JPH01321863A - Inverter - Google Patents

Abstract

PURPOSE:To reduce switching loss by changing the rate of intermittent operation stopping period of time with respect to the operating period of time of an inverter. CONSTITUTION:An inverter device is constituted of a DC power source 1 and switching elements 2a, 2b which are connected to the power source 1. The inverter device is also provided with the electric discharge lamp 5 of a load, a coil 9, forming a resonance circuit together with capacitors 10, 11, diodes 12a, 12b and a control circuit 13. The resonance frequency of the resonance circuit is changed in accordance with the rate of intermittent operation stopping period of time with respect to the opelating period of time in the electric discharge lamp 5 while the control circuit 13 supplies a control signal, whose frequency is changed in accordance with the rate of said intermittent stopping period of time with respect to the operating period of time, to said switching elements 2a, 2b. According to this method, the output control of the electric dischange lamp 5 may be effected while the switching elements 2a, 2b may be opened and/or closed under the condition of resonance at all times regardless of the output control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter having a resonant circuit coupled to a load.

[Conventional technology]

Conventionally, there has been an inverter that supplies 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 in the case of a load or discharge lamp) was developed in the Japanese Patent Laid-Open Publication No. It is known to change the frequency of the output voltage of an invanitor, as disclosed in No. 61-271792 or in the 1985 Illuminating Engineering Society of Japan National Conference Lecture Proceedings, page 35.

FIG. 8 shows this conventional inverter. In the figure, a high frequency current is supplied to a metal halide lamp 5 via a coil 4. Therefore, unless 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, the impedance of the coil 4 will increase, and the current of the discharge lamp 5 will decrease. In this way, the output can be controlled. In this conventional example, the load is a metal halide lamp, or
Discharge lamps such as fluorescent lamps can also be dimmed using the same principle.

[Invention or problem to be solved]

As described above, since conventional inverters control the output of the load by changing the output frequency, it is necessary to vary the output frequency of the inverter over a wide range for output control. For this reason, it is difficult to use a highly efficient inverter equipped with a resonant circuit (resonant type inverter) as an inverter, and even if it is used, there are problems such as increased switching loss of switching elements due to the increase in frequency. was there.

The present invention has been made to solve the above-mentioned problems, and controls the output of the load while maintaining resonant operation, that is, by reducing the increase in switching loss of the switching elements of the inverter. The purpose is to obtain an inverter that can

[Means to solve the problem]

In the present invention, in order to achieve the above object, an inverter is provided with the following elements a, b, and c.

a. A resonant circuit whose resonant frequency changes when a load device is coupled, depending on the ratio of the intermittent operation stop period to the operation period in the load device.

b. A switching element connected to a DC power supply and exciting the common I/O circuit.

C9 A control circuit that supplies a control signal that may include an intermittent stop period and whose frequency changes in accordance with the ratio of the intermittent stop period to the operating period to the surface switching element.

(Function) According to the above configuration, it is possible to control the output of the load by changing the ratio of the intermittent operation stop period to the operation period, and the switching element is always opened in a substantially synchronized state regardless of the output control. , can be closed.

(Example) The present invention will be explained below with reference to Examples.

FIG. 1 is a circuit diagram of an "inverter" according to a first embodiment of the present invention. In the figure, 1 is a DC power supply, and 2a and 2b are switching elements connected to this DC power supply 1, which are constructed of transistors here. 5 is a load such as a discharge lamp such as a fluorescent lamp; 9 is a coil forming a resonant circuit together with a capacitor 10 and 11; 12a and 12b are diodes; 13 is a control circuit; FIG.
The specific configuration is shown below.

In FIG. 2, reference numeral 21 indicates an activation circuit for generating clock pulses, 22 indicates a flip-flop, and 23a.

23b is an AND circuit, 24a and 24b are drive circuits for driving the switching elements 2a and 2b, 25 is a counter, and 26 is a time limit circuit, which is constructed of a monostable multivibrator here.

27 is a capacitor, and the output pulse time of the time limit circuit 26 can be set by a variable resistor 28. This time limit circuit 26 operates the oscillation circuit 21 when its output is at H (high) level, but stops the operation of the oscillation circuit 21 when its output is at extremely low level, that is, opens and closes the switching elements 2a and 2b. stop.

Reference numeral 29 denotes a changeover switch, one contact 29X of which switches the switching element between normal continuous operation and intermittent operation, and the other contact 29Y switches the period of the clock pulse of the oscillation circuit 21.

Next, the operation of this embodiment will be explained using the waveform diagram in FIG. FIG. 3 shows the output waveforms of each part of the control circuit 13 of FIG. 2 and the load current waveform flowing through the discharge lamp 5.

In this embodiment, the switching element 2a.

There is an intermittent stop period in which the switching elements 2b stop opening and closing (stopping the inverter), and the opening and closing cycles of the switching elements 2a and 2b are different depending on whether they are in absentee composing or in continuous operation. Then, the changeover switch 29 is in the state as shown in FIG.
In other words, contact 29X.

When 29Y is in an open state, continuous operation is being performed, and a load current as shown in FIG. 3 (e) flows. Next, when dimming, etc., connect the selector switch 29 to contacts 29X and 29Y.
When closed, the frequency of the clock pulse generated by the oscillation circuit 21 becomes high because the resistor 21a or the contact 29X is short-circuited.

At this time, for example, if the counter 25 operates on the fifth clock pulse, the output of the counter 25 is as shown in FIG.
The waveform becomes as shown in (b), and the time limit circuit 26 is tripped at the rising edge of the pulse, and the time limit circuit 26 stops operating for a time t2 as shown in FIG. 3 (c), and the output becomes L level. Therefore, the excavation circuit 21 stops operating, and the inverter stops operating. A load current as shown in FIG. 3(d) flows through the discharge lamp 5. At this time, the load is the discharge lamp 5 such as a fluorescent lamp, so the discharge state of the discharge lamp 5 is different between the full light state where the inverter is operated continuously and the dimmed state where the inverter is operated intermittently, and the dimmed state When viewed from the external circuit, this corresponds to a state where the impedance becomes large.

In other words, this corresponds to the fact that the impedance of the load connected in parallel with the capacitor 10 of the series resonant circuit consisting of the capacitor 10.11 and the coil 9.61 is larger during dimming than during full light, and this circuit The resonant frequency of is higher during dimming than at full light. By the way, in this embodiment, the open and close wave numbers of the switching element are changed between the dimming state and the full light state, so that the switching element can be opened and closed in a substantially resonant state in any case. The circuit constants are determined.

Therefore, by opening and closing the changeover switch 29, the discharge lamp 5 can be switched between full light and dimming, and in both cases, the switching element is opened and closed in a substantially resonant state, so that the loss of the switching element increases. There's nothing to do.

In the above explanation, the time limit circuit 26 is operated by the output of the counter 25 so that the operation stop time t2 can be arbitrarily set. The output of this frequency dividing circuit may be used in the same way as the output of the time limit circuit 26. In this case, the inverter is operated for two cycles, and the time equivalent to two cycles (t
2) It is also possible to stop the operation of the inverter.

Also, set the frequency dividing operation of the frequency dividing circuit appropriately (dividing ratio 1/4, 1
/8 etc.), it is also possible to change the stop time t2.

FIG. 4 is a circuit configuration diagram showing a second embodiment of the present invention.

In the figure, 3 is an output transformer (leakage transformer), and a discharge lamp 5 as a load is connected to the secondary side of the output transformer 3. 14 is a coil.

In this circuit, a resonant circuit is formed by the inductance of the output transformer 3 and the capacitor 17, and even in such a case, as in the first embodiment, the resonant circuit is fully illuminated.

During dimming, the switching element is opened and closed in a substantially resonant state.

FIG. 5 and FIG. 6 show a third embodiment and a fourth embodiment of the present invention. In these embodiments, one switching element 2 is used, and 10.15.9.16 in the figure is used.
are a capacitor and a coil, respectively, which constitute a resonant circuit.

In these embodiments, since only one switching element 2 is used, the configuration of the control circuit 13 can be made simpler than the circuit shown in FIG. 2 (for example, only one driving circuit 24 is required). Further, the ON period and the OFF period of the switching element 2 may be set to substantially equal lengths of time, and the switching element 2 may be operated continuously, and the frequency may be increased during intermittent operation in the same manner as in the first embodiment. At this time, in the circuit configuration of FIG.
Since the operating mode determined by the resonant circuit appears in the FF state, it is possible to operate by changing the ON period and OFF period of the switching element 2 (by making the ON period longer).
The oscillation circuit 21 of the control circuit 13 does not generate a clock pulse with a duty cycle of ON, 0FF, or 50%, but uses an excavation circuit that can generate an output with a duty cycle longer than 50% on the other side, to avoid stiffness in the switching element 2. By allocating it to the ON period of , it is possible to operate more appropriately both during continuous operation and during intermittent operation.

As explained above, the principle of the present invention is that a resonant circuit and a load device are electrically or electromagnetically coupled, and the electrical characteristics of the load device are determined according to the ratio of the intermittent operation stop period to the operation period of the load device. This is based on the fact that (in a discharge lamp, the discharge state or impedance) changes, and the resonant frequency of the circuit changes.

In this embodiment of the present invention, the duty cycle, which is the period during which the switching element 2 conducts current, is 50% or close to 60% as the generator circuit 21 of the control circuit 13.
%) It is sufficient to use one with a rectangular wave output, and the flip-flop 22 can be omitted, and the control circuit 1
3 may of course be other than the example shown in FIG.

Although each embodiment has been described above, the inverter of the present invention can be modified other than the above embodiments, and the load may also be other than a discharge lamp. The DC power source 1 may also be used other than one that rectifies and smoothes a commercial AC power source, and may have a plurality of loads (coils connected in series or parallel, etc.). The switching elements of the inverter may be other than ordinary transistors, and the time during which current is passed through the load may be set to 4 and a half cycles as t in the explanation of FIG. 3, or may be set to other values.

Further, the configuration of the changeover switch 29 or the method of switching between continuous operation and intermittent operation is not limited to the above embodiment.

Further, in the embodiment, the operation stop period t2 is set by the variable resistor 28 of the time limit circuit 26, but a signal may be supplied from the outside to the control circuit 13 to control the operation of the oscillation circuit 21, for example. Since signals with periods of 1+ and 12 are generated externally, the counter 25. The time limit circuit 26 and the like are not required inside.

In addition, when the load is a discharge lamp, in order to reduce electrode deterioration at the time of starting, the operation stop period t2 is lengthened at the time of starting.
A cold start of the discharge lamp may be prevented and the electrodes may be preheated during this period. The invention related to this preheating period was proposed by the present applicant in Japanese Patent Application No. 1983-277856.

This electrode preheating means may be other than using the capacitor 10.

Furthermore, in the description of the embodiments, the combination of continuous operation and intermittent operation has been described, but it goes without saying that the configuration may be a combination of an intermittent operation state with a short operation stop period and an intermittent operation state with a long operation stop period. .

Furthermore, if the control circuit 13 has a configuration as shown in FIG.
If contact 29Y of the changeover switch is closed, time limit circuit 2
The operation stop time t set in No. 6 is too short. On the contrary, contact 139
When Y is opened, t becomes longer, and at this time, the contact 29X is closed, so the output frequency of the oscillation circuit 131 becomes higher, and the output frequency of the inverter becomes higher.

The present invention is particularly suitable for a load such as a discharge lamp whose internal state (physical state of the discharge body) changes due to intermittent operation stop periods, or may be applied to other loads.

In other words, it is applicable if the load is electrically or electromagnetically coupled to a resonant circuit excited by a switching element, and the change in the ratio of the intermittent operation stop period to the operation period affects the resonant frequency. In that case, it goes without saying that the present invention can be applied not only to a circuit where the resonant frequency increases as in each of the embodiments described above when the ratio of the operation stop period increases, but also to a circuit whose weight is less than 1 g.

Alternatively, the fli'IJ control circuit may be used as a control circuit by detecting the resonance state of the resonance circuit.

〔Effect of the invention〕

As described above, in the present invention, in an inverter equipped with a resonant circuit, it is possible to perform load output control while maintaining resonant operation, and it is possible to suppress an increase in switching loss of switching elements.

[Brief explanation of the drawing]

1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the control circuit of FIG. 1, and FIG. 3 is a circuit diagram showing an example of the control circuit of FIG.
FIG. 4 is a circuit diagram showing the second embodiment of the present invention, FIG. 5 is a circuit diagram showing the third embodiment of the present invention, and FIG. FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention, FIG. 7 is a circuit diagram showing a different example of the control circuit, and FIG. 8 is a circuit diagram showing a conventional example. In the figure, 1 is a DC power supply, 2a and 2b are switching elements,
9 is a coil, 10.11 is a capacitor, and 13 is a μJ control circuit. Note that the same or similar symbols indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An inverter characterized by comprising the following elements a, b, and c. a. A resonant circuit in which, when a load device is coupled, the resonant frequency changes depending on the ratio of the intermittent operation stop period to the operation period of the load device. b. A switching element connected to a DC power source and exciting the resonant circuit. c. A control circuit that supplies the switching element with a control signal that may include an intermittent stop period and whose frequency changes in accordance with the ratio of the intermittent stop period to the operating period.