JP2014045563A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simply configured inverter device capable of reducing the loss and preventing a reflux diode etc. from getting damaged.SOLUTION: The inverter device is configured including: a reflux diode 2 connected to a switching element 1 in inverse-parallel thereto; a switching element control signal generation section 3; a driver section 6 that supplies a voltage and a current to the switching element for a period of time according to a signal from the switching element control signal generation section; an impulse generation section 7 that generates an impulse signal from an output signal supplied from the switching element control signal generation section; and a diode 8 that eliminates negative impulses in the impulse signal generated by the impulse generation section and allows positive impulses only. With this simple configuration, since a short-circuit current is reduced when the reflux diode is activated at inverse recovery, the efficiency is increased by reducing the power loss and the switching element and the diode are prevented from getting damaged.

Description

  The present invention relates to an inverter device that outputs driving power to an inductive load such as a motor.

  In general, an inverter device that supplies power to an inductive load, for example, an inverter device that outputs driving power for a brushless DC motor, has a plurality of upper and lower switching elements, and these switching elements are connected in reverse parallel to each other. A diode is included, and an interconnection point of each switching element is connected to each phase winding of the brushless DC motor.

  Recently, many IGBTs and MOSFETs have been adopted as switching elements.

  In the case of MOSFET, there is a merit that high-frequency switching is possible because the on / off speed is fast, and it is often used when driving a motor with a small output such as a fan motor because the loss at the time of low voltage and low current output is small. .

  However, in the MOSFET, a parasitic diode having a bad reverse recovery characteristic is formed on the element in the process of manufacturing the element. Therefore, when a forward current due to the energy stored in the inductive load flows through the diode, a large reverse current (short-circuit current) flows through the diode as the other switching element is turned on, resulting in a large power loss. Further, the switching element and the diode may be destroyed.

  The above will be described with reference to FIG. When a forward current of the diode flows from the GND to the inductive load 101 through the diode D2 as indicated by “a” in FIG. 7, the control signal from the control unit 102 to the switching element Tr1 as indicated by “b”. Is input, while the DC voltage source is applied to the diode D2 as shown in “c” and the diode D2 reversely recovers, the positive terminal of the DC voltage source 103 → the switching element Tr1 → the diode D2 → the DC voltage source 103 A short-circuit current flows in the order of the negative terminal (GND). For this reason, a big electric power loss and the fear of destruction of a switching element and a diode arise.

  In recent years, as the switching frequency is increased, the device withstand voltage is increased, and the efficiency of the device is improved, a method for reducing the switching loss by improving the inverter device has been proposed (for example, patents). Reference 1).

  FIG. 8 shows an inverter device described in Patent Document 1, in which the switching element 104 is driven by a motor using a MOSFET. In this inverter device, a reverse voltage application circuit 106 that applies a reverse voltage to the diode 105 prior to turning on the other switching element 104 in order to reduce a loss due to a reverse current generated in the diode 105 connected in reverse parallel to the switching element 104. And the reverse current flowing through the diode 105 when the other switching element 104 is turned on is reduced by applying the reverse voltage, thereby reducing the power loss of the inverter device.

Japanese Patent Laid-Open No. 10-327585

  However, as described above, in the conventional inverter device, in order to improve efficiency, selection of switching elements, addition of a countermeasure circuit for reducing loss in reverse recovery, and the like are performed. If such an expensive element and a countermeasure circuit for reducing loss in reverse recovery are provided, the countermeasure circuit is complicated and has a large number of parts, resulting in a reduction in efficiency and an increase in cost.

  Therefore, the present invention solves the above-mentioned problem, improves efficiency by reducing loss in reverse recovery of the diode, further prevents switching elements and diodes from being destroyed, and suppresses cost increase with a simple configuration. An object of the present invention is to provide an inverter device that can be used.

  To achieve the above object, the present invention controls a pair of upper and lower switching elements connected to a DC voltage source and supplying power to an inductive load, a freewheeling diode connected in reverse parallel to the switching elements, and the switching elements. A switching element control signal generation unit that generates an output signal for performing the operation, a driving unit that supplies time, voltage, and current to the switching element according to the signal of the switching element control signal generation unit, and the switching element control signal generation An impulse generator that generates an impulse signal from the output signal of the unit, and a diode that cuts a negative impulse from the impulse signal generated by the impulse generator and passes only a positive impulse, and the switching element operates. Before starting the output signal of the switching element control signal generator. There the generated impulse signal as a configuration applied to the return diode.

  As a result, reverse recovery of the freewheeling diode is started not by the high voltage of the DC voltage source but by the impulse signal from the impulse generator, so that the short circuit current flowing through the freewheel diode can be reduced and the time during which the short circuit current flows can be shortened.

  According to the inverter device of the present invention, since the short-circuit current during the reverse recovery operation of the freewheeling diode can be reduced without using expensive elements and many parts, the power loss is reduced and the efficiency is improved. The destruction of the element and the diode can be prevented, and the configuration can be simplified to suppress an increase in cost.

The block diagram which shows the basic composition of the inverter apparatus in Embodiment 1 of this invention. The time chart which shows control of the inverter apparatus of the inverter apparatus in Embodiment 1 Block diagram of the inverter device in the second embodiment Block diagram of the inverter device in the third embodiment Block diagram of the inverter device in the fourth embodiment Block diagram of a three-phase inverter device in the fifth embodiment Explanatory drawing which shows a mode that a short circuit current flows into the switching element in the conventional inverter apparatus Block diagram showing a conventional inverter device

According to a first aspect of the present invention, there is provided a pair of upper and lower switching elements connected to a DC voltage source for supplying power to an inductive load, a freewheeling diode connected in reverse parallel to the switching elements, and an output signal for controlling the switching elements A switching element control signal generation unit for generating the switching element, a drive unit for supplying time, voltage and current to the switching element according to the signal of the switching element control signal generation unit, An impulse generator that generates an impulse signal, and a diode that cuts a negative impulse from the impulse signal generated by the impulse generator and passes only a positive impulse, and before the switching element starts operation The impulse generated from the output signal of the switching element control signal generator Some as structure to be applied to the return diode Patent.

  As a result, the freewheeling diode starts reverse recovery with the impulse signal from the impulse generator instead of the high voltage of the DC voltage source, the short circuit current flowing through the freewheel diode can be reduced, and the time during which the short circuit current flows can be shortened. As a result, power loss can be reduced without using expensive elements and many parts, efficiency can be improved, destruction of switching elements and diodes can be prevented, and the configuration can be simplified to suppress cost increase. Can do.

  According to a second invention, in the first invention, the time of the control signal supplied to the switching element from the switching element control signal generation unit via the drive unit can be arbitrarily set, and a delay adjustment unit is provided.

  As a result, the operation start time of the switching element can be arbitrarily changed so that the short-circuit current is minimized. As a result, the efficiency is improved by further reducing the power loss, and the switching element and the free wheel diode are destroyed. Can be more effectively prevented.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a control time adjustment unit that can arbitrarily set the time of the impulse signal applied to the freewheeling diode is provided.

  Thereby, the H time of the impulse signal applied to the switching element can be arbitrarily changed so as to minimize the short-circuit current. As a result, the power loss can be further reduced to improve the efficiency, and the switching element can be more efficiently performed. In addition, destruction of the reflux diode can be prevented.

  According to a fourth invention, in the first, second, or third invention, an amplitude adjustment unit that can arbitrarily set the amplitude of an impulse signal applied to the freewheeling diode is provided.

  Thereby, the amplitude of H of the impulse signal applied to the switching element can be arbitrarily changed so as to minimize the short-circuit current, and as a result, the efficiency can be improved by further reducing the power loss.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing a basic configuration of an inverter device according to Embodiment 1 of the present invention, and shows only the U phase in a three-phase inverter device. FIG. 2 is a time chart showing control of the inverter device of the inverter device according to the first embodiment.

  Reference numeral 1 denotes a switching element, which represents a MOSFET, the switching element 1u + is a switching element for the upper arm, and the switching element 1u− is a switching element for the lower arm. The switching element 1u + and the switching element 1u− are connected to the source terminal of the switching element 1u + and the switching element 1u− drain terminal. The switching element 1 may be another device such as an IGBT.

Reference numeral 2 denotes a free-wheeling diode, the anode of the free-wheeling diode 2u + and the switching element 1u.
The + source, the cathode of the freewheeling diode 2u +, and the drain of the switching element 1u + are connected. The freewheeling diode 2u− is also connected to the switching element 1u− in the same connection as the freewheeling diode 2u +.

  Reference numeral 3 denotes a switching element control signal generator, which generates a control signal for controlling the switching element 1. Reference numeral 4 denotes a DC voltage source, which is generated by rectifying a commercial AC power supply. The positive terminal of the DC voltage source 4 is connected to the drain of the switching element 1u +, and the negative terminal (0 V or GND) is connected to the source terminal of the switching element 1u−. An inductive load 5 is an inductive load such as a DC brushless motor. The inductive load 5 is connected to a connection point between the source terminal of the switching element 1u + and the switching element 1u−drain terminal.

  Reference numeral 6 denotes a drive unit that supplies time, voltage, and current to the switching element 1 in accordance with a signal from the switching element control signal generation unit 3. Reference numeral 7 denotes an impulse generator, which generates an impulse signal from the output signal of the switching element control signal generator 3. Reference numeral 8 denotes a diode, which cuts a negative impulse among impulse signals generated by the impulse generator 7, passes only a positive impulse, and applies the positive impulse signal to the drain side of the switching element 1.

  Next, specific control will be described.

  FIG. 2 is a time chart showing the control of the inverter device shown in FIG. 1, and the signals shown by a to h in FIG. 2 correspond to the signals passing through the points a to h in FIG.

  First, referring to FIG. 1, the control of the inverter device during reverse recovery of the freewheeling diode 2u- will be described.

  1 and 2, the signal a output from the switching element control signal generator 3 changes from L → H. At this time, when the signal a is L, the switching element 1u + and the switching element 1u− are supplied with current from the GND via the freewheeling diode 2u− to the inductive load 5. When the signal a is H, current is supplied to the inductive load 5 from the DC voltage source 4 via the switching element 1u +.

  When the signal a changes from L → H, the signal a is input to the impulse generator 7u−, and the impulse signal b is output from the impulse generator 7u− and input to the diode 8u−. The impulse generator 7u- is constituted by, for example, a high-pass filter.

  The diode 8u− passes only the positive impulse signal among the input positive and negative impulse signals, and outputs the signal c to the drain side of the switching element 1u−. The signal a output from the switching element control signal generation unit 3 is also input to the driving unit 6, and the driving unit 6 supplies the signal d to the switching element 1u + according to the signal a from the switching element control signal generation unit 3. The

In the absence of the impulse generator 7u- and the diode 8u-, when the signal a output from the switching element control signal generator 3 changes from L to H, the inductive load 5 receives a current from GND through the freewheeling diode 2u-. Since the switching element 1u + starts to operate from the state in which is supplied, a reverse voltage (the cathode and the DC voltage source 4 are connected and the cathode and GND are connected) is applied to the freewheeling diode 2u−. The free-wheeling diode 2u- is connected to the positive terminal of the DC voltage source 4 → the switching element 1u + → the free-wheeling diode 2u− → the negative terminal (GND) of the DC voltage source 4 while reverse recovery is started and reverse recovery (the diode is going to turn OFF). ) In the order of large short circuit current.

  However, by providing the impulse generator 7u− and the diode 8u−, the impulse signal c is applied before the gate-source voltage d of the switching element 1u + is applied. The reverse recovery operation is started with the impulse signal c (for example, 5V) instead of the voltage (for example, 280V), and a small voltage is applied to the freewheeling diode 2u−. 4 plus terminal → switching element 1u + → freewheeling diode 2u− → minus terminal (GND) of DC voltage source 4 can be reduced, and the time for which the short circuit current flows can be shortened. Efficiency is improved by reducing power loss, and switching element 1 and freewheeling diode 2 are destroyed. You can stop, and it is possible to suppress an increase in cost for simple configuration.

  Next, the control of the inverter device during reverse recovery of the freewheeling diode 2u + will be described with reference to FIG.

  1 and 2, the signal e output from the switching element control signal generator 3 changes from L → H. At this time, when the signal e is L, the switching element 1u + and the switching element 1u− have a current flowing from the inductive load 5 to the plus terminal of the DC voltage source 4 through the freewheeling diode 2u +. When the signal b is H, a current flows in the order of the inductive load 5 → the switching element 1u− → GND.

  When the signal e changes from L → H, the signal e is input to the impulse generator 7u +, and the impulse signal f is output from the impulse generator 7u + and input to the diode 8u +. The impulse generator 7u + is constituted by a high-pass filter, for example.

  The diode 8u + passes only the positive impulse signal among the input positive and negative impulse signals, and outputs the signal g to the drain side of the switching element 1u +. The signal e output from the switching element control signal generation unit 3 is also input to the driving unit 6. In the driving unit 6, the signal h is supplied to the switching element 1 u − according to the signal e from the switching element control signal generation unit 3. Is done.

  Without the impulse generator 7u + and the diode 8u +, when the signal e output from the switching element control signal generator 3 changes from L → H, the current flows in the order of the inductive load 5 → the freewheeling diode 2u + → the DC voltage source 4. Since the switching element 1u− starts operating from the flowing state, a reverse voltage (the cathode and the DC voltage source 4 are connected, and the cathode and GND are connected) is applied to the freewheeling diode 2u−. The free-wheeling diode 2u− starts reverse recovery and reverse recovery (the diode is going to be turned off). The positive terminal of the DC voltage source 4 → the freewheeling diode 2u + → the switching element 1u− → the negative terminal of the DC voltage source 4 (GND) ) In the order of large short circuit current.

However, by providing the impulse generator 7u + and the diode 8u +, the impulse signal g is applied before the gate-source voltage h of the switching element 1u- is applied, so that the freewheeling diode 2u- Reverse recovery starts with an impulse signal g (for example, 5V) instead of a voltage (for example, 280V), and a small voltage is applied to the freewheeling diode 2u +. Therefore, the current flowing through the freewheeling diode 2u− is also small, the short-circuit current flowing in the order of the positive terminal of the DC voltage source 4 → the freewheeling diode 2u + → the switching element 1u− → the negative terminal (GND) of the DC voltage source 4 is reduced, and The time during which the short-circuit current flows can be shortened. As a result, the efficiency can be improved by reducing the power loss, the destruction of the switching element 1 and the freewheeling diode 2 can be prevented, and the cost is increased due to the simple configuration. Can be suppressed.

  In addition, since d and h of FIG. 2 become H simultaneously, the dead time is provided so that the switching element 1u + and the switching element 1u− may be simultaneously turned ON and no short-circuit current flows.

(Embodiment 2)
FIG. 3 is a block diagram showing an example of the configuration of the inverter device according to Embodiment 2 of the present invention.

  3, the inverter device according to the second embodiment includes two delay adjusting units 9 between the driving unit 6 and the switching elements 1u + and 1u− in FIG. That is, as compared with the first embodiment, the time of the control signals d and h in FIG. 2 supplied to the switching element 1 from the switching element control signal generation unit 3 via the drive unit 6 is arbitrarily changed. be able to. The delay adjusting unit 9 is configured by a resistor, for example. The other blocks are the same as in FIG.

  The inverter device according to the second embodiment of the present invention configured as described above is switched so that the short-circuit current is minimized according to the characteristics of the switching element 1 and the freewheeling diode 2, the conditions of the inductive load 5, and the like. The operation start time of the element 1 can be arbitrarily changed. As a result, the power loss can be further reduced, the efficiency can be improved, the switching element 1 and the freewheeling diode 2 can be prevented from being destroyed, and the simple configuration can suppress the increase in cost.

(Embodiment 3)
FIG. 4 is a block diagram showing an example of the configuration of the inverter device according to the embodiment of the present invention.

  4, the inverter device according to the third embodiment includes two control time adjustment units 10 between diodes 8u + and 8u− and switching elements 1u + and 1u− in FIG. That is, as compared with the first embodiment, the time of the H signal of the c and g impulse signals supplied to the switching element 1 in FIG. 2 can be arbitrarily changed. Note that the control time adjustment unit 10 is configured by an operational amplifier, for example. The other blocks are the same as in FIG.

  The inverter device according to the third embodiment configured as described above has the switching elements 1u + and 1u so that the short-circuit current is minimized according to the characteristics of the switching element 1 and the freewheeling diode 2, the conditions of the inductive load 5, and the like. The H time of the impulse signal applied to the drain of − can be arbitrarily changed. As a result, the efficiency can be improved by further reducing the power loss, the destruction of the switching element 1 and the freewheeling diode 2 can be prevented, and the increase in cost can be suppressed due to the simple configuration.

(Embodiment 4)
FIG. 5 is a block diagram showing an example of the configuration of the inverter device according to Embodiment 4 of the present invention.

5, the inverter device according to the fourth embodiment includes two amplitude adjusting units 11 between diodes 8u + and 8u− and switching elements 1u + and 1u− in FIG. That is, as compared with the first embodiment, the amplitudes of the H signals of the c and g impulse signals supplied to the switching element 1 in FIG. 2 can be arbitrarily changed. Note that the control time adjustment unit 10 is configured by, for example, a resistor. The other blocks are the same as in FIG.

  The inverter device according to the fourth embodiment configured as described above has the switching elements 1u + and 1u so that the short-circuit current is minimized according to the characteristics of the switching element 1 and the freewheeling diode 2, the conditions of the inductive load 5, and the like. The amplitude of H of the impulse signal applied to the drain of − can be arbitrarily changed. As a result, the efficiency can be improved by further reducing the power loss, the destruction of the switching element 1 and the freewheeling diode 2 can be prevented, and the increase in cost can be suppressed due to the simple configuration.

(Embodiment 5)
FIG. 6 is a block diagram showing an example of the configuration of an inverter device according to Embodiment 5 of the present invention, and shows a U-phase, V-phase, and W-phase three-phase inverter device.

  6, the inverter device according to the fifth embodiment includes the V-phase and W-phase switching elements 1v +, 1v−, 1w +, 1w−, the freewheeling diodes 2v +, 2v−, 2w +, 2w−, and impulse generation. 7v +, 7v−, 7w +, 7w−, and diodes 8v +, 8v−, 8w +, 8w−. That is, all three phases can be controlled as compared with the first embodiment. The other blocks are the same as in FIG.

  The inverter device according to the fifth embodiment configured as described above further reduces power loss by controlling all three phases of the U phase, the V phase, and the W phase by the same control as the fifth embodiment. As a result, the efficiency can be improved, the switching element 1 and the freewheeling diode 2 can be prevented from being destroyed, and the simple configuration can suppress the increase in cost.

  As described above, the present invention can improve efficiency by reducing power loss, further prevent destruction of switching elements and diodes, and suppress increase in cost, and is widely applied as an inverter device for various devices. be able to.

1 (1u +, 1u−, 1w +, 1w−) Switching element 2 (2u +, 2u−, 2w +, 2w−) Free-wheeling diode 3 Switching element control signal generating unit 4 DC voltage source 5 Inductive load 6 Driving unit 7 (7u +, 7u−, 7w +, 7w−) Impulse generator 8 (8u +, 8u−, 8w +, 8w−) Diode 9 Delay adjustment unit 10 Control time adjustment unit 11 Amplitude adjustment unit

Claims (4)

A pair of upper and lower switching elements connected to a DC voltage source for supplying power to the inductive load, a freewheeling diode connected in reverse parallel to the switching element, and a switching element control for generating an output signal for controlling the switching element A signal generation unit; a drive unit that supplies time, voltage, and current to the switching element according to a signal from the switching element control signal generation unit; and an impulse that generates an impulse signal from the output signal of the switching element control signal generation unit A generator, and a diode that cuts a negative impulse among the impulse signals generated by the impulse generator and passes only a positive impulse, and before the switching element starts operation, the switching element control signal Impulse signal generated from output signal of generator Inverter device and applying the over-de. 2. The inverter device according to claim 1, further comprising a delay adjustment unit capable of arbitrarily setting a time of a control signal supplied from the switching element control signal generation unit to the switching element via the driving unit. The inverter apparatus according to claim 1, further comprising a control time adjustment unit that can arbitrarily set a time of the impulse signal applied to the free wheeling diode. 4. The inverter device according to claim 1, further comprising an amplitude adjusting unit capable of arbitrarily setting an amplitude of an impulse signal applied to the free wheeling diode.

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