JPH07203681A - Method and circuit for suppressing harmonics in power supply for inverter - Google Patents

Abstract

PURPOSE:To prevent reverse current flow from a diode to a semiconductor switch by providing means for interrupting the current for a predetermined time on the input side of the diode thereby interrupting the input to the diode upon turn ON of the semiconductor switch. CONSTITUTION:Upon turn ON of a semiconductor switch 4, current of a power supply circuit flows from a reactance 5 to the semiconductor switch 4 side and upon turn OFF of the semiconductor switch 4, the current flows from the reactor 5 to the recovery diode 6 side. Upon turn ON of the semiconductor switch 4, a switch 10 is turned OFF. A reverse current is generated upon turn OFF of the semiconductor switch 4, but since the switch 10 is turned OFF, the reverse current does not flow into the semiconductor switch 4. Since the diode recovery current does not flow into the semiconductor switch 4 the semiconductor switch 4 is protected against damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter power source harmonic suppression method and circuit for suppressing power source harmonics in inverter equipment used in air conditioners and the like.

[0002]

2. Description of the Related Art In this type of inverter device, when a DC power supply required for inverter control is obtained, in order to suppress harmonic current (power supply harmonics) due to distortion of an input AC current, for example, a booster shown in FIG. Some have adopted the chopper method.

In FIG. 3, the booster chopper type power supply circuit is a rectifier circuit 2 for rectifying a commercial AC power supply 1 into a DC voltage, and a capacitor 3 for smoothing the rectified DC voltage.
A semiconductor switch (transistor; IGBT) 4 that forms an active filter and chops the smoothed DC voltage; a reactor 5 for power factor improvement; a recovery diode (FRD) 6 for blocking reverse current; And a control unit 8 for turning on and off the semiconductor switch 4 in a predetermined manner so that the input AC current waveform from the AC power supply becomes a substantially sine wave, and the DC voltage obtained by this step-up chopper method is converted into an inverter. Use the DC power supply for equipment (including load 9). FRD is FastRecover
Abbreviation for y Diode (high-speed lecturer).

In the power supply circuit having the above-mentioned configuration, the input AC current waveform is made substantially a sine wave, so that power supply harmonics can be suppressed, and the ON time of the semiconductor switch 4 is varied to output the output. The DC voltage can be constant. When applied to an air conditioner, for example, on the load 9 side, a DC voltage from the power supply circuit is switched in a predetermined manner in the inverter unit, and this switched voltage is applied to the winding of the motor of the compressor.

[0005]

By the way, in the power supply circuit of the above-described inverter device, as shown in FIG. 4, when the semiconductor switch 4 is turned on, the reverse current from the recovery diode 6 (diode recovery current; A reverse recovery current) momentarily flows through the semiconductor switch 4, and the reverse current may damage the semiconductor switch 4.

That is, at the moment when the semiconductor switch 4 is switched from off to on, a large diode recovery current flows through the semiconductor switch 4 in 100 nsec, for example. In particular, in the case of a high power type such as an air conditioner, the diode recovery current is larger and the semiconductor switch 4 may be damaged.

The present invention has been made in view of the above problems, and an object thereof is to damage a semiconductor switch constituting an active filter used in a power supply circuit of an inverter device,
It is an object of the present invention to provide a method of suppressing power source harmonics of an inverter device and a circuit thereof that can prevent damage.

[0008]

In order to achieve the above object, the present invention is capable of short-circuiting the output of the rectifying means through a reactor when rectifying the AC power source by the rectifying means to obtain a DC power source for an inverter device. The semiconductor switch means of the active filter is turned on and off in a predetermined manner, and when the semiconductor switch means is turned off, a current flows from the reactor to the forward diode, while when the semiconductor switch means is turned on, the current from the reactor is turned on. To the diode,
A method for suppressing power source harmonics of an inverter device, wherein an input AC current waveform is substantially a sine wave, the input side of the diode having a breaking means for cutting off a current for a predetermined time, and the semiconductor switching means is turned on from off. In that case, the gist is that the input of the diode is cut off by the breaking means so that a reverse current from the diode does not flow to the semiconductor switch.

[0009]

Since the above means is adopted, in order to suppress power source harmonics, the semiconductor switch means is turned on and off at a predetermined time, and the current from the reactor is alternately passed through the semiconductor switch means and the diode (recovery diode) to supply an alternating current power supply. The input AC current waveform of is almost a sine wave, but at this time, when the input of the diode is turned on from the off state of the semiconductor switch means, it is cut off for a predetermined time.

Therefore, at the moment when the semiconductor switch means is turned on, the diode recovery current (reverse current) is generated.
Does not flow into the semiconductor switch, and damage and damage to the semiconductor switch can be prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a diode for reverse current blocking at the moment when a semiconductor switch which constitutes an active filter is switched from OFF to ON in a power supply harmonic suppression circuit of an inverter device adopting a step-up chopper system or the like. Since the same semiconductor switch is damaged or damaged by the reverse current (diode recovery current; reverse recovery current) from the recovery diode (FRD), it suffices to cut the reverse current. Focusing on the fact that the current does not have to flow to the diode side, when the semiconductor switch turns from OFF to ON, the current is cut off to the input side of the diode to prevent the reverse current from the diode from flowing to the semiconductor switch. It has a shut-off means.

Therefore, as shown in FIG. 1, the power supply harmonic suppression circuit of this inverter device includes a switch (breaking means; transistor) 10 provided on the input side of the recovery diode (FRD) 6 behind the semiconductor switch 4. , Fig. 3
The control unit 11 has the function of the control unit 8 shown in FIG. 3 and includes a control unit 11 that controls the switch 10 to turn on and off in the opposite phase to the on / off control of the semiconductor switch 4.

In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals, and the duplicated description will be omitted. Further, the booster chopper type power supply circuit shown in FIG. 1 may have other necessary circuits.

Next, the operation of the power supply harmonic suppression circuit of the inverter device having the above configuration will be described in detail with reference to the time chart of FIG. 2. First, for example, the load 9 of the compressor motor of the air conditioner is inverter-controlled. Control unit 1 of the power supply harmonic circuit in the power supply circuit that outputs DC power supply to the inverter unit
Reference numeral 1 controls the semiconductor switch 4 to be turned on and off in a predetermined manner so that the input AC current waveform becomes a substantially sine wave. This allows
As is well known, it is possible to suppress the harmonic current, and thus suppress the harmonic component contained in the output of the inverter.

At this time, when the semiconductor switch 4 is turned on, the current of the power supply circuit flows from the reactor 5 to the semiconductor switch 4
When the semiconductor switch 4 is turned off, the current flows from the reactor 5 to the recovery diode 6 side. However, the control unit 11 outputs the control signal S1 for controlling the on / off of the semiconductor switch 4 (shown in FIG. 2A), while the control signal S2 for controlling the on / off of the switch 10.
Is output (shown in FIG. 7B). Moreover, as shown in FIGS. 2A and 2B, the control signal S1 and the control signal S2 are
It is in the opposite phase from.

As a result, when the semiconductor switch 4 is switched from off to on, the switch 10 is switched from on to off. A reverse current is generated at the moment when the semiconductor switch 4 is switched from off to on, but since the switch 10 is off, the reverse current does not flow to the semiconductor switch 4.

As described above, in the power supply harmonic suppression circuit, the diode recovery current (about 100 nsec)
Does not flow to the semiconductor switch 4, the damage to the semiconductor switch 4 can be prevented, and the damage to the semiconductor switch 4 can be prevented especially when the semiconductor switch 4 is used in an inverter device of an air conditioner with large power consumption. it can.

As a method for controlling the switch 10 to be turned on and off, when the semiconductor switch 4 is turned on, the switch 10 is turned off for a time (maximum time) during which a reverse current (diode recovery current; reverse recovery current) flows. May be set.

Further, since it is possible to prevent the reverse current from the recovery diode 6 from flowing to the semiconductor switch 4, the switching frequency of the semiconductor switch 4 can be made high, and the recovery diode 6 is, for example, 100 nsec or less. Therefore, the recovery diode 6 can be easily selected.

[0020]

As described above, according to the present invention, when the AC power source is rectified by the rectifying means to obtain the DC power source for the inverter equipment, the output of the rectifying means can be short-circuited via the reactor. The semiconductor switch means of the filter is turned on and off in a predetermined manner, and when the semiconductor switch means is turned off, a current is passed from the reactor to the forward diode, while when the semiconductor switch means is turned on, a current is passed from the reactor to the diode, A method for suppressing power source harmonics in an inverter device that makes an input AC current waveform a substantially sine wave, and a circuit therefor, having a cutoff means for cutting off a diode input for a predetermined period of time, the moment when a semiconductor switch is switched from off to on In addition, the blocking means prevents the reverse current from the diode from flowing to the semiconductor switch. Damage of the switch, damage can be prevented, there is an effect that it leads to an improvement in reliability.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a power supply harmonic suppression circuit for an inverter device showing an embodiment of the present invention.

FIG. 2 is a schematic time chart diagram for explaining the operation of the power supply harmonic suppression circuit shown in FIG.

FIG. 3 is a schematic circuit diagram of a power supply circuit (including a power supply harmonic suppression circuit) of a conventional inverter device.

FIG. 4 is a schematic graph illustrating the operation of the power supply circuit shown in FIG.

[Explanation of symbols]

 1 Commercial AC Power Supply 2 Rectifier Circuit 3 Capacitor 4 Semiconductor Switch (Transistor; IGBT) 5 Reactor 6 Recovery Diode (FRD; High Speed Lecture) 7 Smoothing Capacitor 9 Load 10 Switch (Cut Off Means; Transistor) 11 Controller S1, S2 Control Signal

Claims (3)

[Claims] 1. When rectifying an AC power supply with a rectifying means to obtain a DC power supply for an inverter device, a semiconductor switch means of an active filter that can short-circuit the output of the rectifying means via a reactor is turned on and off as required. When the semiconductor switch means is off, a current is passed from the reactor to the forward diode, while when the semiconductor switch means is on, a current from the reactor is passed to the diode.
A method for suppressing power source harmonics of an inverter device, wherein an input AC current waveform is substantially a sine wave, wherein the input side of the diode has a breaking means for cutting off a current for a predetermined time, and the semiconductor switch means is turned on from off. In this case, the cutoff means cuts off the input of the diode so that a reverse current from the diode does not flow into the semiconductor switch. 2. When rectifying an alternating current power supply with a rectifying means to obtain a direct current power supply for an inverter device, an active filter semiconductor switch means capable of short-circuiting the output of the rectifying means via a reactor is turned on and off as desired. When the semiconductor switch means is off, the current from the reactor is passed through the recovery diode, while when the semiconductor switch means is on, the current from the reactor is passed through the recovery diode, and the input AC current waveform is almost sinusoidal. A method for suppressing power supply harmonics, wherein the input side of the recovery diode has a switch means for turning on and off in a phase opposite to the on / off control of the semiconductor switch means, and the semiconductor switch means is turned on from off. , The switch means is turned off so that no reverse current flows through the semiconductor switch. Power harmonic suppression method of an inverter apparatus, characterized in that the. 3. When converting an AC power supply into a DC power supply for an inverter device, an active filter semiconductor switch means for shorting an output of a rectifying means for rectifying the AC power supply via a reactor is turned on and off in a predetermined manner, While the semiconductor switch means is off, the current from the reactor is passed through the recovery diode connected in series with the reactor,
A power supply harmonic suppression circuit for an inverter device in which a current from the reactor is caused to flow through a recovery diode when the semiconductor switch means is turned on, and an input AC current waveform is substantially a sine wave, and a switch means is provided on the input side of the recovery diode. When the ON / OFF control of the switch means is in the opposite phase to the ON / OFF control of the semiconductor switch means, and when the semiconductor switch means is turned from ON to OFF, the switch means is turned OFF and a reverse current is applied to the semiconductor switch. A power supply harmonic suppression circuit for inverter equipment that is characterized in that it does not flow.