JP2014203608A - Power supply circuit, and ion generation device and electrical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit of low power consumption.SOLUTION: In an ion generation device, when a drain-source voltage Vds of a transistor 4 is raised due to a voltage appeared at a primary coil 5a of a step-up transformer 5 after the transistor 4 makes a transition from an on state to an off state, a diode 13 and a Zener diode 14 are turned on, and then, a current I1 flows from the primary coil 5a to a capacitor 11 via the diodes 13 and 14. The current absorbed in the capacitor 11 is supplied to the primary coil 5a when the transistor 4 is turned on, and reused. Accordingly, power consumption can be reduced.

Description

  The present invention relates to a power supply circuit, an ion generator using the same, and an electric device, and more particularly, a power supply circuit including a switching element connected in series to a primary winding of a step-up transformer, an ion generator using the same, and It relates to electrical equipment.

  In recent years, ion generators that generate ions using a discharge phenomenon have been put into practical use. The ion generator includes a power supply circuit that generates a DC high voltage for discharging the ion generating element. This power supply circuit is connected between a step-up transformer in which one terminal of a primary winding receives a DC voltage from a DC power supply, the other terminal of the primary winding and a reference voltage line, and is alternately turned on and off. A switching element to be brought into a state, and a high voltage generation circuit for generating a DC high voltage based on an AC voltage appearing in the secondary winding of the transformer.

  In such a power supply circuit, since the voltage is generated at the other terminal of the primary winding of the step-up transformer after the switching element transitions from the on state to the off state, it is necessary to protect the switching element from such a voltage. is there. As a method for protecting the switching element, there are a method in which a series connection body of a resistance element and a capacitor is connected in parallel to the switching element or the primary winding, and a method in which a diode or a varistor is connected in parallel to the primary winding (for example, (See Patent Documents 1 and 2).

JP 2012-89327 A JP 2010-103262 A

  However, in the conventional protection method, the voltage appearing at the other terminal of the primary winding of the step-up transformer is discarded wastefully, resulting in a problem that power consumption increases (see FIG. 5).

  SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a low power consumption power supply circuit, and an ion generator and an electric device using the power supply circuit.

  The power supply circuit according to the present invention is connected between a step-up transformer that receives a DC voltage from a DC power supply at one terminal of the primary winding, the other terminal of the primary winding, and a reference voltage line, and is alternately turned on. A switching element that is turned on and off, a high-voltage generating circuit that generates a DC high voltage based on an AC voltage that appears in the secondary winding of the transformer, and a primary after the switching element transitions from the on state to the off state And a protection circuit for protecting the switching element from a voltage appearing at the other terminal of the winding. In this protection circuit, a first element in which one terminal receives a DC voltage from a DC power supply, the other terminal is connected to one terminal of the primary winding, and an anode is connected to the other terminal of the primary winding. And a Zener diode having a cathode connected to the cathode of the first diode and an anode connected to one terminal of the resistance element.

  Preferably, the protection circuit further includes a first capacitor connected between one terminal of the primary winding and the reference voltage line, and the protection circuit further includes an anode receiving a DC voltage from a DC power source and a cathode A first diode connected to one terminal of the resistance element; and a second capacitor connected between the one terminal of the resistance element and a reference voltage line.

  Preferably, the Zener voltage of the Zener diode is set so that the voltage appearing at the other terminal of the primary winding after the switching element transitions from the on state to the off state is equal to or lower than the withstand voltage of the switching element.

  An ion generating apparatus according to the present invention includes the power supply circuit and an ion generating element that is driven by a DC high voltage generated by the power supply circuit and generates ions by a discharge phenomenon.

  An electric apparatus according to the present invention includes the above-described ion generator.

  In the power supply circuit according to the present invention, the voltage appearing in the primary winding of the step-up transformer after the switching element transitions from the on-state to the off-state is absorbed by the DC power supply via the first diode and the Zener diode. Therefore, since the voltage appearing at the other terminal of the primary winding is used without being wasted, power consumption can be reduced.

It is a circuit block diagram which shows the structure of the ion generator used as the comparative example 1 of this invention. 2 is a time chart showing a waveform of a control signal CNT shown in FIG. 1. 2 is a time chart showing a waveform of an AC voltage appearing in a secondary winding of the step-up transformer shown in FIG. 1. 2 is a time chart showing a waveform of a drain-source voltage of the N-channel MOS transistor shown in FIG. It is a circuit block diagram which shows the structure of the ion generator used as the comparative example 2 of this invention. It is a circuit block diagram which shows the structure of the ion generator used as one embodiment of this invention. 7 is a time chart showing a waveform of a drain-source voltage of the N-channel MOS transistor shown in FIG. 6. It is a figure for demonstrating the effect of this invention. It is another figure for demonstrating the effect of this invention.

[Comparative Example 1]
As shown in FIG. 1, an ion generator according to Comparative Example 1 of the present invention includes a DC / DC converter 1, a microcomputer 2, a capacitor 3, an N-channel MOS transistor (switching element) 4, a step-up transformer 5, a high voltage generator. A circuit 6, a positive ion generation element 7, and a negative ion generation element 8 are provided. Parts other than the ion generating elements 7 and 8 in the ion generating device constitute a power supply circuit.

  The DC / DC converter 1 generates a constant DC power supply voltage VDD (for example, 20 V) based on a power supply voltage VCC given from the outside. Capacitor 3 is connected between the output terminal of DC / DC converter 1 and the line of reference voltage VSS, and smoothes and stabilizes DC power supply voltage VDD. Further, the capacitor 3 is provided in order to flow a large current through the step-up transformer 5 instantaneously.

  Step-up transformer 5 includes a primary winding 5a and a secondary winding 5b. The number of turns of the secondary winding 5b is larger than the number of turns of the primary winding 5a. One terminal of primary winding 5a receives DC power supply voltage VDD. The drain of N channel MOS transistor 4 is connected to the other terminal of primary winding 5a, and the source thereof is connected to the line of reference voltage VSS. The breakdown voltage between the drain and source of N channel MOS transistor 4 is, for example, 100V.

  The microcomputer 2 is driven by a DC power supply voltage VCC supplied from the outside, generates a control signal CNT, and supplies it to the gate of the N-channel MOS transistor 4. As shown in FIG. 2, the control signal CNT is a signal that is alternately set to the “H” level and the “L” level in a predetermined cycle. The duty ratio of the control signal CNT is adjusted by the microcomputer 2.

  When control signal CNT is set to “H” level, N-channel MOS transistor 4 is turned on, and the line of reference voltage VSS from the output terminal of DC / DC converter 1 through primary winding 5 a and N-channel MOS transistor 4. Current flows through When control signal CNT is set to “L” level, N-channel MOS transistor 4 is turned off.

  Each time the control signal CNT is set to the “H” level, as shown in FIG. 3, ringing occurs in the secondary winding 5 b of the transformer 5. That is, when the control signal CNT is raised to the “H” level for a predetermined time, an alternating voltage V2 that gradually attenuates while vibrating positively and negatively is generated in the secondary winding 5b of the transformer 5.

  The high voltage generation circuit 6 generates a positive DC high voltage VP and a negative DC high voltage VN based on the AC voltage V2. For example, the high voltage generation circuit 6 includes two diodes, passes only the positive voltage of the AC voltage V2 through the positive ion generation element 7, and passes only the negative voltage of the AC voltage V2 to the negative ion generation element 8. Let it pass.

  The positive ion generating element 7 is driven by the positive DC high voltage VP from the high voltage generating circuit 6 and generates positive ions by a discharge phenomenon. The negative ion generation element 8 is driven by the negative DC high voltage VN from the high voltage generation circuit 6 and generates negative ions by a discharge phenomenon.

  The positive ion generation element 7 and the negative ion generation element 8 have the same configuration except that the polarity of the direct-current high voltage received is different. As the ion generating elements 7 and 8, for example, a metal wire, a metal plate having an acute angle portion, a needle-shaped metal or the like is used as a discharge electrode, and a ground potential metal plate or grid is used as an induction electrode (counter electrode). There is. Further, as other examples of the ion generating elements 7 and 8, a metal wire, a metal plate having an acute angle portion, a needle-shaped metal or the like is used as a discharge electrode, and an induction electrode is particularly arranged by using the ground instead of the induction electrode. There is something not to do.

  In the ion generating elements 7 and 8, air serves as an insulator. In addition, in the ion generating elements 7 and 8, when a high voltage is applied between the discharge electrode and the induction electrode (or between the discharge electrode and the ground), electric field concentration occurs at the acute-angled tip of the discharge electrode, and the pole at the tip is formed. Near air breaks down and ions are generated by the discharge phenomenon.

  FIG. 4A is a time chart showing changes in the drain-source voltage Vds (V) of the N-channel MOS transistor 4, and FIG. 4B is an enlarged view of the time axis around time t1 in FIG. 4A. FIG. 4 (a) and 4 (b), it is assumed that the N-channel MOS transistor 4 is off in the initial state, and Vds is equal to the DC power supply voltage VDD (20V).

  When N channel MOS transistor 4 is turned on at time t0, current flows from the output terminal of DC / DC converter 1 to the line of reference voltage VSS via primary winding 5a of step-up transformer 5 and N channel MOS transistor 4. The electromagnetic energy is stored in the primary winding 5a. At this time, Vds becomes 0V.

  When the N-channel MOS transistor 4 is turned off at time t1, the current in the primary winding 5a tends to continue to flow due to the electromagnetic energy stored in the primary winding 5a. However, since N channel MOS transistor 4 is turned off, there is no current source and a surge voltage is generated at the drain of N channel MOS transistor 4. When Vds exceeded the breakdown voltage (100V) of the N-channel MOS transistor 4, the N-channel MOS transistor 4 was damaged, and the peak value of Vds was 137V.

[Comparative Example 2]
FIG. 5 is a circuit block diagram showing a configuration of an ion generating apparatus serving as a comparative example 2 of the present invention, and is a figure to be compared with FIG. Referring to FIG. 5, the ion generator differs from the ion generator of FIG. 1 in that a Zener diode 9 is added. Zener diode 9 has its anode and cathode connected to the source and drain of N-channel MOS transistor 4, respectively. The Zener voltage Vz9 of the Zener diode 9 is, for example, 30V.

  Even after the N-channel MOS transistor 4 transitions from the ON state to the OFF state, a current continues to flow through the primary winding 5a of the step-up transformer 5, but the current between the drain and the source of the N-channel MOS transistor 4 due to a current that does not go The voltage Vds increases. When Vds exceeds the Zener voltage Vz9, a current flows through the Zener diode 9, as indicated by an arrow in the figure. For this reason, Vds is maintained at Vz9, and the N-channel MOS transistor 4 can be prevented from being destroyed. However, since the voltage appearing in the primary winding 5a when the N-channel MOS transistor 4 is turned off is wasted, the power consumption of the ion generator increases.

[Embodiment]
FIG. 6 is a circuit block diagram showing a configuration of an ion generating apparatus according to an embodiment of the present invention, and is a diagram to be compared with FIG. Referring to FIG. 6, the ion generator differs from the ion generator of FIG. 1 in that diodes 10 and 13, a capacitor 11, a resistance element 12, and a Zener diode 14 are added.

  The anode of the diode 10 is connected to the output terminal of the DC / DC converter 1. The capacitor 11 is connected between the cathode of the diode 10 and the reference voltage VSS line. One terminal (node N1) of resistance element 12 is connected to the cathode of diode 10, and the other terminal of resistance element 12 is connected to one terminal of primary winding 5a of step-up transformer 5. The anode of the diode 13 is connected to the other terminal (the drain of the N-channel MOS transistor 4) of the primary winding 5a. The cathode of the Zener diode 14 is connected to the cathode of the diode 13. The anode of the Zener diode 14 is connected to one terminal of the resistance element 12 (the cathode of the diode 10).

  When the Zener voltage of the Zener diode 14 is Vz14 and the breakdown voltage of the N-channel MOS transistor 4 is Vb, Vz14 is set to satisfy VDD + Vz14 <Vb. If only the Zener diode 14 is provided without providing the diode 13, the Zener diode 14 becomes forward biased when the N-channel MOS transistor 4 is turned on, and a large current flows through the Zener diode 14 and the N-channel MOS transistor 4. End up. Therefore, in order to prevent this, the diode 13 is connected to the Zener diode 14 in the opposite direction.

  When the N-channel MOS transistor 4 is turned off after being turned on, a current continues to flow through the primary winding 5a of the step-up transformer 5, but the drain-source voltage of the N-channel MOS transistor 4 is caused by a current that does not go. Vds rises. When Vds exceeds the Zener voltage Vz14, the Zener diode 14 is turned on, and a current I1 flows from the primary winding 5a to the node N1 through the diode 13 and the Zener diode 14 as indicated by an arrow in the figure.

  This current I1 is shunted to the capacitor 11 and the resistance element 12. The resistance value of the resistance element 12 is set to a value sufficiently larger than the internal resistance value of the capacitor 11. The diode 10 prevents the current I1 from flowing back to the DC / DC converter 10. For this reason, most of the current I1 is absorbed and stored in the capacitor 11. The current stored in the capacitor 11 is passed through the primary winding 5a and reused when the N-channel MOS transistor 4 is next turned on.

  For this reason, Vds is maintained at VDD + Vz14 (<Vb), and the N-channel MOS transistor 4 can be prevented from being destroyed. In addition, since the current I1 generated in the primary winding 5a is stored in the capacitor 11 and reused, the power consumption of the ion generator can be reduced.

  FIG. 7A is a time chart showing changes in the drain-source voltage Vds (V) of the N-channel MOS transistor 4, and FIG. 7B is an enlarged view of the time axis around time t1 in FIG. 7A. FIGS. 7A and 7B are diagrams compared with FIGS. 4A and 4B. 7A and 7B, it is assumed that the N-channel MOS transistor 4 is off in the initial state and Vds is equal to the DC power supply voltage VDD (20 V).

  When N channel MOS transistor 4 is turned on at time t 0, reference voltage VSS is output from the output terminal of DC / DC converter 1 through resistance element 12, primary winding 5 a of step-up transformer 5, and N channel MOS transistor 4. Current flows through the first line, and electromagnetic energy is stored in the primary winding 5a. At this time, Vds becomes 0V.

  When the N-channel MOS transistor 4 is turned off at time t1, the current in the primary winding 5a tends to continue to flow due to the electromagnetic energy stored in the primary winding 5a. However, since N channel MOS transistor 4 is turned off, there is no current source and a surge voltage is generated at the drain of N channel MOS transistor 4. When Vds exceeds VDD + Vz14 (= 52V), the diode 13 and the Zener diode 14 are turned on, and the current I1 flows from the primary winding 5a to the capacitor 11 via the diode 13 and the Zener diode 14. For this reason, the peak value of Vds was saturated at 52 V, and the N-channel MOS transistor 4 was not destroyed.

  Further, as shown in FIGS. 8A to 8C, the ion generators of Comparative Examples 1 and 2 are also provided with a diode 10, a capacitor 11, and a resistance element 12, and Comparative Examples 1 and 2 and the present application are provided. In each of the ion generators of the invention, the current consumption and the peak value of the drain-source voltage Vds of the N-channel MOS transistor 4 were measured.

  However, the DC power supply voltage VDD is set to 20V, a 4.7 μF ceramic capacitor is used as the capacitor 11, the resistance value of the resistance element 12 is set to 100Ω, the Zener voltage Vz of the Zener diodes 9 and 13 is set to 30V, and the N-channel MOS transistor The source-drain breakdown voltage Vb of 4 was set to 100V.

  FIG. 9 is a diagram showing measurement results. As shown in the upper part of FIG. 9, the consumption currents of Comparative Example 1, Comparative Example 2, and the present invention were 12.5 mA, 14.5 mA, and 13.1 mA, respectively. Moreover, as shown in the lower part of FIG. 9, the peak values of Vds of Comparative Example 1, Comparative Example 2, and the present invention were 136V, 31V, and 52V.

  In Comparative Example 1, the current consumption was small, but the peak value of Vds exceeded Vb, and the N-channel MOS transistor 4 was destroyed. In Comparative Example 2, the peak value of Vds was the smallest value, but the current consumption was the largest value. In the present invention, Vds was suppressed to about ½ of Vb, and the current consumption was smaller than that of Comparative Example 2. Therefore, according to the present invention, it is possible to prevent the N-channel MOS transistor 4 from being destroyed and to minimize the current consumption.

  Moreover, the ion generator of this invention can discharge | release ion to space, can improve indoor environment, and can be mounted in various electric equipment. Examples that apply to electrical equipment include air used mainly in closed spaces (houses, rooms in buildings, hospital rooms and operating rooms, cars, airplanes, ships, warehouses, refrigerators, etc.) A harmony machine, a dehumidifier, a humidifier, an air cleaner, a refrigerator, a fan heater, a microwave oven, a washing dryer, a vacuum cleaner, a sterilizer, etc. can be mentioned.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 DC / DC converter, 2 microcomputer, 3,11 capacitor, 4 N-channel MOS transistor, 5 step-up transformer, 5a primary winding, 5b secondary winding, 6 high voltage generation circuit, 7 positive ion generation element, 8 Negative ion generating element, 9,14 Zener diode, 10,13 diode.

Claims (5)

A step-up transformer in which one terminal of the primary winding receives a DC voltage from a DC power supply;
A switching element connected between the other terminal of the primary winding and a reference voltage line and alternately turned on and off;
A high voltage generating circuit for generating a DC high voltage based on an AC voltage appearing in the secondary winding of the transformer;
A protection circuit for protecting the switching element from a voltage appearing at the other terminal of the primary winding after the switching element transitions from an on state to an off state;
The protection circuit is
A resistance element having one terminal receiving a DC voltage from the DC power supply and the other terminal connected to one terminal of the primary winding;
A first diode having an anode connected to the other terminal of the primary winding;
And a Zener diode having a cathode connected to the cathode of the first diode and an anode connected to one terminal of the resistance element. And a first capacitor connected between one terminal of the primary winding and the reference voltage line;
The protection circuit is
A second diode having an anode receiving a DC voltage from the DC power source and a cathode connected to one terminal of the resistance element;
The power supply circuit according to claim 1, further comprising a second capacitor connected between one terminal of the resistance element and the reference voltage line.   The Zener voltage of the Zener diode is set so that a voltage appearing at the other terminal of the primary winding after the switching element transitions from an on state to an off state is equal to or lower than a withstand voltage of the switching element. The power supply circuit according to claim 1. The power supply circuit according to any one of claims 1 to 3,
An ion generation device comprising: an ion generation element that is driven by a high DC voltage generated by the power supply circuit and generates ions by a discharge phenomenon.   An electric apparatus comprising the ion generator according to claim 4.

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