JP3292207B2 - Amplifier with switching control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of switching between a set constant voltage and a set constant current and outputting the same, selecting one of a plurality of operational amplifiers in accordance with a set input signal, and selecting the selected operational amplifier. The present invention relates to an amplifier with a switching control circuit in which an output amplifier is controlled by an output of the amplifier.

[0002]

2. Description of the Related Art In this type of amplifier, the setting state of inputs to a plurality of operational amplifiers is changed to change the voltage output state,
Switching between the positive current output state and the negative current output state. For switching, a saturation prevention circuit is connected to each operational amplifier, and one of a plurality of operational amplifiers is selected by a diode switch circuit according to the set input signal and the load state. The output voltage of the diode switch circuit is converted into a current and supplied to the output amplifier to control the output amplifier with the output of the selected operational amplifier.
No. 155515.

[0003] FIG. 8 shows a similar one to the proposed one. Input terminals 11, 12, 13 are connected to operational amplifiers 17, 18, 19 through resistors 14, 15, 16, respectively.
Is connected to the inverting input side. The output side of the operational amplifier 17 is connected to the connection point between the cathode of the diode 22 and the anode of the diode 23 of the diode switch circuit 21,
The output sides of the operational amplifiers 18 and 19 are connected to the cathode of the diode 24 and the anode of the diode 25 of the diode switch circuit 21, respectively. The anodes of the diodes 22 and 24 are connected, and the connection point 26
Are the Zener diode 27 for level shift and the resistor 28
Connected to the positive power supply terminal 29 through the diode 2
3, 25 are connected to each other, and the connection point 3
1 is a level shift Zener diode 32-resistor 3
3 is connected to the negative power supply terminal 34. The connection point between the Zener diode 27 and the resistor 28 is connected to the base of the pnp transistor 35, and the emitter of the transistor 35 is connected to the power supply terminal 29 through the resistor 36.
The resistors 28 and 36 and the transistor 35 constitute a voltage-current conversion circuit 37. The connection point between the Zener diode 32 and the resistor 33 is connected to the base of the npn transistor 38, and the emitter of the transistor 38 is connected to the power supply terminal 34 through the resistor 39. Resistors 33, 39,
The transistor 38 forms a voltage-current conversion circuit 41.

The collectors of the transistors 35 and 38 are connected to each other, and the connection point 42 is connected to the inverting input terminal of an output amplifier 43. Amplifiers 17, 18, 19, 43
Are connected to the ground. The output side of the output amplifier 43 is connected to an output terminal 45 through a current detection resistor 44, and the output terminal 45 is grounded through a load 46. The output terminal 45 passes through a buffer circuit 47,
Further, it is connected back to the inverting input terminal of the operational amplifier 17 through the resistor 48. The output side of the differential amplifier 49 for detecting the voltage between both ends of the current detecting resistor 44 is connected in feedback to the inverting input terminals of the operational amplifiers 18 and 19 through the resistors 51 and 52, respectively.

A saturation prevention circuit 53,5 is connected between each output side of the operational amplifiers 17,18,19 and each inverting input side.
4, 55 are connected. The saturation prevention circuit 53 is configured by connecting anti-parallel circuits of diodes in two stages in series, and the saturation prevention circuits 54 and 55 are configured by connecting anti-parallel circuits of diodes in three stages in series. Output voltage V _L
Is controlled, a sufficiently large negative voltage V
_B , the diodes D ₈ ,
The D _9, D ₁₀ is turned on to, the potential of the cathode of the diode 24, + 3V _F (V _F is the forward voltage drop of one diode) is clamped to become a cutoff state diode 24 is reverse biased, operation Amplifier 18 is separated from the control system. A sufficiently large positive voltage V _C is applied to the input terminal 13.
First, the diodes D ₁₄ , D ₁₅ , D
₁₆ as ON state, the anode potential of the diode 25 is clamped to -3 V _F, becomes the interruption state diode 25 is reverse biased, the operational amplifier 19 is separated from the control system. To control the output voltage _VL to a positive voltage, a negative voltage _VA is applied to the input terminal 11. In this case, the saturation prevention circuit 53 sets the voltage _VA so that the diodes D _{1 to} D ₃ are not turned on. It becomes an output voltage V _a positive operational amplifier 17, the collector current i of the transistor 38 in accordance with this
_b increases, the input current _ic of the output amplifier 43 becomes a negative current, the output current _IL becomes a positive current, and the output voltage _VL of the output terminal 45 becomes positive.
Is input to the operational amplifier 17 through resistors 14 and 48
Are equal in magnitude and opposite in polarity. That is, when the resistance values of the resistors 14 and 48 are the same, the output voltage _VL is a positive voltage having an absolute value equal to the voltage _VA of the input terminal 11.

Similarly, when it is desired to set and control the output voltage _VL to a negative voltage, a positive voltage _VA is applied to the input terminal 11;
The collector current of the transistor 35 increases, and the input current _ic of the output amplifier 43 becomes a positive current.
_L becomes a negative current, a negative output voltage _VL is obtained, and this output voltage _VL corresponds to the input voltage _VA .

In any case, in the steady state, the transistor 3
Collector current i of 5_aAnd the collector of transistor 38
Flow i_bIs equal to Positive output current for load 46
Is controlled, a sufficiently large negative voltage is applied to the input terminal 11.
V_AIs input to the diode D of the saturation prevention circuit 53._Three,
D_FourAnd the cathode of the diode 22 is set to +
2V_FTo the diode 22 and the reverse via to the diode 22.
The operational amplifier 17 from the control system
Release and control in the same manner as in the output voltage control described above.
The anode of Iode 25 is -3V _FTo calculate
The amplifier 19 is separated from the control system. At this time, transistor 3
+ V between base and emitter of 8_FThe voltage corresponding to
And the corresponding constant current i_bIs the transistor 38
It flows as a collector current. In this state, the input terminal 12
The diode D of the saturation prevention circuit 54_Five~ D_TenTurns on
Negative voltage V_Bgive. Therefore, the power
The collector current i of the transistor 35_aBut
And the input current i of the output amplifier 43_cIs a negative current
Output current I _LBecomes a positive current. The positive output current I_L
Voltage V of the current detection resistor 44 based on the_MIs increased
It is returned to the width unit 18 and flows to the resistors 15 and 51, respectively.
Currents act so that the directions are equal and opposite in direction,
Voltage V_BOutput current I according to_LIs obtained.

In order to set and control the output current _IL to a negative current, as described above, + V _{F is applied} to the cathode of the diode 24 to separate the operational amplifier 18 from the control system, and to apply a positive voltage to the input terminal 11. Applying _VA and preventing saturation 53
The diodes D ₁ and D ₂ are turned on to apply −2 V _F to the anode of the diode 23 to shut off the operational amplifier 17 from the control system. At this time, a voltage corresponding to -V _F is applied between the base and the emitter of the transistor 35, a constant current i _a is the transistor 3 corresponding thereto
5 flows as a collector current. In this state, input terminal 1
3 is applied with a positive voltage V _{C such} that the diodes D _{11 to} D ₁₆ of the saturation prevention circuit 55 do not turn on. The potential of the connection point 31 is down in response to this, decreases the collector current i _b of the transistor 38 becomes the input current i _c is positive of the output amplifier 43 becomes the output current I _L becomes negative. Drop voltage V _M of the resistor 44 due to this current is fed back to the operational amplifier 19,
Resistors 16, 52 to equal the magnitude of the current flowing through each operate such that the opposite polarity, the negative output current I _L corresponding to the voltage V _C is obtained.

[0009]

[SUMMARY OF THE INVENTION For example, in the setting control state to the positive output current I _L, as shown in FIG. 9B to set current control input voltage V _B as shown in FIG. 9A as a slightly negative value, It is assumed that a small positive output current I _L flows and a small positive output voltage V _L is generated as shown in FIG. 9C. At this time, when the control system is in equilibrium,
i _a = i _b , the voltage at the node 31 is + V _F ,
Thus the voltage at node 26 is -V _F, operational amplifier 1
8 the output voltage V _b is -2V, as shown in solid line in FIG. 9D _F of
It has become. Output voltage V _a of the operational amplifier 17 as described above is clamped to + 2V _F, also the operational amplifier 19
The output voltage V _c of which is clamped to -3 V _F. The diode 24 is turned on as shown in FIG. 9E, the diode 22 is turned off as shown in FIG.
9G is in the ON state as shown in FIG.
As shown in H, it is in the OFF state.

[0010] time t ₁ as shown from the state in FIG. 9A
When setting the input voltage V _B by increasing stepwise in the negative direction a positive output current I _L on a large, the moment, the current flowing through the resistor 15 and 16 become unbalanced, the operational amplifier 18 is operational to operate at a range, the output voltage V _b of the operational amplifier 18 to be limited by the diode D ₈ to D ₁₀ of the saturation prevention circuit 54 is soaring, as shown in solid line in FIG. 9D, +
It becomes 3V _F. Therefore, the diode 24 is reverse-biased, and is turned off as shown in FIG. 9E, and the diode 22 is turned on as shown in FIG. 9F. Therefore, the collector current i _a is instantaneously reduced, the load current I _L as shown in FIG. 9B is increased instantaneously. This current _IL is fed back to the operational amplifier 18 via the differential amplifier 49,
Since it takes a little time for the two currents flowing through 5, 51 to equilibrate, the load current I _L flows in a spike state, thereby generating a spike-like output voltage V _L and then to a steady state. As described above, there is a disadvantage in that a spike-like abnormal voltage is applied to the load 46.

In FIG. 9, the voltage V _B of the input terminal 12 is shown.
Is increased in the negative direction as shown at time t ₂ in FIG. 9A, the output current I _L and the output voltage V _L also increase, and the current flowing through the resistor 14 48, the current flowing through 48 becomes large in absolute value, and the diodes D ₃ and D _{4 of the} saturation prevention circuit 53 are turned off.
Small next by the output voltage V _a is 2V _F of the operational amplifier 17, i _a is increased, I _L decreases, so that both the current flowing through the resistor 14 and 18 are balanced, negative feedback control is performed,
The output voltage V _L is determined by the voltage V _A of the input terminal 11. That is, a positive voltage is generated (voltage control).

[0012] In a positive current control state, when a positive output current I _L is set to near zero, the offset voltage of the operational amplifier 18, there is the output current I _L is negative. Resistance is very large in this case the load 46 is not detected current by the current detecting resistor 44, if no fragments feedback by the voltage V _M, the output current I _L turn in the negative direction. Since the operational amplifier 17 is in the positive voltage control state, the negative output voltage _VL at this time cannot be controlled, and as a result, the maximum negative voltage that can be generated by the output amplifier 43 is supplied to the load 46. As a result, the load 46 may be damaged. Even in the negative current control state, the maximum positive voltage may be supplied to the load 46 for the same reason.

[0013]

According to the present invention, a positive output voltage state, a negative output voltage state, a positive output current state,
Each of the negative output current states is controlled by a separate operational amplifier. Therefore, four operational amplifiers for control are provided. All of these operational amplifiers are connected to a saturation prevention circuit that can be switched to one of three types of clamp states that determine an operation range. In any of the four output states, three of the four operational amplifier outputs are switched and selected by the mode switching circuit, one for output and the other for limiter, and the three outputs are supplied to the diode switch circuit. Is done. That is, in the voltage output state, the corresponding voltage control operational amplifier is selected for output and the two current control operational amplifiers are selected for the limiter by the mode switching circuit. In the current output state, the corresponding current control operational amplifier is selected. Are selected for output, and two voltage control operational amplifiers are selected for the limiter.

[0014]

FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 4 are denoted by the same reference numerals. In the present invention, the input terminals 11p and 11p for the positive voltage and the negative
n are provided, and input terminals 11p and 11n are connected to respective inverting input terminals of operational amplifiers 17p and 17n, respectively. The non-inverting input terminals of the operational amplifiers 17p and 17n are respectively grounded, and the saturation prevention circuits 53p and 53n are connected between the input and output terminals. The output side of the buffer circuit 47 is a resistor 48
operational amplifiers 53p and 53n through p and 48n, respectively.
Are connected to the respective inverting input terminals.

A mode switching circuit 61 is provided to output a setting.
The operational amplifiers 17p, 17n, 18, 1
3 each of which is selected as a diode switch circuit
21. Switch S for mode switching circuit 61
₉~ S_{twenty four}And a switch S₉~ S₁₂One end of the die
Switch S connected to the cathode of₁₃~ S ₁₆
Are connected to the cathode of a diode 22 and
Switch S₁₇~ S₂₀Is connected to the anode of the diode 23
Connected, switch S_{twenty one}~ S_{twenty four}One end of the diode 2
5 anode. Output side of operational amplifier 17p
Is the switch S_Fifteen, S₁₆, S₁₇Connected to the other end of the
The output side of the amplifier 17n is a switch S₁₄, S₁₉, S₂₀Each of
The other end is connected, and the output side of the operational amplifier 18 is connected to a switch S
₉, S_Ten, S_{twenty three}Of the operational amplifier 19
Output side is switch S₁₂, S_{twenty one}, S _{twenty two}Connected to each other end
And switch S₁₁, S₁₃, S₁₈, S_{twenty four}Each other end is grounded
It is.

The saturation prevention circuits 53p, 53n, 54, 55
Respectively, four diodes connected in series in the forward direction and three diodes connected in series in the forward direction are connected in parallel in the reverse direction, and one diode connects the three series diodes and the switch. And a switch connected in parallel with one of the output terminals of the operational amplifiers of the three series diodes. The saturation prevention circuits 53p and 54 are connected to the output terminals of the operational amplifiers corresponding to the anodes of the three series diodes, and the saturation prevention circuits 53n and 55 are connected to the output terminals of the operation amplifiers corresponding to the cathodes of the three series diodes. Connected to. In the saturation prevention circuits 53p, 53n, 54, and 55, a switch in series with one diode is connected to each S
_1, S _3, and S _5, S _7, to each one diode in parallel with switches and _{S 2, S 4, S 6} , S 8 , respectively.
Thus each saturation prevention circuits 53p, 54, the output of the corresponding operational _{amplifier, + V F, + 2V F} , or + 3V _F
Hereinafter, clamping the operating range either above -4 V _F,
Each saturation preventing circuit 53n, 55, the output of the corresponding operational amplifier, -V _F, -2 V _F, or -3 V _F above,
The operating range is clamped below + 4V _F. That is, one saturation prevention circuit is switched to one of three types of saturation prevention circuits (clamp states) shown in the saturation prevention circuits 53p, 54, and 55 of FIG. 3A according to the mode setting state.

The switches S _{1 to} S ₂₄ are set as shown in FIG. 2 according to the desired output state. In FIG. 2, 0
Indicates off, 1 indicates on, and-indicates indefinite. That is, when a positive constant voltage is generated, the output of the operational amplifier 17p is supplied to the diode 23 for control, and the outputs of the operational amplifiers 18 and 19 are supplied to the diodes 24 and 25 for limiters. When a negative constant voltage is generated, the output of the operational amplifier 17n is supplied to the diode 22 for control, and the outputs of the operational amplifiers 18 and 19 are supplied to the diodes 24 and 25 for limiters. When the positive constant current is generated, the output of the operational amplifier 18 is supplied to the diode 25 for control, and the outputs of the operational amplifiers 17p and 17n are supplied to the diodes 22 and 23, respectively, for the limiter. The output of 19 is a diode 24
, And the outputs of the operational amplifiers 17p and 17n are supplied to diodes 22 and 23, respectively, for limiting. A switch in parallel with one diode in the saturation prevention circuit connected to the operational amplifier used for control is turned on.

In the positive constant voltage generation setting state, the switch S
₁~ S_{twenty four}Is set as shown in FIG. 1 and thus in FIG. 3A
The circuit state shown in FIG. The cathode of the diode 22 is grounded
And the voltage V at the cathode of the diode 22_fIs OV
The voltage V at the connection point 26 _iIs the direction of the diode 22
Direction drop voltage V_FBecomes A negative voltage V is applied to the input terminal 12._BBut
And the output V of the operational amplifier 18_bIs the saturation prevention circuit 5
Fourth diode D₁₇Is turned on and + V_FClamped on
Have been. This output V_bAnd diode 24 Cassaw
Voltage V_eAre equalized, and this voltage V_b, V_e
Is the diode D in the saturation prevention circuit 54₁₇Voltage drop + V
_FAnd the voltages across the diode 24 are equal,
Aether 24 is turned off. On the other hand, the load voltage V_LAnd negative
Load current I _LIs constant, both collector currents are equal and i_a
= I_bTherefore, the voltage V at the connection point 31_iIs -V_FTona
You. Therefore, the output V of the operational amplifier 17p_ap, Diode 2
3 cathode voltage V_gTurns diode 23 on.
OV because of the potential. At this time, the input terminal 11p
Input voltage -V_APDivided by the resistance of resistor 14p
And the output voltage V of the terminal 45_OWith the resistance of the resistor 48p
An operational amplifier 1 so that the divided current becomes equal in the opposite polarity.
7p works.

Output V _C diode 25 of operational amplifier 19
The positive voltage V _C is applied to the input terminal 13 of the anode voltage V _h , and the output V _C of the operational amplifier 19 is the saturation prevention circuit 55.
Are clamped to -3V _F by the diodes D30, D31 and D32. Therefore, the diode 25 is turned off. Therefore, the operational amplifiers 17n, 18, and 19 are electrically disconnected from the entire control system, and the load 46 is controlled by the operational amplifier 17p to a positive constant voltage generation state.

In this state, the load current I_LIncreases the resistor
The sum of the current flowing through the resistor 15 and the current flowing through the resistor 51 is positive.
, The output V of the operational amplifier 18_b, Diode 24
Cathode V_eBecomes negative and the diode 24 turns on.
You. Therefore i_aIncreases and the load current I_LDecreases and the output
Voltage V_ODecreases, the current flowing through the resistor 14p and the resistance
The sum with the current flowing through the filter 48p becomes negative, and the saturation prevention circuit
53p diode D ₆, D₇Is turned on and the operational amplification
Output of the unit 17p_ap, The voltage at the cathode of the diode 23
V_gIs + 2V_FBecomes constant, and the operational amplifier 17p
Control stops. As a result, the voltage V_jIs +
V_FBecomes Voltage V at connection point 27_iIs i_a= I_bNana
-V_FAnd the operational amplifier 18
Output V_RIs -2V due to the voltage drop of the diode 24._F
become. Classification of the operational amplifier 18 by the saturation prevention circuit 54
Pump voltage is -4V_FTherefore, the saturation prevention circuit 54 operates.
No positive constant current is generated by the operational amplifier 18
Controlled raw.

[0021] Figure 5 sets the mode to a positive constant voltage generating state, the load 46 and a resistive load, and a positive constant voltage generation control voltage V _AP is increased from OV in the negative direction to be given to the input terminal 11p, the load The state of each part when the voltage _VL is increased from OV in the positive direction is shown. When large in the negative direction than a certain a V _AP, positive from the state of the constant voltage control by the operational amplifier 17p, it can be seen that switched to a positive constant current control state by the operational amplifier 18.

FIG. 3B shows a connection of a circuit in a state where a positive constant current is generated.
Fig. 6 shows the mode set to the positive constant current generation state.
The load 46 is a resistive load, and the positive
Constant current generation control voltage V_BIncreases in the negative direction from near negative OV
The load current I _LFrom the vicinity of positive OA to square
The state of each part when increasing in the direction is shown. Time t₁And V
_BIs slightly increased when stepping in the negative direction.
The device 18 has an output V at its maximum operable state._bRises
And the diode D of the saturation prevention circuit 54_{twenty two}, D_{twenty three}Is on
And + 2V_FAnd the transistor
Controlling the star 38, i_bAnd the load current I_LThe square
Increase in the direction. At this time, the output side of the operational amplifier 18 is
8 unlike the prior art, from the cathode of the diode 24
Since it is disconnected, the diode 24 is momentarily turned off.
Instead, a spike-like current or voltage is applied to the load 46.
There is no fear.

[0023] As you further increase the V _B in the negative direction as can be seen from FIG. 6, similarly to the conventional operational amplifier 17p
Is switched to a positive voltage generation state. Further, when a current is generated near the positive OA and the resistance of the load 46 is extremely high, the load 46
However, even if a slight negative current flows and the voltage _{VL of the} load 46 tends to increase in the negative direction, the state is switched to a negative voltage generation state by the operational amplifier 17n, and the load voltage _VL does not significantly increase.

FIG. 4A shows a connection state of the circuit when a negative voltage is generated, and FIG. 4B shows a connection state of the circuit when a negative current is generated. It is easily understood that the operations in these are performed in the same manner as in the related art, without any particular explanation. Said Japanese Utility Model Application No. 61-15551
As shown in FIG. 7, in the present invention, the voltage-current conversion circuits 37 and 41 may be configured using constant current circuits as shown in FIG. Switch S ₁ to S ₂₄ is a semiconductor, it may be constituted by a switch.

[0025]

As described above, according to the present invention, in addition to the operational amplifier for generating a positive constant voltage, an operational amplifier for generating a negative constant voltage is provided, and the mode switching circuit controls the positive constant voltage control state and the negative constant voltage. In the control state, in each case, the positive and negative current control operational amplifiers 18 and 19 are connected to a diode switch circuit as a limiter, so that an excessive voltage and an excessive current are prevented from flowing. In either case, in the negative constant current control state, the positive and negative voltage control operational amplifiers 17p and 17n are connected to the diode switch circuit as limiters to prevent an excessive current and an excessive voltage from being applied. . In addition, since only the three necessary operational amplifiers are always connected to the diode switch circuit, there is no possibility that the spike-like voltage and current are applied to the load when the set current and voltage are changed in a step-like manner.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing ON / OFF setting of switches S _{1 to} S ₂₄ in FIG. 1 according to each setting mode.

3A is a diagram illustrating a connection state of FIG. 1 in a positive constant voltage generation state, and FIG. 3B is a diagram illustrating a connection state of FIG. 1 in a positive constant current generation state.

4A is a diagram illustrating a connection state of FIG. 1 in a state of generating a negative constant voltage, and FIG. 4B is a diagram illustrating a connection state of FIG. 1 in a state of generating a negative constant current.

FIG. 5 shows a positive constant voltage control voltage V in a positive constant voltage generation state.
₆ is a time chart showing the state of each unit when _AP is increased in a negative direction.

FIG. 6 shows a positive constant current control voltage V in a positive constant current generation state.
₆ is a time chart showing the state of each part when _B is increased in the negative direction.

FIG. 7 is a block diagram showing another embodiment of the present invention.

FIG. 8 is a connection diagram showing a conventional amplifier with a switching control circuit.

[9] As a positive constant current control voltage time chart showing the states of the respective units of the case of increasing the V _B in the negative direction in the amplifier of FIG. 8 in a positive constant current generating state.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein one of a plurality of operational amplifiers is selected by a diode switch circuit in accordance with a set input signal or a load state, and an output voltage of the diode switch circuit is converted into a current and supplied to an output amplifier. An amplifier with a switching control circuit configured to control the output amplifier by the output of the operational amplifier, wherein the plurality of operational amplifiers include a positive output voltage state, a negative output voltage state, a positive output current state, and a negative output voltage state. An operational amplifier for controlling the output current state is provided. Each of the operational amplifiers has a saturation prevention circuit that can be switched to one of three types of clamp states that determine an operation range according to the setting state of the generated output. Connected, any one of the above four output states, one of them is for output, and the other two are for limiter A switching control circuit, wherein three output sides of the four operational amplifiers are taken out, and a mode switching circuit for supplying the taken out outputs of the three output sides to the diode switch circuit is provided. With amplifier.