JPS627400A - Winding current controller - Google Patents

Abstract

PURPOSE:To reduce power loss by connecting a switching element through a diode in parallel with a winding. CONSTITUTION:A winding L is connected at one end with a power terminal VCC, and grounded at the other end through a diode D3, the first transistor Q1 and a current detecting resistor RS connected in a Darlington configuration. The second transistor Q1 of Darlington configuration is connected through the first diode D1 in parallel with the winding L, and an energy discharging circuit having the second diode D2 and a Zener diode ZD is connected in parallel. The second transistor Q2 is turned ON during the OFF period of the first transistor Q1, a current based on the storage energy of the winding L continuously flows to perform a smoothing action. Since the first and second transistors are not connected in series with the winding, a current from the power source is not supplied simultaneously to the transistors. Thus, power loss is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit for controlling the current in the windings of a Brangin-lenoid, DC motor, or the like.

[Conventional technology]

BACKGROUND OF THE INVENTION In order to control the current flowing through a Branjan Lenoid used in a printer's print head or the like, or a winding of a DC motor, it is already practiced to supply DC voltage intermittently. 5, 6 and 7 show conventional winding current control circuits. All of these circuits include a first transistor Q, a winding, a second transistor Q, and a current detection resistor between one end of a DC power supply indicated by VCC and the other end (ground) of the power supply. It has a series circuit consisting of R8.

The second transistor Q is turned on in accordance with the drive period of the winding, and the first transistor Q is controlled intermittently to control the current flowing through the winding.

This makes it possible to supply a constant current to the one-turn ML. By the way, when the first transistor QIyr is controlled intermittently, the current flatness deteriorates, so it is necessary to solve this problem. Furthermore, during off control, it is necessary to quickly bring the current in one winding to zero. In the circuit shown in Figure 5, 81 diodes DA are connected between the upper end of one winding and the ground, and a second diode DB is connected between the lower end of one winding and the voltage terminal VCC. has been done. In the circuit of Figure 6, the second diode DB? A Zener diode ZD is connected to the winding ML through a parallel liquid Wr. In the circuit of FIG. 7, a Zener diode ZD is connected between the lower end of the winding and the ground.

[Problem that the invention seeks to solve]

In the circuits shown in FIGS. 5 to 7, both the first and second transistors Q, , Q are connected in series with the winding between the DC power supply terminal VCC and the ground, and the first winding L
When driving Y, the first and second transistors Q, ,Q,
Current flows through both. Therefore, the power loss in the first and second transistors Q, ,Q becomes large. Such a problem also occurs when a FET or the like other than a bipolar transistor is used as a switching element.

[Tanu's means of solving problems]

In order to solve the above-mentioned problems, a winding current control circuit according to the present invention includes a winding whose one end is connected to one DC power supply terminal, and a winding connected to the other end of the winding and the other DC power supply terminal. a first switching element connected between the terminal and the first switching element, which is controlled intermittently to control the current flowing through the winding;
are connected in parallel to the winding through diodes in order to reduce ripples in the current flowing through the winding when the switching elements are controlled intermittently, and at least the first switching element is turned off during the driving period of the winding. It is characterized in that it also has a second switching element that is controlled to be turned on during the period.

[For production]

In the circuit as described above, current is supplied from the power supply to the winding during the on period of the first switching element.

Since the second switching element is on at least during the OFF period of the first switching element during the driving period of the winding, the connection between the winding, the first diode, and the second switching element occurs during the driving period of the first winding. A closed circuit consisting of
A current based on the stored energy (back electromotive force) of the winding continues to flow through this, producing a flat wave effect. Since both the first and second switching elements are not connected in series with the winding, the current supplied from the power supply does not flow through both switching elements simultaneously. Therefore, power loss is reduced.

〔Example〕

Next, an embodiment of the present invention will be described.

(Example of Fig. 1) Fig. 1 shows the control circuit Y of the Branjean Lenoid for printing in a printer.One end of the electromagnetic drive winding is connected to the DC power supply terminal VCC, and the other end is connected to the backflow blocking diode. D.
The winding is connected to the ground (the other end of the power supply) by valving the first transistor Q1 and the current detection resistor R6 of the Darlington configuration. A second transistor Q is connected in parallel, and an energy release circuit consisting of a second diode D and a Zener diode ZD is connected in parallel.In operation, the first diode D1 and M2 The resistance value of the circuit with the transistor Q! is set lower than the resistance value of the circuit with the second diode D and the Zener diode ZD.

The first transistor Q1 is provided as a first switching element which is controlled intermittently as shown by V in FIG. ℃ is provided as a second switching element that is controlled to be turned on during the off period of the first transistor Q□.

The control circuit for the first and second transistors Q, ,Q, is
an operational amplifier 117 whose output terminal is connected to the base of the first transistor Q1;
a triangular wave generator (2) connected to the non-inverting input terminal of the
A resistor (3) connected between the inverting input terminal of the operational amplifier Masuda and the upper end of the current detection resistor Rs, a Hirayui capacitor (4) connected between the inverting input terminal and the ground, and the A third transistor Q1 is connected via a resistor (5) between the base of the transistor Q2 and the output terminal of the operational amplifier, and a resistor (6J is connected to the base of the third transistor Q1). Connected drive signal supply circuit (
7). In addition.

The operational amplifier ti+ includes an open collector transistor in the output stage, and when the non-inverting input is higher than the inverting input, the transistor in the power stage is turned off and the output terminal is not grounded, and conversely, when it is low, it is turned on. The output terminal is configured to be grounded.

(Operation) Next, the operation of the circuit shown in FIG. 1 will be explained with reference to the waveform diagram shown in FIG. A high-level drive signal indicated by vI is generated during periods 1. to 1. in the figure.

This causes the pace current of the first transistor Q1 to flow through the third transistor Q1, turning it on. As a result, current begins to flow through the first winding LK as shown by I in FIG. Since the winding has an inductance, the current II flowing through it gradually increases, and the current detection resistor R8
The voltage V at the upper end and the voltage V at the inverting input terminal of the operational amplifier (1?), which operates as a comparator, gradually increase as shown in FIG. Since the triangular wave voltage V shown by the dotted line in Fig. 2 is applied at a constant cycle, the detected voltage V and the triangular wave voltage v1 are compared, and at time t3, the τ triangular wave voltage V becomes the detected voltage V,
, the output of the operational amplifier 11J changes from high level to low level. For this reason, the first transistor Q.

is controlled off. However, since the capacitor (4) is provided, the voltage V at the inverting input terminal of the operational amplifier tll does not become zero, but decreases with a slope that is gentler than the slope of the triangular wave voltage v1. Therefore, the output voltage V of the operational amplifier (17) is not immediately converted to a high level and is kept at a low level. Even if transistor Q, is on,
The second pnp transistor Q, whose flipper is connected to the power supply terminal VCC, is kept in a reverse bias state and is controlled to be turned off. However, during the period from t0 to t5 when the output voltage v4 of the operational amplifier (1) is at a low level, it is biased to the on state and the current I, as shown in FIG.
flows. This current I is based on the release of energy stored in one winding, that is, a back electromotive force, and flows in a closed circuit consisting of one winding, the first diode D1, and the second transistor Q. The current 11 of this single winding continues to flow as shown in FIG. 2 even during the off period of the first transistor Q1. Therefore, even though the voltage supplied to one winding is interrupted by the first switching transistor Q1, the smoothness of the current I is improved.

When the triangular wave voltage V, becomes higher than the detection voltage V, at time t8, the output voltage V, of the operational amplifier (1) becomes high level again, and the first transistor Qt is turned on.

If the first transistor Q is controlled on and off by such a comparison operation, the average value of the current flowing through the 1Ml transistor Q, that is, the winding current 1, becomes approximately constant. Synchronizing with the end of the drive period of the winding, if the drive signal v1 is set to a low level at point 14 in Figure 2, the third transistor Q
1 is turned off and the first and second transistors Q, ,Q
It becomes impossible to supply the base current of □, and these are turned off. At this time, even if a period occurs in which the triangular wave voltage V, is higher than the detection voltage V, on the input side of the operational amplifier (1), since there is no drive signal, only the operational amplifier (1) can operate the first transistor. It is not possible to control Q+v on. Therefore, after t in FIG. 2, the first and second transistors Q, , Q are kept off and the energy stored in one winding is transferred to the second diode D and the Zener diode. The energy is consumed in the energy release circuit consisting of ZD, and the electric current worker 1 quickly goes to zero.

(Embodiment of FIG. 3) Next, a current control circuit for the windings of a pulse motor shown in FIG. 1M3 will be explained. However, parts common to those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

In Figure 3, instead of supplying a triangular wave voltage to the non-inverting input terminal of the operational amplifier B tlJ, a trigger pulse generation circuit uses a divided voltage obtained from a voltage dividing circuit using a resistor αQαD connected between the power supply terminal +V and the ground. Trigger pulse obtained from (8) plus t is supplied.

Also, do not apply a changing voltage to the 1 inverting input terminal lC1
A resistor (9) is connected between the flipter and the inverting input terminal of the first transistor Q.

In this device, a trigger pulse generation circuit (8) generates a constant period "e) +7 pulses as shown in FIG. The output of the operational amplifier (1) is supplied to the non-inverting input terminal of the drive signal supply circuit (1).As a result, during the trigger pulse generation period, the output of the operational amplifier (1) becomes high level regardless of the level of the inverting input terminal. ) as in the case of Fig. 1, the first transistor Q is turned on in synchronization with the trigger pulse.In other words, during the trigger pulse generation period, the output terminal of the operational amplifier (1) is grounded. Since the state has been released, the base currents of the first and third transistors Q, , Q are supplied by the drive signal, and the first transistor Qj is turned on.
When the transistor Q, turns on at time t1 in FIG. 4, its collector voltage V, decreases, and eventually the voltage V at the inverting input terminal of the operational amplifier (1) also decreases as shown in FIG. . As a result, even if the trigger pulse disappears, the high level output state of the operational amplifier (1) is maintained, and the first transistor Q is kept turned on. However, the first transistor Q! As the current gradually increases, the voltage vl at the upper end of the current detection resistor RS also gradually increases, and eventually the voltage at the inverting input terminal 1 is higher than the voltage v3 at the non-inverting input terminal. The output terminal of (1) is switched to low level. This turns off the first transistor Q+. During the off period of the first transistor Q, the transistor Q of M2 is turned on and current continues to flow in the winding. After that.

When the trigger pulse is applied again, the output of the operational amplifier (1) is inverted and the first transistor Q is turned on again. When the supply of the drive signal from the drive signal supply circuit (force) is stopped, all of the first to third transistors Q1 to Q are turned off.

(Modified example) The invention is not limited to the embodiments described above.

It is deformable. For example, Zener diode Z
Instead of D, a varistor, a resistor, etc. may be connected. 1. Instead of using an open-left operational amplifier (11), a transistor is connected between the base of the first transistor Q and the ground, and the first transistor Q is controlled.

x On/off control may be performed. Further, the first and second transistors Qj, Q are connected by the third transistor Qa.
- without controlling both of them, an independent control circuit is provided, and the entire period (t, ~1.
), the second transistor Q is always supplied with an ON control signal.

〔Effect of the invention〕

As is clear from the above, according to the present invention, the current supplied from the power supply passes through the first switching transistor,
The second transistor does not pass.

Therefore, power loss χ can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a current control circuit according to an embodiment of the present invention. FIG. 2 is a waveform diagram illustrating the states of each part of the circuit of FIG. 1. FIG. 3 is a circuit diagram showing a current control circuit according to another embodiment of the present invention. FIG. 4 is a waveform diagram illustrating the state of each part in FIG. 3. FIGS. 5, 6, and 7 are circuit diagrams showing eight conventional current control circuits. Q...first transistor, Ql...second transistor, L...winding, D...diode, mountain...operational amplifier, (7)...drive signal supply circuit. Agent Norihisa Takano Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] (1) A winding whose one end is connected to one DC power terminal, and a winding connected between the other end of the winding and the other DC power terminal, and which is connected intermittently to control the current flowing through the winding. a first switching element to be controlled; a first switching element connected in parallel to the winding through a diode to reduce ripples in the current flowing through the winding when the first switching element is controlled intermittently; At least the first
A winding current control circuit comprising: a second switching element that is turned on during an off period of the switching element;