JP3241631B2 - Power conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion circuit for driving a motor, and more particularly to a power conversion circuit for driving a motor used for high-speed rotation for medical or industrial use.

[0002]

2. Description of the Related Art A driving circuit for a three-phase brushless motor according to the prior art will be described with reference to FIG. The drive circuit is configured by arranging switches SW1 to SW6 on a drive element including six FETs 1 to 6 respectively. Here, when a current flows in the U-phase-V-phase, the FET1 is turned on by SW1 and the FET4 is turned on by SW4. Similarly, when a current flows through the V phase-W phase, S
FET3 is turned on by W3 and FET is turned on by SW6.
6 is turned on. When a current flows through the W-phase and the U-phase, the FET5 is turned on by SW5 and the FET2 is turned on by SW2.

[0003]

Here, as shown in FIG. 6, a switch SW for turning on / off the FET1 to FET6 is used.
Power supply circuits V1 to V6 were required for 1 to SW6 (comprising, for example, transistors). Here, the switches SW2, SW4, and SW6 for turning on and off the lower FETs 2, 4, and 6 are connected to the ground, so that the power supplies V2, V4, and V6 can be shared, but these are shared. Thus, four power supply circuits are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a power conversion circuit capable of controlling an FET with a single power supply.

Another object of the present invention is to provide a power conversion circuit that can be restarted quickly even after the power supply has been stopped for a long time.

[0006]

In order to achieve the above object, the present invention provides an upper MOSFET connected to a higher potential.
T (hereinafter referred to as an FET), an upper-stage control circuit including a photocoupler for turning on / off the upper-stage FET, a lower-stage FET connected to the ground side or the negative potential side, and turning on / off the lower-stage FET. A lower-stage control circuit comprising a photocoupler , and an upper-stage FET and a lower-stage FE.
T is connected in series to form a bridge circuit, and the upper and lower FETs are switched by pulse width modulation control (hereinafter, referred to as PWM control). To supply power in parallel to the power supply of the upper control circuit in series with the
When the lower stage control circuit turns on the lower stage FET, the capacitor is charged, and the upper stage control circuit turns on the upper stage FET by using the electric charge charged in the capacitor. While driving a single-phase or multi-phase power conversion circuit with a single power supply, when power supply is stopped, the upper-stage control circuit turns off the upper-stage FET, and the lower-stage control circuit turns on the lower-stage FET. have a sequence for charging the capacitor, the rotation state of the motor, and the stop state detection
When the motor stops for a predetermined time or more,
Charge the capacitor until a turn command is given.
Cie with switching to Sequence, and technical features of the shorting braking the motor.

[0007]

[0008]

In the present invention, the lower-stage control circuit controls the lower-stage FE.
When T is turned on, the capacitor connected in series to the lower FET is charged, and the upper FET is turned on by the upper control circuit using the charge charged in the capacitor. For this reason, the upper and lower FEs of a single-phase or multi-phase power conversion circuit
T can be controlled with a single power supply. When the power supply is stopped, the upper FET is turned off by the upper control circuit, the lower FET is turned on by the lower control circuit, and the capacitor is charged, so that the electric charge stored in the capacitor causes the upper control circuit to operate the upper FET. Since the FET can be turned on, it can be quickly restarted even after the power supply is stopped for a long time.

In the present invention, the power conversion circuit detects the rotation state and the stop state of the motor, and when the motor stops for a predetermined time or more, charges the capacitor until a next rotation command is given. And the motor is short-circuit braked.

In the present invention, since the upper control circuit and the lower control circuit are composed of photocouplers, the input and the output are separated by the photocoupler, so that a malfunction due to noise from the input line can be prevented.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the power conversion circuit according to the present invention will be described. The brushless motor driven by the drive circuit of this embodiment has a four-pole permanent magnet disposed on the rotor side, and U-phase, V-phase, and W-phase excited on the stator side by current from the brushless motor drive circuit. It consists of phase coils.

FIG. 1 shows a power conversion circuit according to a first embodiment. The power conversion circuit is mounted on the brushless motor side and filters a signal from the Hall IC 10 for detecting the polarity of the four permanent magnets on the rotor side, and a triangular wave generating circuit 18 for generating a triangular wave.
And a comparator 16 for transmitting a PWM output for PWM control of the brushless motor. That is, the comparator 16 compares the DA signal obtained by converting the rotation speed of the brushless motor, which has smoothed the signal from the Hall IC into a voltage value, with the triangular wave from the triangular wave generating circuit 18, and
Send WM output.

The CPU 14 generates a drive signal for the photocoupler / power circuit 20 based on the signal of the Hall IC 10 from the filter 12 and the PWM output from the comparator 16.

The circuit configuration of the photocoupler power circuit 20 shown in FIG. 1 will be described with reference to FIG. The photocoupler power circuit 20 is configured as a bridge circuit including three upper-stage FETs 1, 3, and 5 connected to the power supply Vcc side, and lower-stage FETs 2, 4, and 6 connected to the ground side. Six photocouplers FC1 to FC6 for turning on and off the upper and lower FET1 to FET6 are connected to the upper and lower FET1 to FET6, respectively.

The input of the photocoupler FC1 for turning on / off the upper side FET1 is + 15V via the diode D1.
, And the output side of the photocoupler FC1 is connected to the gate side of the FET1. A resistor R1 is connected in series with the photocoupler FC1. This photocoupler FC1 and resistor R1
And a lower-stage FET2 is connected in series with the capacitor C1.

The input of the photocoupler FC2 for turning on / off the lower side FET2 is + 15V via the diode D2.
And the output side of the photocoupler FC2 is connected to the gate side of the FET2 and to the ground through a resistor R2.
The upper FET 1 and the lower FET 2 are connected in series, and are configured so that a current is applied to a U phase of a stator coil of a brushless motor (not shown) from a connection point between the FET 1 and the FET 2. .

The operation of the photocoupler power circuit 20 will be described. Here, when a current flows through the W-phase to U-phase of the stator coil, the photocouplers FC5 and FC2 shown in FIG. 2 are turned on by a signal from the CPU 14 shown in FIG. When FET5 is turned on, the lower FE is activated by the photocoupler FC2.
T2 is turned on, and the power supply voltage Vcc is applied to the W phase-U phase of the stator coil. That is, a current flows in the order of Vcc-FET5-W-phase of coil-U-phase (not shown) -FET2-resistor R7-ground. At this time, + 15V FET
The current from the control voltage line flows to the FET2 side via the diode D1 and the capacitor C1, and the capacitor C1
Stores electric charges of the polarity shown in FIG.

Next, when a current flows through the U-phase to V-phase of the stator coil, the photocouplers FC1 and FC4 are turned on by a signal from the CPU 14. Here, the photocoupler F
When C1 is turned on, the electric charge charged in the capacitor C1 when the FET2 is turned on is applied to the gate of the FET1 through the photocoupler FC1 to turn on the FET1. On the other hand, by turning on the photocoupler FC4, +15
The current from the V FET control voltage line is a diode D
4. The current flows to the ground side via the photocoupler FC4 and the resistor R4, and the potential divided by the resistor R4 is applied to the gate side of the FET 4, turning on the FET 4. FET1,
When the FET4 is turned on, the power supply voltage V is applied to the U-phase-V-phase coil.
cc is applied. When the FET 4 is turned on, the capacitor C3 is charged to the polarity shown in the figure.

When a current flows in the V-U phase of the stator coil, the photocouplers FC3 and FC6 are turned on. Here, when the photocoupler FC3 is turned on, the capacitor C3
The FET3 is turned on by the electric charge charged in the FET3. On the other hand, when the photocoupler FC6 is turned on, the FET 6 is turned on.
When the FETs 3 and 6 are turned on, the power supply voltage Vcc is applied to the U-phase to W-phase coils. When the FET 6 is turned on, the capacitor C5 is charged to the polarity shown in the figure. When the above-described W phase is excited by this electric charge, the upper-stage FET 5 is turned on.

As described above, the lower-stage photocouplers FC2, FC4, and FC6 are used by the lower-stage photocouplers FC2, FC4, and FC6.
4. When the FET6 is turned on, the lower FET, FET
4. Capacitors C1 and C connected in series to FET6
3, C5 is charged respectively, and using the charged electric charge,
The upper photocouplers FC1, FC3, and FC5 sequentially turn on the upper FET1, FET3, and FET5. For this reason, the upper and lower FET 1 of the three-phase power conversion circuit
To FET6 as a single power supply (+ 15V FET control voltage)
Can be controlled by

Next, the operation when the power conversion circuit stops the brushless motor will be described. The CPU 14 shown in FIG. 1 monitors a signal from the Hall IC 10. Here, if the CPU 14 detects that the signal from the Hall IC 10 does not change for a predetermined time or more, that is, detects the stop of the rotation of the brushless motor, the CPU 14 of the photocoupler power circuit 20 shown in FIG. F
Turn off all C5, and lower photocouplers FC2, FC
4. Turn on FC6 to short-circuit brake the motor. That is,
Switch to charging sequence. Thereby, the FET
2. The capacitors C1, C3 and C5 connected in series to the FET4 and the FET6 are all charged.

When the brushless motor is restarted, one of the upper and lower photocouplers is turned on to excite any of the U-phase, V-phase and W-phase coils. Here, in the present embodiment, the upper FET
1. Since the capacitors C1, C3, and C5 for turning on the FET3 and the FET5 are all kept in the charged state during the stop, the upper stage FE is turned on by turning on the photocoupler.
T1, FET3, and FET5 can be immediately turned on.

That is, in the configuration shown in FIG. 2, when the brushless motor is stopped, the upper-stage FET1, FET3, FET5
Is turned off and the lower-stage FET2, FET4, and FET6 are not switched to the conductive state, and the capacitors C1, C3,
The electric charge stored in C5 is gradually discharged. Even after the brushless motor is stopped for a long time, even if the photocouplers FC1, FC3, and FC5 floating from the ground are turned on, the FET1, FET3, and FET5 are turned off unless the potential is applied from the capacitors C1, C3, and C5. Cannot turn on. On the other hand, in the power conversion circuit of the first embodiment,
While the brushless motor is stopped, the capacitors C1, C3,
By charging all of C5, the upper stage FET1, FET3, FET
Since the brushless motor 5 can be turned on, the brushless motor can be quickly restarted even after being stopped for a long time.

When restarting, it is also possible to charge only the upper-stage FET capacitor for energizing the coil to be excited first. For example, when starting the excitation from the U-phase, the capacitor C1 that drives the upper FET 1
It is conceivable that only the battery is charged. On the other hand, in the present embodiment, all the lower FETs 2, 4, and 6 are turned on while the brushless motor is stopped, and the upper FE is turned on.
All capacitors C1, C3 and C5 for T drive are charged. For this reason, the F
Since it is not necessary to specify the ET, all the capacitors C1, C3, and C5 are all charged in advance, and it is not necessary to gradually charge the capacitors with the start. FET3 and FET5 can be turned on smoothly.

In this embodiment, the capacitor is charged while the motor is stopped. Instead, the capacitor may be charged and the coil may be energized immediately before starting. .

In this embodiment, the upper and lower F
An element for controlling ET includes photocouplers FC1 to FC6. Since the input and output are separated by the photocoupler, malfunction does not occur even if noise generated in the brushless motor or the drive circuit is superimposed on the input line side.

Next, a modified example of the photocoupler / power circuit of the power conversion circuit according to the first embodiment shown in FIG. 2 will be described with reference to FIG. In the circuit configuration according to the modification shown in FIG. 3, the lower photocoupler FC
2. In parallel with FC4, FC6, capacitors C2, C4,
C6 is connected. In the circuit configuration according to this modification, when the lower-stage FET2, FET4, and FET6 are turned on, the lower-stage photocouplers FC2, FC4, F4
Since the charges of the capacitors C2, C4, and C6 connected to C6 are applied, the lower-stage FET can be smoothly switched to the conductive state.

Next, a second embodiment in which the configuration of the present invention is applied to a two-phase power conversion circuit will be described with reference to FIG. In this embodiment, a capacitor C1 is connected in parallel to a photocoupler FC1 for turning on / off the upper FET 1 and a photocoupler FC3 for turning on / off the upper FET3.
1, C3 are connected. Here, FET1 and FET
4 is turned on, the capacitor C3 connected in series with the FET 4 is charged. Then, when the FET3 and the FET2 are turned on, the FET3 is turned on by the electric charge charged in the capacitor C3.

Also, in the configuration of the second embodiment, when the brushless motor M is stopped, the lower FET
2. When the FET 4 is turned on, the capacitors C1, C
3 is charged, and when restarting, the upper stage FET1, FET
3 can be quickly turned on.

In a conventional two-phase FET bridge, four FET power supplies are used (three power supplies are used when the lower stage is shared).
However, in the second embodiment, all FETs can be switched by a single power supply.

Next, a third embodiment in which the configuration of the present invention is applied to a single-phase power conversion circuit will be described with reference to FIG. In this embodiment, a capacitor C1 is connected in parallel to a photocoupler FC1 that turns on and off the upper-stage FET1. Here, when the lower stage FET 2 is turned on, the capacitor C1 connected in series with the FET 2
Is charged. When the photocoupler FC1 is turned on, the electric charge stored in the capacitor C1 causes the FET
2 is turned on.

Also, in the configuration of the third embodiment, when the brushless motor M is stopped, the lower FET 2
Is turned on, the capacitor C1 is charged, so that the upper-stage FET 1 can be quickly turned on at the time of restart.

In the conventional single-phase type FET bridge, two power supplies for the FETs are required.
In embodiments, a single power supply can switch two FETs.

In the above-described embodiment, a single-phase, two-phase, or three-phase drive circuit has been exemplified. However, it is needless to say that the drive circuit of the present invention can be applied to a four-phase or more drive circuit.

[0036]

As described above, according to the present invention, when the lower FET is turned on by the lower photocoupler (control circuit), the capacitor connected in series to the lower FET is charged and charged. The upper-stage FET connected in parallel to the capacitor is turned on by using the accumulated charge. Therefore, the upper and lower FETs of the single-phase, two-phase, three-phase, and four-phase or more drive circuits of the motor can be controlled by a single power supply.

When the motor is stopped, the lower FE
T is made conductive, and the capacitor connected in series to the lower FET is charged. When the motor is restarted, the upper FET can be immediately turned on by turning on the upper photocoupler (control circuit), so that the brushless motor can be restarted promptly even after being stopped for a long time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power conversion circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the power circuit shown in FIG.

FIG. 3 is a circuit diagram of a power circuit according to a modification of the first embodiment.

FIG. 4 is a circuit diagram of a two-phase power circuit according to a second embodiment.

FIG. 5 is a circuit diagram of a single-phase power circuit according to a third embodiment.

FIG. 6 is a circuit diagram of a power circuit according to the related art.

[Explanation of symbols]

 Reference Signs List 10 Hall IC 12 Filter 14 CPU 16 Comparator 18 Triangular wave generation circuit 20 Photocoupler / power circuit 30 Regenerative dissipation circuit R10 resistor

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor, Hirokazu Yatsushiro 1-1, Ibigawa-cho, Ibi-gun, Gifu Prefecture Ibiden Co., Ltd. Ogaki-Kita Plant JP-A-6-225583 (JP, A) JP-A-7-303389 (JP, A) JP-A-3-74194 (JP, A) JP-A-3-34696 (JP, U) (58) Fields surveyed ( Int.Cl. ⁷ , DB name) H02P 6/08

Claims (1)

(57) [Claims] 1. An upper MOSF connected to a high potential side
ET (hereinafter referred to as FET) and the upper FET
An upper-stage control circuit including a photocoupler that is turned off, a lower-stage FET connected to the ground side or the negative potential side, and a lower-stage control circuit including a photocoupler that turns on and off the lower-stage FET. The upper FET and the lower FET are connected in series to form a bridge circuit.
Is a single-phase or multi-phase power conversion circuit that performs switching by pulse width modulation control (hereinafter referred to as PWM control), and supplies power in series with the lower FET and in parallel with the power supply of the upper control circuit. When the lower-stage FET is turned on by the lower-stage control circuit, the capacitor is charged, and the upper-stage F is controlled by the upper-stage control circuit using the electric charge charged in the capacitor.
By turning on the ET, a single power supply drives a single-phase or multi-phase power conversion circuit, and when the power supply is stopped, the upper-stage control circuit turns off the upper-stage FET, and the lower-stage control circuit further turns off the upper-stage FET. the lower FET is turned on to have the sequence to charge the capacitor, detects the rotational state, and the stopped state of the motor, the motor
Is stopped for more than the specified time, the next rotation command is given.
Until the charging cycle starts.
A power conversion circuit characterized by switching and short-circuit braking a motor .