Current detection circuit and semiconductor integrated circuit for power supplies

Abstract

To provide a current detection circuit capable of applying a hysteresis to a comparing action of an abnormal detection comparator whose object of detection is a current.SOLUTION: A current detection circuit includes a current-to-voltage conversion element that converts an object-of-detection current to a voltage, a comparator that inputs a detection voltage, which results from the conversion, through one of input terminals and inputs a comparison reference voltage through the other input terminal, and a hysteresis application circuit that applies a hysteresis to a comparing action of the comparator. The hysteresis application circuit includes a current source circuit that generates a current of a predetermined magnitude which is added to or subtracted from the current that is an object of detection, and a switch element connected in series with the current source circuit. When the switch element is turned on or off with an output of the comparator, a current flowing into the current-to-voltage conversion element augments or diminishes. Accordingly, the detection voltage varies relatively to the comparison reference voltage. Thus, a hysteresis is applied to the comparing action of the comparator.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a current detection circuit that uses a comparator to detect the magnitude of a current, and a power supply semiconductor integrated circuit (power supply IC) that has the same built in, and relates to a technology that is effective when used in a power supply semiconductor integrated circuit that has, for example, multiple output terminals to which loads are connected and has a function of detecting open or short abnormalities in the multiple output terminals or the loads using a current detection circuit. [Background technology]

[0002] In automobiles equipped with digital terrestrial (terrestrial digital television broadcasting) tuners, power is supplied to the vehicle's electronic devices, such as the antenna for digital terrestrial broadcasting, by an on-board regulator. In addition, in on-board digital terrestrial broadcasting tuners that support full-segment broadcasting, the tuner adjusts the reception sensitivity and switches between full-segment and one-segment broadcasting, and a diversity antenna, which is an equivalent antenna for 4ch (channels), is generally used as the antenna for digital terrestrial broadcasting to optimize reception conditions.

[0003] On the other hand, since in-vehicle tuners and antennas are connected to the in-vehicle regulator via a connector, vibrations of the vehicle body can cause the connector to come loose, opening the output terminal of the power supply, or causing a disconnection or short circuit inside the load. For this reason, some in-vehicle regulators are equipped with a function to detect such abnormal conditions. Patent Documents 1 and 2 describe inventions relating to a semiconductor integrated circuit for a regulator (regulator IC) configured to detect an open or short state of an output terminal, generate an abnormality detection signal, and output it from the output terminal.

[0004] Both of the inventions in Patent Documents 1 and 2 are configured as regulators capable of supplying power corresponding to two channels (hereinafter referred to as 2ch). Of these, the invention in Patent Document 1 is configured to set a threshold value for abnormality detection separately from two external terminals provided corresponding to the 2ch. Meanwhile, the invention in Patent Document 2 is configured to reduce the number of external terminals for setting the threshold value by using a common abnormality detection threshold value for the 2ch. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-45096 A [Patent Document 2] JP 2023-43049 A Summary of the Invention [Problem to be solved by the invention]

[0006] Both of the inventions in Patent Documents 1 and 2 use a comparator that detects an open or short state of the output terminal by comparing a voltage proportional to the output current with an externally set threshold voltage. Therefore, there is a problem that when the output current increases or decreases near the threshold due to noise, the output of the comparator repeatedly changes between high and low. In order to prevent such malfunctions due to noise, it is necessary to provide hysteresis to the comparison operation of the comparator. Incidentally, Patent Document 2 states that it is good to use a comparator having a hysteresis characteristic, but does not disclose a specific configuration for providing hysteresis. Furthermore, Patent Documents 1 and 2 disclose examples of regulators configured with MOS transistors, but do not disclose a specific example of regulators configured with bipolar transistors.

[0007] An object of the present invention is to provide a current detection circuit capable of imparting hysteresis to the comparison operation of a comparator whose detection target is a current, and a power supply semiconductor integrated circuit incorporating the same. Another object of the present invention is to prevent transistors constituting the hysteresis applying circuit of a current detection circuit in a power supply semiconductor integrated circuit composed of bipolar transistors and equipped with a current detection circuit which uses a comparator to detect an open or short state of an output terminal from operating in the saturation region. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides A current detection circuit comprising: a current-voltage conversion element for converting a current to be detected or a reference current into a voltage; a comparator having one input terminal to which the voltage obtained by the current-voltage conversion element is input, and having the other input terminal to which a voltage serving as a comparison reference or a voltage obtained by converting the current to be detected is input; and a hysteresis imparting circuit for imparting hysteresis to the comparison operation of the comparator, The hysteresis applying circuit includes: A current source circuit that generates a current of a predetermined magnitude, and a switch element that is connected in series with the current source circuit, The switch element is switched to an on or off state by the output of the comparator, thereby increasing or decreasing the current flowing through the current-voltage conversion element by the amount of the current in the current source circuit, and changing the voltage obtained by converting the current to be detected or the voltage obtained by converting the reference current, thereby imparting hysteresis to the comparison operation of the comparator. According to the current detection circuit having the above configuration, it is possible to impart hysteresis to the comparison operation of the comparator, which detects a current. Effect of the Invention

[0009] According to the present invention, it is possible to provide a current detection circuit capable of adding hysteresis to the comparison operation of a comparator whose detection target is a current, and a power supply semiconductor integrated circuit having the same built in. Also, in a power supply semiconductor integrated circuit comprising a current detection circuit that uses a comparator to detect an open state or short state of an output terminal and that is made up of bipolar transistors, it is possible to prevent the transistors constituting the hysteresis adding circuit of the current detection circuit from operating in the saturation region. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit configuration diagram showing a first example of a regulator IC according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a circuit configuration diagram showing a second example of the regulator IC according to the first embodiment to which the present invention is applied. [Diagram 3] FIG. 11 is a circuit configuration diagram showing a third example of the regulator IC according to the first embodiment to which the present invention is applied. [Figure 4] FIG. 11 is a circuit diagram showing a basic configuration of a regulator IC according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a circuit configuration diagram showing a first example of a regulator IC according to a second embodiment to which the present invention is applied. [Figure 6] FIG. 11 is a circuit configuration diagram showing a second example of a regulator IC according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a circuit configuration diagram showing a third example of the regulator IC according to the second embodiment to which the present invention is applied. [Figure 8] 1A and 1B are circuit diagrams showing the configuration of a hysteresis applying circuit in a current detection circuit devised by the present inventors prior to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. (First embodiment) Fig. 1 shows a circuit configuration of a first example of a first embodiment of the present invention when the present invention is applied to a series regulator as a DC power supply device. In Fig. 1, the part surrounded by a dashed line is formed as a semiconductor integrated circuit (hereinafter referred to as a regulator IC) 10 on a semiconductor chip such as single crystal silicon.

[0012] 1, the regulator IC10 of this embodiment is provided with one voltage input terminal IN to which a DC voltage VCC is applied and two output terminals OUT1, OUT2 as external terminals, PNP bipolar transistors Qp1, Qp2 are connected between the voltage input terminal IN and each output terminal OUT1, OUT2, and capacitors Co1, Co2 are connected to the output terminals OUT1, OUT2, so that the regulator IC10 functions as a DC power supply device that supplies two stable DC output voltages Vout1, Vout2 to the outside. LD1, LD2 represent load devices such as antennas connected to the output terminals OUT1, OUT2.

[0013] Resistors R11, R12 and resistors R21, R22 that divide the output voltages Vout1 and Vout2 are connected in series between the output terminals OUT1, OUT2 and a ground line to which the ground potential GND is applied. When an external terminal connected to the midpoint of the resistors R11 and R12 or the midpoint of the resistors R21 and R22 is separately provided, R11, R12, R21, and R22 can be provided outside the regulator IC10.

[0014] The voltage VFB1 divided by the output voltage dividing resistors R11 and R12 is fed back to the non-inverting input terminal of an error amplifier 11A as an error amplifier circuit that controls the base terminal of the transistor Qp1, and the voltage VFB2 divided by the resistors R21 and R22 is fed back to the non-inverting input terminal of an error amplifier 11B that controls the base terminal of the transistor Qp2. The error amplifiers 11A and 11B control the transistors Qp1 and Qp2 according to the potential difference between the output feedback voltages VFB1 and VFB2 and a predetermined reference voltage Vref, so that a current according to the load flows and the output voltages Vout1 and Vout2 are controlled to the desired potential. As a result, the transistors Qp1 and Qp2 function as a current control element and a voltage control element.

[0015] Furthermore, the regulator IC10 of this embodiment is provided with a reference voltage circuit 12 for generating a reference voltage Vref to be applied to the inverting input terminals of the error amplifiers 11A and 11B, and a bias circuit 13 for supplying operating current to the error amplifiers 11A and 11B and the reference voltage circuit 12. The reference voltage circuit 12 can be composed of a bandgap reference circuit, a resistor and a Zener diode connected in series, or the like.

[0016] Furthermore, in the regulator IC10 of this embodiment, transistors Qs1 and Qs2 are provided in parallel with the current control transistors Qp1 and Qp2, which respectively form current mirror circuits with Qp1 and Qp2, and the same voltage as that applied to the base terminals of the transistors Qp1 and Qp2, that is, the output voltage of the error amplifiers 11A and 11B, is applied to the base terminals of these transistors Qs1 and Qs2 as control terminals. As a result, a current proportional to the collector currents of Qp1 and Qp2 (1 / N current) flows through Qs1 and Qs2 according to the element size ratio N.

[0017] Furthermore, the regulator IC10 of this embodiment is provided with resistors R31 and R32 connected in series with the current mirror transistors Qs1 and Qs2, respectively, as current-voltage conversion elements that convert the current flowing through Qs1 and Qs2 into a voltage, and the voltage converted by these resistors R31 and R32 is input to one input terminal of comparators CMP1 and CMP2 and compared with a threshold voltage Vth applied to the other input terminal. Therefore, the resistor R31 and the comparator CMP1 form a current detection circuit 14A, and the resistor R32 and the comparator CMP2 form a current detection circuit 14B.

[0018] In addition, hysteresis applying circuits 17A and 17B are provided corresponding to the current detection circuits 14A and 14B for applying hysteresis to the comparison operation of the comparators CMP1 and CMP2 by increasing or decreasing the current flowing through the transistors Qs1 and Qs2 according to the output state of the comparators CMP1 and CMP2. The specific configuration and operation of the hysteresis applying circuits 17A and 17B will be described in detail later.

[0019] In addition, an external terminal P1 is provided for connecting a resistor Rdet that performs voltage-current conversion outside the chip, a voltage converter 15 generates a voltage Vth corresponding to the voltage Vdet generated at the external terminal P1, and the voltage Vth generated by the voltage converter 15 is compared with the voltage converted by the resistors R31 and R32 by comparators CMP1 and CMP2 to detect either an open circuit or a short circuit in the output terminals OUT1 and OUT2. Therefore, the voltage Vth serves as a threshold for determining whether an open circuit or a short circuit is present. Although Figures 1 to 7 show circuit configurations for detecting either an open circuit abnormality or a short circuit abnormality as embodiments of the present invention, it is also possible to configure the circuit so as to detect both an open circuit abnormality and a short circuit abnormality in transistors Qp1 and Qp2.

[0020] When the comparators CMP1 and CMP2 are made to function as an open anomaly detection means, a voltage is generated at one of the input terminals (+ or -) of the comparators CMP1 and CMP2 by flowing the currents Iout1' and Iout2' of Qs1 and Qs2 through resistors R31 and R32, and a threshold voltage Vtho is generated at the other input terminal (- or +). On the other hand, when comparators CMP1 and CMP2 are made to function as short circuit anomaly detection means, a voltage is generated at one input terminal (- or +) of comparators CMP1 and CMP2 by flowing currents Iout1' and Iout2' of Qs1 and Qs2 through resistors R31 and R32, and a threshold voltage Vths is generated at the other input terminal (+ or -). The inverting / non-inverting input terminals (- or +) of the comparators CMP1 and CMP2 to which Vtho or Vths is input can be either one depending on the logic of the subsequent logic circuit 16. Therefore, in FIG. 1, the symbols "+" or "-" attached to the input terminals of the comparators CMP1 and CMP2 are omitted.

[0021] Here, if Vth, Vtho, or Vths is too high or too low, it may be subject to restrictions due to the input dynamic range of the comparators CMP1 and CMP2. Also, if it is too low, the voltage generated across resistors R4, R31, and R32 will be small, which poses an issue in terms of accuracy. Therefore, when comparators CMP1 and CMP2 are used as an open anomaly detection means, since the current flowing through transistor Qp1 or Qp2 is small, it is desirable to set the current mirror ratio m of transistors Qp1 and Qs1, or transistors Qp2 and Qs2, to be small and to make the current flowing through transistor Qs1 or Qs2 relatively large so that Vtho does not become too small. On the other hand, when comparators CMP1 and CMP2 are used as short circuit anomaly detection means, since a large amount of current flows through transistor Qp1 or Qp2, it is desirable to set the current mirror ratio m of transistors Qp1 and Qs1, or transistors Qp2 and Qs2, to be large and to set the current flowing through transistor Qs1 or Qs2 to be relatively small so that Vths does not become too large.

[0022] Furthermore, the regulator IC10 of this embodiment is provided with a logic circuit 16 that receives the outputs of the above-mentioned abnormality detection comparators CMP1, CMP2 as input, and an external terminal P2 that outputs a signal ERR indicating that the comparators CMP1, CMP2 have detected an abnormality. 1 shows a configuration in which the output of the logic circuit 16 is directly output from the external terminal P2, but an NPN bipolar transistor may be provided in which the output of the logic circuit 16 is input to the base terminal and the collector terminal is connected to the external terminal P2, and the abnormality detection signal ERR may be output in an open collector format to an external CPU, etc. Also, instead of an open collector type transistor, an output circuit consisting of an emitter follower may be provided.

[0023] The logic circuit 16 is configured as a circuit having an OR logic function when the outputs of the anomaly detection comparators CMP1, CMP2 are at a high level to indicate an abnormal state and output a low-level abnormality detection signal ERR, a circuit having a NAND logic function when the outputs of the anomaly detection comparators CMP1, CMP2 are at a low level to indicate an abnormal state and output a low-level abnormality detection signal ERR, and a circuit having a NOR logic function when the outputs of the CMP1, CMP2 are at a low level to indicate an abnormal state and output a high-level abnormality detection signal ERR.

[0024] Furthermore, two external terminals for outputting an abnormality detection signal may be provided so that a 2-bit abnormality detection signal corresponding to the outputs of the comparators CMP1 and CMP2 is output to the outside, and in this case, the logic circuit 16 may be configured as, for example, a delay circuit.

[0025] As described above, in the regulator IC10 of this embodiment, when the same load is connected to the output terminals OUT1 and OUT2, an open circuit or short circuit can be detected simply by providing one external terminal to which the external resistor Rdet is connected. This also allows the chip size to be reduced. Furthermore, by reducing the number of terminals and components, a small and inexpensive package can be used, thereby achieving space saving and cost reduction of the power supply device. In addition, the threshold value for detecting an open circuit or short circuit can be easily changed by changing the resistance value of the external resistor Rdet, thereby expanding the range of uses of the IC. Furthermore, since the hysteresis applying circuits 17A and 17B are provided and the comparators CMP1 and CMP2 are configured to perform hysteresis operation, it is possible to prevent the current detection circuits 14A and 14B from malfunctioning due to noise. Moreover, the hysteresis can be set separately for the current detection circuits 14A and 14B.

[0026] Next, a specific circuit of voltage converter 15 and hysteresis applying circuits 17A and 17B in the IC will be described. First, as shown in FIG. 1, the voltage converter 15 includes a current buffer 15a consisting of an amplifier AMP having an inverting input terminal connected to the external terminal P1 to which the resistor Rdet is connected and a non-inverting input terminal to which a reference voltage Vref is applied, and an NPN bipolar transistor Q0 having an emitter terminal connected to the external terminal P1 and a base terminal to which the output voltage of the amplifier AMP is applied, a current mirror circuit 15b that reflects a current I1 generated by the current buffer 15a and passed through the resistor Rdet, and a resistor Rth that converts a current (transfer current) I2 on the secondary side of the current mirror circuit 15b into a voltage, and is configured so that the voltage converted by the resistor R4 is supplied to the comparators CMP1 and CMP2 as a threshold voltage Vth for comparison and judgment.

[0027] In the current buffer 15a of the voltage converter 15, the output terminal of the amplifier AMP is connected to the base terminal of the NPN bipolar transistor Q0, and the emitter terminal of the transistor Q0 is connected to the inverting input terminal of the amplifier AMP. This causes the amplifier AMP to function as a voltage follower, and operates the transistor Q0 so that the emitter voltage of the transistor Q0 (the potential of the external terminal P1) becomes equal to the input voltage of the non-inverting input terminal (reference voltage Vref). The amplifier AMP can be configured as a typical differential amplifier circuit consisting of a pair of differential input transistors whose base terminals receive the reference voltage Vref and the voltage Vdet of the external terminal P1, a pair of load transistors, and a constant current source (or resistor), and operates as a current buffer that passes a predetermined collector current through transistor Q0.

[0028] On the other hand, the current mirror circuit 15b is composed of a PNP bipolar transistor Q1 connected in series with the collector terminal of the transistor Q0, a PNP bipolar transistor Q2 connected in a current mirror with the transistor Q1, and a resistor R4 connected to the collector terminal of the transistor Q2, and a voltage converted into a current-voltage by the resistor R4 is supplied to the comparators CMP1 and CMP2 as a threshold voltage Vth. Therefore, the current buffer 15a and the transistors Q1 and Q2 constituting the current mirror circuit 15b constitute a reference current generating circuit that generates a current that serves as a reference for comparison in the current detection circuits 14A and 14B.

[0029] Here, the characteristics of the voltage converter 15 will be described. In the voltage converter 15 of this embodiment, the voltage Vdet at the external terminal P1 is equal to the reference voltage Vref, that is, Vdet=Vref, due to the function of the current buffer 15a. Therefore, the current I1 flowing through the external resistor R4 by the current buffer 15a is I1=Vdet / Rdet=Vref / Rdet Therefore, the comparison reference voltage Vth generated by conversion by the resistor R4 through which the current I2, which is the current I1 folded back by the current mirror circuit 15b, flows is expressed by the following equation (1), where m is the current mirror ratio. Vth=R4*I2=R4*I1 / m ……(1) It is expressed as:

[0030] On the other hand, the output current Iout1 of the output terminal OUT1 is converted to a voltage Vout1' by passing a current Iout1' generated by a current mirror (n) of transistors Qp1 and Qs1 through a resistor R31. Therefore, if the ratio of Qp1 to Qs1 is n, then the following equation (2) is satisfied: Vout1'=R31*Iout1'=R31*Iout1 / n ……(2) This can be expressed as: The comparator CMP1 detects an abnormality by comparing the voltage given by the above formula (1) with the voltage given by formula (2). When the comparator CMP1 is used as an open abnormality detection means, the threshold voltage can be set by connecting an external resistor Rdet having a resistance value such that Vth=Vtho to the external terminal P1, and a regulator IC that detects an open circuit when Vout1'≦Vtho can be realized. When the comparator CMP1 is used as a short abnormality detection means, the threshold voltage can be set by connecting an external resistor Rdet having a resistance value such that Vth=Vths to the external terminal P1, and a regulator IC that detects a short circuit when Vout1'≧Vths can be realized.

[0031] Here, the IC's internal resistors R31 and R4 are both on-chip elements, so the relative ratio is good (about ±0.5%) and variations in temperature characteristics due to manufacturing variations are cancelled out. On the other hand, the reference voltage Vref of the voltage converter 15 can generate a highly accurate reference voltage using a band gap or the like, and the external resistor Rdet is a discrete component with good accuracy and temperature characteristics, and it is possible to manufacture or obtain one with high accuracy (resistance accuracy of about ±1%, temperature characteristics of about ±100 ppm / °C). Therefore, it is possible to set a highly accurate comparison reference voltage Vth, and the accuracy of open circuit or short circuit anomaly detection can be improved.

[0032] The same applies to the output current Iout2 of the output terminal OUT2, and highly accurate open circuit or short circuit detection can be performed by the voltage converter 15 and comparator CMP2. If the loads connected to the output terminals OUT1 and OUT2 have the same characteristics and pass the same current, the same comparison reference voltage Vth can be used for the comparators CMP1 and CMP2, so that the voltage converter 15 can be shared as in the regulator IC10 of this embodiment, and the comparison reference voltage Vth can be set by providing one external terminal P1 and one external resistor Rdet.

[0033] Next, the configuration and operation of the hysteresis applying circuits 17A and 17B will be described. In developing a regulator composed of bipolar transistors, the inventors of the present invention have studied a hysteresis circuit suitable for bipolar circuits. However, while a method of switching the threshold voltage can be relatively easily implemented to provide hysteresis to a comparator, when a common abnormality detection threshold is used for two channels as in the invention of Patent Document 2, the method of switching the threshold voltage cannot be applied. Therefore, the inventors have devised a method of switching the input voltage or current on the other detection target side of the comparator.

[0034] 8(A) and (B) show the hysteresis applying circuit that the present inventors initially conceived. Of these, the circuit in FIG. 8(A) is a voltage switching type hysteresis applying circuit in which a hysteresis resistor Rh is provided in series with a sense resistor Rs that converts a proportional current Iout' of Iout, which is connected in series with an output control transistor Qp that flows an output current Iout and a current mirror-connected detection current generating transistor Qs, and a switching transistor Qsw is provided in parallel with the resistor Rh.

[0035] On the other hand, the circuit in FIG. 8(B) is a current switching type hysteresis applying circuit in which a hysteresis transistor Qh and a switching transistor Qsw are provided in parallel with a detection current generating transistor Qs, which is current mirror connected to an output control transistor Qp. 8(A) and (B), the switching transistor Qsw is turned on or off by the output of the comparator CMP, which provides hysteresis to the current to be detected.

[0036] In the circuit of FIG. 8(A), when the switching transistor Qsw is in the off state, the input voltage to the comparator CMP is the current Iout' multiplied by the resistance value of resistors Rs and Rh. When the transistor Qsw is on, the collector-emitter voltage of Qsw is ideally 0, and the input voltage to the comparator CMP is the current Iout' multiplied by the resistance value of resistor Rs, Iout' x Rs. However, below the saturation voltage Vsat of the transistor, Qsw enters the saturation region, so the collector voltage does not go below Vsat. Therefore, the input voltage to the comparator is not the current Iout' multiplied by the resistance value of resistor Rs, but Iout' x Rs + Vsat.

[0037] On the other hand, even in the circuit of Fig. 8(B), the amount of current when the transistors Qsw and Qh enter the saturation region is different from the amount of current in the active region, so it no longer functions as a circuit that imparts a certain hysteresis to the current to be detected. In regulators such as LDOs, the input-output voltage is often used with a small potential difference between the collector and emitter of the output control transistor Qp to increase power efficiency, and inevitably the collector-emitter voltage of the transistor Qs for generating the detection current is often used under conditions of a small potential difference as well. Therefore, even in the hysteresis imparting circuit of Fig. 8(B), there is a problem that the transistors Qsw and Qh are very likely to operate in the saturation region.

[0038] 1, the hysteresis applying circuit 17A in the regulator IC of this embodiment includes PNP bipolar transistors Qh11 and Qh21 that form a current mirror circuit with the transistors Qp1 and Qs1 that form the current detection circuit 14A, and NPN bipolar transistors Qh41 and Qh31 that are connected in series with the transistors Qh11 and Qh21, respectively, and the bases of the transistors Qh31 and Qh41 are connected to each other so as to form a current mirror circuit, and the base terminal and collector terminal of Qh31 are connected. A switch transistor Qsw1 for switching hysteresis is connected between the common base terminal of the transistors Qh31 and Qh41 and the ground point, and the output voltage of the corresponding comparator CMP1 is applied to the base terminal of the transistor Qsw1.

[0039] In the hysteresis applying circuit 17A having the above configuration, when the switching transistor Qsw1 is in the ON state, the current Isns1 flowing through the resistor R31 is Isns1=Iout1'+Ihys11, where 10'Ihys11 is the current flowing through the transistor Qh11. The output of the comparator CMP1 is input to the base terminal of the transistor Qsw1, and Qsw1 is switched to the OFF state when a detection operation is performed. Then, when the current flowing through the transistor Qh21 is Ihys21, the current flowing through the resistor R31 when Qsw1 is in the OFF state is Isns1=Iout1'+Ihys11-Ihys21. Therefore, when the current detection circuit is used as an open circuit abnormality detection circuit, an open circuit state is detected when Vth≦R31×(Iout1'+Ihys11-Ihys21), and the detection of the open circuit state is released when Vth≧R31×(Iout1'+Ihys11).On the other hand, when the current detection circuit is used as a short circuit detection circuit, a short circuit state is detected when Vth≧R31×(Iout1'+Ihys11), and the detection of the short circuit state is released when Vth≦R31×(Iout1'+Ihys11-Ihys21).

[0040] By operating as described above, the detection current value differs when the comparator CMP1 performs detection and release operations, which is equivalent to relatively switching the threshold voltage Vth, and it is possible to impart hysteresis to the current detection circuit 14 A. In addition, the width of the hysteresis can be changed by adjusting the mirror ratio of the transistors Qh31 and Qh41 that form the current mirror. The hysteresis applying circuit 17B provided in correspondence with the other current detection circuit 14B constituted by the transistor Qs2, resistor R32 and comparator CMP2 has the same configuration as the hysteresis applying circuit 17A and performs the same operation as described above.

[0041] As described above, in the circuit of FIG. 8(B), the current of the hysteresis transistor Qh is directly turned on and off, so that the transistor operates in the saturation region and it is not possible to impart the desired hysteresis to the current to be detected. In contrast, according to the hysteresis imparting circuit 17A of the present embodiment configured as described above, the transistors Qh21, which are current sources, and the transistors Qh31 and Qh41, which copy the current of Qh21 by a current mirror, and the transistor Qsw, which plays a role in stopping the current flowing through Qh31 and Qh41, prevent Qh11 and Qh21 from operating in the saturation region, so that the desired current hysteresis can be imparted. This is also true for the hysteresis imparting circuit 17B. Note that when the regulator IC10 in FIG. 1 is configured with MOS transistors, there is no problem of saturation, so a hysteresis imparting circuit configured as shown in FIG. 8(B) may be used.

[0042] In the regulator IC10 of the embodiment shown in Fig. 1, when the threshold voltage Vth is low (for example, when the Vth is set low to detect an open circuit abnormality), the current detection circuits 14A and 14B operate with the upper end value of the voltage converted by the resistors R31 and R32 also low. In that case, the collector-emitter voltage of the transistors Qh41 and Qh42 may be insufficient, causing operation in the saturation region. Therefore, a regulator IC of the embodiment that takes measures against this is shown in Fig. 2.

[0043] The regulator IC10' of the second embodiment shown in Fig. 2 is configured by providing NPN transistors Q31, Q32, which function as diodes with their collectors and bases coupled, in series with the resistors R31, R32 between the ground and the current-voltage conversion resistors R31, R32 of the current detection circuits 14A, 14B in the regulator IC of the first embodiment shown in Fig. 1. Also, a diode-connected NPN transistor Q4 is provided in series with the resistor R4 between the ground and the resistor R4 on the secondary side of the voltage converter 15. Note that diode elements may be used instead of the transistors Q31, Q32, Q4.

[0044] In the regulator IC10' of the second embodiment, the provision of diode-connected transistors Q31 and Q32 ensures that the input voltages of comparators CMP1 and CMP2 (detection voltages converted by resistors R31 and R32) do not fall below the threshold voltages of the NPN transistors. This ensures that the collector-emitter voltages of transistors Qh41 and Qh42 are sufficiently high, preventing Qh41 and Qh42 from operating in the saturation region. Furthermore, by providing diode-connected transistor Q4 in voltage converter 15, the potential difference between the input voltages of comparators CMP1, CMP2 and threshold voltage Vth generated by voltage converter 15 does not change before and after transistors Q31, Q32 are provided. Additionally, even if the base-emitter voltages of transistors Q31, Q32 differ from IC to IC due to manufacturing variations, it is possible to avoid a decrease in detection accuracy caused by the base-emitter voltage of transistor Q4 varying in the same way.

[0045] However, since the circuit in Figure 2 raises the input voltage of comparators CMP1 and CMP2 by the forward voltage of the PN junction diode between the base and emitter generated in NPN transistors Q4, Q31, and Q32, it is desirable for the base-emitter voltages of Q4, Q31, and Q32 to be the same. In order to make the base-emitter voltages the same, it is important to match the ratio of the current flowing through transistors Q4, Q31, and Q32 to their driving capabilities. In addition, the driving capabilities of transistors vary depending on the manufacturing process, so consideration must be given to variations, such as by placing each transistor close to each other.

[0046] FIG. 3 shows a regulator IC according to an embodiment in which measures against the above-mentioned variations have been implemented. A regulator IC10" of a third embodiment shown in FIG. 3 omits Q31 and Q32 and provides only Q4, with the aim of standardizing the diode-connected transistors Q4, Q31, and Q32 that are provided in series with the current-voltage conversion resistors R4, R31, and R32 in the regulator IC of the second embodiment shown in FIG. 2. The ground side terminals of the resistors R4, R31, and R32 are connected to the collector terminal of the diode-connected transistor Q4, and the regulator IC is configured so that all of the current flowing through the resistors R4, R31, and R32 flows to the transistor Q4.

[0047] In the regulator IC10" of the third embodiment, the diode-connected transistor for preventing saturation is shared by the resistors R4, R31, and R32, so that it is inevitable that a difference in base-emitter voltage as in the second embodiment does not occur. The threshold value of the detection operation and release operation of the comparator CMP1 is determined by a comparison of the voltage of resistance R4×current I2 and the voltage of resistance R31×Isns1, and the threshold value of the operation and release operation of the comparator CMP2 is determined by a comparison of the voltage of resistance R4×current I2 and the voltage of resistance R32×Isns2. It is therefore possible to realize a current detection circuit that is not dependent on the variations in diode-connected transistors. However, because the diode-connected transistor is shared by the current detection circuits 14A and 14B, crosstalk may occur in which the operation of one current detection circuit affects the other current detection circuit.

[0048] Second embodiment Next, a second embodiment of the present invention applied to a series regulator will be described. Fig. 4 shows the basic circuit configuration of a regulator IC of the second embodiment, which shows the basic circuit configuration of the regulator IC before hysteresis is applied to the comparison operations of the comparators CMP1 and CMP2 constituting the current detection circuits 14A and 14B. Figs. 5 to 7 show an example in which a circuit for applying hysteresis to this basic circuit is provided. In the first embodiment, hysteresis is applied to the current side to be detected by the current detection circuits 14A and 14B, whereas the regulator in the example of the second embodiment shown in Figures 5 to 7 is characterized in that the circuit generating the threshold voltage Vth serving as the reference for comparison is formed by a current mirror circuit, and hysteresis is applied to the current flowing on the secondary side of the current mirror circuit. Note that the basic configuration of the circuit that applies hysteresis is the same in both the first and second embodiments.

[0049] The regulator IC shown in Fig. 4 includes a transistor Q21 on the secondary side constituting a current mirror circuit 15b of the voltage converter circuit 15, a resistor R41 that converts its current I21 into a voltage, and a transistor Q22 that constitutes a current mirror circuit with a primary side transistor Q1 and a resistor R42 that converts its current I22 into a voltage. The regulator IC is configured to supply the voltage converted by the resistor R41 to the comparator CMP1 of the current detection circuit 14A as a threshold voltage Vth1 for comparison and judgment, and to supply the voltage converted by the resistor R42 to the comparator CMP2 of the current detection circuit 14B as a threshold voltage Vth2 for comparison and judgment. Vth1 and Vth2 are independent of each other and can be set to different potentials, but may have the same voltage value.

[0050] The regulator IC10 shown in FIG. 5 is provided with hysteresis imparting circuits 17A', 17B' that impart hysteresis to comparators CMP1, CMP2 by changing the threshold voltages Vth1, Vth2 for comparison in the regulator IC of FIG. 4, and the configuration of the hysteresis imparting circuits 17A', 17B' is the same as the configuration of the hysteresis imparting circuits 17A, 17B shown in FIG. 1. Of these, the hysteresis applying circuit 17A' includes a transistor Q21 which forms a current mirror with the primary-side transistor Q1 of the current mirror circuit 15b, transistors Qh11 and Qh21 which are similarly current-mirror-connected with Q1, current-mirror transistors Qh41 and Qh31 which are connected in series with Qh11 and Qh21, and a switching transistor Qsw1 which is connected between the common base terminal of Qh41 and Qh31 and ground, and Qsw1 is configured so that it is turned on / off by the output of a comparator CMP1.

[0051] 5, it is possible to impart hysteresis to the comparator CMP1 by varying the threshold voltage Vth1, for example, Vth1=R42×(I21+Ihys11) when Qsw1 is on, and Vth1=R42×(I21+Ihys11-Ihys21) when Qsw1 is off. The same is true for the other hysteresis imparting circuit 17B' that imparts hysteresis to the comparator CMP2 of the current detection circuit 14B.

[0052] Furthermore, when threshold voltages Vth1, Vth2 are set to low values, there is a risk that transistors Qh41 and Qh42 constituting hysteresis imparting circuits 17A', 17B' may operate in the saturation region, similar to hysteresis imparting circuits 17A, 17B in regulator IC10 shown in Figure 1. Figure 6 shows regulator IC10' which takes measures to address this issue. In regulator IC10' of FIG. 6, diode-connected transistors Q41, Q31, and Q42, Q32 are provided in series with current-voltage conversion resistors R41, R42 of voltage converter 15 and current-voltage conversion resistors R31, R32 of current detection circuits 14A, 14B, respectively.

[0053] FIG. 7 shows a regulator IC according to an embodiment in which a measure is taken against the variations in diode-connected transistors in the regulator IC 10' of FIG. In a regulator IC10'' shown in FIG. 7, the diode-connected transistors Q41 and Q31 in FIG. 6 are combined into a common circuit, and the diode-connected transistors Q42 and Q32 are combined into a common circuit.

[0054] In this embodiment, as in the embodiment shown in FIG. 6, a diode-connected transistor Q41 is provided common to the current-voltage conversion resistors R31 and R41, and a diode-connected transistor Q42 is provided common to the resistors R32 and R42, thereby making it possible to prevent the transistors Qh41, Qh31 and Qh42, Qh32 constituting the hysteresis application circuits 17A', 17B' from operating in the saturation region while avoiding problems due to transistor variations. In addition, the regulator IC of the second embodiment shown in Figures 5 to 7 separately generates the comparison threshold voltages Vth1 and Vth2 used in the comparators CMP1 and CMP2, so there is no problem of crosstalk between the current detection circuits 14A and 14B in the regulator IC of the first embodiment.

[0055] Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiments, bipolar transistors are used as transistors constituting the internal circuit of the regulator IC10, but in the first example of the first embodiment (FIG. 1) and the first example of the second embodiment (FIG. 5), MOS transistors may be used instead of bipolar transistors. In the above embodiment, the regulator IC is applied to a two-channel regulator IC having two output terminals, but the number of channels is not limited to two and may be three or more. In particular, when the regulator IC has three or more channels, the signal indicating the detection of an abnormality output from the logic circuit 16 may be output as a two-bit or more signal.

[0056] Furthermore, in the regulator IC of the above embodiment, it has been described assuming a case where it is configured as an in-vehicle power supply device for terrestrial digital broadcasting with an antenna connected as a load to the output terminal OUT, but the load is not limited to an antenna, and the regulator IC can also be applied to a power supply device to which two or more loads with the same current consumption are connected. In the above embodiment, the present invention is described as being applied to a regulator IC that constitutes a linear regulator such as an LDO. However, the present invention is not limited to regulator ICs, and can also be applied to ICs that constitute switching regulator type DC-DC converters and high-side switch ICs. [Explanation of symbols]

[0057] 10...regulator IC, 11...error amplifier, 12...reference voltage circuit, 13...bias circuit, 14A, 14B...current detection circuit, 15...voltage converter, 15a...current buffer (voltage-current conversion circuit), 15b...current mirror circuit, 16...logic circuit, 17A, 17B...hysteresis applying circuit, CMP1, CMP2...open / short abnormality detection comparator, Qp1, Qp2...current control transistor, Qsw, Qsw1, Qsw2...switch transistor (switch element), P1...external terminal (terminal for connecting external resistor), P2...external terminal (detection signal output terminal)

Claims

1. A current detection circuit comprising: a current-voltage conversion element for converting a current to be detected or a reference current into a voltage; a comparator having one input terminal to which the voltage current-voltage converted by the current-voltage conversion element is input, and having the other input terminal to which a voltage serving as a comparison reference or a voltage obtained by converting the current to be detected is input; and a hysteresis imparting circuit for imparting hysteresis to a comparison operation of the comparator, The hysteresis applying circuit includes: A current source circuit that generates a current of a predetermined magnitude, and a switch element that is connected in series with the current source circuit, a current detection circuit characterized in that, when the switch element is switched to an on or off state by the output of the comparator, the current flowing through the current-voltage conversion element is increased or decreased by the amount of the current of the current source circuit, and the voltage converted from the current to be detected or the voltage converted from the reference current changes, thereby imparting hysteresis to the comparison operation of the comparator.

2. the detection target current or the reference current is caused to flow through the current-voltage conversion element by a first transistor, The hysteresis applying circuit includes: a second transistor and a third transistor, the second transistor and the third transistor each having a control terminal to which a voltage equal to that applied to a control terminal of the first transistor is applied, and each of the second transistor and the third transistor passes a current proportional to a current of the first transistor; a fourth transistor and a fifth transistor connected in series with the second transistor and the third transistor, respectively; 2. The current detection circuit according to claim 1, wherein the fourth transistor and the fifth transistor have their control terminals coupled to each other to form a current mirror circuit, and the switch element is connected between a junction node of the control terminals of the fourth transistor and the fifth transistor and a reference potential point.

3. the first to fifth transistors are composed of bipolar transistors, 3. The current detection circuit according to claim 2, wherein a PN junction rectifying element is connected between the switch element and the reference potential point so as to be in a forward direction toward the reference potential point.

4. A power supply semiconductor integrated circuit comprising: one input terminal and a plurality of output terminals; a plurality of current control transistors respectively connected between the input terminal and the plurality of output terminals; and a control circuit for controlling the plurality of current control transistors, a plurality of current detection circuits that convert currents proportional to the currents flowing to the plurality of output terminals by the plurality of current control transistors and a predetermined reference current into voltages and compare the voltages to detect an open state or a short state of each of the plurality of output terminals; An external terminal for connecting an external resistor; a reference current generating circuit that generates the reference current in response to a voltage of the external terminal that is generated by passing a current through the external resistor; The plurality of current detection circuits include a first transistor having a control terminal to which a voltage equal to that applied to a control terminal of the current control transistor is applied; a first current-voltage conversion element that converts a current flowing through the first transistor into a voltage; a comparator, one of whose input terminals receives the detection voltage converted by the first current-to-voltage conversion element, and the other of whose input terminals receives a voltage obtained by current-to-voltage conversion of the reference current as a comparison reference voltage; a hysteresis applying circuit for applying hysteresis to the comparison operation of the comparator, The hysteresis applying circuit includes: a current source circuit that generates a current of a predetermined magnitude to be added to or subtracted from a current flowing through the first transistor, and a switch element that is connected in series with the current source circuit; a switching element being switched to an on state or an off state by an output of a corresponding comparator, thereby increasing or decreasing a current flowing through the first current-voltage conversion element by an amount equivalent to a current of the current source circuit, and causing the detection voltage to change relatively to the comparison reference voltage, thereby imparting hysteresis to the comparison operation of the comparator.

5. The hysteresis applying circuit includes: a second transistor and a third transistor, the second transistor and the third transistor each having a control terminal to which a voltage equal to that applied to a control terminal of the first transistor is applied, and each of the second transistor and the third transistor passes a current proportional to a current of the first transistor; a fourth transistor and a fifth transistor connected in series with the second transistor and the third transistor, respectively; a current mirror circuit formed by coupling control terminals of the fourth transistor and the fifth transistor, and the switch element is connected between a coupling node of the control terminals of the fourth transistor and the fifth transistor and a reference potential point.

6. the first to fifth transistors are composed of bipolar transistors, 6. The power supply semiconductor integrated circuit according to claim 5, wherein a PN junction rectifier element is connected between the first current-voltage conversion element and the reference potential point provided in each of the current detection circuits so as to be in a forward direction toward the reference potential point.

7. a voltage-current conversion circuit that generates a current corresponding to the voltage of the external terminal or an external resistor connected to the external terminal, a current mirror circuit that transfers the current generated by the voltage-current conversion circuit, and a second current-voltage conversion element that converts an output current of the current mirror circuit into a voltage, the voltage converted by the second current-voltage conversion element being supplied to the plurality of current detection circuits as a comparison reference voltage; 7. The power supply semiconductor integrated circuit according to claim 6, wherein a common PN junction rectifier element is connected between the first current-voltage conversion element and the second current-voltage conversion element and the reference potential point so as to be in a forward direction toward the reference potential point.

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