JPH02266873A - inverter device - Google Patents

Abstract

PURPOSE:To improve reliability by providing a DC-DC transducer, supplying a predetermined voltage to the gate of a power MOSFET. CONSTITUTION:An inverter device 1 converts a battery 2 into 3-phase AC current and supplies it to a permanent magnet brushless motor 3. The inverter device 1 is constituted of an operation control circuit 11, a DC-DC transducer 12, power MOSFETs 13-18, gate drive circuits for the power MOSFETs and the like while the DC-DC transducer 12 is provided with a constant voltage circuit 30. As a result, the FETs may be put ON surely even when the voltage of the battery 2 is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inverter device using power MOSFETs.

(Prior art) In an inverter circuit that bridge-connects FETs to supply power to a load such as a motor winding, a voltage with a higher polarity than the voltage of the DC power supply or a voltage with the opposite polarity to the voltage of the DC power supply is used. It is necessary to control the switching of the FET by supplying it to the gate of the FET.
The publication discloses a configuration in which a voltage boosted by a DC-DC converter (charge pump circuit) is applied to the gate of an N-channel MOSFET (hereinafter referred to as FET unless there is a particular problem).

(Problem to be Solved by the Invention) On the other hand, when driving a starter motor for engine starting from a battery via an inverter device,
The voltage of the battery may drop because a relatively large current flows through the battery, and fluctuations in the battery's output voltage vary greatly depending on the state of charge of the battery. There is also.

For this reason, an inverter device that uses a DC-DC converter to generate an output voltage of, for example, 18V for an input voltage of 12V and control the FET to be in the ON state, may temporarily reduce the battery voltage to 6V. When the output voltage of the DC-DC converter is about 9V, it may not be possible to completely drive the FET to a switching (saturated) state. In this case, the power consumption of the FET itself increases, and the FET generates heat due to the FET itself.
This may cause damage to the ET or deterioration of its characteristics.

The present invention was made to solve such problems, and its purpose is to maintain the power M even when the battery voltage fluctuates.
The present invention provides an inverter device that can reliably drive OSFETs.

(Means for Solving the Problems) In order to solve the above problems, an inverter device according to the present invention provides a power MO
It is characterized by comprising a DC-DC converter that supplies the gate of the SFET with the voltage necessary to drive the FET into the on state.

The DC-DC converter may be configured to receive a voltage lower than the battery voltage stabilized by the constant voltage circuit and generate a predetermined DC output voltage by the DC-DC converter circuit.

(Function) Even if the battery voltage drops, the FE gate remains
The voltage necessary to drive T into the on state is applied.

Therefore, the FET is reliably turned on.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit configuration diagram in which an inverter device according to the present invention is applied to the operation of a permanent brushless motor having three-phase windings.

In the figure, 1 is an inverter device, and a battery 2 is connected to the power supply voltages 1a and lb of the inverter device 1.
The output voltages 1c, ld, and le are applied to each winding 3a, 3b of a permanent magnet brushless motor (hereinafter referred to as motor) 3 as a load.
, 3c.

The inverter device 1 includes an operation control circuit 11, a DC-DC converter 12, and a power MOSFET (hereinafter referred to as FET).
13 to 18, their gate drive circuits, etc.

Operation control circuit! 1 is in the operating mode when the operation switch 19 is closed, and the stator windings 38 to 38 of the motor 3 are activated based on the position detection signal 20a of the rotational position detection means 20 of the motor 3.
3C, each FE7 is configured to supply a stepped three-phase alternating current that is advanced by a predetermined electrical angle from the magnetic pole of the permanent magnet rotor 3d.
The output voltage 11 is the signal that controls the on/off of 13 to 18.
It is output to a to 11f. Further, the operation control circuit 11 is configured to maintain the standby mode even when the operation switch 19 is changed from the open state to the closed state when the voltage detection signal 2ta of the voltage detection means 21 is at the L level.

The operation control circuit 11 of this embodiment is composed of a commercially available motor drive IC or a one-chip microcomputer that operates at a power supply voltage of 3V or more. The configuration is such that a voltage of

The voltage detection means 21 includes a reference voltage generation circuit and a voltage comparator, and outputs an L level signal to the output voltage 21a when the voltage applied to the input voltage 21b is less than a predetermined voltage value. In this embodiment, a voltage detection IC is used that outputs an L level as an output voltage when the input voltage 21b is approximately 4.5 V or less.

The constant voltage circuit 22 is composed of, for example, a three-voltage series regulator IC and its peripheral circuits, and the voltage of the battery 2 is applied to the input voltage 22a, and the output voltage 22b is connected to the power supply voltage 11g of the operation control circuit 11. has been done. In this embodiment, the voltage of the battery 2 is normally about 12V,
The output voltage of the constant voltage circuit 22 is 5V.

The DC-DC converter 12 has an input voltage 12a.

Based on the voltage of the battery 2 applied to the output voltage 12b, an output voltage boosted to the output voltages 12c and 12d is generated. In this embodiment, a direct current circuit consisting of a self-help oscillation circuit 23, switching transistors 24, 25, a step-up transformer 26 with a center tap, and a voltage doubler type rectifier circuit 27 is used.
It consists of a DC conversion circuit 28, a current limiting resistor 29, and a constant voltage circuit 30 such as a Zener diode. This DC-DC converter 12 has a voltage of 12a.

A constant voltage circuit 29 stabilizes and outputs a boosted voltage output proportional to the voltage input between the input voltage 12b and the input voltage 12a in this embodiment.

Voltage 12c, 12 when a voltage of 3v is applied between 12b
The output between the terminals d and d is about 15V, and even if the input voltage is increased, the output voltage remains approximately constant at about 24V.

The output voltage 12c of the DC-DC converter 12 is connected from the emitters to the collectors of the PNP transistors 31 to 36 constituting the gate drive circuit, and to the respective gates of the FEs 713 to 18 via gate protection resistors 37 to 42. ing. Each of the PNP transistors 31 to 36 is configured to be turned on via oven collector type inverting buffer circuits 42 to 48 when each output voltage 11a to llf of the operation control circuit 11 reaches an H level.

The drains of FETs 13 to 15 are connected to the positive side of battery 2, the sources of FETs 16 to 18 are connected to the negative side of battery 2, and the sources of FETs 13 to 15 and FETs are connected to the negative side of battery 2.
The drains of ET18 to 18 have voltages 1c, ld, and
Connected to Ie. Note that diodes 49 to 49 are connected in antiparallel between the drains and sources of FETs 13 to 18.
Reference numeral 54 denotes a through-flow diode for absorbing surges generated in the windings 3a to 3c of the motor 3 when the FEs 713 to 18 are off.

With the above configuration, when the electromotive voltage of the battery 2 is lower than the voltage set by the voltage detection means 21, that is, when the battery 2 is almost discharged and does not have enough power supply capacity to start the motor 3, the operation switch is switched off. 19 is operated, the operation control circuit 11 maintains the standby mode.

When the battery 2 has an electromotive force equal to or higher than a predetermined voltage value in a no-load state, when the operation switch 19 is operated to the closed state, the operation control circuit 11 changes the output voltage 11 at a predetermined timing.
A gate drive control output is generated at a to llf to start the motor 3. At this time, a large current is supplied to the windings 3a to 3c of the motor 3, and even if the electromotive voltage of the battery 2 decreases as a result, the output voltage of the DC-DC converter 12 is FE
Since the voltage necessary to drive T13-18 is generated, FETs 13-18 can be reliably turned on.

FIG. 2 is a circuit configuration diagram showing another embodiment of the present invention.

In this embodiment, the inverter device according to the present invention is applied to the operation of a three-phase induction motor, and the same components as in FIG. 1 are denoted by the same reference numerals.

A battery 62 is connected to the power supply voltages 61a and 61b of the inverter device 61, and the output voltages 61c and 61d
, 61 e are each winding 63 a, 6 of the induction motor 63
3b and 63c.

The inverter device 61 includes an operation control circuit 71, a DC-DC converter 72, FETs 15 to 18, their drive circuits 33 to 48, and the like.

The DC-DC converter 71 includes a constant voltage circuit 73, a first-stage booster circuit 74, and a second-stage booster circuit 75.

The constant voltage circuit 73 changes to voltage 7 when the operation switch 19 is closed.
The voltage of the battery 62 applied to 3a is used as human power, and a stabilized voltage output is output to voltage 73b.

In this embodiment, the nominal voltage of the battery 62 is 24V,
The constant voltage circuit 73 supplies an output voltage of 12V to the operation control circuit 71.

The first stage booster circuit 74 uses the output voltage of the constant voltage circuit 73 as a power source, and generates a boosted voltage approximately twice that amount as a voltage 74a. This first stage booster circuit 74 includes a PNP transistor 7 and an NPN transistor 78, which are repeatedly turned on and off in a complementary manner by an output cuff 6a of a self-excited oscillation circuit 76.
2 diodes 79.80 and 2 capacitors 8
It consists of 1.82. Output voltage 7 of constant voltage circuit 73
From 3b, a charging circuit for a capacitor 81 is formed by the route of diode 79 - diode 80 - capacitor 8l - GND @ child 73c, and the diode 80 and capacitor 81
The connection point of is connected to voltage 74a. capacitor 8
One end of 2 is connected to the collector of a transistor 77.78 connected in series between voltage 73b and voltage 73c,
The other end of the capacitor 82 is connected to a connection point between two diodes 79 and 80, and this point becomes a connection voltage 74b with the booster circuit 75 at the subsequent stage.

The capacitor 82 is charged through the diode 79 when the NPN transistor 8o is on, and then when the NPN transistor 80 is turned off and the PNP transistor 7 is turned on, the charge in the capacitor 82 is discharged to the capacitor 81 through the diode 80. Since this charging and discharging is repeated based on the oscillation frequency of the oscillation circuit 76, the voltage 74a is approximately twice the output voltage of the constant voltage circuit 73 (approximately 24
A voltage of V) is obtained.

The second-stage booster circuit 75 includes six booster circuits 75A to 75F provided corresponding to each of the FETs 13 to 18. The voltages 74a and 74b of the first stage booster circuit 74 are applied to the second stage booster circuit 75.
are connected in parallel to the voltages 75a..., 75b..., respectively. Boosted output voltage 75d of the subsequent booster circuit 75...
* is PNP) - connected to the emitters of the run listers 31 to 36, respectively. This rear step booster circuit 75 has a voltage 75b
Two diodes 83 and 84 are connected in series in the forward direction between and voltage 75d, and a capacitor 85 is connected between the connection point of diode 83 and diode 84 and voltage 75a,
It is composed of a half-wave voltage doubler rectifier circuit in which a capacitor 86 is connected between the voltage 75d and the GND voltage 75c. All booster circuits 75A to 75F have the same configuration.

Like the first-stage booster circuit, the second-stage booster circuits 75 to 75F charge the capacitor 85 via the diode 83,
By repeating the operation of discharging the charge of the capacitor 85 to the capacitor 86 via the diode 84, the output voltage 75d
A boosted output voltage approximately three times the output voltage of the constant voltage circuit 73 (approximately 36 V in this embodiment) is obtained.

When the output voltage of the constant voltage circuit 73 is applied to the power supply voltage 71g and the initial signal 87a from the power-on initial (POI) circuit 87 is input, the control circuit 71 checks the detection output signal of the voltage detection means 88. , when the signal is at H level, the setting signal 89 of the rotation speed setting means 89
The circuit is configured to output an H level gate drive signal to the output voltages 71a to 71f at a predetermined timing based on the output voltage 71a to 71f.

The voltage detection means 88 of this embodiment is configured to generate an H level output when the voltage of the battery 62 is 12V or more, and to generate an L level output when it is less than 12V. Also,
The operation control circuit 71 detects that even when the electric motor 63 is in operation, the voltage of the battery 62 becomes less than 12V, and the voltage detection means 8
If the output 88a of 8 remains at L level for a certain period of time, the outputs of voltages 71a to 71f are set to L level and the FET
13 to 18 are stopped, an H level output is generated at the alarm output voltage 7th, and the LED in the display circuit 90 is turned on for visual display.

With the above configuration, when the operation switch 19 is operated to the closed state, the inverter device 61 rotates the electric motor 63 at a set rotation speed if the voltage of the battery 62 is equal to or higher than a predetermined voltage value. A voltage boosted from the voltage of the battery 62 is supplied from the DC-DC converter 75 to the gates of the FETs 13 to 18, and the FETs 13 to 18 are reliably controlled to be in the on state. If the voltage of the battery 62 is less than a predetermined voltage value, the operation of the electric motor 63 is stopped, and the display circuit 90 displays a message indicating that it is in a stopped state.

Note that, prior to operation of the electric motor 63, the operation control circuit 71 drives specific FETs (for example, FET 15 and FET 17) to an on state for a predetermined short time, and causes the battery 62 to turn on specific windings (for example, winding 3a) of the electric motor 63. ) may be configured to check the voltage of the battery 63 while supplying current to the battery 63, and start operation if the voltage is equal to or higher than a predetermined voltage value.

Note that this embodiment has a configuration in which a boosted voltage is applied to the gates of all FETs 13 to 18, but the upper FET
A configuration may be adopted in which a boosted voltage is applied only to ETs 13 to 15.

Note that each embodiment uses an N-channel type power MOSFE.
In the case of a P-channel type power MOSFET, an inverter device using T is described, but in the case of a P-channel type power MOSFET, a voltage with a polarity opposite to that of the battery may be generated by a DC-DC converter, and this may be applied to each gate.

(Effects of the Invention) As explained above, in the inverter device according to the present invention, the DC-DC converter is configured so that a predetermined voltage can be supplied to the gate of the power MOSFET even if the battery voltage decreases. Even if the voltage of the battery decreases due to the supply of large current to the load, such as when the electromotive voltage of the power MOSFET decreases or when the battery capacity decreases at low temperatures, the power MOSFET The switching operation can be performed reliably.

Therefore, the on-voltage (voltage between the drain and source) of the FET increases due to insufficient voltage applied to the gate, and the power consumption of the FET increases, which prevents damage due to heat generation and deterioration of characteristics, and improves reliability. It is possible to provide an inverter device with high performance.

The DC-DC converter has a configuration that converts the boosted voltage into a constant current.
Alternatively, since the voltage from the battery is boosted after being passed through a constant voltage circuit based on the voltage from the battery, even if design conditions such as the final voltage of the battery used and the voltage applied to the gate of the FET vary, the boost ratio It can be applied universally by simply adjusting the voltage value for constant voltage, and it can contribute to the standardization and cost reduction of inverter devices.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram in which an inverter device according to the present invention is applied to the operation of a three-phase brushless motor, and Fig. 2 is a circuit diagram in which an inverter device according to another embodiment of the present invention is applied to the operation of a three-phase induction motor. FIG. In addition, in the drawing, 1.61 is an inverter device, 2.62 is a battery, 3.83 is an electric motor (load), 1
1.71 is an operation control circuit, 12.72 is a DC-DC converter, 13 to 18 are bar'7-M05FETs, and 28 is a DC-DC converter.
DC conversion circuit, 3° is constant voltage circuit, 73 is constant voltage circuit,
74 is a first-stage booster circuit, and 75 is a second-stage booster circuit.

Claims (3)

[Claims] (1) Power MOS bridge-connected from battery
In an inverter device that supplies power to a load via a FET, the inverter supplies the voltage necessary to turn on the power MOSFET to the gate of the power MOSFET even when the battery voltage drops. An inverter device comprising a DC-DC converter for supplying direct current. (2) The DC-DC converter comprises a DC-DC converter circuit that generates a boosted output voltage proportional to the input voltage, and a constant voltage circuit that receives the boosted output voltage as an input. The inverter device described. (3) The DC-DC converter includes a constant voltage circuit and a DC-DC converter circuit that generates a predetermined DC output voltage by inputting a voltage lower than the battery voltage stabilized by the constant voltage circuit. The inverter device according to claim 1, characterized in that: