JPH0686569A - Inverter circuit - Google Patents

Abstract

PURPOSE:To reduce losses in an inverter circuit. CONSTITUTION:Low on-loss IGBTs Q1-Q3 are employed in the upper arm, and low switching loss IGBTs Q4-Q6 are employed in the lower arm. With this configuration, the loss can be reduced by decreasing the on-voltage in the upper arm, and by shortening the switching time in the lower arm. Since the life time of IGBTs can be controlled in their manufacturing process, a single type of IGBTs can be sorted into low on-loss IGBTs and low switching loss IGBTs. Since it is sufficient to use only a single type of IGBTs, cost reduction and other advantages can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter circuit mainly used for controlling a DC brushless motor or the like.

[0002]

2. Description of the Related Art Conventional, for example, pulse width modulation (hereinafter referred to as P
It is called WM. In an inverter circuit that performs), a switching element with the same characteristics is generally used on the commutation side for switching with a long period signal such as a fundamental frequency signal of AC power and on the PWM side for switching with a short period signal such as a pulse width modulation carrier signal. Was used.

By the way, since the long-period signal input to the commutation side has a relatively small number of times of switching, it is desirable to reduce the steady loss at the time of switching on rather than the loss at the time of switching transient.
It is known that it is desirable to reduce the loss due to switching transient in the short-period signal input to the M side.

Therefore, an inverter circuit for reducing loss is disclosed in Japanese Patent Laid-Open No. 63-262062.
This inverter circuit uses bipolar type transistors which are low speed switching elements for commutation side and FE which is high speed switching elements for PWM side.
It uses T. In this way, the switching element is selectively used for the transistor and the FET to reduce the power loss.

Further, in Japanese Patent Laid-Open No. 63-43576, a low on-loss transistor element such as a bipolar transistor is used for commutation, and a high speed switching element such as a MOS-FET or bimos transistor is used for the PWM side. In the same manner as the above-mentioned inverter circuit, a circuit aiming to reduce power loss is disclosed.

[0006]

However, it is not always appropriate to use different types of elements on the commutation side and the PWM side in terms of cost reduction and the like. Therefore, an object of the present invention is to provide an inverter circuit capable of reducing power loss even if the upper and lower arms are formed of one type of element.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a plurality of upper and lower arms formed by connecting switching elements in series are connected in parallel to a DC power source, and a series connection point of the switching elements is provided. In an inverter circuit that outputs AC power according to the conduction period of the switching device, a low on-loss IGBT (insulated gate) that switches the switching devices forming the upper and lower arms with a long-period signal such as a fundamental frequency signal of the AC power. Bipolar mode transistor) and low switching loss IG that switches with short-period signals such as carrier signals for pulse width modulation
An inverter circuit comprising a BT.

[0008]

A low on-loss IGBT having a low on-voltage for switching a long period signal is used, and a low switching loss I having a high switching speed is used for switching a short period signal.
By using the GBT, it is possible to reduce the power loss of the upper and lower arms with one type of IGBT. Further, since both are composed of one type of IGBT, it is possible to reduce the cost.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Generally, the IGBT has a feature that the so-called lifetime control can be performed at the end of the manufacturing process to change the magnitude of the ON loss. That is, even one type of IGBT can be sorted into one with a large ON loss and one with a small ON loss. However, those with a small ON loss have a large switching loss, and those with a large ON loss have a small switching loss. Therefore, as shown in FIG. 2, a low on-loss IGBT on the commutation side and a low switching loss IG on the PWM side.
One type of IGB by allocating and using each BT
T can reduce the power loss on each side.

FIG. 1 is a circuit diagram of a main part of an inverter circuit according to the present invention. In this embodiment, a three-phase AC inverter circuit will be described, but it can be used for an inverter circuit having an arbitrary number of phases. The inverter circuit 1 uses low on-loss IGBTs Q1 to Q3 on the commutation side, and PWM
Low switching loss IGBTs Q4 to Q6 are used on the side. All of these IGBTs are the same kind of IGBT obtained by the lifetime control. And
Q1 and Q4, Q2 and Q5, Q3 and Q6 form upper and lower arms, respectively.

A DC power supply 2 is connected between the collectors of the IGBTs Q1 to Q3 and the emitters of the IGBTs Q4 to Q6, and the series connection points U, V, W of the respective IGBTs are connected.
Is supplied to the DC brushless motor 3, the inverter circuit 1 forms a three-phase bridge circuit. The diodes D1 to D6 connected between the collector and the emitter of each IGBT are free-wheeling diodes. Also, the DC brushless motor 3 is used as a load.
However, the load is not limited to the motor, and another load may be used.

Next, the long-period signal is applied to the gates g1 to g3 of the IGBTs Q1 to Q3, respectively, and the IGBT Q4.
The short period signals are input to the gates g4 to g6 of Q6 to Q6, respectively, and the DC voltage of the DC power supply 2 is converted into a three-phase AC voltage to rotate the motor 3.

Now, the relationship between the long-period signal and the short-period signal and the power loss will be described based on an embodiment. Figure 3
The long period signal shown in (A) is the IGBT on the commutation side.
When input to Q1 to Q3, the collector-emitter voltage Vce drops from the high level off voltage v1 to the low level on voltage v2. The fall time at this time is t1.
Then, the state of the on-voltage v2 continues for the time t2 and rises to the original high level voltage v1. The rising time at this time is t3
Is.

On the other hand, according to FIG. 1B, the collector-emitter current Ic becomes a rising on-current i1 almost at the same time as the collector-emitter voltage Vce falls.

Since this time t2 is much longer than t1 or t3, the on-voltage v2 at the time t2 is set to be shorter than the time t1 or t3 is shortened (that is, the fall or rise of the collector-emitter voltage Vce is made faster). The lower the value, the more the power loss (Vce) × (Ic) on the commutation side can be reduced. Therefore, a low on-voltage IGBT having a low on-voltage v2 may be used for Q1 to Q3.

According to FIG. 4A, the PWM-side IGBTQ
When a short period signal is input to 4 to Q6, the collector-emitter voltage Vce drops from the high level off voltage v3 to the low level on voltage v4 after time t4. Then, the state of the voltage v4 continues for the time t5 and, after the time t6, rises to the high level voltage v3 again. Furthermore, after the lapse of time t7, the voltage Vce changes similarly to the times t4 to t6. That is, the short cycle signal has a cycle (t4 + t5 + t6 + t7).
Is a pulsed signal of.

On the other hand, according to FIG. 2B, the collector-emitter current Ic rises from the current substantially zero to the current i2 after the time t4 to t6, and further falls to substantially zero after the time t7. Then, this change is repeated for a predetermined time.

The number of times of switching of this short period signal per unit time is much larger than that of the above long period signal. Therefore,
When the number of times of switching is large as described above, the on-voltage v4
The voltage Vc at times t4 and t6 from the power loss due to
The power loss due to the fall and rise of e is much larger. That is, in this case, even if the power loss due to the ON voltage v4 is sacrificed to some extent, the power loss on the PWM side becomes smaller when the power loss at the falling and rising of the voltage Vce is reduced. For this purpose, a low switching loss IGBT with a short fall time t4 and a short rise time t6 (fast switching speed) may be used.

[0019]

Since the IGBTs whose lifetimes can be controlled are used as the elements for the upper and lower arms, it is possible to distribute the IGBTs having the characteristics suitable for each arm. That is, by using a low ON loss IGBT with a low ON voltage for the upper arm and a low switching loss IGBT with a high switching speed for the lower arm, it is possible to reduce the power loss of the upper and lower arms with one type of IGBT. it can. Therefore, efficient switching characteristics can be obtained, and since the upper and lower arms can be configured by a kind of IGBT, the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part of an inverter circuit according to the present invention.

FIG. 2 is an on-loss vs. off-time characteristic diagram for explaining lifetime control.

FIG. 3 is a switching waveform diagram on the commutation side of the inverter circuit.

FIG. 4 is a PWM side switching waveform diagram of the inverter circuit.

[Explanation of symbols]

1 ... Inverter circuit, 2 ... DC power supply, 3 ... DC brushless motor, Q1-Q6 ... IGBT, D1-D6 ...
Circulating diode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumio Anraku 1-4-1 Chuo, Wako-shi, Saitama Stock Research Institute Honda Technical Research Institute

Claims (1)

[Claims] 1. A plurality of upper and lower arms formed by connecting switching elements in series are connected in parallel to a DC power supply, and AC power is output from a series connection point of the switching elements according to a conduction period of the switching elements. In an inverter circuit, a low on-loss IGBT for switching the switching elements forming the upper and lower arms with a long-period signal such as a fundamental frequency signal of the AC power and a low switching loss for switching with a short-period signal such as a pulse width modulation carrier signal. An inverter circuit characterized by comprising an IGBT.