JPH02285969A - Inverter - Google Patents

Abstract

PURPOSE:To obtain a highly safe inverter by providing an abnormality detecting means for controlling ON interval of a switching element in the direction for suppressing high frequency output and a power source circuit section for detecting current flowing through a resonance loop and providing a power source. CONSTITUTION:A current transformer CT2 for detecting current iL flowing through a resonance loop and producing a voltage and a power source circuit section C for rectifying/smoothing the voltage and producing a driving power source voltage Vcc2 are provided. Furthermore, an abnormality detecting means D for receiving the driving source voltage Vcc2 from the power source circuit section C and controlling ON interval of a switching element Tr1 in the direction for suppressing high frequency output, when a control means B is disabled, is provided. By such arrangement, application of excessive voltage onto the switching element, increase of switching loss, and the like, can be prevented even upon occurrence of abnormality in the control means.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to an inverter device that generates high frequency voltage.

(Prior Art) Conventionally, for example, a series circuit consisting of a resonant circuit consisting of an inductor and a capacitor connected to both ends of a DC power supply and a switching element such as a transistor, and a series circuit connected in parallel with either one of the series circuits. Consisting of a discharge lamp, −
Once the ON signal is applied to the switching element, the current flowing through the resonant circuit or the discharge lamp is converted into a voltage by a current transformer, etc., and fed back to the control end of the switching element, thereby causing self-oscillation operation. (hereinafter referred to as one-way self-excited inverter)
.

However, in such a one-way self-excited inverter, once the switching element is activated, the oscillation frequency is fixed by the resonance circuit and the discharge lamp, and cannot be set to an arbitrary oscillation frequency. There has been a problem in that high-frequency output adjustments such as dimming control, input voltage fluctuation compensation, overcurrent control, etc. cannot be easily performed.

Therefore, there is a strong demand for an inverter that basically performs self-excitation operation and can also control the output within predetermined conditions using signals from other sources (hereinafter referred to as one-sided self-excited and other-controlled inverters). It was done.

Regarding this, the applicant has already proposed (see Japanese Patent Application No. 159196/1982).

FIG. 7 shows an example of such a one-sided self-excited, other-controlled inverter, and its configuration includes a DC power source E and switching elements connected to both ends of the DC power source E via a resonant circuit. a transistor Tri, and a diode D connected in antiparallel with this transistor Tri.
1, a feedback control unit F that turns on and off the transistor Tri, and an inductor L2 at both ends to the resonant circuit.
The discharge lamp La, which is a load, is connected through a series circuit with the feedback controller F, and the transistor Tr2 is connected between the control terminal of the transistor Tri, and the ON state of the transistor Tr2 is controlled for a predetermined period of time. and a control means B that outputs a control signal.

Here, resonant circuit A consists of capacitor CI and inductor L
1 are connected in parallel, and a high frequency voltage is generated between these ends. The control feedback section F connects the discharge lamp La to the resonant circuit.
The primary winding N of the current transformer CT inserted between
1, a resistor R1 connected in series to the control end of the transistor Tri, and a secondary winding N2 of a current transformer CT connected between one end of this resistor R1 and the circuit ground. Tri performs self-excited vibration operation. The control means B is configured to output a control signal that remains on for a predetermined period of time to the control terminal of the transistor Tr2 that can control the on/off of the transistor Tri.

Next, the operating state will be explained below.

(Explanation of self-oscillation operation) Now, when the power switch SW (not shown) is turned on, a starting current flows from the DC power supply E through the starting circuit (not shown) to the control end of the transistor Tri. Tr
i is turned on. When this transistor Tri is turned on, the DC power source E is connected to the resonant circuit A and the discharge lamp La.
, an oscillating current flows through the transistor Tri via the primary winding N1 of the current transformer CT. When this oscillating current is detected from the primary winding Nl, a positive voltage is generated across the secondary winding N2, and a control current flows to the control end of the transistor Tri. Therefore, even if the starting current is interrupted, the control current can be continuously supplied. Next, when a negative voltage is generated across the secondary winding N2, the transistor Tri is reverse biased and turns off, causing the resonant circuit A and the inductor L
2. An oscillating current flows in the closed circuit of the discharge lamp La.

The self-oscillation operation is continued by the repetition of positive and negative voltages generated between the secondary windings 11i1N2.

(Explanation of self-excited other braking operation) On the other hand, a DC voltage is supplied from the DC power supply E, and the control means B
The driving power supply voltage VCCI is generated and the operation of the control means B starts. The on signal generated from the control means B can turn on the transistor Tr2. Then, when the transistor Tr2 is turned on, the transistor Trl that is on is forced to be turned off. Therefore, since the on-period of the transistor Tri can be arbitrarily shortened, the high-frequency output voltage of the transistor Tri can be controlled to decrease.

(In case of instantaneous power outage) Even if a momentary power outage occurs, self-excited vibration operation continues. However, the driving power supply voltage Vccl of the control means B
decreases with momentary power outage, and becomes essentially inactive. Therefore, self-excited other control cannot be performed, and only self-excited control is operated.

Note that such a phenomenon that occurs during a momentary power outage may occur even when the drive power supply voltage vcci has not risen sufficiently when the power is turned on.

[Problem to be solved by the invention]

In such a conventional example, only self-excitation control is operated during a momentary power outage or when the power is turned on, and the on period of the transistor Tri becomes longer, causing an excessive current to flow, and the speed at which the charge accumulated in the base of the transistor Trl is extracted becomes slower. There was also a fear that the switching loss would increase during off-time and the transistor Tri would be destroyed. Furthermore, when the energy stored in the inductors Ll and L2 is transferred to the capacitor CI side due to the flow of an overcurrent, an excessive voltage is generated across the capacitor C1, and the transistor Tr
It was also applied to both ends of l, and there was a risk of deterioration.

The present invention has been made to improve the above problems, and its purpose is to prevent excessive current and voltage from being applied to the switching element even when the output signal of the control means is not output due to some abnormality. It is also an object of the present invention to provide an inverter device that can prevent increases in switching loss, etc., and has higher safety.

[Structure of the invention]

(Means for Solving the Problem) The present invention provides a switching element connected to both ends of a DC power source via a resonant circuit including an inductor and a capacitor, and a switching element connected in parallel with either one of the resonant circuit and the switching element. a load connected to the resonant circuit, at least the resonant circuit, a feedback control section that detects the current in the resonant loop flowing through the load and turns on and off the switching element, and maintains the on state of the switching element for a predetermined period of time. and control means for outputting a control signal, the on-period of the switching element is set such that the high frequency output is suppressed when the output signal of the control means becomes substantially inactive. an abnormality detection means for controlling the
The abnormality detection means is characterized in that it includes a power supply circuit unit that supplies power obtained by detecting the current in the resonance loop.

(Function) By configuring the present invention as described above, even if the output signal of the control means is not output due to some abnormality, application of excessive current and voltage to the switching element and increase in switching loss can be prevented. This makes it possible to provide an inverter device with higher safety.

(Example) Hereinafter, the present invention will be explained in detail based on examples.

FIG. 1 shows the first embodiment of the present invention, and the configuration different from the conventional example shown in FIG. 7 is that the current iL in the resonance loop is detected to obtain the voltage. Then, this voltage is rectified and smoothed (not shown) to obtain the drive power supply voltage V.
Power supply circuit section C that obtains CC2 (!:, this power supply circuit section C
The abnormality detection means which receives the supply of the drive power supply voltage V[C2 from the control means B and controls the on-period of the switching element mTrl in the direction of suppressing the high frequency output when the output signal of the control means B becomes substantially inactive. The point is that it is equipped with the following. In addition,
Parts having the same functions as those of the conventional example are given the same reference numerals and redundant explanations will be omitted. Here, the abnormality detection means generates an on-off signal for a predetermined period in synchronization with the self-oscillation operation when the driving power supply voltage V CC2 is applied to the switching element S2 connected in parallel between the control terminals of the transistor Tri. is configured to output.

With this configuration, when the drive power supply voltage VCCI of the control means B decreases for some reason such as during a momentary power outage or when the power is turned on, the output signal from the control means B stops or the transistor Tr2 is substantially turned off. Even if driving is not possible, the current iL flowing in the resonance loop formed through the resonance circuit A and the discharge lamp La is detected and the drive power supply voltage V CC2 is obtained by the power supply circuit section C. By doing so, it is possible to drive the abnormality detection means.

Therefore, the on-period of the transistor Tri can be set to a shorter period than the on-period due to the self-oscillation operation using the signal output from the abnormality detection means, so that it is possible to control the high frequency output in a direction that limits it.

FIG. 2 shows a second embodiment of the present invention, and the configuration different from the conventional example shown in FIG. 7 is that both ends of the secondary winding N2 of the current transformer CT are connected between the control end of the transistor Tr2. This point is connected to the resistor R2 via the resistor R2.

By obtaining the power source for turning on and off the transistor Tr2 from the current transformer CT, the drive power supply voltage V CCI of the control means B is reduced, and the output signal from the control means B stops or substantially drives the switching element S1. Even if it is not possible to
Since the transistor Tri and the transistor Tr2 are turned on and off almost simultaneously, the transistor Tri can always be turned off.

Next, FIG. 3 shows a third embodiment of the present invention, and the configuration different from the embodiment shown in FIG. 2 is that a diode D3 is connected in series with a resistor R2, and a switching element S
A transistor Tr3 and a diode D2 connected in anti-parallel with the transistor Tr2 are provided as the transistor Tr3.

With this configuration, even when no signal is output from the control means B as in the second embodiment, the transistor Tr2 is always turned on without shifting to self-oscillation operation. Therefore, the high frequency output operation can be stopped.

FIG. 4 shows a fourth embodiment of the present invention, and the configuration different from the embodiment shown in FIG. 1 is that a secondary winding is provided in the inductor L2 to obtain a DC voltage. A power supply circuit section C and an abnormality detection means for detecting the emitter current flowing through the transistor T1 and limiting the on-period of the transistor Tri to suppress the high frequency output voltage when a current exceeding a predetermined value flows are provided. This is the point.

Here, the power supply circuit section C includes a secondary winding provided in an inductor L2, which is an oscillating circuit element, a rectifier DB that rectifies the voltage generated between the windings, and a smoothing capacitor that smoothes the output. The rectified and smoothed driving power supply voltage VCC2 is applied to the abnormality detection means as a driving voltage. The abnormality detection means is an emitter resistor RIO connected between the emitter of the transistor Tri and the circuit ground, and a voltage VRIO across the emitter resistor RIO and a reference voltage V.
A first comparator CP1 that compares l and ko(7)
Resistor R11, resistor R12, and resistor R13 that start operation upon receiving the output when both Q voltage VRIO > reference voltage ■1
Capacitor C3, diode D3. Second comparator CP2. It is composed of a monostable multi-circuit made up of a reference voltage V2 and a transistor Tr4.

With this configuration, the signal from the control means B is not output, and the transistor T shifts to self-oscillation operation.
If the current flowing through ri increases abnormally, the voltage VRIO across the emitter resistor RIO of the abnormality detection means exceeds the preset reference voltage V1, and the monostable multi-circuit starts operating. The transistor Tr4 connected between the control terminals of the transistor Tri can be turned on and off in a direction that can control the high frequency output voltage.

FIG. 5 shows a fifth embodiment of the present invention, and the configuration different from the embodiment shown in FIG. 3 is that the resonant circuit A is connected in series with the transistor Tri.
ri, a diode DlO connected in antiparallel, and a resonance capacitor CIO connected in parallel with the discharge lamp La.
A third winding N3 of a current transformer CT is provided to supply a voltage for self-excited oscillation between the control terminals of the transistor TrlO. In this way, the third embodiment may be applied to a so-called half-bridge inverter circuit.

Furthermore, FIG. 6 shows a sixth embodiment of the present invention, and the configuration different from the embodiment shown in FIG. 1 is that a secondary winding is provided in the inductor L1 to the resonance circuit, and this voltage The point is that the power supply circuit section C is obtained by rectifying and smoothing.

With this configuration, the drive power supply voltage V C of the abnormality detection means can be adjusted without providing a separate current transformer.
C2 can be obtained.

〔Effect of the invention〕

As described above, the present invention provides an abnormality detection means for controlling the ON period of the switching element in a direction to suppress the high frequency output when the output signal of the control means becomes substantially inactive, and the abnormality detection means. Since it is equipped with a power supply circuit unit that supplies power obtained by detecting the current in the resonant loop, even if an abnormality occurs in the control means, there is no need to apply excessive current or voltage to the switching elements, increase switching loss, etc. This has the remarkable effect that it is possible to prevent this and provide an inverter device with higher safety.

[Brief explanation of drawings]

1 to 6 are circuit configuration diagrams showing first to sixth embodiments of the present invention, and FIG. 7 is a circuit configuration diagram showing a conventional example of the present invention. A... Resonance circuit, B...-control means, C... power supply circuit section, D... abnormality detection means, E... DC power supply, F...
...Feedback control unit, switching element, La...load.

Claims (1)

[Claims] (1) A DC power source, a resonant circuit including an inductor and a capacitor, and a switching element connected to both ends of the DC power source via a resonant circuit, in parallel with either the resonant circuit or the switching element. a load connected to the resonant circuit, a feedback control unit that detects a current in the resonant loop flowing through the resonant circuit and the load, and drives the switching element on and off; an inverter device comprising: a control means for controlling an inverter, the abnormality detection controlling an on period of the switching element in a direction to suppress high frequency output when an output signal of the control means becomes substantially inactive; and a power supply circuit section for supplying power obtained by detecting the current in the resonance loop to the abnormality detection means.