JPH02214474A - Resonance type inverter circuit - Google Patents

Abstract

PURPOSE:To freely adjust an output by designing a circuit which can operates in any two states selected from three states, and switching the state. CONSTITUTION:A resonance type inverter circuit has a serial resonance circuit of a resonance capacitor 4 and a resonance inductor 5, and a switching element 2 to supply a sine wave AC current to a load 3. The element 2 for forming a free vibrating state is added, and a switch state (contact D) for disconnecting a DC power source 1a is provided. As a result, an output regulating function can be provided by making the circuit in one of exciting, free vibrating and regeneratively braking states.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a resonant inverter circuit that converts DC power into AC power, and particularly relates to a power source that rectifies the output AC power to obtain a stabilized DC output. It exhibits its effects when applied to equipment.

Conventional technology In a normal square wave inverter circuit, it is necessary to forcibly turn off the switching elements while a relatively large current of the rated current level is flowing through them. When operating at a high frequency, the problem of increased heat generation and switching noise due to switching loss of switching elements becomes serious, and the energy conversion efficiency of the inverter is low, and it is necessary to satisfy various standards regarding electromagnetic interference and reduce the generated noise. The disadvantages include that the price of the filter used to suppress the level increases, and that the ground leakage current increases through the filter element.

Therefore, various resonant inverter circuits have been proposed to eliminate the drawbacks of the above-mentioned square wave inverter circuits.

A basic circuit diagram of a conventional resonant type inverter circuit is shown in Fig. 4. Fig. 4(a) is called a current resonant type, where the capacitance of the resonant capacitor 4 is C(F) and the inductance of the resonant inductor 5 is L. (H), and drive the switching element 2 at a frequency that almost matches the resonant frequency f of the series resonant circuit consisting of these, = 1/(2ππ lower > (Hz), and repeat switching every half cycle of the circuit connection. This allows an alternating current close to a sine wave to flow through the load 3.

In addition, in Fig. 4 (bl is called a voltage resonance type, the capacitance of the resonant capacitor 4 is C (F), the inductance of the resonant inductor 5 is L (H), and the resonant frequency fo of the parallel resonant circuit consisting of this is = By driving the switching element 2 at a frequency approximately equal to 1/(2πf σ) (Hz) and repeating switching every half cycle of the circuit connection, it is possible to apply an alternating current close to a sine wave to the load 3. can.

la and 1b are direct VL power supplies. P indicates the switch position for the + side half wave, and M indicates the switch position for the ~ side half wave.

Problems to be Solved by the Invention The conventional resonant inverter circuit described above does not have an output adjustment function, and the operating point depends on the voltage or current value of the DC power supply, the resonant capacitor, the resonant inductor, the load, and the impedance of the DC power supply. The disadvantage was that the decision was made. To eliminate this drawback, 1. Operate the switching element intermittently.

■ Adding an auxiliary resonant circuit to the resonant circuit allows the impedance of the entire resonant circuit to change significantly in response to minute changes in the operating frequency.

However, in (2), there are disadvantages such as large fluctuations in AC output power and the need for a margin in the electrical performance of the switching element, while in (2), fluctuations in the operating frequency are essential. Another disadvantage is that an extra auxiliary resonant circuit needs to be added.

Means for Solving the Problems An object of the present invention is to provide a resonant inverter circuit that has small fluctuations in AC output power and operating frequency, takes advantage of the inherent characteristics of a resonant inverter circuit, and has an output adjustment function. It is.

In the resonant inverter circuit of the present invention, its operating state is defined as an excitation MJ in which the resonant circuit receives energy from the DC power source and increases electrical vibration, and a resonant circuit that does not transfer energy to or from the DC power source. "F free vibration state" in which free vibration is approximately determined by the impedance of the resonant circuit and the load, and "regenerative braking state" in which the resonant circuit gives the energy of the electrical vibration to the DC power supply and the electrical vibration is damped.
As a configuration in which two or more types can be selected from among the three types, the AC power of the resonant circuit or the load electromagnetically coupled to it can be changed by switching the state using the half period of vibration of the resonant circuit as the minimum time unit. It is a resonant inverter circuit with a so-called output adjustment function.

Operation The basic circuit of the resonant inverter circuit of the present invention is shown in FIG.

FIG. 1(a) is a basic circuit diagram of a current resonant inverter circuit, and the difference from the conventional current resonant inverter circuit shown in FIG. 4(a) is that the switching element 2' is used to create a free vibration state. is added, and there is a switch-like M (contact symbol D) that disconnects the DC power supply 1a. When the switch contact is selected, the energy supply from the DC power source 1 is stopped, and a free vibration state is created in which the energy of the series resonant circuit consisting of the resonant capacitor 4 and the resonant inductor 5 is consumed by the load 3. Further, in order to increase the vibration of the series resonant circuit, the state in which switch contacts P and M are alternately selected every half cycle is the same as the operation of the conventional current resonant inverter shown in FIG. 4(a), and the present invention This is what we call the excitation state.

Furthermore, a state can be set in which the switch contacts P and M are alternately selected every half cycle in a direction to cancel the vibration of the series resonant circuit, and this state is a regenerative braking state in which the vibration energy of the series resonant circuit is returned to the DC power supply 1a. It is.

Fig. 1(b) is a basic circuit diagram of a voltage resonant inverter circuit, and the difference from the conventional voltage resonant inverter circuit shown in Fig. 2(b) is that a new contact is provided in the switching element 2. There is a particular thing. When the contact is selected, the DC power supply 1b is short-circuited, and the parallel resonant circuit consisting of the resonant capacitor 4, resonant inductor 5, and load 3 is disconnected.
It becomes a free vibration state in which the vibration energy is consumed by the load. Furthermore, in order to increase the vibration of the parallel resonant circuit,
The state in which switch contacts P and M are alternately selected every half cycle is the same as the operation of the conventional voltage resonant inverter shown in FIG. 4, and is called an excitation state in the present invention. Further, a state can be set in which switch contacts P and M are alternately selected every half cycle in a direction to cancel the vibration of the parallel resonant circuit, and this state is a regenerative braking that returns the vibration energy of the parallel resonant circuit to the DC power supply 1b. state.

EXAMPLE Hereinafter, an example of the present invention will be explained with reference to FIGS. 2 and 3.

First, the circuit diagram shown in FIG. 2 is an embodiment of the present invention constructed with an inverter circuit generally called a half bridge. In the above-mentioned excitation state, the switching elements 2p and 2m are alternately activated every half cycle to match the vibration period determined by the impedance of the resonant circuit consisting of the resonant capacitor 4, the resonant inductor 5, and the load 3 coupled by the isolation transformer 8. The switching element 2' is repeatedly turned on and off.
is kept in an off state to obtain alternating current vibration energy from the direct current power supply 1. Further, in the above-mentioned free vibration state, the switching elements 2p and 2m are kept off, the switching element 2' is kept on, and the electrical vibration energy of the resonant capacitor 4 and the resonant inductor 5 is consumed by the load 3. Furthermore, in the regenerative braking state described above, the switching element 2 p
12m and 2' are all kept off, and the energy of the resonant circuit is rectified by diodes 6a and 6b and returned to the DC power supply 1 through bypass capacitors 7a and 7b.

Next, the circuit diagram shown in FIG. 3 is a current resonance type inverter circuit generally called a full bridge, and although there is almost no difference between the conventional current resonance type inverter circuit and the current resonance type inverter circuit of the present invention on the circuit diagram, The control method is different and constitutes the scope of the claims of the present invention.

That is, the conventional current resonance type inverter circuit is operated in a state called an excitation state in the present invention. The switching element 2 is adjusted to match the vibration period determined by the impedance of the resonant circuit consisting of the resonant capacitor 4, the resonant inductor 5, and the load 3 coupled via the isolation transformer 8.
The set of switching elements a and 2d and the set of switching elements 2b and 2c are alternately turned on and off every half cycle. In this state, energy from the DC power source 1 is always given to the resonant circuit, so when the energy consumption of the entire resonant circuit including the load 3 is low, an excessive resonant current flows, causing the switching element, resonant capacitor, and resonant There was a risk of damaging the inductor.

On the other hand, in the free vibration state of the present invention, the switching elements 2a s 2 b 12c - 2d are turned on one by one for half the vibration period of the resonant circuit, and for example, when the switching element 2a is on, diode 6c
is conductive, (switching element) 2a- (insulation transformer) 8- (resonant inductor) 5- (resonant capacitor) 4-
Current is passed through the circuit of (diode) 6c, and in the next half cycle, switching element 2b is turned on, (switching element) 2b - (insulation transformer) 8 - (resonant inductor)
Current passes through the circuit of 5-(resonant capacitor) 4-(diode) 6d. In this state, no energy is exchanged between the DC power supply 1 and the resonant circuit. Furthermore, in the regenerative braking state, switching elements 2a, 2b, 2°C0, 2d
is kept off, and the energy of the resonant circuit is rectified through the set of diodes 6a and 6d and the set of diodes 6b and 60, and is returned to the DC power supply 1.

For output control, the usual method is to monitor the current or voltage value of the resonant circuit, rectify the AC value, and feed it back to the control system. In the case of a DC power supply, it is of course possible to feed back the smoothed DC voltage value and DC current value.

Further, the resonant inverter circuit of the present invention has three states B (or two of these states): an excitation state, a free vibration state, and a regenerative braking state.
Since condition B) is taken, it is appropriate to determine the transition between each state by a digital arithmetic circuit, and it is possible to apply program control by a microprocessor as appropriate.

Effects of the Invention In conventional resonant inverter circuits, the flow of energy from the DC power source was always in the direction of outflow, so there was no output adjustment function.However, the resonant inverter circuit of the present invention solves the above-mentioned conventional problem. By solving this problem and creating a state in which the flow of energy from the DC power supply is stopped or a state in which energy flows back from the resonant circuit to the DC power supply, there is a remarkable effect that the output can be freely adjusted.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are basic circuit examples of a resonant inverter circuit according to the present invention, and FIGS. 2 and 3 are circuit diagrams of main parts of different embodiments of the resonant inverter circuit of the present invention. ,
Figures 4(a) and bl are basic circuit examples of conventional resonant inverter circuits. 1.1a, 1b = DC power supply 2.2', 2p, 2m, 2a, 2b, 2c, 2d switching elements 3 : Load 4: Resonant capacitor 5: Resonant inductor

Claims (1)

[Claims] It has a resonant circuit consisting of a capacitor and an inductor,
Two or more operating states are selected from three types: an excitation state in which the resonant circuit receives energy from the DC power supply, a free vibration state in which it does not exchange energy with the DC power supply, and a regenerative braking state in which it provides energy to the DC power supply. A resonant inverter circuit characterized in that it has means for switching using a half period of vibration of the resonant circuit as the minimum time unit, and by this switching, the AC power of the resonant circuit or a load electromagnetically coupled thereto is controlled. .