JP2003274667A - Power module for three-phase inverter and three-phase motor drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a power module for a three-phase inverter having a winding current detector circuit which can detect information of the winding current of a three-phase motor with a low power loss and a high accuracy. <P>SOLUTION: The power module for the three-phase inverter driven by a PWM signal for driving a sine wave comprises IGBTs 114 to 116 with sensors in the lower arm of a three-phase full-bridge circuit having a main emitter connected to a ground terminal 13, a shunt resistor 14 having a low resistance and connected between the emitter of the sensor and the ground terminal, and two diodes D2, D3 having split anodes to supply currents corresponding to predetermined dividing ratio between a collector and the main emitter and between the collector and the sense emitter of the sensor, thereby processing a voltage generated at the shunt resistor by an amplifier 16 and a splitting ratio compensator 17, thereby detecting the current winding of a three-phase motor 20. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power module for a three-phase inverter and a three-phase motor drive system, and more particularly to a circuit for detecting a winding current of a three-phase motor, which uses a sine wave drive method based on a PWM signal. It is used in an intelligent power module that performs vector control so that the total winding current of a driven three-phase motor becomes constant.

[0002]

2. Description of the Related Art The drive system of a DC brushless motor of a three-phase inverter is shifting from a rectangular wave drive system to a sine wave drive system from the viewpoint of energy saving and noise reduction. In such a sine wave driving method, the motor winding is energized over the entire period in order to generate a sine wave driving current.

Since the DC brushless motor is a synchronous motor, it is necessary to detect the position of the rotor and switch the drive phase. Sensor (for example, Hall element) to detect the position of the rotor of a three-phase motor that uses a sine wave drive system
In the method using, for example, when applied to a three-phase motor for a washing machine, the sine wave is distorted due to the fact that the rotor position is estimated and the sine wave waveform is generated when the torque fluctuation is large or at high speed rotation. , Which caused vibration and sound.

As a method in which no sensor is used to detect the rotor position of a three-phase motor employing the sine wave drive method, the current flowing in the winding is detected so that the total sum of the winding currents becomes constant (motor torque Vector control is used.

In the vector control, it is necessary to detect the winding current in real time with high accuracy, and the detection result is processed by a high speed arithmetic circuit, for example, a DSP (digital signal processor) to generate a sine wave driving PWM signal. There is.

In order to detect the winding current of the three-phase motor in real time with high accuracy, the winding current can be detected by detecting the current flowing in each arm of the power element connected in the three-phase full bridge. it can.

Conventionally, a current transformer often detects a current flowing between a power element connected in a three-phase full bridge and a three-phase motor. However, this current transformer requires a correction circuit associated with magnetic saturation,
There is a problem that it is expensive and the system price rises.

Recently, a low resistance is inserted in the main current path of the lower arm of a three-phase full-bridge connected power element, and the voltage of this resistance (shunt resistance) is read in synchronization with the sine wave driving PWM signal. Circuits used as information on winding current have been put to practical use.

6 and 7 each show a conventional three-phase motor drive system.

In the circuit of FIG. 6, a low-resistance shunt resistor 47 is commonly inserted in the main current paths of the lower arms of the power elements 41 to 46 connected in three-phase full bridge. The circuit of FIG.
Three-phase full-bridge connected power devices 51-56 Individual low resistance shunt resistors 57-59 on the main current line of the lower arm
Have been inserted.

The circuits of FIGS. 6 and 7 can be configured with reference to the ground, the shunt resistors 47, 57 to 59 are cheaper than the current transformer, and the cost of the current detection circuit can be reduced. However, this circuit configuration has a shunt resistor 47,
Since the main current needs to flow in 57 to 59, the power loss becomes large.

[0012]

As described above, in the conventional power module for a three-phase inverter, the voltage is read from the shunt resistance inserted in the main current path of the lower arm of the power element connected to the three-phase full bridge, and the winding is read. The circuit used as current information has a problem of large power loss.

In order to reduce the above power loss, an IGBT (insulated gate bipolar transistor) with a sense terminal is provided on the lower arm of a power element connected in three-phase full bridge.
Can be used. In this case, this sense IGB
If the regenerative current of the diode connected in parallel with T cannot be detected, the winding current detected from the voltage of the shunt resistor will be the current detected during the specific period of the PWM signal for sine wave drive. Information is insufficient as compared with the winding current, and current information necessary and sufficient for vector control is lost.

The present invention has been made to solve the above problems, and is a three-phase inverter having a winding current detection circuit capable of detecting winding current information of a three-phase motor with low power loss and high accuracy. It aims at providing the power module for.

[0015]

A power module for a three-phase inverter according to the present invention comprises three upper phase arms of a three-phase full bridge circuit composed of power switch elements driven by a PWM signal for driving a sine wave. Power IGBT
And a lower arm of the three-phase full bridge circuit, and three sense IGBTs whose emitters are divided into a main emitter and a sense emitter to divide a current at a predetermined shunt ratio, and the upper arm. A power supply terminal commonly connected to each collector of the constituent IGBTs, a ground terminal commonly connected to each main emitter of the sensed IGBT forming the lower arm, and a three-phase output of the three-phase full bridge circuit. Three output terminals for connecting to the windings of the three-phase motor and a first collector for connecting a collector / emitter of the IGBT constituting the upper arm in parallel and supplying a regenerative current.
And a second diode connected in parallel between the collector and the main emitter of the IGBT with a sense, and the anode of which is divided in two so that the current can be shunted at a predetermined shunt ratio. And a shunt resistor for current / voltage conversion, which is connected between the sense emitter of the sensed IGBT forming the lower arm and the ground terminal.

The three-phase motor drive system of the present invention comprises three IGBTs forming the upper arm of a three-phase full bridge circuit composed of power switch elements driven by a PWM signal for driving a sine wave, and the three-phase full drive circuit. Three sense IGBTs, each of which constitutes a lower arm of a bridge circuit, has two main emitters and two sense emitters, each of which has a sense and is capable of shunting a current at a predetermined shunt ratio, and each collector of the IGBTs constituting the upper arm. A power supply terminal commonly connected to each other, a ground terminal commonly connected to each main emitter of the IGBT with a sense that constitutes the lower arm, and a three-phase output of the three-phase full bridge circuit to a winding of a three-phase motor. Output terminals for connecting to the IG and the IG that constitutes the upper arm
A first diode, which is connected in parallel between the collector and the emitter of the BT, allows a regenerative current to flow, and the anode is divided into two so that the current can be shunted at a predetermined shunt ratio. A third diode connected in parallel between the second diode and a collector / sense emitter connected in parallel to the second diode, and a third diode connected in parallel between the collector and the sense emitter, and a sense emitter of the IGBT with a sense that constitutes the lower arm, and the ground terminal. A shunt resistor for current / voltage conversion, an amplifier for amplifying the voltage generated in the shunt resistor, and a regenerative current for the shunt resistor and the third diode depending on the timing of the PWM signal for driving the sine wave. To detect the main current of the IGBT connected to the second diode from the output voltage of the amplifier during A shunt ratio compensating means for compensating the output voltage of the amplifier in proportion to the shunt ratio of the third diode and the second diode; and the shunt ratio compensating means based on the output voltage compensated by the shunt ratio compensating means. It is characterized by comprising an arithmetic circuit for detecting current information of windings of the phase motor, converting the information into a PWM signal for driving the sine wave, and performing vector control of the three-phase motor.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
3 shows an example of a power module for a three-phase inverter according to the embodiment of the present invention and a three-phase motor drive system using the same.

In FIG. 1, 10 is a power module for a three-phase inverter, 20 is a three-phase motor, and 21 is a high-speed arithmetic circuit (eg, DSP).

In the power module 10, the three-phase full-bridge connected power switch elements are respectively I
GBT111-116 are used. In this case, the collectors of the IGBTs 111 to 113 forming the upper arm (high potential side switching element) of the three-phase full bridge circuit are connected to the power supply terminal 12 to which the power supply voltage VD is applied.

Further, IGBTs with sense terminals (sense IGBTs) 114 to 116 as IGBTs constituting the lower arm (low potential side switch element) of the three-phase full bridge circuit.
Is used. In this case, the size (division ratio) of the main current flowing through the main emitter of each sense IGBT and the sense current flowing through the sense emitter is set to, for example, 1000: 1. This is the I of a multi-cell configuration.
It can be easily realized by changing the number of cells constituting the GBT.

The main emitters of the sense IGBTs 114 to 116 are connected to the ground terminal 13, and a shunt resistor 14 having a low resistance value for current / voltage conversion is connected between the sense emitter and the ground terminal 13. . Further, three output terminals 15 for supplying a three-phase output to the winding of the three-phase motor 20 are connected from a connection node of the upper arm and the lower arm of the three-phase full bridge circuit.

Further, an IGBT constituting the upper arm
Between the emitter and collector of 111 to 113, the anode and cathode of the first diode D1 for flowing the regenerative current are connected in parallel.

The sense IGBT constituting the lower arm
A second diode D2 for flowing most of the regenerative current is connected in parallel between the main emitters and collectors of 114 to 116, and a part of the regenerative current is allowed to flow between the sense emitter and collector. Third diode D3 of is connected in parallel.

The second diode D2 and the third diode D3 are set to have a junction area ratio so that a current flows at a predetermined ratio (for example, 10: 1). In the present example, the second diode D2 and the third diode D3 have a multi-cell configuration in which the number of constituent cells is different, and the anode has two anodes that can divert the current at a predetermined diversion ratio (for example, 10: 1).
It is divided and has a common cathode.

Since the shunt resistor 14 has a low resistance value and a voltage drop caused by the flow of a current is minute, an amplifier (A) 16 for amplifying the shunt resistor 14 is provided corresponding to each shunt resistor 14. .

A period (driving current period) in which the motor drive current flows in the path of the output terminal 15 → sense IGBT → shunt resistor 14 → ground terminal 13, and ground terminal 13 → second diode D2
→ route of output terminal 15 and ground terminal 13 → shunt resistor 14
→ Third diode D3 → The period during which the regenerative current flows through the path of the output terminal 15 (regenerative current period) depends on the timing of the PWM signal, and the polarity of the voltage drop of the shunt resistor 14 is reversed during the above two periods.

Therefore, the shunt resistance is applied during the drive current period.
By amplifying and detecting the voltage drop of 14, it is possible to detect a part of the drive current, and it is possible to determine the magnitude of the main current from the ratio of the sense current and the main current. In addition, a part of the regenerative current is detected by amplifying and detecting the voltage drop of the shunt resistor 14 during the regenerative current period, and the magnitude of the regenerative current is determined from the shunt ratio of the third diode D3 and the second diode D2. It becomes possible to ask.

In this case, the shunt resistor 14 is connected between the anode of the third diode D3 and the ground terminal 13, while the anode of the second diode D2 is directly connected to the ground terminal 13.

Therefore, the third diode D3 is different from the second diode D2 in the voltage-current characteristic. Figure 2
Shows a comparison of an example of the voltage-current characteristic of the second diode D2 and the forward voltage (VF) -current (I) characteristic of the third diode D3.

Therefore, in this embodiment, when the regenerative current is obtained from a part of the regenerative current, the shunt ratio of the third diode D3 and the second diode D2 is compensated, and as a shunt ratio compensating means therefor, A diversion ratio compensator 17 is provided for each amplifier 16.

This shunt ratio compensator 17 is known in advance for the input voltage from the amplifier 16 during the regenerative current period (the period during which the regenerative current flows) which is determined based on the polarity of the voltage drop of the shunt resistor 14. The correction is performed according to the correction characteristic.

If the shunt ratio of the third diode D3 to the second diode D2 is too small, the difference in the voltage-current characteristics becomes too large and compensation becomes difficult. Therefore, in this example, the second diode D3 is used. Third diode D3 for D2
Is set to be larger than the shunt ratio (for example, 1/1000) between the collector and the sense emitter with respect to the collector-main emitter of the IGBT with sense.

The high-speed arithmetic circuit (eg DSP) 21 is
Receives the output of the shunt ratio compensator 17, performs signal processing so as to detect the current flowing through the winding with high accuracy, and considers the characteristics of the three-phase motor 20 so that the total winding current becomes constant. A sine wave driving PWM signal for vector control is generated in a cycle of, for example, 50 μs. This sine wave driving PWM signal is supplied via a drive circuit 18 to the six IGBTs 111 to 116 constituting each arm of the three-phase full bridge circuit.

FIG. 3 is a waveform diagram showing the operation of the three-phase motor drive system shown in FIG.

The waveform of the voltage drop of the shunt resistor 14 in the drive current period is in phase with the waveform of the PWM signal for driving the power module in the sine wave, and the waveform of the voltage drop of the shunt resistor 14 in the regenerative current period is in the opposite phase. become. The voltage waveform across the shunt resistor 14 is a combination of the above two waveforms.

The above-described power module for a three-phase inverter and the three-phase motor drive system using the power module divide the regenerative current flowing through the diodes and divide the anode into diodes D2 and D3, and a shunt for current-voltage conversion. A resistor 14, an amplifier 16 for amplifying a minute voltage, and a shunt ratio compensator 17 for compensating the shunt ratio are used. This reduces the power loss due to the shunt resistor 14 and reduces the diode D2, D3
The regenerative current can also be detected with low loss, and the same amount of current information as in the winding current detection using the DC current transformer method can be obtained at low cost with low loss.

It is also possible to detect the overcurrent of the three-phase full bridge circuit from the voltage generated in the shunt resistor 14 and perform the overcurrent protection.

FIG. 4 shows an example of a power module for a three-phase inverter according to a second embodiment of the present invention and a three-phase motor drive system using the same.

In the second embodiment, as compared with the first embodiment, the shunt ratio compensator (17 in FIG. 1) is omitted and the high-speed arithmetic circuit (eg, DSP) 21a has the function thereof. That is, the high-speed arithmetic circuit 21a is different in that it has a shunt ratio compensating means for performing the shunt ratio compensating process by software, and the other parts are the same. Therefore, in FIG. 4, the same parts as those in FIG. The description thereof will be omitted.

FIG. 5 is a flow chart briefly showing an example in which the shunt ratio compensating process is performed by software by the shunt ratio compensating means in the high speed operation circuit 21a in FIG.

When the process is started (start), first, in the regenerative current period determination step, it is determined whether or not the PWM signal is in the off cycle (regenerative current period), and the determination result is
In the case of YES (regenerative current period), the output data of the amplifier 16 is read to detect the voltage drop of the shunt resistor 14. Then, the calculation processing of the shunt ratio compensation is performed, and the result is supplied as calculation processing data for generating a PWM signal for vector control.

Then, it is determined whether or not the system is in operation, and if the determination result is YES (in operation), the process returns to the regenerative current period determination step. In the regenerative current period determination step, if the determination result is NO (driving current period), the process returns to the regenerative current period determination process again. If the result of the determination as to whether the system is operating is NO (not operating), the process ends (end).

Also in the second embodiment, the same effect as that of the first embodiment can be obtained.

[0045]

As described above, according to the present invention, a power module for a three-phase inverter equipped with a winding current detection circuit capable of detecting winding current information of a three-phase motor with low power loss and high accuracy, and A three-phase motor drive system using it can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a power module for a three-phase inverter according to a first embodiment of the present invention and a three-phase motor drive system using the same.

FIG. 2 is a characteristic diagram showing the voltage-current characteristics of a second diode D2 and the voltage-current characteristics of a third diode D3 in comparison.

3 is a waveform diagram showing the operation of the three-phase motor drive system of FIG.

FIG. 4 is a circuit diagram showing an example of a power module for a three-phase inverter according to a second embodiment of the present invention and a three-phase motor drive system using the same.

5 is a flow chart briefly showing an example of a case where the shunt ratio compensation process is performed by software in the high-speed arithmetic circuit in FIG.

FIG. 6 is a structural explanatory view showing an example of a conventional three-phase motor drive system.

FIG. 7 is a structural explanatory view showing another example of a conventional three-phase motor drive system.

[Explanation of symbols]

10 ... Power module for three-phase inverter, 20 ... three-phase motor, 21, 21a ... High-speed arithmetic circuit (eg, DSP), 111-113 ... IGBT (upper arm), 114-116 ... Sense IGBT (lower arm), 12 ... power supply terminal, 13 ... ground terminal, 14 ... shunt resistance, 15 ... Output terminal, D1 ... the first diode, D2 ... second diode, D3 ... third diode, 16 ... amplifier, 17 ... Shunt ratio compensator, 18 ... Drive circuit.

Continued front page    F-term (reference) 5H007 AA06 AA12 AA17 BB06 CA01                       CB05 CC23 DA05 DB12 DC02                       EA02 FA20                 5H576 BB04 DD02 EE01 EE11 GG04                       HA04 HB01 JJ03 KK06 LL14                       LL22                 5H740 AA08 BA11 BA15 BB05 BB09                       BB10 BC06 JA28 MM03 MM11

Claims (6)

[Claims] 1. Three IGBTs constituting an upper arm of a three-phase full bridge circuit composed of power switch elements driven by a PWM signal for driving a sine wave, and a lower arm of the three-phase full bridge circuit are constituted. , I with three senses, each of which is divided into a main emitter and a sense emitter so that the current can be shunted at a predetermined shunt ratio
A power supply terminal commonly connected to each collector of the IGBT constituting the upper arm, a ground terminal commonly connected to each main emitter of the sensed IGBT constituting the lower arm, and the three-phase full The three output terminals for connecting the three-phase output of the bridge circuit to the windings of the three-phase motor and the collector-emitter of the IGBT constituting the upper arm are connected in parallel, and the first terminal for flowing the regenerative current. 1 diode, a second diode connected in parallel between the collector and the main emitter of the sensed IGBT, a collector of the sensed IGBT having a predetermined shunt ratio to the second diode, A third diode connected in parallel between the sense emitters and a sense emitter of the sense IGBT forming the lower arm and the ground terminal. A power module for a three-phase inverter, comprising a continuous shunt resistor for current / voltage conversion. 2. An amplifier for amplifying a voltage generated in the shunt resistor, and a main current flowing in an IGBT connected to the second diode during a period in which a regenerative current flows in the shunt resistor and the third diode. 2. A shunt ratio compensating means for compensating an input voltage from the amplifier in proportion to a shunt ratio of the third diode and the second diode to detect the voltage. The power module for the three-phase inverter described. 3. The shunt ratio compensating means corrects the input voltage during a regenerative current period which is determined based on the polarity of the voltage drop of the shunt resistor.
The power module for the three-phase inverter described. 4. The second diode and the third diode have a multi-cell structure in which the number of constituent cells is different, and the anode is divided into two so as to be able to divert the current at a predetermined diversion ratio. The power module for a three-phase inverter according to any one of claims 1 to 3. 5. The shunt ratio of the third diode to the second diode is larger than the shunt ratio of the collector-sense emitter to the collector-main emitter of the sense IGBT. The power module for a three-phase inverter according to any one of 1 to 4. 6. The three-phase inverter power module according to claim 2, wherein current information of the winding of the three-phase motor is detected based on the output voltage compensated by the shunt ratio compensating means, and the sine wave drive is performed. A three-phase motor drive system, further comprising an arithmetic circuit for converting the PWM signal for use in a vehicle to a vector and controlling the three-phase motor.