JPS5815485A - Current source bridge type servo-amplifying circuit - Google Patents

Abstract

PURPOSE:To improve the following property of a current source bridge type servo-amplifying circuit after a control input signal by a method wherein a switching circuit at the final stage is changed over according to change between positive and negative of the control input signal, and moreover conducting time of the switching circuit is controlled according to the control input signal. CONSTITUTION:When a positive voltage is applied as the control input signal Vi, a signal DLi is converted into ''1'', and a switching circuit SW5 is closed to make an amplifier 20 to operate in the inverse mode. Because output VO of a comparing circuit 3 is made to have a negative voltage, output of the amplifier 20 is made to have a positive voltage, and a pulse signal having pulse duration corresponding to largeness thereof is outputted from a PWM circuit 6. While a signal A1 is converted into ''1'' after delay time to be generated by a delay circuit 24, and when an enabling signal is ''1'' at that time, the switching circuits SW4, SW1 are made to conduct. Accordingly a motor 1 is rotated in the positive direction. A current flowing in the motor 1 is fed back to the comparing circuit 3 through a current detecting circuit 2 .

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current source bridge type servo amplifier circuit used for speed control of a DC motor.

Current source bridge type servo amplifier circuits are widely used for speed control of DC motors.

The principle is, as shown in FIG. 1, four switching circuits S Wl are bridge-connected between the positive side line V of a DC voltage source and the earth line GND.

SW2. SW3. A DC motor (hereinafter simply referred to as "motor") 1 is connected between equilibrium points a and b of SW4,
The control signals 81 to 84k of these four switching circuits are controlled according to the control input signal, and the switching circuit SWI
and SW4 or SW2 and SW3 are all selectively made conductive (a state in which current flows), and the conduction time or degree of conductivity is fully controlled to control the direction and magnitude of the current flowing to the motor 1. This is the circuit.

Semiconductor elements such as transistors are used as the final stage switching circuits SWI to S'W4 in such a servo amplifier circuit, but due to the delay in switching time, for example, the switching circuit S in FIG.
A short mode may occur in which Wl and SW2 are in a conductive state (in the following description, for convenience, the conductive state will be referred to as "on" and the non-conductive state will be referred to as "off").

That is, in the circuit of FIG. 1, the control signal S"+84
A signal having a waveform as shown in FIG. 2(a) as a control signal 82. When a signal as shown in the figure (b) is applied as sa, the on/off operations of the switching circuits SWI, SW4 are delayed as shown in the figure (c), and the switching circuits SW2. The on/off operation of SW3 is also delayed, as shown in FIG. 4(d).

Therefore, there is a possibility that a short mode may occur during the time period indicated by hatching in FIG. 2.

Therefore, when constructing such a current source bridge type servo amplifier, it is necessary to provide a circuit to avoid the short mode, and an example of a conventional current source bridge type servo amplifier circuit provided with this circuit is shown in FIG.

In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals. R1 and R2 are current detection resistors that generate voltages in accordance with the current flowing through the motor 1 in the direction of arrow A and the direction of arrow B, respectively. 2 is a current detection circuit, and operational amplifier OP
When inputting the voltage generated at I and input resistance R3゜I' (4, consisting of grounding resistor R5 and feedback resistor R6, resistor R), a corresponding negative voltage is output, and the voltage generated at resistor R2 is completely input. When this occurs, the corresponding IE voltage is output.

6 is a comparison circuit, which receives the control human power signal from the input terminal 4 (
? 1j pressure signal) Vi and the output voltage Vf of the current detection circuit 2 are compared, and a voltage signal \lO having a polarity and magnitude according to the magnitude relationship I and the difference is outputted. That is, Vi and Vf, which are voltage signals with different polarities, are added via resistors R, 7, R, and g, and the difference is calculated by adding the difference between the voltage signals Vi and Vf, which are voltage signals of different polarities, and calculating the difference between them by an integrating-type inverting amplifier (low-pass filter action) consisting of operational amplifier OP2, resistor Rq, and capacitor C. ) is manually inverted and amplified.

5 is an absolute value circuit that outputs the absolute value IV01 of the output ■0 of the comparator circuit 3, and 6 is a pulse width modulation circuit (abbreviated as "P~M circuit"), which outputs the absolute value circuit at a constant frequency. 5 output IVO1 to 1. Outputs a pulse signal with a consistent pulse width.

7 is a comparator that determines whether the output VO of the comparison circuit f) i'i, '5 is positive or negative; when Vo is +E, the output is set to high level "'1°'", and when it is negative, it is set to low level "Q"
Nissl.

A, NI) thereby selectively open gates 8 or 9 to supply pulse width modulated pulse signals from switch circuit SW1 or 5W3 (two PWM circuits 10 is a circuit to avoid short mode, and stable multi 11,
12, inverter 13, 15.01 (consisting of 7 gates 14. and AND gate 16).

Then, when the output Vo of the comparator circuit 6 swings to iE negative as shown in FIG. CPo changes as shown in the same figure (C).

Therefore, the output O8i of the monostable multi 11.12.

O8z, output OR, o of OR gate 14, inverter 1
The output INo of 5 is shown in Fig. 4 (d), (e), and (f), respectively.
(g) +: As shown, the output I of the inverter 15
While No is at a low level "0°", the AND gate 16 is P.
Since the output pulse of the WM circuit 6 is not passed through, the switching circuits SWl and SW3 are turned off.

Note that 1] 1 to D4 are each switching circuit SW1 to SW
This is a diode for erasing the reverse voltage that occurs when 4 is turned off.

In such a current source bridge type servo amplifier circuit, when a voltage is applied to the input terminal 4 as the control human power signal v1, the output VO of the comparator circuit B becomes a negative voltage, and the output of the comparator 7 becomes uO++.

Therefore, the output of the inverter 16 becomes "'1",
While turning on the switching circuit SW2, A, ND
The gate 19 is opened and the output pulse of the PWM circuit 6 is supplied as a control signal to the switching circuit SW3, and the switching circuit SW3 is turned on with a corresponding conduction time (duty).

As a result, a current flows in the direction of arrow A to the motor 1, causing the motor 1 to rotate in the normal direction.

At this time, the current flowing through the motor 1 is detected by the current detection circuit 2, and its output voltage (negative voltage in this case) Vf is fed back to the comparator circuit 6, and the pulse width of the PWM circuit 6 is determined by the difference with the control human power signal Vi. The current flowing through the motor 1 is controlled by changing the conduction time of the switching circuit SWa so that the motor 1 rotates at a speed corresponding to the control input signal.

When a direct voltage is applied as the control human power signal V1, the output vO of the comparison circuit 6 becomes the IE voltage, and the output CP ( ) of the comparator 7 becomes ゛l'', so the switching circuit SW4 turns on and SW 1 An output pulse from the PWM circuit 6 is generated, and a current flows through the motor 1 in the direction of arrow 13, causing it to rotate in the reverse direction.

At this time, the output Vf of the current detection circuit 2 becomes a positive voltage and is fed back to the comparison circuit 6.

In this way, when the control input signal changes only on the positive or negative voltage side, the output of the comparator circuit B is often a negative or positive voltage. On the other hand, since the output change of the current detection circuit 2 is delayed, the control input signal V1 and the output Vf of the current detection circuit 2 are delayed.
The magnitude relationship of each absolute value of is reversed, and the output of the comparator circuit B changes from a negative voltage to a positive voltage, as shown in FIG. 4(a).
Alternatively, the IF voltage may change to a negative voltage.

At that time, the short mode avoidance circuit 10 operates, and after turning off both switching circuits SW1 and SW3 for the time set by the monostable multi 11 or 12, the current flows through the motor 1 in the opposite direction. The switching circuits S W t to S W4 are switched.

As a result, the output V (l is in the negative voltage direction (
Or try to return to 1F (voltage direction).

When the output voltage (1)0 crosses zero, the short mode avoidance circuit 10 operates again, and the switching circuits SWI and SW3 are always turned off.

While the switching circuits SWI and SWa are off, the current detection circuit 2 cannot accurately detect the current flowing through the motor 1.

Therefore, when the circuit that avoids the automatic mode operates, the followability and stability of the human control signal deteriorate.

Therefore, for example, when performing constant velocity control in a reciprocating scanning mechanism, a problem arises in that stable constant velocity control cannot be performed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a current source bridge type servo amplifier circuit that has good followability for a control input signal.

Therefore, the current source bridge type 11-servo amplifier circuit according to the first invention has the advantage that the current source bridge type 11-servo amplifier circuit according to the first invention
(2) The switching circuit of the final stage is not switched due to a change in box characteristics (zero cross). The output signal of the circuit is inverted or non-inverted amplified depending on the sign of the control input signal, and the conduction time or degree of conduction of the switching circuit which is made conductive is controlled by the output.

In addition to the first invention, a second invention provides a method for inputting a direction designation signal that designates the rotational direction of the DC motor in addition to the control human power signal, and switching the final stage using the direction designation signal. Enables circuit switching,
In that case, the circuit for avoiding short mode is made inoperative.

Furthermore, a third invention, in addition to the first invention, reduces the number of positive/negative reversals by adding a constant bias voltage to the control input signal, thereby achieving constant velocity control with better followability. The purpose of the present invention is to provide a servo amplifier circuit with 12 functions.

JJ, below, the present invention will be described in detail with reference to FIG. 5 and subsequent figures of the accompanying drawings.

Figure 5 shows the 1. It is a block circuit diagram of a current source bridge type bass amplifier circuit in which the second invention is put into practice;
Parts that are the same as those in the drawings are designated by the same reference numerals, and explanations of those parts will be omitted.

In this embodiment, the output signal vO of the comparator circuit B is amplified by an amplifier 20 capable of switching between inverting and non-inverting modes.
It is input to the WM circuit 6. Amplifier 20 is an operational amplifier O
Pa input resistance Rho, Rt+.

It consists of a feedback resistor R12 and a switching circuit SW5, and when the switching circuit SW5 is turned on, it functions as an inverting amplifier, and when it is turned off, it functions as a non-inverting amplifier.

This switching circuit SW5 is controlled by human control power and a discrimination output from a comparator 21, which is a discrimination circuit that discriminates whether the signal Vi is positive or negative. That is, the control input signal V
When i is positive, the output of the comparator 21 becomes ``l'', which turns on the switching circuit SW5 through the OR gate 22. When the control human input signal 1 is negative, the output of the comparator 21 becomes ``0''. , the switching circuit SW5 is turned off via the gate 22. It is desirable that the comparator 21 has hysteresis characteristics.

Note that the resistor R13 and the diode D5 connect the PWM circuit hydraulic power to the diode 1)5 when the output of the amplifier 20 is negative.
In order to clamp only the forward voltage of 2 minutes (- is inserted).

On the other hand, the output of the comparator 21 with four OR'y'-totes 22 is the output of the circuit 26. It is applied as a conduction selection signal to the final stage switching circuits SW] to SW4 via an A N D gate 27.28°8.9 for controlling the operation of the servo amplifier.

The circuit 26 to avoid the short mode consists of the delay circuit 24, its human input signal 1) Li and the output signal 1] LO, and the positive input A, ND gate 25 and the negative input A, ND, gate 26, etc. It is configured.

As the delay circuit 24, for example, a circuit as shown in FIG. 6 is used.

If the human input signal DT of the delay circuit 24, that is, the output signal of the comparator 21 changes as shown in FIG. 7(a), the delay circuit 24 delays it by a preset delay time Td and outputs it. Therefore, the output signal becomes as shown in ())) in the same figure.

As shown in the same figure (C), the output of the AND gate 25 is 1''' when both the signals D L + and D L o are 1'', and the output of the AND gate 26 is As shown in the same figure (c), A2 is the signal f) L i and D L
It becomes 1'' only when o are both 0''.

Therefore, during a period corresponding to the delay time Td by the delay circuit 24, the outputs of the AN and D gates 25 and 26 are both 0''.
Since the outputs of the A and ND gates 27 and 28 are also set to 0', all of the final stage switching circuits SW1 to SW4 are turned off, and the occurrence of the 7-yaw mode when switching the switching circuits is avoided.

Reference numeral 29 is an input terminal for a direction 1 determination signal that specifies the rotation direction of the DC motor 1. When this direction designation signal is set to 15-1''', the output of the comparator 21 (- the motor 1 rotates in the positive direction). can be done.

60 is a good-pull signal terminal, and when this enable signal is '1'', it becomes a servo amplifier circuit -pull,
When it is 0''', the servo amplifier's knee pull makes a loud noise.

In the servo amplifier circuit configured as described above, when a positive voltage is applied as the control input signal V1, the output of the comparator 21 becomes 1'', and the switching circuit SW5 of the amplifier 20 is closed and the amplifier 20 enters the inversion mode.

Since the output vO of the comparator circuit 6 becomes a negative voltage, the amplifier 20
The output becomes the city voltage, and a pulse signal with a pulse width corresponding to the magnitude thereof is output from the PWM circuit 6.

On the other hand, after the delay time by the delay circuit 24, the AND gate 2
5's output A1 becomes °°1", so if the enable signal is 1111+, the output of AND gate 127 becomes '
l"i2, the switching circuits 16-8 to V4 are turned on, and the ?I/S signal from the ?WM circuit 6 is applied as a control signal to the switching circuit SW1 through the AND gate 8, and its Conduction time is controlled.

As a result, a current flows through the motor 1 in the direction of arrow A in FIG. 5, and in this example where the motor 1 rotates forward, it is opposite to the conventional example shown in FIG. 6). The current flowing through the motor 1 is detected by the flying current detection circuit 2, and the negative detection voltage Vf is fed back to the comparison circuit B.

Even if the absolute value of this detected voltage Vf becomes larger than the absolute value of the control human power signal 1 and the output voltage vO of the comparator circuit B changes from negative to positive, the direction of the current flowing through the motor 1 The switching circuits SW1 to SW4 that determine the PWM
A constant small voltage is input to the circuit circuit circuit water diode D5, and generally the motor 1 is supplied with the arrow A in order to make the pulse width of the output pulse a constant small width.
A small current continues to flow in the direction.

The switching circuits SW] to SW4 are switched as follows.
Only when the control human input signal changes from positive to negative or from negative to positive (4), the short mode avoidance circuit 26 operates to avoid the short mode 1 and switch the switching circuit SW. ]~S~■4 (2-switch, reverse the direction of the current flowing through the motor 1.

In this way, unnecessary switching of the switching circuit and circuit operation to avoid short mode when the control input signal is changing on one side of the IE or color can be avoided, and the circuit has good followability to the control human input signal. It can be made into a servo amplifier circuit.

By the way, when the servo amplifier circuit according to the present invention is used in a reciprocating scanning mechanism, especially a mechanism that performs constant velocity control in the past,
The configuration is as shown in FIG.

The control power signal 1 of the servo amplifier circuit (the circuit excluding the motor 1 in FIG. 5) 61 is controlled by the positive reference voltage Vr and the rotational speed of the motor 1 by the pulse encoder 62 and the fV variable IA circuit 33i1. Detected negative voltage VV
Therefore, the polarity will be reversed by 1 at the time of rising or when the actual speed becomes faster than the target speed due to some reason.

As a result, switching of the final stage switching circuits SW1 to SW4 in FIG. 5 occurs, resulting in poor followability.

Therefore, in such a case, a high level direction designation signal II II+ is manually input to the input terminal 29 in FIG.
~If SW4 is fixed so as not to switch, constant velocity control with more stable followability can be performed.

For example, when scanning the exposure optical system of a copying machine, the switching circuit is fixed with the direction designation signal set to "]" during forward movement, and the direction designation signal is set to °"0" during backward movement, and the control is manually controlled by the comparator 21. It is preferable to switch according to the signal discrimination result.

Furthermore, when controlling the reciprocating scanning mechanism, a circuit that supplies a constant current to overcome the frictional force of the motor scanning mechanism;
For example, as shown in FIG. 9, a control 19--a circuit for adding a constant bias voltage to the human input signal is provided,
To reduce the number of times the output of the comparator 21 shown in FIG.

The circuit shown in FIG. 9 includes an amplifier 40 that can switch between inverting and non-inverting modes, and an inverting amplifier circuit 41 for addition that adds the output voltage of the amplifier 40 to the control input signal Vi.

The switching circuit SW6 of the amplifier 40 operates in the scanning direction (1
The amplifier 40 is controlled to be on/off by a switching signal S (I) output accordingly, and is turned on during forward scanning, for example, so that the amplifier 40 operates as an inverting amplifier and generates a constant positive voltage Vc.
is inverted and amplified to create a bias voltage for the casing.

In this case, the control input signal vI during forward scanning is a negative voltage, and is inverted and amplified by the inverting amplifier circuit 41 by adding the bias voltage from the amplifier 40, and the positive control input signal V II
Then, the input terminal 4 in FIG. 5 is manually inputted.

120-1, 7. As explained in the embodiments (2. The current source bridge amplifier circuit according to the present invention can perform control with good followability to the control force signal, In particular, constant speed control of a reciprocating scanning mechanism, etc. (one degree is effective).

Furthermore, if the circuit to avoid the short mode is configured by an AND gate with a positive input and a negative input that ANDs the delay circuit and its input signal and output signal, as in the embodiment shown in FIG. The configuration is much simpler than the conventional circuit shown.

In addition, in the embodiment, an example was explained in which on/off control is performed by the output of a PWM circuit, which is a switching circuit, and the conduction time (duty) is controlled according to the pulse width. Of course, it is also possible to perform linear control according to the output (1).

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a bridge configuration with four switching circuits used in a current source bridge type servo amplifier circuit, and Figure 2 is a waveform that also explains the delay in on/off operation of each switching circuit. 6 is a circuit diagram showing an example of a conventional current source bridge type bass amplifier circuit. FIG. Fig. 5 is a circuit diagram showing a practical example of the present invention, Fig. 6 is a circuit diagram showing a specific example of the delay circuit, and Fig. 7 is a circuit diagram showing the operation of the circuit to avoid the short mode. Figure 8 is a block configuration diagram of a constant velocity control mechanism using a servo amplifier circuit, Figure 9 is a circuit for adding a constant bias voltage to the control human input signal. It is a circuit diagram showing an example. 1...DC motor 2...Current detection circuit 6.
... Comparison circuit 6 ... Pulse width modulation circuit 20
...Amplifier 21 capable of switching between inverting and non-inverting modes...Comparator (discrimination time i?8) 26
・・Circuit SW l-8-V4・
... Switching circuit applicant Rico Co., Ltd.
- Figure 7 Figure 8 Figure 9 Procedural amendment (voluntary) December 29, 1981 1, Indication of the case Patent application No. 110667/1982 2, Name of the invention Current source bridge type plasma amplifier circuit 3, Relationship with the case of the person making the amendment Patent applicant Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (674,) Agent 5-5 Amendment, 1-20 Higashiikebukuro, Toshima-ku, Tokyo Content 6 Contents of amendment (1) “Same figure (C
)” is corrected to “(d) in the same figure”. (2) "Servo amplifier disable" on page 17, line 6 of the Circular is corrected to "servo amplifier disable."

Claims (1)

[Claims] 1. A DC motor is connected between the equilibrium points of four switching circuits bridge-connected to a DC voltage source, and two of the four switching circuits are set to short mode in response to a control input signal. In the current source bridge type vacuum amplifier circuit, the direction and magnitude of the current flowing through the DC motor are controlled by selectively making the current conductive through a circuit that avoids the direct current and controlling the conduction time or degree of conductivity. , a current detection circuit that detects the current flowing through the DC motor, and compares the output signal of this current detection circuit with the control input signal, and determines the polarity and boldness according to the person/total relationship and the difference. A comparison circuit that outputs a signal, an amplifier capable of switching between inverting and non-inverting modes that inputs the output signal of the comparison circuit and amplifies it in inverting or non-inverting, and a discrimination circuit that discriminates whether the control input signal is positive or negative, Based on the discrimination output of the discrimination circuit, the mode of the amplifier is switched, and two switch circuits to be rendered conductive among the four switch circuits are determined, and the conduction of the switch circuits to be rendered conductive is determined according to the output of the amplifier. A current source bridge type bass amplifier circuit characterized in that the time or the degree of conductivity is controlled. 2. The circuit that avoids the short mode is a delay circuit that delays all the outputs of the discrimination circuit by a certain period of time and outputs the output, and an AN with an affirmative input that ANDs the input signal and output signal of this delay circuit.
The current source bridge type servo amplifier circuit according to claim 1, which is constituted by a D gate and an AND gate with a negative input. 6 A DC motor is connected between the equilibrium points of four switching circuits bridge-connected to a DC voltage source, and two of the four switching circuits are connected via a circuit that avoids an all-short mode according to a control input signal. A current source bridge type servo amplifier circuit that selectively conducts and controls the conduction time or degree of conduction to control the direction and thickness of the current flowing to the DC motor. a current detection circuit that detects the current that is being detected; a comparison circuit that completely compares the output signal of this current detection circuit with the control input signal and outputs all signals of polarity and magnitude according to the magnitude relationship and difference; an amplifier capable of switching between inverting and non-inverting modes that inputs an output signal from a circuit and amplifies it in inverting or non-inverting; a discrimination circuit that determines whether the control input signal is positive or negative; and a direction designator that designates the direction of rotation of the DC motor. A circuit for inputting a signal is provided, and the mode of the amplifier is switched by the discrimination output or the direction designation signal of the discrimination circuit, and two switch circuits to be made conductive among the four switch circuits are determined, and the amplifier A current source bridge type servo amplifier circuit, characterized in that the conduction time or degree of conductivity of the switch circuit to be rendered conductive is controlled according to the output of the current source bridge type servo amplifier circuit. 4 The circuit to avoid short mode is a delay circuit that delays the output of the discrimination circuit for a certain period of time and outputs it, and an AN with an affirmative input that ANDs the input signal and output signal of this delay circuit.
4. The current source bridge type smartphone amplifier circuit according to claim 3, which is constituted by a D gate and an ANI gate having a negative input. 5 All DC motors are connected between the equilibrium points of four switching circuits bridge-connected to a DC voltage source, and two of the four switching circuits are connected in accordance with the control input signal through a circuit that avoids all short modes. In the current source bridge type servo amplifier circuit, the current source bridge type servo amplifier circuit is configured to selectively conduct the current and fully control the conduction time or degree of conduction to control the direction and thickness of the current flowing through the DC motor. A current detection circuit that detects the current that is flowing, a circuit that adds a constant bias voltage to the front control signal, and said 1! X! A comparison circuit that completely compares the control input signal to which a bias voltage is applied by the circuit with the output signal of the current detection circuit and outputs a signal of polarity and thickness according to the magnitude relationship and difference, and the output signal of this comparison circuit. an amplifier capable of switching between inverting and non-inverting modes for inverting or non-inverting amplification by inputting the signal; and a discrimination circuit for discriminating whether the control input signal to which the bias voltage is fully applied is positive or negative; 2 of the four switch circuits is turned on while switching the mode of the amplifier;
A current bridge type servo amplifier circuit, characterized in that the conduction time or degree of conduction of the switch circuit to be made conductive is fully controlled in accordance with the output of the amplifier. 6 The circuit to avoid short mode is a delay circuit that delays the output of the discrimination circuit for a certain period of time and outputs it, and an AN of the positive input that ANDs the input signal and output signal of this delay circuit.
6. The current source bridge type servo amplifier circuit according to claim 5, comprising a D gate and an AND gate with a negative input.