JPH0759384A - Inverter - Google Patents

Abstract

PURPOSE:To protect a brushless motor by detecting a short of a switching element of a switching circuit of an inverter. CONSTITUTION:A control circuit 17 is installed which compares terminal voltages Vu-Vw of a brushless motor 15 with a reference voltage and obtains basic wave signals Vu'-Vw' and then outputs conduction signals Up-Wn to on/off control transistors 7-12 of a three-phase bridge circuit 13 based on the basic wave signals Vu'-Vw'. When overcurrent appears in the three-phase bridge circuit 13, an overcurrent protection circuit 32 starts up, turning all the transistors 7-12 OFF. After that, when either of the negative-side transistors 8, 10, 12 or either of the positive-side transistors 7, 9, 11 is shorted, a negative- side or a positive side short detecting circuit 54 or 55 starts detection and then turns all the negative-side transistors 8, 10, 12 or all the positive-side transistors 7, 9, 11 ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device having a switching circuit for sequentially energizing each winding of a brushless motor having a plurality of windings at commutation timing corresponding to a predetermined rotational position of a rotor.

[0002]

2. Description of the Related Art In recent years, in air conditioners and refrigerators, brushless motors, which are a kind of DC motors, have been adopted to drive compressors in order to vary the capacity of the compressors and save power consumption. .
In the case of a brushless motor, the rotational position signal of the rotor is usually required to determine the energized phase of the winding, but it may be difficult to arrange the position detection sensor depending on the usage environment of the motor. Therefore, the inventors of the present application developed a technique for obtaining a rotational position signal by detecting an induced voltage in a motor winding and electrically processing the induced voltage, and applied for this as Japanese Patent Application No. 62-162654. .

Hereinafter, the case where the invention of this application is implemented by a pulse width modulation (hereinafter, simply PWM) system will be described as an example, and this will be described as a conventional technique with reference to FIGS. In the inverter device shown in FIG. 4, the DC power supply circuit 2 connected to the AC power supply 1 is composed of a full-wave rectifier circuit 3, a reactor 4a and a smoothing capacitor 4b, and its positive and negative terminals are on the negative terminal side. It is connected to the positive side DC power supply line 5 and the negative side DC power supply line 6 via the current detection resistor 31.
A switching element, for example, a three-phase bridge circuit 13 including switching transistors 7 to 12 is connected as a switching circuit between the positive side DC power supply line 5 and the negative side DC power supply line 6, and its output terminals 14u, 14v, 14w.
A plurality of phases of the brushless motor 15 such as three-phase windings 1
5u, 15v, 15w are connected.

In this three-phase bridge circuit 13, the three transistors 7, 9, 11 connected between the positive side DC power supply line 5 and the output terminals 14u, 14v, 14w correspond to the positive side switching elements, The three transistors 8, 10, 12 connected between the negative side DC power supply line 6 and the output terminals 14u, 14v, 14w correspond to negative side switching elements, and these transistors 7 to 12 are arranged in a predetermined order. When the on / off control is performed, the brushless motor 15 is rotationally driven by sequentially and continuously energizing the windings 15u to 15w with a phase difference of 120 degrees (electrical angle, the same applies below). In this case, one transistor is 120
Is controlled by the ON / OFF cycle of ON and 240 degrees OFF, and the duty is controlled by the PWM signal P1 shown in FIG. 6 in the ON cycle.
5 terminal voltages Vu, Vv, Vw of each winding 15u to 15w
Has the waveform shown in FIG.

FIG. 5 shows waveforms of the terminal voltage Vu and the current Iu of the winding 15u when the PWM control is not performed. In this waveform, the sloped portion over a section of about 60 degrees (period Ta) is the induced voltage in the winding, and the elongated positive and negative pulses are due to the freewheel diodes D1 to D6 connected in parallel with the respective transistors of the three-phase bridge circuit 13. The pulse voltage, or V0, is a reference voltage formed by the resistance voltage dividing circuit 16 connected between the DC power supply lines 5 and 6. From FIG. 5, it is understood that the commutation timing is delayed by about 30 degrees from the time when the induced voltage crosses the reference voltage V0.

The terminal voltages Vu, Vv, Vw are compared with the comparators 18 to 2 provided in the control circuit 17 as a control means.
0 is compared with the reference voltage V0 to obtain one of the terminal voltages Vu, Vv, Vw as shown in FIG.
Fundamental wave signals Vu ', Vv', Vw 'for 80-degree section recognition
Is converted to. Furthermore, these fundamental wave signals Vu ′, Vv
′ And Vw ′ are given to the waveform synthesizing circuit 21 provided in the control circuit 17, and here, by comparison with the PWM signal P1, a continuous square wave having a time width of 180 degrees is formed from only the positive pulse component and 120 The rotational position signals Ua, Va, Wa having a phase difference of degrees are converted. That is, the control circuit 1
7 also has a function as a rotor rotational position detecting means.

Further, in the waveform synthesizing circuit 21, of the first and second timer functions held therein, the first
With the timer function of, the three rotational position signals U
Six first phase division patterns X1 to X6 each having a time width of 60 degrees are formed from a, Va and Wa, and the first phase division patterns X1 to X6 are formed by the second timer function.
The time width starting from the end point of 6 is 30 degrees each (Ta / 2)
6 second phase division patterns Y1 to Y6 are formed. Then, the waveform synthesizing circuit 21 finally conducts the energizing signals Up, Un, Vp, Vn, Wp, Wn from the above-described first and second phase division patterns as shown in FIG.
To synthesize. These energization signals Up, Un, Vp, V
The phase patterns of n, Wp, and Wn are three-phase bridge circuit 13
The commutation timing pattern required for the transistors 7 to 12 of FIG.

On the other hand, the speed judgment circuit 22 judges the speed deviation from the speed command signal Sc and the energization signal Wn given as the rotation speed detection signal of the brushless motor 15 from the waveform synthesizing circuit 21, and corresponds to the speed deviation. Speed deviation signal S
It outputs d and supplies it to the pulse width modulation circuit 23.
The pulse width modulation circuit 23 controls the duty of the PWM signal P1 according to the magnitude of the speed deviation signal Sd.

PWM from the pulse width modulation circuit 23
The signal P1 is supplied to the waveform synthesizing circuit 21 and acts as an enable signal at the time of waveform synthesizing.

Further, the current detection signal S1 of the current detection resistor 31
Are applied to the overcurrent protection circuit 32. The overcurrent protection circuit 32 always keeps the output signal E1 at a high level and keeps the output signal E1 at which the current detection signal S1 is equal to or higher than a set value at a low level. Then, the output signal E1 from the overcurrent protection circuit 32 and the energization signals Up, Un, Vp, from the waveform synthesis circuit 21.
Vn, Wp and Wn are given to the input terminals of AND circuits 34, 35, 36, 37, 38 and 39 which form the gate circuit 33, and the PWM signal P1 from the pulse width modulation circuit 23 is further applied to the AND circuits 34 and 36. , 38 input terminals. Therefore, when the overcurrent protection circuit 32 detects an overcurrent, the output signal E1 becomes low level and the energization signals Up to Wn are cut off (stopped) by the AND circuits 34 to 39.

Now, the output signal E1 of the overcurrent protection circuit 32
Is high level, duty controlled PWM
The signal P1 is combined with the energization signals Up, Vp, Wp by the AND circuits 34, 36, 38, that is, ANDed, that is, the driving units 25, 27, such as the photocoupler of the post-driving circuit 24.
It is supplied as a base signal as an input signal to the bases of the positive side transistors 7, 9, 11 of the three-phase bridge circuit 13 via 29, and these are on / off controlled in the PWM mode, and the negative side transistors 8, 10, 12 are also supplied. Only the energization signals Un, Vn, Wn are supplied to the base of the drive circuit via drive units 26, 28, 30 such as photocouplers, and these are on / off controlled without PWM mode.
As a result, the brushless motor 15 continues to be driven and its rotation speed is controlled by duty control.

[0012]

In the above conventional structure, when a metal piece enters the three-phase bridge circuit 13,
When one or a plurality of transistors are short-circuited in an abnormal state when one of the transistors 7 to 12 is thermally destroyed or an abnormality occurs in any of the drive units 25 to 30 of the drive circuit 24, the brushless motor 15 A current flows through the windings 15u to 15w by using the induced voltage of as a power source.

The states of the three-phase bridge circuit 13 when one or a plurality of transistors are in a short circuit abnormal state can be 2 6 or 64 states. Considering the current flow path, There are 3 ways.

(1) First pattern In the case where one of the positive side transistors 7, 9, 11 or one of the negative side transistors 8, 10, 12 is in a short circuit abnormal state.

(2) Second pattern In the case where two of the positive side transistors 7, 9, 11 or two of the negative side transistors 8, 10, 12 are in a short circuit abnormal state.

(3) Third pattern In the case where all of the positive side transistors 7, 9, 11 or all of the negative side transistors 8, 10, 12 are in a short circuit abnormal state.

7 to 9 are partial circuit diagrams showing the three-phase bridge circuit 13 and the brushless motor 15 taken out.

FIG. 7 shows an example of the first pattern, in which the negative side transistor 12 is in a short circuit abnormal state (the other transistors 7 to 11 are off). In this state, the current flows as shown by the arrows, and each winding 15u, 15v, 15w
A current will flow in one direction, and each winding 15u,
The waveforms of the currents Iu, Iv, and Iw of 15v and 15w are shown in FIG.
As shown in.

FIG. 8 shows an example of the second pattern, in which the negative side transistors 10 and 12 are in the abnormal short circuit state (the other transistors 7 to 9 and 11 are off). In this state, the current flows as shown by the arrow, the current flows in the winding 15u in one direction, and the current flows in both the positive and negative directions in the windings 15v and 15w. The waveforms of the currents Iu, Iv, and Iw are as shown in FIG.

FIG. 9 shows an example of the third pattern, in which all of the negative side transistors 8, 10, 12 are in a short circuit abnormal state (other transistors 7, 9, 11 are off).
In this state, the current flows as shown by the arrow and each winding 1
5u, 15v, 15w current flows in both positive and negative directions, and the current Iu of each winding 15u, 15v, 15w,
The waveforms of Iv and Iw are as shown in FIG.

10 to 12 are current waveform diagrams by simulation when short-circuit abnormal states of respective patterns occur while the brushless motor 15 is rotating at the same number of revolutions.

As is apparent from this, when the abnormal short circuit condition such as the first and second patterns as shown in FIGS. 10 and 11, occurs, the third pattern as shown in FIG.
Compared to the case where a short circuit abnormal condition like the pattern of
A large current may cause demagnetization of the permanent magnet of the rotor of the brushless motor 15. When the permanent magnet of the rotor of the brushless motor 15 is demagnetized, the rotation speed of the brushless motor 15 does not reach the set value, or the flowing current becomes large, which is fatal to the brushless motor 15. A problem occurs.

The present invention has been made in view of the above circumstances, and an object thereof is to use an induced voltage as a power source when a short circuit abnormality occurs in a switching element of a switching circuit for energizing a winding of a brushless motor. It is an object of the present invention to provide an inverter device capable of suppressing the current flowing in a winding as much as possible.

[0024]

According to another aspect of the present invention, an inverter device has a switching circuit having a plurality of switching elements for sequentially energizing windings of a plurality of phases included in a brushless motor, and a control for forming an energization signal. Means, a drive circuit for ON / OFF controlling the switching element in accordance with an energization signal from the control means, and a short circuit detecting means for detecting ON / OFF of the switching element by detecting a short circuit abnormality of the switching element. Have.

According to another aspect of the present invention, an inverter device includes a plurality of positive side switching elements connected between a positive side DC power supply line and an output terminal for sequentially energizing windings of a plurality of phases included in a brushless motor. A switching circuit including a plurality of negative side switching elements connected between the negative side DC power supply line and the output terminal, a rotor rotational position detecting means for detecting the rotational position of the rotor of the brushless motor, and the rotor rotational position. Control means for obtaining an energization signal corresponding to a predetermined commutation timing based on the rotational position signal from the detection means, a drive circuit for turning on / off the switching element according to the energization signal from the control means, and a flow for the switching circuit An overcurrent protection circuit that detects overcurrent and turns off all of the switching elements, and a short circuit of the switching elements Normally detect and characterized by the structure comprising a short circuit detecting means for on-off controlling the switching element.

In this case, when the current flowing in the switching circuit after the operation of the overcurrent protection circuit becomes a predetermined value larger than the set value of the overcurrent protection circuit or more, all of the positive side switching elements are arranged. Alternatively, it may be configured to turn on all of the negative side switching elements (claim 3).

[0027]

According to the inverter device of the present invention, when the short circuit detecting means detects a short circuit abnormality of the switching element of the switching circuit, the short circuit detecting means turns the switching element on and off separately from the on / off control by the control means. Since the control is performed, the current flowing through the winding of the brushless motor is suppressed as much as possible.

According to the inverter device of the second aspect,
When an overcurrent flows through the switching circuit, that is, the brushless motor, the overcurrent protection circuit detects it and turns off all the switching elements of the switching circuit.
Therefore, it is possible to perform overcurrent protection, but in this case, if a short-circuit fault occurs in the switching element of the switching circuit, a large current is generated in the switching element, that is, the winding of the brushless motor, using the induced voltage as a power source. Since the current flows, the short-circuit detection means controls the switching element on / off when detecting a short-circuit abnormality of the switching element, and suppresses the current flowing through the winding of the brushless motor as much as possible.

According to the inverter device of the third aspect,
The short-circuit detection means determines that the switching element is short-circuited abnormally when the current flowing through the switching circuit after the operation of the over-current protection circuit becomes a predetermined value larger than the set value of the over-current protection circuit. When it is determined, specifically, all the positive side switching elements or all the negative side switching elements are turned on.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
In this embodiment, the same parts as those in the conventional example shown in FIGS. 4 to 12 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

As shown in FIG. 1, a current detecting resistor 40 similar to the current detecting resistor 31 is interposed between one terminal of the smoothing capacitor 4b of the DC power source circuit 2 and the positive side DC power source line 5. And smoothing capacitor 4b and current detection resistor 4
The positive connection line 5a is connected to the common connection point with 0, and the negative connection line 6b is connected to the common connection point between the smoothing capacitor 4b and the current detection resistor 31. Then, in the switching circuit 13, the free wheel diode D
1, freewheel diode 4 in place of D3 and D5
Each of the anodes 1, 43 and 45 is connected to the emitters of the transistors 7, 9 and 11 and each cathode is connected to the positive side connecting line 5a, and a freewheel diode 42 which replaces the freewheel diodes D2, D4 and D6. , 44 and 46 are connected to the collectors of the transistors 8, 10 and 12 and their anodes are connected to the negative side connecting line 6a.

The gate circuit 47 interposed between the gate circuit 33 and the drive circuit 24 is composed of six OR circuits 48 to 53, and AND circuits 34 to 39 are provided at one input terminal of each of the OR circuits 48 to 53. The output signals of the OR circuits 48 to 53 are supplied to the drive units 25 to 30.

Negative-side short-circuit detection circuit 54 as short-circuit detection means
Inputs the current detection signal S1 of the current detection resistor 31 and always keeps the output signal E2 at a low level.
When the current detection signal S1 becomes equal to or more than a predetermined value larger than the set value of the overcurrent protection circuit 32, the output signal E2 is set to the high level. The output signal E2 of the negative side short circuit detection circuit 54 is the OR circuit 4 of the gate circuit 47.
It is adapted to be applied to the other input terminals of 9, 51 and 53. The positive-side short-circuit detection circuit 55, which is a short-circuit detection means, receives the current detection signal S2 of the current detection resistor 40 and always keeps the output signal E3 at a low level, and the current detection signal S2 causes the over-current protection circuit 32. The output signal E3 is set to a high level when the output signal E3 is equal to or more than a predetermined value which is larger than the set value. The output signal E3 of the positive side short circuit detecting circuit 55 is applied to the other input terminal of each of the OR circuits 48, 50 and 52 of the gate circuit 47.

Next, the operation of this embodiment will be described with reference to FIGS. 2 and 3. Time T1 in FIG. 2 and FIG.
In the normal state before the time T4, the current detection signals S1 and S2 of the current detection resistors 31 and 40 are smaller than the set value Ra of the overcurrent protection circuit 32, and, of course, larger than this set value Ra. It is smaller than the predetermined value Rb of the negative side short circuit detection circuit 31 and the positive side short circuit detection circuit 40. Therefore, the output signal E1 of the overcurrent protection circuit 32 becomes high level,
The output signals E2 and E3 of the negative side short circuit detection circuit 54 and the positive side short circuit detection circuit 55 are at low level. As a result, the signals from the gate circuits 34 to 39 are transferred to the OR circuit 48 to
It is given to the drive units 25 to 30 via 53,
The three-phase bridge circuit 13 operates normally as in the conventional case.

Now, consider a case where a short circuit abnormality occurs in the negative side transistor 10 at time T1 in the state of FIG. At time T1, the positive side transistor 9 is turned on, so that both the transistors 9 and 10 are turned on, the DC power supply circuit 2 is short-circuited, and the currents flowing through the positive and negative DC power supply lines 5 and 6 are rapidly increased. To do. Therefore, the current detection signals S1 and S2 of the current detection resistors 31 and 40 also rapidly increase. When the current detection signal S1 becomes equal to or higher than the set value Ra (time T2), the overcurrent protection circuit 3
2 operates so as to change the output signal E1 from the high level to the low level, all the output signals of the AND circuits 34 to 39 become the low level, and the base signals are not given to the transistors 7 to 12.

Thus, the transistors 7-9 and 1
Although the transistors 1 and 12 are turned off, the transistor 10 is in the on state even if the short circuit abnormality occurs and the base signal is not given. Therefore, the induced voltage of the brushless motor 15 is used as the power source, the winding 15v, the transistor 10, Current detection resistor 3
1, path of free wheel diode 42 and winding 15u, winding 15v, transistor 10, current detection resistor 3
1, a large current flows through the path of the freewheel diode 46 and the winding 15w, and the current detection signal S1 of the current detection resistor 31 rapidly increases again. Then, when the current detection signal S1 becomes equal to or higher than the predetermined value Rb (time T3), the negative side short-circuit detection circuit 54 determines that the short-circuit abnormality of the negative side transistor has occurred, and switches the output signal E2 from low level to high level.

The high-level output signal E2 from the negative side short-circuit detection circuit 54 is supplied to the drive units 26, 28 and 30 via the OR circuits 49, 51 and 53, so that the drive units 26, 28 and 30 is a negative side transistor 8,
The base signal is continuously supplied to 10 and 12, and the negative side transistors 8, 10 and 12 are all turned on. In this state, the currents flowing through the windings 15u, 15v, and 15w flow in both positive and negative directions in the same manner as the state shown in FIG. 12, and thus are suppressed to a minimum.

On the other hand, consider the case where a short circuit abnormality occurs in the positive side transistor 9 at time T4 in the state of FIG. At time T4, the negative side transistor 10 is turned on, so that both the transistors 9 and 10 are turned on, the DC power supply circuit 2 is short-circuited, and the currents flowing through the positive and negative DC power supply lines 5 and 6 are rapidly increased. To do. Therefore, the current detection signals S1 and S2 of the current detection resistors 31 and 40 also rapidly increase. When the current detection signal S1 becomes equal to or higher than the set value Ra (time T5), the overcurrent protection circuit 3
2 operates so as to change the output signal E1 from the high level to the low level, all the output signals of the AND circuits 34 to 39 become the low level, and the base signals are not given to the transistors 7 to 12.

As a result, the transistors 7, 8 and 10 are
12 to 12 are turned off, but the transistor 9 is in the on state even if the short circuit abnormality occurs and the base signal is not applied. Therefore, the induced voltage of the brushless motor 15 is used as the power source, and the winding 15u and the free wheel diode 41 are used. , A large current flows through the path of the current detection resistor 40, the transistor 9 and the winding 15v and the path of the winding 15w, the freewheel diode 45, the current detection resistor 40, the transistor 9 and the winding 15v, The current detection signal S2 rapidly increases again. Then, the current detection signal S
When 2 becomes equal to or greater than the predetermined value Rb (time T6), the positive side short circuit detection circuit 55 determines that the short circuit of the positive side transistor is abnormal, and switches the output signal E3 from low level to high level.

Since the high-level output signal E3 from the positive side short circuit detection circuit 55 is supplied to the drive units 25, 27 and 29 via the OR circuits 48, 50 and 52,
The drive units 25, 27 and 29 continuously apply the base signal to the positive side transistors 7, 9 and 11, and all the positive side transistors 7, 9 and 11 are turned on. In this state, the currents flowing through the windings 15u, 15v, and 15w flow in both positive and negative directions in the same manner as the state shown in FIG. 12, and thus are suppressed to a minimum.

In the above, the case where the negative side transistor 10 or the positive side transistor 9 has a short circuit abnormality is described. However, another negative side transistor 8 or 12 or another positive side transistor 7 or 11 is used. When a short circuit abnormality occurs, the negative side transistors 8, 10 and 1
Two of the two or positive side transistors 7, 9 and 11
Even when two of them have a short circuit abnormality, the negative side short circuit detecting circuit 54 or the positive side short circuit detecting circuit 55 performs the detection operation in the same manner as described above.

As described above, according to the present embodiment, when the current detection signal S1 of the current detection resistor 31 becomes equal to or higher than the set value Ra of the overcurrent protection circuit 32, the overcurrent protection circuit 32 operates and the three-phase circuit operates. Transistors 7-12 of bridge circuit 13
Are all turned off, and thereafter, when the current detection signal S1 of the current detection resistor 31 becomes a predetermined value Rb or more,
The negative-side short-circuit detection circuit 54 judges that one or two of the negative-side transistors 8, 10 and 12 have a short circuit abnormality, and turns on all the negative-side transistors 8, 10 and 12 or detects a current. Current detection signal S2 of resistor 40
Is greater than or equal to a predetermined value Rb, the positive-side short-circuit detection circuit 55 determines that one or two of the positive-side transistors 7, 9 and 11 have a short-circuit abnormality, and the positive-side transistors 7, 9 and All 11 were turned on.

That is, the negative side transistors 8, 10 and 12
When a short circuit abnormality occurs in one or two of the three, or when a short circuit abnormality occurs in one or two of the positive side transistors 7, 9 and 11, the three-phase bridge circuit 1
In the commutation operation of 3, the DC power supply circuit 2 is short-circuited by a period in which the positive side transistor and the corresponding negative side transistor are always turned on at the same time. Therefore, first, the overcurrent protection circuit 32 is The operation of turning off all the transistors 7 to 12 is performed. Then, as described above, when a short circuit abnormality occurs in the transistor of the three-phase bridge circuit 13, the current detection signal S1 or S2 of the current detection resistor 31 or 40 rapidly increases even after that. Therefore, the negative side short circuit detection circuit 5
4 or the positive side short circuit detection circuit 55 performs a detection operation to turn on all the negative side transistors 8, 10 and 12 or all the positive side transistors 7, 9 and 11.

As a result, the induced voltage of the brushless motor 15 can be used as a power source to suppress the current flowing through the windings 15u, 15v, and 15w of the brushless motor 15 so as to minimize the permanent magnet type rotor of the brushless motor 15. It is possible to prevent demagnetization of the magnet, and thus
It is possible to prevent the number of rotations of the brushless motor 15 from rising to the set value or the flowing current from becoming large.

In the above embodiment, the brushless motor 1
Terminal voltages Vu, V of windings 15u, 15v and 15w of 5
Although the rotational position signals Ua, Va and Wa (see FIG. 6) are obtained by comparing v and Vw with the reference voltage V0, for example, a position detecting element such as a Hall element serving as rotor rotational position detecting means is used as the brushless motor 15 May be arranged to obtain the rotational position signal of the rotor, or may be an open loop system in which the control means directly forms the energization signal based on the speed command signal Sc.
The PWM control by the pulse modulation circuit 23 may be performed as needed.

[0046]

As described above, in the inverter device of the present invention, when a short circuit abnormal state occurs in the switching element of the switching circuit for energizing the windings of the brushless motor, this is detected by the short circuit detecting means. Then, since the switching element is controlled to be turned on and off separately from the control means for controlling the switching element to be turned on and off for energizing the winding, the induced voltage of the brushless motor is used as a power source when the short circuit of the switching element is abnormal. The current flowing through the windings can be suppressed as much as possible, and therefore demagnetization of the rotor of the brushless motor can be prevented,
It is possible to prevent the rotation speed of the brushless motor from rising to a set value or prevent a large current from flowing through the winding.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of each part in FIG.

FIG. 3 is a waveform diagram of each part in a state different from that in FIG.

FIG. 4 is a circuit diagram showing a conventional example.

5 is a voltage and current waveform diagram of one winding of the brushless motor shown in FIG.

6 is a waveform diagram of each part of FIG.

FIG. 7 is a partial circuit diagram showing an abnormal state 1

FIG. 8 is a partial circuit diagram showing an abnormal state, part 2

FIG. 9 is a partial circuit diagram showing an abnormal state, part 3

FIG. 10 is a current waveform diagram of each winding in the state of FIG.

FIG. 11 is a current waveform diagram of each winding in FIG.

FIG. 12 is a current waveform diagram of each winding in FIG.

[Explanation of symbols]

2 is a DC power supply circuit, 5 is a positive side DC power supply line, 6 is a negative side DC power supply line, 7, 9 and 11 are positive side transistors (positive side switching elements) 8, 10 and 12 are negative side transistors (negative side switching) Elements), 13 is a three-phase bridge circuit (switching circuit), 14u to 14w are output terminals, 15 is a brushless motor, 15u to 15w are windings, 17 is a control circuit (control means, rotor rotational position detection means), and 22 is Speed determination circuit, 23 is a pulse width modulation circuit, 24 is a drive circuit, 3
2 is an overcurrent protection circuit, 33 and 47 are gate circuits, 54
Is a negative side short circuit detection circuit (short circuit detection means), and 55 is a positive side short circuit detection means (short circuit detection means).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02M 7/5387 9181-5H

Claims (3)

[Claims] 1. A switching circuit having a plurality of switching elements for sequentially energizing windings of a plurality of phases included in a brushless motor, control means for forming an energization signal, and the switching according to the energization signal from the control means. An inverter device comprising: a drive circuit that controls ON / OFF of an element; and a short circuit detection unit that detects a short circuit abnormality of the switching element and controls ON / OFF of the switching element. 2. A plurality of positive side switching elements and a negative side DC power supply line and an output connected between a positive side DC power supply line and an output terminal for sequentially energizing windings of a plurality of phases included in a brushless motor. A switching circuit including a plurality of negative side switching elements connected between the terminals, a rotor rotational position detecting means for detecting the rotational position of the rotor of the brushless motor, and a rotational position signal from the rotor rotational position detecting means. Control means for obtaining an energization signal corresponding to a predetermined commutation timing based on the above, a drive circuit for on / off controlling the switching element according to the energization signal from the control means, and an overcurrent flowing in the switching circuit to detect the overcurrent. An overcurrent protection circuit for turning off all of the switching elements, and a short circuit abnormality of the switching elements is detected to detect the switching Inverter formed by and a short circuit detection means for turning on and off the device. 3. The short-circuit detection means, when the current flowing through the switching circuit after the operation of the overcurrent protection circuit becomes a predetermined value larger than a set value of the overcurrent protection circuit or more, all of the positive side switching elements or The inverter device according to claim 2, wherein the inverter device is configured to turn on all of the negative side switching elements.