CN205232203U - High -power CAN bus transmitting circuit - Google Patents
High -power CAN bus transmitting circuit Download PDFInfo
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- CN205232203U CN205232203U CN201520880660.3U CN201520880660U CN205232203U CN 205232203 U CN205232203 U CN 205232203U CN 201520880660 U CN201520880660 U CN 201520880660U CN 205232203 U CN205232203 U CN 205232203U
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Abstract
The utility model provides a high -power CAN bus transmitting circuit, sends voltage and sends the electric current through the improvement, extension CAN bus transmission distance. This high -power CAN bus transmitting circuit comprises buffer, phase inverter, current -limiting circuit, H drive circuit and L drive circuit. Incoming signal T delivers to the input of buffer and phase inverter respectively, and the H drive circuit input is delivered to in the output of buffer, and the L drive circuit input is delivered to in the output of phase inverter, and two current -limiting circuits are established ties respectively in H drive circuit and L drive circuit's return circuit, H drive circuit and L drive circuit's output connection CAN bus.
Description
Technical field
Electronic information---communication---transmission of digital information.
Background technology
ISO11898-2 specification (the most frequently used CAN specification) uses twisted-pair feeder as transmission medium, and the maximum distance of transmission is ten thousand metres.In fact the transmission range of CAN affects by several factors, as cable quality, transmission rate, environmental factor etc., is generally difficult to reach distance so far away.The terminal resistance at CAN two ends and transmission line all can consume the energy that a lot of transmitting terminal sends, and the interference signal around transmission line also can affect the transmission of normal signal.
The factor affecting CAN transmission range mainly contains three kinds.The first factor is threshold value.Signal is after long range propagation, and when arriving receiving node, voltage amplitude may not reach the threshold value of receiver, i.e. the threshold voltage of CAN receiver, and at this time signal will be left in the basket.The output voltage of common CAN transceiver is generally about 2.5V, and when the resistivity of transmission line is higher or transmission line is longer, when signal arrives receiving node, signal voltage lower than CAN receiver threshold value, can will cause the loss of signal like this.
The second factor affecting CAN transmission range is interference.All signals that so-called interference refers to beyond useful signal, these external signals can seal among useful signal, and these signals sealed in can persistent accumulation.Along with the superposition of interference signal, not only the shape of useful signal is changed, and even can be flooded by noise gradually.In general, circuit is longer, and the interference sealed in is more; Transmission line surrounding interferers is more, and transmission range is shorter.
The third factor affecting CAN transmission range is the signal skew that causes of the equivalent parameters of transmission line and delay.The equivalent parameters of one section of transmission line comprises resistance, electric capacity and inductance, and wherein electric capacity and inductance are the principal elements causing signal skew and delay.If apply signal in one end of one section of transmission line, due to the impact of transmission line selfcapacity and inductance, the signal occurred at the other end will produce distortion and postpone, and the signal causing receiving can be produced larger change by this compared with primary signal, cannot rediscover signal.Transmission line is longer, this distortion and postpone more serious.
The purpose of this utility model is exactly for this several situation, by improving the voltage and current of output signal, extends CAN transmission range.
Summary of the invention
For the first situation affecting CAN transmission range, need to improve the voltage amplitude sending signal.When the output voltage of transmitting terminal increases, through transmission line, when arriving receiving terminal, the voltage of twisted-pair feeder line-to-line also can correspondingly improve, as long as reliably can cross the threshold voltage of receiver, just correctly can receive data.
For the second situation, solution has several: the voltage and current when internal resistance of minimizing transmitter, the resistance reducing terminal resistance, raising send, use filter etc.This several method is damped electron noise, makes it not affect transfer of data.Wherein, reduce the resistance of terminal resistance and inadvisable, otherwise do not mate with the characteristic impedance of bus.Filter does not then possess generality, is only applicable to the electronic noise of specific frequency spectrum.So really feasible method namely reduces transmitter internal resistance and improves transmission voltage and current.Comparatively speaking, transmission voltage and current is improved easier.
For the third situation, most suitable solution reduces transmission rate exactly, other method DeGrain.
As can be seen from analysis above, when needing the transmission range extending CAN, if the problem first run into is the first situation, the output voltage of transmitter will be improved.If the problem first run into is the second situation, preferably improve output voltage and the output current of transmitter simultaneously.If the problem first run into is the third situation, then transmission rate should be reduced.
In sum, improve output voltage and the output current of CAN transmitter, the transmission range of CAN can be extended.
Improve the transmission voltage and current of CAN transmitter, common CAN transmitter can not be used, a brand-new CAN transmitter must be designed.Except output voltage and output current, this CAN transmitter must observe CAN specification as far as possible, otherwise there will be various problem with during standard CAN devices communicating.
In CAN specification, CAN is made up of CANH and CANL two lines.Countless according to output or export in " 1 ", CANH and CANL presents vacant state; In time exporting " 0 ", CANH pull-up, CANL is drop-down.
Clearly, CANH and CANL requires out to leak and exports, and the field effect transistor source electrode exporting CANH connects positive source, and the field effect transistor source electrode exporting CANL connects power cathode.
In order to regulation output electric current, CANH and CANL must have current regulating device.The simplest scheme uses current-limiting resistance to carry out regulation output electric current, can speed-up capacitor compensating signal edge in parallel on this resistance.More complex scheme uses constant current device, and this is very favourable for the occasion that interference ratio is more serious.
CANH and CANL is normally worked, suitable driving must be applied to these two field effect transistor.When output " 0 ", CANH field effect transistor must apply low level and drive, and makes it saturation conduction; CANL field effect transistor must apply high level simultaneously, makes it saturation conduction.When output " 1 ", these two field effect transistor all must remain off.
In order to realize the driving of field effect transistor, between transmission signal and CANH field effect transistor, a buffer is set, between transmission signal and CANL field effect transistor, an inverter is set, make the driving needs not only meeting field effect transistor like this, and make the conducting simultaneously of two field effect transistor, end simultaneously.
Sum up [0012] ~ [0017] partial content, have devised high-power CAN transtation mission circuit as shown in Figure 1, namely the technical solution of the utility model.This high-power CAN transtation mission circuit comprises buffer, inverter, current-limiting circuit, H drive circuit and L drive circuit, and the input signal of high-power CAN transtation mission circuit is T, outputs signal as H and L.Input signal T delivers to the input of buffer and inverter respectively, H drive circuit input is delivered in the output of buffer, L drive circuit input is delivered in the output of inverter, two current-limiting circuits are series in the loop of H drive circuit and L drive circuit respectively, the output of H drive circuit is the output of H, L drive circuit is L.
The beneficial effects of the utility model improve CAN transmission range.
Accompanying drawing explanation
Fig. 1 is high-power CAN transtation mission circuit schematic diagram.In figure, signal T is the signal for being sent to CAN, comes from user logic treatment circuit signal.H and L is connected respectively to CANH and CANL of CAN.As T=1, field effect transistor T1 ends, H signal floating; Field effect transistor T2 ends, L signal floating.As T=0, field effect transistor T1 saturation conduction, H signal is pulled upward to power supply, presents high level; Field effect transistor T2 saturation conduction, L signal pulls down to ground wire, presents low level.Now, larger voltage difference is had between H signal and L signal.
Embodiment
The utility model comprises buffer, inverter, current-limiting circuit, H drive circuit and L drive circuit, and input signal is T, outputs signal as H and L.Input signal T delivers to the input of buffer and inverter respectively, H drive circuit input is delivered in the output of buffer, L drive circuit input is delivered in the output of inverter, two current-limiting circuits are series in the loop of H drive circuit and L drive circuit respectively, the output of H drive circuit is the output of H, L drive circuit is L.Further, H drive circuit be source electrode connect positive source open leakage output form, L drive circuit be source electrode connect power cathode open leakage output form; Current-limiting circuit comprises H current-limiting circuit and L current-limiting circuit, wherein H current-limiting circuit is between the drain electrode and H signal of H drive circuit or between the source electrode of H drive circuit and positive source, and L current-limiting circuit is between the drain electrode and L signal of L drive circuit or between the source electrode of L drive circuit and power cathode; Current-limiting circuit can use resistance or constant-current circuit, if use resistance, and can speed-up capacitor in parallel on it.
Claims (4)
1. a high-power CAN transtation mission circuit, comprises buffer, inverter, current-limiting circuit, H drive circuit and L drive circuit, and the input signal of high-power CAN transtation mission circuit is T, outputs signal as H and L; It is characterized in that: input signal T delivers to the input of buffer and inverter respectively, H drive circuit input is delivered in the output of buffer, L drive circuit input is delivered in the output of inverter, two current-limiting circuits are series in the loop of H drive circuit and L drive circuit respectively, the output of H drive circuit is the output of H, L drive circuit is L.
2. high-power CAN transtation mission circuit according to claim 1, is characterized in that: H drive circuit be source electrode connect positive source open leakage output form, L drive circuit be source electrode connect power cathode open leakage output form.
3. high-power CAN transtation mission circuit according to claim 1, it is characterized in that: described current-limiting circuit comprises H current-limiting circuit and L current-limiting circuit, wherein H current-limiting circuit is between the drain electrode and H signal of H drive circuit or between the source electrode of H drive circuit and positive source, and L current-limiting circuit is between the drain electrode and L signal of L drive circuit or between the source electrode of L drive circuit and power cathode.
4., according to claim 1 or high-power CAN transtation mission circuit according to claim 3, it is characterized in that: described current-limiting circuit can use resistance or constant-current circuit, if use resistance, can speed-up capacitor in parallel on it.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520880660.3U CN205232203U (en) | 2015-11-08 | 2015-11-08 | High -power CAN bus transmitting circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520880660.3U CN205232203U (en) | 2015-11-08 | 2015-11-08 | High -power CAN bus transmitting circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN205232203U true CN205232203U (en) | 2016-05-11 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201520880660.3U Expired - Fee Related CN205232203U (en) | 2015-11-08 | 2015-11-08 | High -power CAN bus transmitting circuit |
Country Status (1)
| Country | Link |
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| CN (1) | CN205232203U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107294409A (en) * | 2017-07-26 | 2017-10-24 | 江西联智集成电路有限公司 | Active rectifier |
| CN114697157A (en) * | 2022-03-18 | 2022-07-01 | 深圳市麦格米特焊接技术有限公司 | CAN circuit and CAN communication system |
-
2015
- 2015-11-08 CN CN201520880660.3U patent/CN205232203U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107294409A (en) * | 2017-07-26 | 2017-10-24 | 江西联智集成电路有限公司 | Active rectifier |
| CN114697157A (en) * | 2022-03-18 | 2022-07-01 | 深圳市麦格米特焊接技术有限公司 | CAN circuit and CAN communication system |
| CN114697157B (en) * | 2022-03-18 | 2023-10-17 | 深圳市麦格米特焊接技术有限公司 | CAN circuit and CAN communication system |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20160511 Termination date: 20161108 |
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| CF01 | Termination of patent right due to non-payment of annual fee |