JP4049572B2 - Constant voltage regulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a constant voltage regulator, and more particularly to a control circuit that turns off a constant voltage output operation of a series regulator.
[0002]
[Prior art]
In the constant voltage regulator, when a power supply voltage is applied to an input voltage, a constant reference voltage is generated from a reference voltage generation circuit, and the reference voltage is compared with an output voltage by an error signal amplifier circuit. Accordingly, there is a series regulator in which a constant output voltage is output from the output circuit by adjusting the amount of current flowing through the transistor of the output circuit. In this series regulator, the input voltage is applied to the collector of the output transistor, the output voltage output from the emitter of the output transistor is monitored, and the output voltage increases when the load current flowing through the load connected to the output of the output circuit increases. In the error amplification circuit, the amount of current supplied to the base of the output transistor is increased according to the monitoring result, and the output voltage is kept constant. Also, when the load current flowing through the load connected to the output of the output circuit decreases, the output voltage rises. Therefore, in the error amplification circuit, the amount of current supplied to the base of the output transistor is reduced according to the monitoring result, and the output voltage is reduced. Kept constant.
[0003]
The series regulator is a constant voltage regulator suitable for use in an analog circuit or the like because the output voltage has no pulsating current component as compared with a switching type constant voltage regulator. For this reason, series regulators are used in a wide range of fields such as OA equipment, cooling / heating equipment, and car applications.
[0004]
In recent years, in various devices, it has been strongly desired to reduce the operation power consumption of the device and to reduce the quiescent current during the standby operation of the device. For this reason, in the series regulator, a control circuit for stopping the operation of the constant voltage generation circuit is provided to reduce current consumption during standby operation of various devices.
[0005]
FIG. 2 is a diagram showing a circuit configuration of a conventional constant voltage regulator.
In FIG. 2, reference numeral 1 denotes a constant current source, which generates and outputs a constant current I when power is applied to the input voltage VIN. Reference numeral 2 denotes a starting circuit, and a constant current I is supplied to the Zener diode D21 through the resistor R21. A Zener voltage is generated and output at the cathode of the Zener diode D21. Reference numeral 3 denotes a reference voltage generation circuit. When a Zener voltage is applied to the base of the transistor TR31, a reference voltage V1 that is reduced by the base-emitter voltage VBE is output from the emitter of the transistor TR31. Reference numeral 4 denotes an error amplifier, which is composed of a differential amplifier circuit, compares the reference voltage V1 with a comparison voltage V2 generated according to the voltage of the constant voltage output VOUT, and outputs an output voltage Vc according to the comparison result. Is adjusted and output. The comparison voltage V2 is a voltage at a connection point between the resistors R1 and R2 provided in series between the constant voltage output VOUT and the ground, and the reference voltage V1 and the comparison voltage V2 when the constant voltage output is a predetermined voltage. Are set to be equal to each other. An output circuit 5 is composed of Darlington-connected transistors TR51 and TR52. An input voltage VIN is applied to a common connection point of collectors, and the output circuit 5 corresponds to the output voltage Vc of the error amplifier circuit 4 supplied to the base of the transistor TR51. Thus, a predetermined constant voltage is output from the emitter of the transistor TR52.
[0006]
Reference numeral 6 denotes a control circuit, and a control signal STB is input to the bases of the Zener diode D62 and the transistor TR61 via the resistor R61 and the diode D61. Further, at the cathode of the Zener diode D62, when the control signal STB is at the H level and a current is supplied to the Zener diode D62, a Zener voltage is generated. When a Zener voltage is applied to the base of the transistor TR61, the transistor TR61 is turned on.
[0007]
Next, the operation of the constant voltage regulator of FIG. 2 will be described.
When the control signal STB is at the L level, in the zener diode D62, a current sufficient to generate a zener voltage does not flow and a zener voltage is not generated. Therefore, since the base voltage of the transistor TR61 is also lower than VBE, the transistor TR61 is in an off state. Then, in the startup circuit 2, the constant current I is supplied to the Zener diode D21 via the resistor R21, and a Zener voltage is generated at the cathode of the diode D21.
[0008]
In the reference voltage generation circuit 3, when a Zener voltage is applied to the base of the transistor TR31, the reference voltage V1 is generated and output to the emitter of the transistor TR31. Then, in the error amplifier 4, the reference voltage V1 is compared with the comparison voltage V2, and when the load current flowing through the load connected to the output circuit 5 increases and the output voltage VOUT decreases, the voltage of the comparison voltage V2 also decreases. When the reference voltage V1 is higher than the comparison voltage V2, the output voltage Vc of the error amplifier 3 increases. In the output circuit 5, the current flowing through the transistor TR52 increases according to the voltage Vc applied to the base of the transistor TR51, and the output voltage VOUT increases.
[0009]
Further, when the load current flowing through the load connected to the output circuit 5 decreases and the output voltage VOUT rises, the voltage of the comparison voltage V2 also rises. When the reference voltage V1 is lower than the comparison voltage V2, the error amplifier 4 The output voltage Vc decreases. In the output circuit 4, the current flowing through the transistor TR52 decreases according to the voltage Vc applied to the base of the transistor TR51, and the output voltage VOUT decreases. Thus, when the control signal STB is at L level, a predetermined constant voltage is output from the constant voltage output VOUT.
[0010]
Next, when the control signal STB is at the H level, in the control circuit 6, a current flows through the Zener diode D61, and a Zener voltage is generated. Then, a Zener voltage is applied to the bases of the transistors TR61 and TR62, the transistors TR61 and TR62 are turned on, and the constant current I of the constant current source supplied to the resistor R21 of the starting circuit 2 connected to the collector of the transistor TR61 is changed to the transistor. It flows to the ground via TR61.
[0011]
In the startup circuit 2, the current I does not flow through the Zener diode D21, and the generation of the Zener voltage is stopped. Thus, in the reference voltage generating circuit 3, the base of the transistor TR31 is not biased by stopping the generation of the Zener voltage, the transistor TR31 is turned off, and the generation of the reference voltage V1 is stopped. Since the transistor TR62 of the control circuit 6 is also on, the base of the transistor TR51 is grounded via the transistor TR62, the transistors TR51 and TR52 of the output circuit 5 are turned off, and the constant voltage output VOUT is stopped.
[0012]
In this way, in the standby operation, the supply of the constant current I flowing through the Zener diode D21 of the starter circuit 2 is stopped and the Zener voltage generation is stopped, so that the base of the transistor TR31 of the reference voltage generation circuit 3 is not biased, Since the generation of the voltage V1 is also stopped and the bias supplied to the base of the transistor TR51 is also stopped, the generation of the comparison voltage V2 is also stopped. Therefore, the reference voltage generating circuit 3, the error amplifier 4, and the output circuit 5 have no path for current to flow during the standby operation, and the quiescent current during the standby operation is reduced.
[0013]
[Problems to be solved by the invention]
However, in the above-described series regulator, there remains a current path in which the constant current I of the constant current source 11 supplied to the start-up circuit 1 during standby operation flows to the ground via the transistor TR61 of the control circuit 6, and the quiescent current during standby operation remains. Could not be reduced sufficiently.
[0014]
Therefore, an object of the present invention is to provide a control circuit for a constant voltage regulator that further reduces current consumption during standby operation of the constant voltage regulator.
[0015]
[Means for Solving the Problems]
The present invention has been created in view of the above-described points, and is characterized by constant voltage generating means for generating a constant voltage according to an input voltage, and the constant voltage based on the input voltage. A starting means for operating the generating means, and a control means for stopping the constant voltage generating means in response to an external control signal. The output means of the control means includes a current mirror circuit, and is controlled by the output of the current mode control means. The starting means is controlled.
[0016]
According to the present invention, the control output circuit of the control circuit for stopping and controlling the starting means of the constant voltage generating means is a current mirror circuit, and the constant voltage is generated by cutting off the current supplied to the starting circuit according to the control signal from the outside. The operation of the generating means was stopped. As a result, the constant voltage generating means is stopped by stopping the current flowing in the current mirror circuit according to the control signal from the outside, so the current consumption during the standby operation is only the current for the operation bias of the current mirror circuit. Thus, the quiescent current during standby can be reliably reduced.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Details of the present invention will be specifically described with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of the constant voltage regulator of the present invention. In FIG. 1, the starting circuit 2, the reference voltage generating circuit 3, the error amplifier 4 and the output circuit 5 have the same configurations as those in the prior art, and are given the same reference numerals and explanations thereof are omitted.
[0018]
In FIG. 1, reference numeral 7 denotes a control circuit, and a control signal STB is input from the outside to the bases of transistors TR71 and TR72 via a diode D71 and a resistor R71. The transistors TR73 and TR74 constitute a current mirror circuit, and the input voltage VIN is applied to the common connection point between the collector and the base of the transistor TR73 via the resistor R75 and the diode D72. The collector of the transistor TR74 is connected to a common connection point between the collector and base of the transistor TR75.
[0019]
When the control signal STB is at the L level, the transistor TR71 is in an off state because the base voltage to which the control signal STB is input is lower than the voltage VBE. In the transistor TR73, a current I corresponding to the value of the resistor R75 and the input voltage VIN flows. The diode D72 is provided in order to reliably hold a voltage at which the transistor TR73 can be turned on at the common connection point between the base and collector of the transistor TR73 by the forward voltage of the diode. The resistor R75 is a current limiting resistor for limiting the current flowing through the transistor TR71 when the transistor TR71 is turned on, and is a resistance of several hundred kΩ.
[0020]
The transistor TR74 acts to flow the same amount of current as the current I flowing through the transistor TR73. Thus, in the transistor TR75, the same current I1 as the current flowing in the transistor TR74 flows. The current I1 also flows through the transistor TR75 and the transistor TR1 having a mirror configuration, and the current I1 is supplied to the resistor R21 and the Zener diode D21 of the starter circuit 2. Thus, a Zener voltage is generated and output from the Zener diode D21 of the starter circuit 2. Then, in the reference voltage generation circuit 3, the Zener voltage is applied to the base of the transistor TR31, and the emitter voltage of the transistor TR31 is output as a voltage obtained by subtracting the voltage VBE from the Zener voltage. The error amplifier 4 compares the reference voltage V1 with the comparison voltage V2, and adjusts and outputs the output voltage Vc according to the comparison result. Specifically, when the load current flowing through the load connected to the output circuit 5 increases, the output voltage VOUT decreases in the output circuit 5, and thus the voltage of the comparison voltage V2 also decreases. Then, the error amplifying circuit 4 compares the reference voltage V1 with the comparison voltage V2, and since the comparison result is lower than the reference voltage V1, the output voltage Vc is increased. As a result, the current flowing through the transistors TR51 and TR52 of the output circuit 5 is increased, and the output voltage VOUT rises to a predetermined constant voltage. Further, when the load current flowing through the load connected to the output circuit 5 decreases, the output voltage output from the output voltage VOUT increases in the output circuit 5, and the voltage of the comparison voltage V2 also increases. Then, the error amplifying circuit 4 compares the reference voltage V1 and the comparison voltage V2, and since the comparison result is higher than the reference voltage V1, the output voltage Vc is lowered. As a result, the current flowing through the transistors TR51 and TR52 of the output circuit 5 is reduced, and the output voltage VOUT is lowered to a predetermined constant voltage.
As described above, when the control signal STB is at the L level, the constant voltage generating means performs a normal operation, and a predetermined constant voltage is output from the constant voltage output VOUT.
[0021]
Next, the operation when the constant voltage output of the constant voltage regulator is turned off will be described. When the control input STB becomes H level, the transistors TR71 and TR72 of the control circuit 7 are turned on. Then, in the transistor TR73, the voltage at the connection point between the collector and the base becomes the ground level, and the transistors TR73 and TR74 are turned off. Therefore, no current flows in the transistor TR75 when the transistor TR74 is turned off. Then, the current flowing through the transistor TR1 and the transistor TR1 constituting the current mirror circuit is stopped.
[0022]
In the start-up circuit 2, since the current supply from the transistor TR1 is stopped, no current flows through the Zener diode D21, and no Zener voltage is generated. Therefore, in the reference voltage generation circuit 3, the base of the transistor TR31 is not biased, so that the transistor TR31 is turned off and the reference voltage V1 is at the ground level.
[0023]
Since the collectors of the transistor TR71 and the common base transistor TR72 of the control circuit 7 are connected to the base of the transistor TR51, the transistors TR51 and TR51 are turned off. Therefore, the constant voltage output VOUT is not output, and the comparison voltage V2 becomes the ground level. In the differential amplifier circuit constituting the error amplifier 4, both the reference voltage V1 and the comparison voltage V2 are at the ground level, and no bias voltage is output from the output Vc. Further, in the error amplifier 4, since both the reference voltage V1 and the comparison voltage V2 are at the ground level, there is no path through which current flows.
[0024]
As described above, during the standby operation, in the start-up circuit 2, the reference voltage generation circuit 3, the error amplifier 4, and the output circuit 5, there is no current flow path, and the resistor R75 and the transistor TR71 to which the input voltage VIN is connected. Only the amount of current that flows to the ground via this remains, and the current consumed by other circuits is completely eliminated. The resistor R71 is a current limiting resistor that limits the amount of current flowing through the transistor TR71, and has a high resistance within a range in which a current amount for generating a forward voltage of the diode D72 that can sufficiently operate the current mirror circuit is supplied. For example, a resistance of several hundred kΩ. As a result, the amount of current flowing through the transistor TR71 is several tens of μA.
[0025]
The current flowing through the current limiting resistor R75 and the transistor TR71 is the consumption current of the constant voltage regulator in the standby state, and becomes a quiescent current. On the other hand, in the conventional circuit of FIG. 2, the constant current source 1 requires a current amount of several mA in order to stabilize each circuit. In the conventional circuit, since the current amount of the constant current source 1 is always kept flowing in the ground direction during standby, the quiescent current during standby operation is greatly reduced in the present invention.
[0026]
As described above, the present invention uses the current mirror circuit to supply the operation bias current to the starting circuit 2 of the constant voltage generating means, so that the constant voltage generating means is operated by stopping the current mirror circuit. The supply of the bias current is stopped. Therefore, when the current mirror circuit is stopped, only the current that flows from the input voltage VIN to the ground via the current limiting resistor R75 and the transistor TR71 becomes the quiescent current during the standby operation.
[0027]
【The invention's effect】
As described above, according to the present invention, the output circuit of the control circuit that controls the standby operation of the constant voltage regulator is provided with a current mirror circuit, and the bias for operating the starting circuit 2 of the constant voltage generating means using the current mirror circuit. Since the current is supplied, the bias current supplied to the transistor TR73 of the current mirror circuit flows to the ground via the transistor TR71 during the standby operation. The quiescent current of the constant voltage regulator is only the current that flows from the input voltage VIN to the ground via the current limiting resistor R75 and the transistor TR71, and the current does not flow to other circuits, and the current consumption during standby operation is reliably reduced. can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a circuit configuration of a constant voltage regulator of the present invention.
FIG. 2 is a diagram showing a circuit configuration of a conventional constant voltage regulator.
[Explanation of symbols]
2 Start-up circuit 3 Reference voltage generation circuit 4 Error amplifier 5 Output circuit 7 Control circuit VIN Input voltage VOUT Constant voltage output STB Control signal input

Claims (1)

A constant voltage generation circuit that generates a constant voltage according to an input voltage, a start circuit that operates the constant voltage generation circuit based on the input voltage, and an operation bias current that is supplied to the start circuit according to an external control signal A control circuit,
The output stage of the control circuit includes a diode, a current limiting resistor connected to one of the diodes, and a current mirror circuit connected to the other of the diodes ,
The mirror circuit includes a transistor having a base and a collector commonly connected to the other of the diodes,
The current mirror circuit outputs the operation bias current when a limiting current corresponding to a resistance value of the current limiting resistor is input and the transistor is turned on ,
The control circuit operates so as to flow the limiting current to a constant potential point in a standby operation to turn off the transistor and not to output the operation bias current.

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