JPS63307510A - Reverse current preventing circuit for series voltage regulator - Google Patents

Abstract

PURPOSE:To prevent a reverse current and to avoid the drop of the output voltage and the breakage of an output element, by setting the output element under a nonconductive state when the input voltage is reduced less than the output voltage level. CONSTITUTION:A voltage comparator 8 performs comparison between an intermediate point (a) of a voltage dividing resistance 9 connected to an earth through the input side 1 of an output element 6 and an intermediate point (b) of a voltage dividing resistance 10 connected to the earth from the output side 2 of the element 6. In this case, the point (b) is divided at the same dividing rate as that of the point (a). The output of the comparator 8 performs control to set the element 6 under a nonconductive state in case the input voltage is reduced less than the output voltage level. Thus it is possible to prevent a reverse current and to avoid the breakage of the element 6 by setting the element 6 under a nonconductive state. Then the fluctuation of the input voltage is never transmitted to the output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a backflow prevention circuit for a series voltage regulator used as a power source for electronic circuits and the like.

[Summary of the invention]

The present invention is a backflow prevention circuit for a series voltage regulator in which backflow from the output to the input of the series voltage regulator is prevented by making the output element non-conductive.

[Conventional technology]

Conventionally, as shown in FIG. 2, a series voltage regulator has been known in which the output voltage is divided by a resistor 7 and compared with a reference voltage 4 by a voltage comparator 5 to control an output element 6.

[Problem that the invention seeks to solve]

However, conventional series voltage regulators have drawbacks such as if for some reason the input terminal drops below the output voltage, current flows backward through the output element 6, resulting in a drop in the output voltage and destruction of the output element 6. there were.

Therefore, in order to solve these conventional drawbacks, the present invention prevents reverse current by making the output element 6 non-conductive when the input voltage drops below the output voltage. The purpose is to prevent the element 6 from being destroyed.

[Means for solving problems]

In order to solve the above problems, this invention inserts a voltage dividing resistor between the input side and the ground side and between the output side and the ground side of the output element as shown in Fig. 1, and uses a voltage comparator to maintain the same division ratio. The potentials at points a and b are compared and if there is a possibility of backflow, the output element is made non-conductive to prevent backflow from the output to the input.

[Effect]

In the series voltage regulator configured as described above, when the input voltage becomes lower than the output voltage, the potential at point a also becomes lower than the potential at point a, and the output of the voltage comparator is inverted. This output is used to make the output element non-conductive. This prevents backflow from the output to the input.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In Fig. 1, the potential at the intermediate point C of the voltage dividing resistor 7 connected from output 2 to ground is designed to be equal to the voltage 4 at base 11 when output 2 reaches the set potential. , is compared with a reference voltage 4 by a voltage comparator 5. The output of the voltage comparator 4 controls the output element 6 so that the output voltage is equal to the set value. At the midpoint a of the voltage dividing resistor 9 connected from the input side of the output element 6 to the ground, and at the voltage dividing resistor 10 connected from the output 2 to the ground, the division ratio is the same as that at the midpoint a of the voltage dividing resistor 9. The voltage comparator 8 compares the potentials at the intermediate point S. voltage comparison n8
The output of is, when the input voltage is lower than the output voltage,
The output element 6 is controlled to be in a non-conductive state.

31st! 1 indicates a circuit that makes the output element 6 non-conductive when it is a MO3 structure transistor. FIG. 3 shows a positive voltage regulator in which the output transistor is of P type, and when the potential of 0 and 1 is higher than the potential of output 2, the output of voltage comparator 8 is at the ground level. The output of the inverter 11 is at the same potential as the input l, and P2.14° and P3.15 are in a non-conductive state. The output of the inverter 12 is at ground level, Pl and 13 are conductive, and the potential of the well is equal to the input.

When the potential of input 1 becomes lower than the potential of output 2, P2.14 and P3.15 become conductive, switching the well potential from input 1 to output 2, and changing the gate voltage of the output transistor to output 2. By making it equal to the potential of
Make it non-conductive to prevent backflow.

〔Effect of the invention〕

As explained above, this invention is effective in preventing reverse current by making the output element non-conductive, preventing damage to the output element, and preventing fluctuations in input voltage from being transmitted to the output voltage. be.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a series voltage regulator with a backflow prevention circuit according to the present invention, Fig. 2 is a circuit diagram of a conventional series voltage regulator, and Fig. 3 is a circuit diagram of a series voltage regulator with a backflow prevention circuit according to the present invention. FIG. 3 is a circuit diagram of a prevention circuit. 6...Output element 8...Voltage comparator 9.10...More than partial voltage resistance Applicant Seiko Electronics Co., Ltd. Reverse! Figure 1 Circuit diagram of conventional V-Leads voltage regulator L-7 L*F, l, -2 with stop circuit
Inpark C-MOSJ* is 0D Zunuma] Manli 4-wheel drive Figure 3

Claims (2)

[Claims] (1) In a series voltage regulator, when the input voltage of the series voltage regulator is lower than the output voltage of the series voltage regulator, the output element of the series voltage regulator is brought into a non-conducting state, thereby changing the voltage from the output side to the input side. A series voltage regulator backflow prevention circuit characterized by preventing current from flowing backwards toward the voltage regulator. (2) In a series voltage regulator with a MOS structure, by making the gate potential of the output transistor equal to the output potential and the well potential of the output transistor equal to the output, the output transistor is rendered non-conductive to prevent reverse current. A series voltage regulator backflow prevention circuit according to claim 1, characterized in that: