JPH01298963A - Inverter device - Google Patents

Abstract

PURPOSE:To enhance safety by detecting the connecting state of a load circuit, providing an intermittent oscillation timer which is operated at the time of detection of no load, and thereby intermittently operating an inverter circuit. CONSTITUTION:The discharge lamp FL of a load circuit 2 is driven by an inverter circuit 1. The inverter 1 is composed of a switching element Q1, a LC resonance circuit made of an inductance L1 and a capacitor C1, etc., and its operating, frequency is controlled by turning ON, OFF the element Q1. A no load detector 3a is provided, and formed of a current detector for detecting the current of the output terminal of the circuit 1 to detect whether the circuit 2 is mounted or not. An output controller 4 selectively controls whether the circuit 1 is intermittently oscillated or continuously oscillated by the detector output, and an intermittent oscillation timer 6 is provided to set an intermittent oscillation time, a period to the circuit 1. Thus, a DC cutting capacitor is eliminated to conduct a no load detection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an inverter device that can automatically stop operating when a load circuit is removed and restart when the load circuit is reinstalled.

[Prior Art] Conventionally, in this type of inverter circuit device that includes a switching element and an LC resonant circuit and converts a DC power source into an AC power source and outputs it to an output terminal, a load circuit is connected to the output terminal of the inverter circuit. This has the disadvantage that it operates even under no-load conditions, which poses problems in terms of safety, reliability, power consumption, etc.

In addition, such an inverter device is often used when controlling the lighting of a discharge lamp using a load circuit (Fig. 8 shows a one-stone inverter device (discharge lamp lighting device) for lighting a discharge lamp. A circuit example is shown in which an LC resonant circuit is depleted by a capacitor C and an inductance L1, and a switching element Q, to which a DC power source E is applied via this LC resonant circuit, is turned on and off. A load circuit 2 consisting of a discharge lamp FL and a capacitor C2 is generated via an inductance L2.
It supplies high voltage to. However, on top of this
In the case where the C resonant circuit is added, when the discharge lamp FL is removed and the lamp becomes in a no-load state, a high voltage is outputted to its output terminal, which causes the following problem.

A. If a worker touches the output terminal in an unloaded state with the discharge lamp FL removed, there is a risk of electric shock because high voltage is generated.

B. When used as a discharge lamp lighting device (lighting equipment), if the secondary voltage exceeds 300V, it will not comply with the Electrical Appliance and Material Control Law and JIS standards.

Therefore, in order to solve the above-mentioned problems, it is considered that a no-load detection section is provided in the inverter device, and when a no-load detection signal is obtained, the operation of the switching element Q1 of the inverter circuit 1 is stopped or suppressed. It will be done. However, if the operation of the inverter circuit 1 is to be stopped or suppressed when there is no load, a function is required to detect the reinstallation of a load and cause the inverter circuit 1 to operate normally.

FIG. 9 shows a schematic groove diagram of a conventional example, and this inverter device has an inductance LI and a capacitor C.
A series circuit of an LC resonant circuit consisting of a parallel circuit of 1 and a switching element Q consisting of a transistor is connected to a DC power source E.
The main lighting circuit is configured by connecting the load circuit 2 to the LC resonance circuit in parallel via the inductance L2 and the DC cut capacitor C0, and the load side of the capacitor Co is connected to the voltage detection circuit. An output control section 4 is provided to which a no-load detection section 3b is connected, and which controls the operation of the switching element Q to stop or suppress the output of the inverter circuit 1 when a no-load detection signal is obtained. In the figure, reference numeral 5 denotes a drive section that drives the switching element Q1 of the inverter circuit 1 based on the output of the output control section 4.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, a capacitor C0 for DC cut, which is not originally necessary in the inverter circuit 1, is used.
It is necessary to cut the DC component by adding
Without this capacitor C8, it would be impossible to detect whether the load circuit 2 is attached due to the influence of the DC component on the circuit.
Inva automatically.

- Evening circuit 1 cannot be restarted.

However, if such a capacitor C0 is connected in series with the load circuit 2 and added to the main lighting circuit, the voltage applied to the load circuit will decrease and the operation of the inverter circuit 1 will be affected, causing the circuit There was a problem that the design was complicated.

The present invention has been made in view of the above point, and its purpose is to be able to perform no-load detection without adding a DC cut capacitor, and to provide a DC cut capacitor. An object of the present invention is to provide an inverter device that can eliminate the inconvenience caused by.

[! Means for Solving Problem I The inverter device of the present invention includes switching elements and L
An inverter circuit equipped with a C resonance circuit converts DC power into AC power and outputs it to the output terminal, and an inverter circuit that detects whether a load circuit is connected to the output terminal based on the operating current or operating voltage of the inverter circuit. A load detection section, an intermittent oscillation timer that operates when a no-load detection signal is output from the no-load detection section, and an inverter circuit that operates intermittently based on the intermittent oscillation timer output when the no-load detection signal is obtained. and an output control section that continuously operates the inverter circuit when the no-load detection signal is no longer obtained.

[Function] The present invention is configured as described above, and the no-load detection unit detects whether or not a load circuit is connected to the output terminal based on the operating current or operating voltage of the inverter circuit, and performs no-load detection. An intermittent oscillation timer is provided that operates when the no-load detection signal is output from the section, and when the no-load detection signal is obtained, the inverter circuit is operated intermittently based on the intermittent oscillation timer output. Equipped with an output control section that operates the inverter circuit continuously when the power is no longer available, and performs intermittent oscillation during no-load conditions.
Since no-load detection is performed using the operating current or operating voltage during intermittent oscillation, no-load detection can be performed without adding a DC cut capacitor, eliminating the inconvenience caused by installing a DC cut capacitor. It looks like this.

Embodiment 1 FIG. 1 is a block circuit diagram showing a schematic configuration of an embodiment of the present invention, in which the DC power source E is formed by a constant voltage power source obtained by rectifying an AC power source. Further, a load circuit 2 connected to the output end of the inverter circuit 1 is formed by a discharge lamp FL and a capacitor C2. In addition, inverter circuit 1
As in the conventional example, is formed by a switching element Q, an LC resonant circuit consisting of an inductance, and a capacitor C1, and the operating frequency can be controlled by turning on and off the switching element Q. A closed circuit is not formed when there is no load when the discharge lamp FL is removed, and no output current flows from the inverter circuit 1 when there is no load.

On the other hand, the no-load detection section 3a is formed of a current detection circuit that detects the current at the output end of the inverter circuit 1, and detects the operating current of the inverter circuit 1 at the output end and detects the operating current of the inverter circuit 1 at the output end. For example, a current transformer is inserted in series with the load circuit 2, and no-load detection is performed based on the secondary output of the current transformer.

Further, the output control section 4 selectively controls whether the inverter circuit 1 is operated in intermittent oscillation or continuous oscillation based on the output of the no-load detection section 3a, and also controls the frequency at which the switching element Q1 of the inverter circuit 1 is turned on. (set higher than the normal operating frequency at the start of operation and gradually bring it closer to the normal operating frequency) to control the output, and the switching element Q of the inverter circuit 1 is driven by the output of the output control section 4. It is controlled via section 5.

Further, the intermittent oscillation timer 6 sets the time and cycle for causing the inverter circuit 1 to oscillate intermittently when the no-load detection signal is output from the no-load detection section 3a.
Any device may be used as long as it is formed using a crystal oscillator or a CR time constant circuit and outputs a pulse signal with a constant pulse width at regular intervals.

Note that as shown in FIG. 2, a no-load detection section 3b consisting of a voltage detection circuit may be provided. In this case, when the inverter circuit 1 operates intermittently during no-load, the output voltage of the inverter circuit 1 is If the voltage does not stabilize immediately, it is necessary to provide a voltage detection prohibition timer 7 to prohibit the voltage detection operation until the voltage at the output terminal stabilizes.

Furthermore, in each of the above embodiments, current detection or voltage detection is performed at the output end of the inverter circuit 1 to detect whether or not the load circuit 2 is attached. It goes without saying that the presence or absence of the load circuit 2 may be detected by checking the operating current or operating voltage.

The operation of the embodiment will be described below. Now, in a state where the operation of the inverter circuit 1 has stopped under no load,
The output of the no-load detector 3a becomes "L" and a no-load detection signal is output, causing the intermittent oscillation timer 6 to operate, and at the same time, the output controller 4 fixes the operating frequency of the inverter circuit 1 to a high mode. Ru. When the output of the intermittent oscillation timer 6 becomes ``H'', the driving section 5 drives the switching element Q of the inverter circuit 1 at a frequency higher than the operating frequency in the normal state, but immediately the intermittent oscillation timer 6 outputs. becomes L', so the switching element Q,
drive is stopped. Therefore, the intermittent oscillation timer 6
When the output is "H", inverter circuit 1 operates in a pulsed manner and load circuit 2 is not installed,
Since the output end of the inverter circuit 1 is open, "L"' is output from the no-load detection section 3&, and the above operation is repeated until the load circuit 2 is reinstalled.In this case, the inverter circuit 1 performs intermittent oscillation, so high voltage is not output to the output terminal of inverter circuit 1, and there is a risk of electric shock to the worker when reinstalling load circuit 2 (when connecting discharge lamp FL). Inverter equipment (discharge lamp lighting device) that complies with JIS standards and the Electrical Appliances and Materials Control Law.
can be realized.

On the other hand, when the load circuit 2 is reinstalled, the operating current of the inverter circuit 1, which operates intermittently during no load, is detected and "H" indicating load reinstallation is output from the no load detection section 3a. , the signal from the intermittent oscillation timer 6 is no longer output, the inverter circuit 1 performs continuous oscillation operation, and at the same time the signal that fixed the output control section 4 at a frequency higher than the normal operating frequency is also cut, so the inverter circuit 1
The operating frequency gradually shifts to the normal operating frequency, and the inverter circuit 1 automatically restarts to supply power to the load circuit 2. Note that when the no-load detection section 3b is formed using a voltage detection circuit, the voltage detection prohibition timer 8 operates immediately after the inverter circuit 1 starts intermittent oscillation, and voltage detection is disabled until the output terminal voltage is stabilized. It will be prohibited.

By the way, in the inverter circuit 1 composed of the LC resonant circuit and the switching element Q, the switching element Q,
When the switching element Q is turned on and off by applying a DC power supply E through the LC resonant circuit to Both the current flowing through Q1 and the voltage applied become high values. Furthermore, when the on-period of the switching element Q is lengthened, these values become even higher. This is because the on-period of the switching element Q1 becomes longer, and the current flowing through the inductance L1 increases, causing the inductance to increase! This is thought to be due to the fact that when the switching cable Q1 is turned off due to an increase in the electromagnetic energy L12/2 multiplied by F, the increased energy is charged into the capacitor C1, resulting in a high value. In general, when lighting a discharge lamp, the lamp voltage is kept lower than the discharge start voltage when the inverter starts operating, and a preheating current is passed through the filament of the discharge lamp for a certain period of time. It is said that it is good for lamp life to start discharge by increasing the lamp voltage higher than the discharge starting voltage after the lamp has been preheated. Therefore, in particular, when lighting a discharge lamp at high frequency using an inverter device, a period of high operating frequency (preheating period) is set immediately after the inverter device starts operating, taking into account the preheating and transient state of the discharge lamp. After preheating, it is necessary to lower the operating frequency to start discharge. Further, even when the load circuit 2 is other than a discharge lamp, it is better to provide a period in which the operating frequency is set high immediately after the start of operation to protect the switching element Q. Therefore, in the embodiment, the output control unit 4 is configured such that the operating frequency of the inverter circuit 1 immediately after the start of operation is set higher than the normal operating frequency, and is gradually lowered to the normal operating frequency. That's what I'm doing.

FIG. 3 shows a specific circuit example, in which the present invention is applied to an inverter device for lighting a discharge lamp using a single-stone inverter circuit 1, and the DC power source E is a constant voltage source obtained by rectifying the AC power source. A DC power source E is formed by the power source and connected to the DC power source E through an LC resonant circuit consisting of a capacitor C9 and an inductance L1.
The switching element Q1 to which is applied is turned on and off by the drive circuit 5a, and the voltage across the LC resonant circuit is connected to the discharge lamp FL through the inductances (2) and (2).
and a load circuit 2 consisting of a capacitor C2. In the figure, CP + -CP 2 is a comparator, 0
2-Q are transistors, D, ~D are diodes, R
8-R14 is a resistor, C,, C, is a capacitor, diode D1 is a diode for flowing a feedback current, and control power supply Vc is supplied from DC power supply E via resistor R. .

Here, the no-load detection section 3a that detects the non-power supply side voltage of the inductance L2 is formed using a comparator CP2, and the voltage at the detection point is connected to the series circuit of the resistors R131RI4 via the reverse current blocking diode D. The voltage applied and divided by the resistors RI3jRI4 and the resistor R,
,,R,2 is compared with the reference voltage vs2 set by the comparator CP2, and the comparator CP2 is output when the load circuit 2 is installed.
The "H" output voltage of is determined by the resistor R1°.

Here, in a no-load state in which the discharge lamp FL is removed and the load circuit 2 is not attached to the output end of the inverter circuit 1, the output of the comparator CP2 of the no-load detection section 3b becomes "L" and there is no load. A load detection signal is output, and at this time,
In the output control section 4, the capacitor C1 is charged from the control power source Ve via the resistor R8, and when the voltage across the capacitor C4 becomes higher than the reference voltage Vs set by the resistor R9 and R6, the output of the comparator CP is H" and a preheating return signal is output. This preheating return signal is sent to the drive unit 5.
a, the operating frequency of the inverter circuit 1 is set higher than the normal operating frequency by the drive unit 5a,
To suppress an overvoltage applied to a load circuit 2 in a transient state to a sufficiently low level. At the same time, the "H" output of the comparator CP1 turns on the switching element Q2, and the base of the switching element Q is grounded.
, stops driving.

In the intermittent oscillation timer 6, the capacitor C1 is charged from the control power supply Vc via the resistor R3, and when the capacitor C1 is charged to a predetermined voltage, the transistor Q is turned on via the resistor R4, and the transistor Q2 is turned on. Since the base is grounded and the transistor Q2 is turned off, the switching element Q1 is driven at a high frequency according to the drive signal from the drive circuit 5a, and the inverter circuit 1 operates for a certain period of time. At this time, even in a no-load state, capacitor C3
and inductance L resonate, so comparator CP2 outputs an "H" signal indicating the load state, turns on transistor Q, discharges capacitor C1, and turns off transistor Q3. Furthermore, comparator CP
The "H" output of , turns on the transistor Qs, discharges the capacitor C1, and outputs 'L' from the comparator CP.However, when the operation of the inverter circuit 1 passes the transient state, it is in a no-load state. The voltage at the detection point drops, the output of the comparator CP2 goes low, and the driving of the switching cable Q is stopped until the capacitor C1 is charged. Note that since the LC resonant circuit consisting of the inductance L and the capacitor C1 has an internal resistance, the vibration caused by the LC resonant circuit becomes a damped vibration, and if the switching element Q1 is not turned on, the liquid decreases and stops, and the output terminal high voltage is not output.

Next, when the discharge lamp FL is connected and the load circuit 2 is reinstalled, when the intermittent oscillation of the inverter circuit 1 starts, the voltage at the detection point fluctuates greatly due to the resonance of the LC resonant circuit, and the comparator CP2 outputs H'' and 'L'' alternately according to the operating frequency of the inverter circuit 1. Therefore, capacitor C1 repeats charging and discharging, and the voltage across capacitor C1 increases to comparator CP1.
When the reference voltage Vs1 is no longer reached, the comparator CP1
The output is always "L" and no preheating return signal is input to the drive circuit 5a. Further, since the transistor Q2 that had stopped driving the switching element Q1 is turned off, as a result, the switching element Q1 gradually shifts from a high frequency to a normal operating frequency, and the inverter circuit 1 also operates in continuous oscillation according to that frequency. Power is automatically supplied from the inverter circuit 1 to the load circuit 2, and the discharge lamp FL is lit.

In addition, Fig. 4 shows the base voltage of the switching element Q during intermittent oscillation operation in a no-load state, and the voltage at the detection point under load and no-load. , when there is no load, the reference voltage V
Since the voltage does not exceed s2, capacitor C1 is not discharged.

FIG. 5 shows another embodiment, in which drive circuits 5m, 5b
A pair of switching elements Q+a*Q driven by
1b, capacitor CI + 1% inductance. The present invention is applied to an inverter device using a half-bridge type inverter circuit, 1a, formed in
In the figure, CP 3 is a comparator, ■ is an inverting circuit, and Q+
. ~Q13 is a transistor, DlatD1b, D
, 3 are diodes, R2 and -R2 are resistors, C1 is a capacitor, T is an isolation transformer, and CT is a current transformer.

Now, when load circuit 2 is removed and becomes a no-load state,
Since no current flows to the output terminal of the inverter circuit 1a (the non-power supply side of the capacitor CIO), this state is current)
It is detected by the secondary current of the lance CT. That is,
Karen)) When a current flows through the primary side of the lance CT, a current also flows through the secondary side via the diode DI3 and the resistors R26 and R26, and a voltage is generated across the resistor R26, and this voltage causes the transistor Q13 to flow. is turned on, the charge in the capacitor CI+ that had been charged through the resistor R22 is discharged, and the voltage across the capacitor C8 becomes lower than the reference voltage Vs2 determined by the resistor R211R231R24.
Comparator CP's high output becomes "L".

On the other hand, in the case of no-load condition, 2 of Karen)) Lance CT
Since no current flows to the next side and the transistor Q13 is not turned on, the charge in the capacitor C11 is not discharged and the output of the comparator CP becomes "H".

When the output of this comparator CP becomes "■4", a preheating return signal is input to the drive circuits 5a and 5b, and the operating frequency of the drive circuits 5a and 5b is fixed to the preheating mode higher than the normal operating frequency. . Furthermore, the transistor Q l 1 is turned on via the insulating transformer T, and the base of the transistor Q+b is grounded.
Stops driving.

Also, the frequency w from the intermittent oscillation timer 6 as shown in FIG.
IT outputs a signal with on-period t, and this signal No. 43 is inverted by inverting circuit I and applied to the base of transistor Q to via transistor Q 12, and when the output of comparator CP becomes H'' , transistor Q1□ turns on, and the output of inverting circuit I becomes transistor Q.
Since it is input to the base of 10, intermittent oscillation timer 6
When the output signal of is H'', transistor Q+a is driven by drive circuit 5a, and intermittent oscillation operation is started.

Transistors Q and a are intermittently driven and the inverter circuit 1
If load circuit 2 is reinstalled while a is intermittently oscillating at a high frequency, the output of comparator CP 3 becomes "L".
The operating frequency is gradually shifted from the high frequency of the preheating mode to the normal lighting frequency, and the discharge lamp FL is safely and normally lit.

In addition, Fig. 7 (,) to (e) shows the base voltage of transistor Q, a and the primary current of the lance CT under load and no load.
) No current flows through the 1st side of the lance CT.

[Effect 1 of the invention] The present invention is configured as described above, and the no-load detection section detects whether or not a load circuit is connected to the output terminal based on the operating current or operating voltage of the inverter circuit, and detects whether or not there is no load. An intermittent oscillation timer is provided that operates when the no-load detection signal is output from the detection section, and when the no-load detection signal is obtained, the inverter circuit is operated intermittently based on the intermittent oscillation timer output, and the no-load detection signal is The inverter circuit is equipped with an output control section that operates the inverter circuit continuously when the inverter is no longer able to obtain the output voltage, and performs intermittent operation when there is no load.
Since no-load detection is performed using the operating current or operating voltage during intermittent oscillation, no-load detection can be performed without adding a DC cut capacitor, eliminating the inconvenience caused by installing a DC cut capacitor. There is an effect.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of one embodiment of the present invention, Fig. 2 is a block circuit diagram of another embodiment of the above, Fig. 3 is a specific circuit diagram of the same, Fig. 4 is an explanatory diagram of the same as the above, Figure 5 is a specific circuit diagram of another embodiment, Figures 6 and 7 are explanatory diagrams of the same operation as above, Figure 8 is a block circuit diagram of a conventional example, and Figure 9 is a block circuit diagram of another conventional example. be. 1 is an inverter circuit, 2 is a load circuit, 3 a, 3 b
4 is a no-load detection section, 4 is an output control section, 5 is a drive section, and 6 is an intermittent oscillation timer. Agent Patent Attorney Ishi 1) Ai 7 Figure 1 Figure 2 Figure 9 ■

Claims (1)

[Claims] (1) An inverter circuit that is equipped with a switching element and an LC resonant circuit and converts DC power into AC power and outputs it to the output terminal, and a load circuit is connected to the output terminal based on the operating current or operating voltage of the inverter circuit. an intermittent oscillation timer that operates when a no-load detection signal is output from the no-load detection section;
An inverter device comprising an output control unit that operates an inverter circuit intermittently based on an intermittent oscillation timer output when a no-load detection signal is obtained, and continuously operates the inverter circuit when a no-load detection signal is no longer obtained.