JP5193086B2 - Discharge cell discharge circuit and discharge cell discharge circuit control system - Google Patents

Description

  The present invention relates to a silent discharge and a dielectric barrier discharge that occur when an alternating voltage is applied to a pair of planar electrodes in which electrodes on one side or both sides of a flat plate electrode with a predetermined interval are covered with a dielectric. In particular, the present invention relates to a discharge cell discharge circuit and a discharge cell discharge circuit control system used in a high-concentration ozone generator, an ozone water production apparatus, and the like.

In the ozone generation technology, there are methods and devices for generating ozone by silent discharge or creeping discharge. Specifically, a dielectric is interposed between the high-voltage electrode and the ground electrode so that a gap is formed between the two electrodes. Developed ozone generation method and device that constitutes a discharge cell and generates a high concentration of ozone by causing discharge by applying a high voltage between the electrodes while flowing oxygen gas through the gap between the electrodes Is being used. Ozone is used as a useful oxidative sterilizer, but is also widely used, for example, in the semiconductor manufacturing field. Conventionally, a circuit system for improving the amount of ozone generated has also been proposed in the high voltage generation circuit (discharge cell discharge circuit) for generating ozone.

FIG. 13 is a block diagram showing an ozone generation circuit of a discharge cell discharge circuit according to a conventional series resonance system. In FIG. 13, first , commercial AC power supplied from the nodes (R, S, T) to the rectifier (Ur) is full-wave rectified, and the direct current is smoothed by the smoothing capacitors (C10, C11) to become a direct current power source. The DC power is supplied to the inverter (Uj), and an AC voltage is formed between the midpoints of the inverter (Uj). The alternating voltage formed by the inverter (Uj) is converted (boosted) into a high voltage by a step-up transformer (T10), and a discharge cell (Ds) having a dielectric interposed through an inductor (L1) is connected between both electrodes. To be applied. The first purpose of providing the inductor (L1) is to suppress excessive current flowing transiently to the switching elements (Q10, Q11) on the inverter (Uj ) and to protect the switching elements (Q10, Q11). is there. The second object is that the discharge cell (Ds) can be considered equivalent to a circuit in which a resistance component, a Zener diode, and a capacitance component are connected in parallel, so that the inductor (L1) and the discharge cell (Ds) This is because the inverter (Uj) is operated at the resonance frequency of the resonance part configured by the parasitic capacitance (Cm) of the inverter.

The tuning control unit (Us ′) takes in each waveform of the voltage between the electrodes of the discharge cell (Ds) and the current to the discharge cell (Ds), takes in each phase signal, and recognizes the phase difference between them. It has a function to do. For example, when the frequency of the voltage application drive of the resonance unit configured by the LC circuit is applied at the resonance frequency, the phase difference on the primary side of the transformer (T10) is close to zero, and on the secondary side of the transformer (T10). It is a known fact that the connection node voltage of a certain LC circuit is maximized. For example, even in Patent Document 1, by Rukoto combined frequency of the inverter and the resonant frequency, it is introducing the high voltage output can be obtained. Drive that drives the inverter (Uj) in order to make the phase difference between the current and voltage of the transformer (T10) zero in order to maximize the high voltage as the inverter, that is, the voltage application state in the discharge cell (Ds). A pulse signal matching the resonance frequency is transmitted to the circuit (Gq10).

  Next, FIG. 14 is an operation explanatory diagram of the switching elements (Q10, Q11) arranged on the inverter (Uj) in the series generation type ozone generation circuit shown in FIG. As shown in the figure, the DUTY ratio of each of the switching elements (Q10, Q11) of the inverter (Uj) is approximately 50%, and during the on-time of each of the switching elements (Q10, Q11), that is, both switching An appropriate extremely short period in which both elements are turned off is set and operated alternately, and the drive frequency of the inverter (Uj) is subjected to frequency modulation.

In particular, it is generally known that ozone generation is performed with high efficiency when a high voltage is applied by a resonance action in a discharge cell for generating ozone. In this case, the parasitic capacitance of the discharge cell (Ds) is known. The inverter (Uj) is driven at the resonance frequency by using the resonance frequency of the resonance part composed of the (Cm) component and the inductor (L1) connected in series to the discharge cell (Ds) to generate a high voltage. It is preferable to apply. At the same time, it is preferable to achieve zero current switching that performs switching when the current flowing through the switching elements (Q10, Q11) of the inverter (Uj) is zero, thereby reducing the switching loss and improving the efficiency as a power source. .

Here, the drive frequency at which the switching elements (Q10, Q11) operate will be described with reference to FIG. In FIG. 15, the horizontal axis represents frequency and the vertical axis represents resonance sharpness (Q). As described above, when the ozone concentration is set or adjusted high, the inverter (Uj) is operated in the vicinity of the resonance frequency, so that a high voltage can be applied to the discharge cell (Ds) , which is very high. Ozone generation efficiency can be obtained. Therefore, the inverter (Uj) is controlled at the resonance frequency (f0) calculated in advance in order to obtain the highest Q from the characteristics of the discharge cell (Ds). However, the change in the cooling conditions of the discharge cell (Ds), the change in the temperature of the discharge cell (Ds) due to the gas flow rate through the gap between the electrodes of the discharge cell (Ds), and the inter-electrode distance due to the life deterioration due to the discharge. changes, since the resulting changes actually resonance frequency frequency due to a decrease in the capacitive component of the discharge cell (Ds) is constant, there is not always possible to achieve the best efficiency drawbacks.

Further, in the case of adjusting an ozone generation amount, in particular by carrying out the operation in a region where the inverter (Uj) is the driving frequency deviates from the resonance frequency when the desired reduced the generation amounts, both of the discharge cells (Ds) In this method , a low voltage is applied between the electrodes . Therefore, there is a drawback that the switching elements (Q10, Q11) of the inverter (Uj) cannot achieve zero current switching. In addition, the leakage inductance existing in the step-up transformer (T10) is likely to generate noise, and there is a risk that the control system circuit may malfunction, and countermeasures for that must be taken.

  In order to reduce the ozone generation concentration, in this formula, a method is attempted in which the drive frequency of the inverter (Uj) is separated from the resonance frequency (f0), and the voltage applied to the discharge cell (Ds) is reduced. Yes. In this case, the control is performed at a frequency separated from the resonance frequency (f0) with a predetermined frequency region interval (Δf). Therefore, in this method, for example, the phase difference between the input signal and the output signal is detected using a PLL (Phase Locked Loop) technique, that is, an electronic circuit that matches the frequency of the reference frequency and the output signal, and the VCO (voltage By using a method of transmitting a signal having a precisely synchronized frequency by controlling a circuit loop and a circuit loop, the circuit frequency becomes complicated, and the resonance frequency (f0) Since the drive frequency of the inverter (Uj) is deviated, there is a problem that the efficiency is lowered in terms of ozone generation efficiency. Furthermore, if a higher frequency is selected as the direction in which the drive frequency is separated, the switching frequency increases, so there is a problem that the amount of heat generated by the switching element naturally increases. Furthermore, from the viewpoint of switching loss, the phase of the current and voltage do not match. For example, even when a large amount of current is flowing, the switching element must be cut off, so-called hard switching is performed. There is a drawback that the loss is increased and the noise is also increased.

  Furthermore, in the present formula, it has been described that it is best to set the drive frequency of the inverter (Uj) to the resonance frequency (f0). However, in actuality, an excessive voltage is applied to the discharge cell (Ds). As a result, the discharge cell (Ds) was destroyed. This is because the sharpness (Q) of resonance is large as described above, and at the same time, there is no means for limiting the power supplied to the inverter (Uj).

Further, when the drive frequency of the inverter (Uj) is constant according to the resonance frequency of the discharge cell parasitic capacitance (Cm) and the inductor (L1), the discharge cell (Ds) has its parasitic capacitance (Cm For example, when the discharge cell (Ds) is replaced, the resonance frequency may not be the same as that before the replacement depending on the replaced discharge cell, and the desired power consumption and the desired ozone concentration may be reduced. There was a problem that it could not be obtained.

  Further, when the bridge is driven at a constant frequency, for example, when the input power source is single-phase 50 Hz, the smoothing capacitors (C10, C11) have a ripple of 100 Hz after rectification, and the ozone generation concentration However, this swell of 100 Hz occurred, and there was a problem that the specified concentration was not obtained although it was an extremely short time. For this reason, it is necessary to prepare an electric capacitor having an extremely large capacity, and an increase in size cannot be avoided.

  In Patent Document 3, the inverter is driven at the resonance frequency using the resonance frequency of the resonance part formed by the parasitic capacitance component of the discharge cell, the transformer connected in series with the discharge cell, and the leakage inductance of the transformer, Although what controls to reduce switching loss and increase the efficiency as a power supply is described, the above-mentioned problems have not been solved.

  Patent Document 4 describes a method in which a switching element of an inverter is driven at a resonance frequency with a duty ratio of 50% and adopts a PDM (Pulse Density Modulation) method, but the above problems are solved. It wasn't.

  Patent Document 2 proposes a method of outputting a signal according to the polarity of the commercial AC power supply and avoiding fluctuations in the commercial power supply frequency by using the polarity of the voltage of the commercial AC power supply. The applied frequency of the inverter necessary for the inverter requires a high frequency of about 10 kHz to 50 kHz, and even if it is considered from the viewpoint of the efficiency of ozone generation by the resonance part, it cannot be a measure for solving the above problems.

FIG. 16 is a block diagram showing an ozone generation circuit of another conventional discharge cell discharge circuit. FIG. 17 is a diagram for explaining the operation of the switching elements (Q10, Q11) in the ozone generation circuit shown in FIG. The method in FIG. 16 is a method for controlling the ozone generation amount by performing PWM (Pulse Width Modulation) control in which the drive frequency is constant and the ON width is variable. In the embodiment shown in FIG. 16, since a very high ozone generation efficiency can be obtained during operation by applying a voltage at the resonance frequency as described above, therefore, the parasitic capacitance (Cm) and the inductor ( The resonance frequency is derived from the relationship with L2), and a high voltage is applied to the discharge cell (Ds) as a method in which the drive frequency is fixed in advance by the parallel resonance method. The power control unit (Us ″) manages the power to the discharge cell (Ds) and the voltage to the discharge cell (Ds) and feeds back to the drive unit (Gq20) that drives the inverter (Uj). is there.

  As shown in FIG. 17, the drive timing of the switching elements (Q20, 21, 22, 23) on the inverter (Uj) in FIG. 16 is constant while the period (T1) is constant in the state where the resonance state is obtained. (T2) is designed to be approximately 50% at maximum.

  However, in the discharge cell (Ds), the discharge voltage of the discharge cell (Ds) increases as the temperature and pressure increase, and the parasitic capacitance (Cm) component of the discharge cell (Ds) gradually increases. The resonance frequency also changes, and as a result, there is a problem that the drive frequency of the inverter (Uj) deviates from the resonance frequency.

  When it is desired to decrease the ozone generation concentration, the PWM on-time (T2) is decreased. In a general load such as a resistor, the voltage increases as the current increases, but the discharge cell (Ds) has a unique property. Specifically, when the on-time (T2) is decreased, the amount of energy to the discharge cell (Ds) decreases, the temperature of the discharge cell (Ds) decreases, and the discharge cell (Ds) The voltage decreases and the parasitic capacitance (Cm) also decreases. As a result, similarly, there is a problem that the drive frequency of the inverter (Uj) is greatly deviated from the resonance frequency.

If switching is performed out of the resonance state, the state immediately before the switching element is turned on is that voltage is present at both ends of the drain terminal and the source terminal of the switching element. Is stored, and at the moment when the switching element is turned on, the charge flows through the switching element as a short-circuit current, and is consumed as heat by the on-resistance of the switching element. On the other hand, in the state immediately before the switching element is turned off, a current flows between the drain terminal and the source terminal of the switching element. At this time, the switching element is turned off, so that a switching loss occurs. These generate unnecessary heat and can cause noise. Also in this method, like the method of FIG. 13, the discharge cells (Ds) specific variation (variation in parasitic capacitance (Cm)), always for adaptation frequencies can not be obtained, perform adjustment of each time frequency There was a drawback that had to be.

  Further, in each of the conventional examples shown in FIGS. 13 and 16, the inverter is used to adjust the ozone concentration, although there are elements that should be driven near the resonance frequency from the viewpoint of ozone generation efficiency. The drive frequency of (Uj) must be removed from the resonance frequency, and the switching element must be turned on and off. Unnecessary stress is applied to the switching element of the inverter (Uj), and sometimes the switching element is damaged. The change of the cooling condition of the discharge cell (Ds), the change of the temperature of the discharge cell (Ds) due to the gas flow rate to the discharge cell (Ds), the change of the interelectrode distance due to the life deterioration due to the discharge, the capacity of the discharge cell (Ds) Even if the drive frequency of the inverter (Uj) is kept constant due to a decrease in the components, etc., the resonance frequency actually changes, so that the best efficiency cannot always be achieved There is a drawback.

Next, the ozone generation device will be described with reference to FIG. 18, which is a simplified block diagram showing an example of the control system of the ozone generation device. The apparatus is an apparatus for obtaining ozone gas having a desired ozone concentration. In addition to the discharge cell discharge circuit (PS) described above, utility supply valves (V1, V2) such as oxygen, cooling water and nitrogen, and a mass flow controller are provided. Equipment such as (MFC1, MFC2) and ozone detector (Od), which are omitted in the figure, are equipped with necessary parts such as pressure gauges and flow sensors, and are discharged so that they can be controlled automatically A cell discharge circuit control system (hereinafter referred to as “device control system”) (ES) is mounted. The discharge cell discharge circuit (PS) discharges to the discharge cell (Ds), and in this case, oxygen (O ₂ ) and a small amount of nitrogen (N ₂ ) are added and supplied into the discharge cell (Ds). . If oxygen (O ₂ ) is supplied into the discharge cell (Ds), ozone (O ₃ ) is generated.

  The discharge cell discharge circuit (PS) is controlled by a command from the device control system (ES). In particular, the device control system (ES) can operate the discharge start command and the discharge power amount for the discharge cell discharge circuit (PS). For example, if the discharge cell discharge circuit (PS) is a slave and the device control system (ES) is a master, the master outputs a current signal in the range of 4 mA to 20 mA, and the slave is a resistor mounted on the control board on the slave. For example, a signal converted into 1V to 5V is received by a resistor of 250 ohms, and the amount of power input to the discharge cells (Ds) is feedback-controlled. The current signal from the device control system (ES) expresses between the minimum ozone generation value and the maximum ozone generation value defined by the discharge cell discharge circuit (PS).

  The discharge cell discharge circuit (PS) can detect the signal of 4 mA to 20 mA obtained from the device control system (ES) with, for example, 1000 resolution and finely set the amount of power supplied to the discharge cell (Ds). It is. The device control system (ES) monitors the generated ozone amount using an ozone gas detector (Od), and if the ozone generation amount is small, the command value is increased for the discharge cell discharge circuit (PS), If the amount of ozone generated is large, the command value is decreased with respect to the discharge cell discharge circuit (PS).

Next, the relationship between the amount of power input to the discharge cell (DS) and the ozone concentration will be described with reference to FIG. When power is supplied to generate a dielectric barrier discharge (silent discharge) in the discharge cell (Ds) for generating ozone, ozone is generated. When the discharge cell discharge circuit (PS) applies a voltage of several kV to the ozone generation discharge cell (DS) at a driving frequency of several tens of kHz, a barrier discharge is generated, and oxygen (O ₂ ) passes therethrough. In doing so, it is decomposed into radicals and recombined as ozone (O ₃ ). It has been explained that if the command value is increased for the discharge cell discharge circuit (PS), the amount of power supplied to the discharge cell (Ds) also increases. However, excessive power is supplied to the discharge cell (Ds). In this case, the generated ozone (O ₃ ) is destroyed, and the ozone concentration is reduced. This is because the device control system (ES) controls the discharge cell discharge circuit (PS) so as to obtain a desired ozone concentration by simple one-way PID control. This is because the electric power that causes the ozone concentration to decrease after the maximum efficiency point of ozone generation is supplied to the discharge cell (Ds).

  Therefore, the device control system (ES) outputs a current signal in the range of the power range (ΔW ′) and must be set within a range that is lower than the best point of ozone generation and secures a sufficient margin. In addition, it was necessary to reset the maximum output each time so that the discharge cell discharge circuit (PS) also became lower than the maximum original rated output power. Above all, the ozone generation discharge cell (Ds) could not be said to have the maximum ozone generation performance. For example, the discharge power supply is deteriorated due to a change with time, a change in parasitic capacitance of the discharge cell (Ds), a temperature change with continuous use time, for example, cooling by a cooling water supply flow rate to the discharge cell (Ds). Due to changes in conditions and changes in ozone generation conditions due to oxygen flow rate conditions, there was a problem that the ozone concentration changed after a few hours even though the ozone generation concentration was once adjusted and set.

  In addition, when the output from the discharge cell discharge circuit (PS) to the discharge cell (Ds) is defined by the command value from the device control system (ES), even if it is adjusted at the highest point of ozone generation concentration, The maximum ozone generation concentration is not always obtained. This is because the power input point (WO) at which the ozone generation capacity starts to decrease is gradually changing.

  Up to this point, it has been explained that there are two main drawbacks in order to maximize the ozone generation capability of the discharge cell (Ds). The first is a method of applying a voltage to the discharge cell (Ds) by the discharge cell discharge circuit (PS). The discharge cell discharge circuit (PS) is applied by a change in the resonance frequency of the discharge cell (Ds). The voltage changes with time and disturbance, and the best voltage cannot always be applied to the discharge cell (Ds). The other is that when the command value from the device control system (ES) is increased to increase the amount of ozone in order to control the discharge cell discharge circuit (PS), the maximum ozone generation efficiency point passes and the ozone concentration This is because there is a drawback that the electric power that starts to decrease is input to the discharge cell (Ds).

JP 2000-209873 A Japanese Patent Laid-Open No. 11-243690 Japanese Patent Laid-Open No. 11-074057 Japanese Patent Laid-Open No. 06-141554 Japanese Unexamined Patent Publication No. 2000-134944

  The present invention was invented in view of the above problems, and its purpose is to drive a frequency application means in a discharge cell discharge circuit of a discharge cell that generates high-concentration ozone composed of a pair of flat plates and a dielectric. An object of the present invention is to provide a discharge cell discharge circuit capable of adjusting the amount of ozone generation while automatically setting the frequency in the vicinity of the resonance frequency, and being configured at a low cost.

  Another object of the present invention is to provide a discharge cell discharge circuit control system that can adjust the ozone generation amount to the maximum when controlling the discharge cell discharge circuit from the outside and can be configured at a low cost. is there.

The invention described in claim 1 is a discharge cell discharge circuit for discharging a discharge cell (Ds) in which a dielectric is placed between a pair of discharge plates, and a power supply unit (Uw) for supplying DC power An inverter (Uj) that converts DC power supplied from the power supply unit (Uw) into AC power, a transformer (Tr) that boosts AC power converted by the inverter (Uj), and the transformer ( By configuring a closed loop in which the discharge cell (Ds) and the resonant inductor (Lm) are connected to the secondary side of Tr), the resonant inductor (Lm) and the parasitic capacitance (Cm) of the discharge cell (Ds) are configured. And a tuning control for controlling the drive frequency of the inverter (Uj) so as to tune the resonance frequency of the resonance unit and the drive frequency of the inverter (Uj). (Us), and a power control circuit (Uwc) that controls and adjusts the output power of the power supply unit (Uw) so that the output power becomes a specified output power. By the tuning control unit (Us) Discharging is continued by two control systems of control of the drive frequency of the inverter (Uj) and power control by the power control circuit (Uwc), and the tuning control unit (Us) detects a current phase flowing in the resonance unit. A current phase signal (Sfi) obtained by the current phase detection means (Ui) and the voltage phase detection means (Uv) connected to the means (Ui) and the voltage phase detection means (Uv) of the resonating unit; A comparison unit (Uf) that obtains a resonance phase difference signal (Sfr) by comparing the voltage phase signal (Sfv) and a drive frequency of the inverter (Uj) that receives the resonance phase difference signal (Sfr) Resonance frequency And an operation comparison means (Uz) for determining the value of the frequency control signal (Sfg) so as to be tuned to the inverter (Uj) and performing feedback control, and the tuning operation by the tuning control unit (Us) is the frequency control. The frequency control signal (Sfg) in a state where the signal (Sfg) starts from the upper limit frequency and performs a sweep operation toward the lower limit frequency and the resonance phase difference signal (Sfr) level obtains the best resonance state. And then performing a sweep operation in a range narrower than the range corresponding to the lower limit frequency from the upper limit frequency in the vicinity of the frequency control signal (Sfg) corresponding to the resonance frequency of the resonance unit, The discharge cell discharge circuit is characterized in that the resonance part is operated in the vicinity of the resonance frequency .

In the invention according to claim 2 , the tuning control unit (Us) is connected to voltage detecting means (Uv ′) for detecting a voltage applied to the resonant inductor (Lm), and the voltage detecting means (Uv) The value of the frequency control signal (Sfg) is determined so as to tune the drive frequency of the inverter (Uj) to the resonance frequency of the resonance unit in response to the resonance voltage signal (Su) obtained from '). 2. The discharge cell discharge circuit according to claim 1, further comprising an operation comparison means (Uz) for feedback control.

According to the third aspect of the present invention, in the tuning operation by the tuning control unit (Us), the frequency control signal (Sfg) is swept from the upper limit frequency toward the lower limit frequency, and the resonance voltage The frequency control signal (Sfg) in a state where the signal (Su) level has obtained the best resonance state is stored, and thereafter, in the vicinity of the resonance voltage signal (Su) corresponding to the resonance frequency of the resonance unit, 3. The discharge cell discharge circuit according to claim 2 , wherein the resonance unit is always operated near the resonance frequency by performing a sweep operation in a range narrower than a range corresponding to the lower limit frequency from the upper limit frequency. .

The invention according to claim 4 is a control cycle (τx) of the power control circuit (Uwc) for controlling the power supply unit (Uw) for supplying specified power, and the frequency control signal (Sfg). And the control period (τz) of the operation comparison means (Uz) that operates so as to feedback-control the drive frequency of the inverter (Uj) by the relationship of n: m (n ≠ m) 4. The discharge cell discharge circuit according to claim 1 , wherein the discharge cell discharge circuit is controlled with a difference in frequency.

The invention according to claim 5 of the present application operates to feedback control the drive frequency of the power control circuit (Uwc) that operates to feedback control the power supply unit (Uw) and the inverter (Uj). The discharge cell discharge circuit according to any one of claims 1 to 4 , wherein the operation comparison means (Uz) comprises a single microcomputer.

In the invention according to claim 6 of the present application, in the initial stage of starting discharge, the tuning control unit (Us) performs a sweep operation from the upper limit frequency to the lower limit frequency of the inverter (Uj), and performs the sweep operation. The control circuit (Uwc) outputs the output power (WO) of the power supply unit (Uw), the output voltage (VO) of the power supply unit (Uw), or the output current (IO) of the power supply unit (Uw). The discharge cell discharge circuit according to any one of claims 1 to 5 , wherein the voltage is gradually set (over 5 seconds to 120 seconds) and set to a rating.

According to the seventh aspect of the present invention, the tuning control unit (Us) sweeps the drive frequency of the inverter (Uj) from the upper limit frequency to the lower limit frequency before the start of starting discharge, and the inverter detecting the advance value of the resonant frequency near the drive frequency of (Uj), claims after setting and storing this value, perform the firing, further characterized by sustained increase the accuracy of the resonant frequency The discharge cell discharge circuit according to any one of 1 to 5 .

The invention described in claim 8 is a discharge cell discharge circuit control system (ES) for controlling the discharge cell discharge circuit (PS) according to claim 1 from the outside, wherein the discharge cell discharge circuit control system (ES) ) Receives an input signal (Ods) from an ozone detector (Od) that detects the ozone concentration, and outputs an output signal for controlling the output power of the power supply unit (Uw) of the discharge cell discharge circuit (PS) from the outside. The discharge cell discharge circuit control system includes an ozone concentration control circuit (Up) that controls ozone concentration by outputting (PSd) to the power control circuit (Uwc).

According to the ninth aspect of the present invention, the ozone concentration control circuit (Up) increases the output signal (Psd) when the ozone concentration obtained by the input signal (Ods) does not reach a desired ozone concentration. When the ozone concentration obtained by the input signal (Ods) is higher than the desired ozone concentration, feedback control is performed so as to decrease the output signal (PSd), and the output signal (PSd) is further increased. However, when the input signal (Osd) starts to decrease, the sign of the operation change amount is negative, and conversely, the input signal (Osd) is decreased although the output signal (PSd) is decreased. discharge cells discharge circuit control system near of claim 8 but when turned to decrease, characterized in that it comprises a control system that performs feedback control for the sign of the operation amount of change is positive .

According to the first aspect of the present invention, in the discharge cell discharge circuit of the discharge cell that generates high-concentration ozone, the ozone concentration is controlled by controlling the power supplied to the inverter (Uj), and at the same time, the inverter (Uj ) Is always controlled automatically so as to be in the vicinity of the resonance frequency of the resonance part, so that even when the discharge cell (Ds) is in the main discharge and the ozone concentration is adjusted, It is possible to provide the best ozone generation efficiency and to provide an inexpensive discharge cell discharge circuit. Further, the tuning control unit (Us) includes the comparison unit (Uf) and the operation comparison unit (Uz), so that the drive frequency of the inverter (Uj) can be reliably controlled. In the tuning operation by the tuning control unit (Us), the frequency control signal (Sfg) is swept from the upper limit frequency to the lower limit frequency, and the resonance phase difference signal (Sfr) level is the best resonance state. The frequency control signal (Sfg) in the state obtained is stored, and after that, the frequency control signal (Sfg) in the vicinity of the resonance frequency of the resonance unit is swept in a range narrower than the range corresponding to the lower limit frequency from the upper limit frequency By performing the operation, it is possible to always operate the resonance unit in the vicinity of the resonance frequency.

According to the second aspect of the invention, the control of the drive frequency of the inverter (Uj) by the tuning control unit (Us) can be reliably performed with a simple configuration.

According to the third aspect of the present invention, the resonance unit can always be operated in the vicinity of the resonance frequency with certainty.

According to the fourth aspect of the invention, the discharge cell discharge circuit can be controlled without loss of stability.

According to the invention described in claim 5 , an inexpensive and small control system can be provided.

According to the invention described in claim 6 , it is possible to contribute to the protection and life of the discharge cell (Ds), and to safely prevent the discharge cell while contributing to prevention of destruction of the discharge cell (Ds) and maintaining high ozone generation efficiency. (Ds) can be activated.

According to the invention described in claim 7 , since the resonance frequency is detected before the main discharge is started, it is possible to quickly increase the ozone generation efficiency after the discharge start command is turned on, and the resonance frequency is unnecessarily long. Since it is not necessary to drive the inverter (Uj) out of the range, it is possible to contribute to the reduction of the breakdown risk of the discharge circuit.

According to the eighth aspect of the invention, the ozone concentration can be controlled by controlling the discharge cell discharge circuit (PS) from the outside by the ozone concentration control circuit (Up) of the discharge cell discharge circuit control system (ES). it can.

According to the ninth aspect of the present invention, the ozone concentration control circuit (Up) can supply the optimum power to the discharge cell (Ds), and the maximum capacity of the discharge cell (Ds) can be exhibited. Become.

It is a block diagram which simplifies and shows the discharge cell discharge circuit concerning 1st embodiment. It is a block diagram which simplifies and shows an electric power supply part (Uw) and an electric power control circuit (Uwc). It is a characteristic view which simplifies and shows the relationship of the output voltage regarding the constant power control in an electric power supply part (Uw), an output current, and output power. It is a block diagram which simplifies and shows an example of the circuit of a tuning control part (Us). It is a block diagram which simplifies and shows the other example of the circuit of a tuning control part (Us). It is a block diagram which simplifies and shows the operation comparison means (Uz) of the tuning control part (Us), the period drive circuit (Ug), and the inverter (Uj). FIG. 5 is a time chart illustrating an automatic tuning operation when the circuit diagram of FIG. 4 is used. FIG. 5 is an operation flowchart illustrating an automatic tuning operation when the circuit diagram of FIG. 4 is used. It is a figure which shows the frequency characteristic of a resonance part, and is a figure for demonstrating the reason for sweeping a switching frequency from an upper limit frequency (Fmax) toward a lower limit frequency (Fmin). It is a figure which shows an experimental waveform. It is a flowchart figure which shows the control action of a discharge cell discharge circuit. It is a timing diagram which shows the control action of a discharge cell discharge circuit. It is a block diagram which shows the ozone generation circuit of the conventional discharge cell discharge circuit. It is operation | movement explanatory drawing of the switching element (Q10, Q11) of the ozone generation circuit shown in FIG. It is a frequency characteristic figure which simplifies and shows the conventional discharge cell discharge circuit. It is a block diagram which shows the ozone generation circuit of the other conventional discharge cell discharge circuit. It is operation | movement explanatory drawing of the switching element (Q10, Q11) in the ozone generation circuit shown in FIG. It is a block diagram which simplifies and shows an example of the control system of an ozone production | generation apparatus. It is a characteristic view which simplifies and shows the relationship between the electric power input amount to a discharge cell, and ozone concentration. It is a block diagram which simplifies and shows the discharge cell discharge circuit (PS) concerning 2nd embodiment. It is a block diagram which simplifies and shows an example of the circuit of a tuning control part (Us). It is a block diagram which simplifies and shows an example of the interaction of the signal of an apparatus control system (ES), a discharge cell discharge circuit (PS), and an ozone detector (Od). It is a time chart figure explaining the automatic control method by the ozone control circuit (Up) at the time of using the circuit diagram of FIG. It is a characteristic view which simplifies and shows the relationship between the electric power input amount to a discharge cell, and ozone concentration. FIG. 24 is an operation flow diagram illustrating processing in which the increase / decrease direction of the output signal (PSd) described in FIG. 23 is reversed. It is a control block diagram using a discharge cell discharge circuit (PS), an apparatus control system (ES), and an ozone detector (Od).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment of Discharge Cell Discharge Circuit]
FIG. 1 is a simplified block diagram showing a discharge cell discharge circuit according to a first embodiment of the present invention. In the discharge cell discharge circuit shown in the figure, a commercial AC power source, for example, a three-phase power source, which is a power supply source to the discharge cell (Ds), is connected to a rectifier (Ur) from a node (R, S, T). The The rectifier unit (Ur) includes a plurality of diodes, performs full-wave rectification, and becomes a DC output in a power supply unit (Uw) including a power control circuit (Uwc) for supplying specified power. And stored in the smoothing capacitors (C1, C2). The inverter (Uj) converts the DC output into alternating current, and this alternating current power is converted into a high voltage via the step-up transformer (Tr), and an inductor (on the secondary winding side of the step-up transformer (Tr)) ( Lm) is applied to the discharge cell (Ds) with a dielectric interposed.

  The tuning control unit (Us) takes in the AC voltage phase of the discharge cell (Ds) and the AC current phase to the discharge cell (Ds), generates a phase difference signal, and minimizes the phase difference. A drive signal is output as a pulse signal to a drive circuit (Ug) for driving the inverter (Uj) to perform feedback control.

  The operation of the switching elements (Q1, Q2) disposed on the inverter (Uj) will be described. The DUTY ratio of each of the switching elements (Q1, Q2) is approximately 50%, and each of the switching elements (Q1, Q2) is An appropriate extremely short period during which the switching elements (Q1, Q2) are both turned off is set during the on-time, and this is alternately operated. The drive frequency of the inverter (Uj) is a resonance frequency described later. Frequency modulation with a feedback function is performed so as to meet the requirements.

  Here, when adjusting the ozone concentration, the power control circuit (Uwc) controlling the power supply unit (Uw) controls the ozone concentration by controlling the power supplied to the inverter (Uj). .

  On the other hand, the drive frequency of the inverter (Uj) is always close to the resonance frequency of the resonance part on the secondary side of the transformer (Tr) composed of the parasitic capacitance (Cm) component of the discharge cell (Ds) and the inductor (Lm). Control to be In the discharge cell (Ds) for generating ozone, when the high voltage is applied at the resonance frequency, the power supply unit (Uw) is the least necessary supply power and the power discharge cell (Ds) This is because ozone can be generated with high efficiency by applying a high voltage. Therefore, the resonance frequency of the resonance part formed by the parasitic capacitance (Cm) component of the discharge cell (Ds) and the inductor (Lm) connected in series with the discharge cell (Ds) is used, and the frequency It is preferable that the high voltage is applied by driving.

  As described above, the ozone concentration is controlled by controlling the power supplied to the inverter (Uj), and at the same time, the drive frequency of the inverter (Uj) is controlled to be close to the resonance frequency in the discharge cell (Ds). Even when the discharge cell (Ds) is in the main discharge and the ozone concentration is adjusted, the best ozone generation efficiency can be enjoyed.

  In the present embodiment, the inverter (Uj) is a half-bridge type using two switching elements (Q1, Q2). However, two additional switching elements are added, and the full-bridge type shown in FIG. It is also possible to adopt a configuration in which the switching elements at the counter electrode are alternately operated as a pair with a duty ratio of about 50% with the drive frequency as the resonance frequency.

  In this embodiment, the rectification unit (Ur) is described using a diode rectification circuit. However, the PFC technology, which is a power factor correction circuit, a step-up buck converter, and a voltage doubler rectification circuit are used. A DC voltage of 400 V may be generated, the input power supply is not limited to a three-phase power supply, and the circuit system in this part is not the essence of the present invention.

  Next, FIG. 2 is a block diagram schematically showing the power supply unit (Uw) and the power control circuit (Uwc). As shown in the figure, these circuits are circuits that are used to convert the input voltage (VI) of the power supply unit (Uw) into a constant output voltage (VO), and the main switching element (Q20) and A step-down DC-DC converter including an inductor (L20), a smoothing capacitor (C21), and a flywheel diode (D20) is used. The control of the main switching element (Q20) is generally PWM control in which on / off control is repeated at a specified period. Although detailed description of PWM control is omitted, ICs dedicated to PWM controllers such as μPC494 and TL494 are widely known as one means for realizing this.

  The output voltage (VO) is generally determined by the voltage of the discharge cell (Ds) and the winding ratio of the transformer (Tr) shown in FIG. 1, but the state of the discharge cell (Ds) at that time, that is, the discharge As a result, the output voltage (VO) is affected by the internal pressure and temperature of the cell (Ds). That is, since the output voltage (VO) varies depending on the load, the output voltage (VO) is measured and the output current (IO) is controlled to control the output power to be constant. In order to reduce unnecessary loss generated in the power supply unit (Uw) itself, a method using a partial resonance type soft switching technique may be used, or a critical control method in a step-down buck converter may be used. Alternatively, an insulated flyback or forward converter may be used.

  In order to perform desired power control, the power control circuit (Uwc) needs to capture an output voltage signal (Sv) and an output current signal (Si). However, since the output current signal (Si) has a small resistance value of the current detection resistor (R22), the voltage signal generated at both ends thereof is a very weak signal. For this reason, it is necessary to first amplify the signal by the amplifier (A20) and then take it into the power control circuit (Uwc). And the electric power setting signal (Sw) for setting ozone concentration from the outside is taken in into the said electric power control circuit (Uwc). The current output power can be obtained from the acquired output voltage signal (Sv) and the output current signal (Si). Here, a microcomputer (MPU) is adopted as the power control circuit (Uwc). As a result, the power control circuit (Uwc) fetches a power setting signal (Sw) for setting a desired power value (set power value) from the device control system (ES) described below, so that the actual output power Can be compared. For example, if the calculated actual output power value is smaller than a desired set power value, the power control is performed so as to increase the ON width of the PWM signal of the main switching element (Q20) in order to increase the output current (IO). The circuit (Uwc) transmits a PWM signal to the drive circuit (GQ20) of the main switching element (Q20). On the other hand, when the power value is larger than the desired set power value, which is the opposite case, the ON width of the PWM signal is reduced to reduce the output current (IO). Since feedback control is performed in this manner, for example, the power fluctuation at 100 Hz, which is the 50 Hz rectification ripple described in the background art, is greatly reduced, and the fluctuation of the ozone concentration in the discharge cell (Ds) can be almost ignored and is stable. Ozone generation is possible. This also has the advantage of using a smaller smoothing capacitor. By performing feedback control in this way, it is possible to input desired power to the discharge cell (Ds).

  FIG. 3 is a characteristic diagram showing a simplified relationship between output voltage, output current, and output power for constant power control in the power supply unit (Uw). These relationships will be described below. From the viewpoint of damage due to the absolute maximum rated current, which is a characteristic of the main switching element (Q20), and from the viewpoint of heat generation due to current loss in the inductor (L20), the output current (IO) needs to be a finite value. The output current (IO) has a maximum limit current value (Imax). On the other hand, a maximum limit voltage value that can stably output the output voltage (VO) is also set. This may depend on the maximum ON width according to the design condition for controlling the duty ratio of the main switching element (Q20). However, if the output voltage (VO) is set to be unnecessarily high, the inverter (Uj) The above switching elements (Q1, Q2) need to be selected as switching elements with a high withstand voltage. For example, when an FET is used as the switching element (Q1, Q2) in FIG. Therefore, as a result, unnecessarily heat is generated. In addition, from the aspect of selecting an FET, the lower the withstand voltage, there is an advantage that the options are expanded.

Note that the parameters as setting examples in FIG. 3 are as follows.
V1: 100V
V2: 200V
Imax: 4A
W0: 400W
Mainly taking into account variations in the discharge cells (Ds) and discharge conditions, the normally used output power state should be set near the center voltage within the constant power range (WC). When changing the ozone concentration, the line (W0) in the constant power region is shifted to, for example, the power line (W1) in the power modulation variable region (ΔW), and the discharge cell (Ds) is changed. It works to limit the power supply. Thereby, the power control circuit (Uwc) independently manages power without depending on the inverter (Uj) even in a portion where the power consumption is in an unmanaged state in the past. Can be enjoyed. That is, even if the power control circuit (Uwc) performs ozone concentration control, it can be said that the inverter (Uj) can always continue to apply a high voltage Sin wave due to a resonance action optimal for ozone generation.

  Next, FIG. 4 is a block diagram showing a simplified example of the circuit of the tuning control unit (Us). In the tuning control unit (Us) shown in the figure, a current waveform is obtained by using a current transformer as current phase detection means (Ui) flowing in the resonance unit composed of the discharge cell (Ds) and the inductor (Lm). And a voltage waveform is detected using a tertiary winding of a step-up transformer as voltage phase detection means (Uv) flowing in the resonance part. The details will be described below.

  First, for example, two power sources of 20V and 5V are prepared as circuit power sources. One side of two lines from the winding part of the voltage phase detection means (Uv) and current phase detection means (Ui) for detecting the voltage signal and the current signal is connected to the 5V line. The signal of the voltage waveform and the current waveform is detected as a so-called Sin wave centered on 5V, the power source of the comparator (A40, A41) is connected to the 20V line, the voltage waveform or the current waveform is connected to the comparator input terminal, The other input terminal is connected to the 5V line. Therefore, the output from the comparators (A40, A41) is a square wave with a DUTY ratio of 50%.

  Since both the current phase signal (Sfi) and the voltage phase signal (Sfv) converted to the square wave are phase signals of 0-5V level, the phase difference can be measured by comparing the both, so that the comparison unit (Uf ) Can be used to measure the amount of phase difference using an exclusive OR (Exclusive-OR).

  If there is a phase difference, for example, the voltage phase signal (Sfv) from the comparator (A40) is low level (0), and the current phase signal (Sfi) from the comparator (A41) is high level (1). ) And the output of the exclusive OR becomes High level (1). Conversely, when there is no phase difference, for example, the voltage phase signal (Sfv) from the comparator (A40) is at a high level (1), and the current phase signal (Sfi) from the comparator (A41) is at a high level ( 1), and the output of the exclusive OR becomes the low level (0). Therefore, the larger the phase difference is, the longer the time for the exclusive OR output to become High level (1) in time series is smoothed by the CR circuit (R45, C40) and stored in the capacitor (C40). The generated voltage (Vsd) can be expressed as an analog quantity to express the current phase difference signal (Sfr).

  Thereby, the operation comparison means (Uz) can detect the magnitude of the phase difference signal. If the resonance unit is in the resonance state, the voltage phase signal (Sfv) and the current phase signal (Sfi) are Since the phase is the same, the voltage (Vsd) of the phase difference signal (Sfr) approaches to be substantially zero. The generated phase difference signal (Sfr) is input to the operation comparison means (Uz). The operation comparison means (Uz) uses a microprocessor on the premise that the analog quantity is digitized. A digital converter may be used once. Alternatively, an analog signal may be directly used as a control circuit without using a microprocessor.

  FIG. 5 is a simplified block diagram showing another example of the circuit of the tuning control unit (Us). The circuit shown in FIG. 4 uses a method of detecting the phase of the voltage waveform and the current waveform, but the circuit shown in FIG. 5 has a simplified form. That is, the tuning control unit (Us) detects a voltage applied to the inductor (Lm) of the resonance unit, and thus detects a voltage between secondary windings of the inductor (Lm). ). If the resonance part is close to the resonance state, the signal obtained by the voltage detection means (Uv ′) becomes a substantially sine wave signal, so that the voltage generated between the secondary windings of the inductor (Lm) has the largest amplitude. Large waveform. The voltage generated in the secondary winding is rectified by the diodes (D50, D51, D52, D53), smoothed by the CR circuit (R50, C50), and stored in the capacitor (C50). The voltage (Vse) stored in the capacitor (C50) can be expressed as an analog amount to represent the current resonance voltage signal (Su), and is input to the operation comparison means (Uz). In this example, a simple full-wave rectification method using diodes (D50, D51, D52, D53) is used, but a peak hold circuit constituted by an operational amplifier or the like may be used.

  FIG. 6 is a block diagram showing the operation comparison means (Uz), the period drive circuit (Ug) and the inverter (Uj) of the tuning control unit (Us) in a simplified manner. In the form of the tuning control unit (Us) described with reference to FIG. 4, the condition that the drive frequency of the inverter (Uj) is tuned to the resonance frequency of the resonance unit upon receiving the phase difference signal (Sfr), that is, the A case where the phase difference signal (Sfr) is the smallest is detected as a resonance condition, and the calculation comparison means (Uz) determines the value of the frequency control signal (Sfg). Then, the frequency control signal (Sfg) is transmitted to the gate circuit (Ug) that drives the switching elements (Q1, Q2) on the inverter (Uj) to operate the switching elements (Q1, Q2). In this example, a microcomputer (MPU) is used as the operation comparison means (Uz), but when a high frequency signal cannot be output directly from the microcomputer (MPU), DA output is performed from the microcomputer (MPU). The frequency control signal (Sfg) may be generated via Vco, or a technique such as a PLL synthesizer may be introduced and embodied.

  In the case of the tuning control unit (Us) described with reference to FIG. 5, the condition for receiving the resonance voltage signal (Su) and tuning the drive frequency of the inverter (Uj) to the resonance frequency of the resonance unit, that is, A case where the voltage (Vse) of the resonance voltage signal (Su) is the largest is detected as a resonance condition, and the calculation comparison means (Uz) determines the value of the frequency control signal (Sfg). Then, the frequency control signal (Sfg) is transmitted to the gate circuit (Ug) that drives the switching elements (Q1, Q2) on the inverter (Uj) to operate the switching elements (Q1, Q2).

  In the case of the discharge cell discharge circuit for generating high-concentration ozone according to this embodiment, the frequency control signal (Sfg) is generally set in the range of 10 kHz to 40 kHz.

  Next, the automatic tuning operation that always operates in the vicinity of the resonance frequency will be described using the circuit diagram of FIG. 4 with reference to FIG. 7 that is a time chart and FIG. 8 that is an operation flowchart.

  First, the time chart of FIG. 7 will be described. The frequency control signal (Sfg) sweeps the switching frequency from the upper limit frequency (Fmax) toward the lower limit frequency (Fmin). Since the frequency control signal (Sfg) is the upper limit frequency (Fmax) at the initial time, the voltage (Vsd) of the phase difference signal (Sfr) has a large value because it is far from the resonance frequency as a target. ing.

  If the sweep operation is continued, the resonance frequency is temporarily passed. However, the voltage of the phase difference signal (Sfr) is approached to the resonance frequency in the period up to the time point (t1). The operation comparison means (Uz) detects that (Vsd) is decreasing. When the frequency control signal (Sfg) is swept toward the lower limit frequency (Fmin), the frequency control signal (Sfg) deviates from the resonance frequency, and the voltage (Vsd) increases. The operation comparison means (Uz) detects that the voltage (Vsd) has increased at the time (t2) and recognizes that it has passed the resonance frequency. That is, since the frequency control signal (Sfg) has a frequency slightly lower than the optimum point, the control is started to operate in the direction of increasing the frequency control signal (Sfg). Then, until the time point (t3), since the frequency approaches the resonance frequency, the operation comparison means (Uz) detects that the voltage (Vsd) of the phase difference signal (Sfr) decreases, and the frequency control The signal (Sfg) continues to increase. At the time (t4), it turns again and decreases. By repeating this series of operations, the phase difference signal voltage (Vsd) is always controlled to decrease, and is stable in the frequency band (Δf) specified in the range, that is, can always continue toward the resonance frequency.

  Next, a processing method in the operation comparison means (Uz) for performing the automatic tuning operation described with reference to FIG. 7 will be described with reference to an operation flowchart of FIG. First, when the control start condition (CND1) is turned on in the block (B1), for example, it is determined whether or not the power supply is in operation, and the frequency control signal (Sfg) is controlled. The description will be made assuming that the condition (CND1) is on.

  The MPU (microcomputer) of the operation comparison means (Uz) obtains the voltage (Vsd) data of the phase difference signal (Sfr) in the block (B2), performs so-called AD conversion, and obtains the latest value (NOW_AD). get. If there is no phase difference between the voltage phase signal (Sfv) and the current phase signal (Sfi), the voltage (Vsd) should be very small. Therefore, the voltage (Vsd) AD-converted in the block (B3) is If it is smaller than the predetermined set value (k), it is not necessary to update the output amount of the frequency control signal (Sfg), so the current frequency of the bridge is held. However, when the voltage (Vsd) is larger than the predetermined set value (k), the voltage (Vsd) AD-converted in the block (B4) is compared with the predetermined set value (m). That is, when the absolute value of the phase difference is larger than the set value (m), the block (B7) is processed thereafter to increase the amount of frequency modulation operation of the frequency control signal (Sfg). If the voltage (Vsd) is greater than the set value (k) and less than the set value (m), the block (B5) is used to reduce the frequency modulation operation amount of the frequency control signal (Sfg). It is processed. This series of processes is repeated to always keep the vicinity of the resonance frequency.

  Next, the case where the voltage (Vsd) is between the set value (k) and the set value (m) will be described. If the operation routine of FIG. 8 is executed, for example, every about 10 ms, the value of the AD conversion of the voltage (Vsd) executed immediately before, that is, the main value 10 ms before is stored (block). B13) is arranged. Therefore, the block (B5) can compare the previous value (OLD_AD) with the latest value (NOW_AD). If OLD_AD <NOW_AD, the voltage (Vsd) increases compared to the previous value. This means that it is away from the resonance frequency. In this case, in the block (B9), if the frequency control signal (Sfg) is in the current increasing direction, the frequency control signal (Sfg) is in the decreasing direction, and conversely, the frequency control signal (Sfg) is in the current decreasing direction. For example, in order to increase the frequency control signal (Sfg), the increase / decrease direction determination flag (F_ALLOW) for performing the reverse and inversion operation is inverted (Exclusive-OR). If the example described with reference to FIG. 7 is used, when the voltage (Vsd) is detected to increase at the time (t1) and the resonance frequency is recognized, the frequency control signal is detected. This is synonymous with the operation in which the increase / decrease in (Sfg) is reversed at the time (t2).

  Then, when the frequency control signal (Sfg) is in the decreasing direction by the increase / decrease direction determination flag (F_ALLOW), −1 is increased with respect to the current operation amount in the block (B12), and in the case of the current increasing direction, the block is In (B11), +1 is increased with respect to the current operation amount.

  Conversely, when OLD_AD> NOW_AD in block (B5), it means that the voltage (Vsd) is decreasing compared to the previous time, so the frequency control signal (Sfg) is the resonance. Since it can be determined that the frequency is approaching, the increase / decrease direction is maintained according to the previously set increase / decrease direction determination flag (F_ALLOW), that is, without performing the inversion process of the increase / decrease direction determination flag (F_ALLOW).

  If the voltage (Vsd) value is between the set value (k) and the set value (m), the block (B11) is used to reduce the operation amount of the frequency modulation of the frequency control signal (Sfg) described here. , B12), increase / decrease is performed with a small change amount of +1 and −1.

  If it is determined in block (B4) that the voltage (Vsd) value is greater than the set value (m), that is, the phase difference is large, the process proceeds to block (B7). The operation of the block (B7, B8, B10) is the same as that of the block (B5, B6, B9), but the block (B13, B14) is used to increase the amount of frequency modulation operation of the frequency control signal (Sfg). Then, for example, the frequency control signal (Sfg) amount is increased or decreased by a large change amount of +10 and −10.

  Here, the amount of increase / decrease in the frequency control signal (Sfg) is described as +10, −10, +1, −1, but this is a set value for convenience of explanation, and is not limited to this. The value will be adjusted throughout the experiment.

  In the case of a discharge cell for generating high-concentration ozone which is one of the embodiments of the present invention, the frequency control signal (Sfg) is generally controlled and set with a resolution of 4000 in the range of 10 kHz to 40 kHz. The phase difference signal voltage (Vsd) is usually controlled with 1000 resolution, but this is not a limitation.

  By always performing feedback in this way, it is possible to always operate near the resonance frequency. For example, when the pressure or temperature of the discharge cell (Ds) changes, the discharge voltage of the discharge cell (Ds) changes. Even if the resonance frequency changes due to the change in the capacitance value of the parasitic capacitance (Cm), the drive frequency of the inverter (Uj) also changes in the vicinity of the change in the resonance frequency. The ozone generation efficiency can be always satisfied.

  As described above with reference to FIGS. 7 and 8, the tuning operation by the tuning control unit (Us) performs the sweep operation of the frequency control signal (Sfg) from the upper limit frequency toward the lower limit frequency. The frequency control signal (Sfg) in a state in which the resonance state having the best resonance phase difference signal (Sfr) level is obtained is stored, and then the vicinity of the frequency control signal (Sfg) corresponding to the resonance frequency of the resonance unit By performing the sweep operation in a range narrower than the range corresponding to the lower limit frequency from the upper limit frequency, the resonance unit is always operated near the resonance frequency. When FIG. 5 is used, the tuning operation by the tuning control unit (Us) performs the sweep operation of the frequency control signal (Sfg) from the upper limit frequency to the lower limit frequency, and the resonance voltage signal. (Su) Stores the frequency control signal (Sfg) in a state where the resonance state having the best level is obtained, and then the upper limit in the vicinity of the resonance voltage signal (Su) corresponding to the resonance frequency of the resonance unit. By performing the sweep operation in a range narrower than the range corresponding to the lower limit frequency from the frequency, the resonance unit is always operated in the vicinity of the resonance frequency.

  FIG. 9 is a diagram illustrating the frequency characteristics of the resonating unit, for explaining the reason for sweeping the switching frequency from the upper limit frequency (Fmax) toward the lower limit frequency (Fmin). That is, as shown in FIG. 9, the portion with the highest Q is in the resonance state, and the frequency of the frequency control signal (Sfg) is set so as to always keep the vicinity of the resonance frequency (f0) at this time, that is, to enter Δf. Be controlled.

  The reason for not sweeping from the upper limit is that the resonance mode by odd-order resonance is raised. When this is swept from the lower limit frequency (Fmin) toward the upper limit frequency (Fmax), for example, there is a possibility that it is recognized as a resonance state when the third-order resonance is generated. This is because it cannot be said. Therefore, it is optimal to start from the upper limit frequency (Fmax). Since these control sequences are complicated, it is preferable to control them using a microcomputer.

Moreover, it demonstrates using FIG. 10 which is an experimental waveform at the time of implementing in FIG. 1 which is the circuit form of this invention by making a discharge cell (Ds) into a load. In the figure, (a) is a voltage waveform applied to both ends of the discharge cell (Ds), (b) is a current waveform to the discharge cell (Ds), (c) is a voltage waveform on the primary side of the transformer, (d ) Is a current waveform flowing on the primary side of the transformer, and the following results were obtained from the waveform.
Inverter frequency: 24.9 kHz
Discharge cell output current: 0.9 Arms
Discharge cell output voltage: 4.8 kVp-p
Other parameters in this experimental example are as follows.
Power supply: Approximately 200W
Lm: 11.5mH
Discharge cell: 2 Cells manufactured by Ebara Corporation
Tr winding ratio: Pri: Sec / 1: 8
Oxygen supply amount to discharge cell 4L / M
Nitrogen addition amount to discharge cell 32ccm
Ozone production amount: 78ppm

  Looking at the voltage waveform (a) applied to both ends of the discharge cell (Ds) and the current waveform (b) to the discharge cell (Ds), when the voltage value applied to both ends of the discharge cell (Ds) is the maximum, Since the current value to the discharge cell (Ds) is 0, it can be understood that the resonance condition is obtained. Further, in order to maintain this resonance state, the switching element (Q1, Q2) performs an invert operation when the current value to the discharge cell (Ds) becomes 0 to assist this resonance. This can be understood from the voltage waveform (c) on the primary side of the transformer. At this time (ti), the current flowing through the inverter (Uj) from the voltage waveform on the primary side of the transformer is substantially zero, achieving zero voltage (current) switching, and stressing the switching elements (Q1, Q2). A stable operating waveform is obtained without giving Even if there is a leakage inductance present in the step-up transformer (Tr), the resonance system absorbs the L value, which is improved from the viewpoint of noise.

  As described with reference to FIG. 13, if the drive frequency of the inverter (Uj) is forcibly matched with the resonance frequency (f0), an excessive voltage is applied to the discharge cell (Ds) because there is no means for limiting the power. Unfortunately, the drive frequency of the inverter (Uj) is removed from the resonance frequency (f0). Therefore, the phase of the voltage waveform on the primary side of the transformer is different from the phase of the current waveform flowing on the primary side of the transformer, and it cannot be said that the power factor is the best.

Here, W = V × I × cos φ
In other words, in the present invention in which the drive frequency of the inverter (Uj) is always in a resonance state, the phase of the current and the voltage waveform on the primary side of the transformer coincide with each other, so cos φ = 1. If they are different, φ increases, so cos φ is 1 or less. As a result, in the case of outputting the same power, V and I must be increased compared to the condition where the phases are in agreement, so that a peak value larger than the original current value is required. For example, for a transformer, not only the copper loss increases but also the iron loss increases, so that the diameter of the winding of the transformer increases and the size of the transformer itself becomes larger. In view of this problem, since the present invention supplies the optimum voltage and current, the transformer can contribute to reduction in size and weight and cost.

  As described above, according to the present embodiment, the minimum necessary amount is obtained by the operation of the tuning control unit (Us) under the stable condition using the power supply unit (Uw), which is the main object of the present invention. Since the applied voltage of the discharge cell (Ds) can obtain the maximum effect with the input power, ozone can be generated at the best efficiency at all times, and the switching element on the inverter (Uj) is unnecessarily out of resonance. Therefore, the stress of the switching elements (Q1, Q2) of the inverter (Uj) can be reduced, and radiation noise and conduction noise can be suppressed as a secondary effect. In other words, it is possible to generate the same amount of ozone with less power consumption than before, reducing the running cost of the ozone generator, and also contributing to energy saving and global environmental problems. A discharge circuit in the form of can be provided.

  Now, a microcomputer (MPU) on the power control circuit (Uwc) for controlling the power supply unit (Uw) shown in FIG. 2, and the frequency control signal (Sfg) shown in FIGS. A case will be described in which the microcomputer (MPU) on the operation comparison means (Uz) for controlling the computer is constituted by one microcomputer (MPU). For example, this microcomputer can use a microcomputer which is an 8-bit operator equipped with two 16-bit timers. Since the first timer is the power control circuit (Uwc), the power supply unit (Uw) shown in FIG. 2 is used to perform constant power control as described in FIG. 2 by using it as a PWM signal output from a microcomputer. The output voltage (VO) is measured to determine the target current, and the signal is output to the gate circuit (GQ20) to perform power control. The other timer is used as a square wave output, for example, assigned to the frequency control signal (Sfg) output of the arithmetic comparison means (Uz) described in FIG. Can be generated, and the above-described resonance frequency control of the resonance unit can be performed. The reason for using the 16-bit class timer is that the above two controls can be controlled with high accuracy.

  If all the functions of the power control circuit (Uwc) and the operation comparison means (Uz) are configured with only hardware circuits without any software, the amount of circuits becomes enormous and unrealistic from the viewpoint of cost. For this reason, it is preferable that all or part of the functions of the power control circuit (Uwc) and the operation comparison means (Uz) are implemented by a microcomputer. Of course, the microcomputer (MPU) on the power control circuit (Uwc) and the microcomputer (MPU) on the operation comparison means (Uz) may be separate microcomputers, but they are integrated as one microcomputer. By doing so, an inexpensive and small control system can be finally provided. Further, when a digital signal processor (DSP) is used, it is possible to further simplify the peripheral circuits in the power control circuit (Uwc) and the power supply unit (Uw), and to save space and cost. It is.

  Next, referring to FIG. 11, a software operation for controlling the discharge cell discharge circuit, in which the control of the power control circuit (Uwc) and the control of the calculation comparison means (Uz) are integrated as one microcomputer, is conceptually shown. A mode for carrying out the present invention will be described with reference to FIG.

  When the power supply circuit is fed back by digital processing, the power control and the frequency control signal (Sfg) control are performed regularly so that the control feedback time does not vary. Therefore, the block (B20) is limited so that the timer (TIMER) advances to the block (B21) and thereafter every time the desired time (Lt) elapses. For example, the loop (LOOP = Lt) of this software is experimentally determined. To 2 ms. As described above, the block (B21) performs AD conversion processing that requires control, processing for presence / absence of digital input, and the like.

  Subsequent double loop control will be described. As described above, the control of the power control circuit (Uwc) and the control function on the arithmetic comparison means (Uz) are performed, but the timings of the respective executions do not necessarily have to coincide.

  A counter 1 (COUNTER1) is arranged in the block (B22) in order to measure the timing of controlling the power control circuit (Uwc), and a predetermined time, for example, 2 ms is set, that is, the set value (N) is N = 1. It can be set, and feedback control of the output power of the discharge power supply is performed in block (B23) every 2 ms. Thus, the power control circuit (Uwc) stabilizes the desired output power value while increasing or decreasing the current limit level expressed by 16 bits by 1 LSB.

  Similarly, a counter 2 (COUNTER2) is arranged in the block (B24) and a predetermined time, for example, 10 ms is set in order to measure the timing for executing the control of the operation comparison means (Uz). That is, the set value (M) is M = The frequency control signal (Sfg) control is performed in the block (B25) every 10 ms, and as a result, the oscillation frequency of the inverter (Uj) is modulated. For example, the details of the block (B25) mean a series of operations processed in FIG.

  The reason why this double loop control is necessary will be described below. That is, the power command value is not always constant in the usage state of this apparatus, and the amount of ozone to be generated may be modulated. Therefore, it is necessary to control the power command and the frequency command of the inverter (Uj), respectively. However, when the power command value is changed, the resonance frequency also changes, so that it is necessary to provide a time difference in each control cycle (τx, τz). Since the resonance frequency of the discharge cell (Ds) changes depending on the input electric power, the power control cycle is faster than the control cycle of the inverter (Uj). Conditions that are preferred, i.e., M> N are optimal. However, if the condition of M> N is maximized, the frequency modulation will be delayed and the resonance frequency will be deviated, so that the necessary power will not be input, and the power control circuit (Uwc) Control to increase the output voltage to turn on the power, and then the resonance frequency matches with the frequency modulation, power is turned on with the output voltage being raised too much, and excessive power is turned on repeatedly. Such a situation is a concern. Therefore, specific conditions were obtained with the values of N: M = 1: 5 from the experimentally derived values so that control can be performed without loss of stability such as abnormal oscillation.

  That is, in this embodiment, the control period (τx) of the power control circuit (Uwc) for controlling the power supply unit (Uw) for supplying specified power and the value of the frequency control signal (Sfg) are determined. Then, the control period (τz) of the arithmetic comparison means (Uz) that operates so as to feedback control the drive frequency of the inverter (Uj) depends on the relationship of n: m (n ≠ m, especially n <m). It is controlled with a temporal frequency difference.

Next, with reference to FIG. 12 which is a time chart of the output current (IO), which is an output unit of the power supply unit (Uw), and the output power (WO), a sequence of power supply to the discharge cells (Ds) will be described. explain. With respect to the initial discharge state of the discharge cell (Ds), the discharge cell (Ds) suddenly rises in temperature, excessive overpower is supplied to the discharge cell (Ds), or the discharge cell (Ds). It is preferable that the current or voltage waveform applied to is controlled to avoid a protruding state exceeding a specified value. Here, control is performed as follows according to FIG.
-Discharge starts at time (tA).
-Gradually control the maximum current upper limit value from 0 to the maximum limit current value (Imax).
The time point (tB) until the maximum current upper limit value reaches the maximum limit current value (Imax) is defined.
-After the time (tC), the normal operation state is entered in the constant power region.

  Here, the time (tB) is set to approximately 60 seconds from the start of discharge, and the maximum current upper limit value of the output current (IO) is gradually relaxed, but the power supply unit (Uw) The output voltage (VO) may be increased in the beginning, and the set time (tB-tA) may be arbitrarily set, for example, 5 seconds to 120 seconds. That is, the so-called soft start function that gradually raises the output of the power supply unit (Uw) in the transition period from the time point (tA) to the time point (tB) contributes to protection and life of the discharge cell (Ds). Therefore, it is possible to start up the discharge cell (Ds) safely while contributing to the prevention of destruction of the discharge cell (Ds) that is sometimes generated and maintaining high ozone generation efficiency. These can be easily realized by software in a microcomputer on the power control circuit (Uwc), for example. This soft start method can be realized only on the premise of the main object of the present invention described above, and it can be said that the soft start method can enjoy the advantages of the present invention in which the power supply unit (Uw) is arranged.

  That is, in this embodiment, the tuning control unit (Us) performs a sweep operation from the upper limit frequency to the lower limit frequency in the initial stage of starting the discharge, and also performs the power control circuit (Uwc). ) Sets the output power (WO) of the power supply unit (Uw), the output voltage (VO) of the power supply unit (Uw), or the output current (IO) of the power supply unit (Uw) low. Then, we are going to gradually shift to the rating.

  Note that, for example, when the voltage signal of the resonant inductor (Lm) is looked at and exceeds a voltage value that would destroy the discharge cell (Ds), even if there is a phase difference, the inverter frequency sweep operation The frequency may be lowered to deviate from resonance, and the applied voltage to the discharge cell (Ds) may be lowered to protect the device from overvoltage application to the discharge cell (Ds).

  Next, the discharge start timing will be described. Since the inverter (Uj) performs phase modulation, it can be mentioned that a certain time is required until the inverter (Uj) has an optimum resonance frequency for the discharge cell. Generally speaking, a trigger for starting discharge is given as a signal from the outside of the discharge circuit via, for example, a photocoupler and the inverter operation of the power supply unit (Uw) and the inverter (Uj) starts. A method is proposed in which only the inverter (Uj) is driven before input. Naturally, since the power supply unit (Uw) remains in a stopped state, the power supply itself is stopped. However, for example, from a control power source for performing control, from an inverter unit or an output voltage signal (Sv) unit Since weak electricity is flowing out, the inverter (Uj) is driven using this weak leakage current as a source. Based on this, the current phase signal (Sfi) and the voltage phase signal (Sfv) can be detected. Therefore, if a frequency sweep operation is performed to tune, an approximate resonance frequency can be detected. However, at this level, the discharge cell (Ds) is tested in a region where it does not discharge or generate ozone. As described above, since the operation is performed with the target driving frequency of the inverter (Uj) before the discharge start trigger is entered, the detection time can be omitted, so that a rapid rise in ozone generation is expected after the discharge start command. it can.

  Further, since the inverter (Uj) has been operated near the resonance frequency before the power is actually supplied, it is necessary to drive the inverter (Uj) in a state of being out of the resonance frequency for an unnecessarily long time. It becomes possible to contribute to reducing the risk of destruction of the discharge circuit. This is because the inverter has zero current switching from the beginning of startup.

[Second Embodiment of Discharge Cell Discharge Circuit]
FIG. 20 is a simplified block diagram showing a discharge cell discharge circuit according to the second embodiment of the present invention. In the following description of the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals. In the discharge cell discharge circuit shown in FIG. 20 as well, a commercial AC power source, for example, a three-phase power source, which is a power supply source to the discharge cell (Ds), is connected to the rectifier (Ur) from the nodes (R, S, T). Is done. The rectifier unit (Ur) includes a plurality of diodes, performs full-wave rectification, and becomes a DC output in a power supply unit (Uw) including a power control circuit (Uwc) for supplying specified power. . As a matter of course, the power supply unit (Uw) includes a smoothing capacitor inside. The inverter (Uj) converts the DC output into alternating current, and this alternating current power is converted into a high voltage via the step-up transformer (Tr), and an inductor (on the secondary winding side of the step-up transformer (Tr)) ( Lm) is applied to a discharge cell (Ds) with a dielectric such as sapphire interposed.

  The tuning control unit (Us) takes in the AC voltage phase of the discharge cell (Ds) and the AC current phase to the discharge cell (Ds), generates a phase difference signal, and minimizes the phase difference. A drive signal is output as a pulse signal to a drive circuit (Ug) for driving the inverter (Uj) to perform feedback control. As the AC voltage phase, a winding may be further added to the step-up transformer (Tr). In this embodiment, a frequency control signal (Sfg) for driving the inverter (Uj) is used. This is because it is not necessary to prepare windings and is in agreement with the phase signal applied to the step-up transformer (Tr). The alternating current phase is received using the current flowing in the step-up transformer (Tr) and the current transformer.

  The operation of the switching elements (Q1, Q2, Q3, Q4) disposed on the inverter (Uj) will be described. The DUTY ratio of each of the switching elements (Q1, Q2) is approximately 50%, and the switching elements (Q1, Q2, Q2) During each ON time, that is, an appropriate extremely short period in which both switching elements (Q1, Q2) are OFF is set, and this is operated alternately. This operation is the same for the switching elements (Q3, Q4). In the full bridge inverter, switching elements arranged on the diagonals of a pair of switching elements (Q1, Q4) and a pair of switching elements (Q2, Q3) are alternately turned on and off. The drive frequency of the inverter (Uj) is subjected to frequency modulation having a feedback function so as to match a resonance frequency described later.

  The drive frequency of the inverter (Uj) is always near the resonance frequency of the secondary resonance unit of the transformer (Tr) composed of the parasitic capacitance (Cm) component of the discharge cell (Ds) and the inductor (Lm). To control. In the discharge cell (Ds) for generating ozone, when the high voltage is applied at the resonance frequency, the power supply unit (Uw) is the lowest supply power and the highest to the discharge cell (Ds). This is because ozone can be generated with high efficiency by applying a voltage. Therefore, the resonance frequency of the resonance part formed by the parasitic capacitance (Cm) component of the discharge cell (Ds) and the inductor (Lm) connected in series with the discharge cell (Ds) is used, and the frequency It is preferable that the high voltage is applied by driving.

  As described above, the ozone concentration is controlled by controlling the power supplied to the inverter (Uj), and at the same time, the drive frequency of the inverter (Uj) is controlled to be close to the resonance frequency in the discharge cell (Ds). Even when the discharge cell (Ds) is in the main discharge and the ozone concentration is adjusted, the best ozone generation efficiency can be enjoyed.

  In the present embodiment, the inverter (Uj) is a full bridge type using four switching elements (Q1, Q2, Q3, Q4). However, the number of switching elements is reduced to two, and the half bridge shown in FIG. It is possible to adopt a circuit form in which a switching frequency is set to a resonance frequency and the switching elements at the counter electrode are alternately operated as a pair with a duty ratio of about 50%.

  When adjusting the ozone concentration, the power control circuit (Uwc) that controls the power supply unit (Uw) controls the ozone concentration by controlling the power supplied to the inverter (Uj).

  In the present embodiment, the rectifier unit (Ur) is described using a rectifier circuit using a diode. However, the PFC technology, which is a power factor correction circuit, a step-up buck converter, and a voltage doubler rectifier circuit are used. A DC voltage may be generated, and the input power supply is not limited to a three-phase power supply, and the circuit system in this part is not the essence of the present invention.

  In the present embodiment, as a result of using the power supply unit (Uw), the effect of significantly reducing the harmonics with respect to the input of the power source was obtained. In the conventional circuit system, the node (R, S, T) is connected to the rectification unit (Ur) and is connected to the capacitor. Since this capacitor was an electrolytic capacitor having a large capacity, that is, a capacitor input type, a high harmonic current was flowing in the input power supply line. In this embodiment, the function which suppresses this is added to the electric power supply part (Uw). Therefore, since the peak value of the input current can be reduced, the power supply capacity of the power equipment to which this circuit is connected can be reduced.

  Next, the configurations of the power supply unit (Uw) and the power control circuit (Uwc) are the same as those in the first embodiment described with reference to FIG.

  Next, FIG. 21 is a block diagram showing a simplified example of the circuit of the tuning control unit (Us). In the tuning control unit (Us) shown in the figure, a current waveform is obtained by using a current transformer as current phase detection means (Ui) flowing in the resonance unit composed of the discharge cell (Ds) and the inductor (Lm). Is detected. Here, it is assumed that the current of the primary winding of the step-up transformer (Tr) is measured. A voltage waveform is detected by using a frequency control signal (Sfg) for operating the inverter (Uj) applying a voltage to the step-up transformer (Tr) as a voltage phase detection means (Uv) flowing in the resonance unit. . The details will be described below.

  First, for example, two power sources of 20V and 5V are prepared as circuit power sources. One side of two wires from the winding part of the phase detection means (Ui) is connected to the 5V line. The signal of the current waveform is detected as a so-called Sin wave centered on 5V, the power source of the comparator (A41) is connected to the 20V line, the voltage waveform or the current waveform is connected to the comparator input terminal, and the other input terminal Is connected to the 5V line. Therefore, the output from the comparator (A41) is a square wave with a DUTY ratio of 50%, and a current phase signal (Sfi) is generated. The voltage phase detection means (Uv) outputs a frequency control signal (Sfg) for operating the inverter (Uj) applying a voltage to the step-up transformer (Tr) from the microcomputer (MPU). The signal is used for the voltage phase signal (Sfv). However, since the frequency control signal (Sfg) has a delay time until the signal is transmitted to the switching elements constituting the inverter (Uj) via the periodic drive circuit (Ug), the frequency control signal is taken into consideration. A signal (Sfg) once received by the buffer (Ub) and delayed by the CR time constant circuit (C41, R46) is used as a voltage phase signal (Sfv).

  As will be described later, the microcomputer (MPU) checks the phase difference between the output current and output voltage of the inverter (Uj) and feeds back the drive frequency of the inverter (Uj). Output from a microcomputer (MPU). In the case of the discharge cell discharge circuit for generating high-concentration ozone according to this embodiment, the frequency control signal (Sfg) is generally a square wave that is controlled in the range of 10 kHz to 40 kHz.

  Since both the current phase signal (Sfi) and the voltage phase signal (Sfv) converted to the square wave are phase signals of 0-5V level, the phase difference can be measured by comparing the both, so that the comparison unit (Uf ) Can be used to measure the amount of phase difference using an exclusive OR (Exclusive-OR).

  If there is a phase difference, for example, the voltage phase signal (Sfv) is at a low level (0), and the current phase signal (Sfi) from the comparator (A41) is at a high level (1). The output of the logical sum becomes a high level (1). Conversely, when there is no phase difference, for example, the voltage phase signal (Sfv) is at a high level (1), the current phase signal (Sfi) from the comparator (A41) is at a high level (1), and The output of the exclusive OR becomes Low level (0). Therefore, the larger the phase difference is, the longer the time for the exclusive OR output to become High level (1) in time series is smoothed by the CR circuit (R45, C40) and stored in the capacitor (C40). The obtained voltage (Vsd) becomes an analog quantity, and the current phase difference signal (Sfr) can be expressed as a voltage (Vsd).

  Thereby, the microcomputer (MPU) can detect the magnitude of the phase difference signal. If the resonance unit is in the resonance state, the voltage phase signal (Sfv) and the current phase signal (Sfi) are the same. Since the phase is reached, the voltage (Vsd) of the phase difference signal (Sfr) approaches approximately zero. The generated phase difference signal (Sfr) is input to a microcomputer (MPU). The microcomputer (MPU) uses a microprocessor on the premise that the analog quantity is digitized, but analog-digital conversion is performed. A vessel may be used once. Alternatively, an analog signal may be directly used as a control circuit without using a microprocessor.

  Next, the automatic tuning operation that always operates in the vicinity of the resonance frequency is the same as in the first embodiment with respect to the time chart and operation flow when using the circuit diagram of FIG. Omitted.

  By always performing feedback as described above, it is possible to always operate in the vicinity of the resonance frequency, for example, the discharge voltage of the discharge cell (Ds) is changed by changing the pressure or temperature of the discharge cell (Ds). Even if the resonance frequency changes due to the change in the capacitance value of the parasitic capacitance (Cm), the drive frequency of the inverter (Uj) also changes in the vicinity of the changed resonance frequency. The best ozone generation efficiency can always be satisfied.

  Moreover, the experiment waveform when it implemented in FIG. 20 which is a circuit form of this invention by making a discharge cell (Ds) into a load was the same as that of the said FIG.

The conditions when the experiment was actually conducted using the discharge cell of the applicant of the present application and the obtained ozone concentration are described below.
Inverter frequency: Approximately 23 kHz
Inverter output voltage: about 150V
Inverter output power: about 110W
Discharge cell output voltage: about 7.4 kVp-p
Discharge cell: 0.5A-13 type cell + capacitor load 1nF manufactured by EBARA
Oxygen supply amount to discharge cell 0.5L / M
Amount of nitrogen added to the discharge cell 4ccm
Ozone generation amount: 160 g / Nm ³
Resonant inductor: 34mH
High-voltage transformer: primary 13 turns / secondary 19 turns / ferrite core

  The above-described capacitor load will be described. The capacitor load is a capacitor connected in parallel with the discharge cell on the electric circuit. When the design target is to set the resonance frequency, that is, the drive frequency of the inverter (Uj) to about 23 kHz, an extremely large L value is required when the capacitor is not inserted, and the product is manufactured from the viewpoint of cost and size. It becomes an unsuitable resonance inductor (Lm). In view of this problem, the resonant inductor (Lm) can be appropriately sized by increasing the parasitic capacitance (Cm) by connecting an inexpensive and small capacitor load in parallel to the discharge cell (Ds). It was. However, when a discharge cell having sufficient parasitic capacitance is selected, it is not necessary to add the capacitor load.

  As a feature of the ozone generation discharge cell (Ds), the voltage applied to the discharge cell (Ds) is applied as a sine wave. When an actual discharge occurs, the vicinity of the sine wave of the sine wave It becomes. Therefore, the ozone generation concentration increases as the drive frequency of the inverter (Uj) is higher. If the drive frequency is increased to obtain the same ozone concentration, there is an advantage that the voltage applied to the discharge cell (Ds) can be lowered accordingly. The drive frequency is generally determined by the resonance frequency (f0 = 1 / (2π√ (LC)) between the resonance inductor (Lm) and the parasitic capacitance (Cm) of the cell, and the inverter (Uj) is operated at that frequency. Therefore, if the value of the resonant inductor (Lm) is decreased and the resonant frequency (f0) is increased, the voltage applied to the discharge cell (Ds) can be lowered, and thus the applied voltage to the discharge cell (Ds). Therefore, the dielectric breakdown risk of the dielectric barrier of the discharge cell (Ds) can be reduced, and the risk of barrier breakdown that has been rarely generated can be reduced. In the method, the drive frequency of the inverter (Uj) was 5 kHz, and it was succeeded in actually lowering the applied voltage by operating around 20 kHz. Base, it was stably improved about 10% ozone generation concentration ability has been confirmed from experiments.

  As described above, according to the present embodiment, the discharge cell (Ds) is operated with the minimum input power by the operation of the tuning control unit (Us) under the stable condition using the power supply unit (Uw). Since the highest effect is obtained, the ozone can be generated at the best efficiency at all times, and the switching element on the inverter (Uj) does not unnecessarily lose resonance, so that the inverter (Uj) It is possible to reduce the stress of the switching elements (Q1, Q2, Q3, Q4) and to suppress radiation noise and conduction noise as a secondary effect. In other words, compared to the prior art, it is possible to generate the same amount of ozone with less power consumption, which contributes to reducing the running cost of the ozone generator, and provides a discharge circuit in the best mode. I was able to. Above all, even if the resonance frequency (f0) changes due to disturbance conditions or time-series factors, which is the main object of the present invention, it is possible to maximize the capability of the discharge cell (Ds). It was. As a result, the resonance frequency (f0), which was the first problem, fluctuated, and the problem that the capability of the discharge cell (Ds) could not be maximized was solved.

[Embodiment of discharge cell discharge circuit control system]
FIG. 22 is a block diagram showing, in a simplified manner, an example of the relationship between discharge cell discharge circuit control system (hereinafter referred to as “apparatus control system”) (ES), discharge cell discharge circuit (PS), and ozone detector (Od). is there. In the figure, an ozone detector (Od) outputs a signal within a voltage or current range in which the maximum and minimum ozone concentrations that can be detected are defined. The detected ozone concentration is scaled to the voltage or current level, and the ozone detector (Od) generates an analog output signal corresponding to the detected ozone concentration, that is, the device control system (ES). Is received as an input signal (Ods). Generally speaking, in the case of a current signal, since the current signal is expressed by 4 mA to 20 mA, the device control system (ES) receives the resistance (R50) once. The resistance (R50) is 250Ω, and the voltage generated at both ends of the resistance (R50) is converted into a voltage signal of 1V-5V and taken into the ozone concentration control circuit (Up) via the buffer (Ub). As a result, the ozone concentration control circuit (Up) can recognize the current ozone concentration. For the ozone concentration control circuit (Up), a programmable logic controller (PLC), for example, an analog input unit of a sequencer manufactured by Mitsubishi Electric Corporation may be used.

  On the other hand, the discharge cell discharge circuit (PS) manages the input power to the discharge cell (Ds) based on a command from the ozone concentration control circuit (Up). The ozone concentration control circuit (Up) outputs an output signal (PSd) as a current or voltage signal via the buffer (Ub). In this case, for example, an analog output unit of a sequencer manufactured by Mitsubishi Electric Corporation is used. By using a sequencer, it is easy to build a system that allows end users to easily change ozone concentration parameters using a touch panel as its interface, and enjoy its advantages. The discharge cell discharge circuit (PS) can obtain the current output power from the acquired output voltage signal (Sv) and the output current signal (Si), and the microcomputer (MPU) is used as the power control circuit (Uwc). ) Is adopted. As a result, the power control circuit (Uwc) takes in the output signal (PSd) for setting the desired power value (set power value) from the device control system (ES) as the power setting signal (Sw). Compared with the actual output power, it is possible to perform feedback control for arbitrarily managing the power.

  In this embodiment, the output signal (PSd) is expressed as a current signal, but control by communication, for example, using RS422, 232C, and 485, writing to the power setting signal (Sw) to the power control circuit (Uwc) is performed. The format to be used may be used. In the discharge cell discharge circuit (PS) of this embodiment, the RS422 system is adopted. When the desired ozone concentration and amount are very large, a large volume of ozone may be generated by using a plurality of discharge cells (Ds) and a plurality of discharge cell discharge circuits (PS). In that case, the device control system (ES) can individually control the optimum input power to the discharge cells (Ds) for the plurality of discharge cell discharge circuits (PS) by RS422 communication. is there. In that case, the driver IC of RS422, for example, (SN75ALS181) etc. is mounted on both the discharge cell discharge circuit (PS) and the device control system (ES), and connected with a crossover cable, from the device control system (ES) A method is employed in which a command is transmitted and the memory on the microcomputer (MPU) is overwritten as the power setting signal (Sw) of the discharge cell discharge circuit (PS). Moreover, even if RS485 is adopted from the point that it communicates by a one-to-many relationship, the same advantage is acquired. If such a communication system is used, when a plurality of discharge cell discharge circuits (PS) are controlled from the outside, it can be realized more inexpensively and more easily than preparing a plurality of analog output channels of a sequencer.

  Next, the concept of automatic control operation that operates in the vicinity of the highest ozone generation concentration using the block diagram of FIG. 22 will be described with reference to FIG. 23 that is a time chart diagram. The output signal (PSd) to the discharge cell discharge circuit (PS) increases the input power to the discharge cell (Ds) from the lower limit set value of the power command toward the upper limit (max). Since the output signal (PSd) to the discharge cell discharge circuit (PS) is in the vicinity of the lower limit at the initial time point, it is far from the target maximum ozone generation amount, and therefore input from the ozone detector (Od). The signal (Ods) has a small value.

  If the increase is continued, the power input point (WO), which is the maximum ozone generation point, which is the characteristic of the discharge cell (Ds), as described above, temporarily passes, but the period until the time (t11) , The maximum ozone generation point is approached, and it is recognized that the input signal (Ods) from the ozone detector (Od) is increasing. Then, if the output signal (PSd) to the discharge cell discharge circuit (PS) is increased, the output signal (PSd) to the discharge cell discharge circuit (PS) is a power input point which is the maximum ozone generation point. Passing through (WO), the best point is deviated, and the input signal (Ods) from the ozone detector (Od) decreases conversely. The ozone concentration control circuit (Up) has detected that the input signal (Ods) from the ozone detector (Od) is decreasing at the time (t12), and has passed the power input point (WO). Recognize that. That is, since the output signal (PSd) to the discharge cell discharge circuit (PS) is a command value slightly higher than the optimum point, the output signal (PSd) to the discharge cell discharge circuit (PS) is next. The control is started so as to operate in the direction of decreasing). Then, until the time point (t13), the ozone concentration control circuit (Up) detects that the input signal (Ods) from the ozone detector (Od) increases because it approaches the power input point, Conversely, at time (t14), the output signal (PSd) to the discharge cell discharge circuit (PS) is increased. By repeating this series of operations, it is controlled so that the maximum ozone concentration is always obtained, and is stable in the power band (ΔPSd) of the discharge cell discharge circuit (PS) specified in the range, that is, always the maximum ozone concentration limit. You can continue to face the value.

  By always performing feedback control in this way, even if the ozone generation capability of the discharge cell (Ds) is required to exceed the limit, the ozone concentration is exceeded by exceeding the power input point (WO). Is solved, the maximum capacity of the discharge cell (Ds) is exhibited, and ozone generation can be performed to the maximum extent. Even if the power input point (WO), which is the maximum ozone generation point, has changed, the best ozone generation efficiency can always be satisfied by following this.

  In other words, the device control system (ES) determines whether or not the discharge cell discharge circuit (PS) is charged with the electric power that has passed the best point into the discharge cell (Ds) by using the ozone concentration (Ods). When it is determined by monitoring and it is determined that excessive power is being supplied, an upper limit value is determined as needed so as to reduce the power. The output signal (PSd), which is a power command from the device control system (ES) to the discharge cell discharge circuit (PS), has a little power adjustment range of the discharge cell discharge circuit (PS) corresponding to, for example, 4 mA to 20 mA. It is set to be wide, and is actually adjusted at 4 mA to 16 mA. In some cases, it is adjusted within the range of 4 mA to 14 mA. For example, in the case of a discharge cell discharge circuit (PS) with a rated output of 200 W, it is automatically used in the range of 10 W to 140 W without any adjustment work. For example, if an ozone concentration of 150 ppm is desired, and if the ozone concentration is insufficient, the output signal (PSd) is desired to be output up to a maximum of 20 mA, but the output signal (PSd) is actually 14 mA. The power point (WO) that generates the maximum ozone at the time has passed, and the output signal (PSd) is controlled at around 14 mA, so that maximum ozone generation is performed even though the ozone concentration is insufficient. The goal is.

  The relationship between the amount of power input to the discharge cell and the ozone concentration will be described with reference to FIG. Conventionally, the highest ozone generation point was confirmed using a measuring instrument, and the upper limit (max ′) of the output signal (PSd) was finely adjusted and fixed. However, in this embodiment, even if the power input point (WO), which is the maximum ozone generation point, has changed, the maximum point can be obtained following this, so the upper limit (max), that is, the discharge The setting of the rated output power of the cell discharge circuit (PS) may be a little careless, and the labor for adjustment can be greatly reduced. However, if the maximum control is set at a position where the ozone generation concentration slightly exceeds the maximum point, it is preferable because the resolution of the output signal (PSd) can be used more effectively. In that case, since there is a variation due to external factors as described above, the maximum power value should be determined in consideration of at least this.

  Next, it is a part of the arithmetic processing method for performing the control operation of the ozone concentration control circuit (Up) explained in FIG. 22, and the increase / decrease direction of the output signal (PSd) explained in FIG. 23 is reversed. The operation will be described with reference to FIG. First, when the control start condition (CND1) is turned on in the block (b1), for example, it is determined whether or not the power supply is operating, and for example, a timer flag for processing every 5 seconds. The power output signal (PSd) reaches the discharge cell discharge circuit (PS), and the discharge cell (Ds) actually generates ozone, which is detected by the ozone detector (Od). It can be said that the system is a delayed system. Therefore, it is assumed that the output signal (PSd) is controlled after providing an appropriate time such as 5 seconds, and that the control start condition (CND1) is on thereafter.

  The software of the ozone concentration control circuit (Up) acquires the latest input signal (Ods) data from the ozone detector (Od) in the block (b2), performs so-called AD conversion and obtains the latest value (NOW_AD). get. Next, in block (b3), it is determined whether or not the latest input signal (Osd) is within the vicinity (α) of the value (k) which is the desired ozone concentration. If the current ozone concentration is not in the vicinity, that is, if there is still room for the target, the ozone detector acquired in the block (b4) the input signal (Ods) a few seconds before the previous time, for example, the above-mentioned 5 seconds before Compare with the data of the input signal (Ods) from (Od). Here, if the data of the latest input signal (Ods) is larger than the previous data, it indicates that the ozone concentration tends to increase. However, if the ozone gas concentration starts to decrease at this point, that is, if the latest input signal (Ods) is lower than the data of the input signal (Ods) several seconds ago, the output signal (PSd) increases or decreases. Since it is necessary to reverse the direction, it is determined that the power point (W0) for generating the maximum ozone has elapsed, and the increase / decrease flag (PS_ALLOW) is reversed in block (b5). Finally, in block (b6), the latest input data (Ods) acquired by this routine is stored in a variable (OLD_AD) for processing after the next number of seconds.

  The increase / decrease flag (PS_ALLOW) for determining the increase / decrease direction in the series of operations is an operation for inverting the output signal (PSd). If the example described with reference to FIG. 23 is used, the time (t12) It is synonymous with the operation in

  The control operation by the ozone concentration control unit (Up) described in FIGS. 23, 24, and 25 starts the output signal (PSd) to the discharge cell discharge circuit (PS) from the lower limit to the upper limit. And the output signal (PSd) to the discharge cell discharge circuit (PS) in a state where the input signal (Ods) level from the ozone detector (Od) has obtained the best, Corresponds to the lower limit from the upper limit in the vicinity of the output signal (PSd) to the discharge cell discharge circuit (PS) corresponding to the power input point (WO) which is the maximum ozone generation point which is the characteristic of the discharge cell (Ds). By performing automatic adjustment in a range narrower than the range, it is possible to automatically control the ozone generation amount to the maximum without reducing the ozone concentration. As a result, since the power input point (WO), which is the maximum ozone generation point, exists, the second problem of a decrease in ozone generation concentration due to excessive supply of electric power has been solved.

  Finally, with reference to FIG. 26, the concept of the control method will be simplified and described with reference to a control block diagram using the discharge cell discharge circuit (PS), the device control system (ES), and the ozone detector (Od). . This block diagram describes a feedback control loop. The control system is the same as that described in FIG. 25, and the ozone concentration control circuit (Up) of the device control system (ES) blocks an increase / decrease flag as an input signal (Ods) from the ozone detector (Od). ) To determine whether the output is positive or negative.

This flag is added to control the entire feedback. As a feedback function, the block (K1, K2 / S, K3 * S) represents the proportionality, integral, and differentiation of the deviation, which is the difference between the target ozone concentration and the current ozone concentration, and K1, K2, K3 Is a constant. Taking these three factors into account, processing is performed in series with the equation (1 / (S ² + 3S + 1)). Here, S is a variable, and the control expression is derived from Laplace transform. This is so-called PID (proportional, integral, derivative) control. In simple terms, proportional control is based on the current ozone concentration value, integral is control based on the past ozone concentration value, and differential elements predict future values. This is the control. As described above, an output signal (PSd) of power reaches the discharge cell discharge circuit (PS) from the device control system (ES), and the discharge cell (Ds) actually generates ozone, Since the ozone detector (Od) detects this, the entire control system is a delay system that takes time until follow-up, and therefore the control timing is delayed. Generally speaking, the greater the delay, the more unstable the control. However, stable compensation can be achieved by using differential elements to compensate for this. The determination of the increase / decrease flag of (INVERTorNONINVERT) determines the forward operation and the reverse operation. For example, the “heating operation” and “cooling operation” in the PID control of the temperature controller are determined. is there.

  The feedback solution obtained from the device control system (ES) is sent to the discharge cell discharge circuit (PS) as an operation amount. This manipulated variable is the output signal (PSd), which is taken into the power control circuit (Uwc) in the discharge cell discharge circuit (PS). And it employ | adopts as an electric power setting signal (Sw) for setting ozone concentration from the outside, and supplies desired electric power to the said discharge cell (Ds). As a result, ozone is generated, the ozone detector (Od) detects the ozone concentration, and the device control system (ES) inputs the analog amount as an input signal (Ods).

  A first control unit that is a tuning control unit (Us) that controls the drive frequency of the inverter (Uj), and a power control circuit that controls the output power of the power supply unit (Uw) to be a specified output power. By combining the second main control unit that is (Uwc) and the third control unit that is the ozone concentration control circuit (Up) described with reference to FIG. 26 in a well-balanced manner, the resonating unit is always reliably located near the resonance frequency. It can operate stably, enjoy the best ozone generation efficiency, control the discharge cell discharge circuit (PS), prevent destruction of the discharge cell (Ds), and keep the ozone generation efficiency high, safely discharge cell While activating (Ds), the maximum capability of the discharge cell (Ds) can be exhibited under any conditions.

  Finally, the circuit for reducing the generated noise, such as a snubber circuit, a circuit including a noise filter using a ceramic capacitor and an inductor therefor, and a protection circuit for a circuit element including a heating protection element and a switching element, are Apart from the description, it is added to the above-mentioned figure as necessary. At the same time, the configuration of the discharge cell discharge circuit according to the present invention is not limited to the circuit method and timing diagram described above.

Ds Discharge cell Uw Power supply unit Uj Inverter Tr Transformer Lm Resonant inductor Cm Parasitic capacitance Us Tuning control unit Uwc Power control circuit Ui Current phase detection unit Uv Voltage phase detection unit Sfi Current phase signal Sfv Voltage phase signal Sfr Resonance phase difference signal Uf Comparison Section Sfg frequency control signal Uz operation comparison means Uv ′ voltage detection means Su resonance voltage signal τx control period τz control period WO output power VO output voltage IO output current R, S, T node Ur rectifier C10, C11 smoothing capacitor T10 step-up transformer L1 Inductors Q10, Q11 Switching element Us ′ Tuning control unit Gq10 Driving circuit f0 Resonance frequency Δf Frequency domain interval Q Resonance sharpness Gq20 Driving units Q20, 21, 22, 23 Switching element T1 Period T2 On time Ug Periodic driving circuits Q1, Q2 The Switching element VI Input voltage Q20 Main switching element L20 Inductor C21 Smoothing capacitor D20 Diode Sv Output voltage signal Si Output current signal R22 Current detection resistor A20 Amplifier Sw Power setting signal MPU Microcomputer GQ20 Drive circuit Imax Maximum limit current value WC Constant power range W0 Constant power region line ΔW Power modulation variable region W1 Power line A40, A41 Comparator Exclusive-OR Exclusive OR R45, C40 CR circuit C40 Capacitor Vsd Voltage D50, D51, D52, D53 Diode R50, C50 CR circuit C50 Capacitor Vse Voltage Fmax Upper limit frequency Fmin Lower limit frequency t1 Time point t2 Time point t3 Time point Δf Frequency band CND1 Control start conditions B1 to B15 Blocks B20 to B25 Block k Setting value m Setting value OLD_AD Previous value NOW_AD Latest value F_ALLOW Increase / decrease direction determination flag Exclusive-OR Reverse TIMER Timer Lt Desired time COUNTER1 Counter 1
N Setpoint COUNTER2 Counter 2
M Set value tA Time point tB Time point tC Time point PS Discharge cell discharge circuit ES Device control system Od Ozone detector Ods Input signal PSd Output signal Up Ozone concentration control circuit O ₂ Oxygen O ₃ Ozone WO Power input point Ub Buffer t11 Time point t12 Time point t13 Time t14 Time ΔPSd Power band max ′ Upper limit b1 to b6 Block K1 Formula K2 / S Formula K3 * 3 Formula 1 / (S ² + 3S + 1) Formula

Claims (9)

A discharge cell discharge circuit for discharging a discharge cell (Ds) in which a dielectric is placed between a pair of discharge plates,
A power supply unit (Uw) for supplying DC power;
An inverter (Uj) that converts DC power supplied from the power supply unit (Uw) into AC power;
A transformer (Tr) that boosts AC power converted by the inverter (Uj);
By forming a closed loop in which the discharge cell (Ds) and the resonant inductor (Lm) are connected to the secondary side of the transformer (Tr), the parasitic capacitance (Cm) of the resonant inductor (Lm) and the discharge cell (Ds) A resonating part constituted by:
Further, a tuning control unit (Us) that controls the drive frequency of the inverter (Uj) so as to tune the resonance frequency of the resonance unit and the drive frequency of the inverter (Uj);
A power control circuit (Uwc) that adjusts and controls the output power of the power supply unit (Uw) so as to become a specified output power, and
Discharging is continued by two control systems of control of the drive frequency of the inverter (Uj) by the tuning control unit (Us) and power control by the power control circuit (Uwc) ,
The tuning control unit (Us) is connected to a current phase detection unit (Ui) flowing in the resonance unit and a voltage phase detection unit (Uv) of the resonance unit, and obtained by the current phase detection unit (Ui). A comparator (Uf) that compares the current phase signal (Sfi) with the voltage phase signal (Sfv) obtained by the voltage phase detection means (Uv) to obtain a resonance phase difference signal (Sfr);
In response to the resonance phase difference signal (Sfr), the inverter (Uj) is feedback-controlled by determining the value of the frequency control signal (Sfg) so that the drive frequency of the inverter (Uj) is tuned to the resonance frequency of the resonance unit. An arithmetic comparison means (Uz),
In the tuning operation by the tuning control unit (Us), the frequency control signal (Sfg) is swept from the upper limit frequency to the lower limit frequency, and the resonance phase difference signal (Sfr) level is the best. The frequency control signal (Sfg) in a state where the state is obtained is stored, and thereafter, the range corresponding to the lower limit frequency from the upper limit frequency in the vicinity of the frequency control signal (Sfg) corresponding to the resonance frequency of the resonance unit A discharge cell discharge circuit characterized in that, by performing a sweep operation in a narrower range, the resonance unit is always operated in the vicinity of the resonance frequency .   The tuning control unit (Us) is connected to voltage detection means (Uv ′) for detecting a voltage applied to the resonance inductor (Lm), and a resonance voltage signal (Su) obtained from the voltage detection means (Uv ′). ), The value of the frequency control signal (Sfg) is determined so that the drive frequency of the inverter (Uj) is tuned to the resonance frequency of the resonance unit, and feedback control is performed on the inverter (Uj). The discharge cell discharge circuit according to claim 1, comprising: In the tuning operation by the tuning control unit (Us), the frequency control signal (Sfg) is swept from the upper limit frequency to the lower limit frequency, and the resonance voltage signal (Su) level is the best resonance state. From the range corresponding to the lower limit frequency from the upper limit frequency in the vicinity of the resonance voltage signal (Su) corresponding to the resonance frequency of the resonance unit. 3. The discharge cell discharge circuit according to claim 2 , wherein the resonance unit is always operated near the resonance frequency by performing a sweep operation in a narrow range. A control cycle (τx) of the power control circuit (Uwc) for controlling the power supply unit (Uw) for supplying a predetermined power and a value of the frequency control signal (Sfg) are determined to determine the inverter (Uj And the control period (τz) of the operation comparison means (Uz) that operates so as to perform feedback control of the drive frequency of ()) is controlled with a temporal frequency difference according to the relationship of n: m (n ≠ m). The discharge cell discharge circuit according to any one of claims 1 to 3 . The power control circuit (Uwc) that operates to feedback control the power supply unit (Uw), and the operation comparison unit (Uz) that operates to feedback control the drive frequency of the inverter (Uj). 5. The discharge cell discharge circuit according to claim 1 , wherein the discharge cell discharge circuit is constituted by a single microcomputer. The tuning control unit (Us) performs a sweeping operation from the upper limit frequency to the lower limit frequency in the initial stage of starting discharge, and the power control circuit (Uwc) is operated by the power supply unit. The output power (WO) of (Uw), the output voltage (VO) of the power supply unit (Uw), or the output current (IO) of the power supply unit (Uw) is set low and gradually rated. 6. The discharge cell discharge circuit according to claim 1 , wherein the discharge cell discharge circuit is shifted. Before the start of starting discharge, the tuning control unit (Us) performs a sweep operation with the drive frequency of the inverter (Uj) from the upper limit frequency to the lower limit frequency, and the drive frequency of the inverter (Uj) is set to the resonance frequency in advance. 6. The method according to claim 1 , further comprising: detecting a value in the vicinity, storing and setting the value, starting discharge, and further increasing accuracy to a resonance frequency. Discharge cell discharge circuit. A discharge cell discharge circuit control system (ES) for controlling the discharge cell discharge circuit (PS) according to claim 1 from the outside,
The discharge cell discharge circuit control system (ES) receives an input signal (Ods) from an ozone detector (Od) that detects an ozone concentration, and also supplies power to a power supply unit (Uw) of the discharge cell discharge circuit (PS). Discharge cell discharge circuit control comprising an ozone concentration control circuit (Up) for controlling ozone concentration by outputting an output signal (PSd) for controlling output power from the outside to the power control circuit (Uwc) system. The ozone concentration control circuit (Up) increases the output signal (Psd) when the ozone concentration obtained by the input signal (Ods) does not reach a desired ozone concentration,
When the ozone concentration obtained by the input signal (Ods) is more than the desired ozone concentration, feedback control is performed so as to decrease the output signal (PSd),
Further, when the input signal (Osd) starts to decrease in spite of increasing the output signal (PSd), the sign of the operation change amount is negative,
Conversely, when the output signal (PSd) decreases, the control system performs feedback control in which the sign of the operation change amount is positive when the input signal (Osd) starts to decrease. The discharge cell discharge circuit control system according to claim 8 .

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