JPH04177514A - Output transistor saturation preventing circuit of regulator circuit - Google Patents

Abstract

PURPOSE:To stabilize the output level obtained from an output transistor by setting an output saturation voltage to an arbitrary value by the product of a constant-current and a third resistance so as to prevent the generation of a rush current by obstructing the saturation of an output transistor of a regulator circuit. CONSTITUTION:To output transistor 22, a current of a current amplification factor fold of its base current flows, and to a first and a second resistances 23, 24, a part of its current flows. An intermediate connecting point voltage Vn of a first and a second resistances 23, 24 generated by this current is fed back to a negative phase input side of a voltage comparing means 21 and compared with an intermediate connecting source voltage, and a base current corresponding to its large/small relation is led in from the output transistor 22, therefore, each intermediate connecting point voltage becomes a balanced state to a reference voltage Vref of a positive phase input side. Accordingly, in the collector side of the output transistor 22, an output voltage given the product of resistance values of a fourth and a fifth resistances 65, 66 and a constant-current is obtained. In such a way, saturation of the transistor is prevented surely, and by fetching a stable output, overheating of a substrate, a fluctuation of the substrate potential, and an increase of a reactive current are prevented surely.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an output transistor saturation prevention circuit for a regulator circuit used to stabilize the output of a multi-power IC or the like.

[Conventional technology]

-i, power supplies with extremely small voltage fluctuations are used in various control circuits that perform control that requires high precision, such as the tracking servo and focus servo of CD player pickups. It is essential to install a regulator circuit to ensure stability. By the way, when a battery or the like is used as the input power source for this regulator circuit, when the voltage decreases due to battery consumption, the output transistor of the regulator circuit becomes saturated, and the saturated current flows to the IC board on which the regulator circuit is formed, causing damage to the board. Causes fever. In particular, the saturation current is a reactive current, which not only increases power consumption, but also causes the substrate potential to fluctuate due to the rush current, which is a factor that inhibits the normal operation of other circuits on the attached substrate. In order to prevent saturation of the output transistor of such a regulator circuit, for example, a regulator circuit J has been proposed in Japanese Patent Application No. 63-288225. In this regulator circuit, as shown in FIG. Section 2 (hereinafter simply referred to as "main circuit section 2")
A saturation prevention circuit 4 is installed at the front stage of the saturation prevention circuit 4. Main circuit section 2
A voltage comparator 21 receiving a reference voltage Vref is installed on the positive phase input side, and an output transistor 22 is installed which receives the output of the voltage comparator 21 as a base and extracts an output voltage Vout from the output terminal 20. A PNP type transistor is used as the output transistor 22, and the output transistor 22 is connected between the collector side and the ground point.
Resistors 23 and 24 are connected in series to convert the current flowing into the voltage into voltage. According to this regulator, the current flowing through the output transistor 22 causes a voltage drop across the resistor 23.24, and the voltage Vn generated at the intermediate connection point of the resistor 23.24 is fed back to the negative phase input side of the voltage comparator 21. ing. Therefore, in the main circuit section 2 of this regulator circuit, the positive phase input (+)
The voltage comparator 21 compares the reference voltage Vref applied to the voltage Vref and the voltage Vn across the resistor 23.24.
The base current of the output transistor 22 is drawn into the voltage comparator 21 side according to the comparison result of step 1, that is, the linear output, and the collector current of the output transistor 22 is controlled so that the reference voltage Vref and the voltage Vn are equal. It is. By the way, in such a regulator circuit consisting only of the main circuit section 2, when the power supply voltage ■cc decreases, that is, when
During power reduction, the emitter voltage of the output transistor 22 decreases, and when the value approaches the output voltage Vout, the output transistor 22 enters a saturated state. The output transistor 22 is formed as a part of an IC constituting a regulator circuit, for example, as shown in FIG. That is, a buried layer 26 made of an N-type high concentration region is formed on the substrate 25, and an N-type base region 27 is formed covering this buried layer 26. This base region 27 is separated from other regions by an isolation region 28, and a base electrode 29 is formed in the surface layer portion of the base region with an N-type high concentration region, and an emitter consisting of a high concentration P-type conductive region. A region 30 is formed, and a collector region 31 made of a highly doped P-type conductive region is formed surrounding the emitter region 30. Therefore, during normal operation, the output transistor 22 performs an amplification operation using the base region 27, emitter region 30, and collector region 31. However, when the potential of the emitter region 30 decreases due to a decrease in the power supply voltage VCC, and the potential difference between that potential and the potential on the collector region 31 side becomes smaller, the emitter region 30 becomes an emitter, the base region 27 becomes a base, and the isolation A parasitic transistor 32 is generated whose collector is the region 28, that is, the substrate 25, and a rush current flows through the parasitic transistor 32 from the emitter N region 30 to the substrate 25 side. The magnitude of this rush current is determined by the parasitic transistor 3
2, that is, the scale of the output transistor 22. In this case, since the output transistor 22 is expected to have a large output current, its emitter area is large, and the rush current flowing through the parasitic transistor 32 having the emitter area becomes extremely large in proportion to the large emitter area. In this way, the saturated state of the output transistor 22 is caused by the rush current caused by the parasitic transistor 32 in addition to the saturation current.
5 side, causing overheating of the substrate 25 and making the substrate potential unstable. In order to prevent this, a saturation prevention circuit 4 is installed at the front stage of the voltage comparator 21. This saturation prevention circuit 4 includes the n
A transistor 41 having an emitter area of about 1/2 is installed, and a resistor 42 is connected to the collector of this transistor 41.
．． 43.44 series circuits are connected. A voltage comparator 45 is installed on the base input side of the transistor 41, and a reference voltage Vref is applied from a reference voltage source such as a bandgap circuit to its positive phase input (+) side, and its negative phase input (-) side The voltage vrn generated at the intermediate connection point of the resistors 43 and 44 is fed back. This voltage Vm is
The control operation by the voltage comparator 45 makes it equal to the reference voltage Vref on the positive phase input (+) side. Therefore, the reference voltage V re is applied to the positive phase input (+) of the voltage comparator 21 of the main circuit section 2
f will be added. Therefore, in this regulator circuit, by installing the saturation prevention circuit 4, which forms a positive feedback amplifier equivalent to the main circuit section 2, in the front stage of the main circuit section 2, the output transistor 22
This is to prevent the output transistor 22 from entering the saturated state by forcibly forcing the transistor 41 of the saturation prevention circuit 4 to enter the saturated state before the output transistor 22 enters the saturated state. Here, in the main circuit section 2 and the saturation prevention circuit 4, the transistor 41 corresponds to the output transistor 22,
Each resistance value of each resistor 43, 44, 23, 24 is Ra, Rb
, Rc, Rd, each resistance value Ra=Rc, Rb=R
If it is set to d and matched on the IC, the output voltage Vout will be as follows. However, when the power is reduced, the resistor 42 is connected through the transistor 41.
．． Current flows through 43.44, and the voltage Vm across resistor 43.44
is reduced by the voltage drop across the resistor 42, and this voltage Vm is applied to the negative phase input (-) of the voltage comparator 45. Therefore,
If the resistance value of the resistor 42 is Ra, then the voltage ■α generated across the resistor 42 is as follows. Therefore, when the power is reduced, this voltage
The generation of α selectively saturates only the transistor 41 and prevents the output transistor 22 from saturating. This is equivalent to increasing the apparent saturation voltage on the output transistor 22 side. As a result, the transition of the output transistor 22 to the saturated state is alleviated.

[Problem to be solved by the invention]

Output transistor 22 in conventional regulator circuit
The idea of preventing saturation is to install a transistor 41, which has a smaller capacitance than the output transistor 22 and is less affected by parasitic transistors, in the preceding stage, and saturates the transistor 41 early when the output transistor 22 is saturated under adverse conditions. Since the transistor 41 has a small capacity, its saturation current is made smaller than that of the output transistor 22.
This is aimed at preventing the effects of saturation. However, although saturation of the output transistor 22 can be avoided by the transistor 41, the transistor 41 on the substrate 25 is still saturated, and a saturation current flows to the substrate 25 side through the transistor 41, preventing the generation of this saturation current. cannot be stopped. Furthermore, since increases and decreases in the rush current due to manufacturing process variations cannot be controlled, the current consumption Iq in the regulator circuit becomes unstable, and furthermore, increases and decreases in the saturation voltage of the transistor 41 are reflected directly in the output voltage Vout. This cannot be ignored in a regulator circuit that is expected to provide a stabilized output. Therefore, the present invention provides an output transistor saturation prevention circuit for a regulator circuit, which prevents the saturation of the output transistor of such a regulator circuit, prevents the generation of inrush current, and stabilizes the output level obtained from the output transistor. The primary purpose is to provide information. A second object of the present invention is to provide an output transistor saturation prevention circuit for a regulator circuit that achieves output stabilization by matching resistors for setting the output.

[Means to solve the problem]

That is, in order to achieve the first object, the output transistor saturation prevention circuit of the regulator circuit of the present invention is provided with an output transistor (22) that should output a stabilized output according to a reference voltage (Vref), and this output transistor A base current is drawn from the output transistor according to the difference between the reference voltage and the voltage taken out through the first and second resistors (23, 24) connected in series on the collector side of the output transistor. A regulator main circuit section (main circuit section 2) in which a voltage comparison means (voltage comparator 21) for controlling the current is installed, and a regulator main circuit section (main circuit section 2) that converts the reference voltage into a constant current (1) and converts this constant current into a first transistor. (
612), a current mirror circuit (63) that detects the constant current flowing through the first transistor, and a current mirror circuit (63) that detects the constant current flowing through the first transistor; a third resistor (62) connected between the resistors (62) and 62, which generates a voltage on the ground by the constant current; and a third resistor (62) installed corresponding to the first transistor, with a base connected to the voltage drop point of the third resistor. and a second transistor (64) which receives the constant current from the current mirror circuit, forming a series circuit connected in parallel to this second transistor, and which is to be applied as the reference voltage to the voltage comparison means. It is provided with fourth and fifth resistors (65, 66) that generate a voltage at the intermediate connection point. Further, in order to achieve the second object, the output transistor saturation prevention circuit of the regulator circuit of the present invention has the following features:
The resistor and the fourth resistor, and the second resistor and the fifth resistor are set to have equal resistance values.

[For production]

A constant current corresponding to the reference voltage Vref is obtained through the first transistor of the voltage-current conversion circuit, and this constant current flows through the current mirror circuit and the third resistor. The second transistor receives its base input voltage from the voltage drop point of the third resistor, and a constant current flows through the current mirror circuit. Therefore, the emitter of the second transistor has a base voltage that is equal to the base voltage of the second transistor.
A voltage is generated that is the sum of the emitter voltage. When the power supply voltage exceeds the voltage given by the product of the resistance values of the fourth and fifth resistors and the constant current, and the voltage generated in the third resistor, the second transistor becomes non-conductive. Therefore, the constant current from the current mirror circuit flows through the fourth and fifth resistors. The voltage at the intermediate junction point of the fourth and fifth resistors generated by this constant current is applied to the positive phase input side of the voltage comparison means, and the base current of the output transistor is drawn by its output. A current with a current amplification factor times the base current flows through the output transistor, and a portion of the current flows through the first and second resistors. The voltage at the intermediate junction point between the first and second resistors generated by this current is fed back to the negative phase input side of the voltage comparison means and compared with the voltage at the intermediate junction point between the first and second resistors, and the magnitude relationship is Since a base current according to the output transistor is drawn from the output transistor, the voltage at each intermediate node is in equilibrium with the reference voltage on the positive phase input side. Therefore, there is a fourth transistor on the collector side of the output transistor.
Then, an output voltage given by the product of the resistance value of the fifth resistor and the constant current is obtained. In the output transistor saturation prevention circuit, since the saturation of the output transistor depends on the emitter voltage of the second transistor, the output saturation voltage can be set by the product of the constant current and the resistance value of the third resistor. It can be set to any value using a resistor. Further, according to the present invention, by setting the respective resistance values of the first resistor and the third resistor, and the second resistor and the fifth resistor to be equal, the output voltage can be adjusted by the constant current and the fourth and fifth resistors. It is given by the resistance of Moreover, such a setting makes it possible to avoid variations in the IC manufacturing process and the effects of temperature changes, and to obtain stable output.

[Embodiments] Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 shows an embodiment of the output transistor saturation prevention circuit of the regulator circuit of the present invention. The output transistor saturation prevention circuit of this regulator circuit is equipped with a main circuit section 2, and a saturation prevention circuit 6 is installed in front of it, and the same parts as the regulator circuit shown in Fig. 3 are designated by the same reference numerals. It is attached. The main circuit section 2 has a reference voltage Vref on the positive phase input (+) side.
A voltage comparator 21 is installed as a voltage comparing means for receiving the voltage, and an output transistor 22 is installed to receive the output of the voltage comparator 21 as a base and take out the output voltage Vout from the output terminal 20. This output transistor 2
2, a PNP type transistor is used, and this output transistor 22 has its emitter connected to the power supply line 34.
First and second resistors 23 and 24 forming a series circuit for converting the current flowing through the output transistor 22 into a voltage are connected in series between the collector side and the ground point. Voltage Vn generated at the intermediate connection point of resistors 23 and 24
is added to the negative phase input (=) of the voltage comparator 21. Therefore, in the main circuit section 2, the reference voltage V ref and voltage Vn applied to the positive phase input (2) are connected to the voltage comparator 2.
1, and the comparison result of this voltage comparator 21, that is,
According to the linear output, the base current of the output transistor 22 is drawn into the voltage comparator 21 side, and the reference voltage V r
The collector current of the output transistor 22 is controlled so that ef and voltage Vn are equal. The saturation prevention circuit 6 is supplied with a reference voltage V ref to be applied to the positive phase input (+) side of the voltage comparator 21 using a constant current I
A voltage-current conversion circuit 61 is installed as a voltage-current conversion means for converting the voltage to the current. The reference voltage V ref is generated by a reference voltage source (not shown), such as a bandgap voltage generation circuit. A voltage-current conversion circuit 61 that is to convert the second reference voltage V ref into a constant current I is provided with a voltage comparator 611 on the input side, and a first transistor 612 is provided on the output side of this voltage comparator 611. ing. A transistor 612 is connected to the emitter side of this transistor 612.
A resistor 613 is connected to convert the current flowing into voltage into voltage. Therefore, the reference voltage Vref is
When applied to the positive phase input (+) of 1, a base current flows through the transistor 612 in accordance with the voltage input, and an emitter current flows in the transistor 612 in accordance with the base current. This emitter current is converted into a voltage by a resistor 613, and the voltage is the negative phase input (-
) side, the voltage comparator 611 compares the feedback voltage with the reference voltage Vref, and a base current corresponding to the difference voltage between the two flows to the transistor 612, and the voltage is increased between the reference voltage Vref and the resistor 613. The current flowing through the transistor 612 is controlled so that the generated voltage is equal to the current. A third resistor 62 is connected to the collector side of the transistor 612.
A transistor 631 on the input side of the current mirror circuit 63 is connected through the current mirror circuit 63. The transistor 631 is diode-connected, and the base and collector of this transistor 631 and the base of the transistor 6320 are shared. Therefore, when a constant current I flows through the transistor 631 through the transistor 612 and the resistor 62,
A constant current corresponding to the constant current I flows through the transistor 632 due to the current mirror effect of the transistors 631 and 632. Assuming that the emitter area ratios of the transistors 631 and 632 are equal, a constant current of 1 will flow through the transistor 632. Further, a second transistor 64 is connected between the collector of the transistor 632 and the ground point, and the base of this transistor 64 is connected to the voltage drop point of the resistor 62, that is,
It is connected to the collector side of transistor 612. This transistor 64 has fourth and fifth transistors forming a series circuit.
resistors 65 and 66 are connected in parallel. This resistance 6
The voltage Vm generated at the intermediate connection point of 5.66 is the reference voltage ■
ref, and is input to the positive phase input (+) side of the voltage comparator 21 of the main circuit section 2. In the above configuration, the operation will be explained. When the reference voltage V ref is applied to the voltage-current conversion circuit 61 , a constant current (2) according to the reference voltage V ref flows through the transistor 612 . When the resistance value of the resistor 613 is R1, the constant current I is R3. This constant current (2) flows through the current mirror circuit 63 to the resistor 65.66 during normal operation when the transistor 64 is not conductive. Here, the power supply voltage is ■. C1 resistance 62.65.66.2
If each resistance value of 3.24 is R2, R3, R4, R6, R, and R3=R5, R,=R6, the resistance is 65.66.
The voltage Vm generated at the intermediate connection point is as follows, and this is added to the positive phase input (+) of the voltage comparator 21. Therefore, the voltage Vn generated at the intermediate connection point of the resistors 23 and 24 is also equal to this voltage Vm,
The output voltage Vout is Vout = r ・(R3+R
4) ...(5) This results in a constant level set by the constant current I and the resistors R65 and R66. Such operation is conditional on the transistor 64 transitioning to a non-conducting state;
The operation is based on the power supply voltage V. This is selectively performed depending on the relationship between the voltages of the series circuit of C and resistors 65 and 66. That is, the power supply voltage ■. , is higher than ■.(Ri+Ra), the transistor 64 is turned off, so the power supply voltage ■cc
In a normal state where the voltage does not decrease, the transistor 64 always maintains a non-conducting state, the constant current I flows through the resistors 65 and 66, and the above normal operation is performed. Then, when the power supply voltage ■cC decreases, assuming that the voltage between the base and emitter of the transistor 631 is VFI, and the voltage between the base and emitter of the transistor 64 is VF2, the voltage Vp at the point P on the emitter side of the transistor 64 is as follows.・(6) becomes. Since it can be regarded as V F I - V F 2, the output saturation voltage is expressed as (
Vrer /R,)-Rz, constant current I(=V
rer /R,), i.e. determined by the resistance 613.62,
When a constant current ■ is applied, it is determined only by the resistance value R2 of the resistor 62. By installing the saturation prevention circuit 6 in this way, when the power is reduced, the output transistor 22 and other transistors 6
12.631.632.64 saturation can be reliably prevented,
The output voltage Vout can also be maintained at a constant set voltage and output. In addition, each resistance value R,, R9 of resistor 65.23 is R3=R
5. Let the resistance values R4 and R6 of the resistor 66 and resistor 24 be R4=
By setting R6 to ensure consistency, the output voltage Vout can be stabilized even against temperature changes and manufacturing process variations. Matching of each resistor 65, 66, 23, 24 can be easily realized by IC. Next, FIG. 2 shows a specific example of the circuit configuration of the output transistor saturation prevention circuit of the regulator circuit of the present invention. The voltage comparator 21 uses an operational amplifier, and a differential pair consisting of transistors 213 and 214 whose emitters are shared by a resistor 211 and 212 is installed, and a base input side of each transistor 213 and 214 is installed. Transistors 215, 216 are installed. transistor 2
A voltage Vm is applied to the base of transistor 2.
A voltage Vn is applied to the base of 16. and,
A current mirror circuit consisting of transistors 217, 218 is installed as an active load on the collector side of the transistors 213, 214. This voltage comparator 21 includes transistors 213 and 214.
A constant current source 219 is installed to drive the transistors 220 .
221.222.223 and resistance 224.225.22
Transistors 213.214 through a current mirror circuit 232 consisting of 6.227.228.229.230
and the emitter sides of transistors 215 and 216. An output taken out from the collector side of transistor 214 is applied to output circuit 233. The output circuit 233 includes transistors 234 and 235 connected to Darlington.
A resistor 236 is connected between the base and emitter of the transistor 235, and a phase compensation capacitor 237 is connected between the base and collector of the transistor 234. Resistors 238 and 239 are connected in series between the collector of the transistor 235 and the power supply line 34, and the base of the output transistor 220 is connected to the intermediate connection point of the resistors 238 and 239. The emitter area of the output transistor 22 in this embodiment is set to be approximately N times (for example, 100 times) that of the transistor 612. Further, in this embodiment, a constant current source 610 is installed as the voltage-current conversion circuit 61, and a constant current I flows through the constant current source 610 through a current mirror circuit 63 and a resistor 62. The emitter area of the transistor 632 of the current mirror circuit 63 is set to be twice that of the transistor 6310, and a constant current k·I is supplied to the resistors 65 and 66. The circuit of this embodiment is composed of a monolithic IC, and the resistors 65 and 23, and the resistors 66 and 24 are set to have equal resistance values. According to such a configuration, saturation of the output transistor 22 can be prevented as described in the above embodiment, and
Each transistor 213 of the main circuit section 2 formed on the IC
．． 214, and saturation prevention port 860) transistor 612
etc., saturation of all transistors can be prevented, and a stable output as described in the previous embodiment can be obtained. In this regulator circuit, resistor 65 and resistor 2
3. Since the resistor 66 and the resistor 24 are each set to have the same resistance value, a stable output can be obtained regardless of temperature changes or manufacturing process variations.

【Effect of the invention】

As explained above, according to the present invention, the following effects can be obtained. (a) It is possible to reliably prevent the saturation of the output transistor, as well as the saturation of the transistor installed to prevent the saturation, and it is possible to obtain a stable output. It is possible to reliably prevent overheating of the substrate, fluctuations in substrate potential, increases in reactive current, etc. (b) Stable output can be obtained regardless of temperature changes or manufacturing process variations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the output transistor saturation prevention circuit of the regulator circuit of the present invention, and FIG.
A circuit diagram showing a specific circuit configuration example of the output transistor saturation prevention circuit of the regulator circuit shown in the figure. Figure 3 is a circuit diagram showing a conventional regulator circuit with measures to prevent output transistor saturation. FIG. 3 is a diagram showing the configuration of an output transistor. 2... Main circuit section (regulator main circuit section) 21...
Voltage comparator (voltage comparison means) 22...Output transistor 23...First resistor 24...Second resistor 61...Voltage-current conversion circuit (voltage-current conversion means) 62...th No. 3 resistor 63...Current mirror circuit 64...Second transistor 65...Fourth resistor 66...Fifth resistor 612...First transistor V ref...Reference voltage ■ ...Constant current Figure 4

Claims (1)

[Claims] 1. An output transistor is installed to extract a stabilized output according to a reference voltage, and the output transistor is provided at an intermediate connection point between a first and a second resistor connected in series to the collector side of the output transistor. a regulator main circuit section provided with voltage comparison means for drawing a base current from the output transistor according to the difference between the reference voltage and the reference voltage, and controlling the current of the output transistor; a voltage-current conversion circuit that converts the constant current into a constant current and outputs the constant current through a first transistor; a current mirror circuit that detects the constant current flowing through the first transistor; the current mirror circuit and the first transistor; a third resistor connected between the transistors and configured to convert the constant current into a voltage; and a third resistor installed corresponding to the first transistor, the base of which is connected to the voltage drop point of the third resistor, and which converts the constant current into voltage. a second transistor receiving the constant current from the mirror circuit; forming a series circuit connected in parallel to the second transistor, generating a voltage at an intermediate connection point to be applied as the reference voltage to the voltage comparison means; An output transistor saturation prevention circuit for a regulator circuit, characterized in that the output transistor saturation prevention circuit comprises: 2. The output transistor saturation prevention circuit for the regulator circuit according to claim 1, wherein the first resistor and the fourth resistor, and the second resistor and the fifth resistor are set to equal resistance values. .