A PWM output control circuit

Abstract

The application discloses a PWM output control circuit, which comprises a relay, a relay control module, an isolation conversion module and a protection module; the input end of the relay control module is connected with the control signal input end of the PWM output control circuit, and the output end of the relay control module is connected with the control end of the relay; the first contact and the second contact of the relay are connected with the PWM signal output end and the reference ground output end of the PWM output control circuit respectively; the input end of the isolation conversion module is connected with the PWM signal input end of the PWM output control circuit, the output end of the isolation conversion module is connected with the input end of the protection module, and the output end of the protection module is connected with the first common contact of the relay; the isolation conversion module is used for boosting and converting the input PWM signal and then outputting the PWM signal through the protection module. Through the PWM output control circuit, safe and effective control of the PWM signal output is realized, and the safety of the PWM output system is improved.

Description

Technical Field

[0001] This invention relates to the field of circuit control technology, and in particular to a PWM output control circuit. Background Technology

[0002] Pulse Width Modulation (PWM) circuits are used to control the switching on and off of switching devices in inverter circuits and are applied in various high-power circuits.

[0003] However, typical PWM output circuits are used to output PWM signals, which are susceptible to external electromagnetic interference, resulting in errors in the PWM signal duty cycle and an inability to directly intervene in the output of the PWM signal, which is detrimental to system safety. Summary of the Invention

[0004] This invention provides a PWM output control circuit to solve the safety problem of PWM output systems.

[0005] According to one aspect of the present invention, a PWM output control circuit is provided, including a relay, a relay control module, an isolation conversion module, and a protection module;

[0006] The input terminal of the relay control module is connected to the control signal input terminal of the PWM output control circuit, and the output terminal of the relay control module is connected to the control terminal of the relay. The relay control module is used to control the power-on or power-off of the relay.

[0007] The relay includes a first common contact, a second common contact, a first contact, and a second contact; the relay is used to control the first common contact to connect with the first contact and the second common contact to the second contact when powered on, and to control the first common contact to disconnect with the first contact and the second common contact to disconnect with the second contact when powered off, wherein the second common contact is grounded; the first contact and the second contact are respectively connected to the PWM signal output terminal and the reference ground output terminal of the PWM output control circuit;

[0008] The input terminal of the isolation conversion module is connected to the PWM signal input terminal of the PWM output control circuit, the output terminal of the isolation conversion module is connected to the input terminal of the protection module, and the output terminal of the protection module is connected to the first common contact of the relay. The isolation conversion module is used to boost and convert the PWM signal input from the input terminal and output it through the protection module.

[0009] Optionally, the relay control module includes a first Schmitt trigger and a power-on control circuit; the input terminal of the first Schmitt trigger is connected to the control signal input terminal, and the output terminal of the first Schmitt trigger is connected to the control terminal of the power-on control circuit; the input terminal of the power-on control circuit is connected to a first power supply, and the output terminal of the power-on control circuit is connected to the control terminal of the relay; the power-on control circuit is used to control the relay to power on or off according to the signal from its own control terminal.

[0010] Optionally, the power-on control circuit includes a first resistor, a second resistor, and a transistor; the first terminal of the transistor serves as the input terminal of the power-on control circuit and is connected to the first power supply, the second terminal of the transistor serves as the output terminal of the power-on control circuit and is connected to the first terminal of the relay coil, and the second terminal of the relay coil is grounded; one end of the first resistor is connected to the base of the transistor, and the second end of the first resistor serves as the control terminal of the power-on control circuit; the second resistor is connected between the first terminal and the base of the transistor.

[0011] Optionally, the power-on control circuit further includes a first diode, the cathode of which is connected to a first terminal of the relay coil, and the anode of which is connected to a second terminal of the relay coil.

[0012] Optionally, the isolation conversion module includes a second Schmitt trigger and a voltage isolation conversion circuit; the input terminal of the second Schmitt trigger is connected to the input terminal of the PWM signal, the output terminal of the second Schmitt trigger is connected to the input terminal of the voltage isolation conversion circuit, and the output terminal of the voltage isolation conversion circuit is connected to the input terminal of the protection module; the voltage isolation conversion circuit is used to boost the PWM signal and transmit it to the first common contact via the protection module.

[0013] Optionally, the voltage isolation conversion circuit includes an optocoupler.

[0014] Optionally, the PWM output control circuit further includes a third resistor connected between the input terminal of the second Schmitt trigger and the ground terminal.

[0015] Optionally, the protection module includes a second diode, a third diode, and a fuse; the cathode of the second diode is connected to the output terminal of the voltage isolation conversion circuit, and the anode of the second diode is grounded; the anode of the third diode is connected to the output terminal of the voltage isolation conversion circuit, the cathode of the third diode is connected to the first terminal of the fuse, and the second terminal of the fuse is connected to the PWM signal output terminal of the PWM output control circuit.

[0016] Optionally, the protection module further includes a first capacitor; the first capacitor is connected between the second end of the fuse and the anode of the second diode.

[0017] According to another aspect of the present invention, a train automatic operation system is provided, including a control module and a PWM output control circuit; the control signal input terminal is connected to a first output terminal of the control module, and the PWM signal input terminal is connected to a second output terminal of the control module. The PWM output control circuit is applied to the train operation system and is connected to the control module of the train operation system to control the PWM signal output by the control module, thereby improving the safety of the train operation system.

[0018] This invention provides a PWM output control circuit, including a relay, a relay control module, an isolation conversion module, and a protection module. The input terminal of the relay control module is connected to the control signal input terminal of the PWM output control circuit, and the output terminal of the relay control module is connected to the control terminal of the relay. The relay controls the first common contact to connect with the first contact and the second common contact to the second contact when powered on, and controls the first common contact to disconnect from the first contact and the second common contact to the second contact when powered off. The input terminal of the isolation conversion module is connected to the PWM signal input terminal of the PWM output control circuit, and the output terminal of the isolation conversion module is connected to the input terminal of the protection module. The output terminal of the protection module is connected to the first common contact of the relay. The isolation conversion module boosts and converts the PWM signal input to the input terminal and outputs it through the protection module. By setting a relay control module in the PWM output control circuit to control the power-on and power-off of the relay, safe and effective control of the PWM signal output is achieved, improving the safety of the PWM output system.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a real-time waveform diagram of the PWM signal output by the frequency converter provided in Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of a PWM output control circuit structure provided in Embodiment 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of the relay control module structure provided in Embodiment 2 of the present invention;

[0024] Figure 4 This is a circuit diagram of the relay control module provided in Embodiment 2 of the present invention;

[0025] Figure 5 This is a schematic diagram of the isolation transformation module provided in Embodiment 3 of the present invention;

[0026] Figure 6 This is a circuit connection diagram of the isolation conversion module and the protection module provided in Embodiment 3 of the present invention;

[0027] Figure 7 This is a schematic diagram of the PWM output control structure of a train automatic operation system provided in Embodiment 4 of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] Figure 1 This is a real-time waveform diagram of the PWM signal output by the inverter provided in this embodiment of the invention. The PWM circuit is used to control the on / off switching of the switching devices in the inverter circuit and is applied in various high-power circuits. For example... Figure 1As shown, a PWM circuit can output a series of pulses with equal amplitude but inconsistent widths. These pulses can replace a sine wave or the desired waveform, generating multiple pulses within half a cycle of the output waveform. This ensures that the equivalent voltage of each pulse is a sine wave, resulting in a smooth output with fewer low-order harmonics. By modulating the width of each pulse according to certain rules, both the magnitude of the inverter circuit's output voltage and the output frequency can be changed. For example, dividing a sine half-wave waveform into N equal parts allows us to view it as a waveform composed of N interconnected pulses. These pulses have equal widths, all equal to π / n, but unequal amplitudes, and their peaks are not horizontal straight lines but curves. The amplitude of each pulse varies sinusoidally. If the above pulse sequence is replaced with the same number of rectangular pulse sequences of equal amplitude but unequal width, such that the midpoint of the rectangular pulse coincides with the midpoint of the corresponding sine wave division, and the area (impulse) of the rectangular pulse and the corresponding sine wave portion are equal, a pulse sequence, i.e., a PWM waveform, is obtained. It can be seen that the width of each pulse changes according to a sinusoidal pattern. Based on the principle that equal impulse has the same effect, the PWM waveform and the half-wave of a sine wave are equivalent. The same method can be used to obtain the PWM waveform for the negative half-cycle of the sine wave. In the PWM waveform, the amplitude of each pulse is equal. To change the amplitude of the equivalent output sine wave, simply change the width of each pulse by the same proportional coefficient. Therefore, in an AC-DC-AC inverter, the pulse voltage output by the PWM inverter circuit is the amplitude of the DC side voltage. Based on the above principle, given the sine wave frequency, amplitude, and the number of pulses in half a cycle, the width and interval of each pulse in the PWM waveform can be accurately calculated. By controlling the on / off state of each switching device in the control circuit according to the calculation results, the required PWM waveform can be obtained. In the field of railway locomotive speed control technology, the control module outputs a PWM wave to the wheel drive module, and the duty cycle of the PWM signal determines the speed. Due to external electromagnetic interference during train operation, the voltage amplitude increases, causing the PWM signal to change from low to high level, posing a safety hazard to speed control.

[0031] In view of this, embodiments of the present invention provide a PWM output control circuit that processes the PWM wave output by the control module and outputs it to the wheel drive module to solve the safety hazard of vehicle speed control caused by the increase in voltage amplitude due to external electromagnetic interference. Figure 2 This is a schematic diagram of a PWM output control circuit structure provided in an embodiment of the present invention, as shown below. Figure 2As shown, the PWM output control circuit 200 provided in this embodiment of the invention includes: a relay 210, a relay control module 220, an isolation conversion module 230, a protection module 240, a control signal input terminal 203, a PWM signal input terminal 204, and a PWM signal output terminal 205. The relay control module 220 includes an input terminal 250 and an output terminal 260; the relay 210 includes a control terminal 270, a first common contact 211, a second common contact 212, a first contact 213, and a second contact 214; the isolation conversion module 230 includes an input terminal 280 and an output terminal 290; and the protection module 240 includes an input terminal 201 and an output terminal 202.

[0032] In this embodiment, the input terminal 250 of the relay control module 220 is connected to the control signal input terminal 203 of the PWM output control circuit, and the output terminal 260 of the relay control module 220 is connected to the control terminal 270 of the relay 210. The relay control module 220 is used to control the power-on or power-off of the relay 210. The relay 210 includes a first common contact 211, a second common contact 212, a first contact 213, and a second contact 214. When powered on, the relay 210 controls the first common contact 211 to connect with the first contact 213 and the second common contact 212 to connect with the second contact 214. When powered off, the relay 210 controls the first common contact 211 to disconnect from the first contact 213 and the second common contact 212 to disconnect from the second contact 214. The second common contact 212 is grounded. The first contact 213 and the second contact 214 are respectively connected to the PWM signal output terminal 205 and the reference ground output terminal of the PWM output control circuit. The input terminal 280 of the isolation conversion module 230 is connected to the PWM signal input terminal 204 of the PWM output control circuit, the output terminal 290 of the isolation conversion module 230 is connected to the input terminal 201 of the protection module 240, and the output terminal 202 of the protection module 240 is connected to the first common contact 211 of the relay. The isolation conversion module 230 is used to boost and convert the PWM signal input from the input terminal and then output it through the protection module 240.

[0033] In this embodiment, relay 210 is an electrical control device that causes a predetermined step change in the controlled quantity when the change in the input quantity reaches a specified requirement. Relay 210 acts as an automatic switch that controls a large current operation with a small current, playing roles in automatic adjustment, safety protection, and circuit switching. Optionally, relay 210 can be a safety relay, which has advantages over ordinary relays such as a wider supported switching power range and higher dielectric strength. The control signal input terminal 203 of the PWM output control circuit is connected to an external control module. The external control module can send switching signals to the PWM output control circuit through the control signal input terminal 203. For example, the switching signal can be represented by high and low levels, or by digital logic "1" and digital logic "0". The control signal input terminal 203 of the PWM output control circuit is connected to the input terminal 250 of the relay control module 220. Switching signals generated by the external control module are sent to the relay control module 220. The output terminal 260 of the relay control module 220 is connected to the control terminal 270 of the relay 210. The relay control module 220 controls the power-on or power-off of the relay 210 through the control terminal 270 of the relay 210 based on the received switching signals. For example, when the switching signal output by the external control module is high, the relay control module 220 controls the relay 210 to power on; when the switching signal output by the external control module is low, the relay control module 220 controls the relay 210 to power off.

[0034] In this embodiment, relay contacts can be understood as contacts that enable or disable signals. When the control terminal 270 of relay 210 receives a control signal from relay control module 220, relay 210 performs corresponding power-on or power-off actions. When relay 210 is powered on, the first common contact 211 and the first contact 213 are connected, and the second common contact 212 and the second contact 214 are connected; when relay 210 is powered off, the first common contact 211 and the first contact 213 are disconnected, and the second common contact 212 and the second contact 214 are disconnected. The second common contact 212 of relay 210 is grounded, and the grounding terminal is analog ground (AGND). The first contact 213 is connected to the PWM signal output terminal 205 of the PWM output control circuit. The PWM signal output terminal 205 of the PWM output control circuit can be understood as the port in the PWM output control circuit that outputs the PWM signal. The PWM signal is transmitted to relay 210 through the PWM signal output terminal 205. The second contact 214 is connected to the reference ground output terminal, which can be understood as a reference point with zero potential and is the common terminal that constitutes the signal loop of the circuit.

[0035] In this embodiment, the isolation conversion module 230 may include an isolation converter, which can convert the input current and voltage into the required current and voltage, and the power supply, input terminal, and output terminal are mutually isolated. The PWM signal input terminal 204 of the PWM output control circuit is connected to an external control module, which can generate a PWM signal and send it to the PWM output control circuit through the PWM signal input terminal 204. The PWM signal input terminal 204 of the PWM output control circuit is connected to the input terminal 280 of the isolation conversion module 230, and the PWM signal generated by the external control module is sent to the isolation conversion module 230. The output terminal 290 of the isolation conversion module 230 is connected to the input terminal 201 of the protection module 240. The PWM signal generated by the external control module is transmitted to the protection module 240 through the isolation conversion module 230. The protection module 240 is used to prevent unstable factors such as overcurrent and overvoltage in the circuit from affecting the circuit effect. The output terminal 202 of the protection module 240 is connected to the first common contact 211 of the relay, and the PWM signal is output to the first common contact 211 of the relay 210 through the protection module 240.

[0036] In the PWM output control circuit, the PWM signal input terminal 204 is connected to the external control module and the input terminal 280 of the isolation conversion module 230. The PWM signal generated by the external control module can be sent to the isolation conversion module 230. The output terminal 290 of the isolation conversion module 230 is connected to the input terminal 201 of the protection module 240. The PWM signal is transmitted to the protection module 240 through the isolation conversion module 230. The output terminal 202 of the protection module 240 is connected to the first common contact 211 of the relay. The control signal input terminal 203 is connected to the external control module and the input terminal 250 of the relay control module 220. The switch signal generated by the external control module is sent to the relay control module 220. The output terminal 260 of the relay control module 220 is connected to the control terminal 270 of the relay 210. The relay control module 220 can control the relay 210 to power on or off according to the received switch signal. When the relay is powered on, the first common contact 211 and the first contact 213 are connected. Referring to the above embodiment, the first contact 213 is connected to the PWM signal output terminal 205 of the PWM output control circuit. Since the first common contact 211 can receive the PWM signal, the PWM signal output terminal 205 has a PWM signal output at this time. When the relay 210 is powered off, the first common contact 211 and the first contact 213 are disconnected. At this time, the PWM signal output terminal 205 has no PWM signal output.

[0037] This embodiment provides a PWM output control circuit, including a relay, a relay control module, an isolation conversion module, and a protection module. The input terminal of the relay control module is connected to the control signal input terminal of the PWM output control circuit, and the output terminal of the relay control module is connected to the control terminal of the relay. The relay controls the first common contact to connect with the first contact and the second common contact to the second contact when powered on, and controls the first common contact to disconnect from the first contact and the second common contact to the second contact when powered off. The input terminal of the isolation conversion module is connected to the PWM signal input terminal of the PWM output control circuit, and the output terminal of the isolation conversion module is connected to the input terminal of the protection module. The output terminal of the protection module is connected to the first common contact of the relay. The isolation conversion module is used to boost and convert the PWM signal input to the input terminal and output it through the protection module. By setting an isolation conversion module in the PWM output control circuit, external electromagnetic interference can be eliminated, making the PWM output more accurate. Simultaneously, the relay control module controls the power-on and power-off of the relay, achieving safe and effective control of the PWM signal output and improving the safety of the PWM output system.

[0038] Figure 3 This is a schematic diagram of the relay control module structure provided in an embodiment of the present invention, as shown below. Figure 3 As shown, it includes a relay control module 220, a first Schmitt trigger 310, and a power-on control circuit 320.

[0039] Based on the above embodiments, the relay control module 220 includes a first Schmitt trigger 310 and a power-on control circuit 320.

[0040] In this embodiment, the Schmitt trigger is a comparator circuit containing positive feedback. For a standard Schmitt trigger, the output is high when the input voltage is higher than the positive threshold voltage; the output is low when the input voltage is lower than the negative threshold voltage; and the output does not change when the input voltage is between the positive and negative threshold voltages. That is, the threshold voltages corresponding to the output flipping from a high level to a low level, or from a low level to a high level, are different. The output only changes when the input voltage changes sufficiently, hence the name "flip-flop." This double-threshold action is called hysteresis, indicating that the Schmitt trigger has memory. Essentially, the Schmitt trigger is a bistable multivibrator. Schmitt triggers can be used as waveform shaping circuits to shape analog signal waveforms into square wave waveforms that can be processed by digital circuits. Moreover, due to their hysteresis characteristics, Schmitt triggers can be used for interference suppression, for example, to prevent digital logic "1" from being misinterpreted as digital logic "0" or vice versa. Their applications include interference suppression in open-loop configurations and the implementation of multivibrators in closed-loop positive / negative feedback configurations.

[0041] In the relay control module 220, the first Schmitt trigger 310 is connected to the control signal input terminal 203 and receives the switching signal. The first Schmitt trigger 310 performs anti-interference processing on the switching signal input to the control signal input terminal 203 based on the hysteresis characteristic of the Schmitt trigger. The first Schmitt trigger 310 is connected to the power-on control circuit 320 and sends the processed switching signal to the power-on control loop 320. The power-on control loop 320 is connected to the relay 210, and the power-on control loop 320 controls the power-on or power-off of the relay 210 according to the received switching signal.

[0042] For example, Figure 4 This is a circuit schematic diagram of the relay control module provided in an embodiment of the present invention, such as... Figure 4 As shown, the system includes a relay 210, a relay control module 220, a first common contact 211 of the relay, a second common contact 212 of the relay, a first contact 213 of the relay, a second contact 214 of the relay, a PWM signal output terminal 205, a relay control terminal 270, a first Schmitt trigger 310, a power-on control circuit 320, a first Schmitt trigger input terminal 410, a first Schmitt trigger output terminal 420, a power-on control circuit control terminal 430, a power-on control circuit input terminal 440, a first power supply 450, a power-on control circuit output terminal 460, a first resistor 470, a second resistor 480, a transistor 490, a first terminal 401 of the relay coil, a second terminal 402 of the relay coil, a first terminal 403 of the first resistor, a second terminal 404 of the first resistor, a first diode 405, and a second capacitor 406.

[0043] In this embodiment, the input terminal 410 of the first Schmitt trigger 310 is connected to the control signal input terminal 203, and the output terminal 420 of the first Schmitt trigger 310 is connected to the control terminal 430 of the power-on control circuit 320; the input terminal 440 of the power-on control circuit 320 is connected to the first power supply 450, and the output terminal 460 of the power-on control circuit 320 is connected to the relay control terminal 270. The power-on control circuit 320 is used to control the relay 210 to power on or off according to the signal from its own control terminal 430.

[0044] In the relay control module 220, the first Schmitt trigger 310 is connected between the control signal input terminal 203 and the power-on control circuit 320. The first Schmitt trigger 310 processes the received switching signal to remove interference signals, making the switching signal more accurate. For example, the first Schmitt trigger can be an SN74LVC1G06DBV type Schmitt trigger. Pin 2 of the SN74LVC1G06DBV type Schmitt trigger (i.e., the input terminal 410 of the first Schmitt trigger) receives the switching signal. The SN74LVC1G06DBV type Schmitt trigger is used to prevent digital logic output errors caused by voltage fluctuations (i.e., misinterpreting digital logic "1" as digital logic "0" or misinterpreting digital logic "0" as digital logic "1"). Pin 3 of the SN74LVC1G06DBV Schmitt trigger is grounded, and pin 4 (i.e., the output terminal 420 of the first Schmitt trigger) is connected to the control terminal 430 of the power-on control circuit. The SN74LVC1G06DBV Schmitt trigger can transmit a precise switching signal to the power-on control circuit 320. There are no restrictions on the selection of the first Schmitt trigger.

[0045] The control terminal 430 of the power-on control circuit 320 is connected to the output terminal 420 of the first Schmitt trigger 310. The power-on control circuit 320 receives a precise switching signal through the control terminal 430. The input terminal 440 of the power-on control circuit 320 is connected to the first power supply 450, which can be a 5V power supply. The first power supply 450 is grounded through series connection with the second capacitor 406, which can filter out high-frequency AC interference signals in the 5V DC power. The output terminal 460 of the power-on control circuit 320 is connected to the relay control terminal 270. The power-on control circuit 320 achieves precise control of the relay's power-on and power-off states based on the received precise switching signal.

[0046] In this embodiment, the power-on control circuit 320 includes a first resistor 470, a second resistor 480, and a transistor 490. The first terminal of the transistor 490 serves as the input terminal 440 of the power-on control circuit 320 and is connected to the first power supply 450. The second terminal of the transistor 490 serves as the output terminal 460 of the power-on control circuit 320 and is connected to the first terminal 401 of the coil of the relay 210. The second terminal 402 of the coil of the relay is grounded. The first terminal 403 of the first resistor 470 is connected to the base of the transistor 490, and the second terminal 404 of the first resistor 470 serves as the control terminal 430 of the power-on control circuit 320. The second resistor 480 is connected between the first terminal and the base of the transistor 490.

[0047] In this circuit, the first resistor 470 is connected between the control terminal 430 of the power-on control circuit and the base of the transistor 490, and the second terminal 404 of the first resistor 470 can serve as the control terminal 430 of the power-on control circuit. The first resistor 470 can be selected as a 1kΩ resistor. The second resistor 480 is connected between the first terminal and the base of the transistor 490 to improve the stability of the circuit. The second resistor 480 can be selected as a 4.7kΩ resistor. The second terminal of the transistor 490 is connected to the first terminal 401 of the relay coil. The second terminal of the transistor 490 serves as the output terminal 460 of the power-on control circuit 320, which can transmit the switching signal output by the power-on control circuit 320 to the coil of the relay 210. The second terminal 402 of the relay coil is grounded. The relay 210, as an electronic control device, can include a control unit and a switching unit. The coil of the relay 210 serves as the control unit, and the contacts of the relay 210 serve as the switching unit. Transistor 490 functions as a switch. This embodiment does not limit the selection of transistor 490. For example, MMSS8550-H-TP type PNP transistor can be used. When the MMSS8550-H-TP type PNP transistor is turned on, it connects the first power supply 450 to the relay coil. When it is turned off, it controls the disconnection of the first power supply 450 from the relay coil, i.e., controlling the energization and de-energization of the relay coil. The coil of relay 210 controls the action of the relay 210 contacts according to the received power signal, thus completing the energization and de-energization of relay 210. Relay 210 can be a G5V-2-DC5 type safety relay. The G5V-2-DC5 type safety relay can withstand an external surge voltage of 1500V, protecting the safety of internal system components.

[0048] The relay control module 220 also includes a first diode 405. The cathode of the first diode 405 is connected to the first terminal 401 of the coil of the relay 210, and the anode of the first diode 405 is connected to the second terminal 402 of the coil of the relay 210. The first diode 405 is connected in parallel with the relay 210 to prevent the relay coil from being broken down by the reverse current input from the outside. For example, the first diode 405 can be a 1N5819HW-7-F type diode, and there is no limitation on this.

[0049] In this embodiment, a first Schmitt trigger is incorporated into the relay control module to perform anti-interference processing on the input switching signal, preventing digital logic output errors caused by voltage fluctuations and resulting in a more accurate output switching signal. A power-on control circuit is also included in the relay control module to amplify the switching signal; the amplified voltage is used to control the relay's power-on and power-off states. After passing through the first Schmitt trigger and the power-on control circuit, the switching signal is transmitted to the relay control terminal, enabling precise control of the relay's power-on and power-off states.

[0050] This embodiment is a refinement based on the above embodiments. Figure 5 This is a schematic diagram of the isolation transformation module provided in an embodiment of the present invention, as shown below. Figure 5 As shown, it includes an isolation conversion module 230, a second Schmitt trigger 510, and a voltage isolation conversion circuit 520.

[0051] Based on the above embodiments, the isolation conversion module 230 includes a second Schmitt trigger 510 and a voltage isolation conversion circuit 520. The second Schmitt trigger 510, based on the hysteresis characteristic of a Schmitt trigger, can be used for anti-interference. The voltage isolation conversion circuit 520 can isolate the power supply, input terminal, and output terminal from each other, and convert the input voltage signal into the voltage signal required by the output terminal. Optionally, the voltage isolation conversion circuit includes an optocoupler, which is an electro-optical-electrical conversion device that transmits electrical signals using light as a medium, with its light source pin as the input terminal and the light-receiving pin as the output terminal. The second Schmitt trigger 510 is connected to the PWM signal input terminal 204 and receives the PWM signal. The second Schmitt trigger 510 is connected to the voltage isolation conversion circuit 520 and transmits the received PWM signal to the voltage isolation conversion circuit 520. The voltage isolation conversion circuit 520 is connected to the protection module 240 and transmits the PWM signal to the protection module 240.

[0052] For example, Figure 6 This is a circuit connection diagram of the isolation conversion module and the protection module provided in Embodiment 3 of the present invention. Figure 6 As shown, the circuit includes an isolation conversion module 230, a protection module 240, a PWM signal input terminal 204, a PWM signal output terminal 205, a second Schmitt trigger 510, a voltage isolation conversion circuit 520, a second Schmitt trigger input terminal 610, a second Schmitt trigger output terminal 620, a voltage isolation conversion circuit input terminal 630, a voltage isolation conversion circuit output terminal 640, a protection module input terminal 650, a third resistor 660, a second Schmitt trigger ground terminal 670, a second diode 680, a third diode 690, a fuse 601, a fuse first terminal 602, a fuse second terminal 603, a first capacitor 604, a second power supply 605, a third capacitor 606, a fourth resistor 607, and a third power supply 608.

[0053] In this embodiment, the input terminal 610 of the second Schmitt trigger 510 is connected to the PWM signal input terminal 204, the output terminal 620 of the second Schmitt trigger 510 is connected to the input terminal 630 of the voltage isolation conversion circuit 520, and the output terminal 640 of the voltage isolation conversion circuit 520 is connected to the input terminal 650 of the protection module 240. The voltage isolation conversion circuit 520 is used to boost the PWM signal and transmit it to the first common contact 211 through the protection module 240.

[0054] In the isolation conversion module 230, the second Schmitt trigger 510 is connected between the PWM signal input terminal 204 and the voltage isolation conversion circuit input terminal 630. The second Schmitt trigger 510 performs anti-interference processing on the input PWM signal and transmits the processed PWM signal to the isolation conversion circuit 520, making the PWM signal more accurate. For example, the second Schmitt trigger 510 can be an SN74LVC1G17DBV type Schmitt trigger. Pin 2 of the SN74LVC1G17DBV type Schmitt trigger (i.e., the input terminal 610 of the second Schmitt trigger) receives the PWM signal, and pin 3 of the SN74LVC1G17DBV type Schmitt trigger is grounded. A third resistor 660 is also included between pin 2 and pin 3 of the SN74LVC1G17DBV type Schmitt trigger, and the third resistor 660 can be a 10kΩ resistor. Pin 4 of the SN74LVC1G17DBV type Schmitt trigger (i.e., the output terminal 620 of the second Schmitt trigger) outputs the PWM signal. Pin 4 of the SN74LVC1G17DBV type Schmitt trigger is connected to a second power supply 605, which can be a 5V voltage source. The second power supply 605 is connected in series with a third capacitor 606 and grounded. The selection of the second Schmitt trigger 510 is not limited.

[0055] The isolation converter circuit 520 amplifies the input PWM signal. For example, the isolation converter circuit 520 can use a FOD3120SD type optocoupler, which can convert a 3.3V input PWM signal to a 24V PWM signal; this is not limited. A fourth resistor 607 is connected in series between pin 2 of the FOD3120SD type optocoupler (i.e., the input terminal 630 of the voltage isolation converter circuit) and the output terminal 620 of the second Schmitt trigger, ensuring that the voltage at the input terminal 630 of the voltage isolation converter circuit is 3.3V. Pin 3 and pin 5 of the FOD3120SD type optocoupler are grounded. Pins 6 and 7 of the FOD3120SD type optocoupler serve as the output terminal 640 of the voltage isolation converter circuit. Pin 8 of the FOD3120SD type optocoupler is connected to a third power supply 608, which can be 24V.

[0056] In this embodiment, the protection module 240 includes a second diode 680, a third diode 690, and a fuse 601. The cathode of the second diode 680 is connected to the output terminal 640 of the voltage isolation conversion circuit 520, and the anode of the second diode 680 is grounded. The anode of the third diode 690 is connected to the output terminal 640 of the voltage isolation conversion circuit 520, and the cathode of the third diode 690 is connected to the first terminal 602 of the fuse 601. The second terminal 603 of the fuse 601 is connected to the PWM signal output terminal 205 of the PWM output control circuit. The protection module 240 also includes a first capacitor 604, which is connected between the second terminal 603 of the fuse 601 and the anode of the second diode 680. The second diode 680 and the third diode 690 can both be SL14-A type diodes, without limitation. The fuse 601 can be a 0437.75WR fuse, without limitation. The first capacitor, 604, can be a 0.1uF / 50V 10% capacitor; there are no restrictions on this.

[0057] In this embodiment, a second Schmitt trigger is set in the isolation conversion module. The second Schmitt trigger can be used as a waveform shaping circuit to process the input PWM signal, making the waveform of the output PWM signal more accurate. A voltage isolation conversion circuit is set in the isolation conversion module to isolate the power supply, input terminal and output terminal from each other, and at the same time convert the input voltage signal into the voltage signal required by the output terminal. By setting a protection module, damage to important components in the circuit is avoided in the event of a circuit failure.

[0058] Figure 7 This is a schematic diagram of the PWM output control structure of a train automatic operation system provided in an embodiment of the present invention. Figure 7 As shown, the structure includes a PWM output control circuit 200, a control signal input terminal 203, a PWM signal input terminal 204, a control module 710, a first output terminal 720 of the control module, and a second output terminal 730 of the control module.

[0059] In this embodiment, the automatic train operation system is an automatic control subsystem that realizes automatic adjustment control of train speed, and its control signal can be in the form of a PWM signal. Applying the PWM signal output control circuit 200 from the above embodiment to the automatic train operation system can perform interference processing on the PWM signal output by the automatic train operation system, achieving precise control of the PWM signal output.

[0060] For example, the control module 710 can be a microcontroller, but this is not limited. The control signal input terminal 203 is connected to the I / O pin of the microcontroller (i.e., the first input terminal 720 of the control module 710), and the PWM signal input terminal 204 is connected to the PWM signal pin of the microcontroller (i.e., the second input terminal 730 of the control module 710). The I / O pin of the microcontroller can output a high level (i.e., digital logic "1") and a low level (i.e., digital logic "0"). The output pin of the microcontroller's PWM module is controlled by the microcontroller's internal program to output a PWM wave with a specified duty cycle and frequency.

[0061] The control signal input terminal 203 is connected to the microcontroller's I / O pins, receiving the high and low levels output by the microcontroller's I / O pins. The control signal input terminal 203 is also connected to the relay control module input terminal 250, transmitting the received high and low levels from the microcontroller's I / O pins to the relay control module 220 of the PWM output control circuit 200. The PWM signal input terminal 204 is connected to the microcontroller's PWM signal pins, receiving the PWM signals output by the microcontroller's PWM signal pins. The PWM signal input terminal 204 is also connected to the input terminal 280 of the isolation conversion module 230, transmitting the received PWM signals from the microcontroller's PWM signal pins to the isolation conversion module 230 of the PWM output control circuit 200.

[0062] In this embodiment, the PWM output control circuit is applied to the train operation system. The isolation conversion module in the PWM output control circuit can avoid the problem of PWM signal output errors caused by voltage amplitude increase due to external electromagnetic interference during train operation. At the same time, the relay control module in the PWM output control circuit controls the power-on and power-off of the relays, realizing safe and effective control of the PWM signal output and improving the safety of the train operation system.

[0063] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0064] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A PWM output control circuit, characterized by comprising: The relay, a relay control module, an isolation conversion module and a protection module are included. The input end of the relay control module is connected to the control signal input end of the PWM output control circuit, and the output end of the relay control module is connected to the control end of the relay. The relay includes a first common contact, a second common contact, a first contact and a second contact. The relay is used to control the first common contact and the first contact to be connected, and the second common contact and the second contact to be connected when powered on, and control the first common contact and the first contact to be disconnected, and the second common contact and the second contact to be disconnected when powered off.

2. The circuit of claim 1, wherein, The first contact and the second contact are respectively connected to the PWM signal output end and the reference ground output end of the PWM output control circuit. The input end of the isolation conversion module is connected to the PWM signal input end of the PWM output control circuit, the output end of the isolation conversion module is connected to the input end of the protection module, and the output end of the protection module is connected to the first common contact of the relay. The isolation conversion module is used to convert and output the PWM signal input by the input end through the protection module.

3. The circuit of claim 2, wherein, The relay control module includes a first Schmitt trigger and a power-on control circuit. The input end of the first Schmitt trigger is connected to the control signal input end, and the output end of the first Schmitt trigger is connected to the control end of the power-on control circuit. The input end of the power-on control circuit is connected to a first power supply, and the output end of the power-on control circuit is connected to the control end of the relay. The power-on control circuit includes a first resistor, a second resistor and a transistor.

4. The circuit of claim 3, wherein, The first pole of the transistor is connected to the first power supply as the input end of the power-on control circuit, the second pole of the transistor is connected to the first end of the coil of the relay as the output end of the power-on control circuit, and the second end of the coil of the relay is grounded.

5. The circuit of claim 1, wherein, One end of the first resistor is connected to the base of the transistor, and the second end of the first resistor is connected to the control end of the power-on control circuit. The second resistor is connected between the first pole and the base of the transistor. A first diode is also included, the cathode of the first diode is connected to the first end of the coil of the relay, and the anode of the first diode is connected to the second end of the coil of the relay.

6. The circuit of claim 5, wherein, The isolation conversion module includes a second Schmitt trigger and a voltage isolation conversion circuit. The input end of the second Schmitt trigger is connected to the PWM signal input end, the output end of the second Schmitt trigger is connected to the input end of the voltage isolation conversion circuit, and the output end of the voltage isolation conversion circuit is connected to the input end of the protection module. The voltage isolation conversion circuit is used to convert and transmit the PWM signal to the first common contact through the protection module. The voltage isolation conversion circuit includes an optoelectronic coupler.

7. The circuit of claim 5, wherein, A third resistor is further included, which is connected between the input end of the second Schmitt trigger and the ground end.

8. The circuit of claim 5, wherein, The protection module comprises a second diode, a third diode and a fuse; The cathode of the second diode is connected to the output end of the voltage isolation conversion circuit, and the anode of the second diode is grounded. The anode of the third diode is connected to the output end of the voltage isolation conversion circuit, the cathode of the third diode is connected to the first end of the fuse, and the second end of the fuse is connected to the PWM signal output end of the PWM output control circuit.

9. The circuit of claim 8, wherein, A first capacitor is further included, which is connected between the second end of the fuse and the anode of the second diode.

10. A train automatic operation system characterized by comprising: The PWM output control circuit comprises a control module and the PWM output control circuit according to any one of claims 1-9. The control signal input end is connected to the first output end of the control module, and the PWM signal input end is connected to the second output end of the control module. The PWM output control circuit is applied to the train operation system, is connected to the control module of the train operation system, and is used for controlling the PWM signal output by the control module, thereby improving the safety of the train operation system.

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