JPH02218972A - Voltage control circuit - Google Patents

Abstract

PURPOSE:To obtain higher output voltage by a control signal while omitting a variable resistor by generating overvoltage by the specific combination of control signals. CONSTITUTION:Reference voltage Va applying predetermined voltage is connected to one of the input terminals of an amplifier AMP and a resistor R1 is connected between the other input terminal and a voltage control circuit 1 while a resistor R2 is connected between the other input terminal and standard voltage. A switch 1 and a resistor 4 connected in series are connected to the resistor R1 in parallel and not only a switch 2 and a resistor 5 connected in series but also a switch 3 and a resistor 3 connected in series are connected to a resistor 2 in parallel. When control signals *VL, *VH are supplied to the circuit 1, output voltages V0 of four ways are obtained by these two combinations. The switch 1 becomes an ON-state by applying the signal *VL, the switch 2 becomes an ON-state by applying the signal *VH and the switch 3 becomes an ON-state by applying both signals. By this method, a variable resistor can be omitted and a test can be automated and stable overvoltage and output voltage can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a voltage control circuit having a function of varying an output voltage using a control signal.

The purpose is to omit the variable resistor and obtain a higher output voltage by controlling the control signal.

an amplifier that operates so that the voltages at its two input terminals are equal; a reference voltage connected to one of the input terminals of the amplifier; and a reference voltage connected to the other input terminal of the amplifier and an output terminal of the voltage control circuit. a second resistor connected between the other input terminal of the amplifier and a reference voltage; and a fourth resistor connected in parallel with the first resistor. a resistor and a first switch means, a fifth resistor and a second switch means, and a third resistor and a third switch means connected in parallel with the second resistor; The second switch means each
and turns on when a second control signal is applied;
The third switch means is configured to be turned on when the first and second control signals are applied.

[Industrial application field]

The present invention relates to voltage control circuits, and more particularly, to voltage control circuits.

The present invention relates to a voltage control circuit having a function of varying an output voltage using a control signal.

Using control signals for element voltage margin tests, etc. in power supplies built into electronic equipment.

A function that changes the output voltage of the power supply by, for example, ±10% is often added.

[Conventional technology]

FIG. 3 is an explanatory diagram of the prior art, showing a conventional voltage control circuit.

In FIG. 3, R1, R4, R5, R11 and R12
is a resistor, R2' is a variable resistor, pH and PI2 are photocouplers, AMP is an amplifier, and V is a reference voltage.

Amplifier AMP is a voltage stabilizing error amplifier.

It operates so that the voltages at its two input terminals are equal. Therefore, the voltage (2) at the connection point between the resistor R1 and the variable resistor R2' is made equal to the reference voltage V.

Normally, the control signals *vL and *v,I are both.

It is set to "H" (high level), which turns off the photocouplers P1 and PI2.

Voltage 1 depends on the ratio of resistor R1 and variable resistor R2'. Now, suppose V*-2.5V and R1=R2'.

Output voltage■. = 5. It becomes OV.

When the control signal *VL is set to "L" (low level), the photocoupler pH is turned on. Therefore.

The voltage V depends on the ratio of the resistors R1 and R4 connected in parallel to the variable resistor R2'.

As a result, if R1=R2', then V,>Vo-■,
becomes. On the other hand, due to the action of the amplifier AMP.

The output voltage VO-4.5V (-10% output) is obtained by setting the value of +Va-2-5V to +Va-2-5V when V is maintained at 0 or more so that V=V is maintained, and by appropriately determining the values of the resistors R1 and R4.

Conversely, if the control signal *■8 is set to L'', the photocoupler PI
2 is turned on. Then, R1=R2', V,=
By setting the value to 2.5V and appropriately determining the values of resistors R1 and R5, the output voltage o = 5.5V (-10% output)
get.

According to such a voltage control circuit, ICs such as TTL can operate normally at 5V, and can also operate at 4.5V.
A voltage margin test can be performed by operating at 5.5V and 5.5V.

[Problem to be solved by the invention]

In general, power supplies built into electronic equipment include TTL, etc.
An overvoltage protection circuit is provided to prevent overvoltage from being applied to C. Therefore, as part of the test, it is necessary to confirm whether the overvoltage protection circuit operates normally.

By the way, according to the voltage control circuit described above, if R2' (or R1) is a fixed resistance, a voltage of only 5.5V at maximum can be obtained (for voltages other than 5.5V, the voltage margin test that is widely conducted However, this method does not allow testing of overvoltage protection circuits, so a variable resistor R2' was indispensable to obtain a high voltage.

The need for variable resistor R2' in this way.

Conventionally, this has caused various problems.

For example, the value of variable resistor R2' had to be adjusted by nine people, which was an obstacle to test automation.
Further, since the 5 variable resistor R2' is usually realized as an external component (volume), there is a drawback that an f4 voltage is generated due to its malfunction.

An object of the present invention is to provide a voltage control circuit that can omit a variable resistor and obtain a higher output voltage using a control signal.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle configuration of the present invention.

In FIG. 1, 1 is a voltage control circuit, and 2 is a power supply.

3 is an electronic cable, 4 is an overvoltage protection circuit, R1 to R5 are resistors, and SWt to SW3 are switch means.

AMP is an amplifier, and ① is a reference voltage.

Amplifier AMP is a voltage stabilizing error amplifier.

It operates so that the voltages at its two input terminals are equal.

A reference voltage V is connected to one of the input terminals of the amplifier AMP (between it and the reference voltage). The reference voltage (■) is a voltage supply means that applies a predetermined voltage (■).

Dividing resistors R1 and R2 that divide the voltage from the power supply 2 are
They are connected in series between the output terminal (power supply voltage line) of the voltage 17711 circuit 1 and the reference (ground) voltage (reference voltage line). That is, the first resistor R1 is connected between the other input terminal of the amplifier AMP and the output terminal of the voltage control circuit 1, and the second resistor R2 is connected between the other input terminal of the amplifier AMP and the reference voltage. connected between.

A resistor R4 is connected in parallel with the resistor R2, and resistors R5 and R3 are connected in parallel with the resistor R2. Resistors R4, R5 and R3 are provided with switch means SWI, SW2 and SW, respectively.
3 are connected in series. That is, the fourth resistor R4 and the first switch means SWl are connected in parallel to the resistor R1. Further, the fifth resistor R5 and the second switch means SW2. and.

The third resistor R3 and the third switch means SW3.

Connected in parallel to resistor R2.

The voltage control circuit 1 is supplied with first and second control signals *vL and *Vi from the outside. 4 types of output voltage ■ by combination of 2 control signals. is obtained. The control signals *■ and *■□ are.

9 signals for obtaining an output voltage lower than the normal output voltage, and 1 signal for obtaining an output voltage higher than the normal output voltage, respectively. The first and second switch means SWI and SW2 respectively.

When the first control signal *vL and the second control signal *vH are applied, the third switch means SW3 is turned on.
turns on when both the first and second control signals *vL and *v,I are applied.

[Function] By the action of the amplifier AMP, the voltage at the connection point between the fixed resistor R1 and the fixed resistor R2 is made equal to the reference voltage v.

Normally, the control signals *vL and *v,I are both.

'H'' (high level), and as a result, the switch means SWI and SW2 are turned off, so that the voltage ■
, depends on the ratio of resistor R1 and resistor R2. Now, Vl
=2.5V, R1=R2, output voltage Vo=5.0
It becomes V.

When the control signal *v is set to "L" (low level), the switch means SWI is turned on. Therefore, the voltage V,
depends on the ratio of resistors R1 and R4 connected in parallel to resistor R2.

As a result, if R,1-R2, V,>V0■, on the other hand, due to the action of the amplifier AMP.

By setting VR = 2.5 (2) and appropriately determining the values of resistors R1 and R4, an output voltage Vo = 4.5 V (10% output) is obtained since V, = V is maintained at 0 or more. At this time, the control signal *vH is set to "H", and the switch means SW2 and SW3 are in the off state.

Conversely, when the control signal *V□ is set to "L", the control signal *VL is set to 1.
H'', only the switch means SW2 is turned on. Then, R1=R2,v.

= 2.5 V, and by appropriately determining the values of resistors R1 and R5, the output voltage ■. =5.5V (+10% output) is obtained.

On the other hand, when both the control signals *■ and *■8 are set to "L", the switch means SWI to SW3 are turned on.

Therefore, the voltage ■. depends on the ratio of resistors R1 and R4 connected in parallel to resistors R2, R3, and R5 connected in parallel.

As mentioned above, suppose that one normal voltage of 5.0 cm is changed by the same percentage (±10%) to the + side and to the - side.

R1=R2, R4=R5. And ■8-2.5
(2), and by appropriately determining the value of the resistor R3, the output voltages Vo-7 and OV are obtained.

Therefore, according to such voltage control circuit 1.

It is possible to obtain a normal operating voltage for normally operating the electronic device 3 such as TTL, and also to change the normal operating voltage for performing a voltage margin test of the electronic device 3 to the + side and - side by a predetermined ratio. It is possible to obtain a voltage that is higher and lower than the normal operating voltage by a predetermined percentage to test whether the overvoltage protection circuit 4 of the power supply device operates normally. High voltage can be obtained. Selection of these voltages can be set by control signals *■ and *vH.

〔Example〕

FIG. 2 is a configuration diagram of an embodiment, showing the configuration of the voltage control circuit 1. In FIG.

In FIG. 2, Ql and Q2 are transistors.

R7 to R12 are resistors, and D is a Zener diode.

pH and PI2 are photocouplers.

The first switch means SWI consists of two photocouplers P11 and a resistor R11. When the control signal *vL is set to “L”, 2
A voltage is applied to the light emitting diode to emit light, and a phototransistor that receives the light turns on. Note that instead of this configuration, a transistor that is turned on by 1L'' of the control signal *■L may be used.

The second switch means SW2 has the same configuration as the first switch means, and includes a photocoupler PI2 and a resistor R12, and a phototransistor is turned on by "L" of the control signal *vH.

The third switch means SW3 includes resistors R7 to R10, transistors Q1 and Q2 . It consists of a Zener diode D. As shown in the figure, the switch means SW3 includes a photocoupler p
It receives control signals *vL and *vH via H and PI2 (switch means SWI and 5W2), respectively. That is, the Zener diode D (and resistors R9 and RIO) is connected between the connection point C between the photocoupler Prl and the resistor R4 and the connection point C between the photocoupler PI2 and the resistor R5. and by a Zener diode D which receives control signals *■ and *Vi at both terminals thereof.

The (npn) transistor Q1, which is the actual switching means SW3, is driven.

When control signals *vL and *■bar are both “L”.

The voltage vhc between the connection points A and C is the voltage ■. is approximately equal to As a result, Zener diode D breaks down and current flows through resistor R9 and RIO. As a result, (pnp)) transistor Q2 turns on, and resistor R7
A current flows through R8. Therefore, transistor Q1 is turned on.

To enable such operation, a Zener diode D is connected between the connection points be in the direction shown, and its breakdown voltage 2 is vov, < v, +V = EQt or VI < Vz + Vm! oz and V
z +VmE, z<V. be satisfied.

Further, in order to obtain the voltage Vbc when both the control signals *vL and *VH are "L", the photocoupler pH is connected closer to the output terminal than the resistor R4, and the photocoupler P2 is connected closer to the reference voltage than the resistor R5.

When at least one of the control signals *■ and *vH is I]'', the voltage Vbc becomes O. Therefore, the Zener diode is not turned on, and the transistor Q1 is not turned on either.

Now, VR"2.5V, the ratio of resistance is R1:R2:R3:R
If 4:R5=1:1:1:3.9:3.9, then by the combination of control signals *■ and *V□.

The output voltage v0 is determined as follows.

■ Output voltage when *vH''``H'', *VL - ``H''. When obtaining a normal operating voltage, for example +5.0■, which normally operates the electronic element 3.

This combination is considered.

*V□=*VL=”H”, photocabra pH and P
Both I2 are turned off. The voltage at the nodes A and C becomes equal to the voltage V, and the Zener diode D is not turned on, so that the voltage I, depends on the ratio of the resistors R1 and R2.

Therefore, the output voltage■. 1 is in the on state. The voltage at connection points S and C is voltage v0
is approximately equal to , and Zener diode D does not turn on.
As a result, the voltage {circle around (2)} depends on the ratio of the resistor R2 to the parallel connection of the resistors R1 and R4.

Therefore, the output voltage v0 is =+5.0(V) becomes.

This increases the electronic device 3 such as TTL by +5. It can be operated with OV.

■ Output voltage V0 when *■I = “H”, *V, = “L”
When performing a voltage margin test on the electronic device 3, a low voltage for low voltage operation, for example +4.5
This combination is used when obtaining .

*yN=“H”, *vL=“L”, the photocabra P
I2 is turned off and the photocoupler PI-+4.5 (V
) becomes.

As a result, it is possible to perform a voltage margin test by operating the electronic element 3 at a low voltage of +4.5 .

■Output voltage when *vN=“L”, *VL=”H”■.

Therefore, when performing a voltage margin test on the electronic device 3, a high voltage such as +5.5V is used for high voltage operation.
This combination is used when obtaining .

Honey@L", *y, = "H" makes Hotokabura P
I2 is turned on and the photocoupler pH is turned off. The voltage at connection points S and C is voltage ■. is approximately equal to
Zener diode D does not turn on. As a result, the voltage
1 depends on the ratio of resistor R1 to the parallel connection of resistors R2 and R5.

Therefore, the output voltage ■. depends on the ratio of resistors R2, R3 and R5 connected in parallel to that of resistors R2, R3 and R5 connected in parallel.

Therefore, the output voltage■. teeth +5.5 (V) becomes.

As a result, it is possible to perform a voltage margin test by operating the electronic element 3 at a high voltage of +5.5 .

■ Output voltage V0 when *V, = 'L', *y, -'L'
This combination is used when obtaining a voltage for checking the operation of the overvoltage protection circuit 4.

Due to *V,=*VL-“L”, both photocoupler PTI and PI2 are turned on. The voltage V6c between connection points S and C is voltage ■. is equal to .

Zener diode D turns on (breaks down).

As a result, the voltage V, is equal to the resistance R1 and R4R2XR3X
R5 = +6.99 (V).

As a result, it is possible to apply an overvoltage of approximately 7 cm to the overvoltage protection circuit 4 and check its operation.

This overvoltage is detected by the control signal *v for voltage margin test.
Since this can be generated by using L and *vM, the number of signal lines does not increase.

Furthermore, since this overvoltage value is constant, damage to the load can be prevented. For example, for an electronic device 3, such as a standard logic IC such as TTL, whose normally used voltage is 5V and whose maximum rating is 7V, the overvoltage can be set to 7V or less. Thereby, even if there is a defect in the overvoltage protection circuit, destruction of the electronic element 3 can be prevented.

Width board.

is the reference voltage.

〔Effect of the invention〕

As explained above, according to one aspect of the present invention, in a voltage control circuit, by generating an overvoltage using a specific combination of control signals, it is possible to omit a variable resistor for generating an overvoltage. can be automated, and also.

Stable overvoltage and output voltage can be obtained, and the convertibility can be improved. Furthermore, by omitting the variable resistor, environmental resistance against gas and the like can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention. FIG. 2 is a configuration diagram of an embodiment. FIG. 3 is an explanatory diagram of the prior art. 1 is a voltage control circuit, 2 is a power supply, and 3 is an electronic element. 4 is an overvoltage protection circuit, and R1 to R5 are resistors.

Claims (1)

[Claims] An amplifier (AMP) that operates so that the voltages at its two input terminals are equal; a reference voltage (V_R) connected to one of the input terminals of the amplifier (AMP); and the amplifier (AMP). A first resistor (R
1), a second resistor (R2) connected between the other input terminal of the amplifier (AMP) and the reference voltage, and a second resistor (R2) connected in series with each other and in parallel with the first resistor (R1). a fourth resistor (R4) and a first switch means (SW1) connected to the second resistor (R2); a fifth resistor (R5) connected in series with each other and in parallel with the second resistor (R2); a second switch means (SW2); a third resistor (R3) and a third switch means (SW3) connected in series with each other and in parallel with the second resistor (R2); The first and second switch means (SW1, SW2) are turned on when the first and second control signals are applied, respectively, and the third switch means (SW3) is turned on when the first and second control signals are applied, respectively. A voltage control circuit characterized by being turned on when first and second control signals are applied.