• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a voltage comparator having a hysteresis characteristic designed to design an accurate hysteresis voltage, the constant current source being operated when the output voltage is high to output a predetermined constant current; A comparator for comparing a predetermined reference voltage with an input voltage; A current mirror provided to a load of the comparator and changing an output current value of the comparator to a first current value and a second current value in response to an output current of the constant current source; And an output buffer for hysterically driving the output voltage in response to the first and second current values.
    公开号:KR19980055006A
    申请号:KR1019960074212
    申请日:1996-12-27
    公开日:1998-09-25
    发明作者:김동훈
    申请人:김광호；삼성전자 주식회사；
    IPC主号:
    专利说明:

    Voltage comparator with hysteresis characteristics
    The present invention relates to a voltage comparator having hysteresis characteristics, and more particularly, to a voltage comparator having hysteresis characteristics designed to design an accurate hysteresis voltage.
    1 is a diagram showing a circuit diagram of a comparator according to the prior art. The conventional hysteresis characteristic HYSTERESIS has a voltage divider (DIVIDER) consisting of resistors R3, R4, and R5, a voltage comparator capable of comparing an input voltage with a reference voltage, and a resistor R6 capable of generating hysteresis voltage. , Transistor Q4.
    The operation principle of this circuit is as follows. Compare the reference voltage of the voltage divider consisting of resistors R3, R4, and R5 with the input voltage of the voltage comparator, and when the input voltage increases and exceeds the reference voltage, transistor Q5 is turned on and transistors Q4 and Q6 are turned on and resistor R5 The parallel resistance of and R6 is formed, so that the reference voltage of the voltage comparator is set lower than the initial setting value, thereby forming the hysteresis voltage. Thus, even if the input voltage is lowered again, the output voltage of transistor Q6 can be kept low by the hysteresis voltage. In such a structure, it is difficult to design an accurate hysteresis voltage because a design considering the saturation voltage relationship of transistor Q4 is required.
    An object of the present invention is to provide a voltage comparator having hysteresis characteristics designed to design an accurate hysteresis voltage.
    In order to achieve the above object, a voltage comparator having a hysteresis characteristic according to the present invention includes a constant current source operated when the output voltage is high to output a predetermined constant current; A comparator for comparing a predetermined reference voltage with an input voltage; A current mirror provided to a load of the comparator and changing an output current value of the comparator to a first current value and a second current value in response to an output current of the constant current source; And an output buffer for hysterically driving the output voltage in response to the first and second current values.
    1 is a circuit diagram of a comparator according to the prior art.
    2 is a circuit diagram of a comparator according to the present invention.
    3 is a diagram illustrating an output waveform according to the circuit of FIG. 2.
    Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
    FIG. 2 is a circuit diagram of a comparator according to the present invention, and FIG. 3 is a diagram showing an output waveform according to the circuit shown in FIG.
    The circuit shown in FIG. 2 is a constant current source 10 consisting of transistors Q11, Q12, Q13, Q14, Q15, Q16 and resistor R11, transistors Q2, Q5, Q6, and resistor R7 so that the magnitude of the reference voltage and the input voltage can be compared. Comparator 20 is configured to provide a load of the comparator 20, the output current value of the comparator 20 in response to the output current of the constant current source 10 to the first current value and the second current value A current mirror 30 composed of transistors Q7, Q8, resistors R1, R2, transistors Q3, Q4, Q9, Q10 to hysterically drive the output voltage in response to the first and second current values And an output buffer 40 composed of resistors R5 and R6. The circuit composed of the resistors R8, R4 and the transistor Q1 constitutes a current mirror with transistors Q2 of the comparator 20 and transistors Q3, Q4 of the output buffer 40 to set a constant current.
    The comparator 20 is connected between the emitter constant current sources Q2 and R7 connected between the power supply voltage Vcc and the first node N1, and between the first node N1 and the second node N2. The first transistor Q5 of the first conductivity type and pnp type, to which the reference voltage Vref is applied to the base, is connected between the first node N1 and the third node N3 and the input voltage Vin ) Includes a second transistor Q6 of the first conductivity type applied to the base.
    The current mirror 30 is connected to the second node N2 and the fourth node N4, and the first transistor Q8 of npn, whose second base is connected to the third node N3, A second transistor Q7 of the second conductivity type connected between the third node N3 and the fifth node N5 and a base connected to the third node N3, and the fourth node N4. The first resistor R2 is connected between ground, and the second resistor R1 is connected between the fifth node N5 and ground.
    The output buffer 40 includes a third transistor Q9 of a second conductivity type having a base connected to the second node N2, supplied with constant current (provided by Q3 and R6) to the collector, and having an emitter grounded. And a fourth transistor (Q10) of the second conductivity type having a base connected to the collector of the third transistor (Q9), a constant current (provided by Q4, R5) supplied to the collector, and an emitter grounded.
    Looking at the operation of this circuit, if the input voltage is increased by comparing the input voltage (Vin) and the reference voltage (Vref) of the comparator 20, if the input voltage is higher than the reference voltage, the collector current of Q5 increases, but most of them to ground through Q8 Since the base current of Q9 flows less to the first current value, the input voltage is sufficiently higher than the reference voltage so that the base current of Q9 is increased so that the output voltage of the output buffer 40 is inverted from a low state to a high state. . When the output voltage is inverted to the high state, the constant current source 10 is operated so that the output current of the constant current source is supplied to the fourth node N4, so that the base current of Q9 is further increased, and the output voltage remains high. Will be.
    On the contrary, when the input voltage is lower than the reference voltage, the collector current of Q6 increases, so that the current capability to sink in Q8 increases, but since the output current of the constant current source is being provided to the fourth node, it is charged to the second node. Since the charge cannot escape through Q8 at high speed, the output voltage does not fall low and remains high. As the collector voltage of Q6 further decreases as the input voltage continues to drop, the current sinking capability of Q8 also increases, so even if the current of the constant current source is supplied to the fourth node N4, the charge of the second node N2 is now Since it is somehow lost through Q8, the output voltage of the output buffer 40 falls to a low state. Therefore, since the operation of the constant current source is turned off and the charge of the second node is quickly discharged through Q8, the output voltage of the output buffer 40 is kept low.
    As described above, in the present invention, since the output voltage is inverted from the low state to the high state at an input voltage higher than the reference voltage, and the output voltage is inverted from the high state to the low state at an input voltage lower than the reference voltage, there is a hysteresis characteristic. The two pointer values of the hysteresis of the present invention can be arbitrarily adjusted by the designer as the current value of the constant current source, so that the hysteresis voltage pointer can be set very accurately and precisely.
    As described above, according to the voltage comparator having hysteresis characteristics according to the present invention, the hysteresis voltage can be accurately designed because the constant current value can be adjusted without considering the saturation relationship by the transistor in the circuit. have.
    权利要求:
    Claims (4)
    [1" claim-type="Currently amended] A constant current source operated when the output voltage is high to output a predetermined constant current;
    A comparator for comparing a predetermined reference voltage with an input voltage;
    A current mirror provided to a load of the comparator and changing an output current value of the comparator to a first current value and a second current value in response to an output current of the constant current source;
    And an output buffer for hysterically driving the output voltage in response to the first and second current values.
    [2" claim-type="Currently amended] 2. The apparatus of claim 1, wherein the comparator comprises: an emitter constant current source coupled between the power supply voltage and the first node;
    A first transistor of a first conductivity type connected between the first node and a second node and having the reference voltage applied to a base; And
    And a second transistor of a first conductivity type connected between the first node and a third node and to which the input voltage is applied to a base.
    [3" claim-type="Currently amended] The method of claim 2, wherein the current mirror
    A first transistor of a second conductivity type coupled to the second and fourth nodes and having a base connected to the third node;
    A second transistor of a second conductivity type connected between the third node and a fifth node and having a base connected to the third node;
    A first resistor coupled between the fourth node and ground;
    A second resistor connected between the fifth node and ground;
    And the output current of the constant current source is supplied to the fourth node.
    [4" claim-type="Currently amended] 4. The transistor of claim 3, wherein the output buffer comprises: a third transistor of a second conductivity type having a base connected to the second node, a constant current supplied to the collector, and an emitter grounded; And
    And a fourth transistor of a second conductivity type having a base connected to the collector of the third transistor, a constant current supplied to the collector, and an emitter grounded, and an output terminal connected to the collector of the fourth transistor.
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    同族专利:
    公开号 | 公开日
    KR100212155B1|1999-08-02|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1996-12-27|Application filed by 김광호, 삼성전자 주식회사
    1996-12-27|Priority to KR1019960074212A
    1998-09-25|Publication of KR19980055006A
    1999-08-02|Application granted
    1999-08-02|Publication of KR100212155B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019960074212A|KR100212155B1|1996-12-27|1996-12-27|Voltage comparator equipped by hysteresis|
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