JP2749315B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an inverter device.

[Prior Art] FIG. 4 shows a circuit configuration of an inverter device used in a conventional discharge lamp lighting device, in which transistors Q ₁ and Q ₂ are connected in series with a DC power supply (including a rectified voltage of an AC power supply) E. And diodes D ₁ and D ₂ are connected in parallel to the transistors Q ₁ and Q _{2 with} the polarity shown. (However, diodes D ₁ and D ₂ are not always necessary). In parallel with the transistor Q _1, a capacitor C _1, the capacitor C _2, the choke L _1,
A resonant circuit A including the discharge lamp l, a series circuit of a primary winding n ₁ of the drive transformer T ₁ is connected. With such a configuration, a series-type inverter circuit unit or a half-bridge-type inverter circuit unit is configured.

The driving transformer T ₁ has a secondary winding n _2, n _3, one of the secondary winding n ₂ is connected to a control resistor R ₁ of the transistor Q _1,
The other secondary winding n ₃ is connected to a control resistor R ₂ of the transistor Q _2.

The inverter circuit section shown is provided with a starting circuit B, the activation circuit B and a resistor R ₃ connected in series capacitor
C ₃ , and an ignition element such as a diac Q ₃ and a diode D ₃ .The connection point between the resistor R ₃ and the capacitor C ₃ is connected to one end of the diac Q ₃ , and the other end is connected to the transistor Q _2. Is connected to the base which is the control terminal of

The connection point of the resistor R ₃ and the capacitor C ₃ is a diode D ₃
It is connected to the collector of the transistor Q ₂ through.

The operation of the circuit described above is as follows. That is, the power switch SW is turned on, the capacitor C ₃ is charged through the resistor R _3. Next, the voltage of the capacitor C ₃ is changed to the diac Q ₃
Capacitor C ₃ reaches the breakover voltage of the discharges through the base-emitter junction of the transistor Q _2.
Transistor Q ₂ for the first time turned on by this discharge.

After that the oscillating operation is continued by the drive transformer T _1,
Those that by applying a voltage of the capacitor C ₂ to the discharge lamp l lighting a discharge lamp l. Because after the oscillation transistor Q ₂ is the capacitor C ₃ is not sufficiently charged current flows through the resistor R ₃ → the diode D ₃ → transistor Q ₂ when turned on, not lead to the break-over voltage of the diac Q _3, the diac Q ₃ Is turned off.

FIG. 5 shows a circuit configuration of another conventional example. When there is no load or an abnormality such as at the end of the life of the discharge lamp, the transistors Q ₁ and Q
A voltage corresponding to the current flowing through the ₂ is generated in the resistor R _4, the voltage and the reference voltage, high current transistor Q _1, the abnormal state such as no-load or discharge lamp end-of-life when compared with a relatively IC ₁ and Q _Two
When flowing in, and generates an output by conducting given to the gate of the thyristor Q ₄ via a resistor R ₇ to the output thyristor winding n ₄ of the drive transformer T ₁ through the diode D ₄ Q ₄ and short-circuited by, eliminating the output of the winding n _2, n _3, is intended to stop the oscillation of the inverter circuit, the thyristor Q ₄ conducts once since the holding current supplied by the resistor R _6, oscillation Stop connected. Note a resistor R _8, Tze Zener diode ZD ₁ constitutes a reference voltage generator providing a reference voltage to the comparator IC _1, diode D _5, the resistor R _5, the capacitor C ₄
Constitute a circuit for integrating the voltage across the resistor R _4.

[Problems to be Solved by the Invention] In the conventional example shown in FIG. 4, there is no problem when the discharge lamp 1 is normally lit. When the discharge lamp 1 reaches the end of its life, a high voltage due to resonance is output to the output terminal of the inverter circuit unit, which causes various problems.

The Figure 5 prior art are problems of the Figure 4 prior art is considered, in order to hold the stop of the oscillation of the inverter circuit, the thyristor Q ₄ are require switching element capable of self-holding of the triac or the like, Also, to supply holding current,
There is a problem that it requires a resistor R ₆ high power, further thyristor lit between the anode and cathode of Q ₄ steep voltage is applied, the inverter circuit oscillation stops the rendered conductive malfunctioning Also, there is a problem that the discharge lamp 1 does not light.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its purpose is to reliably detect various abnormal states and load states of a discharge lamp with a simple configuration and limit the oscillation output of the inverter circuit unit. To provide an inverter device with improved reliability.

Means for Solving the Problems The present invention provides an inverter circuit unit configured to supply high-frequency power to a load circuit unit by a switching operation of a switching element, and a reference voltage generation circuit that operates by a part of an output of the inverter circuit unit. , An auxiliary reference voltage source for generating a voltage lower than the reference voltage set by the reference voltage generation circuit, and a current for detecting the current of the load circuit for generating a detection voltage larger than the magnitude of the detected current. A detection circuit unit, and an output voltage from the detection circuit unit and a voltage of the auxiliary reference voltage source are applied to a comparison input terminal, and the voltage of the comparison input terminal and the reference voltage set by the reference voltage generation circuit unit are applied. A comparison circuit unit that generates an output when the applied voltage at the comparison input terminal exceeds the reference voltage, and an output voltage from the comparison circuit unit that is output in response to an abnormality of the load circuit unit. And an output control circuit for limiting the output of the inverter circuit.

[Operation] When the load circuit section is operating normally, the current flowing through the load circuit section is low and the detection voltage of the detection circuit section is lower than the reference voltage set by the reference voltage generation circuit section. No comparison output is generated, and the switching of the switching element of the inverter circuit section is continued.

Next, when the load circuit section becomes abnormal and the current flowing through the load circuit section increases, the detection voltage of the detection circuit section increases and exceeds the reference voltage, and the comparison circuit section generates a comparison output. When there is this comparison output, the output control circuit limits the output of the inverter circuit. When the output of the inverter circuit section is limited, power is not supplied to the reference voltage generation circuit section, and the reference voltage of the comparison circuit section becomes zero, but since the voltage is applied to the comparison input, the comparison circuit The comparison output of the unit is continuously output, and the output limitation of the inverter circuit unit by the output control circuit unit is maintained.

EXAMPLES The present invention will be described below with reference to examples.

First Embodiment FIG. 1 shows a circuit configuration of a first embodiment. An inverter circuit unit 2 configured to supply a high-frequency power to a load circuit unit 1 by a switching operation of a switching element, and an output of the inverter circuit unit 2 A reference voltage generating circuit section 3 which operates partially, a detecting circuit section 4 for detecting a current of the load circuit section 1 and detecting an overcurrent or an overvoltage for generating a detection voltage corresponding to the magnitude of the detected current; , and applies the output voltage E ₂ from the detection circuit section 4 to the comparison input terminal applied voltage of the comparator input by comparing the voltage with a reference voltage set by the reference voltage generating circuit 3 of the comparison input terminal A comparison circuit section 5 for generating an output when the voltage exceeds a reference voltage;
Of the inverter circuit section at the time of abnormality according to the output voltage from the
An output control circuit unit 6 for stopping the switching operation of
An auxiliary reference voltage source 7 which applies a constantly the reference voltage generating circuit unit 3 lower than the reference voltage E ₁ that is set by e in comparison input terminal of the comparator circuit 5, and is converted into a high frequency in the inverter circuit section 2 DC power supply (including a power supply obtained by rectifying and smoothing an AC power supply) E.

Figure 2 shows a specific circuit of the present embodiment, elements and circuits Figure 5 circuit the same symbols are those which form also has the same operation, the drive transformer T ₁ of the fourth winding n ₄ diode
A transistor Q ₄ connected through D ₄ ′ and a transistor
A resistor R ₉ connected between the base and emitter of Q _4, constitutes the output control circuit section 6 with a resistor R ₁₀ connected in series to the base.

Also provided in addition to the secondary winding n ₂₀ of the primary winding n ₁₀ is the choke L _1, and the secondary winding n _20, the resistance R in the secondary winding n ₂₀
Capacitor connected in parallel via ₁₁ and diode D ₆
Constitute a reference voltage generation circuit section 3 between C ₅ and a Zener diode ZD _1. And the detection circuit section 4 includes resistor R ₄ connected to the emitter of the switching element serving transistor Q ₂ of the inverter circuit 2, a diode D ₅ for rectifying the voltage developed across the emitter resistor R _4, charging the rectified output capacitor C ₄ to, and a parallel circuit of a resistor R _5.

Comparator circuit 5 is constituted by a comparator IC _1, inverting the input reference voltage E ₁ that is made constant by the Zener diode ZD ₂ of the reference voltage generating circuit 3 is applied to the non-inverting input terminal the detection detection voltage E ₂ from the circuit portion 4 is applied.

 Here, the vibration circuit A forms a load circuit unit.

However, in this embodiment, when the switch SW is turned on and the transistors Q ₁ and Q ₂ of the inverter circuit section 2 start oscillating by the starting circuit B, a current flows through the oscillation circuit A which is a load circuit section. Thus the output to the secondary winding n ₂₀ of choke L ₁ is stopped, the generator output is rectified by the diode D ₆ is further smoothed by the capacitor C _5, the output of this is rectified and smoothed in a certain further Zener diode ZD ₂ Regulated to voltage. The stabilized voltage is the reference voltage E _1. The reference voltage E ₁ is set at a higher value than the output voltage E ₁ of the load current detection circuit section 4 when normal. Well voltage when the current flowing through the load circuit is normal capacitor C ₄ was charged with the voltage generated in the resistor R ₄ by the emitter current of the transistor Q _2,
That output voltage E ₂ of the detecting circuit unit 4 compares the output of the comparator IC ₁ of the comparator circuit 5 for the reference voltage E ₁ or less becomes to "L", the transistor Q ₄ of the output control circuit section 6 does not operate.

Therefore, an output is normally generated in the windings n ₂ and n ₃ of the drive transformer T ₁ , so that the oscillation operations of the transistors Q ₁ and Q ₂ continue, and the lighting of the discharge lamp 1 in the load circuit section is maintained. .

Then when the discharge lamp l is not turned or or connected to Emiresu flows a large resonant current by choke L ₁ and capacitor C ₂ for resonance. At this time a large current also flows through the emitter resistor R ₄ of the transistor Q _2, the output voltage E ₂ of the detection circuit section 4 is increased, the E _2> E _1. The time comparison output of the comparator circuit 5 becomes "H" level, transistor Q ₄ is turned.

Therefore the winding n ₄ of the drive transformer T ₁ is short-circuited by the transistor Q _4, the voltage in the winding n _2, n ₃ is not induced, the oscillation transistor Q _1, Q ₂ is stopped. Since the induced voltage due to the winding n ₂₀ of choke L ₁ and oscillation stops is eliminated, the reference voltage E ₁ becomes zero. At this time, the capacitor C ₃ in the starting circuit B is charged through the resistor R ₃ , and the diac Q ₃
Reaches the breakover voltage, momentarily diac Q ₃ is turned on the transistor Q ₂ is turned on, the capacitor C ₄ of the detection circuit 4 is charged. Output voltage E ₂ of the detecting circuit unit 4 this operation is repeated thereafter will be maintained at a constant voltage e there. This voltage e is E ₂ = e> E ₁₀ .

That is, the detection circuit section 4 generates the output voltage e as the auxiliary reference voltage source 7.

Well comparator IC ₁ of the comparator circuit 5 by the detection voltage e maintains the comparison output of "H" level, and maintains the ON state of the transistor Q ₄ of result output control circuit section 6 oscillation stop of the inverter circuit 2 Hold.

Example 2 Figure 3 shows the circuit of this embodiment, the circuit of this embodiment connects the transistor Q ₅ between the base and emitter of the transistor Q ₄ of the output control circuit section 6, the transistor
The Q ₅ differs from the first embodiment in that a so as to control the output of the timer circuit section 8. The power supply _VDC of the timer circuit section 8 is obtained by dividing the DC power supply E with a resistor or the like.

Example high voltage is generated when 1, the discharge lamp l is lighted, becomes higher the detection voltage E ₂ of the detecting circuit unit 4, when the E _2> E _1, comparison of the comparator IC ₁ of the comparator circuit 5 The output becomes “H” level and the transistor of the output control circuit unit 6
Q ₄ is rendered conductive, there may be oscillation stop the inverter. But is obtained by the capacitance of the capacitor C ₄ in this order detecting circuit unit 4 to be started by providing a time lag, it is obtained by the more reliable the timer circuit unit 8 in Example 2.

That for the capacitor C ₆ of the timer circuit 8 when introduced the switch SW is in this embodiment is not charged, the timer circuit 8 obtained by dividing the power V _CD by resistors R _10, R ₁₁
Voltage e ⁺ is a non-inverting input of comparator IC ₂ voltage at the inverting input terminal e ^- higher than, the comparison output of the comparator IC ₂ becomes "H" level. Therefore the transistor Q ₅ is turned on base current flows through the transistor Q based on the resistance R ₁₅ of ₅ of the output control circuit section 6, a short circuit between the base and emitter of the transistor Q _4. Thus high detection voltage E ₂ than the reference voltage E ₁ is generated at the time of startup, the transistor Q ₄ also becomes comparison output is "H" level of the comparison circuit 5 is not turned on, the oscillation of the inverter circuit 2 is stopped Instead, the starting lighting is performed.

After the start lighting, the capacitor C _{6 of the} timer circuit section 8
Because There is charged through the resistor R _14, the voltage at the non-inverting input terminal of the comparator IC ₂ e ^- is inverted the input terminal becomes higher than the voltage e ^+, the output is "L" level of the comparator IC ₂ of the timer circuit section 8 now, transistor Q ₅ becomes non-conductive state.

Therefore and unloaded state after lighting, the discharge lamp l is likewise transistor Q ₄ is conducted to the first embodiment when an abnormal state, the oscillation of the inverter circuit 2 can be stopped.

[Effects of the Invention] The present invention provides an inverter circuit unit configured as described above,
Providing a reference voltage generation circuit portion operated by a part of the output of the inverter circuit portion, an auxiliary reference voltage source, a detection circuit portion, a reference voltage generation circuit portion, a comparison circuit portion, and an output control circuit portion; Since the output voltage from the detection circuit and the voltage of the auxiliary reference voltage source lower than the reference voltage set by the reference voltage generation circuit are applied to the comparison input terminal of the comparison circuit, abnormality occurs in the load circuit. Then, when the load current increases, a comparison output of the comparison circuit section is generated and the output of the inverter circuit section can be limited through the output control circuit section, and after the output is limited, the output limitation state of the inverter circuit section is maintained. Therefore, it is possible to obtain high reliability, and furthermore, it is only necessary to add a slight circuit configuration of the conventional circuit, so that the configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a specific circuit diagram of the same, FIG. 3 is a circuit diagram of a second embodiment of the present invention, FIG. 4 and FIG. FIG. 1 is a load circuit section, 2 is an inverter circuit section, 3 is a reference voltage generation circuit section, 4 is a detection circuit section, 5 is a comparison circuit section, 6 is an output control circuit section, and 7 is an auxiliary reference voltage source.

Claims (1)

(57) [Claims] An inverter circuit for supplying high frequency power to a load circuit by a switching operation of a switching element; a reference voltage generating circuit operating by a part of an output of the inverter circuit; An auxiliary reference voltage source that generates a voltage lower than the reference voltage set by the generation circuit unit, a detection circuit unit that detects the current of the load circuit unit and generates a detection voltage according to the magnitude of the detection current, The output voltage from the detection circuit unit and the voltage of the auxiliary reference voltage source are applied to a comparison input terminal, and the voltage of the comparison input terminal is compared with a reference voltage set by the reference voltage generation circuit unit to compare the comparison input terminal. A comparison circuit section that generates an output when the voltage applied to the terminal exceeds the reference voltage, and an inverter circuit that uses an output voltage from the comparison circuit section that is output in response to an abnormality in the load circuit section. Inverter apparatus characterized by comprising providing an output control circuit for limiting the output of.