JPH0731182A - Inverter control circuit for driving dc motor - Google Patents

Abstract

PURPOSE:To allow control of an inverter without accompanying significant cost increase by employing fine switching IGBTs or MOSFETs on the upper arm of a switching circuit and employing bipolar transistors on the lower arm. CONSTITUTION:Output signals of phases U, V, W from a switching element six phase output circuit 13 are added to an output signal from a PWM circuit 12 through an OR circuit and fed to a drive circuit 8a. On the other hand, output signals of phases X, Y, Z from the output circuit 13 are fed, as they are, to a drive circuit 8b. Both drive circuits 8a, 8b deliver drive signals for respective elements in a switching circuit 3. Since high switching rate is not required for the lower arm 5 of the switching circuit 3, inexpensive bipolar transistors are employed for the lower arm 5 and high speed IGBTs or MOSFETs are employed only for the upper arm 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control circuit for driving a DC motor such as a DC motor or a compressor.

[0002]

2. Description of the Related Art In a conventional inverter control circuit of this type, a switching circuit for driving a DC electric motor such as a DC motor and a compressor is composed of upper and lower arms in total of 6 phases and 6 elements.
Each switching element is a bipolar transistor, an insulated gate bipolar transistor (IGBT) or M
A drive circuit suitable for a switching circuit is formed by an OSFET and the like, and a control circuit including a microcomputer is controlled to switch each switching element to drive a DC motor.

[0003]

However, in the conventional inverter control circuit described above, all the switching elements of the upper and lower arms of the switching circuit are composed of the same element, as seen in JP-A-3-226291. ing.

Therefore, for example, when a bipolar transistor is used as the switching element, the IGBT, MO
Since the switching frequency is lower than the SFET and the switching speed is limited, the rotation control when driving the DC motor is rough, and there is a possibility of causing vibration or noise due to electromagnetic noise or resonance with a peripheral mechanism.

Further, when the IGBT or MOSFET is used, the switching frequency is higher than that of the bipolar transistor, the rotation of the DC motor can be finely controlled, the driving noise and the vibration and noise due to the resonance with the peripheral mechanism are reduced, and the switching element is used. Although the circuit configuration of the drive circuit for switching the IGBT and MOSFET is simple and inexpensive, the cost is high because the IGBT and MOSFET are expensive.

It is an object of the present invention to provide an inverter control circuit which does not cause such noise and a large increase in cost.

[0007]

The present invention has been invented in order to solve the above-mentioned problems of the prior art, in which the upper and lower arms are respectively composed of a plurality of phases and are connected to the AC power source via a rectifying and smoothing circuit. And a drive circuit means for switching the switching circuit to drive a DC motor, and a microcomputer programmed to perform a series of control of the drive circuit means and the like. In the above, there is provided an inverter control circuit for driving a DC motor, wherein the upper arm of the switching circuit is composed of an insulated gate bipolar transistor and the lower arm is composed of a bipolar transistor, and the upper arm is composed of a MOSFET. It is characterized in that it is configured.

[0008]

As described above, according to the present invention, an IGBT or MOSFET capable of fine switching is used for the upper arm three phases of the switching circuit for driving the DC motor, and a bipolar transistor is used for the lower arm three phases.
Compared to using bipolar transistors for all phases,
Fine switching is possible to suppress the generation of electromagnetic noise when driving a DC motor and vibration and noise due to resonance with peripheral mechanisms.

Further, the drive circuit for outputting the switching signal of the IGBT or MOSFET can be controlled by a circuit structure simpler than that of the drive circuit using the bipolar transistor, so that the cost can be reduced.

Therefore, the IGBT or M is applied to all six phases.
The circuit configuration of the switching element is less expensive than the case where the OSFET is used, and it is possible to suppress the generation of electromagnetic noise and vibration or noise due to resonance with the peripheral mechanism when the DC motor is driven.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block-like circuit diagram showing an embodiment of an inverter control circuit for driving a DC motor according to the present invention. FIG. 1 is an AC power supply whose power supply voltage passes through a rectifying / smoothing circuit 2 and a switching circuit 3. It is designed to be supplied to the DC motor 6.

The switching circuit 3 includes an upper arm 4 in which an insulated gate bipolar transistor (hereinafter referred to as an IGBT) serving as a switching element has three phases (U phase, V phase, and W phase) and a bipolar transistor serving as a switching element. The lower arm 5 has three phases (X phase, Y phase, and Z phase), and has an upper and lower six phases.

Position sensors 7a, 7b and 7c for detecting the rotor position are arranged around the DC motor 6, and the outputs of the position sensors 7a, 7b and 7c are passed through a position detection circuit 9 to the rotor in the microcomputer 11. Position detecting means 16
Is configured to be supplied to.

On the other hand, in the microcomputer 11, the rotor position detecting means 16, the rotational speed detecting means 17, the rotational speed determining means 15, and the feedback control means 1 described above are provided.
4, a switching element 6-phase output circuit 13, a duty control means 18, and a PWM (pulse modulation) circuit 12 are provided. The rotation speed detecting means 17 and the rotation speed determining means 15 are connected to the feedback control means 14, and the feedback control means 14 is connected to the switching element 6-phase output circuit 13 and the duty control means 18.

The switching element 6-phase output circuit 13 has an output for upper arm 3 phase (u, v, w) and an output for lower arm 3 phase (x, y, z), and the output for upper arm 3 phase is O
It is connected to the drive circuit 8a through the R circuit 10, and the output for the lower arm three phases is directly connected to the drive circuit 8b.

The other duty control means 18 is connected to the PWM circuit 12, and the PWM circuit 12 is connected to the drive circuit 8a via the OR circuit 10. The drive circuit 8a and the drive circuit 8b are connected to the three phases of the upper arm 4 and the lower arm 5 of the switching circuit 3, respectively.

Further, the duty control means 18, the feedback control means 14, and the rotation speed determination means 15 are a data RAM in the microcomputer 11 and a program RO.
It is composed of M, CPU and the like.

In the above circuit configuration, the alternating current from the alternating current power source 1 is rectified and smoothed into direct current by the rectifying and smoothing circuit 2 and supplied to the switching circuit 3. Each switching element of the switching circuit 3 is a switching element 6-phase output circuit 1
By the switching output from 3, the switching operation is performed via the drive circuits 8a and 8b, a DC voltage is applied to the DC motor 6, and the motor 6 is rotationally driven.

In order to vary the applied voltage, the OR circuit 10 reads the logical sum of the upper arm 3 phase output of the switching element 6 phase output circuit 13 of the microcomputer 11 and the PWM circuit 12 and drives the output of the OR circuit 10. Input to the circuit 8a and the switching element 6-phase output circuit 1
The duty of the applied voltage is varied by inputting the output for the three phases of the lower arm 3 to the drive circuit 8b, and the DC motor 6 is driven by the switching outputs of the drive circuits 8a and 8b.

At the same time, in order to detect the number of revolutions when the DC motor 6 is driven, the signals detected by the position sensors 7a, 7b, 7c, which are Hall devices provided around the DC motor 6, are detected by the position detection circuit 9 The position of the rotor is detected by inputting it to the rotor position detecting means 16 via the, and is input to the rotation speed detecting means 17 to calculate the rotation speed.

The feedback control means 14 compares the data and the data from the rotation speed determination means 15 with data, and the duty control means 18 controls the rotation speed of the DC motor 6. The duty is varied to control the rotation speed of the DC motor 6.

In the above embodiment, the switching element of the upper arm 4 of the switching circuit 3 is an insulated gate bipolar transistor. Instead of this, a MOSFE is used.
You may use T (MOS field effect transistor).

FIG. 2 shows a switching element 6-phase output circuit 13 and a drive circuit 8 from the microcomputer 11.
a and 8b, and in particular, the waveforms (1) to (6) are u of the switching element 6-phase output circuit 13.
To z-phase output, the waveform of (7) is the PWM circuit 12
Shows the output waveform of. Further, (8) to (13) show the output waveforms of the u to z phases of the drive circuits 8a and 8b, respectively.

The u-phase, v-phase, and w-phase output signals of the switching element 6-phase output circuit 13 of the microcomputer 11 are added to the PWM circuit 12 by the OR circuit 10 and input to the drive circuit 8a. The x-phase, y-phase, and z-phase of the switching element 6-phase output circuit 13 are directly input to the drive circuit 8b, and are output as drive signals for the respective elements of the switching circuit 3 from the drive circuits 8a and 8b.

Then, each switching element performs a switching operation by the output drive signal, and the DC motor 6 is rotationally driven at a rotation speed according to the duty. At this time, the lower arm 4 of the switching circuit 3 only performs switching control on the rotor in the DC motor 6, and does not perform chopping control.

In the above operation, the switching circuit 3
The lower arm 5 is not required to perform switching speed because chopping control is not performed. Therefore,
IGBT or MO is provided on the upper arm 4 of the switching circuit 3.
Even if the SFET is used, it is not necessary to use the IGBT or MOSFET for the lower arm 5, and the IGBT or MOSFET is used for the three phases of the upper arm 4 of the switching circuit 3.
The DC motor 6 is rotationally driven by a circuit configuration using bipolar transistors for the three phases of the lower arm 5.

The switching circuit 3 can control the switching and chopping speeds at high speeds, and eliminates electromagnetic noise when the DC motor 6 is driven.
In order to reduce the vibration due to the resonance with the peripheral mechanism, the microcomputer 11 has a programmed content corresponding to the type of the switching element of the switching circuit 3 that is programmed in advance, that is, the IGBT or the MOSFET, compared to the case where the bipolar transistor is used. Performs switching and chopping control at fast timing.

At this time, the upper arm 4 of the switching circuit 3
IGBT and MOS for switching control by voltage control
The drive circuit 8a using the FET has a different circuit configuration from the drive circuit 8b of the bipolar transistor, and has a smaller number of parts used than the drive circuit 8b.

That is, the upper arm 4 is provided with an IGBT or MO.
By using the SFET, the drive circuit 8a becomes cheaper than the drive circuit 8b of the bipolar transistor, and the cost can be reduced.

The same switching element (bipolar transistor, IGBT, MOSFET) is used for all six phases.
Although a modularized product has been realized, an IGBT or MOSFET is used for the three phases of the upper arm 4 of the switching circuit 3 as in the circuit configuration of the present invention,
Since modularization using a bipolar transistor has not been realized in the three phases of the lower arm 5, when the switching circuit 3 is mounted on the board by discrete parts, the board mounting area becomes large, and the peripheral parts and board processing accompanying this increase. Expenses also increase.

Moreover, in the case of a high output DC motor,
A switching element with a large output capacitance must be used. Therefore, in order to drive the base of the bipolar transistor, it is necessary to increase the base current of the drive circuit and the specifications of the drive circuit accordingly, which further increases the cost.

In the switching circuit 3 of the present invention, an IGBT or MOSFET is provided in the upper arm 4 in three phases.
Using a circuit configuration that uses bipolar transistors for the three phases of the lower arm 5, one package is integrated (modularized) to achieve high integration of the control circuit board and at the same time reduce the board mounting area. It is an inverter control circuit that can suppress the substrate processing cost and the cost increase of peripheral parts.

[0033]

As described in the above embodiment, in order to reduce the electromagnetic noise generated when the DC motor is driven by the bipolar transistor and the vibration due to the resonance with the peripheral mechanism, the switching frequency is increased and the chopping cycle is increased. Need to be faster.

As a means for solving this, the switching element of the switching circuit has a high switching frequency I.
This can be solved by using a GBT or MOSFET, but IGBTs and MOSFs are used for all 6 phases of the switching circuit.
When ET is used, the switching element is expensive and the cost is high.

Therefore, in the present invention, the IGBT or MOSFET is used for the three phases of the upper arm of the switching circuit, and the bipolar transistor is used for the three phases of the lower arm, so that it is cheaper than the case of using the IGBT or MOSFET for all six phases. In addition, compared to when using a bipolar transistor, it is possible to control fine switching and chopping, and further it is possible to perform control to eliminate electromagnetic noise when driving a DC motor and reduce vibration due to resonance with peripheral mechanisms, It was possible to improve the noise reduction.

Further, in the present invention, an IGBT or a MOSFE is used.
Since the drive circuit of T performs the switching control by the voltage control, it is possible to simplify and reduce the cost compared with the circuit configuration of the drive circuit of the bipolar transistor in which the switching control is performed by the current control.

Further, the switching circuit 6 phase is connected to the upper arm 3
The circuit is composed of an IGBT or MOSFET for the phase and a bipolar transistor for the three phases of the lower arm for modularization and hybrid IC, and the switching circuit is 1
By using the parts, the mounting area of the control board can be reduced as compared with the case of the discrete parts, which is effective in reducing the board processing cost and peripheral parts cost.

That is, compared with the conventional inverter control circuit, it is possible to drive the DC motor without giving rise to a significant increase in cost and the cost.

[Brief description of drawings]

FIG. 1 is a block-like electric circuit diagram showing an embodiment of a DC motor driving inverter control circuit according to the present invention.

FIG. 2 is a signal waveform diagram provided for explaining the operation of the inverter control circuit for driving a DC motor according to the present invention.

[Explanation of symbols]

 1 Power Supply 2 Rectifying / Smoothing Circuit 3 Switching Circuit 4 Upper Arm 5 Lower Arm 6 DC Motor 8a Drive Circuit 8b Drive Circuit 11 Microcomputer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H02P 6/08

Claims (2)

[Claims] 1. A switching circuit having upper and lower arms each having a plurality of phases and receiving supply of a power supply voltage from an AC power supply through a rectifying and smoothing circuit, and drive circuit means for switching the switching circuit to drive a DC motor. And a microcomputer programmed to perform a series of control of the drive circuit means and the like, wherein the upper arm of the switching circuit is an insulated gate bipolar transistor and the lower arm is a bipolar transistor. An inverter control circuit for driving a DC motor characterized by the above. 2. A switching circuit having upper and lower arms each having a plurality of phases and receiving supply of a power supply voltage from an AC power supply through a rectifying / smoothing circuit, and drive circuit means for switching the switching circuit to drive a DC motor. And a microcomputer programmed to perform a series of control of the drive circuit means and the like, wherein the upper arm of the switching circuit is composed of a MOSFET and the lower arm is composed of a bipolar transistor. Characteristic DC motor drive inverter control circuit.