains unchanged for N sampling cycles, it is considered to be a valid second pulse signal. V oFiltter , thereby effectively filtering out the strong interference signals that cannot be filtered out by the first two stages; the pulse width of the larger pulse width burr interference signal is greater than 500μs and less than 10ms.

3. A pulse-per-second interference filtering device as claimed in claim 2, characterized in that: The N value is in the range of 0 to 100.

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