A grating AC drive output circuit

Abstract

The present invention discloses a novel AC drive output circuit for a grating, comprising an AC drive circuit connected to an MCU pulse square wave signal transmitting end, the AC drive circuit comprising a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3 and a voltage stabilizing diode D1, the other end of the diode D1 is connected in parallel with the resistor R1 and the grounded capacitor C2 and resistor R3, the emitter of the triode Q1 is grounded, and the collector of the triode Q1 is connected to the fuse F1. In the novel AC drive output circuit for a grating, the square wave of the AC drive circuit provided by the MCU, when the grating of the triode Q1 is triggered, the drive signal becomes a DC low level, and a high level cannot be obtained through the AC drive circuit, and the triode Q1 will be in a disconnected state, thereby the grating outputs an effective triggered signal, and when the MCU program runs away or the MCU itself has a hardware failure, the drive signal is no longer a square wave, but a high level or a low level, and the triode Q1 will be in a disconnected state, which is equivalent to a trigger signal.

Description

Technical Field

[0001] The present invention relates to a grating drive output circuit, in particular to a grating AC drive output circuit. Background Art

[0002] For safety gratings, the physical properties of the electronic components such as chips, resistors, capacitors, etc. used inside, as well as environmental factors, inevitably lead to a certain probability of failure. Although the use of more reliable materials can effectively reduce this risk and improve reliability, the choice of materials is also limited by product design space and cost factors. In other words, the safety grating itself will inevitably have a certain risk of failure. Reasonable design can greatly reduce the risk, but it still exists.

[0003] However, the application scenarios of safety light curtains determine that the reliability requirements for their own work are very high. Once the product fails and cannot give the correct trigger signal, it is very likely to cause a major public security accident.

[0004] This leads to another question that needs to be considered: since failure cannot be avoided 100%, how can we reduce the severity of the consequences of failure? Based on this idea, we abandoned the DC drive output method used by most products on the market and took a different approach to develop a new AC drive output method, which greatly improves the system's ability to resist failure and effectively avoids serious accidents.

[0005] Taking the normally closed NPN output type as an example, Figure 1 This is a schematic diagram of a conventional DC drive output. When the drive signal is a DC high level, it is in a closed state. When the grating is triggered (an obstacle is detected), the drive signal becomes a low level and is disconnected. The grating outputs a valid triggered signal. The advantage of this circuit is that the circuit structure is simple. Figure 2 As shown, the disadvantages are also obvious. When the front-end circuit is abnormal, such as the MCU program runs away or fails to work, the drive signal will no longer flip and change, and will be at a high level or a low level for a long time. If it is at a high level for a long time, it will always be in a closed state. At this time, the processing system of the external device will think that the grating has been normal and cannot detect the trigger signal, which will pose a great safety hazard. Summary of the invention

[0006] The object of the present invention is to provide a grating AC drive output circuit, which has the advantages of greatly improving the system's ability to resist failures and effectively avoiding the occurrence of serious accidents.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a grating AC drive output circuit, comprising an AC drive circuit connected to an MCU pulse square wave signal transmitting end, the AC drive circuit comprising a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3 and a voltage stabilizing diode D1, one end of the capacitor C1 is connected to the MCU, the other end of the capacitor C1 is connected to a parallel interface of a diode D1 and a grounded resistor R2, the capacitor C1 plays a role of AC coupling, isolating the DC and coupling the AC signal, the resistor R2 provides a charging and discharging current path for the capacitor C1, the capacitor C1 and the resistor R2 form a simple high-pass filter, but the cut-off frequency is also affected by the rear-end resistor and capacitor device, the front-end MCU provides a 0V to 3.3V flip high-frequency square wave signal, after passing through the capacitor C1, the signal becomes a -1.65V to +1.65V flip square wave signal symmetrical with the 0 level as the center;

[0008] The diode D1 forms a half-wave rectifier, so that the negative half cycle of the square wave signal from which the DC is removed is blocked, and only the positive half cycle passes. This positive half cycle signal is similar to a square wave, but the amplitude is slightly lower than half of the original square wave signal.

[0009] The other end of the resistor R1 is connected to the base of the transistor Q1, and a DC signal is obtained after filtering by the capacitor C2. The DC signal value is between 1.2V and 1.5V, which is fully capable of driving the output transistor Q1 to conduct.

[0010] The other end of the diode D1 is connected to the resistor R1 and the grounded capacitor C2 and resistor R3 in parallel. The emitter of the transistor Q1 is grounded, and the collector of the transistor Q1 is connected to the fuse F1. The resistor R1 is the base current limiting resistor of the output transistor Q1, and the resistor R3 is the discharge loop of the capacitor C2. When there is no signal from the front end, the charge stored on the capacitor C2 will be quickly released through the resistor R3, and the voltage driving the transistor Q1 will no longer be maintained. The transistor Q1 will be cut off after a very short time delay. When there is a signal from the front end, the capacitor C2 will be charged again to about 1.2V~1.5V to drive the transistor Q1 to saturation conduction.

[0011] Furthermore, the square wave of the AC drive circuit provided by the MCU obtains a high level after shaping and filtering in the AC drive circuit, driving the transistor Q1 output to be in a closed state. When the grating is triggered, the drive signal becomes a DC low level, and cannot obtain a high level through the AC drive circuit, and will be in a disconnected state, thereby the grating outputs a valid triggered signal.

[0012] Furthermore, if the MCU program runs out of control or the MCU itself fails in hardware, the drive signal will no longer be a square wave, but a continuous high level or low level. No effective signal can be obtained through the AC drive circuit, and the transistor Q1 will be in a disconnected state. This abnormal state is equivalent to a trigger signal, which is output to the processing system of the external device.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] In this novel AC drive output circuit of the grating, the square wave of the AC drive circuit provided by the MCU obtains a high level after shaping and filtering in the AC drive circuit, and the output of the driving transistor Q1 is in a closed state. When the grating of the transistor Q1 is triggered, the driving signal becomes a DC low level, and a high level cannot be obtained through the AC drive circuit. The transistor Q1 will be in a disconnected state, so the grating outputs a valid triggered signal. When the MCU program runs away or the MCU itself has a hardware failure, the driving signal will no longer be a square wave, but a continuous high level or low level, and an effective signal cannot be obtained through the AC drive circuit. The transistor Q1 will be in a disconnected state. This abnormal state is equivalent to a trigger signal, which is output to the processing system of the external device. Since the AC drive circuit of this circuit is composed of conventional resistors, capacitors, diodes and other components, its voltage and current specifications are much higher than the system working electrical range, so it has excellent reliability and low cost, which greatly improves the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the existing grating DC drive diagram;

[0016] Figure 2 This is the schematic diagram of the existing grating drive;

[0017] Figure 3 It is the AC drive diagram of the present invention;

[0018] Figure 4 The AC drive principle diagram of the present invention;

[0019] Figure 5 Schematic diagram of voltage waveform of the present invention.

[0020] In the figure: 1. AC drive circuit. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be explained clearly below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] See also Figure 3-4 A grating AC drive output circuit includes an AC drive circuit 1 connected to an MCU pulse square wave signal transmitting end, the AC drive circuit 1 includes a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3 and a voltage stabilizing diode D1, one end of the capacitor C1 is connected to the MCU, the other end of the capacitor C1 is connected to the parallel interface of the diode D1 and the grounded resistor R2, the capacitor C1 plays the role of AC coupling, isolating the DC and coupling the AC signal, the resistor R2 provides a charging and discharging current path for the capacitor C1, the capacitor C1 and the resistor R2 form a simple high-pass filter, but the cut-off frequency will also be affected by the rear-end resistor and capacitor components.

[0023] The front-end MCU provides a high-frequency square wave signal that flips from 0V to 3.3V. After passing through capacitor C1, this signal becomes a square wave signal that flips from -1.65V to +1.65V symmetrically centered on the 0 level. Diode D1 forms a half-wave rectifier, so that the negative half cycle of the DC signal removed from the square wave signal emitted by the front MCU is blocked, and only the positive half cycle passes. This positive half cycle signal is similar to a square wave, but the amplitude is slightly lower than half of the original square wave signal.

[0024] The other end of the resistor R1 is connected to the base of the transistor Q1, and a DC signal is obtained after filtering by the capacitor C2. The DC signal value is between 1.2V and 1.5V, which is fully capable of driving the output transistor Q1 to conduct.

[0025] The other end of the diode D1 is connected to the resistor R1 and the grounded capacitor C2 and resistor R3 in parallel. The emitter of the transistor Q1 is grounded, and the collector of the transistor Q1 is connected to the fuse F1. The resistor R1 is the base current limiting resistor of the output transistor Q1, and the resistor R3 is the discharge loop of the capacitor C2. When there is no signal from the front end, the charge stored on the capacitor C2 will be quickly released through the resistor R3, and the voltage driving the transistor Q1 will no longer be maintained. The transistor Q1 will be cut off after a very short time delay. When there is a signal from the front end, the capacitor C2 will be charged again to about 1.2V~1.5V to drive the transistor Q1 to saturation conduction.

[0026] The square wave of the AC drive circuit 1 provided by the MCU obtains a high level after shaping and filtering in the AC drive circuit 1, and drives the output of the transistor Q1 to be in a closed state. When the grating of the transistor Q1 is triggered, the drive signal becomes a DC low level, and a high level cannot be obtained through the AC drive circuit. The transistor Q1 will be in a disconnected state, so the grating outputs a valid triggered signal. When the MCU program runs away or the MCU itself fails in hardware, the drive signal will no longer be a square wave, but a continuous high level or low level. No effective signal can be obtained through the AC drive circuit 1, and the transistor Q1 will be in a disconnected state. This abnormal state is equivalent to a trigger signal, which is output to the processing system of the external device.

[0027] See also Figure 5 This circuit can drive the transistor Q1 to turn on and off only when the MCU front end provides a high-frequency square wave driving signal. If the front end provides a continuous high level or low level, or even a very low-frequency square wave, it will be filtered out by the high-pass filter composed of capacitor C1 and resistor R2, and the transistor Q1 cannot be driven to work.

[0028] When the grating does not detect an obstacle, the MCU provides a square wave drive signal, which passes through the above drive circuit to drive the output transistor Q1 to turn on and close. When an obstacle is detected, the MCU does not provide a square wave drive signal, but only provides a low level (a high level is also acceptable), and the transistor Q1 is cut off and disconnected.

[0029] If the MCU system is abnormal, it will not be able to maintain the provision of square wave signals. At this time, the transistor Q1 will be in a cut-off state, and this abnormality will be equivalent to a grating trigger signal provided to the external device.

[0030] Since the AC drive circuit of this circuit is composed of conventional resistors, capacitors, diodes and other components, its voltage and current specifications are much higher than the system's operating electrical range, so it has excellent reliability and low cost, greatly improving the overall reliability of the system.

[0031] In summary, in the novel AC drive output circuit of the grating, the square wave of the AC drive circuit 1 provided by the MCU obtains a high level after shaping and filtering in the AC drive circuit 1, and the output of the driving transistor Q1 is in a closed state. When the grating of the transistor Q1 is triggered, the driving signal becomes a DC low level, and a high level cannot be obtained through the AC drive circuit, and the transistor Q1 will be in a disconnected state. Therefore, the grating outputs a valid triggered signal. When the MCU program runs away or the MCU itself fails in hardware, the driving signal will no longer be a square wave, but a continuous high level or low level. No effective signal can be obtained through the AC drive circuit 1, and the transistor Q1 will be in a disconnected state. This abnormal state is equivalent to a trigger signal, which is output to the processing system of the external device. Since the AC drive circuit of this circuit is composed of conventional resistors, capacitors, diodes and other components, its voltage and current specifications are much higher than the system working electrical range, so it itself has excellent reliability and low cost, which greatly improves the overall reliability of the system.

[0032] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A grating AC drive output circuit, characterized in that: The invention comprises an AC drive circuit (1) connected to the pulse square wave signal transmitting end of an MCU, wherein the AC drive circuit (1) comprises a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3 and a voltage stabilizing diode D1, wherein one end of the capacitor C1 is connected to the MCU, and the other end of the capacitor C1 is connected to a parallel interface of the diode D1 and the grounded resistor R2, wherein the capacitor C1 plays the role of AC coupling, isolating the DC and coupling the AC signal, and the resistor R2 provides a charging and discharging current path for the capacitor C1, and the capacitor C1 and the resistor R2 form a simple high-pass filter, but the cut-off frequency is also affected by the rear-end resistor and capacitor components, and the front-end MCU provides a A high-frequency square wave signal that flips from 0V to 3.3V, after passing through capacitor C1, becomes a square wave signal that flips from -1.65V to +1.65V symmetrically with 0 level as the center; the diode D1 constitutes a half-wave rectifier, so that the negative half cycle of the square wave signal that removes the DC is blocked, and only the positive half cycle passes. This positive half cycle signal is similar to a square wave, but the amplitude is slightly lower than half of the original square wave signal; the other end of the resistor R1 is connected to the base of the transistor Q1, and after filtering through capacitor C2, a DC signal is obtained again. The DC signal value is between 1.2V and 1.5V, which is fully capable of driving the output transistor Q1 to conduct; the diode The other end of D1 is connected to the resistor R1 and the grounded capacitor C2 and resistor R3 in parallel. The emitter of transistor Q1 is grounded, and the collector of transistor Q1 is connected to fuse F1. Resistor R1 is the base current limiting resistor of output transistor Q1, and resistor R3 is the discharge circuit of capacitor C2. When there is no signal from the front end, the charge stored on capacitor C2 will be quickly released through resistor R3, and the voltage driving transistor Q1 will no longer be maintained. Transistor Q1 will be cut off after a very short time delay. When there is a signal from the front end, capacitor C2 will be charged to about 1.2V~1.5V again to drive transistor Q1 to saturation conduction. The AC drive provided by MCU The square wave of the AC driving circuit (1) is shaped and filtered to obtain a high level, and the output of the driving transistor Q1 is in a closed state. When the grating is triggered, the driving signal becomes a DC low level, and a high level cannot be obtained through the AC driving circuit. The transistor Q1 will be in a disconnected state, thereby the grating outputs a valid triggered signal. When the MCU program runs away or the MCU itself has a hardware failure, the driving signal will no longer be a square wave, but a continuous high level or low level. No effective signal can be obtained through the AC driving circuit (1), and the transistor Q1 will be in a disconnected state. This abnormal state is equivalent to a trigger signal, which is output to the processing system of the external device.

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