The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2019-086510 filed in the Japan Patent Office on Apr. 26, 2019, the entire content of which is hereby incorporated by reference.
The present disclosure relates to a linear regulator and a semiconductor integrated circuit.
The input voltage Vi is supplied from an undepicted voltage source to the input terminal 911 through the wiring 930. It is presumable that a supply voltage from the voltage source is within a certain range. However, a surge voltage outside the certain range might be applied to the input terminal 911. In order to prevent a positive surge voltage higher than a maximum rated voltage of the input terminal 911 from being applied to the input terminal 911 in the power supply IC 910, the Zener diode 920 having a Zener voltage Vz not higher than the maximum rated voltage is included.
More specifically, when a positive surge voltage is applied to the input terminal 911 in the linear regulator 900, a surge current based on the positive surge voltage flows from the cathode of the Zener diode 920 to the anode as depicted in
Further, a negative surge voltage might be applied to the input terminal 911. In such an instance, a surge current based on the negative surge voltage flows from the anode of the Zener diode 920 to the cathode as depicted in
However, in a case where the input voltage Vi is high, the configuration depicted in
The present disclosure has been made in view of the above circumstances, and provides a linear regulator and a semiconductor integrated circuit that will contribute to reducing a circuit size or cost.
According to a first aspect of the present disclosure, there is provided a linear regulator that includes a semiconductor integrated circuit and an external diode externally connected to the semiconductor integrated circuit, and generates an output voltage from an input voltage with reference to a ground potential. The semiconductor integrated circuit includes an input terminal, an output terminal, an output transistor, a parallel diode, and a control circuit. The input voltage is applied to the input terminal. The output voltage is applied to the output terminal. The output transistor is disposed between the input terminal and the output terminal. The parallel diode is formed in parallel to the output transistor, and has a forward direction from the output terminal to the input terminal. The control circuit controls the output transistor in accordance with a feedback voltage based on the output voltage. An anode of the external diode is connected to a ground having the ground potential. A cathode of the external diode is connected to the output terminal.
According to a second aspect of the present disclosure, there is provided the linear regulator as described in the first aspect, in which the semiconductor integrated circuit includes an output protection diode section disposed between the output terminal and the ground. The output protection diode section includes one or more output protection diodes having a forward direction from the ground to the output terminal. Forward voltage of the output protection diode section is higher than the forward voltage of the external diode.
According to a third aspect of the present disclosure, there is provided the linear regulator as described in the first aspect, in which the semiconductor integrated circuit includes the output protection diode section disposed between the output terminal and the ground. The output protection diode section includes a first output protection diode and a second output protection diode. The cathodes of the first and second output protection diodes are respectively connected to the output terminal and the ground. The anodes of the first and second output protection diodes are commonly connected to each other.
According to a fourth aspect of the present disclosure, there is provided the linear regulator as described in any one of the first to third aspects, in which the semiconductor integrated circuit includes an input protection diode section disposed between the input terminal and the ground. The input protection diode section includes one or more input protection diodes having a forward direction from the ground to the input terminal. The forward voltage of the input protection diode section is higher than the voltage sum of the forward voltage of the external diode and the forward voltage of the parallel diode.
According to a fifth aspect of the present disclosure, there is provided the linear regulator as described in any one of the first to third aspects, in which the semiconductor integrated circuit includes the input protection diode section disposed between the input terminal and the ground. The input protection diode section includes a first input protection diode and a second input protection diode. The cathodes of the first and second input protection diodes are respectively connected to the input terminal and the ground. The anodes of the first and second input protection diodes are commonly connected to each other.
According to a sixth aspect of the present disclosure, there is provided the linear regulator as described in any one of the first to fifth aspects, in which the parallel diode is a parasitic diode formed on a metal-oxide-semiconductor field-effect transistor (MOSFET) that acts as the output transistor.
According to a seventh aspect of the present disclosure, there is provided the linear regulator as described in any one of the first to sixth aspects, in which, when a negative surge voltage is applied to the input terminal, a current based on the negative surge voltage flows from the ground toward the input terminal through the external diode, the output terminal, and the parallel diode.
According to an eighth aspect of the present disclosure, there is provided a semiconductor integrated circuit included in a linear regulator that generates an output voltage from an input voltage with reference to a ground potential. The semiconductor integrated circuit includes an input terminal, an output terminal, an output transistor, a parallel diode, and a control circuit. The input voltage is applied to the input terminal. The output voltage is applied to the output terminal. The output terminal is to be connected to the cathode of an external diode disposed outside the semiconductor integrated circuit. The output transistor is disposed between the input terminal and the output terminal. The parallel diode is formed in parallel to the output transistor, and has a forward direction from the output terminal to the input terminal. The control circuit controls the output transistor in accordance with a feedback voltage based on the output voltage. The anode of the external diode is connected to a ground having the ground potential.
According to a ninth aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in the eighth aspect, in which the semiconductor integrated circuit includes an output protection diode section disposed between the output terminal and the ground. The output protection diode section includes one or more output protection diodes having the forward direction from the ground to the output terminal. The forward voltage of the output protection diode section is higher than the forward voltage of the external diode.
According to a tenth aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in the eighth aspect, in which the semiconductor integrated circuit includes an output protection diode section disposed between the output terminal and the ground. The output protection diode section includes the first output protection diode and the second output protection diode. The cathodes of the first and second output protection diodes are respectively connected to the output terminal and the ground. The anodes of the first and second output protection diodes are commonly connected to each other.
According to an eleventh aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in any one of the eighth to tenth aspects, in which the semiconductor integrated circuit includes an input protection diode section disposed between the input terminal and the ground. The input protection diode section includes one or more input protection diodes having the forward direction from the ground to the input terminal. The forward voltage of the input protection diode section is higher than the voltage sum of the forward voltage of the external diode and the forward voltage of the parallel diode.
According to a twelfth aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in any one of the eighth to tenth aspects, in which the semiconductor integrated circuit includes an input protection diode section disposed between the input terminal and the ground. The input protection diode section includes the first input protection diode and the second input protection diode. The cathodes of the first and second input protection diodes are respectively connected to the input terminal and the ground. The anodes of the first and second input protection diodes are commonly connected to each other.
According to a thirteenth aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in any one of the eighth to twelfth aspects, in which the parallel diode is the parasitic diode formed on the MOSFET that acts as the output transistor.
According to a fourteenth aspect of the present disclosure, there is provided the semiconductor integrated circuit as described in any one of the eighth to thirteenth aspects, in which, when the negative surge voltage is applied to the input terminal, the current based on the negative surge voltage flows from the ground toward the input terminal through the external diode, the output terminal, and the parallel diode.
According to the above-mentioned aspects of the present disclosure, it is possible to provide a linear regulator and a semiconductor integrated circuit that will contribute to reducing a circuit size or cost.
Example embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. In the drawings referenced below, like elements are designated by like reference numeral and, in principle, will not be redundantly described. In this document, for the purpose of simplification of description, by denoting information, signals, physical quantities, members, parts, and the like with reference symbols or marks, the names of information, signals, physical quantities, members, parts, and the like corresponding to the symbols or marks may be omitted or abbreviated. For example, a later-described output protection diode section referred to by “20” (see
First of all, several terms used in the description of the embodiments of the present disclosure will be described. In the embodiments of the present disclosure, the term “IC” is an abbreviation of an integrated circuit. The term “ground” denotes a conductive part having a potential of 0 V (zero volt), which is a reference voltage or denotes a potential of 0 V itself. A potential of 0 V may be referred to as a ground potential. In the embodiments of the present disclosure, a voltage indicated without referring to a specific reference is a potential with respect to the ground. As regards a transistor configured as a field-effect transistor (FET) including a MOSFET, the term “ON state” denotes a state where there is conduction between the drain and source of the transistor, and the term “OFF state” denotes a cut-off state where there is no conduction between the drain and source of the transistor. This also holds true for transistors not classified as a FET. The ON state and the OFF state may be hereinafter simply referred to as ON and OFF, respectively. The term “MOSFET” is an acronym for metal-oxide-semiconductor field-effect transistor.
A first embodiment of the present disclosure will now be described.
As depicted in
An input voltage Vin having a predetermined positive DC voltage value is applied to the input terminal TM1. The input voltage Vin is supplied from the voltage source VS, such as a battery, to the input terminal TM1 through a wiring W1. The wiring W1 is disposed outside the power IC 10 and used to connect the voltage source VS to the input terminal TM1. The power supply IC 10 generates an output voltage Vout by decreasing the input voltage Vin applied to the input terminal TM1. The output voltage Vout is applied to the output terminal TM2. Except for a transient state, the output voltage Vout has a predetermined positive DC voltage value. The ground terminal TM3 is connected to a ground having a ground potential. The input voltage Vin and the output voltage Vout are voltages with respect to the ground potential. The output voltage Vout is lower than the input voltage Vin. In some cases, however, the output voltage Vout may be substantially equal to the input voltage Vin. The output voltage Vout is supplied to the load LD connected to the output terminal TM2. The output voltage Vout is used as a power supply voltage for driving the load LD. The load LD may be any load that is driven by a DC voltage.
The external diode DD is disposed outside the power supply IC 10. The cathode of the external diode DD is connected to the output terminal TM2 of the power supply IC 10. The anode of the external diode DD is connected to the ground.
In some cases, a positive surge voltage (e.g., 100 V) having a potential higher than the voltage (e.g., 40 V) to be outputted from the voltage source VS may be applied to the input terminal TM1 (i.e., applied to the wiring W1). The linear regulator according to the present embodiment does not include a Zener diode corresponding to the Zener diode 920 depicted in
This point is addressed by configuring the power IC 10 to increase the maximum rated voltage of the input terminal TM1. More specifically, the input terminal TM1 has a maximum rated voltage higher than a positive surge voltage that may be applied to the input terminal TM1. Therefore, even when a positive surge voltage is applied to the input terminal TM1, a surge current based on the positive surge voltage does not substantially flow through the input terminal TM1. Consequently, the power supply IC 10 and a circuit (including the load LD) in the output stage of the power supply IC 10 will not be significantly affected. The technology for increasing the maximum rated voltage of the input terminal TM1 is not described here because it is well known.
In some cases, however, a negative surge voltage may be applied to the input terminal TM1 (i.e., applied to the wiring W1). The external diode DD effectively functions to protect against the negative surge voltage. This matter will be described later.
The first embodiment includes the following example embodiments EX1_1 to EX1_4. The matters described above in conjunction with the first embodiment are applied to the example embodiments EX1_1 to EX1_4 unless specifically stated otherwise and as long as there is no contradiction. In a case where the matters described in conjunction with the individual example embodiments are contradictory to those described in conjunction with the first embodiment, the matters described in conjunction with the individual example embodiments may take precedence. Further, as long as there is no contradiction, the matters described in conjunction with one of the example embodiments EX1_1 to EX1_4 may be applied to another example embodiment (i.e., two or more of a plurality of the example embodiments may be combined).
The example embodiment EX1_1 will now be described.
The output transistor 11 is disposed between the input terminal TM1 and the output terminal TM2. Therefore, a current flowing from the output terminal TM2 toward the load LD flows through the output transistor 11. In the power supply IC 10a, the output transistor 11 is configured as a P-channel MOSFET, the source of the output transistor 11 is connected to the input terminal TM1, and the drain of the output transistor 11 is connected to the output terminal TM2.
The parallel diode 12 is formed in parallel to the output transistor 11, and has a forward direction from the output terminal TM2 to the input terminal TM1. Therefore, the anode of the parallel diode 12 is connected to the output terminal TM2, and the cathode of the parallel diode 12 is connected to the input terminal TM1. The parallel diode 12 is a parasitic diode formed on a MOSFET that acts as the output transistor 11. Accordingly, the parallel diode 12 may be hereinafter referred to as the parasitic diode 12.
The voltage divider circuit, which includes the voltage-dividing resistors R1 and R2, is disposed between the output terminal TM2 and the ground, and used to generate a feedback voltage Vfb based on the output voltage Vout. More specifically, the voltage-dividing resistor R1 is connected at one end to the output terminal TM2, and connected at the other end to the ground through the voltage-dividing resistor R2. As a voltage proportional to the output voltage Vout, the feedback voltage Vfb is generated at a connection node between the voltage-dividing resistors R1 and R2. The feedback voltage Vfb is transmitted to the control circuit 13.
The control circuit 13 controls the gate voltage of the output transistor 11 in such a manner that the feedback voltage Vfb agrees with a predetermined reference voltage. As a result, a voltage determined by the reference voltage and the resistance value ratio between the resistors R1 and R2 is set as a target voltage Vtg. Accordingly, the control circuit 13 continuously controls the ON resistance value of the output transistor 11 in such a manner that the output voltage Vout agrees with the target voltage Vtg.
The output voltage Vout itself may be the feedback voltage Vfb. In any case, the feedback voltage Vfb is a voltage based on the output voltage Vout. Further, the voltage-dividing resistors R1 and R2 may be disposed outside the power supply IC 10a. In such an instance, a feedback terminal for receiving the feedback voltage Vfb generated by the voltage-dividing resistors R1 and R2 is disposed as an external terminal of the power supply IC 10a.
As described above, a Zener diode for surge protection corresponding to the Zener diode 920 depicted in
However, if a negative surge voltage is applied to the input terminal TM1 in a state where no Zener diode is provided for the input terminal TM1, a negative voltage is generated at the output terminal TM2 by way of the parasitic diode 12 of the output transistor 11. If, in such an instance, no appropriate measures are taken, a high negative voltage is applied to a circuit (including the load LD) in the output stage of the power supply IC 10a. Consequently, the circuit in the output stage of the power supply IC 10a may be damaged.
In view of the above circumstances, the linear regulator according to the present embodiment is configured such that a diode for protecting against a negative surge voltage is connected to the output terminal TM2 as the external diode DD.
Consequently, no high negative voltage will be applied to the circuit (including the load LD) in the output stage of the power supply IC 10a. This not only prevents the circuit in the output stage of the power supply IC 10a from being damaged due to a negative surge voltage, but also beneficially works to protect the power supply IC 10a itself. Further, the external diode DD may not need to protect against the application of a positive surge voltage. This significantly reduces the loss that may occur in the external diode DD. Therefore, a diode in a small package can be used as the external diode DD. This makes it possible to reduce the overall size and cost of the linear regulator.
Referring to
In the reference configuration depicted in
Meanwhile, in the configuration depicted in
In the configuration depicted in
Further, the external diode DD may be of any type. For example, the external diode DD may be a rectifier diode (PN diode) based on PN junction, a Schottky barrier diode, or a Zener diode. However, the reverse bias breakdown voltage of the external diode DD may need to be higher than the target voltage Vtg of the output voltage Vout. That is, even when the target voltage Vtg of the output voltage Vout (in reality, a voltage higher than the target voltage Vtg by a predetermined margin voltage) is applied to the cathode of the external diode DD, it is necessary that no current flow to the external diode DD. Moreover, the allowable forward current value of the external diode DD may need to be equal to or greater than the value of the surge current INS (see
The example embodiment EX1_2 will now be described. An electrostatic discharge (ESD) protection element may be disposed in the power supply IC 10 depicted in
First of all, the output protection diode section 20 will be described. The output protection diode section 20 is an ESD protection element for protecting the power supply IC 10b or its peripheral circuits against static electricity that may be applied to the output terminal TM2. The output protection diode section 20 is formed inside the power supply IC 10b and disposed between the output terminal TM2 and the ground.
More specifically, the output protection diode section 20a depicted in
Meanwhile, the output protection diode section 20b depicted in
When a negative surge voltage is applied to the input terminal TM1 (see
Consequently, in the first or second example configuration of the output protection diode section 20, the forward voltage of the output protection diode section 20 is set to be higher than the forward voltage Vfa of the external diode DD. This prevents the surge current INS from flowing to the output protection diode section 20 upon the application of a negative surge voltage to the input terminal TM1. As a result, no problem occurs. More specifically, the forward voltage of the output protection diode section 20 in a case where a forward current having a predetermined current value flows to the output protection diode section 20 is set to be higher than the forward voltage Vfa of the external diode DD in a case where the forward current having the predetermined current value flows to the external diode DD. In this instance, the predetermined current value may be, for example, the current value of the surge current INS that is presumably generated based on the negative surge voltage.
In the output protection diode section 20a depicted in
Depending on the current carrying capacity (allowable forward current value) of the output protection diode section 20, the forward voltage of the output protection diode section 20 may be substantially equal to the forward voltage Vfa of the external diode DD. In such a case, when a negative surge voltage is applied to the input terminal TM1, the surge current INS partly flows through the output protection diode section 20. However, the output protection diode section 20 does not become damaged or otherwise defective as far as such a current is tolerable by the output protection diode section 20.
The input protection diode section 30 will now be described. The input protection diode section 30 is an ESD protection element for protecting the power supply IC 10b or its peripheral circuits against static electricity that may be applied to the input terminal TM1. The input protection diode section 30 is formed inside the power supply IC 10b and disposed between the input terminal TM1 and the ground.
More specifically, the input protection diode section 30a depicted in
Meanwhile, the input protection diode section 30b depicted in
When a negative surge voltage is applied to the input terminal TM1 (see
Consequently, in the first or second example configuration of the input protection diode section 30, the forward voltage of the input protection diode section 30 is set to be higher than the voltage sum (Vfa+Vfb) of the forward voltage Vfa of the external diode DD and the forward voltage Vfb of the parasitic diode 12. This prevents the surge current INS from flowing to the input protection diode section 30 upon the application of a negative surge voltage to the input terminal TM1. As a result, no problem occurs. More specifically, the forward voltage of the input protection diode section 30 in a case where a forward current having a predetermined current value flows to the input protection diode section 30 is set to be higher than the voltage sum (Vfa+Vfb) of the forward voltage Vfa of the external diode DD and the forward voltage Vfb of the parasitic diode 12 in a case where the forward current having the predetermined current value flows to the external diode DD and the parasitic diode 12. In this instance, the predetermined current value may be, for example, the current value of the surge current INS that is presumably generated based on the negative surge voltage.
In the input protection diode section 30a depicted in
Depending on the current carrying capacity (allowable forward current value) of the input protection diode section 30, the forward voltage of the input protection diode section 30 may be substantially equal to the above voltage sum (Vfa+Vfb). In such a case, when a negative surge voltage is applied to the input terminal TM1, the surge current INS partly flows through the input protection diode section 30. However, the input protection diode section 30 does not become damaged or otherwise defective as far as such a current is tolerable by the input protection diode section 30.
The example embodiment EX1_3 will now be described. An N-channel MOSFET may be used as the output transistor 11. In such a case, the source and drain of the N-channel MOSFET, which is used as the output transistor 11, are respectively connected to the output terminal TM2 and the input terminal TM1. In this case, too, it is true that the parasitic diode 12 having a forward direction from the output terminal TM2 to the input terminal TM1 is formed.
The example embodiment EX1_4 will now be described. The diode 12 is formed in parallel to the output transistor 11. The diode 12 functions as a parallel diode having a forward direction from the output terminal TM2 to the input terminal TM1. The foregoing description assumes that the diode 12 acting as a parallel diode is a parasitic diode of the output transistor 11. However, the diode 12 acting as parallel diode may be a diode disposed separately from the output transistor 11 instead of being a parasitic diode of the output transistor 11. In such a case, for example, a bipolar transistor may be configured as the output transistor 11.
A second embodiment of the present disclosure will now be described. The second embodiment is implemented based on the first embodiment. As regards the matters not specifically described in conjunction with the second embodiment, the description given in conjunction with the first embodiment is applied to the second embodiment as well as long as there is no contradiction. If a description given in conjunction with the second embodiment is found contradictory to the corresponding description of the first embodiment during the interpretation of the description of the second embodiment, the description given in conjunction with the second embodiment may take precedence.
The second embodiment includes the following example embodiments EX2_1 and EX2_2. The example embodiments EX2_1 and EX2_2 may be implemented in combination.
The example embodiment EX2_1 will now be described. The linear regulator according to the first embodiment may be mounted on any appropriate device.
In the vehicle 210, the load LD may be any electric device disposed in the vehicle 210. For example, the load LD may be an electronic control unit (ECU). The ECU provides, for example, cruise control of the vehicle 210 and drive control of an air conditioner, lamps, power windows, and airbags. The load LD may alternatively be, for example, the air conditioner, lamps, power windows, or airbags. The load LD may include a certain other power supply circuit.
The example embodiment EX2_2 will now be described. The technology described in conjunction with the first embodiment may be applied to a switch IC. The switch IC is a semiconductor integrated circuit for switching an input-output terminal state between a conducting state and a non-conducting state. In the switch IC, the output transistor 11 is used as a switching element.
The switch IC can be formed by transforming the power supply IC 10 in the first embodiment in a manner described below. More specifically, the switch IC can be formed by deleting the voltage divider circuit, which includes the voltage-dividing resistors R1 and R2, from the power supply IC 10 (10a, 10b) in the first embodiment. Based on a switching signal supplied from the outside of the switch IC, the control circuit 13 in the switch IC switches the output transistor 11, which acts as the switching element, between an ON state and an OFF state. When the output transistor 11 in the switch IC is in the ON state, conduction occurs between the input terminal TM1 and the output terminal TM2 so that the input voltage Vin at the input terminal TM1 appears as the output voltage Vout at the output terminal TM2. Meanwhile, when the output transistor 11 is in the OFF state, the input terminal TM1 is disconnected from the output terminal TM2.
The external diode DD is connected to the output terminal TM2 of the switch IC, as is the case with the power supply IC 10 described in conjunction with the first embodiment. Further, the anode and cathode of the external diode DD are respectively connected to the ground and the output terminal TM2 of the switch IC. The switch IC may also include the output protection diode section 20 and input protection diode section 30 depicted in
Moreover, the technology described in conjunction with the first embodiment may be applied to a semiconductor integrated circuit that includes the input terminal TM1, the output terminal TM2, and the output transistor 11 disposed between these terminals TM1 and TM2.
The embodiments of the present disclosure may be variously modified as needed within the scope of a technical idea defined by the appended claims. The foregoing embodiments are merely example embodiments of the present disclosure. It is to be understood that the significance of the present disclosure and the significance of terms describing individual component elements thereof are not limited in any way by those specifically described in the foregoing embodiments. Specific numerical values used in the foregoing description are merely illustrative and not restrictive, and may be changed to various other numerical values.
Number | Date | Country | Kind |
---|---|---|---|
2019-086510 | Apr 2019 | JP | national |