Abstract:
A semiconductor device including: lines connected to lines between respective neighboring battery cells of plural battery cells connected in series; at each of the battery cells, a voltage detection portion that detects a battery voltage value of the battery cell based on a voltage provided by the lines connected to the high potential side of the battery cell and to the low potential side of the battery cell; and at each of the lines, a regulation portion that regulates current to make a first current and a second current cancel out, the first current being caused to flow in a first direction in the resistor element by the battery cell at the high potential side of the line, and the second current being caused to flow in a second direction in the resistor element by the battery cell at the low potential side of the line.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-073564 filed on Mar. 28, 2012, the disclosure of which is incorporated by reference herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a semiconductor device and a battery monitoring system, and particularly relates to a semiconductor device and battery monitoring system that detect voltages of battery cells. 
         [0004]    2. Related Art 
         [0005]    In general, a battery pack (assembled battery) in which plural batteries (battery cells) are connected in series is used as a high-power battery with high capacity to be utilized for driving a motor in a hybrid automobile or an electric automobile, or the like (as a concrete example, a lithium ion battery or the like can be mentioned). A battery monitoring system that detects and monitors voltages of the battery cells of this battery with voltage detection circuits is known. As an example of this kind of voltage detection circuit, the technology recited in Japanese Patent Application Laid-Open (JP-A) No. 2010-281805 is known. 
         [0006]    Another technology is recited in JP-A No. 2001-116776, in which a noise removal filter that removes noise produced by a battery cell is provided between the battery cell and a voltage detection circuit. 
         [0007]    An example of a related art battery monitoring system and voltage detection circuit is shown in  FIG. 6  and  FIG. 7 . Here, as a specific example, three battery cells C of a battery cell group  12  are illustrated in  FIG. 6 . As shown in  FIG. 7 , a voltage detection circuit  200  of a related art battery monitoring system  100  is provided at each battery cell C. 
         [0008]    The voltage detection circuit  200  divides a battery voltage from the battery cell C (a difference between a high potential side voltage and a low potential side voltage of the battery cell) over a resistor Ra and a resistor Rb, and is equipped with a comparison circuit (a comparator  300 ) that compares the divided voltage with a reference voltage generated by a reference voltage generation circuit, and outputs a comparison result. 
         [0009]    If the battery voltages of neighboring battery cells C are different, the related art battery monitoring system  100  as shown in  FIG. 6  may not be able to accurately detect the battery voltages of the battery cells C, due to the effect of a noise removal filter  14  connected between the battery cell group  12  and the voltage detection circuits  200 . 
         [0010]    Operation of the related art voltage detection circuit  200  is described with reference to  FIG. 8 . As shown in  FIG. 8 , a current flowing in a battery cell C 1  is represented by I 1 , and an input voltage of the voltage detection circuit  200  thereof is represented by V 1 . Similarly, a current flowing in a battery cell C 2  is represented by I 2  and the input voltage of the voltage detection circuit  200  thereof is represented by V 2 , and a current flowing in a battery cell C 3  is represented by I 3  and the input voltage of the voltage detection circuit  200  thereof is represented by V 3 . 
         [0011]    The noise removal filter  14  is a low-pass filter (LPF) constituted by an RC circuit. Resistors to which the same reference numeral is assigned in the RC circuits have equal resistance values. 
         [0012]    Firstly, a case in which the battery voltages of neighboring battery cells C are equal is described. Specifically, a state in which the battery voltages of the battery cells C (C 1 , C 2  and C 3 ) of the battery cell group  12  are all equal is described. 
         [0013]    Of current flowing in a resistor R 1  of the noise removal filter  14 , a current flowing from a low potential side (lower level) battery cell C and a current flowing from a high potential side (upper level) battery cell C flow in opposite directions. Given that the battery voltages of these battery cells C are equal, the values of the two currents are equal, the currents flowing in the resistor R 1  cancel out, and there is no voltage drop across the resistor R 1 . Therefore, when the battery voltages of the battery cells C are equal, the battery voltage of each battery cell C becomes the input voltage V of the voltage detection circuit  200  thereof, and there are no differences between the input voltages V. 
         [0014]    In a resistor R 2  that is connected to the highest potential battery cell C 3 , current flows in only one direction (corresponding to a current flowing from the low potential side battery cell). Therefore, there is a voltage drop across the resistor R 2 , and there may be a difference between the battery voltage of the highest potential battery cell C 3  and the input voltage V of the voltage detection circuit  200  thereof Reducing the resistance value of resistor R 2  is commonly used as a measure to moderate the effects of this difference. 
         [0015]    Next, a case in which the battery voltages of neighboring battery cells C are not equal is described. As a specific example, a case in which the battery voltage of the battery cell C 1  is smaller than those of the other battery cells C (C 2  and C 3 ) is described. In this case, the current I 1  is not equal to the current I 2 . 
         [0016]    A current that flows in the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 1  and the battery cell C 2  is the difference between current I 1  and current I 2 . Given that the battery cell C 2  has a larger battery voltage than the battery cell C 1 , current I 2  is larger than current I 1 . Therefore, the current flowing through the resistor R 1  is not substantially at zero, and a voltage drop is caused by the current difference between current I 1  and current I 2 . Therefore, there are differences between the input voltages V of the voltage detection circuits  200  and the battery voltages of the battery cells C, and accurate voltage detections may not be possible. 
       SUMMARY 
       [0017]    The present invention is proposed to solve the problem described above, and an object of the present invention is to provide a semiconductor device and battery monitoring system that may accurately detect battery voltages of battery cells regardless of variations in the battery voltages. 
         [0018]    A first aspect of the present invention provides a semiconductor device including: 
         [0019]    plural lines connected, each via a resistor element, to lines between respective neighboring battery cells of plural battery cells connected in series; 
         [0020]    at each of the plural battery cells, a voltage detection portion that detects a battery voltage value of the battery cell in accordance with a voltage provided by the line that is connected to the high potential side of the battery cell and the line that is connected to the low potential side of the battery cell; and 
         [0021]    at each of the plural lines, a regulation portion that regulates current to make a first current and a second current cancel out, the first current being caused to flow in a first direction in the resistor element by the battery cell at the high potential side of the line, and the second current being caused to flow in a second direction in the resistor element by the battery cell at the low potential side of the line. 
         [0022]    A second aspect of the present invention provides a battery monitoring system including: 
         [0023]    plural battery cells connected in series; 
         [0024]    a noise removal portion comprising resistor elements and capacitor elements connected to high potential sides of the plural battery cells; 
         [0025]    plural lines connected, via the resistor elements of the noise removal portion, to lines between respective neighboring battery cells of the plural battery cells; 
         [0026]    at each of the plural battery cells, a voltage detection portion capable of detecting a battery voltage value of the battery cell in accordance with a voltage provided by the line that is connected to the high potential side of the battery cell and the line that is connected to the low potential side of the battery cell; and 
         [0027]    at each of the plural lines, a regulation portion configured to regulate current to make a first current and a second current cancel out, the first current being caused to flow in a first direction in the resistor element by the battery cell at the high potential side of the line, and the second current being caused to flow in a second direction in the resistor element by the battery cell at the low potential side of the line. 
         [0028]    According to the present invention, an effect is provided in that battery voltages of battery cells may be accurately detected regardless of variations in the battery voltages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
           [0030]      FIG. 1  is a circuit diagram showing an example of schematic structure of a battery monitoring system in accordance with a first exemplary embodiment; 
           [0031]      FIG. 2  is a schematic diagram showing relationships between voltage detection circuits and a battery cell group in accordance with the first exemplary embodiment; 
           [0032]      FIG. 3  is a circuit diagram of an example of schematic structure of the voltage detection circuit in accordance with the first exemplary embodiment; 
           [0033]      FIG. 4  is a circuit diagram for describing operation of the example of the voltage detection circuit in accordance with the first exemplary embodiment; 
           [0034]      FIG. 5  is a circuit diagram for describing operation of an example of a voltage detection circuit in accordance with a second exemplary embodiment; 
           [0035]      FIG. 6  is a schematic diagram showing relationships between voltage detection circuits and a battery cell group in related art; 
           [0036]      FIG. 7  is a circuit diagram of an example of schematic structure of the related art voltage detection circuit; and 
           [0037]      FIG. 8  is a circuit diagram for describing operation of an example of the related art voltage detection circuit. 
       
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment  
       [0038]    Herebelow, a voltage detection circuit and battery monitoring system according to the first exemplary embodiment are described in detail with reference to the drawings. The battery monitoring system detects voltages of battery cells with the voltage detection circuit. 
         [0039]    First, structure of the battery monitoring system according to the present exemplary embodiment is described.  FIG. 1  shows an example of schematic structure of the battery monitoring system of the present exemplary embodiment. A battery monitoring system  10  of the present exemplary embodiment that is shown in  FIG. 1  is provided with the battery cell group  12  including a plural number of battery cells C (in the present exemplary embodiment, three battery cells C are illustrated in the battery cell group  12 ), the noise removal filter  14 , and a semiconductor device  16  equipped with voltage detection circuits  20  that detect battery voltages of the battery cells of the battery cell group  12 . 
         [0040]    The semiconductor device  16  is provided with the voltage detection circuits  20  and a microcontroller unit (MCU)  22 . The high potential sides and low potential sides of the battery cells C (C 1 , C 2  and C 3 ) of the battery cell group  12  are connected with respective voltage detection circuits  20   1 ,  20   2  and  20   3  via terminals (pads)  23  (see  FIG. 2 ). 
         [0041]    The MCU  22  is structured with a CPU and memory such as ROM, RAM and the like. The MCU  22  functions to perform pre-specified processing in accordance with whether or not outputs OUT that are outputted from the respective voltage detection circuits  20  ( 20   1 ,  20   2  and  20   3 ) are at predetermined potentials. 
         [0042]    In the present exemplary embodiment, the voltage detection circuits  20   1 ,  20   2  and  20   3  are provided for each of the battery cells C (C 1 , C 2  C 3 ). Relationships between the voltage detection circuits  20   1 ,  20   2  and  20   3  of the present exemplary embodiment and the battery cell group  12  are shown in  FIG. 2 . Hereinafter, where the voltage detection circuits  20   1 ,  20   2  and  20   3  are to be individually referred to, individually identified reference numerals are given, and where the voltage detection circuits  20   1 ,  20   2  and  20   3  are to be referred to in general, they are simply referred to as the voltage detection circuits  20 . 
         [0043]    The noise removal filter  14  is connected between the battery cell group  12  and the voltage detection circuits  20  (the semiconductor device  16 ). The noise removal filter  14  is a low-pass filter (LPF) constituted by RC circuits. The noise removal filter  14  functions to suppress sudden voltage changes occurring in the battery cells C, by cutting out high-frequency components. The resistors of the RC circuits of the noise removal filter  14  are a resistor R 2  that is connected only at the high potential side of the highest potential battery cell C (C 3 ), and resistors R 1  in the other RC circuits (described in more detail herebelow). R 2  has a smaller resistance value than R 1 . 
         [0044]    Each voltage detection circuit  20  functions to detect the battery voltage of the respective battery cell C.  FIG. 3  shows a circuit diagram of an example of schematic structure of the voltage detection circuit  20  of the present exemplary embodiment. 
         [0045]    In the voltage detection circuit  20  of the present exemplary embodiment, a resistor Ra and a constant current source I 0  are connected in series across an input voltage V of the voltage detection circuit  20  (between a line  1  connected to the high potential side of the battery cell C and a line  1  connected to the low potential side of the same). The voltage of the connection between the resistor Ra and the constant current source I 0  is inputted to the non-inverting terminal of a comparator  30 . The inverting terminal of the comparator  30  is connected such that a reference voltage generated by a reference voltage generation circuit is inputted thereto. The comparator  30  outputs a difference between the voltage inputted at the non-inverting terminal and the reference voltage inputted at the inverting terminal Because the constant current IO from the constant current source IO flows in the resistor Ra, the voltage inputted to the non-inverting terminal of the comparator  30  is V−I 0 ×Ra. Meanwhile, the reference voltage generated by the reference voltage generation circuit is inputted to the inverting terminal Therefore, by the reference voltage being set in accordance with the constant current I 0  and the resistor Ra, the input voltage V (or a voltage corresponding to the input voltage V) can be outputted from the comparator  30 . 
         [0046]    Now, a voltage detection operation of the voltage detection circuit  20  according to the present exemplary embodiment is described with reference to  FIG. 4 . In  FIG. 4 , as a specific example, a case is illustrated in which the battery cell group  12  is formed with three of the battery cells C and connected such that the battery cell C 3  is at the highest potential and the battery cell C 1  is at the lowest potential. The voltage detection circuits  20   1 ,  20   2  and  20   3  shown in  FIG. 4  are substantially identical. The resistance values of the resistors Ra (Ra 1 , Ra 2  and Ra 3 ) and the current values of the constant current sources I 0  (I 0   1 , I 0   2  and I 0   3 ) are equal, and the reference voltage generation circuits have identical structures. 
         [0047]    In  FIG. 4 , a current flowing in the battery cell C 1  is represented by I 1  and the input voltage of the voltage detection circuit  20   1  is represented by V 1 , a current flowing in the battery cell C 2  is represented by I 2  and the input voltage of the voltage detection circuit  20   2  is represented by V 2 , and a current flowing in the battery cell C 3  is represented by I 3  and the input voltage of the voltage detection circuit  20   3  is represented by V 3 . 
         [0048]    Currents flowing in the battery cells C due to the constant current sources I 0   1 , I 0   2  and I 0   3  are I 1 , I 2  and I 3 , which are all equal to the constant current I 0  regardless of the battery voltages of the battery cells C. 
         [0049]    Therefore, the current values of the current I 1  and the current I 2  in the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 1  and the battery cell C 2  are equal to the constant current I 0  and flow in opposite directions to one another. Therefore, current I 1  and current I 2  cancel out, current flowing through the resistor R 1  is substantially zero, and there is no voltage drop across the resistor R 1 . Similarly, in the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 2  and the battery cell C 3 , current flowing through the resistor R 1  is substantially at zero and there is no voltage drop across the resistor R 1 . 
         [0050]    Only current I 3  (a current in one direction) flows in the resistor R 2  of the noise removal filter  14  that is connected at the high potential side of the battery cell C 3 . Therefore, there is a voltage drop across the resistor R 2 , and there is a difference between the battery voltage of the battery cell C 3  and the input voltage V 3 . Accordingly, the present exemplary embodiment has a structure in which the resistance value of the resistor R 2  is made smaller (at least, smaller than the resistors R 1 ) and the effect of the difference is moderated. 
         [0051]    Thus, according to the present exemplary embodiment, the resistor Ra and constant current source I 0  are connected in series between the line  1  connected to the high potential side of the respective battery cell C and the line  1  connected to the low potential side, and the voltage of the junction between the resistor Ra and the constant current source I 0  is inputted to the non-inverting terminal of the comparator  30 . Thus, the voltage inputted to each comparator  30  is generated by constant current consumption (the constant current source I 0 ) with no dependence on the battery voltage of the battery cell C. Therefore, a current flowing in the battery cell C is always at the constant current I 0 . 
         [0052]    Thus, in the resistors R 1 , the constant currents I 0  flow in mutually opposite directions and cancel out, and the currents are substantially at zero. Consequently, voltage drops across the resistors R 1  do not occur and there are no differences between the input voltages V of the voltage detection circuits  20  and the battery voltages of the battery cells C. As mentioned above, the input voltage V is outputted from the comparator  30 . Thus, because this difference does not occur in the present exemplary embodiment, the battery voltage of each battery cell C is accurately outputted from the corresponding comparator  30 . Therefore, even if a battery voltage of the battery cells C (C 1 , C 2  or C 3 ) is inconsistent, the battery voltages of the battery cells C may be accurately detected. 
       Second Exemplary Embodiment  
       [0053]    Herebelow, a voltage detection circuit according to a second exemplary embodiment of the present invention is described with reference to the drawings. The present exemplary embodiment features structures and operations that are substantially the same as in the voltage detection circuit  20  of the first exemplary embodiment. Accordingly, portions that are substantially the same are only recited in gist and are not described in detail. 
         [0054]      FIG. 5  shows a circuit diagram of an example of schematic structure of the voltage detection circuit  20  in accordance with the present exemplary embodiment. In the voltage detection circuit  20  of the present exemplary embodiment, constant current sources I 0   11 , I 0   12  and I 0   13  correspond to the constant current sources IO that are connected in series with the resistors Ra in the first exemplary embodiment. Other ends of the constant current sources I 0   11 , I 0   12  and I 0   13  are connected to ground (GND). Therefore, the constant current sources I 0   11 , I 0   12  and I 0   13  generate constant currents by reference to the ground potential GND. 
         [0055]    In the present exemplary embodiment, in place of the reference voltage generation circuits of the first exemplary embodiment, generation sources of the reference voltages that are inputted to the inverting terminals of the comparators  30   1 ,  30   2  and  30   3  are constant current sources I 0   21 , I 0   22  and I 0   23  and Zener diodes  32   1 ,  32   2  and  32   3 , which are connected to a power supply line VDD that supplies a power supply voltage VDD. 
         [0056]    In the present exemplary embodiment, the Zener diodes  32  are used in correspondence with the resistors Ra. Accordingly, the input voltages V (or voltages corresponding to the input voltages V) are outputted from the comparators  30 . 
         [0057]    A current I 1   1  flowing from the battery cell C 1  to the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 1  and the battery cell C 2  is I 1   1  equal to the constant current I 0   11  due to the constant current source I 0   11 . A current I 2   2  generated flowing through the Zener diode  32   2  from the constant current source I 0   22  and flowing to the battery cell C 2  is I 2   2  equal to the constant current I 0   22  due to the constant current source I 0   22 . Similarly, a current I 2   1  flowing from the battery cell C 2  to the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 2  and the battery cell C 3  is I 2   1  equal to the constant current I 0   12  due to the constant current source I 0   12 . A current I 3   2  generated flowing through the Zener diode  32   3  from the constant current source I 0   23  and flowing into the battery cell C 3  is I 3   2  equal to the constant current I 0   23  due to the constant current source I 0   23 . 
         [0058]    If the current values of the constant current sources I 0   11 , I 0   12  and I 0   13  and the constant current sources I 0   21 , I 0   22  and I 0   23  are all equal (the constant current I 0 ), then I 1   1 , I 2   1 , I 2   2  and I 3   2  are all equal at the constant current I 0 , regardless of the battery voltages of the battery cells C (C 1 , C 2  and C 3 ). 
         [0059]    Thus, the current values of current I 1   1  and current I 2   2  in the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 1  and the battery cell C 2  are equal, being the constant current I 0 , and the directions of flow are opposite. Therefore, current I 1   1  and current I 2   2  cancel out, current flowing through the resistor R 1  is substantially zero, and there is no voltage drop across the resistor R 1 . Similarly, the current values of current I 2   1  and current I 3   2  in the resistor R 1  of the noise removal filter  14  that is connected between the battery cell C 2  and the battery cell C 3  are equal at the constant current I 0 , and the directions of flow are opposite. Therefore, current I 2   1  and current I 3   2  cancel out, current flowing through this resistor R 1  is substantially zero, and there is no voltage drop across the resistor R 1 . 
         [0060]    Now, consider a case in which only either the constant current sources I 0   1  or the constant current sources I 0   2  are provided; for example, a case in which only the constant current sources I 0   1  are provided. This mode corresponds to the conventional technology recited in the above-mentioned Japanese Patent Application Laid-Open (JP-A) No. 2010-281805. In this case, the currents flowing out from the battery cells C (I 1   1 , I 2   1  and I 3   1 ) are all at the constant current I 0 , and are all equal. However, the currents flowing from the comparators  30  (from the reference voltage generation sources) to the battery cells C (I 2   2  and I 3   2 ) are not constant but vary in accordance with the battery voltages of the battery cells C. Therefore, the currents flowing through the resistors R 1  do not cancel out and do not go substantially to zero, and there may be voltage drops across the resistors R 1 . Similarly, in a case in which only the constant current sources I 0   2  are provided, the currents flowing through the resistors R 1  do not cancel out and do not go substantially to zero, and there may be voltage drops across the resistors R 1 . Thus, currents flowing through the resistors R 1  may cancel out and go substantially to zero, and voltage drops across the resistors R 1  may be avoided by both the constant current sources I 0   1  and the constant current sources I 0   2  being provided as in the present exemplary embodiment. 
         [0061]    According to this present exemplary embodiment, the battery monitoring system is structured such that each resistor Ra and constant current source I 0   1  are connected in series between the high potential side line  1  of the respective battery cell C and ground GND, and the voltage of the junction between the resistor Ra and the constant current source I 0   1  is inputted to the non-inverting terminal of the comparator  30 . Furthermore, the battery monitoring system is structured that each constant current source I 0   2  and Zener diode  32  are connected in series between the power supply line VDD and the low potential side line  1  of the battery cell C, and the reference voltage generated by the constant current IO and the Zener diode  32  is inputted to the inverting terminal of the comparator  30 . The constant currents provided by the constant current sources I 0   1  and the constant current sources I 0   2  are all equal (the constant current I 0 ). 
         [0062]    Thus, the voltages inputted to the comparators  30  and the reference voltages are generated by constant current consumption (the constant current sources I 0 ) with no dependence on the battery voltages of the battery cells C. Therefore, the currents flowing to the battery cells C and the currents flowing from the battery cells C are always at the constant current I 0 . Thus, in the resistors R 1 , the constant currents I 0  flow in mutually opposite directions and cancel out, and the currents are substantially at zero. Consequently, voltage drops across the resistors R 1  do not occur and there are no differences between the input voltages V of the voltage detection circuits  20  and the battery voltages of the battery cells C. Therefore, even if a battery voltage of the batteries C (C 1 , C 2  or C 3 ) is inconsistent, the battery voltages of the battery cells C may be detected accurately. 
         [0063]    In the present exemplary embodiment, the constant current sources I 0   1  all generate the constant current I 0  by reference to the ground potential (GND), and the constant current sources I 0   2  all generate the constant current IO by reference to the potential of the power supply voltage (VDD). 
         [0064]    Therefore, a constant current source I 0   1  and a constant current source I 0   2  that are shared by the battery cells C may be used. For example, if a constant current source is provided separately in the semiconductor device  16 , constant currents I 0  generated by this constant current source may be utilized. In contrast, in the first exemplary embodiment, because each constant current source I 0  generates the constant current I 0  by reference to the potential of the lower potential side of the respective battery cell C, a constant current source I 0  is needed for each of these potentials, which is to say, for each of the battery cells C. Therefore, the present exemplary embodiment provides an effect in that circuit size may be reduced. 
         [0065]    In the present exemplary embodiment, the Zener diodes  32  are used as reference voltage sources for the comparators  30 , but this is not a limitation. Diodes and resistors may be used, and resistors alone may be used. 
         [0066]    In the exemplary embodiments described above, each resistor Ra is connected to the positive terminal (higher potential) of the battery cell C, and the reference voltage of the comparator is connected to the negative terminal (lower potential) of the battery cell C. However, this is not a limitation and the two may be arranged the other way round. 
         [0067]    In the exemplary embodiments described above, the MCU  22  is provided inside the semiconductor device  16  together with the voltage detection circuits  20 , but this is not a limitation. The MCU  22  may be formed in a separate circuit (chip). Furthermore, the noise removal filter  14  is provided outside the semiconductor device  16  but this is not a limitation, and the noise removal filter  14  may be formed in the same circuit (chip). 
         [0068]    In the exemplary embodiments described above, cases are described in which the voltage detection circuits  20  are provided one for each battery cell C of the battery cell group  12 , but this is not a limitation. For example, a single voltage detection circuit  20  may be provided for the battery cell group  12 , and a battery cell C whose battery voltage is to be detected may be connected with this voltage detection circuit  20  by suitable switching elements or the like. 
         [0069]    It will be clear to those skilled in the art that the structures, operations and the like of the battery monitoring system  10 , semiconductor device  16 , voltage detection circuit  20  and so forth described in the above exemplary embodiments are examples and may be suitably modified in accordance with circumstances within a scope not departing from the spirit of the present invention.