JPH05276788A - Driver for dc brushless motor - Google Patents

Abstract

PURPOSE:To simplify calculation and to reduce memory capacity by setting the period of synchronizing signal in step with time thereby producing a synchronizing signal having a set period. CONSTITUTION:Upon receiving a command signal 151, period setting means (PS) 101 reads out a period T1 and a period sustaining time t1 from a memory 103 and sets the period T of synchronizing signal at T1. A synchronizing signal output means (SO) 104 produces a synchronizing signal having period T1 and a timer 102 begins to measure the time. When the timer 102 measures a time t1, the PS 101 reads out a period sustaining time t2 for next period T2 from the memory 103 and sets the period T at T2. The SO 104 produces a synchronizing signal having period T and the timer 102 begins to measure the time t2. When the timer 102 measures the time t2, the PS 101 sets the period T at T3 and the SO 104 produces a synchronizing signal having newly set period. In similar manner, period of synchronizing signal is reduced in step with time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a relative position between a magnet rotor and an armature winding based on an induced voltage induced in an armature winding of a brushless DC motor, and detects the relative position. The present invention relates to a brushless DC motor driving device that drives a brushless DC motor based on the above.

[0002]

2. Description of the Related Art A brushless DC motor is usually provided with a detector for detecting the magnetic pole position of a rotor.
In a compressor of an air conditioner that is used under high temperature and high pressure, due to poor reliability, etc., recently, the induced voltage induced in the armature winding causes a difference between the magnet rotor and the armature winding. Various proposals have been made in which the detector is eliminated by detecting the relative position and generating a commutation signal of the inverter based on the detected relative position.

As a brushless DC motor of this type,
Conventionally, there is one as shown in FIG. 4 (Japanese Patent Laid-Open No. 2-197).
No. 291). In FIG. 4, 1 is a DC power supply, 2
Is an inverter and 3 is a brushless DC motor. The inverter 2 includes six transistors Q1 to Q6 and six diodes respectively connected in antiparallel.
The brushless DC motor 3 has an armature winding 4 connected in three phases.
And a magnet rotor 5. 6 is position detecting means, 7 is switching means, 8 is drive signal generating means, 9 is pulse width modulating means, 10 is synchronizing signal generating means, 11 is rotating magnetic field generating signal output means, 12 is start commanding means, and 13 is switching. Command means,
Reference numeral 14 is a duty ratio command means. Since voltage is not induced in the armature winding 4 at startup, the switching command means 13 switches the switching means 7 to the rotating magnetic field generation signal output means 11 side to drive the output signal of the rotating magnetic field generation signal output means 11. The output signal of the drive signal generation means 8 is transmitted to the signal generation means 8, and the pulse width modulation means 9 performs pulse width modulation to drive the transistors Q1 to Q6 of the inverter 2 to start the brushless DC motor 3. Then, when the brushless DC motor 3 rotates and a certain time elapses, the switching means 7 is switched to the position detecting means 6 side, and the induced voltage generated in the armature winding 4 causes the magnetic pole of the magnet rotor 5 to be detected by the position detecting means 6. The position is detected, the signal is transmitted to the drive signal generation means 8, pulse width modulation is applied to it, the transistors Q1 to Q6 are driven, and the brushless DC motor 3 is controlled.

FIG. 5 is a waveform chart of each part of the circuit of FIG. First, the start command signal 151, the switch command unit 13, and the duty ratio command unit 14 respectively start command signals 151,
Switching signal 152 and duty ratio command signal 153 (not shown) are simultaneously output. The synchronization signal generation circuit 10 receiving the start command signal 151 outputs the synchronization signal 100. This synchronization signal is a signal whose frequency increases with time. Based on this synchronization signal 100, the rotating magnetic field generation signal output means 11 outputs signals 111 to 113. This signal is taken into the drive signal generating circuit 8 via the switching circuit 7, and the signals 8 to 86 are output from this circuit 8. Among these outputs, 81 to 83 are pulse width modulated by the pulse width modulation circuit 9 based on the duty ratio command signal, and become drive signals for the transistors Q1 to Q3, respectively, and the signals 84 to 86 are directly used for the transistors Q4 to Q.
6 drive signal.

FIG. 6 is a diagram showing changes over time in the frequency of the synchronizing signal 100 and the duty ratio commanded by the duty ratio command signal 153. As shown in FIG. 6A, the frequency and the duty ratio increase along a straight line having a constant slope.
Then, when these values reach such values that the stable rotation of the brushless DC motor 3 can be maintained, these increases are stopped and the constant values are maintained. After the start-up, when the time t _{0 at} which the brushless DC motor 3 can maintain sufficiently stable rotation has passed, the switching circuit 7 is switched to the position detection circuit 6 side. 6B shows a case where the frequency and the duty ratio are changed so as to increase along a curve whose differential coefficient decreases with time, and FIG. 6C shows the frequency and the duty ratio with time. This is the case where the inclination is changed so as to increase along three straight lines.

As a method of changing the frequency of the synchronizing signal as shown in FIGS. 6A to 6C, a value stored in advance in the ROM or a method of calculating in real time can be considered. 7A is a flowchart showing the operation in the former case, and FIG. 7B is a flowchart showing the operation in the latter case. 7A and 7B, the drive signals (81 to 86) in the current synchronous operation mode are output. For example, in the example of FIG. 5, 81 and 85 are “High” in the first cycle of the sync signal, and “Low” in the other cycles, and 8 in the next cycle.
1 and 86 are "High", others are "Low". The period T of the synchronizing signal is set by a timer. When the timer counts the set value (T), a new cycle is set in the timer and the synchronous operation mode is updated to the next mode. In the case of FIG. 7A, the cycle T set in the timer
n is stored in the ROM in advance and is called from the ROM each time. In the case of FIG. 7B, the period T set in the timer is calculated in real time according to a fixed rule. For example, T = T-Cn (C ₁ = ΔT / 2, C ₂ =
.DELTA.T / 4, ..., Cn = .DELTA.T / (2 to the nth power)).

[0007]

As described above, the conventional brushless DC motor driving device uses the value stored in advance in the ROM as the period of the synchronizing signal, or the value calculated in real time each time. Since it is used, R
There is a problem that the OM capacity becomes large and the calculation time becomes long. Therefore, an object of the present invention is to provide a brushless DC motor drive device having a small ROM capacity and a short calculation time.

[0008]

In order to achieve the above object, the present invention provides an inverter 2 for energizing and interrupting a current to a three-phase armature winding 4 of a brushless DC motor 3, a start command means 12, A synchronizing signal generating means 10 for outputting a synchronizing signal in response to a command from the start commanding means 12, and a relative relationship between the magnet rotor 5 and the armature winding 4 based on the induced voltage induced in the armature winding 4. A position detecting means 6 for detecting a position is provided, and a drive signal for the inverter is generated based on a synchronizing signal output from the synchronizing signal generating means 10 for a certain period of time after the start instruction means 12 generates an instruction. In the brushless DC motor drive device in which the drive signal of the inverter is generated based on the output signal of the position detection means 6 after a certain period of time, the synchronization signal generation means (10) is A cycle setting means (101) for setting the cycle of the sync signal in a stepwise manner with the passage of time, and a sync signal output means (104) for outputting the sync signal of the cycle set by the cycle setting means (101). It is characterized by that.

[0009]

The drive signal for the inverter 2 is generated based on the synchronizing signal output from the synchronizing signal generating means 10 for a fixed time after the start commanding means 12 generates the command, and the position detecting means 6 outputs after the fixed time elapses. A drive signal for the inverter 2 is generated based on the signal. In the sync signal generating means 10, the cycle setting means 101 sets the cycle of the sync signal in a stepwise manner with the passage of time, and the sync signal output means 104 outputs the sync signal of the cycle set by the cycle setting means 101. Output. Since the cycle of the synchronization signal is changed stepwise as described above, the calculation time can be shortened and the storage capacity can be reduced.

[0010]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. The structure of the brushless DC motor drive device of this embodiment is the same as that of the conventional example shown in FIG. 4 except that the synchronization signal generating means 10 has the structure shown in FIG. The synchronizing signal generating means 10 of this embodiment shown in FIG. 1 stores n periods T _{1 to} T _n (T ₁ > T ₂ >...> T _n ) and a duration t _n for each period. Memory 103 and timer 1
02 and a command from the start command means 12 to set a cycle of the sync signal based on the data of the memory 103, and a sync for outputting the sync signal of the cycle set by the cycle setting means 101. The signal output means 104 is provided.

When the cycle setting means 101 receives the command signal 151 from the start command means 12, first, the memory
The period T ₁ and the period maintaining time t ₁ are read from the (ROM) 103 and the period T of the synchronizing signal is set to T ₁ . Then,
The synchronizing signal output means 104 outputs the synchronizing signal of the cycle T ₁ , and at the same time, the timer 102 starts measuring time. When the timer 102 measures the time t ₁ , the cycle setting means 101
Reads the next cycle T ₂ and cycle maintenance time t ₂ from the memory 103, and newly sets the cycle T to T ₂ . Then, the synchronization signal output means 104 outputs the synchronization signal of the newly set cycle T ₂ , and at the same time, the timer 102 starts measuring the time t ₂ . When the timer 102 measures the time t ₂ ,
The cycle setting means 101 sets the cycle T to T ₃ , and the sync signal output means 104 outputs the sync signal of this newly set cycle. Hereinafter, similarly, the cycle of the synchronization signal is made smaller stepwise with respect to time. Since the reciprocal of the period T is the frequency of the sync signal, the frequency of the sync signal increases in a stepwise manner as shown in FIG.

FIG. 2 is a flowchart of the synchronous operation of the drive system of this embodiment. In steps S1 and S2, the cycle setting means 101 reads the cycle T _n from the memory 103 as described above.
And the cycle maintenance time t _n are read out and set as the cycle T and the cycle maintenance time t, respectively. In step 3, the timer 102
Then, the set value of the cycle maintaining timer is set to the above t to start counting. At the same time, in step S4, the set value of the cycle timer of the synchronizing signal output means is set to the above T to start counting. In step S5, the drive signal for the synchronous operation mode at that time is output. Step S
At 6, it is determined whether the cycle timer has finished counting the set value T, and if not, the determination is continued until the counting is finished. On the other hand, if the counting is completed, the process proceeds to step S7 to update the synchronous operation mode, then in step S8 it is judged whether or not the cycle maintaining timer has finished counting the set value t, and if counting is completed, step S
Returning to 1, the settings of the cycle T and the cycle maintenance time t are updated.
On the other hand, if not counting, the process returns to step S4 to set and start the synchronous timer, and the drive signal of the mode at that time is output. In this way, since the cycle (frequency) of the synchronization signal is decreased (increased) stepwise with the passage of time, the calculation time can be shortened and the storage capacity of the memory 103 is small. I'm done. In the above embodiment, the cycles T ₁ , ..., T _n and the cycle maintaining times t ₁ , ..., T _n are stored in the memory 103, but these values may be calculated and obtained in real time. Good.

[0013]

As is apparent from the above, in the brushless DC motor drive device of the present invention, the synchronizing signal generating means sets the period of the synchronizing signal in a stepwise manner with the passage of time, and the above-mentioned cycle. Since the setting means is provided with the synchronizing signal output means for outputting the synchronizing signal of the set period, the calculation becomes simple and the storage capacity is small.

[Brief description of drawings]

FIG. 1 is a block diagram of a synchronization signal generating means used in an embodiment of the present invention.

FIG. 2 is a flowchart of a synchronous driving operation of the above embodiment.

FIG. 3 is a diagram showing changes with time of frequency and voltage of a synchronization signal in the above embodiment.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is a circuit waveform diagram of the above conventional example.

FIG. 6 is a diagram showing a change with time of a frequency of a synchronization signal and a duty ratio of a drive signal in the conventional example.

FIG. 7 is a flowchart of a synchronous driving operation in the above conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Inverter, 3 ... Brushless DC motor, 4 ... Armature winding, 5 ... Magnet rotor, 6 ... Position detecting means, 7 ... Switching means, 8 ... Drive signal generating means, 9 ... Pulse width Modulation means, 10 ... Synchronous signal generation means, 11 ... Rotating magnetic field generation signal output means, 12 ... Start command means, 13 ... Switching command means, 14 ... Duty ratio command means, 101 ... Cycle setting means, 102 ... Timer, 103 ... Memory, 104 ...
Synchronous signal output means.

Claims (1)

[Claims] 1. An inverter (2) for energizing and interrupting current to a three-phase armature winding (4) of a brushless DC motor (3),
A start command means (12), a sync signal generating means (10) for outputting a sync signal according to the command of the start command means (12),
A position detecting means (6) for detecting the relative position of the magnet rotor (5) and the armature winding (4) based on the induced voltage induced in the armature winding (4), The start command means (1
The synchronizing signal generating means (1
0) generates a drive signal for the inverter on the basis of the synchronizing signal output from 0), and after the lapse of the predetermined time, generates a drive signal for the inverter on the basis of the output signal of the position detecting means (6). In the brushless DC motor driving device, the synchronization signal generating means (10) sets the cycle of the synchronization signal in a stepwise manner with the passage of time.
01) and a sync signal output means (104) for outputting a sync signal having a cycle set by the cycle setting means (101), and a brushless DC motor drive device.