JP3396955B2 - DC-AC converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC / AC converter having a bridge circuit including transistors. INDUSTRIAL APPLICABILITY The DC-AC converter of the present invention is applied to, for example, a vehicle charger that rectifies an AC power generation voltage of an automobile alternator (AC generator) to charge a battery.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 45-16651 discloses a three-phase full-wave rectifier using a constant voltage diode instead of a normally used junction diode. JP-A-63-20
Japanese Patent No. 2255 discloses a bridge circuit (inverter / rectifier) which is arranged between a three-phase AC generator motor and a battery and orthogonally transforms electric power transferred between the two (an orthogonal transform in the present specification includes an AC / DC transform). ) Is composed of a MOS transistor and a high voltage (1.5 to 3 times the battery voltage) constant voltage diode connected in parallel with the MOS transistor.

These constant voltage diodes are for clamping and suppressing the G pulse voltage generated between the terminals of the generator when the load of the three-phase full-wave rectifier is cut off. Japanese Laid-Open Patent Publication No. 4-138030 proposes a three-phase full-wave rectifier using a MOS power transistor. On the other hand, an inverter that converts DC power of a battery into three-phase AC power and applies it to an armature winding of a three-phase AC motor is often used using a bipolar transistor or an IGBT. In this case, Usually, a junction diode is connected in parallel with these bipolar transistors or IGBTs and in a direction to rectify the generated voltage.

[0004]

However, in order to suppress the G pulse voltage by the above-mentioned constant voltage diode, the maximum allowable current of the constant voltage diode must be set extremely large, which is a big problem in practical use. . The present invention has been made in view of the above circumstances, and a bridge circuit (inverter or rectifier (rectifier)) that can suppress the G pulse voltage generated between the ends of the rotating electric machine at the time of sudden current change without using a constant voltage diode. Alternatively, it is an object of the present invention to provide a DC-AC converter including an inverter and a rectifier). The DC-AC converter in the present specification means a device having an inverter function of converting DC power into AC power, a rectifier function of converting AC power into DC power, or both of the above functions.

[0005]

A first configuration of a DC-AC converter according to the present invention comprises connecting a required number of phase bridge circuits, each of which includes a high-side element and a low-side element including a transistor connected in series. A pair of direct current terminals are connected to both ends of a battery and a load, and a connection point of both elements is individually connected to each end of an armature winding of an AC rotating electric machine, and the transistor is intermittently controlled. A control unit, wherein the transistor is the AC rotating electric machine.
In the DC-AC converter that performs the operation of rectifying the generated voltage of, the control unit detects an abnormal voltage of the armature winding exceeding a predetermined voltage value, and an abnormal voltage detection circuit unit, When exceeding, all the transistors forming one of the elements are turned on and the other of the elements is turned on.
And a short circuit circuit that cuts off all the transistors that form

According to a second structure of the present invention, in addition to the above-mentioned first structure, the transistor is a P transistor immediately below a gate electrode.
It is characterized in that the parasitic diode between the mold substrate region and the N + type region forming the main electrode is composed of an N-channel MOS transistor formed so as to rectify the generated voltage.

A third structure of the present invention is the same as the first structure, wherein the high-side element or the low-side element is in a direction to rectify a generated voltage with a bipolar transistor or an IGBT.
It is characterized in that it comprises a BT and a junction diode connected in parallel. A fourth configuration of the present invention is characterized in that, in the above-mentioned second configuration, the control unit intermittently causes the MOS transistor to perform DC-AC conversion or AC-DC conversion at predetermined timing. I am trying.

In a fifth configuration of the present invention, in addition to the third configuration, the control section intermittently connects the bipolar transistor or the IGBT at a predetermined timing to apply an AC voltage to the rotating electric machine. Is characterized by. A sixth configuration of the present invention is further characterized in that, in the first configuration, the control unit conducts each of the transistors forming one of the elements at a predetermined average conductivity.

According to a seventh aspect of the present invention, in addition to the above-mentioned first configuration, the short-circuit circuit section is configured to fully conduct the transistor for a predetermined time after the abnormal voltage detection circuit section detects the excess. It is characterized by lasting.
An eighth structure of the present invention is the same as the first structure,
The short circuit portion, after the full conduction of the transistor,
It is characterized in that it is judged whether or not the DC end voltage becomes lower than a predetermined value which is set lower than the battery voltage, and when it does not, the full conduction is maintained.

[0010]

According to the first structure of the present invention,
A transistor that forms at least a part of at least one of a high-side element and a low-side element of a bridge circuit that exchanges electric power by orthogonal conversion between an AC rotating electric machine (AC generator or AC motor or AC generator motor) and a battery is When the pulse voltage (high voltage generated at each end of the armature winding of the AC rotating electric machine) is generated, all are made conductive, so after all,
Each end of the armature winding is short-circuited by this transistor. As a result, the surge power of the AC rotary electric machine that generates the G pulse voltage is consumed by the ON resistance of these transistors, the wiring resistance, the resistance of the armature winding, and the like. The G pulse voltage applied to the load connected in parallel with is greatly suppressed.

Further, even if the breakdown voltage of the high-side element or the low-side element forming the bridge circuit is reduced, the breakdown of these elements can be prevented. Further , since all the transistors which are made conductive and the transistors on the opposite side are all cut off, the battery voltage is not short-circuited due to simultaneous conduction of both elements of the same phase bridge circuit.

According to a second structure of the present invention, in addition to the first structure, a parasitic diode between the P-type substrate region immediately below the gate electrode and the N + -type region forming the main electrode is further provided. N formed to rectify the generated voltage
Since it is composed of channel MOS transistors, this parasitic diode can be used for rectification. According to a third configuration of the present invention, in the above first configuration,
The high-side element or the low-side element is composed of a bipolar transistor or an IGBT and a junction diode connected in parallel with the bipolar transistor or the IGBT so as to rectify the generated voltage. In this case, the surge current due to the G pulse voltage short-circuits the armature winding by a bipolar transistor or IGBT of a predetermined phase and a junction diode of a different phase on the same side as this bipolar transistor or IGBT. G
The pulse voltage can be suppressed without any trouble.

According to the fourth structure of the present invention, in the above-mentioned second structure, the MOS transistor for suppressing the G pulse voltage is also used as a device for an inverter or a rectifier. The addition can be omitted and the configuration becomes simple. According to the fifth configuration of the present invention, in the third configuration, the bipolar transistor for suppressing the G pulse voltage or the IGBT is also used as the element for the inverter, so that the addition of the element to the bridge circuit can be omitted. And the configuration is simple.

According to a sixth aspect of the present invention, in addition to the first configuration, the G pulse voltage suppressing transistor does not become completely conductive when the G pulse voltage is generated, but has a predetermined average conductivity. Since the PWM control is performed as described above, it is possible to prevent heat generation and destruction of these transistors. According to a seventh configuration of the present invention, in the above-mentioned first configuration, the short-circuit circuit section further comprises:
Since the transistor is kept in full conduction for a predetermined time, even if the G pulse voltage is lowered due to a short circuit of the armature winding, the short circuit is maintained until the electromotive voltage generated in the armature winding is attenuated. It is possible to prevent the generation of the G pulse voltage.

According to an eighth aspect of the present invention, further, in the first configuration, the short circuit portion has a DC terminal voltage lower than a predetermined value set lower than the battery voltage after the transistor is fully conducted. Since it is determined whether or not the battery is connected, the full continuity is maintained. Therefore, when the battery connection is restored, it is possible to eliminate the short circuit of the armature winding and recharge the battery. it can.

[0016]

【Example】

(Example 1) Hereinafter, a vehicle AC generator (alternator)
An embodiment of the DC-AC converter of the present invention used in a charging device for charging the battery by rectifying the generated voltage of FIG. 1 will be described with reference to FIG.

Reference numeral 1 denotes a three-phase AC generator for a vehicle, and the output terminals (each terminal) of the armature windings 11 to 13 are AC terminals of a three-phase full-wave rectifier (bridge circuit in the present invention) 3. (Connection points to be described later) 41 to 43, and a pair of DC ends of the three-phase full-wave rectifier 3 are connected to both ends of the battery 7. A load 9 is connected to both ends of the battery 7 via a switch 10.

Reference numeral 2 is a field coil whose one end is connected to the high end of the battery 7, and the other end is connected to the collector of a grounded emitter transistor 51 incorporated in the power generation control circuit section 5. Reference numeral 52 is a flywheel diode, and the power generation control circuit unit 5 has the same configuration as a conventional regulator, and intermittently controls the transistor 51 according to the level of the high-order terminal voltage (B voltage) of the battery 7 to control the field current. The voltage generated by the armature windings 11 to 13 is controlled so that the B voltage becomes a predetermined level. Since this control operation is well known, further explanation is omitted.

The three-phase full-wave rectifier 3 includes high-side devices 31 to 33 composed of junction diodes and an N-channel MOS.
It is composed of low side elements 34 to 36 formed of transistors, and high side elements 31 to 33 and low side elements 34 to
3 sets of phase bridge circuits 3 in which 36 are individually connected in series
7 to 39 are connected in parallel, a pair of direct current terminals are individually connected to the high end and the low end of the battery 7, and each connection point of each element 31 to 36 of each phase bridge circuit 37 to 39, that is, an AC terminal 41. 43 are armature windings 11 to 11 of the AC generator 1.
It is configured to be individually connected to each end of 13.

Further, the main electrodes of the low-side elements 34 to 36, which are N-channel MOS transistors, on the battery lower terminal side are connected to a P-type substrate region (which may be a P-type substrate or a P-type well region) immediately below the gate electrode. A potential is applied to the substrate area. Therefore, in this embodiment, the parasitic diode D formed of a junction between the main electrodes of the low side elements 34 to 36 on the side of the stator coils 11 to 13 and the P-type substrate region is parasitically formed, and the parasitic diode D is formed. Constitutes the low-side element of a diode-type three-phase full-wave rectifier during rectification. Of course, the low side elements 34 to 36
It is naturally possible to connect a rectifying junction diode in parallel with the parasitic diode D in parallel.

The transistors 34 to 36 have a DMOS structure or a vertical power MOS structure in order to improve the breakdown voltage. In this way, the junction diodes 31 to 33 and the parasitic diode D that form the three-phase full-wave rectifier rectify the generated voltage of the vehicle three-phase AC generator 1 to charge the battery 7.

Next, the structure of the overvoltage suppression control circuit section 6 which is a characteristic part of this embodiment will be described. The overvoltage suppression control circuit unit 6 includes a constant voltage diode 61 having a rated breakdown voltage of 18V,
62 and a resistor r1 are connected in series, and the armature winding 11
Abnormal voltage detection circuit section 6a for detecting whether or not the generated voltage of ~ 13 exceeds a predetermined voltage value, and based on the output voltage of this abnormal voltage detection circuit section 6a, all the MOS transistors 34-36 are turned on at the time of the excess. Short circuit part 6b
Consists of.

The short circuit portion 6b comprises resistors r1 to r5, transistors 63 and 65, a constant voltage diode 64 having a rated breakdown voltage of 6V, capacitors C1 and C2, and a junction diode 66. The operation of the overvoltage suppression control circuit unit 6 will be described below. When the G pulse voltage is not generated, the constant voltage diodes 61 and 62 are in the cutoff state, so that the output voltage of the abnormal voltage detection circuit unit 6a including the voltage dividing circuit becomes the low level, the transistor 63 is turned off, and the ignition switch IGSW is turned on. Is turned on, the capacitor C1 is charged through the resistor r5, the diode 66 and the resistor r2, and the capacitor C1 is charged.
The constant voltage diode 64 to which the charging voltage of 1 is applied becomes conductive, and the output voltage of the voltage dividing circuit including the constant voltage diode 64 and the resistor r3 becomes high level and the transistor 6
5 is turned on, the output voltage of the inverter composed of the transistor 65 and the resistor r4 becomes low level, and the transistors 34 to 36 are turned off through the high frequency cutoff resistor rg.

If the terminals of the battery 7 are disconnected due to some trouble during charging of the battery 7, or if the output current of the three-phase full-wave rectifier 3 is suddenly reduced for some reason, the armature windings 11 to 13 are high. A G pulse voltage is generated, and this G pulse voltage is sent to the B terminal through the three-phase full-wave rectifier 3. When the B terminal voltage exceeds 36.6V, the output voltage of the abnormal voltage detection circuit unit 6a (the constant voltage diode 62 and the resistor r
1 (voltage at the connection point with 1) becomes a high level (about 0.7 V) to turn on the transistor 63, the capacitor C1 is discharged, the constant voltage diode 64 and the transistor 65 are cut off, and as a result, the transistors 34 to 36. A high-level voltage is applied to the gate electrode of the transistor through the resistor r5, the diode 66, the resistor r4, and the resistor rg to turn on.

In this way, each MOS transistor 34
When ~ 36 is conducted, the output terminals of the three-phase armature windings 11 to 13 are short-circuited by the channels of the MOS transistors 34 to 36, and the G pulse voltage is applied to the battery 7 and the load 9. Is prevented. Also,
Since the magnitude of the G pulse voltage itself is reduced, it is possible to avoid destruction of each semiconductor element or the like.

Even if the IG terminal voltage drops rapidly due to the disconnection of the battery terminal, the capacitor C2
Are charged through the diode 66, and the operation of the short circuit portion 6b is guaranteed. When the B terminal voltage drops due to the disappearance or attenuation of the G pulse voltage, the transistor 63
Cut off again, and the capacitor C1 has a resistance r5 and a resistance r2.
Through the constant voltage diode 64 and the transistor 6 after a lapse of a predetermined time determined by the CR time constant.
5, the MOS transistors 34 to 36 are turned off, and the three-phase full-wave rectifier can be rectified again. (Embodiment 2) Another embodiment of the apparatus of the present invention will be described with reference to FIG.

In this embodiment, when the B terminal voltage is 10 V or less after the transistors 34 to 36 are turned on when the G pulse voltage is generated, it is determined that the battery 7 is out of the three-phase full-wave rectifier 3, and the diode described later is used. A high level voltage is output from 84 to the gate electrodes of the transistors 34 to 36 to continue the conduction of the MOS transistors 34 to 36, thereby suppressing the G pulse until the connection of the battery terminals is secured. . On the other hand, even when the G pulse voltage is temporarily generated due to the noise voltage or the like, the battery voltage immediately after that is 10 V or more, and thus the charging is restarted as in the first embodiment.

Explaining in detail below, the overvoltage suppression control circuit unit 6 of this embodiment is the same as the overvoltage suppression control circuit unit 6 of the first embodiment except that the output of the voltage dividing circuit composed of the constant voltage diode 81 and the resistor r6. A transistor 82 operated by a voltage, diodes 83 and 84, and a resistor r7 are added, and further, the capacitor C1 is relocated between the base and collector of the transistor 63.

Therefore, the constant voltage diodes 61, 6
2. When the transistor 63 is turned on, the transistor 65 is turned off as in the first embodiment, and the resistor r5 and the diode 6 are turned on.
6, the transistor 3 through the resistor r4 and the diode 83
4 to 36 are turned on. Here, if the G pulse voltage is temporarily reduced due to noise or the like, the constant voltage diode 6
Even if 1, 62 and the transistor 63 are turned off, conduction of the constant voltage diode 64 and the transistor 65 is prohibited until it is charged by the presence of the capacitor C1.
As a result, the transistors 34 to 36 can be kept on.

When the battery 7 is removed, the B terminal voltage drops to OV, so that the constant voltage diode 81 is turned off and the transistor 82 is turned off.
Since the voltage of the capacitor C2 is applied to the gate electrodes of the S transistors 34 to 36 through the resistor r7,
The conduction of the transistors 34 to 36 will be maintained.

When the connection between the battery 7 and the three-phase full-wave rectifier 3 is restored, the B terminal voltage rises to the terminal voltage of the battery 7, so that the constant voltage diode 81 and the transistor 8 are connected.
2 conducts and diode 84 shuts off. In addition, the transistor 63 is cut off and the transistor 65 is turned on. As a result, the MOS transistors 34 to 36 are cut off to perform a normal rectification operation.

Therefore, in this embodiment, it is possible to suppress the G pulse generated when the battery 7 is disconnected by turning on the MOS transistors 34 to 36, and when the connection of the battery 7 is restored. The normal power generation control can be returned promptly. (Embodiment 3) Another embodiment will be described with reference to FIG.

This embodiment is the same as the second embodiment except that each MO is
The transistor operation control circuit unit 8 is added to each of the S transistors 34 to 36. The transistor operation control circuit unit 8 includes a comparator 85, diodes 86 and 87, and a resistor r8, and one set is provided for each of the MOS transistors 34 to 36. However, M
In the transistor operation control circuit portion 8 for driving the OS transistors 35 and 36, only the diode 87 is shown in FIG. 3 and is omitted thereafter.

Here, the diodes 86 and 87 and the resistor r8
Is a diode type OR circuit.
The logical sum signal of the logical outputs of 3, 84 and the logical output of the comparator 85 is applied to the MOS transistor 34 through the resistor rg.
Is applied to the gate electrode of. Comparator 85
Determines whether the terminal voltage of the armature winding 11 has dropped below the ground potential, and when it drops, applies a high-level voltage to the gate electrode of the transistor 34 to make it conductive, When the terminal voltage becomes higher than the ground potential, a low level voltage is output so that the MOS transistor 34 operates in the control mode of the second embodiment.

In this way, the low-side element of the three-phase full-wave rectifier 3 can be rectified with less loss than the diode (here, the parasitic diode D of the MOS transistors 34 to 36). (Modification) In the above embodiment, the high-side elements 31 to 33 of the three-phase full-wave rectifier 3 are composed of junction diodes, and the low-side elements 34 to 36 are composed of MOS transistors and their parasitic diodes D. As the high-side element and the low-side element of the three-phase full-wave rectifier 3, FIG.
One of a MOS transistor (a) with a parasitic diode, a junction diode (b), an IGBT (c) connected in parallel with the junction diode, and a bipolar transistor (d) connected in parallel with the junction diode is adopted as shown in FIG. can do.

Of course, at least one of the group of high-side elements 31 to 33 and the group of low-side elements 34 to 36 needs to be a transistor. It goes without saying that, contrary to the above embodiments, all the transistors that form the high side element can be turned on when the G pulse voltage is generated. However, when both the high-side elements 31 to 33 and the low-side elements 34 to 36 include transistors, and when either one of them is turned on to suppress the G pulse voltage,
All the other transistors must be turned off.
Specifically, the inverted signal of the signal voltage applied to the control terminals of the transistors that are turned on to suppress overvoltage is synthesized by the NOT circuit, and this inverted signal is applied to the control terminals of the transistors that are turned off. do it. Since such a circuit configuration is simple and obvious, its illustration is omitted.

Further, the high side elements 31 to 33 are MOS
When configured with a transistor, this MOS transistor detects whether or not the potential of the N ⁺ type region on the armature winding side exceeds the battery voltage with a comparator similar to the comparator 85 of FIG. A high level voltage may be applied to the gate electrode of the transistor with the same configuration as in FIG. However, in this case, the high-level potential of this comparator must be sufficiently higher than the battery voltage + threshold voltage of the MOS transistor 31, and the MOS transistor must be operated in a non-saturated state even as the high-side element. That is, in the circuit of FIG. 3, the potential of the connection point 41 is applied to the + input terminal of the comparator 85, and the −
It is understood that the MOS transistor as the high side element can be rectified by applying the battery voltage to the input end.

In the above embodiment, the bridge circuit constituting the three-phase full-wave rectifier 3 is protected from the G pulse voltage, but the bridge as an inverter for driving and controlling the three-phase AC motor has the same circuit configuration. It will of course be understood that the circuit can be protected from the G pulse voltage. Further, in the above description, an example in which at least the group of the low-side elements 34 to 36 or the high-side elements 31 to 33 is always turned on at least during the G pulse voltage detection period has been described.
3 or PW is used to suppress the heat generation of the transistors forming the low-side elements 34 to 36 below the allowable value.
M control is also possible. For such PWM control, an oscillator for generating a constant frequency signal voltage having a predetermined duty ratio is added to the circuit unit 5, and the constant frequency signal voltage and the collector voltage of the transistor 65 of FIG. Input to the circuit, and the logical product signal of this AND circuit is applied to these MOS transistors 3
4 to 36 may be controlled. Since such a circuit configuration is simple and obvious, its illustration is omitted.

Further, in each of the above embodiments, the generation of the G pulse voltage is detected based on the battery voltage.
It goes without saying that the output voltages of 1 to 13 may be directly detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a DC-AC converter of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is an element diagram showing a modified example of a high side element or a low side element.

[Explanation of symbols]

1 is a three-phase AC generator, 3 is a three-phase full-wave rectifier (bridge circuit), 6 is a control unit, 6a is an abnormal voltage detection circuit unit, 6b is a short circuit circuit unit, 7 is a battery, and 31 to 33 are high-side elements. , 34 to 36 are low-side elements.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-63-202255 (JP, A) JP-A-4-138030 (JP, A) JP-A-6-62526 (JP, A) JP-A-6- 62600 (JP, A) Actual development 63-48389 (JP, U) Japanese Patent Publication 45-16651 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 7/219 H02J 7 /twenty four

Claims (8)

(57) [Claims] 1. A required number of phase bridge circuits in which high side elements and low side elements each including a transistor are connected in series are connected in parallel, and a pair of direct current terminals are connected to both ends of a battery and a load. A bridge circuit in which each connection point is individually connected to each end of the armature winding of the AC rotating electric machine, and a control unit for controlling the on / off of the transistor, and the transistor is a generator of the AC rotating electric machine.
In the DC-AC converter that performs an operation of rectifying a voltage, the control unit detects an abnormal voltage detection circuit unit that detects whether the generated voltage of the armature winding exceeds a predetermined voltage value, and The transistors forming one of the two elements are all made conductive and the other of the elements is formed.
A DC-AC converter, comprising: a short circuit circuit that cuts off all the transistors . 2. The transistor comprises an N-channel MOS transistor in which a parasitic diode between a P-type substrate region immediately below a gate electrode and an N + -type region forming a main electrode is formed so as to rectify a generated voltage. Item 3. The DC-AC converter according to Item 1. 3. The high-side element or the low-side element is a bipolar transistor or an IGBT, and the bipolar transistor or the IG in a direction to rectify a generated voltage.
The DC-AC converter according to claim 1, comprising a junction diode connected in parallel with BT. 4. The control unit intermittently connects the MOS transistor at a predetermined timing to perform DC-AC conversion or AC-
The DC-AC converter according to claim 2, which is for performing DC conversion. 5. The DC-AC converter according to claim 3 , wherein the control section intermittently connects the bipolar transistor or the IGBT at a predetermined timing to apply an AC voltage to the rotating electric machine. 6. The DC-AC converter according to claim 1, wherein the control unit causes each of the transistors forming one of the elements to conduct at a predetermined average conductivity. 7. The DC circuit according to claim 1, wherein the short-circuit circuit section maintains the full conduction of the transistor for a predetermined time after the abnormal voltage detection circuit section detects the excess.
AC converter. 8. The short-circuit circuit section determines whether or not the DC terminal voltage has become equal to or lower than a predetermined value set lower than a battery voltage after the transistor has been fully conducted, and if not, the fully-conducted circuit is turned on. The DC-AC converter according to claim 1, which is continuous.