JPS62109114A - Voltage regulator - Google Patents

Abstract

PURPOSE:To protect a control transistor from its breakage due to the discharging current by using a switching circuit that switches the substrate potential of the control transistor so that it is equal to the higher one of both levels of an input voltage source and the output voltage. CONSTITUTION:When Vin<Vout is satisfied between the input voltage and the output voltage, a transistor TR 53 is turned on and therefore the gate voltage of a TR 54 is approximately equal to the level of the Vout. Then the TR 54 is turned off. While the gate voltage is less than the source voltage with a TR 61 and therefore the TR 61 is turned on. Thus the substrate potential of a control TR 42 is approximately equal to the voltage Vout and therefore the P-N junction consisting of a P<+> area 23 and N<+> area 25 is adversely biased. Thus no current flows to the P-N junction part even in case a capacitor, etc. are connected between terminals 11 and 9. This prevents the breakage of the TR 42.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage regulator constructed using a C-MOS process.

(Summary of the Invention) The present invention provides a voltage control system using a C-MO87' process configured to compare an output voltage level with a predetermined reference voltage level and control the conductivity of a control transistor according to the comparison result.・In the regulator, 0-M2O)
The total substrate potential of the control transistor configured as a transistor is fixed at the better potential of the input voltage or output voltage, so that when the input voltage becomes lower than the output voltage, the control This prevents current from flowing from the input terminal to the output terminal within the transistor.

C. Prior Art There are many cases where it is desired to supply a stabilized voltage to various electronic devices, and in such cases, it is necessary to supply the battery voltage to the required circuits via a voltage regulator. is the general cup.

A circuit diagram of a conventional C-MO8 voltage regulator used under such dead weight conditions is shown in FIG. This voltage regulator 1 includes a reference voltage source 4 consisting of a current source 2 and an impedance 3, a differential amplifier 5 to which a reference voltage V from the reference voltage source 4 is applied to one input, and The control transistor 6 has a gate (G) to which the output of the dynamic amplifier 5 is input, and a drain (D) of the control transistor 6 is grounded via resistors 7 and 8. Here, 9 is a ground terminal, 10 is an input terminal for applying an input voltage, and 11 is an output terminal from which a stabilized voltage is output. The source (S) of the control transistor 6 has its substrate potential equalized and is connected to the input terminal 10, and the voltage generated across the resistor 8 is applied to the other input of the differential amplifier 5 as the detection voltage Vd. The structure is as follows.

According to this configuration, when the output voltage between the terminals 11-9 deviates from a predetermined level, this deviation is detected by the differential amplifier 5 and the source of the control transistor 6 is detected. The resistance between the drains is adjusted according to the detection result of the differential amplifier 5, so that the level of the filter pressure is kept constant.

(Problem to be solved by the invention) By the way, the circuit of this voltage regulator 1 is all C! - It is formed on a single conductor substrate by a MOS process, and the structure of the control transistor 6 is similar to that of the second
As shown in the figure. To explain the structure of the control transistor shown in FIG. 2, the substrate 21
In the N well n formed within the N well, there is a P region n which acts as a drain region, another A+ region n which serves as a source region, and an N region 5 formed so as to be in contact with this A+ region n. are formed, and the r region n is connected to the outside by an electrode 26, and the P+ region and the N region δ are at the same potential by a common electrode n, and are connected to the outside by this electrode n. is now possible. C, indicated by the code string fb, is a gate electrode, which faces the channel region (to) between the two P regions n, 24 with the insulating layer 29 interposed therebetween.

Therefore, if the potential of the electrode n connected to the input terminal 10 is higher than the potential of the electrode 26 connected to the output terminal 11, no problem will occur. A large capacity capacitor is often inserted between the output terminal 11 and the ground terminal 9 for the purpose of improving characteristics, but when such a configuration is used, for some reason the input voltage may be lower than the output voltage. At a lower level, the charge stored in this capacitor is discharged through the PN junction formed by region B and N0 region 5, as shown in FIG. The current will flow in the forward direction of the level. As a result, a current exceeding the allowable loss level of the element may flow, and there is a risk that the control transistor 6 may be destroyed.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks in the prior art, and to protect the control transistor by preventing current from flowing back into the control transistor even if the input voltage drops below the output voltage. I did it like this,
voltage. The purpose is to provide regulators.

Means for Solving Problem C] The configuration of the present invention for solving the above-mentioned problems of the prior art includes a control transistor connected to an input voltage source via a resistance circuit, and a voltage generated in the resistance circuit. and a circuit that compares the voltage with a predetermined reference atmospheric pressure and controls the degree of conductivity of the control transistor according to the comparison result, and obtains a stabilized output voltage from the resistor circuit. The regulator is characterized in that the substrate potential of the control transistor can be switched to the same potential as the higher of the level of the input voltage source and the level of the output voltage. .

(Function) According to this configuration, the potential of the substrate of the control transistor is set to the same potential as the higher level depending on the level between the input voltage source level and the output voltage level. However, if the input voltage level becomes lower than the output voltage level, the potential of the control transistor's substrate becomes the same potential as the output voltage level, so a large capacitor is inserted between the output voltage terminal and ground. Even if the capacitor is open, the discharge current of the capacitor will not flow from the output terminal to the input terminal, and the control transistor can be protected from waves caused by the discharge current.

〔Example〕

FIG. 3 shows a circuit diagram of an exemplary voltage regulator according to the present invention. In the voltage regulator 41 according to the present invention, the same parts as those in the voltage regulator 1 shown in FIG.

Similar to the control transistor 6 shown in FIG. A control voltage V from an error detection circuit 44 including a differential amplifier 5 is applied to the gate thereof. However, in this control transistor 42, the substrate has a structure in which neither the drain nor the source K is connected.

Control is performed to make the potential of the control transistor 420 substrate (not shown) the same as the potential of either the input terminal 10 or the output terminal 11 according to the magnitude relationship between the voltage level of the input terminal 10 and the voltage level of the output terminal 11. transistor 4
A first switch circuit 51 and a second switch circuit 61 are provided on the output side of the switch 2.

The first switch circuit 51 includes a transistor 58 whose gate is connected to the input terminal 10 and whose source and drain circuits are connected between the output terminal 11 and the ground terminal 9 via the electrolyte source 52; The transistor 54 has a source connected to the input terminal 10 and a drain connected to the substrate of the control transistor 42.

On the other hand, the second switch circuit 61 has a gate connected to the input terminal 10.
The source of the transistor 62 is connected to the output terminal 11 and the drain thereof is connected to the control transistor 420 substrate.

Next, the operation of the first and second sweetener circuits 51 and 61 will be explained.

When the value of the input voltage V in at the input terminal 10 is greater than the output voltage V out at the output terminal 11, the transistor 53 is turned off, and the gate voltage of the transistor 54 is approximately at the ground level, so the transistor 54 is turned on. Become. On the other hand, since the gate voltage of transistor 61 is higher than its source voltage, transistor 61 is turned off. As a result, the potential of the substrate of the control transistor 42 becomes approximately the same potential as the input voltage Vin. This is the same state as shown in FIG.
The problem of breaking ↓h does not occur at all.

When V in (V owt ), the transistor 5
8 is turned on, the gate voltage of the transistor 54 becomes approximately equal to the level of the output voltage V olLt, and the transistor 54 is turned off. On the other hand, since the gate voltage of transistor 61 is lower than its source voltage, transistor 61 is turned on. As a result, control transistor 4
The potential of the substrate No. 2 is i2! which is approximately the same as the output voltage V owt which is at a higher level than the input voltage V in ! Therefore, the I'N junction formed by the P region field and the N+ region 5 shown in FIG. No current flows through the 1'N junction, and the control transistor 42 will not be destroyed.

In this way, the substrate potential of the control transistor 42 is switched to be substantially the same as the higher potential of V in and V out, depending on the level of the input voltage V in and the output voltage V out. Because it will be done, and n
Therefore, it is possible to effectively prevent a large forward current from flowing in the control transistor 42.

Therefore, as in the conventional case, no current flows into the control transistor 42 from the load capacitor even if the levels of the input and output voltages are reversed.

Note that the configuration of the first and second switch circuits 51 and 61 is one example, and the configuration of the present invention is not limited to this example. For example, similar switches may be constructed using transistors of other conductivity types. Times! 27, or may be configured such that the potential of the substrate of the control transistor 42 is switched by other known means.

〔effect〕

According to the present invention, as described above, even if the input/output voltage levels are reversed, current can be prevented from flowing backward from the load side to the control transistor, and damage to the control transistor can be effectively prevented. be effective.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a voltage regulator using the conventional O+Z (OS process). Fig. 2 is a cross-sectional view showing the structure of the control transistor shown in Fig. 1. Fig. 3 is a circuit diagram of a voltage regulator according to the conventional O+Z (OS process). Circuit diagram of Poldage regulator. 41C voltage regulator 4 2 , %i control transistor 4 4C error detection circuit 51C first switch circuit 61 , second switch circuit and above

Claims (1)

[Claims] (1) A control transistor connected to an input voltage source via a resistor circuit, and the voltage generated in the resistor circuit is compared with a predetermined reference voltage, and the conductivity of the control transistor is determined according to the comparison result. In the voltage regulator, the substrate potential of the control transistor is equal to the level of the input voltage source and the output voltage. A voltage regulator characterized in that it can be switched to have the same voltage as the higher of the levels.