CN101470151B - CAN bus isolation circuit - Google Patents
CAN bus isolation circuit Download PDFInfo
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- CN101470151B CN101470151B CN2007100946314A CN200710094631A CN101470151B CN 101470151 B CN101470151 B CN 101470151B CN 2007100946314 A CN2007100946314 A CN 2007100946314A CN 200710094631 A CN200710094631 A CN 200710094631A CN 101470151 B CN101470151 B CN 101470151B
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Abstract
The invention discloses an CAN bus insulation circuit, comprising an CANH optical coupler insulator, an CANL optical coupler insulator and a power supply unit, wherein one end of the CAHN optical coupler insulator is connected with the CANH of a host computer CAN driver and the other end is connected with the CANH of a target computer CAN driver; one end of the CANL optical coupler insulator is connected with the CANL of the host computer CAN driver and the other end is connected with the CANL of the target computer CAN driver; the circuits of the CAHN optical coupler insulator, the CANL optical coupler insulator and the power supply unit at the host computer side share one grounding pole with the host computer CAN driver, while the circuits at the target side share one grounding pole with the target computer CAN driver; the CANH optical coupler insulator and the CANL optical coupler insulator adopt optical coupler to process the bidirectional transmission of CANH and CANL signals between the CAN drivers of the host computer and the target computer, and insulate the CAN buses of the host computer and the target computer. The CAN bus insulation circuit has simple circuit, reliability and low cost.
Description
Technical field
The present invention relates to the automobile bus communication technique field, particularly a kind of CAN bus isolation circuit.
Background technology
At present; Whole world total vehicle constantly increases, and electronic product proportion used in all kinds of automobiles is also increasingly high, and especially the In-vehicle networking communication part is more and more; A lot of car load networks adopt with CAN (controller local mostly; Controller Area Net) network is main, and LIN (local interconnect network), K-Line (K bus) are a kind of communication bus pattern of assisting, and increasing controller ECU becomes the node on the CAN network.Automotive electronics is from the consideration of itself security; Can do a large amount of product tests to these controller products; Like EMC (electromagnetic compatibility; Electro-MagneticCompatibility) test just comprises Electromagnetic Launching test, electromagnetic immunity test and ESD (static discharge, Electrostatic Discharge) test etc.And when doing this type of test; Need each controller under normal mode of operation, to test; This just needs to give to be measured to load some specific incentives signals (like the CAN signal); For avoiding influencing each other and disturbing of EUT to be measured (Equipment Under Test) and signal excitation source and monitoring client, need this two-part CAN bus is isolated, break off being electrically connected and test.
Carry out this CAN bus differential signal isolation scheme at present and roughly have two kinds: a kind of is the mode that adopts gateway, and the CAN signal is received from main frame, after microprocessor processes such as single-chip microcomputer, changes into the output of corresponding C AN signal again.This mode is isolated at Rx, Tx end, needs a microprocessor (two CAN control unit interfaces are arranged) and two CAN transceivers.This scheme needs programmed process, costs an arm and a leg, and ubiquity is poor.Another kind of with the Rx between two CAN transceivers, the Tx end is isolated, when a CAN transceiver when sending, control another one CAN transceiver through logical circuit, its receipts are not sent out, vice versa.This kind scheme still needs two extra CAN transceivers, also needs some DLC(digital logic circuit), complex structure, and price is more expensive.
Summary of the invention
The technical matters that the present invention will solve provides a kind of CAN bus isolation circuit, and its circuit is simple, reliable, cost is low.
For solving the problems of the technologies described above; The technical scheme that CAN bus isolation circuit of the present invention adopts; Comprise CANH optical coupling isolator, CANL optical coupling isolator and power supply unit; CANH optical coupling isolator one end is used for linking to each other with the CANH of host C AN driver; The other end is used for linking to each other with the CANH of target machine CAN driver; CANL optical coupling isolator one end is used for linking to each other with the CANL of host C AN driver, and the other end is used for linking to each other with the CANL of target machine CAN driver, and CANH optical coupling isolator, CANL optical coupling isolator and power supply unit host computer side circuit are with the shared ground of host C AN driver; The target machine lateral circuit is with the shared ground of target machine CAN driver, and CANH optical coupling isolator, CANL optical coupling isolator carry out main frame through optocoupler isolates with target machine CAN bus with the transmitted in both directions of the CANH between target machine CAN driver, CANL signal and to main frame.
CAN bus isolation circuit of the present invention utilizes optocoupler to carry out the CAN bus and isolates, and only needs 4 optocouplers to add power-switching circuit and can realize the isolation of CAN differential signal; Circuit is simple and reliable; Institute's device that utilizes is general and be easy to buying, is easy to make up, and overall cost is low.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the utility model is done further explain.
Fig. 1 is CAN CANH, CANL voltage level synoptic diagram when being dominance (1) level;
Fig. 2 is CAN CANH, CANL voltage level synoptic diagram when being recessive (0) level;
Fig. 3 is a CAN signal voltage level synoptic diagram;
Fig. 4 is the schematic diagram of CAN bus isolation circuit one embodiment of the present invention;
Fig. 5 is CANH optical coupling isolation circuit one an embodiment circuit diagram of the present invention;
Fig. 6 is CANL optical coupling isolation circuit one an embodiment circuit diagram of the present invention.
Embodiment
Like Fig. 1, Fig. 2, shown in Figure 3, the voltage span during the dominance level (Dominant Level) of common CANH is 2.75～4.5V, and the voltage span during recessive level (Recessive Level) is 2～3V; Voltage span during the dominance level of CANL is 0.5～2.25V, and the voltage span during recessive level is 2～3V; Voltage span when the CAN signal is the dominance level is 1.5～3V, and the voltage span when the CAN signal is recessive level is-0.5～50mV.
One embodiment of CAN bus isolation circuit of the present invention is as shown in Figure 4; Comprise CANH optical coupling isolator, CANL optical coupling isolator and power supply unit; The CANH that CANH optical coupling isolator one end is used for same main frame (HOST) CAN driver A links to each other; Continuous CANL optical coupling isolator one end of CANH that the other end is used for same target machine (TARGET) CAN driver B is used for linking to each other with the CANL of host C AN driver A; The other end is used for linking to each other with the CANL of target machine CAN driver B; CANH optical coupling isolator CANL optical coupling isolator and power supply unit host computer side circuit are with the shared ground GRAND A of host C AN driver A; The target machine lateral circuit is with the shared ground GRAND B of target machine CAN driver B, and CANH optical coupling isolator, CANL optical coupling isolator carry out main frame through optocoupler isolates with target machine CAN bus with the transmitted in both directions of the CANH between target machine CAN driver, CANL signal and to main frame.
One embodiment of the invention, like Fig. 5, shown in Figure 6, the light-coupled isolation device is selected rapid light coupling TLP559 for use.
The CANH optical coupling isolator is as shown in Figure 5, power supply unit output provide draw on the host side of constant voltage source: CANH level V1_AH (+4V), the host side optical coupling secondary edges level V2_AH of CANH (+5V), the host side optocoupler master limit level V3_AH of CANH (+5V), the host side optocoupler ground level V4_AH of CANH (+2.5V), draw on the target machine end of CANH level V1_BH (+4V), the target machine end optical coupling secondary edges level V2_BH of CANH (+5V), the target machine end optocoupler master limit level V3_BH of CANH (+5V), the target machine end optocoupler ground level V4_BH of CANH (+2.5V).
The circuit of the host side of CANH optical coupling isolator connects as follows: the negative terminal of the light emitting diode on the first optocoupler ISO1 master limit connects the emitter of positive-negative-positive the first transistor Q1; The base stage of the NPN transistor of the second optocoupler ISO2 secondary connects the anode of the second optocoupler ISO2 secondary light sensitive diode; The anode of the light emitting diode on the first optocoupler ISO1 master limit meets the host side optocoupler master limit level V3_AH of CANH through host side current-limiting resistance R2 (100 ohm); The base stage of the first transistor Q1 meets the CANH signal output part HOST_IN_OUTH of host C AN driver; And connect the collector of the NPN transistor of the second optocoupler ISO2 secondary through host side dividing potential drop filter resistance R3 (2000 ohm); The collector of the NPN transistor of the second optocoupler ISO2 secondary connects through host side pull-up resistor R4 (10000 ohm) on the host side of CANH and draws level V1_AH; The emitter of the NPN transistor of the collector of the first transistor Q1 and the second optocoupler ISO2 secondary is with the host side optocoupler ground level V4_AH that meets CANH, and the negative terminal of the second optocoupler ISO2 secondary light sensitive diode meets the host side optical coupling secondary edges level V2_AH of CANH.
The circuit of the target machine end of CANH optical coupling isolator connects as follows: the negative terminal of the light emitting diode on the second optocoupler ISO2 master limit connects the emitter of positive-negative-positive transistor seconds Q2; The base stage of the NPN transistor of the first optocoupler ISO1 secondary connects the anode of the first optocoupler ISO1 secondary light sensitive diode; The anode of the light emitting diode on the second optocoupler ISO2 master limit meets the target machine end optocoupler master limit level V3_BH of CANH through target machine end current-limiting resistance R5 (100 ohm); The base stage of transistor seconds Q2 meets the CANH signal output part TARGET_IN_OUTH of target machine CAN driver; And connect the collector of the NPN transistor of the first optocoupler ISO1 secondary through target machine end dividing potential drop filter resistance R6 (2000 ohm); The collector of the NPN transistor of the first optocoupler ISO1 secondary connects through target machine end pull-up resistor R1 (10000 ohm) on the target machine end of CANH and draws level V1_BH; The emitter of the NPN transistor of the collector of transistor seconds Q2 and the first optocoupler ISO1 secondary is with the target machine end optocoupler ground level V4_BH that meets CANH, and the negative terminal of the first optocoupler ISO1 secondary light sensitive diode meets the target machine end optical coupling secondary edges level V2_BH of CANH.
The CANL optical coupling isolator is as shown in Figure 6; Its circuit connecting mode is consistent with the CANH optical coupling isolator; But power supply unit offers magnitude of voltage of each end and adapts with the requirement of CANL signal, and voltage of each end of circuit is respectively: draw on the host side of CANL level V1_AL (+3V), the host side optical coupling secondary edges level V2_AL of CANL (+5V), the host side optocoupler master limit level V3_AL of CANL (+4V), the host side optocoupler ground level V4_AL of CANL (+1.5V), draw on the target machine end of CANL level V1_BL (+3V), the target machine end optical coupling secondary edges level V2_BL of CANL (+5V), the target machine end optocoupler master limit level V3_BL of CANL (+4V), the target machine end optocoupler ground level V4_BL of CANL (+1.5V); The base stage of the first transistor Q1 meets the CANL signal output part HOST_IN_OUTL of main frame (HOST) CAN driver, and the base stage of transistor seconds Q2 meets the CANL signal output part TARGET_IN_OUTL of target machine (TARGET) CAN driver.
The shared ground GRAND A of CANH optical coupling isolator, CANL optical coupling isolator and the same main frame of power supply unit main frame (HOST) lateral circuit (HOST) CAN driver, the shared ground GRAND B of the same target machine of target machine (TARGET) side (TARGET) CAN driver.The voltage level current potential of host computer side is relative transmitting terminal 0V earth potential in the circuit, and the voltage level current potential of target pusher side is relative destination end 0V earth potential.
Below to draw level current potential V1_AH, V1_BH to be+4V on the CANH; The optocoupler ground level current potential V4_AH of CANH, V4_BH are+2.5V; Draw level current potential V1_AL, V1_BL to be+3V on the CANL; The optocoupler ground level current potential V4_AL of CANL, V4_BL for+1.5V is an example, and is adjustable in certain voltage range, describes CAN bus isolation circuit principle of work of the present invention in detail.
The CANH optical coupling isolation circuit:
One, A district main frame (HOST) sends signal, B district target machine (TARGET) acknowledge(ment) signal
1, sends signal " 1 ": when the CAN network is logical one; CANH is relative level 3.5V; Be that level on the CANH signal output part HOST_IN_OUTH of host C AN driver is 3.5V; The host side optocoupler master limit level V3_A of CANH and the CANH signal output part HOST_IN_OUTH voltage difference of host C AN driver are 5V-3.5V=1.5V at this moment; Because the existence of host side current-limiting resistance R2, the first optocoupler ISO1 drive current is approximately (1.5-0.7-0.7)/100=1mA, and this electric current can't drive the light emitting diode on the first optocoupler ISO1 master limit; This moment, the NPN transistor of the first optocoupler ISO1 secondary was a cut-off state; Transistor seconds Q2 ends, and the level of the CANH signal output part TARGET_IN_OUTH of target machine CAN driver at 3.5V～4V, is realized the acceptance of target machine end level"1" through level equalization after drawing level V1_BH and target machine end dividing potential drop filter resistance R6 on the target machine end that draws CANH on the target machine end pull-up resistor R1.
2, send signal " 0 ": when the CAN network is logical zero; CANH is relative level 2.5V; Be that level on the CANH signal output part HOST_IN_OUTH of host C AN driver is 2.5V; The host side optocoupler master limit level V3_AH of CANH and the CANH signal output part HOST_IN_OUTH voltage difference of host C AN driver are 5V-2.5V=2.5V at this moment, because the existence of host side current-limiting resistance R2, the first optocoupler ISO1 drive current is approximately (2.5-0.7-0.7)/100=11mA; This voltage can drive the light emitting diode on the first optocoupler ISO1 master limit; The NPN transistor of the first optocoupler ISO1 secondary is a conducting state, transistor seconds Q2 conducting, thereby the level of the CANH signal output part TARGET_IN_OUTH of target machine CAN driver is by clamped target machine end optocoupler ground level V4_BH at CANH.Because target machine end pull-up resistor R1 is greater than target machine end dividing potential drop filter resistance R6, this level equalization is realized the acceptance of target machine end level "0" about 2.5V.
Two, B district target machine sends signal, A district main frame acknowledge(ment) signal
1, sends signal " 1 ": when the CAN network is logical one; CANH is relative level 3.5V; The CANH signal output part TARGET_IN_OUTH level that is target machine CAN driver is 3.5V; The target machine end optocoupler master limit level V3_BH of CANH and the CANH signal output part TARGET_IN_OUTH voltage difference of target machine CAN driver are 5V-3.5V=1.5V at this moment; Because the existence of target machine end current-limiting resistance R5; The second optocoupler ISO2 drive current is approximately (1.5-0.7-0.7)/100=1mA, and this electric current can't drive the light emitting diode on the second optocoupler ISO2 master limit, and this moment, the NPN transistor of the second optocoupler ISO2 secondary was a cut-off state; The level of the CANH signal output part HOST_IN_OUTH of host C AN driver through draw on the host side of drawing CANH on the host side pull-up resistor R4 level V1_AH (+4V) with host side dividing potential drop filter resistance R3 after level equalization at 3.5V～4V, realize the acceptance of host side level"1".
2, send signal " 0 ": when the CAN network is logical zero; CANH is relative level 2.5V; The CANH signal output part TARGET_IN_OUTH level that is target machine CAN driver is 2.5V; The target machine end optocoupler master limit level V3_BH of CANH and the CANH signal output part TARGET_IN_OUTH voltage difference of target machine CAN driver are 5V-2.5V=2.5V at this moment; Because the existence of target machine end current-limiting resistance R5, the second optocoupler ISO2 drive current is approximately (2.5-0.7-0.7)/100=11mA, and this voltage can drive the light emitting diode on the second optocoupler ISO2 master limit; This moment the second optocoupler ISO2 secondary NPN transistor be conducting state, thereby the level of the CANH signal output part HOST_IN_OUTH of host C AN driver by clamped host side optocoupler ground level V4_AH at CANH (+2.5V).Because host side pull-up resistor R4 is greater than host side dividing potential drop filter resistance R3, this level equalization is realized the acceptance of host side level "0" about 2.5V.
Because photoelectricity transmission speed is very fast, the transmission again and the transmission delay of CANH transmission signal and feedback signal, reflected signal can be ignored, and realize the transmitted in both directions of host side and target machine end CANH signal through the first transistor Q1, transistor seconds Q2.
The CANL optical coupling isolation circuit:
One, A district main frame sends signal, B district target machine acknowledge(ment) signal
1, sends signal " 1 ": when the CAN network is logical one; CANL is relative level 1.5V; The CANL signal output part HOST_IN_OUTL level that is host C AN driver is 1.5V; The host side optocoupler master limit level V3_AL of CANL and the CANL signal output part HOST_IN_OUTL voltage difference of host C AN driver are 4V-1.5V=2.5V at this moment; Because the existence of host side current-limiting resistance R2, the first optocoupler ISO1 drive current is approximately (2.5-0.7-0.7)/100=11mA, and this voltage can drive the light emitting diode on the first optocoupler ISO1 master limit; This moment the first optocoupler ISO1 secondary NPN transistor be conducting state, thereby the level of the CANL signal output part TARGET_IN_OUTL of target machine CAN driver by clamped target machine end optocoupler ground level V4_BL at CANL (+1.5V).Because target machine end pull-up resistor R1 is greater than target machine end dividing potential drop filter resistance R6, this level equalization is realized the acceptance of target machine end level"1" about 1.5V.
2, send signal " 0 ": when the CAN network is logical zero; CANL is relative level 2.5V; The CANL signal output part HOST_IN_OUTL level that is host C AN driver is 2.5V; The host side optocoupler master limit level V3_AL of CANL and the CANL signal output part HOST_IN_OUTL voltage difference of host C AN driver are 4V-2.5V=1.5V at this moment; Because the existence of host side current-limiting resistance R2; The first optocoupler ISO1 drive current is approximately (1.5-0.7-0.7)/100=1mA, and this electric current can't drive the light emitting diode on the first optocoupler ISO1 master limit, and this moment, the NPN transistor of the first optocoupler ISO1 secondary was a cut-off state; The level of the CANL signal output part TARGET_IN_OUTL of target machine CAN driver through on draw draw on the target machine end that draws CANL on the target machine end resistance R 1 level V1_BL (+3V) with target machine end dividing potential drop filter resistance R6 after level equalization at 2.5V～3V, realize the acceptance of target machine end level "0".
Two, B district target machine sends signal, A district main frame acknowledge(ment) signal
1, sends signal " 1 ": when the CAN network is logical one; CANL is relative level 1.5V; The level that is the CANL signal output part TARGET_IN_OUTL of CAN driver is 1.5V; The voltage difference of the CANL signal output part TARGET_IN_OUTL of the target machine end optocoupler master limit level V3_BL of CANL and CAN driver is 4V-1.5V=2.5V at this moment; Because the existence of target machine current-limiting resistance R5, the drive current of the second optocoupler ISO2 is approximately (2.5-0.7-0.7)/100=11mA, and this voltage can drive the light emitting diode on the second optocoupler ISO2 master limit; This moment the second optocoupler ISO2 secondary NPN transistor be conducting state, thereby the level of the CANL signal output part HOST_IN_OUTL of CAN driver by clamped host side optocoupler ground level V4_AL at CANL (+1.5V).Because host side pull-up resistor R4 is greater than host side dividing potential drop filter resistance R3, this level equalization is realized the acceptance of host side end level"1" about 1.5V.
2, send signal " 0 ": when the CAN network is logical zero; CANL is relative level 3.5V; The level that is the CANL signal output part TARGET_IN_OUTL of CAN driver is 3.5V; The target machine end optocoupler master limit level V3_BL of CANL and the CANL signal output part TARGET_IN_OUTL voltage difference of CAN driver are 5V-3.5V=1.5V at this moment; Because the existence of target machine end current-limiting resistance R5; The second optocoupler ISO2 drive current is approximately (1.5-0.7-0.7)/100=1mA, and this electric current can't drive the light emitting diode on the second optocoupler ISO2 master limit, and this moment, the NPN transistor of the second optocoupler ISO2 secondary was a cut-off state; The level of the CANL signal output part HOST_IN_OUTL of CAN driver at 2.5V～3V, is realized the acceptance of host side level "0" through level equalization after drawing level V1_AL and host side dividing potential drop filter resistance R3 on the host side of drawing CANL on the host side pull-up resistor R4.
Because photoelectricity transmission speed is very fast, the transmission again and the transmission delay of CANL transmission signal and feedback signal, reflected signal can be ignored, and realize the transmitted in both directions of host side and target machine end CANL signal through the first transistor Q1, transistor seconds Q2.
CAN bus isolation circuit of the present invention utilizes optocoupler to carry out the CAN bus and isolates, and circuit is simple and reliable, and institute's device that utilizes is general and be easy to buying, and overall cost is low.
Through embodiment and specific embodiment technical scheme of the present invention is described above; Just for describing convenient the setting, the CAN controller that the CAN bus isolation circuit is connected does not have the branch of actual primary and secondary to the appellation of said main frame (HOST), target machine (TARGET).Invention has been described with preferred embodiment above, but the those of ordinary skill of skilled should be made various conversion that are equal to and change on the basis of foregoing.Therefore protection scope of the present invention should not be limited to the form of said embodiment, and should be limited claims.
Claims (5)
1. CAN bus isolation circuit; It is characterized in that; Comprise CANH optical coupling isolator, CANL optical coupling isolator and power supply unit; CANH optical coupling isolator one end is used for linking to each other with the CANH of host C AN driver, and the other end is used for linking to each other with the CANH of target machine CAN driver, and CANL optical coupling isolator one end is used for linking to each other with the CANL of host C AN driver; The other end is used for linking to each other with the CANL of target machine CAN driver; CANH optical coupling isolator, CANL optical coupling isolator and power supply unit host computer side circuit are with the shared ground of host C AN driver, and the target machine lateral circuit is with the shared ground of target machine CAN driver, and CANH optical coupling isolator, CANL optical coupling isolator carry out main frame through optocoupler isolates with target machine CAN bus with the transmitted in both directions of the CANH between target machine CAN driver, CANL signal and to main frame.
2. CAN bus isolation circuit according to claim 1 is characterized in that:
The circuit of the host computer side of CANH, CANL optical coupling isolator is: the negative terminal of the light emitting diode on the first optocoupler master limit connects the emitter of positive-negative-positive the first transistor; The base stage of the NPN transistor of second optical coupling secondary edges connects the anode of the second optical coupling secondary edges light sensitive diode; The anode of the light emitting diode on the first optocoupler master limit connects host side optocoupler master limit level through the host side current-limiting resistance; The base stage of the first transistor connects the signal output part of host C AN driver; And connect the collector of the NPN transistor of second optical coupling secondary edges through host side dividing potential drop filter resistance; The collector of the NPN transistor of second optical coupling secondary edges connects through the host side pull-up resistor and draws level on the host side; The emitter of the NPN transistor of the collector of the first transistor and second optical coupling secondary edges is with connecing host side optocoupler ground level, and the negative terminal of the second optical coupling secondary edges light sensitive diode connects host side optical coupling secondary edges level; The circuit of the target pusher side of optical coupling isolator is: the negative terminal of the light emitting diode on the second optocoupler master limit connects the emitter of positive-negative-positive transistor seconds; The base stage of the NPN transistor of first optical coupling secondary edges connects the anode of the first optical coupling secondary edges light sensitive diode; The anode of the light emitting diode on the second optocoupler master limit connects target machine end optocoupler master limit level through target machine end current-limiting resistance; The base stage of transistor seconds connects the signal output part of target machine CAN driver; And connect the collector of the NPN transistor of first optical coupling secondary edges through target machine end dividing potential drop filter resistance; The collector of the NPN transistor of first optical coupling secondary edges connects on the target machine end through target machine end pull-up resistor and draws level; The emitter of the NPN transistor of the collector of transistor seconds and first optical coupling secondary edges is with connecing target machine end optocoupler ground level, and the negative terminal of the first optical coupling secondary edges light sensitive diode connects target machine end optical coupling secondary edges level;
Power supply unit offers respectively to draw on the host side of CANH, CANL optical coupling isolator and draws level, target machine end optical coupling secondary edges level, target machine end optocoupler master limit level, target machine end optocoupler ground level corresponding work voltage on level, host side optical coupling secondary edges level, host side optocoupler master limit level, host side optocoupler ground level, the target machine end; The CANH of the signal output part of host C AN driver, CANL signal connect the base stage of CANH, CANL optical coupling isolator the first transistor respectively, and the CANH of the signal output part of target machine CAN driver, CANL signal connect the base stage of CANH, CANL optical coupling isolator transistor seconds respectively.
3. CAN bus isolation circuit according to claim 2 is characterized in that, the host side pull-up resistor is greater than host side dividing potential drop filter resistance, and target machine end pull-up resistor is greater than target machine end dividing potential drop filter resistance.
4. according to claim 2 or 3 described CAN bus isolation circuits; It is characterized in that, draw on the host side of the CANH optical coupling isolator that power supply unit provides level be+4V, host side optical coupling secondary edges level for+5V, host side optocoupler master limit level for+5V, host side optocoupler ground level for draw on+2.5V, the target machine end level be+4V, target machine end optical coupling secondary edges level be+2.5V for+5V, target machine end optocoupler master limit level for+5V, target machine end optocoupler ground level; Draw on the host side of CANL optical coupling isolator level be+3V, host side optical coupling secondary edges level for+5V, host side optocoupler master limit level for+4V, host side optocoupler ground level for draw on+1.5V, the target machine end level be+3V, target machine end optical coupling secondary edges level be+1.5V for+5V, target machine end optocoupler master limit level for+4V, target machine end optocoupler ground level.
5. according to claim 2 or 3 described CAN bus isolation circuits; It is characterized in that; Host side and target machine end current-limiting resistance are 100 ohm, and host side and target machine end pull-up resistor are 10000 ohm, and host side and target machine end dividing potential drop filter resistance are 2000 ohm.
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| CN2007100946314A CN101470151B (en) | 2007-12-26 | 2007-12-26 | CAN bus isolation circuit |
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| CN2007100946314A CN101470151B (en) | 2007-12-26 | 2007-12-26 | CAN bus isolation circuit |
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| CN102857208B (en) * | 2012-08-02 | 2015-04-15 | 北京交通大学 | High-speed bidirectional communication isolating circuit based on dual optocouplers |
| CN104460466B (en) * | 2014-12-25 | 2017-07-04 | 李钢 | A kind of CAN isolation circuits |
| CN105376127B (en) * | 2015-10-09 | 2018-10-16 | 深圳市科陆智慧工业有限公司 | A kind of circuit system for the noise margin improving CAN bus signal |
| CN108173543A (en) * | 2017-12-26 | 2018-06-15 | 北京航天测控技术有限公司 | A kind of two-way isolation circuit of single-wire communication bus |
| CN108132665A (en) * | 2017-12-27 | 2018-06-08 | 威马智慧出行科技（上海）有限公司 | For the Vehicular communication system and electric vehicle of electric vehicle |
| EP3700137B1 (en) * | 2019-02-22 | 2023-08-02 | Volvo Car Corporation | Monitoring can nodes |
| US11310072B2 (en) * | 2019-12-03 | 2022-04-19 | Texas Instruments Incorporated | Bus transceiver with ring suppression |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6233509B1 (en) * | 1995-08-10 | 2001-05-15 | Genrad Limited | Electronic diagnostic system |
| CN1984154A (en) * | 2005-12-14 | 2007-06-20 | 中国科学院沈阳自动化研究所 | On-site bus interface device |
| CN200993741Y (en) * | 2006-12-13 | 2007-12-19 | 北京交通大学 | Hybrid power electric automobile matching demarcation device based on serial communication |
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| CN101470151A (en) | 2009-07-01 |
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