JP2011035983A - Power supply circuit for inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely suppress a rush current and a rise of a voltage of a regeneration capacitor by using a circuit which is relatively low in price and easy in mounting. <P>SOLUTION: When suppressing the rise of the voltage caused by the charge of the smoothing capacitor 105 using regeneration power, a DC power supply of a control part 119 which turns on a voltage-absorption switch 109 uses a bootstrap power supply circuit in which a current flows and is formed as shown by a dashed arrow D in Fig. via a bootstrap diode 117 from a control power supply 114. Three power resistors of a power resistor which suppresses the rush current generated at the input of DC input power, a power resistor which discharges accumulated electric charges in order to suppress the rise of the voltage caused by charging the capacitor by a regeneration power and a power resistor which is used in the bootstrap power supply circuit and stabilizes an output voltage of the power supply circuit are made to be common by one power resistor 112. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inverter power supply circuit in which DC input power is smoothed by a capacitor and output to an inverter circuit, and regenerative power from the inverter is stored in the capacitor. In particular, the present invention is relatively inexpensive and easy to mount. The present invention relates to an inverter power supply circuit that can reliably perform operations of suppressing an inrush current and suppressing a voltage increase of a regenerative capacitor.

  FIG. 1 is a circuit diagram of a conventional general inverter power supply circuit.

  In this figure, AC power supplied from an external three-phase or single-phase AC power source 101 is rectified to DC by a rectifier 102. The rectified DC power is rectified after the pulsating flow is removed by the smoothing capacitor 105 and supplied to the inverter 106. The inverter 106 generates AC power having a predetermined voltage and frequency from the supplied DC power, and rotates the motor 108.

  Here, when power supply from the AC power supply 101 is started in a state where the accumulated charge in the smoothing capacitor 105 is small (power is turned on), as indicated by the one-dot chain line arrow A in FIG. A charging current flows from the AC power supply 101 (inrush current).

  In order to suppress such inrush current, when power is turned on, the inrush current is suppressed by the power resistance of the inrush current suppression circuit, and the power of the inrush power is consumed. For example, in the inverter power supply circuit of FIG. 1, an inrush current suppression circuit is configured around the input current bypass switch 103 and the inrush current suppression resistor 104.

  In FIG. 1, in order to suppress such inrush current, the input current bypass switch 103 in parallel with the inrush current suppression resistor 104 is turned off when the power is turned on. Then, all the current from the rectifier 102 flows through the inrush current suppression resistor 104, and the inrush current is suppressed by the electrical resistance of the inrush current suppression resistor 104, and is consumed as electric power.

  As the charge current flows and the electric charge is accumulated in the smoothing capacitor 105, the voltage of the smoothing capacitor 105 increases. Therefore, the difference between the voltage and the output side voltage of the rectifier 102 is gradually reduced. The charging current decreases. Thereafter, the input current bypass switch 103 is turned on until the motor 108 is rotated by the inverter 106. As a result, the inrush current suppression resistor 104 is bypassed by the input current bypass switch 103, and direct current power is directly supplied from the rectifier 102 to the inverter 106 and the smoothing capacitor 105.

  Next, the regenerative power generated as the motor 108 rotates and decelerates is stopped and stored in the smoothing capacitor 105 from the inverter 106. When the charge accumulated in the smoothing capacitor 105 increases, the voltage of the smoothing capacitor 105 increases. Here, it is necessary to suppress the voltage of the smoothing capacitor 105 within a specified range such as its rated voltage.

  For this reason, the voltage absorption circuit causes a current to flow so as to discharge the electric charge stored in the smoothing capacitor 105, or a current of the regenerative power is bypassed so as not to flow into the smoothing capacitor 105 (voltage absorption operation). ). In FIG. 1, this voltage absorption circuit is constituted by the voltage absorption switch 124, the power resistor 125, and the surge absorption diode 126. The surge absorption diode 126 absorbs a surge current generated when the voltage absorption switch 124 is turned on / off.

  In FIG. 1, the voltage absorption switch 124 is turned on during this voltage absorption operation. Then, as indicated by a two-dot chain line arrow B, the current due to the accumulated charge of the smoothing capacitor 105 flows through the power resistor 125 and is discharged, and the voltage of the smoothing capacitor 105 drops. At the same time, as indicated by the two-dot chain line arrow B, the current due to the regenerative power from the inverter 106 also flows to the power resistor 125, and charging of the smoothing capacitor 105 is suppressed.

  Here, FIG. 2 is a circuit diagram showing the inverter power supply circuit of Patent Document 1. In FIG.

  FIG. 2 is a reproduction of FIG. 3 of Patent Document 1. In the above-described inverter power supply circuit of FIG. 1, two power resistors that increase the rated power, which are the inrush current suppression resistor 104 and the power resistor 125, are integrated into one power resistor 112 in this Patent Document 1. , To reduce component prices and facilitate component mounting.

  In the inverter power supply circuit of FIG. 2, when the input current bypass switch 103 is turned off at the time of turning on the power in order to suppress the inrush current, the current from the rectifier 102 is represented by the dashed line arrow A in FIG. As shown, all the current from the rectifier 102 flows through the power resistor 112 via the inrush current inflow diode 113, and the inrush current is suppressed by the power resistor 112. Here, an inrush current suppression circuit is configured with the input current bypass switch 103, the power resistor 112, and the inrush current inflow diode 113 as the center.

  The input current bypass switch 103 is turned on from when the power is turned on until the motor 108 is rotated by the inverter 106 after the charging current of the smoothing capacitor 105 is reduced. As a result, the inrush current inflow diode 113 and the power resistor 112 are bypassed by the input current bypass switch 103, and DC power is directly supplied from the rectifier 102 to the inverter 106 and the smoothing capacitor 105.

  Next, in order to drop the voltage due to the regenerative power accumulated in the smoothing capacitor 105, the voltage absorption switch 109 and the power resistor 112 constitute a voltage absorption circuit.

  At the time of voltage absorption, the voltage absorption switch 109 is turned on. Then, as indicated by a two-dot chain line arrow B in FIG. 2, a current due to the electric charge accumulated in the smoothing capacitor 105 flows through the power resistor 112 and is discharged, and the voltage of the smoothing capacitor 105 drops. At the same time, as indicated by the two-dot chain line arrow B, the current due to the regenerative power from the inverter 106 also flows into the power resistor 112, thereby suppressing charging of the smoothing capacitor 105.

  Here, in order to suppress the inrush current in the inverter power supply circuit, it is necessary to detect “power on” by some circuit and operate the switching element for suppressing the inrush current. For example, it is necessary to turn off the input current bypass switch 103 in the inverter power supply circuit of FIG. 1 and to turn off the input current bypass switch 103 in the inverter power supply circuit of FIG.

  In addition, in order to perform a voltage absorption operation in the inverter power supply circuit, a certain circuit detects “increase in accumulated charge” of the smoothing capacitor due to regenerative power and “voltage increase” due to increase in the accumulated charge. It is necessary to operate the switching element for the absorption operation. For example, the voltage absorption switch 124 needs to be turned on in the inverter power supply circuit shown in FIG. 1, and the voltage absorption switch 109 needs to be turned on in the inverter power supply circuit shown in FIG.

  For example, in Patent Document 2, “power-on” is detected based on the period of the CR time constant of the differentiating circuit, and a period in which an inrush current to be suppressed is generated. Also, during this period, the transistor that bypasses the power resistor for suppressing the inrush current is kept off, and the inrush current is allowed to flow through the power resistor, thereby suppressing the inrush current.

JP-A-8-168250 (FIG. 3) Japanese Patent No. 3564694 (FIG. 5)

  However, such a circuit that performs detection related to inrush current suppression and voltage absorption operation cannot be easily realized.

  For example, also in the above-mentioned Patent Document 2, in the operation of turning on the transistor that bypasses the power resistor for suppressing the inrush current during the period of the CR time constant of the differentiating circuit, and turning on at other times, As described below, questions arise regarding the stable operation. In Patent Document 2, the voltage absorption circuit is not dealt with.

  In Patent Document 2, the gates of the MOS transistors Q1 and Q2 are controlled by a signal from a differential circuit having a CR time constant. However, the source potential of these transistors is different from the ground potential of the CR time constant differentiating circuit, and it is necessary to design in consideration of the transient change of the voltage between these potentials. In particular, when the inrush current suppression circuit is activated, the MOS transistor Q1 is in an OFF state, and a large voltage from the power input 1 is applied to C8, R5, and Q2 as they are, so that protection against reverse charging of C8 is performed. In addition, a large resistance value is required for the resistance of R5, and a large value of the wattage of the resistance is required. In addition, when regenerative power in the motor drive increases the voltage of C1 rapidly, after Q1 is turned off once, The case where it turns ON is also considered. At this time, since the gate charge time constant of Q1 is large, it is necessary to consider the turn-on time of Q1.

  Alternatively, attention must be paid even when the power input 1 is momentarily interrupted, and a design for any transient change is required.

  Next, as described above, in Patent Document 1, two power resistors whose rated power tends to increase are concentrated in one power resistor 112 to reduce the component price and facilitate component mounting. Excellent in terms. However, the period in which the power resistor 112 is actually used is only the initial period when the power is turned on to suppress the inrush current and the period in which the voltage absorption operation is performed. Thus, the usage period is short and the power resistance is reduced. It cannot be said that 112 is fully utilized.

  Further, this Patent Document 1 does not disclose what circuit is used to turn on / off the input current bypass switch 103 and the voltage absorption switch 109. Furthermore, since the source potential of the voltage absorption switch 109 is in a state where the potential has floated from the minus of the rectifier 102, a circuit that gives a signal to the gate of the voltage absorption switch 109 needs to consider such a circuit state.

  In the inverter power supply circuit of FIG. 1 as well, the input current bypass switch 103 and the voltage absorption switch 124 are not disclosed for on / off in the same manner.

  The present invention is for solving the above-mentioned conventional problems, and is an inverter that can reliably perform inrush current suppression and regenerative capacitor voltage rise suppression operation with a relatively inexpensive and easy-to-mount circuit. It is an object of the present invention to provide a power supply circuit.

  The present invention provides an inverter power supply circuit in which DC input power is smoothed by a capacitor and output to an inverter circuit, and regenerative power from the inverter is stored in the capacitor. A power resistor for suppressing the inrush current generated when the input power is input, a power resistor for discharging the accumulated charge of the capacitor in order to suppress a voltage increase due to charging of the capacitor by regenerative power, and a plus The first internal power supply is used in a bootstrap power supply circuit that generates and supplies a primary internal power supply different from the positive and negative direct current input power from the direct current input power. At least part of the resistance of each of these three power resistors with the power resistor for stabilizing the output voltage, One of the well as sharing the shared power resistors, one of the two terminals of the co power resistance, by being connected to the negative of the DC input power, is obtained by solving the above problems.

  Here, both the positive and negative potentials are power supplies different from the positive and negative of the DC input power, and are different from the positive and negative of the primary internal power supply of the bootstrap power supply circuit. A secondary bootstrap power supply circuit may be provided that generates and supplies secondary internal power supply from power supplied by the bootstrap power supply circuit.

  According to the present invention, the power resistor shared by the inrush current suppression circuit and the voltage absorption circuit can be further shared by the power resistor for stabilizing the output voltage in the bootstrap power supply circuit. Thus, the power resistor can be effectively used. A signal for operating the switching element of the inrush current suppression circuit and the voltage absorption circuit can be generated by using this bootstrap power supply circuit. Therefore, inrush current suppression and voltage absorption operation can be reliably performed by a circuit that is relatively inexpensive and easy to mount.

  Since the positive and negative DC power supplied from the bootstrap power supply circuit are different from the positive and negative DC powers on the input side supplied to the bootstrap power supply circuit, they are floating potentials. Can be easily generated and the options for the power element can be expanded. For example, an inexpensive N-channel power element can be used. For example, N-channel IGBTs and MOSFETs that are relatively inexpensive and have many options can be employed.

Circuit diagram of a conventional general inverter power supply circuit Circuit diagram showing power supply circuit for inverter of Patent Document 1 1 is a circuit diagram including a power supply circuit for an inverter according to a first embodiment to which the present invention is applied. The circuit diagram containing the power supply circuit for inverters of 2nd Embodiment to which this invention was applied Time chart showing operation of the second embodiment An enlarged time chart of the main part of the above time chart The circuit diagram containing the power supply circuit for inverters of 3rd Embodiment to which this invention was applied A first circuit diagram including an inverter power supply circuit according to a fourth embodiment to which the present invention is applied. Second circuit diagram including the inverter power supply circuit of the fourth embodiment.

  FIG. 3 is a circuit diagram including the inverter power supply circuit of the first embodiment to which the present invention is applied.

  The inverter power supply circuit of the present embodiment includes a rectifier 102 that rectifies AC power supplied from an external three-phase or single-phase AC power supply 101 into DC, and a smoothing capacitor 105 that removes pulsating flow of rectified DC power. And an inrush current suppression circuit and a voltage absorption circuit. The smoothing capacitor 105 is also used for accumulating charges of regenerative power from the inverter.

  Further, a control power supply 114 and a control voltage smoothing capacitor 115 for supplying DC power to the voltage absorption circuit and others, and a bootstrap power supply circuit (charge pump circuit) using the control power supply 114 as a power supply are configured. A bootstrap diode 117 for supplying power and a control voltage smoothing capacitor 118;

  The inrush current suppression circuit includes an input current bypass switch 103 that is a transistor having diodes connected in parallel, a control unit 116, an inrush current inflow diode 113, and a power resistor 112. The controller 116 monitors the voltage between point A and point B, or the voltage between point C and point D, and detects a decrease in inrush current after power-on. In addition, the control unit 116 outputs an H state when the voltage to be monitored becomes equal to or higher than a preset voltage as the rush current decreases. The input current bypass switch 103 is turned on by the output in the H state.

  The voltage absorption circuit includes a voltage absorption switch 109 which is a transistor that is turned on when performing a voltage absorption operation, a control unit 119, and a power resistor 112. The control unit 119 monitors the voltage between the point A and the point B or the voltage between the point C and the point D, and as a result, the charge of the regenerative power is stored in the smoothing capacitor 105 and the voltage increases. Then, it is determined whether or not the value is equal to or higher than a set value at which the voltage absorption operation should be performed. When the control unit 119 determines that the voltage absorption operation should be performed, the control unit 119 outputs an H state and turns on the voltage absorption switch 109.

  In the present embodiment as described above and also in the second to fourth embodiments described later, the power resistor 112 is shared in the three circuits of the inrush current suppression circuit, the voltage absorption circuit, and the bootstrap power supply circuit. Yes.

  Here, the power resistance for stabilizing the output voltage of the bootstrap power supply circuit is such a resistance value that a voltage drop can be ignored even when a bootstrap current (output current of power supply from the bootstrap power supply circuit) flows. There must be a value of about 100 [Ω] or less. Also, since the power resistance tends to increase the rated power, it is possible to reduce the component price and the component mounting space by sharing with other circuits.

  In this embodiment, in order to suppress the inrush current, the input current bypass switch 103 is turned off when the power is turned on. Then, all the current from the rectifier 102 flows through the power resistor 112, and the inrush current is suppressed by the power resistor 112. In the present embodiment, an inrush current suppression circuit is configured around the input current bypass switch 103, the power resistor 112, and the inrush current inflow diode 113.

  The input current bypass switch 103 is turned on from when the power is turned on until the motor 108 is rotated by the inverter 106 after the charging current of the smoothing capacitor 105 is reduced. Thus, the inrush current inflow diode 113 and the power resistor 112 are bypassed by the input current bypass switch 103, and direct current power is directly supplied from the rectifier 102 to the inverter 106 and the smoothing capacitor 105.

  Next, in this embodiment, a voltage absorption circuit is configured by the voltage absorption switch 109 and the power resistor 112 in order to perform a voltage absorption operation. In the present embodiment, the smoothing capacitor 105 accumulates the charge of regenerative power from the inverter 106.

  In this voltage absorption operation, the voltage absorption switch 109 is turned on. Then, as indicated by a two-dot chain line arrow B in FIG. 3, a current due to the accumulated charge of the smoothing capacitor 105 flows through the power resistor 112 and is discharged, and the voltage of the smoothing capacitor 105 drops. At the same time, as indicated by the two-dot chain line arrow B, the current due to the regenerative power from the inverter 106 also flows to the power resistor 112, and charging of the smoothing capacitor 105 is suppressed.

  Here, the input current bypass switch 103 and the voltage absorption switch 109 have different source potentials from the negative potential of the smoothing capacitor 105. Therefore, this point needs to be taken into consideration in a circuit that generates signals to be supplied to these gates.

  For this reason, this embodiment includes a control power supply 114 that uses a DC stabilized power supply for generating a DC voltage of plus 15 volts with reference to point B in the figure. Further, as indicated by a broken line arrow C in the figure, a current flows from the control power source 114 to the control voltage smoothing capacitor 115, whereby the control voltage smoothing capacitor 115 is connected to the DC power source supplied from the control power source 114. Suppresses pulsating flow. In the control voltage smoothing capacitor 115, as shown in the figure, the voltage is V1 (= 15v).

  Next, the control voltage smoothing capacitor 118 is supplied with DC power from the control power supply 114 via the bootstrap diode 117. In this power supply, as indicated by the broken line arrow D in the figure, the current flows in the order of the output U terminal of the control power supply 114, the bootstrap diode 117, the control voltage smoothing capacitor 118, the power resistor 112, and the negative terminal of the control power supply 114. Flowing. Therefore, the control voltage smoothing capacitor 118 becomes the voltage V2 as shown.

  The power source of the voltage V1 and the power source of the voltage V2 are supplied to the control unit 116 and the control unit 119. The control unit 116 and the control unit 119 generate signals for turning on / off the input current bypass switch 103 and the voltage absorption switch 109, respectively.

  Here, the control voltage smoothing capacitor 118 of the bootstrap power supply circuit is charged with a current flowing from the control voltage smoothing capacitor 118 to the power resistor 112. This current increases during an idle period when the inrush current suppression circuit and the voltage absorption circuit are not operating. Therefore, the power resistor 112 is effectively used in the bootstrap power supply circuit together with the inrush current suppressing circuit and the voltage absorbing circuit. In addition, the power resistor 112 is usually several Ω to several tens Ω, and thus is a sufficiently small value for charging the control voltage smoothing capacitor 118.

  The load of the control voltage smoothing capacitor 118 is the control unit 119 and the voltage absorption switch 109. Further, the voltage absorption operation works for a very short period of about 10 ms, for example, and the load on the control voltage smoothing capacitor 118 becomes small. The load current of the control voltage smoothing capacitor 118 is, for example, about several mA to several tens mA.

  However, since the charge of the control voltage smoothing capacitor 118 is discharged as the voltage absorption operation is prolonged, for example, when the voltage absorption operation continues for 100 ms or more, a protective function such as turning off the voltage absorption switch 109 may be provided. preferable. Such a protection function can be realized in the control unit 119 as necessary.

  In the present embodiment, the control power supply 114 is provided as a plus 15 volt DC power supply, and this causes a cost burden. However, the control power supply 114 can be effectively used by being used for a fan motor that cools the substrate on which the inverter power supply circuit of the present embodiment is mounted, or for other peripheral circuits via a connector. In a fourth embodiment to be described later, power is also supplied from the control power supply 114 to the power transistor control unit 144 inside the inverter 106.

  Here, in this embodiment, since the power resistor 112 is shared by the three circuits of the inrush current suppression circuit, the voltage absorption circuit, and the bootstrap power supply circuit, the resistance value is the least common multiple in these circuits. It is determined. For this reason, if the resistance value of the power resistor 112 is set to a value preferable for operation in the inrush current suppression circuit and the bootstrap power supply circuit, the resistance value of the power resistor 112 may be small as a value in the voltage absorption circuit. . Or the case where it is large as a value in a voltage absorption circuit is also considered.

  When the value in the voltage absorption circuit is small, according to the second embodiment described below, the resistance value of the power resistor that is insufficient as the voltage absorption circuit can be compensated, and the voltage absorption operation can be suppressed. Also, according to the third and fourth embodiments described below, on the contrary, when the resistance value of the power resistor is too large as a voltage absorption circuit, the voltage absorption operation is improved so as to eliminate the surplus. be able to.

  FIG. 4 is a circuit diagram including an inverter power supply circuit according to a second embodiment to which the present invention is applied.

  In the present embodiment, a power resistor 120 and a surge absorbing diode 127 are added as part of the voltage absorbing circuit to the first embodiment described above.

  Here, if the power resistor 112 is shared by three circuits, the inrush current suppression circuit, the voltage absorption circuit, and the bootstrap power supply circuit, the resistance value of the power resistor 112 may be small as a value in the voltage absorption circuit. In this case, in this embodiment, the shortage of the resistance value can be compensated by the power resistor 120. In the case where the power resistor 120 is provided, heat (power consumption) generated in the power resistor 112 at the time of a voltage drop can be distributed to the power resistor 120.

  Next, FIG. 5 is a time chart showing the operation of this embodiment, and FIG. 6 is an enlarged time chart of the main part.

  In these figures, the upper part is the current flowing through the input current bypass switch 103, and the lower part is the voltage across the smoothing capacitor 105. 6 is an enlarged view of the section T in FIG.

In FIG. 6, periods t1 to t5 are a motor acceleration period, a motor constant speed period, a motor deceleration period, a motor deceleration (with voltage absorption operation) period, and a motor stop period, respectively. These periods t1 to t5 correspond to one-cycle operation in which the rotation of the motor accelerates from the stopped state to the constant speed state, and then decelerates to the stopped state again.

  A negative current flows through the input current bypass switch 103 during the voltage absorption operation period of the section t4 in FIG. This indicates that the diode parallel to the input current bypass switch 103 flows in the forward direction. For this reason, the input current bypass switch 103 needs to be able to flow a current from the emitter (source) to the collector (drain) during voltage absorption. It is preferable to use an IGBT with a built-in diode, a MOSFET capable of conducting in the reverse direction, or the like as the input current bypass switch 103 because an external diode in parallel can be omitted.

  FIG. 7 is a circuit diagram including an inverter power supply circuit according to a third embodiment to which the present invention is applied.

  As shown in the figure, this embodiment is obtained by adding a power resistor 161 and a voltage absorption current inflow diode 162 to the first embodiment of FIG. 3 described above, and the second embodiment of FIG. 4 described above. On the contrary, the voltage absorption operation is improved. That is, in the first embodiment and the second embodiment described above, when the voltage absorption capability of the voltage absorption circuit is insufficient, the present embodiment only adds the power resistor 161 and the voltage absorption current inflow diode 162. It is possible to enhance the voltage absorption capability.

  In the voltage absorption operation, the voltage absorption switch 109 is turned on. Then, as illustrated by a two-dot chain line arrow B in FIG. 7, the current due to the accumulated charge of the smoothing capacitor 105 is added to the power resistor 112 in addition to the power resistor 112 similar to the first embodiment and the second embodiment. And the voltage of the smoothing capacitor 105 drops. At the same time, as indicated by the two-dot chain line arrow B, the current due to the regenerative power from the inverter 106 also flows to the power resistor 161 in addition to the power resistor 112, and charging to the smoothing capacitor 105 is suppressed.

  In addition, in this embodiment, by adding the voltage absorption current inflow diode 162, when the inrush current is suppressed, this inrush current can be prevented from flowing to the power resistor 161, and the current value of the two-dot chain line arrow A is shown. Can be prevented from affecting.

  Furthermore, the added power resistor 161 also serves as a path for passing a current for charging the control voltage smoothing capacitor 118 of the bootstrap power supply circuit, and the voltage stability of the bootstrap power supply circuit can be improved. That is, charging to the control voltage smoothing capacitor 118 is performed by charging the control voltage smoothing capacitor 118 through the voltage absorption current inflow diode 162 and the power resistor 112 and charging the control voltage smoothing capacitor 118 through the power resistor 161. Therefore, the bootstrap power supply circuit with a more stable voltage to be supplied can be realized by adding the power resistor 161.

  8 and 9 are circuit diagrams including the inverter power supply circuit according to the fourth embodiment to which the present invention is applied.

  8 is the left side of the circuit, and FIG. 9 is the right side. FIG. 8 and FIG. 9 are divided into two parts for convenience of drawing. 8 and 9, the control voltage smoothing capacitor 122, the control unit 123, the voltage absorption switch 124, the power resistor 125, the surge absorption diode 126, and the current limiting resistor 129 are easily understood in the connection between these two diagrams. As shown in FIG.

  In the present embodiment, a part of the voltage absorption circuit is added to the above-described second embodiment. This additional circuit includes a bootstrap power supply circuit different from that of the second embodiment or the first embodiment. In this embodiment, power is also supplied to the inverter 106 from the added bootstrap power supply circuit. Further, three bootstrap power supply circuits are also formed in the inverter 106.

  First, a circuit added to a part of the voltage absorption circuit in the present embodiment will be described.

  In the voltage absorption circuit of this embodiment, a voltage absorption switch 124, a power resistor 125, and a surge absorption diode 126 are added. Further, a control unit 123 that gives a signal to the gate of the voltage absorption switch 124, and the control unit 123 A bootstrap diode 121 and a control voltage smoothing capacitor 122 constituting a bootstrap power supply circuit for supplying a DC power supply, and a current limiting resistor 129 for stabilizing the voltage of the power supply supplied from the bootstrap power supply circuit are added. The

  The current limiting resistor 129 stores the regenerative electric power in the smoothing capacitor 105 and the voltage rises. When the potential difference between the points CD and the potential difference between the points AB changes rapidly, the current limiting resistor 129 The voltage of the capacitor 115 and the voltage of the control voltage smoothing capacitor 122 are stabilized, and thus the power supply voltage supplied from the control voltage smoothing capacitor 115 and the control voltage smoothing capacitor 122 is stabilized.

  The control unit 123 monitors the voltage between the point A and the point B or the voltage between the point C and the point D, the electric charge of regenerative power is stored in the smoothing capacitor 105, the voltage rises, and the voltage is absorbed. It is determined whether or not the set value to be operated is exceeded, and if it is determined that the voltage absorption operation should be performed, the H state is output and the voltage absorption switch 124 is turned on. Then, as indicated by a two-dot chain line arrow B ′ in FIGS. 8 and 9, a current due to the accumulated charge of the smoothing capacitor 105 flows through the power resistor 125 and is discharged, and the voltage of the smoothing capacitor 105 drops. At the same time, as indicated by the two-dot chain line arrow B ', the current due to the regenerative power from the inverter 106 also flows to the power resistor 125, and charging of the smoothing capacitor 105 is suppressed.

  In the first embodiment and the second embodiment described above, when the voltage absorption capability of the voltage absorption circuit is insufficient, the above circuit for supplying a current of regenerative power to the power resistor 125 is further absorbed by the voltage absorption circuit as in this embodiment. Add to the circuit. If the voltage absorption switch 124 is also turned on when the voltage absorption switch 109 is turned on, the power resistor 125 can be operated in parallel with the power resistor 112 with respect to the smoothing capacitor 105 and the inverter 106. The electric power resistor 125 can absorb the electric charge stored in the smoothing capacitor 105 and the regenerative electric power from the inverter 106, and can play a role of increasing the amount of current at the time of voltage absorption.

  Here, in the present embodiment, the control unit 116 or the like uses the control voltage smoothing capacitor 115, and the point B is the reference potential. On the other hand, the control unit 123 that outputs a signal to the gate of the voltage absorption switch 124 needs to use the point D on the minus side of the smoothing capacitor 105 as a reference potential, and a control power supply for this is required. .

  Therefore, the control power is supplied by a bootstrap power supply circuit using the bootstrap diode 121 and the control voltage smoothing capacitor 122. In this bootstrap power supply circuit, as indicated by a broken line arrow E in the figure, the control voltage is controlled by a circuit that makes a circuit in the forward direction of the bootstrap diode 121, the current limiting resistor 129, the control voltage smoothing capacitor 122, and the input current bypass switch 103. By charging the smoothing capacitor 122, a control power supply for the floating potential point D is obtained at both ends of the control voltage smoothing capacitor 122 as shown as a voltage V 3.

  Here, the input current bypass switch 103 is always turned on except when the inrush current is suppressed. In addition, when an overcurrent flows from the input side due to an external surge or the like, the input current bypass switch 103 may be blocked by the control unit 116. The input current bypass switch 103 is also interposed in the above-described bootstrap power supply circuit. Therefore, when the switch is turned off, charging of the control voltage smoothing capacitor 122 is hindered. However, if necessary for protection, each of the control unit 116, the control unit 119, and the control unit 123 may be provided with a low voltage protection function.

  Here, as the voltage absorption switch 124, the power resistor 125, and the surge absorption diode 126 of the present embodiment, a transistor, a power resistor, or a surge absorption diode that is often built in a power module for an inverter can be used as a brake. . On the other hand, if the bootstrap diode 121, the control voltage smoothing capacitor 122, and the control part 123 are added, a voltage absorption circuit can be comprised comparatively easily.

  Next, in the present embodiment, six powers including a control unit 145 are provided in the inverter 106 from the bootstrap power supply circuit added to the voltage absorption circuit using the bootstrap diode 121 and the control voltage smoothing capacitor 122. Power is also supplied to the transistor control units 144a to 144f.

  Of these power transistor control units 144a to 144f, three power transistor control units 144d to 144f (for the lower three-phase arm) are respectively connected to the gates of the power transistors 150d to 150f (for the lower three-phase arm). Although the input signal is output, the sources of these power transistors 150d to 150f have the same potential as the negative terminal of the control voltage smoothing capacitor 122 described above. Accordingly, power is directly supplied to the three power transistor control units 144d to 144f from the bootstrap power supply circuit using the control voltage smoothing capacitor 122.

  On the other hand, among the power transistor control units 144a to 144f, the remaining three power transistor control units 144a to 144c (for the upper three-phase arm) are gates of the power transistors 150a to 150c (for the upper three-phase arm), respectively. The power transistors 150a to 150c have different potentials from each other, and also have different potentials from the negative terminal of the control voltage smoothing capacitor 122 described above. Accordingly, each of these three power transistor control units 144a to 144c is provided with one bootstrap power supply circuit to supply power, thereby individually setting the reference potential (minus side potential) of the power supply.

  That is, as shown in FIG. 9, an individual bootstrap power supply circuit using bootstrap diodes 140a to 140c and control voltage smoothing capacitors 142a to 142c is provided for each of the three power transistor control units 144a to 144c. Supply power. As described above, in this embodiment, three independent bootstrap power supply circuits are also formed in the inverter 106. For example, from the bootstrap power supply circuit using the bootstrap diode 140a and the control voltage smoothing capacitor 142a, the power supply of the voltage V4a can be supplied as shown in FIG. The three bootstrap power supply circuits are supplied with power from the bootstrap power supply circuit using the control voltage smoothing capacitor 122.

  Here, in this embodiment, two power transistors 150 are provided corresponding to each phase of the three-phase motor 108. A power transistor controller 144 is provided for each power transistor 150. In the inverter 106, the power transistor control unit 144 controls the current flowing through the power transistor 150 to control the voltage and frequency of AC power supplied to the motor 108.

  Further, since each power transistor control unit 144 that controls the power transistor 150 corresponding to each phase operates with the power supply from the bootstrap power supply circuit, the floating potential for driving the gate of these power transistors 150 is generated. It is easy to do and can improve the freedom degree of design.

DESCRIPTION OF SYMBOLS 101 ... AC power supply 102 ... Rectifier 103 ... Input current bypass switch 104 ... Inrush current suppression resistance 105 ... Smoothing capacitor 106 ... Inverter 108 ... Motor 109, 124 ... Voltage absorption switch 112, 125, 161 ... Power resistance 113 ... Inrush current inflow diode 114: Control power supply 115, 118, 122, 142 ... Control voltage smoothing capacitor 116, 119, 123, 145 ... Control unit 117, 121, 140 ... Bootstrap diode 129 ... Current limiting resistor 144 ... Power transistor control unit 150 ... Power transistor 162. Voltage absorbing current inflow diode

Claims (2)

In the inverter power supply circuit in which the DC input power is smoothed by the capacitor and output to the inverter circuit, and the regenerative power from the inverter is stored in the capacitor.
A power resistor for suppressing an inrush current generated when the DC input power is applied in a state where the accumulated charge of the capacitor is small;
In order to suppress a voltage increase due to charging of the capacitor due to regenerative power, a power resistor for discharging the accumulated charge of the capacitor;
The primary internal power supply used in a bootstrap power supply circuit that generates and supplies a primary internal power supply that is different from the positive and negative of the DC input power from both the positive and negative potentials. With power resistance to stabilize the output voltage of
While sharing at least a partial resistance of each of these three power resistors with one shared power resistor,
One of the terminals of the shared power resistor is connected to the minus of the DC input power, and the inverter power supply circuit. In the inverter power supply circuit according to claim 1,
Both the positive and negative potentials are power supplies different from the positive and negative of the DC input power, and the secondary internal power different from the positive and negative of the primary internal power supply of the bootstrap power supply circuit. A power supply circuit for an inverter, comprising a secondary bootstrap power supply circuit that generates and supplies power from power supplied by the bootstrap power supply circuit.

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