JP3978902B2 - Ozone generator short circuit detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a short-circuit detection circuit for an ozone generator tube that operates by receiving a high-frequency voltage output from an inverter.
[0002]
[Prior art]
As a conventional short circuit detection circuit for this type of ozone generator tube, there is known a circuit that detects a current change state at a predetermined position on an inverter circuit that changes in response to a short circuit of an ozone generator tube. It is an illustration of the main circuit diagram of the current source inverter apparatus which drives an ozone generator tube, and is an example of a main circuit in the case where the ozone generator tube short-circuit state is detected by detecting an increase in the DC intermediate current of the inverter device.
[0003]
In FIG. 4, reference numeral 5 denotes a current type inverter device, which includes a PWM control type converter 5a using a power transistor, a DC reactor DCL, and an inverter 5b using a self-extinguishing thyristor element GTO. 2 is a single-phase step-up transformer, 3 is an ozone generator tube, ACL is an AC reactor connected in parallel to the ozone generator tube 3, and HCT is a DC current detection signal Sidc of a DC intermediate circuit between the converter 5a and the inverter 5b. This is a Hall element type DC current transformer that outputs.
[0004]
If a short circuit occurs in the ozone generator tube 3 in the illustrated main circuit configuration, the shared voltage of the ozone generator tube 3 viewed from the inverter side via the step-up transformer 2 becomes zero or an extremely low value close to zero. Causes a commutation failure of the thyristor element in the circuit, and causes an increase in the current of the DC intermediate circuit.
Therefore, the ozone generator tube short-circuit state is detected by detecting the state where the DC intermediate circuit current detection signal Sidc output from the DC current transformer HCT is equal to or greater than a predetermined current set value by a current comparison circuit (not shown). I can do it.
[0005]
[Problems to be solved by the invention]
As described above, as a short circuit detection circuit for an ozone generating tube that operates in response to a predetermined high-frequency voltage output from the inverter or its boosted voltage, the conventional circuit is designed to detect a current change at a predetermined position on the circuit of the ozone generating tube driving inverter. A detection signal, for example, an increase detection signal of a DC intermediate current in a current source inverter device is used as a required short-circuit detection signal.
[0006]
However, if a clear current change does not occur on the drive inverter circuit when the ozone generator tube is short-circuited, the circuit configuration for detecting the ozone generator tube short-circuit by detecting the current change cannot be applied. .
[0007]
For example, in the case of a voltage-type inverter device in which an AC rectified voltage supplied via a smoothing capacitor is used as the input DC voltage and a required AC voltage is obtained by a PWM switching operation by a power transistor, a short circuit occurs in the ozone generator tube that forms the load. When any abnormality that causes an excessive state of load current, including when it occurs, rapid current limit control is performed, so no significant change in inverter input / output current occurs, and short circuit due to current change as described above Application of the detection circuit is difficult.
[0008]
In view of the above, the present invention provides a short circuit detection circuit for an ozone generator tube that operates in response to a predetermined high-frequency voltage output from the inverter or its boosted voltage, and therefore does not depend on the presence or absence of a significant current change in the inverter device. It is an object of the present invention to provide an ozone generator tube short circuit detection circuit that enables clear detection of the ozone generator tube regardless of the current type or voltage type in the apparatus.
[0009]
[Means for Solving the Problems]
To achieve the above object, an ozone generator tube short-circuit detection circuit according to the present invention is a short-circuit detection circuit for an ozone generator tube that operates by applying a high-frequency voltage output from an inverter or a boosted voltage thereof. A power average circuit that calculates an average value of output power from detected values of both voltage and output current, a first level comparator that compares the power average value output by the power average circuit and its monitoring level setting value; A second level comparator that compares the set value of the output power of the inverter and the monitoring allowable level set value; and a logic circuit that receives the outputs of both of these comparators, and the output power of the inverter the actual value is short-circuited state of the ozone generating tube state is smaller than the predetermined monitoring level setting value of the setting value is larger than a predetermined monitoring acceptable level despite the output power Judgment shall be output ozone generating tube short detection signal from said logic circuit.
[0010]
As described above, the present invention does not depend on the presence or absence of a significant current change in the inverter device, but detects a reduction change in the input power of the ozone generation tube that is proportional to the ozone generation amount, and thus the output power of the inverter device. Thus, the circuit is constructed so as to obtain an ozone generator tube short-circuit signal.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS. Here, FIG. 1 is a short circuit detection circuit diagram of an ozone generator tube, FIG. 2 is a short circuit detection characteristic diagram of the ozone generator tube, and FIG. 3 is a main circuit diagram of a voltage source inverter device for driving the ozone generator tube.
First, in FIG. 3, reference numeral 1 denotes a voltage-type inverter device, which is composed of a rectifier 1a, a smoothing capacitor Cf, and a PWM-controlled inverter 1b using a power transistor having a diode in antiparallel. Single-phase step-up transformer, 3 is an ozone generator tube, PT is a transformer for instrument, and CT is a current transformer for instrument.
[0012]
In addition, Sv is an inverter output voltage detection signal by PT, Si is an inverter output current detection signal by CT, and Sp is a setting signal PS of an inverter output power set by a power setting unit installed in the inverter 1b. .
As described above, the ozone generation amount and the input power of the ozone generation tube are in a proportional relationship. Therefore, the setting of the inverter output power that forms the input power of the ozone generation tube is equivalent to the setting of the ozone generation amount.
[0013]
Next, in the ozone generation tube short circuit detection circuit diagram shown in FIG. 1, 11 is an output current detector that receives a detection signal Si of the inverter output current and outputs a predetermined conversion signal, and 12 is a detection signal Sv of the inverter output voltage. An output voltage detector 13 for receiving a predetermined conversion signal and multiplying the current conversion signal and the voltage conversion signal respectively output by the detectors 11 and 12 to output an inverter output power value as a scalar product of both signals. 14 is a power averaging circuit that receives the output signal of the multiplier 13 and outputs an average value P0, and 16 is a first power setting that sets a monitoring level value POL for the average value P0 of the inverter output power. 15 is a first level comparator that compares the power signal values PO and POL and outputs an L level logic signal when PO is smaller than POL, and 18 is the inverter. A second power setting unit 17 for setting a monitoring allowable level value PSL with respect to the set value PS of the output power, 17 compares the two power signal values PS and PSL, and when PS is greater than PSL, the L level logic signal , A second level comparator 19 which is an OR logic element which outputs a logic signal Sf with the output logic signals of both level comparators as inputs.
[0014]
In the OR element 19, when both the output signals of the level comparators 15 and 17 are at the L level, that is, the set value PS of the inverter output power corresponding to the ozone generation amount is larger than the monitoring allowable level value PSL. In spite of the fact that the actual value PO of the inverter output power is smaller than the monitoring level value POL and the inverter output cannot be increased, the logic signal Sf is used as the short circuit detection signal of the ozone generator tube. Is output as
[0015]
Further, the ozone generation tube short-circuit detection characteristic diagram shown in FIG. 2 shows the range where the formation condition PS> PSL, PO <POL of the logic signal Sf as the short-circuit detection signal as described above is satisfied. The short circuit detection of the ozone generating tube is performed by the related specifications PO and PS of the inverter output power that is proportional to the ozone generation amount without depending only on the change of the output current detection signal Si. It shows a pattern.
[0016]
In the embodiment of FIG. 1, the level comparator 17 is configured to output an L level logic signal when the power signal value PS is larger than the PSL.
On the other hand, if the level comparator 17 is configured to output an H level logic signal when the signal value PS is greater than the PSL, and a NOT element is connected to the output side thereof, the NOT element An L level logic signal similar to the above case is output.
[0017]
That is, the logic circuit composed of the level comparators 15 and 17 and the logic elements connected thereafter is not limited to the circuit configuration of the embodiment of FIG. 1, and PS> PSL and PO < It is only necessary to be logically configured to detect the establishment of both conditions of POL as a short circuit state of the ozone generating tube and output a predetermined detection signal.
[0018]
【The invention's effect】
According to this invention, the short circuit detection circuit of the ozone generator tube that operates by applying the output high-frequency voltage of the inverter or its boosted voltage, calculates the average value of the output power from the detected value of the output voltage and output current of the inverter. A power average circuit, a first level comparator for comparing the power average value output from the power average circuit and its monitoring level setting value, a setting value of the output power of the inverter and a monitoring allowable level setting value thereof, A second level comparator for comparing the outputs of the two comparators and a logic circuit having the outputs of these comparators as inputs, although the set value of the output power of the inverter is greater than a predetermined allowable monitoring level. without actually value determines the state is smaller than the predetermined monitoring level setting value and short-circuit state of the ozone generating tube, of the output ozone generating tube short detection signal from the logic circuit of the output power Therefore, the input power of the ozone generator tube is proportional to the amount of ozone generated, regardless of whether there is a significant current change in the inverter device, and regardless of the current type or voltage type of the inverter device. Therefore, it is possible to detect the short circuit of the ozone generator tube by detecting the change in the output power of the inverter device, and to avoid the damage due to the operation of the ozone generator tube in the short circuit state.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a short circuit detection circuit of an ozone generator tube showing an embodiment of the present invention. FIG. 2 is a characteristic diagram of a short circuit detection circuit of an ozone generator tube corresponding to FIG. Main circuit diagram [Fig. 4] Main circuit diagram of current source inverter device corresponding to the embodiment of the prior art [Explanation of symbols]
1 Inverter device (voltage type)
1a Rectifier 1b Inverter 2 Single-phase step-up transformer 3 Ozone generator tube 5 Inverter device (current type)
5a converter 5b inverter 11 output current detector 12 output voltage detector 13 multiplier 14 power averaging circuit 15 (first) level comparator 16 (first) power setter 17 (second) level comparator 18 ( Second power setting device 19 OR element ACL AC reactor Cf Smoothing capacitor CT Instrument current transformer DCL DC reactor HCT Hall element type DC current transformer PT Instrument transformer

Claims (1)

A short-circuit detection circuit for an ozone generator tube that operates by applying a high-frequency voltage output from the inverter or a boosted voltage thereof, and calculates an average value of output power from detection values of both the output voltage and output current of the inverter A circuit, a first level comparator for comparing the power average value output from the power averaging circuit and its monitoring level setting value, and a setting value of the output power of the inverter and its monitoring allowable level setting value. A second level comparator and a logic circuit that receives the outputs of both of these comparators as inputs, the output even though the set value of the output power of the inverter is larger than a predetermined monitoring allowable level. determining the actual value of the power and short-circuit state of the ozone generating tube state is smaller than the predetermined monitoring level setting value, it is output ozone generating tube short detection signal from said logic circuit Ozone generating tube short detection circuit according to claim.

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