JPH11299292A - Motor driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving circuit of a motor which can limit charging current with small number of components and which requires only a small space and can increase the motor efficiency by allowing charging current of an electrolytic capacitor to flow through an upper or a lower arm transistor which constitutes an H-bridge and a resistor for detecting a motor winding current and thereby building up a current limiting circuit with these components. SOLUTION: When a power switch 12 is turned on, for examle, an upper transistor 2 comes to an ON state and charging current id is caused to flow through the transistor 2 and a diode 9. The current id passes through a resistor 14 for detecting a current, where the current is converted into voltage, and then the voltage is compared with the reference voltage by means of a comparator 15. In the case that current of the set value or above is caused to flow, an output signal from a logic circuit 7 is cut off to stop the flow of charging current into an electrolytic capacitor 13. When the current in the resistor 14 for detecting a current decreases, the electrolytic capacitor 13 is supplied with charging current again. When charging comes near to completion, a motor winding 5 is also starts to be excited. The sum of the charging current id and the exciting current for the motor winding 5 is kept at the set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a motor driving circuit,
In particular, the present invention relates to a drive circuit such as a DC brushless motor that suppresses a charging current flowing to charge a surge absorbing electrolytic capacitor in a circuit when power is turned on.

[0002]

2. Description of the Related Art Generally, when a DC brushless motor is bipolar energized, a commutation operation for switching the energizing direction is required. FIG. 4 shows this commutation state. Reference numerals 1 and 2 denote an upper-arm PNP transistor constituting an H bridge, 3
And 4 are also lower arm NPN transistors and 5 is H
A single-phase winding of a motor connected to the output side of the bridge, 6 is a DC power supply also connected to the input side, and 7 is an energizing logic circuit for turning on and off the above-mentioned transistors 1-4. , And a pair of 2 and 3 are alternately turned on and off by a signal from the energization logic, and a commutation in which the energization direction to the motor winding 5 is alternately reversed as ia and ie is generated. I have.

In this case, electric energy E is accumulated in the single-phase winding 5 of the motor that has been energized in a certain direction. If the energizing current is i and the winding inductance is L, E = Li ²
/ 2. When the energization is stopped, a surge voltage Vs is generated at the winding terminal depending on the degree of attenuation of the current, and this surge voltage is expressed as Vs = Ldi / dt. In FIG. 4, there is no energy E release path, and in the case of an instantaneous stop, d
i / dt becomes infinite, and a very large surge voltage exceeding the withstand voltage of the transistor is applied to the transistor and destroys it.

Therefore, in order to protect the transistors from this surge voltage and to effectively use the energy stored in the windings, each transistor 1 shown in FIG.
4 are connected in parallel with the power supply 6, and the surge absorbing electrolytic capacitor 13 is connected in parallel with the power supply 6 through the switch 12, so that the transistors 1 and 4 are turned on.
In the state, the current ia flows, and at the moment of commutation when the state shifts to the OFF state, the energy E stored in the motor winding 5 flows through the diodes 9 and 10 as the current ib, the capacitance of the electrolytic capacitor 13 is C, and the electrolytic capacitor 13 is C. Is V, the voltage applied to the electrolytic capacitor 13 is E = CV ² /
2 will be accumulated. The level of the surge voltage Vs generated in this state is determined by the capacity of the electrolytic capacitor 13, and the larger the capacity, the longer the charging time and the smaller the voltage rise due to the surge voltage. Therefore, the capacity may be set so as not to exceed the withstand voltage of the transistor. . Further, at the start of the energization in the reverse direction, this energy is returned to the motor winding 5 as a current via the transistors 2 and 3 as a current, and the current supplied from the power source 6 is reduced, thereby increasing the efficiency. In FIG. 5, reference numeral 14 denotes a current detection resistor for detecting a current value supplied to the motor winding 5, and 15 denotes a comparator for comparing a detected voltage with a reference voltage corresponding to a set maximum current value. By controlling the output of the energizing logic circuit 7 with the output of the above, the maximum current value generated when the motor is started or locked is limited. The above is the general conventional method of surge voltage absorption.

However, in the above-described conventional driving circuit, when the power is turned on by the switch 12, a large charging current flows through the electrolytic capacitor 13 in accordance with the capacity and impedance of the power supply. FIG. 6 shows an example of a charging current waveform at a power supply voltage of 24 V DC and an electrolytic capacitor capacity of 100 μF.
A large current of 5 A flows for 100 μs. This large current has a significant effect on the life of switches, relays and semiconductors for opening and closing the power supply. Therefore, in order to limit the peak value of the charging current, as shown in FIG.
8 or a current limiting resistor 17 is inserted in series with the power supply 6 as shown in FIG. 8, and after the charging of the electrolytic capacitor 13 is completed, a transistor 18 connected in parallel with the resistor 17 is connected. There is a way to turn it on.

[0006]

However, in the conventional driving circuit configured as described above, there are many problems that the efficiency is reduced, the shape is increased, and the cost of parts is increased due to the voltage drop of the power supply line. Has occurred.

[0007] It is an object of the present invention to keep in mind the above-mentioned conventional problems,
An object of the present invention is to provide a drive circuit with good motor efficiency, space saving and low cost by limiting the charging current of the electrolytic capacitor with a much smaller number of parts than in the past.

[0008]

A motor driving circuit according to the present invention comprises a current detecting resistor for detecting a current flowing in a motor winding when the motor winding is bipolar-energized by four transistors having an H-bridge configuration. And a capacitor for absorbing a surge voltage during commutation, wherein the maximum current flowing through the circuit is suppressed, and the motor winding connection terminals of the two upper arm PNP transistors constituting the H-bridge are provided. And the anodes of the first and second diodes are connected to each other. The cathode side of each diode is connected to one terminal of the capacitor and the anode side of the third diode. The cathode side of the third diode is connected to DC.
The other terminal of the capacitor is connected to the emitter of the two lower arm NPN transistors and one end of the current detection resistor. The other end of the current detection resistor is connected to DC.
The power supply is connected to the negative side.

The motor driving circuit according to the present invention comprises a current detecting resistor for detecting a current flowing through the motor winding when the motor winding is bipolar-energized by four transistors having an H-bridge configuration, A motor drive circuit comprising a capacitor for absorbing a surge voltage at the time of controlling the maximum current flowing through the circuit, wherein the motor winding connection terminals of the two lower arm NPN transistors constituting the H-bridge are connected to the first and second terminals. The cathodes of the second diodes are connected to each other, the anode side of each diode is connected to one terminal of the capacitor and the cathode side of the third diode, the emitters of two lower arm NPN transistors and the current detection resistor are connected. And the other end of the current detection resistor and the anode side of the third diode are connected to the DC power supply negative side. The other terminal of the capacitors, characterized in that connected to the DC power source + side.

Further, the present invention is characterized in that a charging resistor is connected in parallel with the third diode.

In the present invention, the transistors constituting the H-bridge are MOSFETs, IGBTs or the like.
Is used.

The motor is a three-phase DC brushless motor or a stepping motor, and is characterized in that it has a three-phase bridge configuration in which three transistors for energizing the motor winding are arranged on the upper and lower arms, respectively.

[0013]

In the above configuration, a current limiting circuit is configured by passing the charging current of the electrolytic capacitor through the upper arm transistor or the lower arm transistor constituting the H-bridge and the resistor for detecting the motor winding current. In addition, the charging current of the electrolytic capacitor can be suppressed to the same value as the set value of the maximum current of the motor winding.

[0014]

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

FIG. 1 shows an example in which the present invention is applied to a bipolar energizing type driving circuit of a single-phase DC brushless motor.

In the present invention, the cathodes of the first and second diodes 8, 9 inserted in parallel with the upper arm PNP transistors 1, 2 are connected to the positive electrode of the electrolytic capacitor 13 and the anode of the third diode 19. And the negative electrode side of the electrolytic capacitor 13 is connected to the lower arm NPN transistors 3 and 4.
Connected to one end of the current detection resistor 14,
The other end of the current detection resistor 14 is connected to the negative electrode side of the DC power supply 6, and the cathode side of the third diode 19 is connected to the DC power supply + side.

Since the motor drive circuit of the present invention has the above-described structure, when the power switch 12 is turned on, one of the upper arm transistors 1 and 2 and the transistor 2 in FIG. 2. The charging current id flows through the diode 9, and the current passes through the current detecting resistor 14. The current is converted into a voltage by this resistor, and is compared with the reference voltage by the comparator 15. When the current flows, the output signal of the logic circuit 7 is cut off, the charging current to the electrolytic capacitor 13 is stopped, and when the current flowing through the current detection resistor 14 decreases, the current flows again. Therefore, by performing this operation at a high speed, it becomes possible to charge the electrolytic capacitor 13 with the set current value.

When the charging is almost completed, the motor winding 5
Also, the energization is started, and the sum of the charging current id and the energizing current of the motor winding 5 is suppressed to the set value. The energy E stored in the motor winding 5 at the time of commutation is charged as a current to the electrolytic capacitor 13 via the first or second diode 8 or 9, and when the current flows in the reverse direction, the third diode It is returned to the motor winding 5 via 19.

FIG. 2 shows another embodiment of the present invention in which a charging resistor 20 is connected in parallel to the third diode 19, and a delay between the time when the power switch is turned on and the time when the output signal of the energizing logic circuit is output. During the time, the charging current flows to the electrolytic capacitor 13 through the charging resistor 20 to shorten the charging time, and other operations are the same as those in the case of FIG.

FIG. 3 shows still another embodiment of the present invention in which the charging circuit of the electrolytic capacitor 13 is performed by the lower arm transistor 3 or 4. The basic operation is the same as that of FIG.

FIG. 9 shows an embodiment in which the present invention is applied to a three-phase DC brushless bipolar energizing drive circuit, in which three upper arm PNP transistors 1, 2, 31 and a lower arm NPN are provided.
A three-phase bridge circuit is constituted by three transistors 3, 4, and 32. When the power is turned on, the lower arm NPN transistor 3,
Either 4 or 32 is turned on, the same operation as the above-described H-bridge configuration circuit is performed, and the charging current of the electrolytic capacitor 13 can be limited to the set current value. Reference numeral 33 denotes a reflux diode connected in parallel with the transistor 31, and reference numerals 35 to 37 denote three-phase motor windings.

As described above, single-phase and three-phase DC to which the present invention is applied
The operation of the brushless motor has been described. However, the present invention can be applied to a bipolar energizing drive circuit of a multi-phase DC brushless motor or a stepping motor, and has the same effect. Also,
Although the transistor constituting the bridge is a bipolar transistor in the description, a similar configuration is possible by using a MOSFET or an IGBT.

[0023]

As described above, the motor driving circuit according to the present invention has the following excellent effects.

(1) Basically, a diode 1 is added to a conventional circuit.
This can be realized by adding an additional number.

(2) Cost reduction and space saving can be realized.

(3) Efficiency is high because there are no components with power loss in the power supply line.

(4) The time from the start of charging the capacitor to the start of energization of the motor winding can be minimized.

(5) Applicable to most bipolar motor drive circuits.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a motor drive circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the motor drive circuit of the present invention.

FIG. 3 is a circuit diagram showing still another embodiment of the motor drive circuit of the present invention.

FIG. 4 is a circuit diagram of a conventional bipolar energization without a surge voltage absorbing function.

FIG. 5 is a circuit diagram of a conventional bipolar energization with a surge voltage absorbing function.

FIG. 6 shows a charging current waveform when the power of the surge absorbing capacitor is turned on.

FIG. 7 is a conventional charge current value limiting circuit diagram.

FIG. 8 is a conventional charging current value limiting circuit diagram.

FIG. 9 is a circuit diagram showing an embodiment in which the present invention is applied to a drive circuit of a three-phase DC brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper-arm PNP transistor 2 Upper-arm PNP transistor 3 Lower-arm NPN transistor 4 Lower-arm NPN transistor 5 Single-phase winding of motor 6 DC power supply 7 Energizing logic circuit 8 Reflux diode 9 Reflux diode 10 Reflux diode 11 Reflux diode 12 Power supply switch 13 Surge absorbing electrolytic capacitor 14 Current detection resistor 15 Comparator 16 Cho coil 17 Current limiting resistor 18 Transistor 19 Diode 20 Charging resistor 31 Upper arm PNP transistor 32 Lower arm NPN transistor 33 Reflux diode 34 Reflux Diode 35 three-phase motor winding 36 three-phase motor winding 37 three-phase motor winding

Claims (8)

[Claims] 1. A current detecting resistor for detecting a current flowing in a motor winding when a motor winding is bipolar-energized by four transistors having an H-bridge configuration, and a capacitor for absorbing a surge voltage during commutation. In a motor drive circuit having a maximum current flowing through the circuit,
The motor winding connection terminals of the two upper arm PNP transistors constituting the H bridge are connected to the anodes of the first and second diodes, respectively, and the cathode side of each diode, one terminal of the capacitor and the third terminal The anode side of this diode is connected, the cathode side of this third diode is connected to the DC power supply + side, and the other terminal of the capacitor, the emitters of the two lower arm NPN transistors, and one end of the current detection resistor are connected. A motor drive circuit, wherein the other end of the current detection resistor is connected to the DC power supply (−) side. 2. A current detection resistor for detecting a current flowing through a motor winding when the motor winding is bipolar-energized by four transistors having an H-bridge configuration, and a capacitor for absorbing a surge voltage during commutation. In a motor drive circuit having a maximum current flowing through the circuit,
The motor winding connection terminals of the two lower arm NPN transistors constituting the H bridge are connected to the cathodes of the first and second diodes, respectively, and the anode side of each diode, one terminal of the capacitor and the third terminal And the emitters of two lower arm NPN transistors are connected to one end of the current detection resistor. The other end of the current detection resistor and the anode of the third diode are connected to the DC power supply side. And the other terminal of the capacitor is connected to a DC power supply (+) side. 3. The motor driving circuit according to claim 1, wherein a charging resistor is connected in parallel with said third diode. 4. The motor driving circuit according to claim 3, wherein MOSFETs and IGBTs are used as transistors constituting said H-bridge. 5. The motor driving circuit according to claim 1, wherein the motor is a DC brushless motor. 6. The motor driving circuit according to claim 1, wherein the motor is a stepping motor. 7. The motor according to claim 1, wherein the motor is a three-phase DC brushless motor, and has a three-phase bridge configuration in which three transistors for energizing the motor winding are arranged on each of the upper and lower arms. A drive circuit for the motor according to 3 or 4. 8. The motor according to claim 1, wherein the motor is a three-phase stepping motor, and a three-phase bridge configuration is provided in which three transistors for supplying current to the motor winding are arranged on upper and lower arms, respectively. Or a motor drive circuit according to 4.