JPH01115099A - Inverter - Google Patents

Abstract

PURPOSE:To make it possible to conduct output control of a load with the increase of a switching loss reduced by intermittently operating a switching element, and repeating a continuous and intermittent operation for a longer period. CONSTITUTION:An intermittent operation is made in which e.g. when a signal is generated as (D) with a dividing circuit 95 by a signal from a first oscillation circuit 91 of a control circuit 9, a current flows in a load as a full line of (E) for one period and an operation stops in the next one period. Then, a signal of a long period T e.g. as (F) is genetated by a second oscillation circuit 97, the circuit 95 is operated in a H level, a dividing signal as (D) is not generated by the circuit 95 in the period of a L level, and a switching element of an inverter is continuously operated as (A) and (B). A load current is continuously supplied to a load for a t2 period of (F), an intermittent operation, in which the inverter stops its operation by the operation of the circuit 95, the output supplied to a load can be controlled. This makes it possible to restrain the increase of a switching loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter capable of controlling high frequency power supplied to a load.

[Conventional technology]

There is a device that uses an inverter to supply high-frequency power to a load such as a discharge lamp, and a method for controlling the high-frequency power supplied to this load (dimming is used when the load is a discharge lamp) is 61-271792 or 1985 Illuminating Engineering Society of Japan National Conference Lecture Proceedings 35P, there are known inverters that change the frequency of the output voltage of the inverter. The load output control (dimming) operation by changing this frequency will be explained based on the collection of lectures of the Illuminating Engineering Society. FIG. 7 shows this conventional device, and in FIG. 1, a high frequency current is supplied to the discharge lamp (5) via a coil (4). Therefore, if the operating frequency of the switching elements (2a) and (2b) of the inverter is increased, the frequency of the output voltage of the output transformer (3) will increase, and the impedance of the coil (4) will increase. The current of ; decreases.In this way, the output can be controlled, and in the above example, the load is a metal halide lamp.

Discharge lamps such as fluorescent lamps can also be dimmed using the same principle.

[Problem that the invention seeks to solve]

In this way, conventional devices control the output of the load.

Since this is done by changing the output voltage frequency of the inverter, it is necessary to change the output frequency of the inverter over a wide range for output control.

For this reason, it is advisable to use a highly efficient inverter equipped with a resonant circuit (resonant type inverter) as an inverter, and even if one is used, the switching loss of the switching elements will increase due to an increase in frequency. There was a problem.

The present invention has been made to solve the above-mentioned problems, and is an inverter that maintains resonant operation, that is, reduces the increase in switching loss of the switching elements of the inverter. The object of the present invention is to obtain a device that can control the output of a load.

[Means for solving problems]

The inverter according to the present invention operates at a cycle that is sufficiently long compared to the output frequency of the inverter.

The output of the load is controlled by repeating continuous operation and one intermittent operation.

[For production]

In the inverter of the present invention, a control circuit (91) that controls the operation of the switching element causes the switching element to operate intermittently, and repeats continuous operation and intermittent operation at a longer cycle.

〔Example〕

FIG. 1 shows an embodiment of the device according to the invention.

FIG. 6 shows its operating waveform. In FIG. 1, 11) is a DC power supply, and (2a) and (2b) are switching elements of an inverter, which are composed of transistors here. (51 is the load (here, a discharge lamp such as a fluorescent lamp)
, +S+ is a coil that forms a resonant circuit together with a capacitor (7), (8) is a capacitor, (91 is a control circuit, and FIG. 5 is a circuit diagram of an example embodying this control circuit (9). In Figure 5, (91) is the first oscillation circuit t that generates clock pulses, (92) is a flip-flop, (91) is an AND circuit, and (9 is a circuit for driving the switching elements of the inverter). A drive circuit, (95) is a frequency dividing circuit that generates a frequency-divided signal for intermittent operation of the inverter, and (97) is a second oscillation circuit that generates a signal with a sufficiently long period compared to the output frequency of the inverter. The duty ratio of the output signal can be variably set using a variable resistor (9 days).

In the device configured as described above, the first oscillation circuit (9
For example, the frequency divider circuit (95)
When a signal is generated as shown in Figure (D), the load performs an intermittent operation in which a current flows for one cycle as shown by the solid line in (E) and the operation is stopped for the first cycle. Here, the second oscillation circuit (9
7), for example, as shown in FIG. The switching elements of the inverter operate continuously as shown in Fig. 6(a) and (b) without generating a frequency-divided signal as shown in Fig. 6(d).Then, the load is ), the load current is continuously supplied during the period t2, and during the period e tI, the frequency dividing circuit (95)
This operation results in intermittent operation that causes the inverter to stop operating, and the output supplied to the load can be controlled. Here, 'Duty of the output signal of the second oscillation circuit (97)
Appropriate power can be supplied to the load by setting the ratio to a desired value using a variable resistor (98). In this manner, the inverter can operate the resonant circuit at an appropriate frequency and control the output, and furthermore, when the load is a discharge lamp, there is a period t1 during which it operates continuously.

Discharge lamps also tend to maintain stable discharge. Figures 2 and 3.

FIG. 4 shows another different embodiment, and only points different from FIG. 1 are shown. In FIG. 2, numeral 31 denotes an output transformer, which here consists of a single cage transformer, but a coil may be connected in series with the load.

(7) is the capacitor of the resonant circuit, and αG is the coil.

It is called a voltage resonant inverter. In FIG. 3, coil Q3. Capacitor aυ constitutes a resonant circuit, and α1 is a diode. In this configuration, the number of switching elements is one, and the control circuit (91) may be simplified from FIG. It is possible to operate even if omitted. In FIGS. 3 and 4, the conduction period ratio of the switching element is set to 50 to 6096 for one period.
If you set it to about.

Good symmetry of load current. In FIG. 4, a capacitor Qll of a resonant circuit is connected in parallel with a switching element (2a).

The inverter can be modified other than the embodiment.

The load may also be other than a discharge lamp. If the load is a discharge lamp, 1
In addition to lighting, two or more lights may be connected in series, or multiple lights may be lit in parallel by connecting impedances such as coils in series. It goes without saying that the switching elements of the inverter can be other than ordinary bipolar transistors.

The configuration of the control circuit (9) is also not limited to the embodiment, and may have other configurations. In addition, in the embodiment, the 9 frequency divider circuit (95) has been shown to be a signal that operates on an inter-day cycle, but
Other cycles may be used. Furthermore, the signal generated by the second oscillation circuit (97) of the control circuit (91) is as follows.

It may be made at a remote location and transmitted to operate the frequency dividing circuit (95). In addition, if the period T is set to correspond to 100/120 Hz and a DC power source 11) obtained by full-wave rectification of a commercial AC power source 5D/50)Iz is used as the DC power source 11), problems such as flickering can be avoided even if the ripple of the DC power source is quite large. I have nothing to give.

The DC power source 11) can be used other than one that rectifies and smoothes a commercial AC power source; in this case, the period of the second oscillation circuit (97) that is shorter than the period equivalent to 100/120 Hz is suitable for the DC power source. It is preferable if there is ripple, and especially if the load is a discharge lamp.

Furthermore, if the load is a discharge lamp, in order to reduce the deterioration of the electrodes at the time of starting the discharge lamp, set the tl period ratio as large as possible when starting the discharge lamp, and preheat the electrodes with a comb before starting the discharge. Alternatively, during dimming, in order to ensure and stabilize the discharge of the discharge lamp after the start of discharge, the period ratio of t2 may be set as large as possible for a predetermined period. A timer may be provided in the control circuit (9) and the above-described operation may be performed for a predetermined period when the discharge lamp is started.

In addition, in the explanation of the embodiment, the frequency divider circuit (95) was used to perform intermittent operation, so during this operation, there is a period when current is flowing through the load, t3 in FIG. 6 (e), and a rest period. t
4 is approximately t3>t4. but.

If t5<t4, the controllable range can be widened. In this case, the control circuit is 1, for example (
95) is used as a counter, and this counter operates a time limit circuit such as a monostable multivibrator that generates a period of t4, and during this time limit operation, the operation of the switching element of the inverter is stopped, and the first oscillation is stopped. By stopping the oscillation of the circuit, t4 can be set to a desired time.

When the load is a discharge lamp, the electrode preheating means is a capacitor (7
) may be used.

〔Effect of the invention〕

As described above, according to the device of the present invention, since the output is controlled by repeating continuous operation and intermittent operation of the inverter, increase in switching loss of the switching elements of the inverter can be suppressed even when controlling the output. In addition, when the load is a discharge lamp, there is an effect that stress on the switching element is reduced compared to a lamp that repeats turning on and off in a long cycle.

[Brief explanation of the drawing]

1 to 4 are circuit diagrams showing embodiments of the device according to the present invention, FIG. 5 is a circuit diagram showing an example of a control circuit that can be used in the device of the present invention, FIG. 6 is an operation explanatory diagram, and FIG. Figure 1 shows a circuit diagram of a conventional device. In the figure, 11) is a DC power supply, (2a), (2b
) is a switching element, (5) is a load, and (9) is a control circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (6)

[Claims] (1) In an inverter that is connected to a DC power source, opens and closes a switching element to generate a high-frequency voltage, and is equipped with a resonant circuit to supply a substantially sinusoidal load current to the load, the operation of the switching element is controlled. During intermittent operation, the switching element is opened and closed at approximately the resonance period of the resonant circuit, and during intermittent operation, the switching element is stopped for a period of at least approximately one cycle of the high frequency voltage. An inverter characterized by comprising a control circuit that repeatedly performs continuous operation without an operation stop period at a predetermined period. (2) The switching element sets its operation stop period with a signal formed from the output signal of the first oscillation circuit, and the period and time of intermittent operation and continuous operation according to the output signal of the second oscillation circuit. 2. The inverter according to claim 1, wherein the inverter is driven to open and close by a control circuit that sets a ratio. (3) During intermittent operation, the control circuit defines the time t_3 during which the load current is flowing and the time t_4 during which the load current is at rest as approximately t_3.
The inverter according to claim 1 or 2, characterized in that ≒t_4. (4) The control circuit determines that during intermittent operation, the time t_3 during which the load current is flowing and the time t_4 during which the load current is at rest are t_3<t
_4. The inverter according to claim 1 or 2, characterized in that: _4. (5) The load is a discharge lamp, and at the time of starting, the time ratio of intermittent operation to continuous operation is maximized, and a predetermined time is provided for preheating the electrodes of the discharge lamp load during this period. An inverter according to any one of claims 1 to 4. (6) The control circuit provides a period for minimizing the time ratio of intermittent operation to continuous operation after the time-limited operation for preheating the electrodes at the time of starting the load. Inverter described in section.