JP2010072902A - Series regulator and semiconductor integrated circuit for power supply control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a series regulator equipped with an overvoltage protection function of an input, an adjustment function of an output voltage and on/off-control function by suppressing the increase of the number of external terminals. <P>SOLUTION: This series regulator is provided with a transistor (Q1) connected between an input terminal and an output terminal; a control circuit (AMP, Q2) for controlling the drive of the transistor for control; a first decision circuit (CMP1) for deciding the overvoltage state of the input voltage by monitoring the voltage of a prescribed external terminal with a first decision level as a reference; and a second decision circuit (CMP2) for deciding the state of an external control signal by monitoring the voltage of the prescribed external terminal with a second decision level different from the first decision level as a reference. The transistor for control is put in an off-state based on the output of the first decision circuit, and at least a portion of operations of the control circuit is stopped based on the output of the second decision circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a constant voltage power supply circuit, further to a series regulator, and a power supply control semiconductor integrated circuit (series regulator IC), and more particularly to a series regulator IC having an on / off control function and an input overvoltage protection function. And effective technology.

  In order to protect the internal circuit of the IC from an overvoltage state in the series regulator, for example, there is a series regulator IC provided with an input voltage monitoring circuit as shown in FIG. This series regulator IC has a potential difference between a control transistor Q11 connected between the voltage input terminal 4 and the output terminal 6, a feedback voltage VFB obtained by dividing the output voltage Vout by resistors R11 and R12, and a reference voltage Vref. Accordingly, an error amplifier OP11 for controlling the control transistor Q11 and a comparator OP12 for detecting an input overvoltage are provided.

The series regulator IC of FIG. 3 generates a predetermined output voltage determined by the resistance ratio of the voltage dividing resistors R11 and R12 by stepping down the input voltage by the control transistor Q11, and includes the voltage dividing resistors R11 and R12. Therefore, the output voltage cannot be changed. In the series regulator IC of FIG. 3 having the input overvoltage protection function, the voltage input terminal 4, the output terminal 6, the ground terminal 9, and the voltage obtained by dividing the input voltage Vin by the resistors R17 and R18 are input to the comparator OP12. A total of four external terminals are provided.
JP 2000-305639 A

  Although the conventional series regulator has an advantage that the number of external terminals is small, there is a problem in that the output voltage is fixed and the function of stopping the operation from the outside is not provided, so that the user's usability is poor. On the other hand, as a series regulator IC provided with an output voltage adjustment function and an on / off control function in addition to the input overvoltage protection function, one having a configuration as shown in FIG. 4 is conceivable.

  The series regulator IC of FIG. 4 includes a control transistor Q1 connected between the voltage input terminal IN and the output terminal OUT, a feedback voltage VFB obtained by dividing the output voltage Vout by external resistors R1 and R2, and a reference voltage. An error amplifier AMP for controlling the control transistor Q1 in accordance with the potential difference from Vref, comparators CMP1 and CMP2 for detecting input overvoltage and undervoltage, and the like are provided. This series regulator can generate an arbitrary output voltage obtained by stepping down the input voltage by changing the ratio of the external resistors R1 and R2.

  Further, an inverter INV that discriminates an external command (on / off control signal) is provided, and the bias circuit BIAS that applies a bias to the error amplifier AMP is turned off to stop the driving of the control transistor Q1. It is configured.

  In the series regulator IC as shown in FIG. 4 provided with the output voltage adjustment function and the on / off control function in addition to the input overvoltage protection function, in addition to the voltage input terminal IN, the output terminal OUT, and the ground terminal GND, A terminal FB for inputting the feedback voltage VFB, a control terminal CNT for inputting an on / off control signal, a terminal OVP for inputting a voltage obtained by dividing the input voltage Vin by the resistors R3 and R4 to the comparator CMP1, and the like 6 external terminals are required. Therefore, there is a problem that the chip size increases and the chip cost increases.

  An object of the present invention is to provide a series regulator having a small increase in the number of external terminals and having an input overvoltage protection function, an output voltage adjustment function, and an on / off control function.

  In order to achieve the above object, the present invention provides a control transistor connected between an input terminal and an output terminal, a control circuit for driving and controlling the control transistor, and a voltage at a predetermined external terminal. A first determination circuit that monitors an input voltage overvoltage state by monitoring with reference to the determination level, and a voltage of the predetermined external terminal based on a second determination level different from the first determination level. And a second determination circuit for determining the state of the external control signal by monitoring the control transistor, turning off the control transistor based on the output of the first determination circuit, and based on the output of the second determination circuit Thus, at least a part of the operation of the control circuit is stopped.

  Preferably, the control circuit includes an error amplifier that outputs a voltage corresponding to a potential difference between a voltage obtained by dividing the output voltage and a predetermined reference voltage, and the error is based on an output of the second determination circuit. It is configured to stop the operation of the amplifier.

  According to the above-described means, the first determination circuit that determines the overvoltage state of the input voltage and the second determination circuit that determines the state of the external control signal can monitor the voltage of the common external terminal and perform the respective determinations. Therefore, it is possible to reduce one external terminal which was originally required two.

  Desirably, an external terminal for receiving a voltage obtained by dividing the output voltage is provided. Thereby, since the output voltage can be adjusted by changing the ratio of the resistors that divide the output voltage, an output voltage at a desired level can be generated.

  Further preferably, the low voltage state of the input voltage is determined by monitoring the voltage of the predetermined external terminal on the basis of a third determination level different from the first determination level and the second determination level. And a third determination circuit configured to turn off the control transistor based on an output of the third determination circuit. As a result, it is possible to provide a function of detecting a low voltage state of the input voltage, and even if the function is increased in this way, it is not necessary to increase the number of external terminals, so that an increase in chip size can be suppressed.

  Also, a power supply control semiconductor integrated circuit having the above-described configuration, a logic gate circuit using the input voltage applied to the input terminal as a power supply voltage and the external control signal as an input, and an output terminal of the logic gate circuit And a voltage dividing means that divides the input voltage, and is connected between the power supply and a ground point, and a series regulator is provided so that the voltage divided by the voltage dividing means is applied to the predetermined external terminal from the outside. Constitute.

  Alternatively, a power supply control semiconductor integrated circuit having the above-described configuration, a voltage dividing means connected between the input terminal and a ground point outside the semiconductor integrated circuit, and the semiconductor integrated circuit A switching element that is connected between the predetermined external terminal and a ground point outside and is connected to the gate terminal or the base terminal, and the voltage divided by the voltage dividing means is A series regulator is configured to be applied to a predetermined external terminal.

  This makes it possible to realize a series regulator with an input overvoltage protection function, output voltage adjustment function, and on / off control function using a power supply control semiconductor integrated circuit with a small number of external terminals. Cost increase can be suppressed.

  According to the present invention, an increase in the number of external terminals is small, and it is possible to realize a series regulator having an input overvoltage protection function, an output voltage adjustment function, and an on / off control function.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a series regulator to which the present invention is applied. Although not particularly limited, the elements constituting the circuit in the range surrounded by the alternate long and short dash line A in FIG. 1 are formed on one semiconductor chip and are used as a semiconductor integrated circuit (series regulator IC). Composed. C1 is an external smoothing capacitor that stabilizes the input voltage Vin, and C2 is an external smoothing capacitor that stabilizes the output voltage Vout.

  The series regulator IC in this embodiment has an externally connected control transistor Q1 connected between the voltage input terminal IN and the output terminal OUT, an open collector transistor Q2 for controlling the base voltage of Q1, and an output voltage Vout. And an error amplifier AMP for controlling the control transistor Q1 through the transistor Q2 in accordance with the potential difference between the feedback voltage VFB divided by the resistors R1 and R2 and the reference voltage Vref. This series regulator can generate an arbitrary output voltage obtained by stepping down the input voltage by changing the ratio of the external resistors R1 and R2.

  Further, a comparator CMP1 for detecting an input overvoltage and a comparator CMP2 for detecting a low voltage are provided, and a transistor Q3 provided between the base of the transistor Q2 and the ground point is turned on by the outputs of the comparators CMP1 and CMP2. Accordingly, the control transistor Q1 can be turned off by turning off Q2.

  Further, a comparator CMP3 that discriminates an external command (on / off control signal) CE is provided, and the control transistor Q1 is driven by turning off the bias circuit BIAS that applies a bias to the error amplifier AMP by the output of the comparator CMP3. It is configured to have a function of stopping. The comparators CMP1 to CMP3 operate using the input voltage Vin as a power supply voltage.

  In the series regulator IC of this embodiment, a voltage obtained by dividing the input voltage Vin by the resistors R3 and R4 is input to a terminal for inputting to the comparators CMP1 and CMP2 and a comparator CMP3 for inputting the on / off control signal CE. The terminal is shared. By changing the reference voltages Vref1, Vref2, and Vref3 applied to the non-inverting input terminals of the comparators CMP1 to CMP3, it becomes possible to determine the input of one terminal at each determination level. Here, for example, Vref1> Vref2> Vref3 is set.

  In order to make it possible to share a terminal for inputting a voltage obtained by dividing the input voltage Vin with the resistors R3 and R4 and a terminal for inputting the on / off control signal CE, in this embodiment, the input voltage Vin is provided in the preceding stage. Is provided with an inverter INV1 having a power source voltage, and resistors R3 and R4 for voltage division are connected in series between the output terminal of the inverter INV1 and a ground point, and the voltage divided by R3 and R4 is used as a common terminal CNT / It is configured to input to the OVP.

  In this configuration, when the ON / OFF control signal CE is input to the inverter INV1 and the control signal CE is set to the low level, the output of the inverter INV1 changes to the high level and the input voltage Vin is applied to the resistors R3 and R4. Since the same voltage can be applied, the same state as that of the terminal OVP in FIG. That is, when CE = “L”, the regulator IC enters an operation state in which the input voltage is monitored.

  On the other hand, when the control signal CE is set to the high level, the output of the inverter INV1 changes to the low level, the ground potential (0V) is applied to the resistors R3 and R4, and the terminal CNT / OVP is set to 0V. It can be detected that the on / off control signal CE is set to the high level. The comparator CMP3 outputs a low level signal when the control signal CE is at a high level, and the bias circuit BIAS is configured to stop supplying the bias to the error amplifier AMP, whereby CE = “H” and the regulator IC Becomes the output stop state.

  Thus, the external terminal of the series regulator IC of the present embodiment inputs the voltage input terminal IN, the output terminal OUT, the ground terminal GND, the terminal FB for inputting the feedback voltage VFB, and the on / off control signal CE. The common terminals CNT / OVP, a total of five external terminals are sufficient. Therefore, the number of external terminals can be reduced by one as compared with the regulator IC of FIG. 4 having the same function.

  FIG. 2 shows a modification of the series regulator of the embodiment of FIG. In FIG. 1, the voltage dividing resistors R3 and R4 for detecting the overvoltage state of the input voltage are connected between the output terminal of the inverter INV1 and the ground point, whereas in this modification, the voltage dividing resistor R3 for detecting the overvoltage. , R4 are connected between the input line or input terminal IN and the grounding point. Further, instead of providing the inverter INV1, a switch transistor SW1 composed of an N-channel MOSFET (insulated gate field effect transistor) is provided between the connection node of the voltage dividing resistors R3 and R4 and the ground point, and the gate terminal is turned on. / Off control signal CE is input.

  In this modification, when the on / off control signal CE is set to the low level, the switch transistor SW1 is turned off, a current flows through the resistor R4, and a voltage obtained by dividing the input voltage Vin by the resistance ratio of R3 and R4 is shared terminal. Since it is applied to CNT / OVP, the same state as the terminal OVP of FIG. That is, when CE = “L”, the regulator IC enters an operation state in which the input voltage is monitored.

  On the other hand, when the control signal CE is set to the high level, the switch transistor SW1 is turned on, the potential of the connection node between the resistors R3 and R4 is lowered to the ground potential (0V), and the terminal CNT / OVP is at a potential close to 0V. Therefore, the comparator CMP3 can detect that the on / off control signal CE is set to the high level. The comparator CMP3 outputs a low level when CE is at a high level, and the bias circuit BIAS is configured to stop supplying a bias to the error amplifier AMP. Therefore, the output of the regulator IC is stopped when CE = “H”. It becomes a state.

  Also in this modification, the number of external terminals of the regulator IC can be five, and the number of external terminals can be reduced by one as compared with the regulator IC of FIG. 4 having the same function.

  Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the comparator is used as the determination circuit for determining the overvoltage state and the low voltage state of the input voltage Vin and the high level state (off command state) of the on / off control signal CE. By appropriately setting the resistance ratio of R3 and R4 and the reference voltage Vref2, and replacing the P-MOS or N-MOS of the CMOS inverter with a constant current source or a resistor, a logic threshold with less power supply dependency is provided. It is also possible to replace the comparator CMP1 or CMP2 with an inverter by using an inverter.

  In the regulator of FIGS. 1 and 2, a logic circuit that determines these outputs and generates an internal control signal may be provided after the comparators CMP1 to CMP3. Further, in the embodiment, the comparator CMP2 for detecting the low voltage state of the input voltage is provided. However, the comparator (low voltage detection function) is omitted, and only the overvoltage protection function for detecting the overvoltage state of the input voltage is provided. You may comprise as follows.

  In the above-described embodiment, the resistors R1 and R2 that divide the output voltage to generate the feedback voltage are configured by external elements, and the regulator IC is provided with the feedback terminal FB that receives the divided voltage on the chip. However, the present invention can also be applied to a regulator IC having voltage dividing resistors R1 and R2 in the chip. In that case, five external terminals are required, but by applying the present invention, four external terminals can be used.

  In the above description, the example in which the present invention is applied to the series regulator IC has been described. However, the present invention is not limited to the present invention, and the input voltage monitoring function and the external on / off control function are desired to be provided. It can also be used for a voltage power supply circuit and a charge control IC.

It is a circuit block diagram which shows one Embodiment of the series regulator IC to which this invention is applied. FIG. 6 is a circuit configuration diagram showing a modification of the series regulator IC of FIG. 1. It is a circuit block diagram which shows an example of the conventional series regulator IC. It is a circuit block diagram which shows an example of the series regulator IC examined prior to this invention.

Explanation of symbols

AMP error amplifier CMP1 comparator for overvoltage monitoring (first determination circuit)
CMP2 Low voltage monitoring comparator (third judgment circuit)
CMP3 On / off control signal monitoring comparator (second determination circuit)
Q1 Control transistor

Claims (6)

A control transistor connected between the input terminal and the output terminal;
A control circuit for driving and controlling the control transistor;
A first determination circuit that monitors a voltage of a predetermined external terminal with reference to a first determination level to determine an overvoltage state of the input voltage;
A second determination circuit for monitoring the voltage of the predetermined external terminal with reference to a second determination level different from the first determination level to determine the state of the external control signal;
And configured to turn off the control transistor based on the output of the first determination circuit and stop at least part of the operation of the control circuit based on the output of the second determination circuit. A power supply controlling semiconductor integrated circuit.   The control circuit includes an error amplifier that outputs a voltage corresponding to a potential difference between a voltage obtained by dividing the output voltage and a predetermined reference voltage, and stops the operation of the error amplifier based on the output of the second determination circuit. The power supply control semiconductor integrated circuit according to claim 1, wherein the power supply control semiconductor integrated circuit is configured as described above.   3. The semiconductor integrated circuit for power control according to claim 2, further comprising an external terminal for receiving a voltage obtained by dividing the output voltage.   A third determination circuit for monitoring the voltage of the predetermined external terminal with reference to a third determination level different from the first determination level and the second determination level to determine a low voltage state of the input voltage 4. The power supply control semiconductor integrated circuit according to claim 1, wherein the control transistor is configured to be turned off based on an output of the third determination circuit. .   5. The semiconductor integrated circuit for power control according to claim 1, a logic gate circuit using the input voltage applied to the input terminal as a power supply voltage and the external control signal as input, and the logic gate circuit A voltage dividing means connected between the output terminal and a ground point for dividing the input voltage, and the voltage divided by the voltage dividing means is applied to the predetermined external terminal from the outside. Characteristic series regulator.   5. The semiconductor integrated circuit for power supply control according to claim 1, the voltage dividing means connected between the input terminal and a ground point outside the semiconductor integrated circuit, and the semiconductor A switching element connected between the predetermined external terminal and a grounding point outside the integrated circuit and having the gate terminal or the base terminal input the external control signal, and the voltage divided by the voltage dividing means Is applied to the predetermined external terminal.

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