Current detection circuit and semiconductor integrated circuit for power supply

Abstract

The invention provides a current detection circuit and a semiconductor integrated circuit for a power supply, which can impart a hysteresis to a comparison operation of an abnormality detection comparator in which a current is detected. A current detection circuit includes: a current-voltage conversion element that converts a current to be detected into a voltage; a comparator, one input terminal of which receives the converted detection voltage and the other input terminal of which receives a comparison reference voltage; and a hysteresis imparting circuit for imparting a hysteresis to the comparison operation of the comparator, the hysteresis imparting circuit comprising: a current source circuit for generating a current of a predetermined magnitude obtained by adding or subtracting the current to be detected; and a switching element connected in series to the current source circuit, the switching element being switched to an ON or OFF state in response to the output of the comparator, whereby the current flowing through the current-voltage conversion element increases or decreases, and the detection voltage changes relative to the comparison reference voltage, thereby imparting a hysteresis to the comparison operation of the comparator.

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 semiconductor integrated circuit for power supply (power supply IC) that has the current detection circuit built in. For example, it relates to a technology that is effectively used for a semiconductor integrated circuit for power supply, wherein the semiconductor integrated circuit for power supply has multiple output terminals connected to a load and has the function of using a current detection circuit to detect open circuit abnormalities or short circuit abnormalities of multiple output terminals or loads. Background Art

[0002] In a car equipped with a terrestrial digital (terrestrial digital television broadcasting) tuner, power is supplied to the terrestrial digital antenna and other on-board electronic equipment through the on-board tuner. In addition, in a full-band compatible on-board terrestrial digital tuner, in order to adjust the reception sensitivity and switch between full-band and single-band through the tuner to optimize the reception condition, a 4-channel (channel) equivalent antenna, that is, a diversity antenna, is generally used as a terrestrial digital antenna.

[0003] On the other hand, the on-board tuner and antenna are connected to the on-board regulator via a connector, so the connector may fall off due to the vibration of the vehicle body, and the output terminal of the power supply may become open, or a disconnection or short circuit may occur inside the load. Therefore, some on-board regulators have a function to detect such abnormal conditions.

[0004] Conventionally, there are inventions described in Patent Documents 1 and 2 as inventions related to a semiconductor integrated circuit for a regulator (regulator IC) configured to detect an open state or a short state of an output terminal, generate an abnormality detection signal, and output it from the output terminal.

[0005] The inventions of Patent Documents 1 and 2 are both configured as regulators capable of supplying power corresponding to two channels (hereinafter referred to as 2ch). Among them, the invention of Patent Document 1 can set the threshold value for abnormality detection from two external terminals provided corresponding to 2ch respectively. In addition, the invention of Patent Document 2 reduces the number of external terminals for setting the threshold value by using a common threshold value for abnormality detection for 2ch.

[0006] The inventions of Patent Documents 1 and 2 both use a comparator that compares a voltage proportional to the output current with a threshold voltage set externally to detect the open circuit state and short circuit state of the output terminal. Therefore, there is the following problem: when the output current increases or decreases near the threshold due to noise, the output of the comparator repeatedly changes to high / low. In order to prevent malfunction caused by such noise, it is necessary to make the comparison action of the comparator have hysteresis.

[0007] In addition, Patent Document 2 states that a comparator having a hysteresis characteristic can be used in the comparator, but does not disclose a specific structure for providing hysteresis. In addition, Patent Documents 1 and 2 disclose embodiments of a regulator composed of MOS transistors, but do not disclose a specific embodiment of a regulator composed of bipolar transistors.

[0008] Patent Document 1: Japanese Patent Application Publication No. 2017-45096

[0009] Patent Document 2: Japanese Patent Application Publication No. 2023-43049 Summary of the invention

[0010] An object of the present invention is to provide a current detection circuit capable of providing hysteresis to a comparison operation of a comparator whose detection object is current, and a semiconductor integrated circuit for power supply incorporating the current detection circuit.

[0011] Another object of the present invention is to prevent the transistors of the hysteresis providing circuit constituting the current detection circuit from operating in the saturation region in a semiconductor integrated circuit for power supply that has a current detection circuit that uses a comparator to detect the open circuit state and the short circuit state of the output terminal and is composed of bipolar transistors.

[0012] In order to achieve the above-mentioned object, the present invention provides a current detection circuit, comprising: a current-voltage conversion element, which converts a detection object current or a reference current into a voltage; a comparator, one input terminal of which is input with a voltage obtained by current-voltage conversion by the current-voltage conversion element, and the other input terminal is input with a voltage that becomes a reference for comparison or a voltage obtained by converting the detection object current; and a hysteresis imparting circuit, which is used to impart hysteresis to the comparison operation of the comparator,

[0013] The hysteresis imparting 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.

[0014] The switching element is switched to an on state or an off state according to the output of the comparator, thereby increasing or decreasing the current flowing through the current-voltage conversion element by the amount of current of the current source circuit, causing the voltage obtained by converting the detection object current or the voltage obtained by converting the reference current to change, thereby giving a hysteresis to the comparison action of the comparator.

[0015] According to the current detection circuit having the above configuration, hysteresis can be given to the comparison operation of the comparator whose detection target is current.

[0016] According to the present invention, a current detection circuit capable of providing hysteresis to the comparison operation of a comparator whose detection object is current and a power supply semiconductor integrated circuit having the current detection circuit built therein can be provided. In addition, in a power supply semiconductor integrated circuit having a current detection circuit that uses a comparator to detect an open circuit state or a short circuit state of an output terminal and that is composed of bipolar transistors, there is an effect that a transistor constituting a hysteresis providing circuit of the current detection circuit can be prevented from operating in a saturation region. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a circuit configuration diagram showing a first example of a regulator IC to which the first embodiment of the present invention is applied.

[0018] Figure 2 1 is a circuit configuration diagram showing a second example of a regulator IC to which the first embodiment of the present invention is applied.

[0019] Figure 3 1 is a circuit configuration diagram showing a third example of a regulator IC to which the first embodiment of the present invention is applied.

[0020] Figure 4 This is a circuit configuration diagram showing a basic configuration of a regulator IC according to a second embodiment to which the present invention is applied.

[0021] Figure 5 1 is a circuit configuration diagram showing a first example of a regulator IC to which the second embodiment of the present invention is applied.

[0022] Figure 6 1 is a circuit configuration diagram showing a second example of a regulator IC to which the second embodiment of the present invention is applied.

[0023] Figure 7 1 is a circuit configuration diagram showing a third example of a regulator IC to which the second embodiment of the present invention is applied.

[0024] Figure 8 (A) Figure 8 (B) is a circuit diagram showing the structure of a hysteresis providing circuit in a current detection circuit considered by the inventors before the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0026] (First Embodiment)

[0027] Figure 1 The circuit structure of the first example of the first embodiment of the present invention is shown as an example of applying the present invention to a series regulator as a DC power supply device. Figure 1 In FIG. 1 , a portion 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.

[0028] In the regulator IC10 of this embodiment, as Figure 1 As shown, a voltage input terminal IN to which a DC voltage VCC is applied and two output terminals OUT1 and OUT2 are provided as external terminals, PNP bipolar transistors Qp1 and Qp2 are connected between the voltage input terminal IN and the output terminals OUT1 and OUT2, respectively, and capacitors Co1 and Co2 are connected to the output terminals OUT1 and OUT2, so as to function as a DC power supply device that supplies two stable DC output voltages Vout1 and Vout2 to the outside. LD1 and LD2 represent load devices such as antennas connected to the output terminals OUT1 and OUT2.

[0029] In addition, resistors R11 and R12 and resistors R21 and R22 are connected in series between the output terminals OUT1 and OUT2 and the ground line to which the ground potential GND is applied, respectively dividing the output voltages Vout1 and Vout2. In the case where an external terminal connected to the midpoint of the resistors R11 and R12 or the midpoint of R21 and R22 is separately provided, R11, R12, R21, and R22 can be provided outside the regulator IC10.

[0030] The voltage VFB1 divided by the output voltage dividing resistors R11 and R12 is fed back to the non-inverting input terminal of the error amplifier 11A, which is the 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 the error amplifier 11B that controls the base terminal of the transistor Qp2. The error amplifiers 11A and 11B control the transistors Qp1 and Qp2 based on the potential difference between the output feedback voltages VFB1 and VFB2 and a predetermined reference voltage Vref, and control the output voltages Vout1 and Vout2 to a desired potential so that a current corresponding to the load flows. Thus, the transistors Qp1 and Qp2 function as current control elements and voltage control elements.

[0031] The regulator IC 10 of this embodiment is provided with: a reference voltage circuit 12 for generating a reference voltage Vref applied to the inverting input terminals of the error amplifiers 11A and 11B; and a bias circuit 13 for passing an operating current through the error amplifiers 11A and 11B and the reference voltage circuit 12 .

[0032] The reference voltage circuit 12 can be composed of a bandgap reference circuit, a series resistor, a Zener diode, and the like.

[0033] Furthermore, in the regulator IC10 of the present 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 the voltage 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 the transistors Qs1 and Qs2 as the control terminals. As a result, a current (a current of 1 / N) proportional to the collector current of Qp1 and Qp2 flows through Qs1 and Qs2 according to the element size ratio N.

[0034] Furthermore, in the regulator IC10 of the present embodiment, resistors R31 and R32 are provided as current-voltage conversion elements which are connected in series with the current mirror transistors Qs1 and Qs2, respectively, and convert the current flowing through Qs1 and Qs2 into voltage. The voltage converted by the resistors R31 and R32 is input to one input terminal of the comparators CMP1 and CMP2, and compared with the threshold voltage Vth applied to the other input terminal. Therefore, the resistor R31 and the comparator CMP1 constitute the current detection circuit 14A, and the resistor R32 and the comparator CMP2 constitute the current detection circuit 14B.

[0035] In addition, hysteresis providing circuits 17A and 17B are provided corresponding to the above-mentioned current detection circuits 14A and 14B. The hysteresis providing circuits 17A and 17B increase or decrease the current flowing through the transistors Qs1 and Qs2 according to the output states of the comparators CMP1 and CMP2, thereby providing hysteresis to the comparison operation of the comparators CMP1 and CMP2. The specific structure and operation of the hysteresis providing circuits 17A and 17B will be described in detail later.

[0036] In addition, there are an external terminal P1, which is used to connect a resistor Rdet for voltage-current conversion outside the chip; and a voltage converter 15, which generates a voltage Vth corresponding to the voltage Vdet generated at the external terminal P1, and uses comparators CMP1 and CMP2 to compare the voltage Vth generated by the voltage converter 15 with the voltage converted by the resistors R31 and R32 to detect any abnormality of the output terminals OUT1 and OUT2, either an open circuit abnormality or a short circuit abnormality. Therefore, the voltage Vth becomes a threshold for determining an open circuit abnormality or a short circuit abnormality.

[0037] exist Figures 1 to 7 In the embodiment of the present invention, a circuit configuration for detecting either an open abnormality or a short abnormality is shown, but a configuration capable of detecting both an open abnormality and a short abnormality of the transistors Qp1 and Qp2 is also possible.

[0038] When comparators CMP1 and CMP2 function as open circuit abnormality detection units, a voltage is generated at one input terminal (+ or -) of comparators CMP1 and CMP2 by allowing currents Iout1' and Iout2' of Qs1 and Qs2 to flow through resistors R31 and R32, and a threshold voltage Vtho is generated at the other input terminal (- or +).

[0039] On the other hand, when comparators CMP1 and CMP2 function as short-circuit abnormality detection units, a voltage is generated at one input terminal (- or +) of the comparators CMP1 and CMP2 by allowing currents Iout1' and Iout2' of Qs1 and Qs2 to flow through resistors R31 and R32, and a threshold voltage Vths is generated at the other input terminal (+ or -).

[0040] Furthermore, the inverting / non-inverting input terminals (- or +) of the comparators CMP1 and CMP2 to which Vtho or Vths is input can be arbitrary based on the logic of the subsequent logic circuit 16. Figure 1 In the figure, the symbols “+” and “−” which are added to the input terminals of the comparators CMP1 and CMP2 are omitted.

[0041] Here, whether Vth, Vtho or Vths is too high or too low, it may be restricted by the input dynamic range of comparators CMP1 and CMP2. In addition, when it is too low, the voltage generated by resistors R4, R31 and R32 becomes smaller, so there is a problem of accuracy.

[0042] Therefore, when comparators CMP1 and CMP2 function as open circuit abnormality detection units, the current flowing through transistor Qp1 or Qp2 is small. Therefore, it is desirable to set the current mirror ratio m between transistors Qp1 and Qs1, or between transistors Qp2 and Qs2 to be smaller. By making the current flowing through transistor Qs1 or Qs2 relatively large, Vtho will not become too small.

[0043] On the other hand, when comparators CMP1 and CMP2 function as short-circuit abnormality detection units, more current flows through transistor Qp1 or Qp2. Therefore, it is desirable to set the current mirror ratio m of transistors Qp1 and Qs1, or transistors Qp2 and Qs2 to be larger. By making the current flowing through transistor Qs1 or Qs2 relatively small, Vths will not become too large.

[0044] The regulator IC10 of the present embodiment is provided with a logic circuit 16 that receives the outputs of the abnormality detection comparators CMP1 and CMP2 as inputs, and an external terminal P2 that outputs a signal ERR indicating that the comparators CMP1 and CMP2 have detected an abnormality.

[0045] In addition, Figure 1 In the embodiment of the invention, a structure is shown in which the output of the logic circuit 16 is directly output from the external terminal P2, but it can also be configured to provide an NPN bipolar transistor whose base terminal is input to the output of the logic circuit 16 and whose collector terminal is connected to the external terminal P2, and output the abnormality detection signal ERR to an external CPU etc. in an open collector form. In addition, an output circuit composed of an emitter follower can be provided instead of an open collector transistor.

[0046] The logic circuit 16 is configured as a circuit having an OR logic function when the outputs of the abnormality detection comparators CMP1 and CMP2 are high and indicate an abnormal state and output the abnormality detection signal ERR at a low level. The logic circuit 16 is configured as a circuit having a NAND logic function when the outputs of the abnormality detection comparators CMP1 and CMP2 are low and indicate an abnormal state and output the abnormality detection signal ERR at a low level. The logic circuit 16 is configured as a circuit having a NOR logic function when the outputs of the abnormality detection comparators CMP1 and CMP2 are low and indicate an abnormal state and output the abnormality detection signal ERR at a high level.

[0047] Furthermore, two external terminals for outputting abnormality detection signals may be provided to output 2-bit abnormality detection signals corresponding to the outputs of the comparators CMP1 and CMP2 to the outside. In this case, the logic circuit 16 may be configured as a delay circuit, for example.

[0048] As described above, in the regulator IC10 of the present embodiment, when the output terminals OUT1 and OUT2 are connected to the same load, only one external terminal connected to the external resistor Rdet is provided, and an open circuit abnormality or a short circuit abnormality can be detected. In addition, the chip size can be reduced. Moreover, by saving terminals and components, a small and inexpensive package can be used, which can achieve space saving and cost reduction of the power supply device.

[0049] In addition, by changing the resistance value of the external resistor Rdet, the threshold for detecting an open circuit abnormality or a short circuit abnormality can be easily changed, thereby expanding the use of the IC. In addition, the hysteresis providing circuits 17A and 17B are provided, and the comparators CMP1 and CMP2 are configured to be able to perform hysteresis operations, thereby preventing the current detection circuits 14A and 14B from malfunctioning due to noise. In addition, hysteresis can be set for each of the current detection circuits 14A and 14B.

[0050] Next, specific circuits of the voltage converter 15 and the hysteresis providing circuits 17A and 17B in the IC will be described.

[0051] First, if Figure 1 As shown, the voltage converter 15 is constructed as follows: a current buffer 15a, which is composed of an amplifier AMP and an NPN bipolar transistor Q0, wherein the inverting input terminal of the amplifier AMP is connected to the external terminal P1 connected to the resistor Rdet, and the reference voltage Vref is applied to the non-inverting input terminal, and the emitter terminal of the NPN bipolar transistor Q0 is connected to the external terminal P1 and the inverting input terminal, and the output voltage of the amplifier AMP is applied to the base terminal; a current mirror circuit 15b, which folds back the current I1 generated by the current buffer 15a and flowing through the resistor Rdet; and a resistor Rth, which converts the current (replica current) I2 on the secondary side of the current mirror circuit 15b into a voltage, and the voltage converted by the resistor R4 is provided to the comparators CMP1 and CMP2 as a threshold voltage Vth for comparison and judgment.

[0052] Regarding 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. Thus, the amplifier AMP functions 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) is equal to the input voltage of the non-inverting input terminal (reference voltage Vref).

[0053] The above-mentioned amplifier AMP can be constructed by a general differential amplifier circuit composed of a pair of differential input transistors whose base terminals are input with the above-mentioned reference voltage Vref and the voltage Vdet of the external terminal P1, and a pair of load transistors and a constant current source (or resistor), and can act as a current buffer that allows a predetermined collector current to flow through the transistor Q0.

[0054] On the other hand, the current mirror circuit 15b is composed of a PNP bipolar transistor Q1 connected to the collector terminal of the transistor Q0 in series with Q0, a PNP bipolar transistor Q2 connected to the transistor Q1 as a current mirror, and a resistor R4 connected to the collector terminal of the transistor Q2, and the voltage obtained by current-voltage conversion by the resistor R4 is supplied to the comparators CMP1 and CMP2 as the 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.

[0055] Here, the characteristics of the voltage converter 15 will be described.

[0056] In the voltage converter 15 of the present embodiment, the voltage Vdet of the external terminal P1 is equal to the reference voltage Vref by the function of the current buffer 15a, that is, Vdet=Vref. Therefore, the current I1 flowing through the external resistor R4 via the current buffer 15a becomes

[0057] I1 = Vdet / Rdet = Vref / Rdet.

[0058] Therefore, when the current mirror ratio is set to m, the comparison reference voltage Vth generated by conversion by the resistor R4 through which the current I2 which is the current mirror circuit 15 b folds back the current I1 is passed is expressed by the following equation (1).

[0059] Vth=R4*I2=R4*I1 / m……(1)

[0060] On the other hand, the output current Iout1 of the output terminal OUT1 is converted into a voltage Vout1' by passing a current Iout1' generated by a current mirror (n) of transistors Qp1 and Qs1 through a resistor R31. Therefore, when the ratio of Qp1 to Qs1 is n, it is expressed by the following equation (2).

[0061] Vout1'=R31*Iout1'=R31*Iout1 / n......(2)

[0062] The comparator CMP1 detects an abnormality by comparing the voltage given by the above formula (1) with the voltage given by the formula (2). When the comparator CMP1 is used as an open circuit abnormality detection unit, by connecting an external resistor Rdet having a resistance value such as Vth=Vtho to the external terminal P1, a threshold voltage can be set, and a regulator IC that detects an open circuit when Vout1'≤Vtho can be implemented. When the comparator CMP1 is used as a short circuit abnormality detection unit, by connecting an external resistor Rdet having a resistance value such as Vth=Vths to the external terminal P1, a threshold voltage can be set, and a regulator IC that detects a short circuit when Vout1'≥Vths can be implemented.

[0063] Here, since the internal resistors R31 and R4 of the IC are both on-chip components, the relative comparison is good (approximately ±0.5%), and the variation in temperature characteristics due to manufacturing variation is eliminated.

[0064] On the other hand, the reference voltage Vref of the voltage converter 15 can generate a high-precision reference voltage based on a band gap or the like, and the external resistor Rdet is a discrete component, and a resistor with good accuracy and temperature characteristics and high accuracy (resistance accuracy is about ±1%, and temperature characteristics are about ±100ppm / °C) can be manufactured or obtained. Therefore, a high-precision comparison reference voltage Vth can be set, and the accuracy of open circuit abnormality detection or short circuit abnormality detection can be improved.

[0065] As for the output current Iout2 of the output terminal OUT2, high-precision open circuit abnormality detection or short circuit abnormality detection can be performed by the voltage converter 15 and the comparator CMP2 as described above. In addition, if the loads connected to the output terminals OUT1 and OUT2 are loads through which the same current flows with the same characteristics, the same comparison reference voltage Vth can be used in the comparators CMP1 and CMP2. Therefore, the voltage converter 15 can be shared as in the regulator IC10 of the present embodiment, and the comparison reference voltage Vth can be set by providing one external terminal P1 and one external resistor Rdet.

[0066] Next, the configuration and operation of the hysteresis providing circuits 17A and 17B will be described.

[0067] The inventors studied a hysteresis circuit suitable for a bipolar circuit when developing a regulator composed of bipolar transistors. However, in order to give hysteresis to the comparator, a method of switching the threshold voltage can be realized relatively simply, but in the case of using a common abnormality detection threshold for 2 channels as in the invention of Patent Document 2, the method of switching the threshold voltage cannot be applied. Therefore, a method of switching the input voltage or current on the other detection object side of the comparator is considered.

[0068] Figure 8 (A) Figure 8 (B) shows a hysteresis providing circuit which was initially considered by the present inventors.

[0069] in, Figure 8 The circuit (A) is a voltage switching type hysteresis imparting circuit, wherein a hysteresis resistor Rh is provided in series with a sensing resistor Rs that converts a proportional current Iout' of Iout into a voltage, and a switching transistor Qsw is provided in parallel with the resistor Rh, to which a detection current generating transistor Qs is connected in series with a current mirror to an output control transistor Qp through which an output current Iout flows.

[0070] on the other hand, Figure 8The circuit (B) is a current switching type hysteresis imparting circuit, in which a hysteresis transistor Qh and a switching transistor Qsw are provided in parallel with a transistor Qs for generating a detection current which is connected to an output control transistor Qp by a current mirror.

[0071] exist Figure 8 (A) Figure 8 In any circuit of (B), the switching transistor Qsw is turned on or off by the output of the comparator CMP. Thus, hysteresis is given to the detection target current.

[0072] However, about Figure 8 In the circuit (A), if the switching transistor Qsw is in the off state, the voltage obtained by multiplying the current Iout' by the resistance value of the resistors Rs and Rh is obtained as the input voltage of the comparator CMP. In addition, when the transistor Qsw is in the on state, the collector-emitter voltage of Qsw is ideally 0, and the input voltage of the comparator CMP is Iout'×Rs, which is the current Iout' multiplied by the resistance value of the resistor Rs. However, below the saturation voltage Vsat of the transistor, Qsw enters the saturation region, so the collector voltage will not be less than Vsat. Therefore, the input voltage of the comparator is not the value obtained by multiplying the current Iout' by the resistance value of the resistor Rs, but becomes Iout'×Rs+Vsat.

[0073] On the other hand, Figure 8 In the circuit (B), the current when transistors Qsw and Qh enter the saturation region is different from the current in the active region, so it cannot function as a circuit that gives a predetermined hysteresis to the detection object current. In regulators such as LDO, in order to improve power efficiency, the input-output voltage is often used under the condition that the collector-emitter voltage of the output control transistor Qp is small, and it must be used under the condition that the collector-emitter voltage of the detection current generation transistor Qs is also small. Therefore, in Figure 8 In the hysteresis providing circuit of (B), there is also a problem that the transistors Qsw and Qh are very likely to operate in the saturation region.

[0074] like Figure 1As shown, the hysteresis imparting circuit 17A in the regulator IC of this embodiment includes: PNP bipolar transistors Qh11 and Qh21 constituting a current mirror circuit with the transistors Qp1 and Qs1 constituting the current detection circuit 14A, and NPN bipolar transistors Qh41 and Qh31 connected in series with the transistors Qh11 and Qh21, respectively. The bases of the transistors Qh31 and Qh41 are coupled to each other so as to constitute a current mirror circuit, and the base terminal and collector terminal of Qh31 are coupled. In addition, a switching transistor Qsw1 for hysteresis switching 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.

[0075] In the hysteresis providing circuit 17A having the above-mentioned structure, when the current flowing through the transistor Qh11 is set to 10'Ihys11 when the switching transistor Qsw1 is turned on, the current Isns1 flowing through the resistor R31 is Isns1=Iout1'+Ihys11. In addition, the output of the comparator CMP1 is input to the base terminal of the transistor Qsw1, and when the detection operation is performed, Qsw1 is switched to the off state. And when the current flowing through the transistor Qh21 is set to Ihys21, when Qsw1 is turned off, the current flowing through the resistor R31 is Isns1=Iout1'+Ihys11-Ihys21.

[0076] Therefore, when the current detection circuit is used as an open circuit abnormality detection circuit, the 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 for short circuit detection, the 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).

[0077] By operating as described above, the detection current values ​​of the comparator CMP1 are different when performing the detection and release operations, so that hysteresis can be given to the current detection circuit 14A in the same manner as relatively switching the threshold voltage Vth. In addition, by adjusting the mirror ratio of the transistors Qh31 and Qh41 constituting the current mirror, the width of the hysteresis can be changed.

[0078] The hysteresis providing circuit 17B provided corresponding to the other current detection circuit 14B including the transistor Qs2, the resistor R32 and the comparator CMP2 also has the same configuration as the hysteresis providing circuit 17A and performs the same operation as described above.

[0079] As mentioned above, in Figure 8 In the circuit of (B), the current of the hysteresis transistor Qh is directly turned on and off, so the transistor operates in a saturation region and cannot provide a desired hysteresis to the detection target current.

[0080] On the other hand, according to the hysteresis providing circuit 17A of the present embodiment configured as described above, due to the transistor Qh21 which is a current source, the transistors Qh31 and Qh41 which copy the current of Qh21 by the current mirror, and the transistor Qsw which has the task of stopping the current flowing through Qh31 and Qh41, Qh11 and Qh21 do not operate in the saturation region, and thus a desired current hysteresis can be provided. This is also the case in the hysteresis providing circuit 17B. In addition, in the case of the MOS transistor configured Figure 1 In the case of the regulator IC10, since there is no saturation problem, it can also be Figure 8 A hysteresis providing circuit having a structure as shown in (B).

[0081] However, in Figure 1 In the regulator IC10 of the embodiment shown, when the threshold voltage Vth is low (for example, when the Vth is set low for open circuit abnormality detection), the current detection circuits 14A and 14B operate in a state where the upper end value of the voltage converted by the resistors R31 and R32 is also low. In this case, the collector-emitter voltage of the transistors Qh41 and Qh42 is insufficient, and they may operate in the saturation region. Therefore, Figure 2 A regulator IC of an embodiment in which this countermeasure is implemented is shown.

[0082] Figure 2 The regulator IC10' of the second embodiment shown in FIG. Figure 1 In the regulator IC of the first embodiment shown, NPN transistors Q31 and Q32 are provided in series with the resistors R31 and R32 for current-voltage conversion in the current detection circuits 14A and 14B and the ground point, and the collectors and bases of the resistors R31 and R32 are coupled to function as diodes. In addition, a diode-connected NPN transistor Q4 is provided in series with the resistor R4 between the resistor R4 on the secondary side of the voltage converter 15 and the ground point. In addition, a diode element may be used instead of the transistors Q31, Q32, and Q4.

[0083] In the regulator IC10' of the second embodiment, by providing diode-connected transistors Q31 and Q32, the input voltage of the comparators CMP1 and CMP2 (the detection voltage converted by the resistors R31 and R32) does not fall below the threshold voltage of the NPN transistor. Thus, the collector-emitter voltage of the transistors Qh41 and Qh42 is sufficiently ensured, and Qh41 and Qh42 do not operate in the saturation region.

[0084] Furthermore, by providing the diode-connected transistor Q4 in the voltage converter 15, the potential difference between the input voltage of the comparators CMP1 and CMP2 and the threshold voltage Vth generated by the voltage converter 15 does not change before and after the transistors Q31 and Q32 are provided. At the same time, even if the base-emitter voltage of the transistors Q31 and Q32 differs for each IC due to manufacturing variations, it is possible to avoid a decrease in detection accuracy due to variations in the base-emitter voltage of the transistor Q4 in the same manner.

[0085] but, Figure 2 The circuit is a form in which the input voltage of the comparator CMP1 and CMP2 is increased by the forward voltage of the PN junction diode between the base and the emitter generated in the NPN transistors Q4, Q31, and Q32. Therefore, it is desired that the base-emitter voltages of Q4, Q31, and Q32 are the same. In addition, in order to make the base-emitter voltages the same, it is particularly important to match the ratio of the current flowing through the transistors Q4, Q31, and Q32 to the driving capability. In addition, the driving capability of the transistor also varies depending on the manufacturing process, so it is also necessary to consider the variation, such as arranging each transistor close to each other.

[0086] Figure 3 A regulator IC according to an embodiment in which a countermeasure against the above-mentioned deviation is taken is shown.

[0087] Figure 3 The regulator IC10" of the third embodiment shown is Figure 2 In the regulator IC of the second embodiment shown, for the purpose of commonality, the diode-connected transistors Q4, Q31, and Q32 are provided in series with the resistors R4, R31, and R32 for current-voltage conversion, and Q31 and Q32 are omitted and only Q4 is provided. Furthermore, the terminals on the grounding point side of the resistors R4, R31, and R32 are connected to the collector terminal side of the diode-connected transistor Q4, and the current flowing through the resistors R4, R31, and R32 flows entirely through the transistor Q4.

[0088] The regulator IC10" of the third embodiment is in the form of a diode-connected transistor for saturation prevention shared by the resistors R4, R31, and R32, and therefore, it is inevitable that a difference in base-emitter voltage will not occur as in the second embodiment. Furthermore, the thresholds for the detection action and release action of the comparator CMP1 are determined by comparing the voltage of the resistor R4×current I2 with the voltage of the resistor R31×Isns1, and the thresholds for the action and release action of the comparator CMP2 are determined by comparing the voltage of the resistor R4×current I2 with the voltage of the resistor R32×Isns2. Therefore, a current detection circuit that does not depend on the deviation of the diode-connected transistor can be realized. However, since the diode-connected transistor is shared by the current detection circuits 14A and 14B, crosstalk that affects the other current detection circuit may sometimes occur as one current detection circuit operates.

[0089] (Second Embodiment)

[0090] Next, a second embodiment in which the present invention is applied to a series regulator will be described. Figure 4 The basic circuit structure of the regulator IC according to the second embodiment is shown. Figure 4 FIG. 2 shows a circuit configuration of a basic regulator IC before hysteresis is added to the comparison operation of the comparators CMP1 and CMP2 constituting the current detection circuits 14A and 14B. Figure 5 to Figure 7 An embodiment of a circuit in which hysteresis is added to this basic circuit will be shown.

[0091] In the first embodiment, hysteresis is given to the current side of the detection target of the current detection circuits 14A and 14B. Figure 5 to Figure 7 The regulator of the example of the second embodiment shown is characterized in that the circuit on the side that generates the threshold voltage Vth that becomes the reference for comparison and determination is formed by a current mirror circuit, and hysteresis is given to the current flowing through the secondary side of the current mirror circuit. In addition, the basic structure of the circuit that gives hysteresis is the same in both the first embodiment and the second embodiment.

[0092] Figure 4The regulator IC shown in the figure is provided with a transistor Q22 constituting a current mirror circuit 15b of the voltage converter circuit 15 and a resistor R41 for converting the current I21 into a voltage, in addition to the transistor Q21 on the secondary side and the resistor R41 for converting the current I21 into a voltage. The transistor Q22 constituting a current mirror circuit with the transistor Q1 on the primary side and the resistor R42 for converting the current I22 into a voltage. The voltage converted by the resistor R41 is supplied to the comparator CMP1 of the current detection circuit 14A as a threshold voltage Vth1 for comparison and determination, and the voltage converted by the resistor R42 is supplied to the comparator CMP2 of the current detection circuit 14B as a threshold voltage Vth2 for comparison and determination. Vth1 and Vth2 can be set to different potentials independently of each other, but can also be the same voltage value.

[0093] Figure 5 The regulator IC10 shown is set up by using Figure 4 The hysteresis providing circuits 17A' and 17B' are configured to provide hysteresis to the comparators CMP1 and CMP2 by changing the threshold voltages Vth1 and Vth2 used for comparison and judgment in the regulator IC. The hysteresis providing circuits 17A' and 17B' are configured to provide hysteresis to the comparators CMP1 and CMP2. Figure 1 The hysteresis providing circuits 17A and 17B shown have the same structure.

[0094] Among them, the hysteresis imparting circuit 17A' has: a transistor Q21, which forms a current mirror with the transistor Q1 on the primary side of the current mirror circuit 15b; transistors Qh11 and Qh21, which are also connected to Q1 in a current mirror manner; 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 the ground point. The hysteresis imparting circuit 17A' is configured to turn Qsw1 on / off according to the output of the comparator CMP1.

[0095] exist Figure 5 In the regulator IC10 shown, for example, when Qsw1 is in the on state, Vth1=R42×(I21+Ihys11), and when Qsw1 is in the off state, Vth1=R42×(I21+Ihys11-Ihys21), so that the threshold voltage Vth1 can be changed to give hysteresis to the comparator CMP1. The same is true for another hysteresis providing circuit 17B' that provides hysteresis to the comparator CMP2 of the current detection circuit 14B.

[0096] In addition, when the threshold voltages Vth1 and Vth2 are set to low values, the transistors Qh41 and Qh42 constituting the hysteresis providing circuits 17A' and 17B' may operate in the saturation region. Figure 1 The hysteresis providing circuits 17A and 17B in the regulator IC10 shown in FIG. Figure 6The regulator IC10' that takes such a countermeasure is shown.

[0097] exist Figure 6 In the regulator IC10', diode-connected transistors Q41 and Q31, and Q42 and Q32 are respectively provided in series with the resistors R41 and R42 for current-voltage conversion of the voltage converter 15 and the resistors R31 and R32 for current-voltage conversion of the current detection circuits 14A and 14B.

[0098] and, Figure 7 Indicates that Figure 6 The regulator IC10' is an embodiment of a countermeasure against deviation of a diode-connected transistor in the regulator IC.

[0099] exist Figure 7 The regulator IC10" shown in Figure 6 The diode-connected transistors Q41 and Q31 are made common, and the transistors Q42 and Q32 are made common.

[0100] In this embodiment, Figure 6 As in the embodiment shown, by providing a common diode-connected transistor Q41 for the resistors R31 and R41 for current-voltage conversion, and providing a common diode-connected transistor Q42 for the resistors R32 and R42, it is possible to avoid adverse conditions caused by transistor deviations, and to prevent the transistors Qh41, Qh31 and Qh42, Qh32 constituting the hysteresis imparting circuits 17A', 17B' from operating in the saturation region.

[0101] in addition, Figure 5 to Figure 7 The regulator IC of the second embodiment shown generates the threshold voltages Vth1 and Vth2 for comparison and determination of the comparators CMP1 and CMP2, respectively. Therefore, the problem of crosstalk between the current detection circuits 14A and 14B in the regulator IC of the first embodiment does not occur.

[0102] The invention completed by the inventors has been specifically described above based on the embodiments, but the present invention is not limited to the embodiments. For example, in the embodiments, bipolar transistors are used as transistors constituting the internal circuit of the regulator IC 10, but the first example ( Figure 1 )、The first example of the second embodiment ( Figure 5 ) MOS transistors can also be used instead of bipolar transistors.

[0103] In addition, in the above embodiment, the case of applying to a regulator IC having a 2-channel structure with 2 output terminals is described, but the number of channels is not limited to 2, and may be 3 or more. In addition, especially in the case of 3 or more channels, the signal indicating the detection of abnormality outputted from the logic circuit 16 may be outputted as a signal of 2 bits or more.

[0104] Furthermore, in the regulator IC of the above embodiment, the description is made assuming a case where the regulator IC is configured as a vehicle-mounted terrestrial digital power supply device having an antenna connected to the output terminal OUT as a load. However, the load is not limited to the antenna, and the regulator IC can also be applied to a power supply device connected to two or more loads with the same current consumption.

[0105] In addition, in the above-mentioned embodiment, the case where the present invention is applied to a regulator IC constituting a linear regulator such as an LDO is described, but the present invention is not limited to the regulator IC, and can also be applied to an IC constituting a DC-DC converter of a switch / regulator type or a high-side switch IC.

[0106] Explanation of symbols

[0107] 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 imparting circuit, CMP1, CMP2…comparator for open / short abnormality detection, Qp1, Qp2…current control transistor, Qsw, Qsw1, Qsw2…switching transistor (switching element), P1…external terminal (external resistor connection terminal), P2…external terminal (detection signal output terminal).

Claims

1. A current detection circuit, comprising: a current-voltage conversion element that converts a detection target current or a reference current into a voltage; a comparator, one input terminal of which is input with a voltage obtained by current-voltage conversion by the current-voltage conversion element, and the other input terminal is input with a voltage that serves as a reference for comparison or a voltage obtained by converting the detection target current; and a hysteresis imparting circuit for imparting hysteresis to the comparison operation of the comparator, characterized in that: The hysteresis imparting 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 switching element is switched to an on state or an off state according to the output of the comparator, thereby increasing or decreasing the current flowing through the current-voltage conversion element by the amount of current of the current source circuit, causing the voltage obtained by converting the detection object current or the voltage obtained by converting the reference current to change, thereby giving a hysteresis to the comparison action of the comparator.

2. The current detection circuit according to claim 1, characterized in that: The detection target current or the reference current is configured to flow through the current-voltage conversion element via the first transistor. The hysteresis imparting circuit has: a second transistor and a third transistor, the control terminals of which are applied with the same voltage as the voltage applied to the control terminal of the first transistor, and through which a current proportional to the current of the first transistor flows; as well as a fourth transistor and a fifth transistor, which are connected in series with the second transistor and the third transistor respectively, The control terminals of the fourth transistor and the fifth transistor are coupled to each other to form a current mirror circuit, 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.

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

4. A semiconductor integrated circuit for power supply, comprising: an input terminal and a plurality of output terminals; a plurality of current control transistors, which are respectively connected between the input terminal and the plurality of output terminals; and a control circuit, which controls the plurality of current control transistors, characterized in that: The semiconductor integrated circuit for power supply comprises: a plurality of current detection circuits, which convert currents proportional to the currents flowing to the plurality of output terminals through the plurality of current control transistors and a predetermined reference current into voltages and compare them to detect an open circuit state or a short circuit state of each of the plurality of output terminals; External terminals, which are used to connect external resistors; as well as a reference current generating circuit for generating the reference current based on a voltage of the external terminal generated by causing a current to flow through the external resistor, The multiple current detection circuits respectively have: a first transistor having a control terminal to which a voltage equal to the voltage applied to the 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 having one input terminal inputted with the detection voltage converted by the first current-voltage conversion element and another input terminal inputted with a voltage obtained by current-voltage conversion of the reference current as a comparison reference voltage; as well as a hysteresis imparting circuit for imparting hysteresis to the comparison operation of the comparator, The hysteresis providing circuit includes: a current source circuit that generates a current of a predetermined magnitude that is added to or subtracted from the current flowing through the first transistor; and a switch element that is connected in series with the current source circuit. The switching element is switched to an on state or an off state according to the output of the corresponding comparator, thereby, the current flowing through the first current-voltage conversion element increases or decreases the current of the current source circuit, and the detection voltage changes relative to the comparison reference voltage, thereby giving a lag to the comparison action of the comparator.

5. The semiconductor integrated circuit for power supply according to claim 4, characterized in that: The hysteresis imparting circuit has: a second transistor and a third transistor, the control terminals of which are applied with the same voltage as the voltage applied to the control terminal of the first transistor, and through which a current proportional to the current of the first transistor flows; as well as a fourth transistor and a fifth transistor, which are connected in series with the second transistor and the third transistor, respectively, The control terminals of the fourth transistor and the fifth transistor are coupled to each other to form a current mirror circuit, 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 semiconductor integrated circuit for power supply according to claim 5, characterized in that: The first transistor to the fifth transistor are composed of bipolar transistors, A PN junction rectifying element is connected between the first current-voltage conversion element included in the plurality of current detection circuits and the reference potential point so as to be forward oriented toward the reference potential point.

7. The semiconductor integrated circuit for power supply according to claim 6, wherein: The power supply semiconductor integrated circuit comprises: a voltage-current conversion circuit that generates a current corresponding to the voltage of the external terminal or the external resistor connected to the external terminal; a current mirror circuit that replicates the current generated by the voltage-current conversion circuit; and a second current-voltage conversion element that converts the output current of the current mirror circuit into a voltage, and the voltage converted by the second current-voltage conversion element is supplied to the plurality of current detection circuits as a comparison reference voltage. A common PN junction rectifying 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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