WO2020097797A1 - 一种双向车载充电机绝缘检测电路及其检测方法 - Google Patents

一种双向车载充电机绝缘检测电路及其检测方法 Download PDF

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WO2020097797A1
WO2020097797A1 PCT/CN2018/115259 CN2018115259W WO2020097797A1 WO 2020097797 A1 WO2020097797 A1 WO 2020097797A1 CN 2018115259 W CN2018115259 W CN 2018115259W WO 2020097797 A1 WO2020097797 A1 WO 2020097797A1
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circuit
voltage
output
resistor
sampling
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PCT/CN2018/115259
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English (en)
French (fr)
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刘钧
冯颖盈
徐金柱
张远昭
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深圳威迈斯新能源股份有限公司
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Priority to PCT/CN2018/115259 priority Critical patent/WO2020097797A1/zh
Priority to EP18939932.2A priority patent/EP3879285B1/en
Priority to US16/857,482 priority patent/US11604217B2/en
Publication of WO2020097797A1 publication Critical patent/WO2020097797A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/005—Testing of electric installations on transport means
    • G01R31/006—Testing of electric installations on transport means on road vehicles, e.g. automobiles or trucks
    • G01R31/007—Testing of electric installations on transport means on road vehicles, e.g. automobiles or trucks using microprocessors or computers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
    • G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40—Testing power supplies
    • G01R31/42—AC power supplies

Definitions

  • the invention relates to charging equipment, in particular to a bidirectional vehicle-mounted charger insulation detection circuit and a detection method thereof.
  • the car charger is a very important component in electric vehicles. The quality of the car charger directly affects the safety and reliability of the vehicle. The insulation of the live wire and ground wire of the car charger is also related to the performance of the whole machine. If the insulation of the live wire and ground wire fails, it is easy to cause damage to components and even electric shock. In the past, the detection method was to use an instrument to test after a power failure. It has the defects of cumbersome operation and cannot be monitored in real time.
  • the present invention is to solve the above problems of the prior art, and proposes a detection circuit and a detection method for detecting whether there is an insulation failure between an AC output of a vehicle-mounted charger operating in a pure inverter mode and a vehicle body.
  • the technical solution proposed by the present invention is to design a two-way vehicle charger insulation detection circuit, including an inverter circuit, a first Y capacitor connected between the output live wire and the ground wire of the inverter circuit, connected in the reverse
  • the second Y capacitor between the neutral line and the ground line of the transformer circuit which also includes a live line sampling circuit and a zero line sampling circuit corresponding to the output live line and the output neutral line of the inverter circuit, connecting the live line sampling circuit and the zero line sampling circuit
  • a controller wherein the live line sampling circuit and the neutral line sampling circuit respectively output sampling voltages, and the controller judges the insulation state of the bidirectional vehicle-mounted charger according to the two sampling voltages.
  • a summing circuit is provided between the controller and the FireWire sampling circuit and the Neutral sampling circuit, the summing circuit performs summing processing on the two sampled voltages to obtain a summing voltage, and transmits the summing voltage To the controller, the controller judges the insulation state of the bidirectional on-board charger based on the added voltage.
  • the live line sampling circuit and the neutral line sampling circuit have the same circuit structure, and all include a voltage dividing circuit, a bias power supply, a negative voltage bias circuit, and an impedance matching circuit, wherein the voltage dividing circuit is connected to the output live wire or output neutral wire To reduce the voltage proportionally and output the divided voltage; the negative voltage bias circuit is connected between the output terminal of the voltage dividing circuit and the bias power supply to bias the divided voltage; the impedance matching circuit is connected The output terminal of the voltage dividing circuit performs impedance matching and outputs the sampling voltage.
  • the voltage dividing circuit in the live wire sampling circuit includes a first resistor and a sixth resistor connected in series between the ground wires of the output live wire, and the connection terminal of the first resistor and the sixth resistor is the output terminal of the voltage divider circuit;
  • the voltage dividing circuit in the sampling circuit includes a second resistor and a fifth resistor connected in series between the ground of the output neutral line, and the connection terminal of the second resistor and the fifth resistor is the output terminal of the voltage dividing circuit.
  • the negative pressure bias circuit in the FireWire sampling circuit includes a fourth resistor, one end of the fourth resistor is connected to the bias power supply, and the other end is connected to the connection end of the first resistor and the sixth resistor; the neutral line sampling circuit
  • the negative voltage bias circuit in includes a third resistor, one end of the third resistor is connected to the bias power supply, and the other end is connected to the connection ends of the second resistor and the fifth resistor.
  • the impedance matching circuit uses an emitter follower or a voltage follower.
  • the impedance matching circuit in the FireWire sampling circuit includes a first operational amplifier, the non-inverting input terminal of the first operational amplifier is connected to the connection terminal of the first resistor and the sixth resistor, and the output terminal of the first operational amplifier is connected to the reverse Phase input terminal and output the sampling voltage;
  • the impedance matching circuit in the neutral sampling circuit includes a second operational amplifier, the non-inverting input terminal of the second operational amplifier is connected to the connection terminal of the second resistor and the fifth resistor The output terminal of the second operational amplifier is connected to its inverting input terminal and outputs the sampling voltage.
  • the summing circuit includes a seventh resistor, an eighth resistor, a ninth resistor, and an output terminal A, the seventh resistor is connected in series between the output terminal A and the output terminal of the first operational amplifier, and the eighth resistor is connected in series at the output Between the terminal A and the output terminal of the second operational amplifier, a ninth resistor is connected in series between the output terminal A and the ground, and the output terminal A outputs the summed voltage.
  • a detection method for an insulation detection circuit of a bidirectional vehicle-mounted charger includes an inverter circuit, a first Y capacitor connected between the output live wire and the ground wire of the inverter circuit, and connected to the output neutral wire and ground of the inverter circuit
  • the second Y capacitor between the lines includes the following steps: sampling the voltage on the output live line and output neutral line of the inverter circuit respectively to obtain a sampling voltage, and judging the insulation state of the two-way vehicle charger based on the two sampling voltages.
  • the invention detects the magnitude of the insulation resistance of the output live line L and the output neutral line N to the ground when the vehicle-mounted charger works in the inverter variable mode, judges whether there is an insulation failure between the AC output of the pure inverter mode and the vehicle body, and eliminates personnel electric shock Hidden danger; at the same time, the invention has the advantages of simple and practical structure and easy realization of low cost.
  • FIG. 1 is a schematic block diagram of a preferred embodiment of the present invention.
  • Figure 2 is a circuit diagram without using the summing circuit
  • Figure 3 is a circuit diagram using the sum circuit
  • Figure 4 is the waveform of the summed voltage when the insulation is normal
  • Figure 5 is the waveform of the summed voltage when the insulation fails
  • Figure 6 is the voltage waveform at each point when the insulation is normal
  • Figure 7 shows the voltage waveforms at various points when the insulation fails.
  • the output live line L and output zero line N on the AC output port have Y capacitors to the ground line, and the output live line L and output zero
  • the capacitance value of the Y capacitor of line N to ground is equal.
  • the presence of the Y capacitor makes the output live line L and the output neutral line N have voltages respectively to the ground and are 180 ° out of phase; the amplitude of the voltage and the capacitor output live line L and output
  • the capacitance value of the neutral line N is proportional to each other.
  • the invention provides an insulation detection circuit and a detection method for a bidirectional vehicle-mounted charger.
  • the insulation resistance of the output live line L and the output neutral line N to ground is obtained by detecting the voltage of the output live line L and the output neutral line N to ground
  • the size is used to detect whether there is an insulation failure between the AC output of the pure inverter mode and the car body of the car charger, thereby eliminating the hidden danger of electric shock.
  • the invention discloses an insulation detection circuit of a two-way vehicle charger, which includes an inverter circuit, a first Y capacitor C1 connected between the output live wire and the ground wire of the inverter circuit, and connected between the output neutral wire and the ground wire of the inverter circuit Between the second Y capacitor C2, which also includes a live wire sampling circuit and a neutral wire sampling circuit corresponding to the output live wire and the output neutral wire of the inverter circuit, a controller connected to the live wire sampling circuit and the neutral wire sampling circuit, wherein the live wire sampling The circuit and the neutral sampling circuit respectively output sampling voltages, and the controller judges the insulation state of the two-way vehicle charger based on the two sampling voltages.
  • an adder circuit is provided between the controller and the live-wire sampling circuit and the neutral-line sampling circuit, and the adder circuit adds the two sampled voltages
  • the sum processing obtains the sum voltage, and transmits the sum voltage to the controller, and the controller judges the insulation state of the bidirectional vehicle-mounted charger according to the sum voltage.
  • the summing process can be calculated inside the controller, and the circuit diagram of the embodiment is shown in FIG. 2; the summing process can also be processed outside the controller, and then the summed voltage is transmitted to the control after processing
  • the circuit diagram of its embodiment is shown in FIG. 3.
  • the live line sampling circuit and the neutral line sampling circuit have the same circuit structure, and all include a voltage dividing circuit, a bias power supply, a negative voltage bias circuit, and an impedance matching circuit, wherein the voltage dividing circuit is connected to the The output live wire or output neutral wire is used to proportionally reduce the voltage and output the divided voltage; the negative voltage bias circuit is connected between the output terminal of the voltage dividing circuit and the bias power supply to bias the divided voltage
  • the impedance matching circuit is connected to the output terminal of the voltage divider circuit to perform impedance matching and output the sampling voltage. It should be pointed out that the impedance matching circuit can match the impedance of the input end and the output end, so that the input impedance is high and the output impedance is low, thereby enhancing the load carrying capacity.
  • the voltage divider circuit in the FireWire sampling circuit includes a first resistor R1 and a sixth resistor R6 connected in series between the ground wire of the output Firewire, the first resistor and the sixth resistor Is connected to the output terminal of the voltage divider circuit;
  • the voltage divider circuit in the neutral sampling circuit includes a second resistor R2 and a fifth resistor R5 connected in series between the ground of the output neutral line, the second resistor and the fifth resistor Is the output of the voltage divider circuit.
  • the negative voltage bias circuit in the FireWire sampling circuit includes a fourth resistor R4, one end of the fourth resistor is connected to the bias power supply, and the other end is connected to the connection ends of the first resistor and the sixth resistor; the neutral line sampling
  • the impedance matching circuit uses an emitter follower or a voltage follower.
  • the impedance matching circuit in the FireWire sampling circuit includes a first operational amplifier oab1, an in-phase input terminal of the first operational amplifier is connected to the connection terminal of the first resistor and the sixth resistor, and an output terminal of the first operational amplifier is connected to the The inverting input terminal outputs the sampling voltage;
  • the impedance matching circuit in the neutral sampling circuit includes a second operational amplifier oab2, and the non-inverting input terminal of the second operational amplifier is connected to the second resistor and the fifth resistor
  • the connecting terminal, the output terminal of the second operational amplifier is connected to the inverting input terminal and outputs the sampling voltage.
  • the summing circuit includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9 and an output terminal A, the seventh resistor is connected in series at the output terminal A and the output terminal of the first operational amplifier Between, the eighth resistor is connected in series between the output terminal A and the output terminal of the second operational amplifier, the ninth resistor is connected in series between the output terminal A and the ground line, and the output terminal A outputs the summed voltage.
  • the Y capacitor generates the output live line L to ground and the output neutral line N to ground to generate voltages VL and VN, respectively, and the phases of the two voltages differ by 180 °.
  • the magnitude of these two voltages is related to the ratio of the Y capacitor, where:
  • f is the frequency of the AC voltage, and t is the time; connect the resistors R2 and R5 between the output neutral N and the ground, reduce the voltage on the output neutral N proportionally, and form a voltage at the connection point B of R2 and R5 VB1.
  • a resistor R3 is added between the bias power supply v_pwl1 and point B, and v_pwl1, R3, and R5 form a DC bias voltage VB2 to point C; the voltage VB at point B is the sum of VB1 and VB2.
  • resistors R1 and R6 between the output live line L and the ground line, proportionally reduce the voltage on the output live line L, form a voltage VC1 at the point C of R1 and R6, and add it between the bias power supply v_pwl1 and point C
  • Resistor R4, v_pwl1 and R4, R6 form a DC bias voltage VC2 for point C; the voltage VC at point C is the sum of VC1 and VC2.
  • VC1 VL * R6 / (R1 + R6); (Formula 6)
  • the voltage at point C passes through the impedance matching circuit, the voltage VD at the output point of the first operational amplifier is equal to VC; similarly, the voltage at point B passes through the impedance matching circuit, and the voltages VE and VB at the output point of the second operational amplifier Equal; the voltage at point D and point E is added to point A through resistors R7 and R8; the voltage at point A is:
  • VA VD + VE; (Formula 9)
  • the voltage at point A in Figure 2 and Figure 3 is sent to the AD sampling port of the controller MCU.
  • the impedance of the output live line L and the output zero line N to the ground line is infinite, that is, pwlr1 is infinite in the figure, and the output live line L to the ground line Y
  • the capacitance C1 is equal to the Y capacitance C2 of the output neutral N to ground.
  • the voltage division VB1 of the output live line L to ground and the voltage division VC1 of the output neutral N to ground add to zero, as shown in the following formula Show:
  • the sum of the voltage at point A is the sum of the negative bias voltage, that is, under normal insulation
  • the controller MCU reads the voltage value at point A through AD sampling.
  • the voltage value at point A is equal to the sum of the negative bias voltage values of the output live line L and the output neutral line N (the voltage at point A is shown in FIG. 4), and the sum voltage
  • the amplitude remains unchanged and the graph shows a straight line, then the controller MCU judges that the output live line L and the output neutral line N are properly insulated.
  • the insulation resistance pwlr1 is considered to be infinite, which is ignored in the above formula.
  • VL is the voltage of the output live line L to ground
  • VN is the voltage of the output neutral line N to ground
  • VA0 is the voltage of the R7 output terminal
  • VA1 is the voltage of the R8 output terminal.
  • the controller MCU uses M two different AD sampling ports to sample VL and VN to the MCU, and uses the MCU to perform addition processing.
  • the invention also discloses a method for detecting the insulation detection circuit of the two-way vehicle charger.
  • the detection circuit includes an inverter circuit, a first Y capacitor C1 connected between the output live wire and the ground wire of the inverter circuit, and connected to the inverter
  • the circuit outputs the second Y capacitor C2 between the neutral and the ground, which includes the following steps: separately sampling the voltages of the output live and neutral lines of the inverter circuit to obtain a sampling voltage, and judging the two-way vehicle charger based on the two sampling voltages Insulated state.
  • a voltage divider circuit is used to proportionally reduce the voltage on the output live line and output neutral line of the inverter circuit to generate a divided voltage; a negative voltage bias circuit is used to bias the divided voltage , The divided voltage after the bias processing is output through impedance matching to sample the voltage; the summation circuit is used to sum the sample voltage of the output live line and the sample voltage of the output neutral line to obtain the sum voltage, and the two-way judgment is based on the sum voltage Insulation state of vehicle charger.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
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  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

一种双向车载充电机绝缘检测电路及其检测方法，所述检测电路包括逆变电路，连接在逆变电路输出火线(L)与地线之间的第一Y电容(C1)，连接在逆变电路输出零线(N)与地线之间的第二Y电容(C2)，还包括对应连接逆变电路输出火线(L)和输出零线(N)的火线采样电路和零线采样电路，连接火线采样电路和零线采样电路的控制器，其中所述火线采样电路和零线采样电路分别输出采样电压，控制器根据两个采样电压判断双向车载充电机绝缘状态；在车载充电机工作在逆变模式时，检测输出火线(L)和输出零线(N)对地绝缘阻抗的大小，判断纯逆变模式AC输出与车体之间是否存在绝缘失效，消除人员触电隐患；同时具有结构简单实用，易于实现造价低廉的优点。

Description

一种双向车载充电机绝缘检测电路及其检测方法 技术领域
本发明涉及充电设备，尤其涉及一种双向车载充电机绝缘检测电路及其检测方法。
背景技术
能源危机和环境污染已在世界范围内日趋严重，整个传统汽车工业和世界客观环境面临严峻挑战。随着公众环保意识的加强，倡导绿色出行及改变出行结构俨然已成为主流。随着发达国家政府发展新能源汽车的计划，我国政府也公布了相应的新能源车发展计划，新能源车也已列入七大新兴战略产业。而新能源车里面目前当属电动车最为主流。车载充电机是电动车中十分重要的部件，车载充电机的好坏直接影响到车辆的安全性和可靠性。车载充电机火线与地线绝缘的好坏又关乎到整机的性能，如火线与地线绝缘失效容易引起元器件损毁甚至人员触电。以往的检测手段是停电后，用仪器进行检测。具有操作繁琐，不能实时监控的缺陷。
故此业内亟需开发一种操作简便，可以在逆变模式下实时检测绝缘的绝缘检测电路及其检测方法。
发明内容
本发明是要解决现有技术的上述问题，提出一种用于检测车载充电机工作在纯逆变模式AC输出与车体之间是否存在绝缘失效的检测电路及其检测方法。
为解决上述技术问题，本发明提出的技术方案是设计一种双向车载充电机绝缘检测电路，包括逆变电路，连接在逆变电路输出火线与地线之间的第一Y电容，连接在逆变电路输出零线与地线之间的第二Y电容，其还包括对应连接逆变电路输出火线和输出零线的火线采样电路和零线采样电路，连接火线采样电路和零线采样电路的控制器，其中所述火线采样电路和零线采样电路分别输出采样电压，控制器根据两个采样电压判断双向车载充电机绝缘状态。
所述控制器与火线采样电路和零线采样电路之间设有一个加和电路，所述加和电路对所述两个采样电压进行加和处理得出加和电压，并将加和电压传输给所述控制器，控制器根据加和电压判断双向车载充电机绝缘状态。
所述火线采样电路和零线采样电路具有相同电路结构，皆包括分压电路、偏置电源、负压偏置电路、阻抗匹配电路，其中所述分压电路连接所述输出火线或输出零线，用以按比例减小电压输出分压电压；所述负压偏置电路连接在分压电路输出端与偏置电源之间，对所述分压电压进行偏置；所述阻抗匹配电路连接分压电路输出端，进行阻抗匹配并输出所述采样电压。
所述火线采样电路中的分压电路包括串联在输出火线的地线之间的第一电阻和第六电阻，第一电阻和第六电阻的连接端为分压电路输出端；所述零线采样电路中的分压电路包括串联在输出零线的地线之间的第二电阻和第五电阻，第二电阻和第五电阻的连接端为分压电路输出端。
所述火线采样电路中的负压偏置电路包括第四电阻，第四电阻一端连接所述偏置电源、另一端连接所述第一电阻和第六电阻的连接端；所述零线采样电路中的负压偏置电路包括第三电阻，第三电阻一端连接所述偏置电源、另一端连接所述第二电阻和第五电阻的连接端。
所述阻抗匹配电路采用射极跟随器或电压跟随器。
所述火线采样电路中的阻抗匹配电路包括第一运算放大器，所述第一运算放大器的同相输入端连接所述第一电阻和第六电阻的连接端，第一运算放大器的输出端连接其反相输入端并输出所述采样电压；所述零线采样电路中的阻抗匹配电路包括第二运算放大器，所述第二运算放大器的同相输入端连接所述第二电阻和第五电阻的连接端，第二运算放大器的输出端连接其反相输入端并输出所述采样电压。
所述加和电路包括第七电阻、第八电阻、第九电阻和输出端A，所述第七电阻串接在输出端A与第一运算放大器输出端之间，第八电阻串接在输出端A与第二运算放大器输出端之间，第九电阻串接在输出端A与地线之间，输出端A输出所述加和电压。
一种双向车载充电机绝缘检测电路的检测方法，所述检测电路包括逆变电路，连接在逆变电路输出火线与地线之间的第一Y电容，连接在逆变电路输出零线与地线之间的第二Y电容，其包括以下步骤：对逆变电路输出火线和输出零线上的电压分别采样得到采样电压，根据两个采样电压判断双向车载充电机绝缘状态。
分别用分压电路对逆变电路输出火线和输出零线上的电压按比例减小生 成分压电压；用负压偏置电路对所述分压电压进行偏置处理，将偏置处理后的分压电压通过阻抗匹配输出采样电压；用加和电路对输出火线的采样电压和输出零线的采样电压进行加和处理得出加和电压，根据加和电压判断双向车载充电机绝缘状态。
本发明在车载充电机工作在逆变变模式时，检测输出火线L和输出零线N对地绝缘阻抗的大小，判断纯逆变模式AC输出与车体之间是否存在绝缘失效，消除人员触电隐患；同时本发明具有结构简单实用，易于实现造价低廉的优点。
附图说明
图1为本发明较佳实施例的原理框图；
图2为未采用加和电路的电路图；
图3为采用加和电路的电路图；
图4为绝缘正常时加和电压的波形图；
图5为绝缘失效时加和电压的波形图；
图6为绝缘正常时各点电压波形；
图7为绝缘失效时各点电压波形。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明作进一步详细说明。应当理解，此处所描述的具体实施例仅仅用于解释本发明，并不用于限定本发明。
车载充电机工作在逆变状态时，由于正向OBC对EMI的要求，逆变时AC输出端口上的输出火线L和输出零线N对地线都有Y电容，并且输出火线L和输出零线N对地的Y电容容值是相等的，Y电容的存在使得输出火线L与输出零线N分别对地都有电压，并且错相180°；电压的幅值与电容输出火线L和输出零线N的容值比例相关，当输出火线L或者输出零线N对地的绝缘失效时，输出火线L或者输出零线N对地的电压将失去均衡。本发明提供双向车载充电机绝缘检测电路及其检测方法，在逆变模式下通过检测输出火线L与输出零线N对地的电压从而得出输出火线L和输出零线N对地的绝缘阻抗的大小，用于检测车载充电机工作在纯逆变模式AC输出与车体之间是否存在绝缘失效，从而消除人员触电隐患。
本发明公开了一种双向车载充电机绝缘检测电路，包括逆变电路，连接 在逆变电路输出火线与地线之间的第一Y电容C1，连接在逆变电路输出零线与地线之间的第二Y电容C2，其还包括对应连接逆变电路输出火线和输出零线的火线采样电路和零线采样电路，连接火线采样电路和零线采样电路的控制器，其中所述火线采样电路和零线采样电路分别输出采样电压，控制器根据两个采样电压判断双向车载充电机绝缘状态。
参看图1示出的较佳实施例的原理框图，所述控制器与火线采样电路和零线采样电路之间设有一个加和电路，所述加和电路对所述两个采样电压进行加和处理得出加和电压，并将加和电压传输给所述控制器，控制器根据加和电压判断双向车载充电机绝缘状态。需要指出，加和处理可以在控制器内部进行运算，其实施例的电路图如图2所示；加和处理也可以在控制器外部进行处理，处理完毕后再将加和电压传输给所述控制器，其实施例的电路图如图3所示。
在较佳实施例中，所述火线采样电路和零线采样电路具有相同电路结构，皆包括分压电路、偏置电源、负压偏置电路、阻抗匹配电路，其中所述分压电路连接所述输出火线或输出零线，用以按比例减小电压输出分压电压；所述负压偏置电路连接在分压电路输出端与偏置电源之间，对所述分压电压进行偏置；所述阻抗匹配电路连接分压电路输出端，进行阻抗匹配并输出所述采样电压。需要指出，阻抗匹配电路可以匹配输入端和输出端的阻抗，使输入阻抗高、输出阻抗低，从而增强带负荷能力。
参看图2和图3示出的实施例，所述火线采样电路中的分压电路包括串联在输出火线的地线之间的第一电阻R1和第六电阻R6，第一电阻和第六电阻的连接端为分压电路输出端；所述零线采样电路中的分压电路包括串联在输出零线的地线之间的第二电阻R2和第五电阻R5，第二电阻和第五电阻的连接端为分压电路输出端。分压比例由第一电阻R1和第六电阻R6，第二电阻R2和第五电阻R5的比值决定。在较佳实施例中：R1＝R2；R5＝R6。
所述火线采样电路中的负压偏置电路包括第四电阻R4，第四电阻一端连接所述偏置电源、另一端连接所述第一电阻和第六电阻的连接端；所述零线采样电路中的负压偏置电路包括第三电阻R3，第三电阻一端连接所述偏置电源、另一端连接所述第二电阻和第五电阻的连接端。在较佳实施例中R3＝R4。
所述阻抗匹配电路采用射极跟随器或电压跟随器。
所述火线采样电路中的阻抗匹配电路包括第一运算放大器oab1，所述第一运算放大器的同相输入端连接所述第一电阻和第六电阻的连接端，第一运算放大器的输出端连接其反相输入端并输出所述采样电压；所述零线采样电 路中的阻抗匹配电路包括第二运算放大器oab2，所述第二运算放大器的同相输入端连接所述第二电阻和第五电阻的连接端，第二运算放大器的输出端连接其反相输入端并输出所述采样电压。
在较佳实施例中，所述加和电路包括第七电阻R7、第八电阻R8、第九电阻R9和输出端A，所述第七电阻串接在输出端A与第一运算放大器输出端之间，第八电阻串接在输出端A与第二运算放大器输出端之间，第九电阻串接在输出端A与地线之间，输出端A输出所述加和电压。
下面结合图3详述本发明的工作原理。充电机逆变输出火线L和输出零线N分别对地存在Y电容，即第一Y电容C1和第二Y电容C2，其中C1＝C2。Y电容将输出火线L对地、输出零线N对地产生分别产生电压VL、VN，并且这两个电压的相位相差180°，这两个电压的大小与Y电容的比例有关，其中：
Figure PCTCN2018115259-appb-000001
Figure PCTCN2018115259-appb-000002
f为交流电压的频率，t为时间；在输出零线N与地线之间接入电阻R2、R5，按比例减小输出零线N上的电压，在R2和R5的连接端B点形成电压VB1。在偏置电源v_pwl1与B点之间加入电阻R3，v_pwl1与R3、R5对C点形成直流偏置电压VB2；B点电压VB为VB1与VB2之和。
VB1＝VN*R5/(R2+R5)；(公式3)
VB2＝v_pwl1*R5/(R3+R5)；(公式4)
VB＝VB1+VB2；(公式5)
在输出火线L与地线之间接入电阻R1、R6，按比例减小输出火线L上的电压，在R1和R6的连接端C点形成电压VC1，在偏置电源v_pwl1与C点之间加入电阻R4，v_pwl1与R4、R6对C点形成直流偏置电压VC2；C点电压VC为VC1与VC2之和。
VC1＝VL*R6/(R1+R6)；(公式6)
VC2＝v_pwl1*R6/(R4+R6)；(公式7)
VC＝VC1+VC2；(公式8)
C点电压经过阻抗匹配电路后，在第一运算放大器的输出端D点电压VD与VC相等；同理B点电压经过阻抗匹配电路后，在第二运算放大器的输出端E点点电压VE与VB相等；D点和E点电压经过电阻R7、R8相加于A 点；A点电压为：
VA＝VD+VE；(公式9)
结合公式1至9得：
Figure PCTCN2018115259-appb-000003
图2图3中的A点电压送到控制器MCU的AD采样端口，正常状态输出火线L与输出零线N对地线阻抗无穷大，即图中pwlr1无穷大，且输出火线L对地线的Y电容C1与输出零线N对地线的Y电容C2相等，在绝缘正常状态，输出火线L对地线的分压VB1和输出零线N对地线的分压VC1相加等于零，如下式所示：
Figure PCTCN2018115259-appb-000004
A点的电压的和为负压偏置电压的和，即绝缘正常状态下
Figure PCTCN2018115259-appb-000005
控制器MCU通过AD采样读取A点电压值，A点电压值与输出火线L、输出零线N的负压偏置电压值的和相等(A点电压如图4所示)，加和电压幅值保持不变，图形呈现一条直线，则控制器MCU判断输出火线L和输出零线N绝缘正常。在正常状态，认为绝缘电阻pwlr1无穷大，在上述公式中忽略不计。图6为绝缘正常时各点电压波形，VL为输出火线L对地电压，VN为输出零线N对地电压，VA0为R7输出端电压，VA1为R8输出端电压。
当输出火线L或者输出零线N对地线出现绝缘失效，输出火线L或者输出零线N对地线的阻抗在减小，即图中的PWLr1由无穷大减小，输出火线L对地的阻抗将减小，此时VL对地线与VN对地线的电压将失去平衡，VN与VL相加不再等于零，实测如图5所示，加和电压幅值呈现正弦波波形，控制器MCU将根据AD采样的电压值判断出绝缘失效以及判断出绝缘电阻阻值的大小。图7为绝缘失效时各点电压波形，VL为输出火线L对地电压，VN为输出零线N对地电压，VA0为R7输出端电压，VA1为R8输出端电压。
图示出的一个实施例中，控制器MCU采用M两个不同的AD采样端口将VL和VN的采样到MCU，利用MCU进行加和处理。
本发明还公开了一种双向车载充电机绝缘检测电路的检测方法，所述检测电路包括逆变电路，连接在逆变电路输出火线与地线之间的第一Y电容C1，连接在逆变电路输出零线与地线之间的第二Y电容C2，其包括以下步骤：对逆变电路输出火线和输出零线上的电压分别采样得到采样电压，根据两个采样电压判断双向车载充电机绝缘状态。
在较佳实施例中，分别用分压电路对逆变电路输出火线和输出零线上的电压按比例减小生成分压电压；用负压偏置电路对所述分压电压进行偏置处理，将偏置处理后的分压电压通过阻抗匹配输出采样电压；用加和电路对输出火线的采样电压和输出零线的采样电压进行加和处理得出加和电压，根据加和电压判断双向车载充电机绝缘状态。
以上实施例仅为举例说明，非起限制作用。任何未脱离本申请精神与范畴，而对其进行的等效修改或变更，均应包含于本申请的权利要求范围之中。

Claims (10)

  1. 一种双向车载充电机绝缘检测电路，包括逆变电路，连接在逆变电路输出火线与地线之间的第一Y电容(C1)，连接在逆变电路输出零线与地线之间的第二Y电容(C2)，其特征在于，还包括对应连接逆变电路输出火线和输出零线的火线采样电路和零线采样电路，连接火线采样电路和零线采样电路的控制器，其中
    所述火线采样电路和零线采样电路分别输出采样电压，控制器根据两个采样电压判断双向车载充电机绝缘状态。
  2. 如权利要求1所述的双向车载充电机绝缘检测电路，其特征在于，所述控制器与火线采样电路和零线采样电路之间设有一个加和电路，所述加和电路对所述两个采样电压进行加和处理得出加和电压，并将加和电压传输给所述控制器，控制器根据加和电压判断双向车载充电机绝缘状态。
  3. 如权利要求1或2任一项所述的双向车载充电机绝缘检测电路，其特征在于，所述火线采样电路和零线采样电路具有相同电路结构，皆包括分压电路、偏置电源、负压偏置电路、阻抗匹配电路，其中
    所述分压电路连接所述输出火线或输出零线，用以按比例减小电压输出分压电压；
    所述负压偏置电路连接在分压电路输出端与偏置电源之间，对所述分压电压进行偏置；
    所述阻抗匹配电路连接分压电路输出端，进行阻抗匹配并输出所述采样电压。
  4. 如权利要求3所述的双向车载充电机绝缘检测电路，其特征在于，所述火线采样电路中的分压电路包括串联在输出火线的地线之间的第一电阻(R1)和第六电阻(R6)，第一电阻和第六电阻的连接端为分压电路输出端；所述零线采样电路中的分压电路包括串联在输出零线的地线之间的第二电阻(R2)和第五电阻(R5)，第二电阻和第五电阻的连接端为分压电路输出端。
  5. 如权利要求4所述的双向车载充电机绝缘检测电路，其特征在于，所述火线采样电路中的负压偏置电路包括第四电阻(R4)，第四电阻一端连接所述偏置电源、另一端连接所述第一电阻和第六电阻的连接端；所述零线采样电路中的负压偏置电路包括第三电阻(R3)，第三电阻一端连接所述偏置电源、另一端连接所述第二电阻和第五电阻的连接端。
  6. 如权利要求5所述的双向车载充电机绝缘检测电路，其特征在于， 所述阻抗匹配电路采用射极跟随器或电压跟随器。
  7. 如权利要求5所述的双向车载充电机绝缘检测电路，其特征在于，所述火线采样电路中的阻抗匹配电路包括第一运算放大器，所述第一运算放大器的同相输入端连接所述第一电阻和第六电阻的连接端，第一运算放大器的输出端连接其反相输入端并输出所述采样电压；所述零线采样电路中的阻抗匹配电路包括第二运算放大器，所述第二运算放大器的同相输入端连接所述第二电阻和第五电阻的连接端，第二运算放大器的输出端连接其反相输入端并输出所述采样电压。
  8. 如权利要求7所述的双向车载充电机绝缘检测电路，其特征在于，所述加和电路包括第七电阻(R7)、第八电阻(R8)、第九电阻(R9)和输出端A，所述第七电阻串接在输出端A与第一运算放大器输出端之间，第八电阻串接在输出端A与第二运算放大器输出端之间，第九电阻串接在输出端A与地线之间，输出端A输出所述加和电压。
  9. 一种双向车载充电机绝缘检测电路的检测方法，所述检测电路包括逆变电路，连接在逆变电路输出火线与地线之间的第一Y电容(C1)，连接在逆变电路输出零线与地线之间的第二Y电容(C2)，其特征在于，包括以下步骤：对逆变电路输出火线和输出零线上的电压分别采样得到采样电压，根据两个采样电压判断双向车载充电机绝缘状态。
  10. 如权利要求9所述的双向车载充电机绝缘检测电路的检测方法，其特征在于，分别用分压电路对逆变电路输出火线和输出零线上的电压按比例减小生成分压电压；用负压偏置电路对所述分压电压进行偏置处理，将偏置处理后的分压电压通过阻抗匹配输出采样电压；用加和电路对输出火线的采样电压和输出零线的采样电压进行加和处理得出加和电压，根据加和电压判断双向车载充电机绝缘状态。
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