JPS62262689A - Power source circuit for dc motor - Google Patents

Abstract

PURPOSE:To set the variable range of a voltage applied to a motor without respect to an input DC power source voltage by selecting any of a step-down circuit and a step-up circuit. CONSTITUTION:A selector 6 outputs a selection signal of H level when a control signal voltage is higher than a reference voltage and a selection signal of L level when it is lower. When the selector 6 outputs the signal of H level, a gate circuit 7 passes a PWM signal, a gate circuit 8 sets a switching transistor T1 always to ON state, thereby constructing a chopper type step-up circuit. When the selector 6 outputs the signal of L level, the gate circuit 8 passes a PWM signal, the gate 7 sets a switching transistor T1 always to OFF state, thereby constructing a chopper type step-down circuit.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a DC motor power supply circuit that supplies current to motor windings to drive a DC motor, and particularly relates to a DC motor power supply circuit that supplies current to motor windings to drive a DC motor, and in particular, to a DC motor power supply circuit that controls a variable range of motor applied voltage. This invention relates to a DC motor power supply circuit that can be set regardless of voltage.

[Prior Art] FIG. 5 is a diagram showing a DC motor power supply circuit having a conventional chopper type step-down circuit configuration.

In the figure, an input DC power supply voltage V is input to an input power supply terminal 1. An input power supply terminal 1 is connected to the emitter of a switching transistor T1 made of a pnp transistor, and its collector is connected to a motor winding of a DC motor 2 via a coil L1 and an output terminal 5. A diode D is connected to the connection point between the switching transistor T1 and the coil L1.
1 cathode is connected and its anode is grounded. Coil L
One electrode of the capacitor C1 is connected to the connection point between the capacitor C1 and the output terminal 5, and the other electrode is grounded. Further, the connection point between the coil L1 and the capacitor C1 and the connection point between the output terminal 5 and the output terminal 5 are grounded via resistors R1 and R2. A control signal for controlling the rotation speed of the DC motor 2 is input to the control signal input terminal 3 . Control signal input terminal 3 is PWM (pulse width variable 2
N) switching transistor T1 via control circuit 4
The connection point between resistors R1 and R2 is PW
It is connected to the M control circuit 4.

The PWM control circuit 4 generates a PWM signal, which is a pulse signal with a predetermined pulse width, in response to a control signal, and controls on/off of the switching transistor T1. If the control signal voltage is high, the pulse width of the PWM signal becomes wide, and if the control signal voltage is low, the pulse width of the PWM signal becomes narrow. The emitter-collector voltage of the switching transistor T1 is v
When cε is increased, the collector voltage waveform of the switching transistor T1 becomes as shown in FIG. FIG. 6(A) shows a case where the control signal voltage is high, and FIG. 6(B) shows a case where the control signal voltage is low. switching transistor T
1 is smoothed by a smoothing circuit composed of a coil L1 and a capacitor C1, but if the control signal voltage is high, the output voltage of the output terminal 5, that is, the DC motor 2
The motor applied voltage applied to the winding becomes higher, and the motor rotation speed increases. Conversely, if the control signal voltage is low, the voltage applied to the motor becomes low and the motor rotational speed decreases. Then, by feeding back to the PWM control circuit 4 a divided voltage obtained by dividing this motor applied voltage by resistors R1 and R2, the pulse width of the PWM signal is corrected by 1117 ζ This corrects the rotation speed of the DC motor 2. ing. For reference, FIG. 7 shows the motor rotation speed-load torque characteristic of a direct current (DC) motor. This DC motor power supply circuit having a chopper type step-down circuit configuration has a feature of high power supply efficiency because the switching transistor T1 can be operated in the saturation region.

Further, a relationship of V>V2 holds between the input DC power supply voltage V and the output voltage V2.

FIG. 8 is a diagram showing a DC motor power supply circuit having a conventional chopper type step-up circuit configuration.

In the figure, the input power supply terminal: 11 has an input DC power supply voltage V,
is input. Input power terminal 1 is connected to n via coil L2.
It is connected to the collector of a switching transistor T2 consisting of a pn transistor, and its emitter is grounded. The connection point between the coil L2 and the switching transistor T2 is connected to the DC motor 2 via the diode D2° output terminal 5.
connected to the motor windings. One electrode of the capacitor C2 is connected to the connection point between the diode D2 and the output terminal 5,
The other electrode is grounded. Further, the connection point between the diode D2 and the capacitor C2 and the connection point between the output terminal 5 and the output terminal 5 are grounded via resistors R3 and R4. A control signal for controlling the rotation speed of the DC motor 2 is input to the control signal input terminal 3 . The control signal input terminal 3 is connected to the gate of the switching transistor T2 via the PWM control circuit 4, and is connected to the gate of the switching transistor T2.
The connection point between 3 and R4 is connected to a PWM control circuit 4.

This DC motor power supply circuit receives P from the PWM control circuit 4.
The switching transistor T2 is turned on and off by the WM signal.
The output voltage v2 of the output terminal 5, that is, the divided voltage obtained by dividing the motor applied voltage by the resistors R3 and R4, is set as P.
It is fed back to the WM control circuit 4, and similar to the DC motor power supply circuit with the chopper type step-down circuit configuration shown in FIG.
If the control signal voltage is high, the motor applied voltage becomes high and the motor rotation speed increases, and conversely, when the control signal voltage is low, the motor applied voltage becomes low and the motor rotation speed decreases. This DC motor power supply circuit differs from the DC motor power supply circuit shown in FIG. 5 in that it can obtain an input DC power supply voltage V and a higher motor applied voltage. That is, one end of the coil L2 is directly connected to the input power supply terminal 1, and the other end of the coil L2 is connected to the collector of the switching transistor T2. Therefore, by controlling the switching transistor T2 on and off using a PWM signal, the coil L2 The other end is repeatedly connected to the ground (GND) potential and disconnected from the ground potential. Therefore, when the other end of the coil 2 is disconnected from the ground potential, a back electromotive force is generated between both ends of the coil L2, and due to this back electromotive force, a voltage of V2 is generated between the input DC power supply voltage v1 and the output voltage v2. >V holds true.

[Problems to be Solved by the Invention] Since the conventional power supply circuit for a DC motor is configured as described above, the variable range of the voltage applied to the motor can be set to either a voltage lower than the input power supply voltage or a voltage higher than the input power supply voltage. There was a problem in that it could only be set.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a DC motor power supply circuit that can set the variable range of motor applied voltage regardless of the input DC power supply voltage.

[Means for Solving the Problems] A DC motor power supply circuit according to the present invention includes a step-down circuit of a DC motor power supply circuit having a chopper-type step-down circuit configuration, and a DC motor power supply circuit having a chopper-type step-up circuit configuration. The circuits are connected in cascade with a step-up circuit, and a selection circuit selects either the step-down circuit or the step-up circuit.

[Function] In this invention, when the level of the selection signal from the selection circuit is L level, the step-down circuit is selected and the voltage applied to the motor becomes lower than the input DC power supply voltage, and when the level of the selection signal is H level. , the step-up circuit is selected and the motor applied voltage becomes higher than the input DC power supply voltage.

[Example〕 Embodiments of the present invention will be described below with reference to the drawings.

In the description of this embodiment, the description of parts that overlap with the description of the conventional technology will be omitted as appropriate.

FIG. 1 is a diagram showing a DC motor power supply circuit according to an embodiment of the present invention. In the figure, an input DC power supply voltage V is input to an input power supply terminal 1.

The step-up circuit SU includes a coil L2, a switching transistor T2, a diode D2, and a capacitor C2, and the step-down circuit SD includes a switching transistor T1, a diode D1, a coil L1, and a capacitor C1. Input power supply terminal 1 is connected to coil L2 of step-up circuit SU. The connection point between the diode D2 and the capacitor C2 of the step-up circuit SU is connected to the emitter of the switching transistor T1 of the step-down circuit SD, and the connection point between the coil L1 and the capacitor D1 of the step-down circuit SD is connected to the output terminal 5. Ru. A control signal for controlling the rotation speed of the DC motor 2 is input to the control signal input terminal 3 . Control signal input terminal 3 is connected to one input side of gate circuit 7 and one input side of gate circuit 8 via PWM control circuit 4 . Further, the control signal input terminal 3 is connected to the other input side of the gate circuit 7 and the other input side of the gate circuit 8 via the selection circuit 6. Gate circuit 7 is connected to the gate of switching transistor T2, and gate circuit 8 is connected to the gate of switching transistor T1.

A connection point between the coil L1 and the capacitor C1 and a connection point between the output terminal 5 and the output terminal 5 are connected to the PWM control circuit 4 via a voltage dividing circuit 9.

The control signal from the control signal input terminal 3 is sent to the PWM control circuit 4.
and is applied to the selection circuit 6. PWM control circuit 4 generates a PWM signal in response to a control signal, and this PWM signal is applied to one input side of gate circuit 7 and one input side of gate circuit 8.

The selection circuit 6 includes a reference voltage generation circuit, compares the control voltage and the reference voltage, and outputs an "H" level selection signal when the control signal voltage is higher than the reference voltage, and conversely outputs an "H" level selection signal when the control signal voltage is lower than the reference voltage. Outputs an L'' level selection signal. This selection signal is applied to the other input side of gate circuit 7 and the other input side of gate circuit 8, and is also applied to voltage divider circuit 9. When the selection signal of "H° level" is output from the selection circuit 6, the gate circuit 7 passes the PWM signal, and the PWM signal that has passed through the gate circuit 7 controls the switching transistor T2 on/off. The circuit 8 cuts off the PWM signal and generates a signal that keeps the switching transistor T1 always on. Therefore, in this case, the switching transistor T1 is always on, and the diode D1, coil L1, and capacitor of the step-down circuit SD C1 is
It does not operate as a switching power supply circuit, but simply plays the role of a smoothing filter, and the entire circuit shown in FIG. A higher power supply voltage V and a higher motor applied voltage V2 can be obtained. When the selection signal at "L" level is output from the selection circuit 6, the gate circuit 8 passes the PWM signal, and the PWM signal that has passed through the gate circuit 8 controls the switching transistor T1 to be turned on and off. On the other hand, the gate circuit 7 cuts off the PWM signal and generates a signal that keeps the switching transistor T2 in an off state at all times. Therefore, in this case, the switching transistor T2 is always in an off state, and the coil L1, diode D2, and capacitor C2 of the step-up circuit SA do not operate as a switching power supply circuit, but instead serve as a power supply filter 111. Therefore, the entire circuit in FIG. 1 operates as a DC motor power supply circuit with a step-down circuit configuration, and the motor applied voltage v lower than the input DC power supply voltage v1 is applied to the output terminal 5.
2 is obtained.

The voltage dividing circuit 9 is constructed as shown in FIG. In the figure, R5, R6 and R7 are resistors, 10 is a switch, and 12 is an output voltage V2 of output terminal 5 between resistor R5 and resistor R.
A terminal 11 outputs a feedback voltage divided by resistor R5 and resistors R6 and R7. A terminal 11 inputs a selection signal from the selection circuit 6 that turns on and off the switch 10.

The “H” level selection signal from the selection circuit 6 is input to the input terminal 11.
switch 10 is turned on and output terminal 1 is input to
The feedback voltage No. 2 is a voltage obtained by dividing the output voltage V2 by the resistor R5 and the resistors R6 and R7. “L” from the selection circuit 6
"When the level selection signal is input to the input terminal 11, the switch 10 is turned off, and the feedback voltage at the output terminal 12 becomes a voltage obtained by dividing the output voltage v2 by the resistor R5 and the resistor R6.

When setting the feedback voltage, it is advantageous in terms of power supply circuit design to secure the dynamic range of the PWM control circuit 4 as effectively as possible. Even when operating as a DC motor power supply circuit with a step-up circuit configuration, it is generally desirable to consider so that the pulse width variable range of the PWM signal operates 100% effectively. Obviously, when operating as a power supply circuit with a step-down circuit configuration, the variable range of the output voltage v2 is the input DC power supply voltage V or less, and when operating as a power supply circuit with a step-up circuit configuration, the variable range of the output voltage v2 is Since the range is a voltage range equal to or higher than the input DC power supply voltage V2, it is desirable in design that the voltage divider circuit 9 be configured to be able to set at least two or more divided voltage values.

In addition, in the explanation of the prior art, the relationship between the output voltage v2 and the input DC power supply voltage ■1 is ■ in the DC motor power supply circuit with a chopper type step-down circuit configuration, 〉■2, and 〉■2 in the DC motor power supply circuit with the chopper type step-up circuit configuration. In the motor power supply circuit, it is assumed that V, <V2, but when considered in detail in Fig. 1, when operating as a power supply circuit with a step-down circuit configuration, the voltage due to the DC resistance of the coil L2,
Since a voltage drop occurs in the forward voltage vF of the diode D2 and the emitter-collector voltages 2 and ε of the switching transistor T1, the output voltage v2 actually becomes as shown in the following equation.

V2<V, -1 (voltage due to DC resistance of coil L2)
+ V F + V CE When operating as a power supply circuit with a step-up circuit configuration, the output voltage v2 is similarly expressed by the following equation.

V2>v, -+ (voltage due to DC resistance of coil L1)
+VF +Vcε) Therefore, if the DC resistance of coils L1 and L2 is appropriately selected from the above two equations, the input DC power supply voltage ■,
It is possible to set the variable range of the output voltage, that is, the voltage applied to the motor, without being restricted by this.

FIG. 3 is a diagram showing a DC motor power supply circuit according to another embodiment of the present invention. This DC motor power supply circuit is
In Figure 1, the arrangement of the step-down circuit SD and step-up circuit SU is swapped, and the operation of this DC motor power supply circuit can be easily understood from the explanation of the DC motor power supply circuit shown in Figure 1 above. be understood.

FIG. 4 is a diagram showing a DC motor power supply circuit according to still another embodiment of the present invention. The rising speed of the motor rotational speed largely depends on the starting torque generated by the motor. As is clear from the motor rotation speed-load torque characteristic of the DC motor shown in FIG. 7, the higher the voltage applied to the motor, the greater the starting torque. Therefore, if an attempt is made to speed up the rise time when the motor is started, an applied voltage that is several times higher than the voltage applied to the motor during normal rotation is required when the motor is started. Therefore, as shown in FIG.
An input terminal 14 for a start command signal is provided, and by this start command signal! If the stable multivibrator 13 is configured to send an "H" level signal to the other input side of the gate circuit 7 and the other input side of the gate circuit 8 for a certain period of time, the time required to start the DC motor 2 will be reduced. , 4th
The entire circuit in the figure operates as a DC motor power supply circuit with a chopper type step-up circuit configuration, so the DC motor 2
A high-speed rise can be ensured.

A battery is often used as the input DC power source. Assuming that the power consumption of the entire device including the DC motor and DC motor power supply circuit is constant, the larger the current capacity of the battery, the better the volumetric efficiency. It is generally known that the smaller the volume of the body, the lighter the weight. In view of reducing the size and weight of the entire device, it is effective to lower the supply voltage of the battery power source, and the present invention is particularly effective in this respect.

Note that in the above embodiment, the switching transistor TI
, T2 is controlled on and off by the PWM control circuit 4, but the switching transistor T2 is
The on/off control of I and T2 may be performed by frequency control, and in this case as well, the same effects as in the above embodiment can be achieved.

[Effects of the Invention] As described above, according to the present invention, a step-down circuit of a DC motor power supply circuit having a chopper-type step-down circuit configuration and a step-up circuit of a DC motor power supply circuit having a chopper-type step-up circuit configuration. are connected in cascade, and the selection circuit selects either the step-down circuit or the step-up circuit, so the switching drive allows the variable range of the motor applied voltage to be set regardless of the input DC power supply voltage. It is possible to obtain a DC motor power supply circuit using this method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a DC motor power supply circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the voltage dividing circuit shown in FIG. 1. FIG. 3 is a diagram showing a DC motor power supply circuit according to another embodiment of the present invention. FIG. 4 is a diagram showing a DC motor power supply circuit according to still another embodiment of the present invention. FIG. 5 is a diagram showing a DC motor power supply circuit having a conventional chopper type step-down circuit configuration. 6A and 6B are diagrams showing collector voltage waveforms of switching transistors in the DC motor power supply circuit having the chopper type step-down circuit configuration shown in FIG. 5. FIGS. FIG. 7 is a diagram showing motor rotation speed-load torque characteristics of a DC motor. FIG. 8 is a diagram showing a DC motor power supply circuit having a conventional chopper type step-up circuit configuration. In the figure, 1 is an input power supply terminal, 2 is a DC motor, 3 is a control signal input terminal, 4 is a PWM control circuit, 5 is an output terminal, 6 is a selection circuit, 7 and 8 are gate circuits, 9 is a voltage dividing circuit,
10 is a switch, 11 is an input terminal, 12 is an output terminal, 1
3 is monostable multi-bi break, 14 is input terminal, TI
, T2 are switching transistors, DI and D2 are diodes, Ll and L2 are coils, CI and C2 are capacitors, SU is a step-up circuit, SD is a step-down circuit, and R5, R6, and R7 are resistors. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (4)

[Claims] (1) A DC motor power supply circuit of a switching drive type, which includes a DC power supply, a pnp transistor whose emitter is an input terminal, and a first coil whose one end is connected to the collector of the pnp transistor. a first diode whose cathode is connected to a connection point between the pnp transistor and the first coil and whose anode is grounded; one electrode of which is connected to the other end of the first coil and the other electrode of which is connected; a first capacitor that is grounded; a first circuit that has an output terminal at a connection point between the first coil and the first capacitor; and a second coil that has one end thereof as an input terminal. and a second diode whose anode is connected to the other end of the second coil, whose collector is connected to the connection point between the second coil and the second diode and whose emitter is grounded. np
n transistor, and a second capacitor, one electrode of which is connected to the cathode of the second diode, and the other electrode of which is grounded, and the connection point between the second diode and the second capacitor is a second circuit serving as an output terminal, the DC power supply being connected to the input terminal of the first circuit, and the output terminal of the first circuit being connected to the input terminal of the second circuit. and the output end of the second circuit is connected to a winding of a DC motor, or the DC power source is connected to the input end of the second circuit, and the output end of the second circuit is connected to a winding of a DC motor. The output terminal of the first circuit is connected to the input terminal of the first circuit, and the output terminal of the first circuit is connected to the winding of the DC motor, and generates a predetermined pulse width in response to a control signal that controls the rotation speed of the DC motor. a pulse signal generation circuit that generates a pulse signal; and a voltage divider that divides the voltage applied to the winding of the DC motor in order to correct the rotational speed of the DC motor and feeds it back to the pulse signal generation circuit. a selection circuit that generates a binary level selection signal for selecting one of the first circuit and the second circuit; A signal generation circuit output is connected to the gate of the pnp transistor and generates a signal to turn off the npn transistor, or an output of the pulse signal generation circuit is connected to the gate of the npn transistor and the pnp transistor is turned on. A power supply circuit for a DC motor, comprising a gate circuit that generates a signal to (2) The DC motor power supply circuit according to claim 1, wherein the voltage dividing circuit is configured to set the first or second voltage dividing value in response to the output of the selection circuit. (3) The DC motor power supply circuit according to claim 1 or 2, wherein the selection circuit comprises a comparison circuit to which the control signal is input and which compares the voltage of the control signal with a reference voltage. (4) The DC motor power supply circuit according to claim 1 or 2, wherein the selection circuit comprises a multivibrator into which a starting command signal for the DC motor is input.