JP2001178147A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter realizing reduction in cost and size. SOLUTION: A control means 10 controls the duty of ON/OFF state of a lower arm such that the voltage of a power supply 8 for drive circuit does not drop below a gate drive voltage immediately after turning on commercial power until a first waveform is outputted. Consequently, the capacitance of a power supply filter capacitor 9 for the drive circuit can be reduced and charging current to the capacitors 6a-6c in a charge pump circuit can be suppressed without requiring any resistor for suppressing the inrush current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an inverter device using a charge pump system for a drive circuit of a switching element for generating a pseudo AC waveform output.

[0002]

2. Description of the Related Art In recent years, the use of a charge pump system in an inverter device has made it possible to reduce the size of a power supply for a driving circuit for a switching element.

A conventional inverter device using a charge pump system will be described below.

In FIG. 3, 1 is a DC voltage source, 2a to 2a
f is a switching element, and 3a to 3c are driving circuits for driving a switching element (hereinafter referred to as an upper arm) connected to the positive side of the DC voltage source 1, and drive circuit via an inrush current suppressing resistor 5a and a diode 4a. A predetermined voltage is charged in a capacitor 6a serving as a power supply of 3a. Similarly, capacitors 6b and 6c are connected to inrush current suppressing resistors 5b and 5c.
c and the diodes 4b and 4c. At this time, the charging current to the capacitor 6a is suppressed by the inrush current suppression resistor 5a. Reference numeral 3d denotes a drive circuit for driving a switching element 2d (hereinafter referred to as a lower arm) connected to the negative side of the DC voltage source 1. 7 is a drive circuit 3a
8 is a power supply for a drive circuit,
Reference numeral 9 denotes a power supply smoothing capacitor for the drive circuit.

[0005] Although not shown, the inrush current suppressing resistor may combine its functions into one.

In the inverter device configured as described above, the switching elements 2a and 2d are connected to the DC voltage source 1 in a bridge-like manner, and the DC voltage output from the DC voltage source 1 is appropriately switched so as to perform predetermined switching. Is output.

The switching element 2 of the upper arm
The driving circuit 3a for driving the inrush current suppressing resistor 5a,
Together with the diode 4a and the capacitor 6a, a charge pump circuit is formed. That is, a predetermined voltage is supplied from the drive circuit power supply 8 to the capacitor 6a via the rush current suppressing resistor 5a and the diode 4a,
Charge a. The drive circuit 3a is driven using the capacitor 6a as a power supply.

The drive circuit 3d for driving the switching element 2d of the lower arm is supplied with a DC power from the drive circuit power supply 8, and thus does not include a diode and a capacitor.

Next, the operation of the inverter device will be described.

When the switching element 2d of the lower arm is first turned on by a predetermined signal from the control circuit, the negative power supply line 7 of the drive circuit 3a of the upper arm has substantially the same potential as the negative potential of the DC voltage source 1. It drops to the potential. At this time, the capacitor 6a of the drive circuit 3a for the upper arm is charged from the drive circuit power supply 8 to almost the same potential as the drive circuit power supply 8 via the rush current suppressing resistor 5a and the diode 4a.

Next, when the switching element 2d of the lower arm is turned off and the switching element 2a of the upper arm is turned on, the potential of the minus power supply line 7 of the driving circuit 3a of the upper arm is changed to a DC voltage. The potential rises to substantially the same potential as the positive potential of the source 1. In this state, the diode 4a is in the backflow preventing state, the electric charge of the capacitor 6a is maintained, and the driving circuit 3a
Power continues to be supplied. As described above, during normal waveform output, the capacitor 6a is automatically charged by PWM switching of the upper arm and the lower arm.

However, immediately after the power is turned on, the capacitor 6a is not sufficiently charged, and its charging current is limited by the inrush current suppressing resistor 5a. It was necessary to always turn on the lower arm for a sufficient time to charge 6a.

[0013]

In the above-mentioned conventional inverter device, the lower arm is continuously turned on in order to charge the capacitor of the charge pump circuit which is the power supply of the drive circuit for the upper arm in the shortest possible time before outputting the waveform. However, an inrush current suppressing resistor for suppressing the charging current of the capacitor was required.

Further, as shown in FIG. 4, the power supply voltage for the driving circuit fluctuates at the same time as the charging of the capacitor 6a is started. In the worst case, the voltage drops below the gate driving voltage level of the switching element, and the function of the inverter stops. There was a problem.

For this reason, the power supply smoothing capacitor 9 for the drive circuit needs a relatively large capacity in order to suppress the voltage fluctuation.

In other words, a space is required for disposing a rush current suppressing resistor and a large power supply smoothing capacitor for a drive circuit, and there are problems in terms of size reduction and cost.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an inexpensive and compact inverter device.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a positive switching element and a negative switching element respectively connected between a positive side and a negative side of a DC voltage generated from a commercial power supply. A plurality of pairs of switching means of a pair of switching elements, a driving circuit for driving the switching elements, a capacitor for a charge pump circuit that is a power supply for the driving circuits for the switching elements connected to the positive side of the DC voltage, A drive circuit power supply for charging the capacitor and a power supply smoothing capacitor for the drive circuit, and ON / OFF of the switching element on the minus side when the pseudo AC waveform is output immediately after the commercial power supply is turned on.
Control means is provided for arbitrarily changing the duty and cycle of the state and suppressing and charging the capacitor of the charge pump circuit without using an inrush current suppressing resistor.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above problems, the present invention relates to a positive side switching element and a negative side switching element connected between a positive side and a negative side of a DC voltage generated from a commercial power supply. A plurality of pairs of switching means composed of elements, a driving circuit for driving the switching element, a capacitor for a charge pump circuit that is a power supply for the driving circuit for the switching element connected to the positive side of the DC voltage, and the capacitor. When a drive circuit power supply for charging and a power supply smoothing capacitor for the drive circuit and a pseudo AC waveform output immediately after the commercial power supply is turned on,
An inverter device comprising control means for arbitrarily changing the duty and cycle of the ON / OFF state of the switching element on the minus side and suppressing and charging the capacitor of the charge pump circuit without using an inrush current suppressing resistor.

The switching element is a MOS-FE
The inverter device according to claim 1, wherein the inverter device is a power switching element having an insulated gate input such as T or IGBT.

As described above, when the pseudo AC waveform is output immediately after the commercial power is turned on, the ON state of the switching element on the minus side,
By arbitrarily changing the duty and cycle of the OFF state, the capacity of the power supply smoothing capacitor for the drive circuit can be reduced, and the rush current suppressing resistor can be eliminated.

Further, when the present invention is used for a power switching element having an insulated gate input, the size can be reduced particularly.

[0023]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a DC voltage source obtained by rectifying a commercial AC power supply, reference numerals 2a to 2f denote insulated gate input switching elements, IGBTs; The capacitor 6a serving as a power supply of the drive circuit 3a is charged with a predetermined voltage via the. The capacitors 6b and 6c are similarly charged via the diodes 4b and 4c, and form a charge pump circuit. Reference numeral 7 denotes a negative power supply line of the drive circuit 3a. 3d to 3f are drive circuits for driving the lower arm switching elements 2d to 2f, 8 is a drive circuit power supply,
Reference numeral 10 denotes a microcomputer of the PWM signal generating means of the control means, and the switching element 2a is connected via the driving circuits 3a to 3f.
信号 2f are turned on and off.

The difference from the conventional example in the configuration is that the charge pump circuit is not provided with an inrush current suppressing resistor and that the control means 10 controls.

In the inverter device of this embodiment, the switching elements 2a to 2f are normally connected in a bridge to the DC voltage source 1, and the DC voltage output from the DC voltage source 1 is appropriately switched to provide a predetermined voltage. Although a pseudo AC waveform is output, the capacitor 6a is not sufficiently charged immediately after the commercial power is turned on, as in the conventional example, and the lower arm must be charged for a sufficient time to charge the capacitor 6a before outputting the waveform. Must be turned ON.

At this time, as shown in FIG. 2, the capacitor 6a is sufficiently charged until the first waveform is output, and the voltage fluctuation of the drive circuit power supply 8 keeps a sufficient margin with respect to the gate drive voltage level. ON state of lower arm, O
The duty in the FF state is controlled.

That is, until the first waveform output, the duty ratio of the ON / OFF state of the lower arm is changed or the duty cycle is changed so that the power supply voltage for the drive circuit is controlled so as not to be lower than the gate drive voltage level. .

As a result, although the charging time is slightly longer in the practical range than in the conventional example, the capacity of the power supply smoothing capacitor for the drive circuit can be reduced, and the capacitor of the charge pump circuit can be used without using an inrush current suppressing resistor. Can be suppressed.

As described above, since a rush current suppressing resistor is unnecessary and the capacity of the power supply smoothing capacitor for the drive circuit can be reduced, it is possible to provide a small and inexpensive inverter device.

Although the present embodiment has been described with respect to an inverter having a three-phase bridge configuration, the present invention can be applied to a single-phase inverter using four switching elements, and the same effect can be obtained.

Although the present invention can be applied to a bipolar transistor, an IG which is a switching element having an insulated gate input is used.
The effect of downsizing is greater when implemented with BT or MOS-FET.

[0033]

As is apparent from the above embodiment, according to the present invention, by controlling the duty of the ON / OFF state of the switching element of the lower arm until the first waveform output immediately after the commercial power is turned on, The capacity of the power supply smoothing capacitor for the drive circuit can be reduced, and the capacitor of the charge pump circuit can be charged within a practical range without using an inrush current suppressing resistor.

As described above, since a rush current suppressing resistor is unnecessary and the capacity of the power supply smoothing capacitor for the drive circuit can be reduced, a small and inexpensive inverter device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an inverter device according to an embodiment of the present invention.

FIG. 2 is an operation waveform diagram when a capacitor is charged in the charge pump circuit of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional inverter device.

FIG. 4 is an operation waveform diagram when a capacitor is charged in a conventional charge pump circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC voltage source 2a-2f Switching element 3a-3f Drive circuit 6a-6c Capacitor 8 Power supply for drive circuit 9 Power supply smoothing capacitor for drive circuit 10 Control means (PWM signal generator)

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yasuyuki Yokouchi 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H007 AA17 CA01 CB05 CC23 CD06 DB03 EA02 GA03

Claims (2)

[Claims] 1. A plurality of pairs of switching means comprising a positive side switching element and a negative side switching element connected between a positive side and a negative side of a DC voltage generated from a commercial power supply, respectively, and said switching means. A driving circuit for driving the element, a capacitor for a charge pump circuit that is a power supply for a driving circuit for the switching element connected to the positive side of the DC voltage, a power supply for a driving circuit for charging the capacitor, and a power supply for the driving circuit ON and OFF of the negative side switching element when outputting the capacitor and the pseudo AC waveform immediately after the commercial power supply is turned on.
An inverter device comprising: control means for arbitrarily changing a duty and a cycle of a state to suppress and charge a capacitor of a charge pump circuit without using an inrush current suppressing resistor. 2. A switching device comprising: a MOS-FET;
2. The inverter device according to claim 1, wherein the inverter device is a power switching device having an insulated gate input such as a GBT.