JPS59172991A - Rotor position detector of brushless dc motor - Google Patents

Abstract

PURPOSE:To effectively detect the position of a rotor by obtaining a signal having the same phase or 180 deg. different phase as a phase voltage from the output of a phase shifter and using it as a position detection signal of a rotor. CONSTITUTION:An imaginary neutral point circuit 101 is connected in parallel with an inverter 7 to the output terminal of a rectifier 2. On the other hand, clampers connected to the phases of stator windings 5 are coupled in a start connection, and a neutral point is connected to an imaginary neutral point EN. Rectangular signals having the same phase or 180 deg. different phase as the voltages of the phases of the windings 5 are obtained from a phase shifter 103 coupled in a star connection with the phase shifter, a subtraction amplifier 105 and an integrator 106, and substantially triangular signals V4-W4 of 90 deg. phase delay are outputted. A comparator 107 compares the signals V4-W4 with imaginary neutral point voltage, and delivers as position detection signals the rectangular signals V0-W0 of 120 deg. different phases to a distributor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the rotor position of a planless DC motor using the winding voltage of a stator winding. Various methods have been proposed for obtaining the child position detection signal directly from the winding voltage of the stator winding. An example thereof will be explained with reference to FIG. l is a commercial AC power supply (for example, ACloQV, Otsu OHJ, 2 is a rectifier circuit that rectifies and smoothes the AC power supply l and outputs it, and a diode D
The anode of the diode D2 and the cathode of the diode D2 are connected to one end of the AC power supply via the power factor correction glue handle 3,
A circuit in which capacitor C and 02 are connected in series between the cathode of diode D and the anode of diode D2 is inserted in parallel with capacitor C3, and the connection point between capacitor C and 02 is connected to the AC power source. Connect to the other end of
A so-called voltage doubler rectifier circuit is formed, and the capacitor C3
DC output is sent out between the terminals. The motor is a brushless DC motor (hereinafter simply referred to as the motor).
It consists of a stator winding S and a rotor B, which are connected in a three-phase star shape. 7 is a so-called 720 which is connected to the output end of the rectifier circuit and controls the energization of the stator winding S of the electric motor.
° An energizing type pulse width control type inverter circuit (hereinafter simply referred to as an inverter circuit), which consists of transistors and other switching elements QuIQx, QvIQy and Q
7. Connect two Q2 in series to form a set.

, and Q is connected to each phase of the stator winding S as an output terminal, and the stator winding S is energized for each phase by conduction of each switching element.

Then, the switching elements QuIQxIQv, Qy
.

QW, Q2 pace has a buffer driver BD that isolates the input side and output side and sends out the drive output.
are connected to each other. This is a position detection circuit connected to each phase of the stator winding S to obtain a position detection signal of the rotor B from the stator winding voltage.
u, Cv, CvII) with resistors Ru, Rv at one end, respectively.
, the capacitor Cu of the phase i, which consists of a resistor and a capacitor connected to each phase of the stator winding S via Rw,
Cv, ・C, /) The other end is commonly connected to serve as a neutral point, and this is a star-connected phase shift circuit that is grounded, and the output terminal of each phase shifter (resistor and The non-inverting input terminals of comparators CP, CPv, and CPw each consisting of an operational amplifier are connected to the capacitor connection point), and the comparators OP u *
C! It is formed from a comparator circuit IO with the inverting input terminal of P v * OP w grounded (i.e. connected to the neutral point of the phase shift circuit), and is The winding voltages of the respective phases of the stator winding 3 are received as phase voltages by each phase shifter of the phase shift circuit to form a substantially triangular wave voltage with an O0 phase lag, and this is applied to the comparator CPU.
By comparing the neutral point voltage with ICPv and CPw,
/2 from the output terminals of comparators CP, CPv, and CPw, respectively.
00 Comparison signal U of rectangular waves with different phases. , ■o, W0 are obtained with a duty ratio of SO%, and this is used as a position detection signal. o// is a comparison signal U of the comparison circuit 10 of the position detection circuit. , Vo.

W is a combination of logic circuits (for example ■.・Wo, Uo・Vo
.

switching elements Qu, Qx, Qv of the inverter circuit 7;

No., Qw, Q2 are sequentially conducted (for example, Qu-QX, -
Qv-QX-(5) Q, , = -Q, y)) is a distribution circuit configured to send out opening/closing signals. Further, this distribution circuit l/ sends out a switching signal so that the switching element of the inverter circuit 7 is turned off by a signal from a load current detection circuit /3 connected from a current detector /2 that detects the load current. The circuit is designed to protect against overcurrent, and when the motor t is started, a signal from the starting circuit /l sends out an opening/closing signal that sequentially turns on and off the switching elements.

In such a rotor position detection method, if the motor speed is controlled by a pulse width control method (that is, by a logical combination of the opening/closing signal of the distribution circuit // and the output signal of a pulse width modulation circuit (not shown) The position detection of the rotor in the case where the switching element of the inverter circuit 7 is switched by pulse width modulation is explained with reference to Fig. 2. The first figure shows the position detection circuit when the switching element is switched by pulse width modulation. This figure shows the waveform (6) of the input/output of the phase shift circuit and the output of the comparator circuit IO. Figure (a) is for no load and light load, and figure (b) is for heavy load. In the same figure, ■8□ shows the current cutoff when switching the switching element (for example, when switching from Qu to Qv). The reverse voltage (hereinafter referred to as spike voltage) generated by the release of electromagnetic energy accumulated by the leakage inductance of the stator winding is caused by the reverse voltage (hereinafter referred to as spike voltage). Similarly, the reverse voltage generated by the release of electromagnetic energy (hereinafter referred to as cutting spike), ■ is the induced voltage in the stator winding, ■
, respectively indicate the phase voltages of the stator windings.

During no-load and light-load conditions (Fig. 2 (a)), the ON period of the pulse-width modulated switching element is short and the current in the stator winding is small, so the electromagnetic energy is small. , the cutting spike caused by this ■82
becomes linear, and after this generation, an induced voltage due to the rotation of the motor is generated, and then when the switching element is turned on, the voltage waveform becomes the voltage waveform to which the DC output of the rectifier circuit is applied.
Figure (a) input). Therefore, the output of the phase shift circuit 7 has a shape of η7' in which a triangular high frequency component due to the cutting spike S2 is superimposed (output of 9 in Fig. 2 (a)), which is approximately triangular with a phase lag of O0. Comparison circuit 10 compares the unstable zero-crossing point of the wavy output that alternates between positive and negative.
The rising and falling points of the rectangular wave fluctuate and become unstable, making it difficult to accurately obtain a signal with an O0 phase delay with respect to the phase voltage (2).

In addition, under heavy load (Figure 2 (b)), the on-period of the switching element is extended to maintain the stator winding voltage, so the stator winding current is reduced. As the electromagnetic energy increases due to the leakage inductance, the width of the cutting spike S2 that occurs due to the release of this also increases, and the pulse width modulated switching element increases before the induced voltage of the electric motor is generated. When it is turned on, DC output is applied to the stator winding, creating a waveform that alternates between positive and negative at the so-called chopper frequency (input of Ω diagram (b) 7).
.

For this reason, the ripple increases and the zero-crossing point of the output waveform, which alternates between positive and negative in a substantially triangular waveform with a phase lag of O0, equivalently advances in phase, and the comparison signal of the comparator circuit 10 that compares these points is in phase. For w fE vF, as described above, it is no longer possible to accurately convert a signal with a phase delay of 0° to 4M.

Furthermore, when overloaded (2), the on period of the switching element is made longer (for example, 1200
Since the current is further increased and the electromagnetic energy due to leakage inductance is also increased, the width of the spike voltage Vs generated when switching the switching element is also increased ( Therefore, the zero-crossing point of the output waveform, which alternates between positive and negative in a substantially triangular waveform with a 900 phase delay in the phase shift circuit, equivalently becomes a large leading phase, and this is compared. Comparison circuit 1
Similarly to the above, with the comparison signal of 0, it is no longer possible to obtain a signal with an accurate 900 phase delay with respect to the phase voltage . As a result, the comparison signal U of the position detection circuit g. .

V and W cannot be used as rotor position detection signals, and if they are used as they are, stable operation of the motor (9) cannot be obtained. The purpose of this invention is to provide a device that can accurately detect the position of the rotor of an electric motor even when the switching element is controlled by pulse width modulation.

In order to achieve the above object, the present invention has been made to achieve the above object.Even when the switching element is controlled by pulse width modulation, the switching element is not switched near the zero-crossing point of the phase voltage. Focusing on the point that high-frequency components are not superimposed, the system is configured to obtain a signal from the output of the phase shift circuit that has the same phase as the phase voltage or a phase difference of /1r00, and uses this as a rotor position detection signal. It is.

Hereinafter, embodiments of the present invention will be described with reference to three fangs and a spear diagram. Since the configuration is the same as that in FIG. 7 except for the position detection circuit, the same reference numerals are given and the explanation will be repeated to avoid duplication. In Figure 3 (10), lOO is a position detection circuit that detects the position of the rotor of the electric motor, and a virtual neutral point circuit lO/ is inserted in parallel with the inverter circuit 7 at the output end of the rectifier circuit 2. , a voltage clamp circuit 102 in which clamp devices connected to each phase of the stator winding S are connected in a star shape, and this voltage clamp circuit 1
A phase shift circuit 103 in which phase shifters connected to the output terminals of each clamper of 02 are connected in a star shape, and the output of each phase shifter of this phase shift circuit 103 is the same as each phase voltage of the stator winding S. A position detection signal is obtained by obtaining a rectangular waveform signal having a -phase or a 7g00 phase difference. These circuits will be explained. The above virtual neutral point circuit 10/ has two capacitors C4 and C5 inserted in series between the output terminals of a rectifier circuit, and a resistor R between the terminals of the capacitors C4 and C5.
Insert capacitors C4 and R2, respectively, and connect the capacitors C4 and 05.
The connection point is set as a virtual neutral point EN and the circuit is grounded, so that a virtual neutral point voltage of % of the output voltage of the rectifier circuit 2 is always obtained. Therefore, the output of the rectifier circuit 2 which rectifies and smoothes the AC power supply, that is, each output terminal of the inverter circuit 7 connected in a bridge form to the DC power supply, is connected to each phase of the stator winding S having a three-phase star connection. By doing so, the voltage at the neutral point not derived from the stator winding S is substantially reduced to the connection point of the capacitors C4 and 05 (virtual neutral point E1m).
The virtual neutral point voltage is obtained from this voltage. The capacitors C4 and C5 and the resistors R and R2 have the same value (C4=CB=R), and the value is such that the capacitor C415I 1 2 C5 sufficiently removes the induced voltage caused by the AC power supply. Therefore, the impedance is selected to be a value sufficiently lower than the leakage impedance when the switching element of the inverter circuit 7 is turned off, and the resistor R and R2 are the capacitors C4 and C.
Select a value that is sufficiently lower than the leakage resistance of 5.
The direct voltage of the virtual neutral point is set to % of the output voltage of the rectifier circuit 2, and a stable voltage is obtained with respect to the AC power supply.For example, c = C>i oμF, R = R 1
00 will be Ω4 5-
A zero voltage clamp circuit 10Ω, which may be set as 1 to 2, consists of a pair of constant voltage diodes ZD, ZD2, ZD and ZD4, whose anodes are connected in anti-series to each phase of the stator winding. The above-mentioned constant voltage diode ZD work of ZD5 and ZD6, ZD3. The cathodes of ZD5 are connected through resistors R3°R41R5, and constant voltage diodes ZD21ZD4. Connect the cathodes of ZD6 in common to form a neutral point, connect this neutral point to the above virtual neutral point to ground the circuit, and connect the clamp device consisting of a resistor and a pair of constant voltage diodes to a three-phase star connection. The connection point between the resistor of each clamp device and the constant voltage diode (R3 and ZD
R and ZD3. connection point of R5 and ZD5) to output terminal 1
4, each phase voltage of the stator winding S is clamped to a constant value determined from the Zener voltage 2, and outputs are sent from the output terminals. The phase shift circuit 103 connects one end of capacitors C6, C7, C8α to the output terminal of each clamper of the voltage clamp circuit 102, and resistors R6, C8α, respectively.
Connected through R7 and R8, and the above capacitors C6 and C7
, the other ends of C8 are commonly connected to form a neutral point, and this neutral point is connected to the above virtual neutral point KN to ground the circuit. Form a wire connection and connect the above capacitor C6°C
Between the terminals of 7 and C8, in order to prevent fluctuations in the time constant caused by variations in leakage resistance between the capacitors,
Bypass resistors RR and R are inserted at 9'1O11, respectively, and each phase shifter is connected to the connection point of the resistor and capacitor (R
6 and C6, Rヮ and C7, R8 and C8 connection point) as the output terminal, and output voltage of approximately triangular waveform whose phase is shifted to the phase of the input Oo as output signal U□, ■□, W Each of them is sent out. The comparison circuit 10'l is connected to the output terminal of each phase shifter of the phase shift circuit 103 and outputs a rectangular wave output signal U3 having a phase difference of approximately /go° from each phase voltage of the stator winding S.゜■3. W3 and the output signal U3. V3. W3 is phase-shifted to a phase lag of O0 to generate a substantially triangular waveform output signal U4. V4. W4
The outputs of the integrating section 10 B and the integrating section IO B are coupled with AC, and compared and inverted with the above virtual neutral point voltage, so that the phase voltage ■ - and O0 are delayed in phase. output signal U. + Vow and Wo. The subtraction amplifier section 10S has operational amplifiers A, A2, . The inverting input terminal of A3 is connected to 12 13 through resistors R, R, and R, respectively.
14 At the same time, connect the non-inverting input terminal of operational amplifier A + A21 A3 to the resistor and capacitor (R□5 and C
0°R and C, R and C)
Connect via 10 17 11,
A feedback resistor R8'19'R is inserted between the inverting input terminal and the output terminal of the operational amplifier IIA"21 A3, and the above resistors R, R, R20121314 and feedback resistors R,, R9' The relationship with R20 is R engineering, = R engineering.

-R engineering. <<R engineering, = R□9 = R20, and operational amplifiers A□, A2. Output signals U2.A3 are sent from the output terminals au, av, awi+5 of the delay circuit. ■2. W2 and the phase shifter output signal U1. Vo
, W engineering and subtracting U knee U,.

V knee V2. W knee W,) is inverted and amplified with a large amplification degree to produce a rectangular wave output signal U4. V4゜W
4, respectively. The delay circuit in the subtraction amplifier circuit 103 is provided to accurately detect the inflection point at the peak of the output waveform of each phase shifter (i.e., the phase voltage ρ zero cross point), and the OR time constant is The output is set to approximately 1 ottS to 700 μs to send out an output whose phase is slightly delayed by ψ from the output of the phase shifter, and the operational amplifiers A, A2. The amplification degree of A3 is set to be high so that the relationship is R, = R□3 = R, 〈R, = R□9 = R20, so a rectangular wave with saturated ripples is generated by inverse amplification. The output signal is

Integration section 101. is the operational amplifier A of the subtractive amplifier section 10S.
Engineering, A2. Connect Ω resistors and capacitors (R21, R22 and C12' R23,
R24, 32, R26 and C engineering. ) are connected in series, C and R respectively, and the connection points of the above two resistors (R2□ and R22゜R23 and R24' and the connection points of R25 and R26) are the output terminals, and the above two resistors are connected to R2. □=R23=R25
>> When the relationship of R22"R24"' R26 is set and the output of the subtraction amplifier 10S is integrated with a phase lag of OO, the zero-crossing point of the approximately triangular integral waveform that alternates between positive and negative will be slightly advanced in phase. (i.e., the zero-crossing point of the integral waveform corresponds to the zero-crossing point of the phase voltage VF with a phase delay of OO).
' W4 is sent out from each of the above output terminals. The comparator 107 connects the inverting input terminals of the comparators CP+CP and CP, each of which is an operational amplifier, to each output terminal of the integrator 10B.
W Connected through capacitors c, C, and C, and the above anti-15
16 17 Resistors R27+R and R between the input terminal and circuit ground, respectively.
Insert the above comparator CP, CPvI28 2
9
Connect the non-inverting input terminal of uCP to the circuit ground and compare each output of the integrating section IO via AC coupling @cp.

A comparison signal U of rectangular waves having a phase difference of 1200 degrees is output from the output terminal of the comparator cp + OPv + cpw. , vo, and Wo are respectively sent to the distribution circuit 11 with a duty ratio of 5Oq6.

Next, the position detection operation of rotor B will be explained. The rectifier circuit 2 receives an AC power supply l (for example, Ac1oov, OR2) through a reactor 3, and inverts the DC output voltage by rectifying and smoothing it into a double voltage (17), the overcurrent circuit 7, and the virtual neutral point circuit 101. supply to.

Next, start the electric motor l. As is well known, the distribution circuit/1 responds to the starting signal from the starting circuit/4t, and the switching element Q of the inverter circuit 7 is connected to the output terminal of the distribution circuit/1.
Opening/closing signals are sequentially sent to the bases of u, QXIQvlQy, Qw, and C2 via the pace driver BD to control the switching elements, for example, Qu-hQ, 2-'Q, , iQ.
The conduction is interrupted in the order of
The starting circuit /g performs a so-called additional braking operation to gradually increase the rotation speed to a predetermined rotation speed (for example, about 00 r qp 4 m). Thereafter, a so-called self-control operation is performed in which each switching element of the inverter circuit 7 is made conductive or disconnected at an appropriate time by the position detection signal from the position detection circuit 100 via the distribution circuit //.

In this self-control operation, when the switching element is pulse-width modulated (18) and switched in order to control the speed of the motor t, the winding voltage of each phase of the stator winding S is rectified by the conduction and interruption of the switching element. When the output of circuit 2 is applied, looking at the negative phase component, there is a cutting spike 82 that occurs during switching and a spike voltage 8 □ that occurs when switching the switching element, and the voltage is positive and negative around the virtual neutral point EN. This is shown as an alternating substantially trapezoidal voltage waveform, which is input as a phase voltage (2) to each clamp device of the voltage clamp circuit 10Ω (input of the tooth diagram 702). At this time, the virtual neutral point EN is shown as a stable virtual neutral point voltage because the virtual neutral point circuit 101 always derives a voltage that is % of the output voltage of the rectifier circuit. Then, the winding voltages of each phase of the stator winding S are defined as phase voltage (2), ZD4. The Zener voltages v2 of ZD5 and ZD6) are clamped to a constant value, and output voltages of approximately rectangular waves are sent out. At this time, the load on the motor increases and the ripples superimposed on the rectified and smoothed output increase, causing unbalance in the winding voltage of each phase of the stator winding S, and the peak value of the phase voltage of each phase 1 Even if unbalance occurs, a phase voltage having a stable peak value is always outputted from each clamp device (output of the tooth diagram 702).

Each phase shifter of the phase shift circuit 103 receives the output of each clamper of the voltage clamp circuit 102, and converts the input voltage into a substantially triangular wave voltage with a phase lag of O0 using a resistor and a capacitor, and converts the input voltage to a substantially triangular waveform voltage with a phase delay of O0, and converts the input voltage to a substantially triangular waveform voltage with a phase delay of O0. Output voltages that alternate between positive and negative around the center are sent out as output signals U, ■□, and W□, respectively (
(output of the discrepancy diagram 703).

At this time, the neutral point of the three-phase star-connected voltage clamp circuit 102 and phase shift circuit 103 is connected to the virtual neutral point EN of the virtual neutral point circuit 101, and the virtual neutral point circuit 10/ is connected to the virtual neutral point EN of the virtual neutral point circuit 101. , the impedance is sufficiently low for the power frequency of the AC power supply /, and is set to a sufficiently lower impedance than the leakage impedance of each switching element of the inverter circuit 7 when it is off, so that the leakage impedance of the switching element when it is off is The output of heavy pressure clamping is not affected by induced voltage due to variations in
Since the phase is shifted to a phase lag, the output of each phase shifter becomes a substantially triangular waveform that peaks at the zero-crossing point of the phase voltage ■2. For example, when used in a compressor, the load fluctuates during the rotation of the stator winding S, and the so-called wow and flutter phenomenon occurs, which causes unevenness in the rotational speed during the rotation. This causes a phase imbalance in the winding voltage, causing a difference in the positive and negative charging times for the capacitor of the phase shifter, and a waveform that is DC-shifted with respect to the virtual neutral point EN is output from the phase shifter. Even if it is output, the phase voltage ■
The inflection point at the peak corresponding to the ρ zero-crossing point is accurately output without change. Then, the output signals U, V0 . The subtraction amplifier section 10S of the comparator circuit 101 which has received the W signal outputs the output signals U, Vo, and W of the phase shifter, and the output signals U, Vo, and W.
Output signal U8.Vo, W□ is delayed by a time period determined by its CR time constant by a delay circuit. V2. W2(
That is, the output signal U, V0. The output signal obtained by slightly delaying W□ by the phase ψ, (2l) (point a in Fig. 103), is subtracted by (U, -U), respectively.
2°V, -V2. W□-W2), the waveform becomes the phase voltage ■, as shown by the input difference of A in Figure 103.
.

By alternating positive and negative at the zero-crossing point delayed by the phase ψ with respect to the zero-crossing point of
(The output signal U3.■3.W3, which is a rectangular wave with a phase difference of S'00 and alternates between positive and negative, is delayed by the phase ψ and is sent out from the output terminals of operational amplifiers A and A2 and A3, respectively. 10S output).This output signal U3.■3.
The integral part IO B which received W3 outputs the input signal U3' ■31
The output signal U4.W3 is integrated with a phase delay of 00 and has a substantially triangular waveform alternating between positive and negative. V4. Sends W4 respectively (output shown in Figure 10B). At this time, the integrating section 10
B is two resistors (R2, and R22゜R and R, R and R)
and capacitor C02゜23 24 2
5 26C□3. Input signal U3 by C□4
．． ■3. Integrate each W3 and output the output signal ■4. ■
4IW4 is formed so as to be sent out from the mutual connection point (output end) of two resistors (22), and the two resistors are R2□=R23=R25>>R22=R
24-R26, so when the polarity of the input signal "" 31 w3 is reversed, the voltage at the output terminal is the same as that of the input signal U3. ■3. Voltage after polarity reversal of W3 VV u3' v3 ” w3 and capacitor c12 ”
Charging voltage just before polarity reversal of the above input signal of 131C□4■
. , 2vo engineering 3. vc engineering. The output waveform (Fig. 1) changes sharply in the direction of zero voltage by the difference between
0), so the output signal U of the integrating section 10
4. V4. The zero crossing point of the output waveform of W4 is the output signal U3. Just use v31w3O0
It is slightly on the leading side (that is, leading by the phase shift ψ) from the zero-crossing point of the output waveform when integrated into the phase lag. That is, the phase shift ψ with respect to the phase voltage ■ is corrected. As a result, the integrator IOB receives the input signal from the phase voltage V,
Even if the signal has a phase difference of 1lr00 and is delayed by the phase ψ, the zero-crossing point of its output waveform can be obtained with a phase difference of 2700 with respect to the zero-crossing point of the phase voltage vF. Comparator CPU of comparison unit 107 receives this.

CPv and CPw block and input the DC component through AC coupling by the capacitor and resistor (C05 and R27, C□6 and R28, C and R29) provided at the inverting input terminal, and The output signal U is a rectangular wave related to the duty ratio SO, which is compared and inverted with the input (virtual neutral point voltage) of the non-inverting input terminal, and has a phase delay of 0° with respect to the phase voltage V-. ,
■o, Wo as comparator CP u + CP y +02w
The position detection circuit 100 outputs the signals from the output terminals of the rotor A with a phase difference of 7200 degrees from each other, and the position detection circuit 100 receives the position detection signal U of the rotor A. * Vo * Wo are sent to the distribution circuit l/, respectively.

In the above position detection operation, if the period of the output frequency of the inverter circuit 7 is T, and the delay time of the delay circuit of the subtraction amplifier 10S is td, when the above output frequency is low (that is, when the rotation speed of the electric motor J is low), , since the period T is long and the delay time t (1 is constant), the phase shift ψ determined by 2·td −×2π is extremely small with respect to the period T, and in this case, the subtraction amplification unit l.

The output of the integrating section 10B which receives the output of 3 becomes longer in integration time, and the amplitude of the output waveform which alternates between positive and negative in a substantially triangular waveform becomes large, and the voltage suddenly changes when the polarity is reversed with respect to this amplitude. The ratio of the integrating section 101. When the zero-crossing point in the output waveform of is corrected to a smaller value on the advancing side, and when the output frequency becomes higher (that is, when the rotational speed of the electric motor I becomes higher), the period T becomes shorter, and the above relational expression 2 As can be understood from % □ × 2π, the phase delay ψ becomes sharper, but the output of the integrating section 10B that receives this becomes shorter in integration time, and the amplitude of the alternating output waveform is approximately triangular. The voltage becomes smaller and suddenly changes when the polarity reverses for this amplitude■. The ratio becomes large, and the zero-crossing point in the output waveform of the integrating section 10B is greatly corrected to the advancing side.

In other words, the zero-crossing point of the output waveform of the integrating section 10B is corrected to the leading side according to the magnitude of the phase shift ψ that changes according to the output frequency (that is, according to the rotational speed), and the phase voltage ■
A signal at the zero-crossing point having a phase difference of 27oO(25) with respect to the zero-crossing point of signals can be obtained accurately. This means that the position of the rotor B can be accurately detected without interfering with the operation of the electric motor I even when the rotation of the electric motor ranges from a low speed to a high speed range.

Furthermore, the electric motor l is used for the compressor and the load is 7.
The so-called wow and flutter phenomenon occurs, in which the rotational speed varies during rotation and unevenness occurs during one rotation, resulting in an unbalanced phase of the winding voltage of each phase of the stator winding 5, and each phase shifter of the phase shift circuit 103 When a deviation occurs in the integration time in both the positive and negative polarity directions, the bypass resistors R9 and R. , R operation □ to suppress the accumulation of charge that causes a direct current shift, and output signals U□, ■□, W□ of each phase shifter to the subtraction amplifier 10! ; Since the comparison is made by AC coupling via the integrating section IO B, the comparison signal U. IVQ
By preventing the phase shift of IWo, it is possible to accurately obtain a position detection signal with a phase delay of 00 (26) with respect to the phase voltage ■1.

In the above embodiment, the comparator circuit 1011 of the position detection circuit 100 outputs an output signal U3 '■3 + alternating with a rectangular wave having a phase difference of /1r00 delayed by the phase ψ with respect to the phase voltage ■ by the subtraction amplifier 10S. It has been explained that W3 is obtained and compared with the virtual neutral point voltage via the integrating section 10A to obtain a position detection signal with a phase delay of OO with respect to the phase voltage VF. As shown in the figure, an operational amplifier A is connected to the output terminal of each phase shifter of the phase shift circuit 103.
A2. Connect the non-inverting input terminal of A3, and connect the inverting input terminal through a delay circuit consisting of a resistor and a capacitor (R, and 09. R□6 and C, R□ヮ and C,). , operational amplifier A.

A2. Feedback resistor R□ between the inverting input terminal and output terminal of A3
8. Insert R engineering 91 and R20 respectively, subtract the outputs U□, Vo, W□ of each of the above phase shifters by the output delayed by the phase ψ via the delay circuit, and amplify this with a large amplification degree. A subtractive amplifier 10S' which sends out alternating output signals U3' and (3'9w4') with rectangular waves having the same phase difference with respect to the phase voltage (1) with a delay of a slight phase ψ, and the same as described above. The formed integral part IO B and
A comparator CPU at each output of this.

V that connects the non-inverting input terminals of CP and CP, respectively.
Along with W, the inverting input terminals of the comparators CPu, CPv, and CPw are connected to resistors and capacitors (R3o and C, , R3□ and C
91 R32 and C2o) are connected through low-pass filters, and the output U4 of the integration section lOB is
．． V4. A signal U is obtained by comparing W4 with the output obtained by averaging it using a low-pass filter. ,V. A comparator circuit 101' consisting of a comparator section/07' configured to send out a voltage of Corrected by a low-pass filter, O0 for the phase voltage vF
Comparison signal U with phase delay. .

(2) o and Wo may be sent as position detection signals.

According to the present invention, the position of the rotor is detected by forming a signal having the same phase or a 1lr00 phase difference with respect to the phase voltage with a slight phase shift, and this signal is 00 phase delayed with respect to the phase voltage. Since the position detection signal is obtained by comparison detection using the integrated output, even if the switching elements of the inverter circuit are switched due to the pulse width adjustment, the rotor is accurately detected without being affected by this. can detect the position of Moreover, outputs having the same phase or a 1g00 phase difference are obtained by providing a virtual neutral point circuit with low impedance at the output end of the rectifier circuit that rectifies and smoothes the commercial AC power source, and outputs the output with the same phase or 1g00 phase difference. A star-wired voltage clamp circuit of a clamper is connected to each phase of the star-wired stator winding, and a phase shifter connected to the output end of the clamper is star-wired. Each of the above transfers connects the neutral point with the phase shift circuit and grounds the circuit to stabilize the neutral point voltage and prevent the superposition of induced components due to variations in leakage impedance when the switching element is turned off. The output of the phase converter is slightly slower than the phase of this phase.The above slight phase delay can be easily corrected by integrating the two resistors and the capacitor (29) to obtain a position detection signal with a phase delay of OO relative to the phase voltage. It is possible to accurately detect the position of the rotor in all motor speed ranges, from low speed to high speed, without the need for special correction means, and even in cases where the switching element is switched by pulse width modulation. O

[Brief explanation of the drawing]

Figure 2 is a block diagram showing the conventional example, Figure 2 is Figure θ)
Voltage waveform diagrams for each part to explain the operation.
/ indicates the case of overload. Figure 3 is a block diagram showing an embodiment of the present invention, Figure 1 is a voltage waveform diagram of each part explaining the operation of Figure 3, and Figure S is a block diagram showing another embodiment of the comparison circuit of Figure 3. It is. l: Commercial AC power supply, 2: Rectifier circuit, G: Brushless DC motor, S: Stator winding, O: Rotor, 7: Inverter circuit, lOO: Position detection circuit, 10/: Virtual neutral point circuit, ( 30) 102: Voltage clamp circuit, 103: Phase shift circuit, 7
0g, ioa': Comparison circuit, 103, IO! ;': Subtraction amplification section, 10B: Integration section,
107.107': Comparison Department, Patent Applicant Aichi Electric Works Co., Ltd. ICH Emerson Electric Co., Ltd. (31) Fan 1 Figure 81011

Claims (1)

[Claims] A brushless DC motor consisting of a star-connected stator winding and a rotor, and a plurality of switching elements connected to a commercial AC power source in a bridge configuration via a rectifier circuit, the output end of which is connected as described above. The rotor position is detected from an inverter circuit connected to each phase of the stator winding and the winding voltage of the stator winding, and a position detection signal is sent to timely conduct or interrupt the switching element. and a position detection circuit which sequentially energizes each phase of the stator winding, the position detection circuit has two capacitors connected in series to the output end of the rectifier circuit, A virtual neutral point circuit in which a resistor is inserted between each, and the connection point between the capacitors is used as a virtual neutral point to ground the circuit;
A voltage clamp circuit that connects a clamp device consisting of a resistor connected to each phase of the stator winding and a pair of voltage regulator diodes in a star shape and connects the neutral point to the virtual neutral point (1) above; Voltage clamp - A phase shift circuit consisting of a resistor and a capacitor connected to the output end of each clamper of one path is connected in a star shape, and the neutral point is connected to the above virtual neutral point. A subtracting amplifier consisting of an operational amplifier that subtracts and amplifies the output of the phase shifter and an output whose phase is slightly delayed through a delay circuit and outputs the output terminal of each phase shifter of the phase shift circuit. Department and
The output of this is connected to two cells (consisting of resistors and capacitors)
A comparator circuit is provided, which consists of an integrator output from the connecting point of two resistors, and a comparator circuit that sends out a signal that compares the output with the virtual neutral point voltage. A rotor position detection device for a brushless DC motor, characterized in that a position detection signal is obtained from a signal having the same phase as a phase voltage or a signal having a phase difference of 1 lrOO.