JP4577760B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device that supplies power having two different frequencies to an inductive load (for example, an induction heating coil).

  A technique for supplying AC power having two different frequencies to an induction load such as an induction heating coil is known. Examples of the two different frequencies include a high frequency (for example, 100 kHz to 2.0 MHz) and a low frequency (for example, 1 kHz to 50 kHz). As one of such technologies, high frequency AC power is output from the oscillator to the matching circuit unit, and the impedance of the load (induction heating coil and object to be heated) is matched to the high frequency output impedance in the matching circuit unit. In addition to supplying high frequency AC power to the induction heating coil, low frequency AC power is output from the oscillator to the matching circuit unit, and the impedance of the load (induction heating coil and object to be heated) is low in this matching circuit unit. A technique is known in which AC power having a low frequency is supplied to an induction heating coil so as to match the output impedance of the frequency (see Patent Document 1). The matching circuit unit that matches the impedance of the load to the high frequency AC power is formed of a series resonant circuit, and the matching circuit unit that matches the impedance of the load to the AC power of the low frequency is a parallel resonant circuit (or series resonant circuit). And LC filter.

  In addition, as another technique described above, AC power having a high frequency is output from the oscillator to the matching circuit unit, and the impedance of the load (induction heating coil and object to be heated) is output at a high frequency in the matching circuit unit. A high frequency AC power is supplied to the induction heating coil in accordance with the impedance, and an AC power having a low frequency is output from the oscillator to the matching circuit unit. In this matching circuit unit, a load (induction heating coil and object to be heated) is output. A technique is known in which the impedance of the above is matched with the output impedance of a low frequency and AC power of a low frequency is supplied to the induction heating coil (see Patent Document 2). The matching circuit unit for matching the impedance of the load to the high frequency AC power is configured by a series resonant circuit, and the matching circuit unit for matching the impedance of the load to the AC power of the low frequency is configured by a parallel resonant circuit.

In the technique disclosed in Patent Document 1 described above, in order to prevent AC power having a high frequency from entering an oscillator (low frequency oscillator) that oscillates AC power having a low frequency, a circuit for a low frequency oscillator is used. It is necessary to connect the reactor Lf. According to Patent Document 1, this reactor Lf must be at least four times larger than the inductance of the inductive load. Therefore, there is a problem that it is necessary to connect a very large reactor Lf to the low frequency oscillator circuit. In the technique disclosed in Patent Document 2 described above, the voltage across the induction heating coil is the same as the secondary voltage of the transformer included in the matching circuit. For this reason, when the matching circuit is grounded, there is a problem that the ground potential of the inductive load becomes the same as the secondary voltage of the transformer and the possibility of discharging from the inductive load increases.
Japanese Patent No. 3150968 (for example, FIGS. 3 and 4) JP 2003-342633 A (for example, FIG. 7)

  In order to solve the above problem, the present inventors have a first oscillator that outputs AC power having a predetermined first frequency, and a first oscillator that outputs AC power having a second frequency higher than the first frequency. Two oscillators and a matching unit that matches the impedance of a predetermined load with the output impedances of the first and second oscillators, and supplies AC power output from the first and second oscillators to one inductive load. In the power supply apparatus, an AC current having the second frequency output from the second oscillator is prevented from entering the first oscillator, and a series load is used to match the impedance of a predetermined load with the output impedance from the first oscillator. A power supply device having a resonance circuit is proposed. According to this power supply device, there is an effect that a reactor for preventing AC power having a high frequency from entering a circuit for a low frequency can be reduced. The above series-parallel resonant circuit will be described with reference to FIG.

  FIG. 6A shows a series-parallel resonant circuit, and FIG. 6B shows an equivalent circuit of the circuit shown in FIG.

  In the series-parallel resonance circuit, there are two resonance points (resonance frequencies) of series resonance and parallel resonance, and the first oscillator basically operates near the parallel resonance frequency. An equivalent circuit of the resonance circuit during this operation is as shown in FIG.

In the equivalent circuit shown in (b), since the reactor L1 and the impedance Zp of the parallel resonance circuit are connected in series, and the first oscillator operates at the parallel resonance point, the impedance Zp approximately becomes the resistance Rp. As a result, in the equivalent circuit shown in (b), the reactor L1 and the resistor Rp are connected in series, and the output voltage of the first oscillator, the phase difference of the current, and the delay angle α are expressed by α = tan ⁻¹ {ωp · L1 / Rp}. Therefore, since the power factor PF of the output power of the first oscillator is PF = cos α, α does not become zero unless L1 becomes zero. Since α is generally 45 ° to 20 °, the power factor PF is a value of about 0.7 to 0.93.

  An object of this invention is to provide the electric power supply apparatus which improved (improved) the power factor in view of the said situation.

To achieve the above object, a power supply apparatus according to the present invention includes a first oscillator that outputs AC power having a predetermined first frequency, and a first oscillator that outputs AC power having a second frequency higher than the first frequency. Two oscillators and a matching unit that matches the impedance of a predetermined load with the output impedances of the first and second oscillators, and the first oscillator includes a first forward conversion unit that converts AC power into DC power; A voltage type comprising: a first smoothing capacitor that smoothes the DC power output from the first forward conversion unit; and a first inverse conversion unit that converts the DC power smoothed by the first smoothing capacitor into AC power. The second oscillator includes a second forward converter that converts AC power into DC power, a second smoothing capacitor that smoothes the DC power output from the second forward converter, and the second Smoothing capacitor A power supply for supplying a single inductive load with the AC power output from the first and second oscillators, the voltage source having a second inverse conversion unit that converts the smoothed DC power into AC power. In the device
(1) The matching unit
(1-1) a reactor through which an alternating current having a first frequency oscillated from the first oscillator flows through the inductive load, and a matching capacitor connected in series to the reactor;
(1-2) A bypass capacitor through which an alternating current having a second frequency oscillated from the second oscillator flows to the inductive load is provided.

here,
(2) The reactor and the matching capacitor may form a series resonance circuit that compensates a power factor of a predetermined inductive load.

Also,
(3) The bypass capacitor prevents an alternating current oscillated from the second oscillator from entering the first oscillator, and is electrically connected in series and has a connection point thereof. It may consist of two capacitors of equal capacity grounded.

further,
(4) Instead of the first and second forward conversion units, a forward conversion unit that converts AC power output from one AC power source into DC power,
(5) The first smoothing capacitor is for smoothing the DC power output from the forward conversion unit, and
(6) The second smoothing capacitor may smooth the DC power output from the forward conversion unit.

Furthermore,
(7) A transformer having a primary side winding to which the second reverse conversion unit is connected and a secondary side winding to which the first reverse conversion unit is connected,
(8) The secondary winding of the transformer may be divided into two parts, a first partial secondary winding and a second partial secondary winding.

Furthermore,
(9) The two capacitors having the same capacity are connected between the first part secondary winding and the second part secondary winding,
(10) The other end of each of the two capacitors having the same capacity may be connected to the first inverse conversion unit.

Furthermore,
(11) The reactor and the matching capacitor may be electrically connected in series between the first partial secondary winding and the first inverse conversion unit.

Furthermore,
(12) A transformer in which the first inverse conversion unit includes a primary winding connected via the reactor and the matching capacitor, and a secondary winding connected to the two capacitors having the same capacity. With
(13) The transformer may match the impedance of a predetermined inductive load with the output impedance of the first oscillator.

In the power supply device of the present invention, a series resonance circuit having a reactor through which an alternating current having a first frequency oscillated from a first oscillator flows to an inductive load and a matching capacitor connected in series to the reactor is formed. The output voltage, current phase difference, and delay angle α of the first oscillator 20 output to the series resonance circuit are α = tan ⁻¹ {Q (1− (ωs ² / ω ² )) ² }. Can express. When operating at the series resonance point, ω = ωs, so α = 0 and the power factor PF of the output power is 1. Actually, a slight delay angle (α is about 5 to 10 °) is taken in order to prevent the lead phase. As a result, the actual power factor is improved to about 0.98.

  In the above equation, the unit of the delay angle α is rad (radian) or degree (degree), Q is a resonance circuit quality factor, and Q = ω (L1 + L0) / R0. Further, ωs is a series resonance angular frequency, ωs = 1 / √ {((L1 + L0) C3)}, and its unit is rad (radian). Further, ω is an angular frequency, and its unit is rad (radian).

  The present invention has been realized in a power supply device that supplies AC power to an induction heating coil for induction heating of gears, screws, and the like.

  With reference to FIG. 1 and FIG. 2, Example 1 of the electric power supply apparatus of this invention is demonstrated.

  FIG. 1 is a circuit diagram showing a schematic configuration of an example of a power supply apparatus of the present invention. FIG. 2 is a perspective view schematically showing a transformer or the like used in the circuit of FIG.

  The power supply device 10 supplies AC power having two different frequencies simultaneously to one induction heating coil 14 (which is an example of an induction load) for induction heating the object to be heated 12 such as a gear. is there. The frequency of the AC power is obtained by appropriately converting the frequency of the AC power from the AC power sources (commercial power sources) 16 and 18. The power supply apparatus 10 is roughly divided into a first oscillator 20 that converts the frequency of the AC power output from the AC power supply 16 and outputs AC power having a predetermined first frequency (MF), and an output from the AC power supply 18. The second oscillator 40 that converts the frequency of the AC power thus generated and outputs AC power having a predetermined second frequency (HF), and the impedance of the object to be heated 12 and the induction heating coil 14 are the first and second oscillators 20. , 40 and a matching device 60 for matching (matching) the output impedance. The predetermined first frequency here refers to a frequency in the range of 1 kHz to 50 kHz, for example, and the predetermined second frequency refers to a frequency in the range of 100 kHz to 2.0 MHz, for example. Therefore, the second frequency is higher than the first frequency, and conversely, the first frequency is lower than the second frequency. In addition, the equivalent inductance L0 of the induction heating coil 14 is in the range of several hundreds nH to several μH.

  The first oscillator 20 includes a first forward converter 22 (converter) that converts AC power output from the AC power source (commercial power source) 16 into DC power, and DC power output from the first forward converter 22. A first smoothing capacitor CF1 to be smoothed and a first reverse conversion unit (MF reverse conversion unit) 24 (inverter) for converting the DC power smoothed by the first smoothing capacitor CF1 into AC power having the predetermined first frequency. ). A known bridge rectifier circuit is formed in the first forward converter 22. In addition, the first inverse conversion unit 24 incorporates a plurality of switching elements composed of well-known transistors, and the DC power is changed to the AC power of the first frequency by performing on / off control of the plurality of switching elements. Convert.

  The second oscillator 40 includes a second forward converter 42 (converter) that converts AC power output from the AC power source (commercial power supply) 18 into DC power, and DC power output from the second forward converter 42. A second smoothing capacitor CF2 to be smoothed, and a second reverse conversion unit (HF reverse conversion unit) 44 (inverter) for converting the DC power smoothed by the second smoothing capacitor CF2 into AC power having the predetermined second frequency. ). A known bridge rectifier circuit is formed in the second forward converter 42. The second inverse conversion unit 44 incorporates a plurality of switching elements composed of well-known transistors, and the DC power is changed to the AC power of the second frequency by controlling on / off of the plurality of switching elements. Convert.

  The matching unit 60 includes a series resonance circuit 62 corresponding to AC power having a first frequency oscillated from the first oscillator 20 and a series resonance corresponding to AC power having a second frequency oscillated from the second oscillator 40. A circuit 64 is formed. According to the electric circuit principle that “the maximum power can be supplied to the load when the output impedance of the power supply matches the load impedance”, the output impedance (resistance) of the power supply matches the impedance (resistance) of the resonance circuit. It is necessary to make it. For this matching, the matching device 60 is formed with a series resonance circuit 62 and a series resonance circuit 64.

  The series resonance circuit 62 includes a reactor L1 having several μH, a matching capacitor C3, and an induction heating coil 14 having an equivalent inductance L0. Reactor L1 and matching capacitor C3 are connected in series, and when an alternating current having a first frequency oscillated from first oscillator 20 flows through induction heating coil 14, it passes (passes) through reactor L1 and matching capacitor C3. The capacitance of the matching capacitor C3 is generally in the range of several tens of μF to several hundreds of μF. The equivalent inductance L0 is several μH. For the first oscillator 20, the reactor L1, the matching capacitor C3, and the induction heating coil 14 form a series resonance circuit. The reactor L <b> 1 also has a function of preventing the alternating current output from the second oscillator 40 from entering the first oscillator 20.

The series resonance circuit 64 includes a matching capacitor C1 of several hundreds nF, a current transformer 70, and a load coil equivalent inductance (N1 / N2) ² L0. The matching capacitor C <b> 1 also has a function of preventing the alternating current output from the first oscillator 20 from entering the second oscillator 40. N1 / N2 described above is the ratio of the number of turns N1 of the primary winding 71 of the current transformer 70 and the number of turns N2 of the secondary winding 72 described later. The number of turns N2 is the sum (total) of the number of turns N2A of the first partial secondary winding 72A described later and the number of turns N2B of the second partial secondary winding 72B. That is, N2 = N2A + N2B.

  As described above, the current transformer 70 is one of the components constituting the series resonance circuit 64. The current transformer 70 includes a primary side winding 71 connected to the second oscillator 40 and a secondary side winding 72 connected to the first oscillator 20. The primary side winding 71 is wound in a coil shape (spiral), and as shown in FIG. 2, a belt-like secondary side winding 72 is formed so as to surround the outer peripheral surface of the primary side winding 71. Is arranged. A matching capacitor C1 is connected to the terminal 71a of the primary winding 71. Therefore, the terminal 71a of the primary side winding 71 is connected to the second oscillator 40 via the matching capacitor C1. The terminal 71b of the primary winding 71 is directly connected to the second oscillator 40 without any intervention.

  The material of the primary winding 71 and the secondary winding 72 is copper (for example, JIS C1100) from the viewpoint of conductivity and economy. The outer diameter of the primary winding 71 (outer diameter as a coil) is, for example, 300 mm, and the plate thickness (thickness) of the secondary winding 40 is, for example, 3 mm. Here, although the coil-shaped thing was shown as the primary side coil | winding 71, you may use the copper pipe whose outer diameter is 12.7 mm and whose thickness (thickness) is 1.5 mm. Moreover, the height of the primary side winding 71 and the secondary side winding 72 is the same, and these gaps (gap) are in the range of about 5 mm to 10 mm. That is, the distance from the outer peripheral surface of the primary side winding 71 to the inner peripheral surface of the secondary side winding 72 is a distance within a range of about 5 mm to 10 mm.

  The secondary winding 72 is a belt-like one that surrounds the outer peripheral surface of the primary winding 71 and is divided into two parts. The two parts themselves are electrically disconnected from each other. Yes. The secondary side winding 72 includes a first partial secondary side winding 72 </ b> A that surrounds a half-circumferential portion of the outer peripheral surface of the primary side winding 71 and a first partial secondary of the outer peripheral surface of the primary side winding 71. It consists of a second part secondary winding 72B that surrounds a half-circumferential part that is opposite to the half-circumferential part that the side winding 72A surrounds. The secondary winding 72 is divided into two equal parts to form a first partial secondary winding 72A and a second partial secondary winding 72B, which have the same shape and have a primary winding. 71 are arranged symmetrically (or surrounded).

  Output terminals 72Aa and 72Ab are formed at both ends in the circumferential direction of the first partial secondary winding 72A, respectively. Similarly, output terminals 72Ba and 72Bb are formed at both ends in the circumferential direction of the second partial secondary winding 72B, respectively. The first oscillator 20, the bypass capacitors C2A and C2B, the matching capacitor C3, and the reactor L1 are connected to the output terminal 72Aa and the output terminal 72Ba. The coil terminal of the bypass capacitor C2A is directly electrically connected to the output terminal 72Aa of the secondary winding 72, and the coil terminal of the bypass capacitor C2B is directly connected to the output terminal 72Ba of the secondary winding 72. Electrically connected. The capacitances of the two bypass capacitors C2A and C2B are equal and are in the range from several tens of μF to several hundreds of μF. The secondary winding 72 of the current transformer 70 is divided into two parts, a first partial secondary winding 72A and a second partial secondary winding 72B, and bypass capacitors C2A and C2B are also provided. It is divided into two.

  The two bypass capacitors C2A and C2B described above are connected in series by a conductive wire 63, and the two bypass capacitors C2A and C2B are grounded (grounded) through the conductive wire 63. That is, the connection point of these two bypass capacitors C2A and C2B is grounded. The secondary winding 72 of the current transformer 70 is divided into two parts, a first partial secondary winding 72A and a second partial secondary winding 72B, and bypass capacitors C2A and C2B are also provided. It is divided into two. As a result, the ground potential (ground potential) of the induction heating coil 14 becomes half (1/2) of the voltage at both ends of the induction heating coil 14 (in other words, the ground potential of the induction heating coil 14 is a current transformation). Therefore, the possibility of discharging from the induction heating coil 14 is low. The alternating current having the second frequency (high frequency) oscillated from the second oscillator 40 flows to the induction heating coil 14 via (through) the two bypass capacitors C2A and C2B. The two bypass capacitors C <b> 2 </ b> A and C <b> 2 </ b> B also have a function of preventing the alternating current output from the second oscillator 40 from entering the first oscillator 20.

  Here, the power factor of the output power from the first oscillator 20 will be described with reference to FIG.

  FIG. 3A shows an equivalent circuit of a series resonance circuit corresponding to AC power having the first frequency oscillated from the first oscillator, and FIG. 3B shows an equivalent when the bypass capacitors C2A and C2B are ignored. The circuit is shown.

  As described above, the bypass capacitors C2A and C2B connected to the series resonance circuit 62 allow the alternating current having the second frequency (high frequency) oscillated from the second oscillator 40 to flow through the induction heating coil 14. It is a capacitor that passes through and has a smaller capacity than the matching capacitor C3. The total capacity (C2A · C2B / (C2A + C2B)) of the two bypass capacitors C2A and C2B is about 1/10 or less of the capacity of the matching capacitor C3. Therefore, the influence of the bypass capacitors C2A and C2B can be ignored for the alternating current having the first frequency oscillated from the first oscillator. As a result, when functioning as the series resonance circuit 62, it can be regarded as a series resonance circuit composed simply of the reactance L1, the matching capacitor C3, and the equivalent inductance L0 as in the equivalent circuit shown in FIG.

The output voltage, current phase difference, and delay angle α of the first oscillator 20 output to the equivalent series resonance circuit shown in FIG.
α = tan ⁻¹ {Q (1- (ωs ² / ω ² )) ² }. When operating at the series resonance point, ω = ωs, so α = 0 and the power factor PF of the output power is 1. Actually, a slight delay angle (α is about 5 to 10 °) is taken in order to prevent the lead phase. As a result, although the actual power factor is about 0.98, the power factor is greatly improved as compared with the circuit shown in FIG. 6, and the power factor of the induction heating coil 14 is compensated.

  In the above equation, the unit of the delay angle α is rad (radian) or degree (degree), Q is a resonance circuit quality factor, and Q = ω (L1 + L0) / R0. Further, ωs is a series resonance angular frequency, ωs = 1 / √ {((L1 + L0) C3)}, and its unit is rad (radian). Further, ω is an angular frequency, and its unit is rad (radian).

  An example in which the object to be heated 12 is induction-heated using the above-described power supply apparatus 10 will be described.

  When power is supplied to an induction heating system (not shown) including the power supply device 10, AC power is supplied from the AC power supply 16 to the first oscillator 20 and from the AC power supply 18 to the second oscillator 40. AC power is supplied. In the first oscillator 20, the AC power supplied from the AC power supply 16 is converted into DC power by the first forward conversion unit 22, and the DC power output from the first forward conversion unit 22 is smoothed by the first smoothing capacitor CF1. The input DC power is converted into AC power having a first frequency (for example, a frequency within a range of 1 kHz to 50 kHz) by the first inverse conversion unit 24. The converted AC power is output to matching unit 60.

  On the other hand, in the second oscillator 40, the AC power supplied from the AC power source 18 is converted into DC power by the second forward converter 42, and the DC power output from the second forward converter 42 is converted into the second smoothing capacitor CF2. The input DC power is converted into AC power having a second frequency (for example, a frequency within a range of 100 kHz to 2.0 MHz) by the second inverse conversion unit 44. Is done. The converted AC power is output to matching unit 60.

  The matching unit 60 receives the AC power having the first frequency output from the first oscillator 20 and the AC power having the second frequency output from the second oscillator 40. The AC power having the first frequency is input to the series resonance circuit 62 and enters a resonance state. An AC current having the resonance frequency flows through the induction heating coil 14, and an eddy current is induced in the article 12 to be heated by the AC current. The heated object 12 is heated. In addition, since the capacitor C <b> 1 is disposed in the series resonance circuit 64, AC power having the first frequency output from the first oscillator 20 cannot enter the second oscillator 40.

  The AC power having the second frequency is input to the series resonance circuit 64 and enters a resonance state. An AC current having the resonance frequency flows through the induction heating coil 14, and an eddy current is induced in the article to be heated 12 by the AC current, and the target is covered. The heated object 12 is heated. The series resonant circuit 62 is provided with a reactor L1, and AC power having the second frequency output from the second oscillator 40 flows to the induction heating coil 14 via the bypass capacitors C2A and C2B. Therefore, AC power having the second frequency output from the second oscillator 40 does not enter the first oscillator 20.

  As described above, in the power supply device 10, the secondary winding 72 of the current transformer 70 is divided into two parts, the first partial secondary winding 72A and the second partial secondary winding 72B. The bypass capacitors C2A and C2B are also divided into two. As a result, the ground potential (ground potential) of the induction heating coil 14 becomes half (1/2) of the voltage at both ends of the induction heating coil 14 (in other words, the ground potential of the induction heating coil 14 is a current transformation). Therefore, the possibility of discharging from the induction heating coil 14 is low. Further, as described above, when operating at the resonance point of the series resonance circuit 62, ω = ωs, so α = 0 and the power factor PF of the output power is 1. Actually, a slight delay angle (α is about 5 to 10 °) is taken in order to prevent the lead phase. As a result, although the actual power factor is about 0.98, the power factor is greatly improved as compared with the circuit shown in FIG.

  With reference to FIG. 4, Example 2 of the electric power supply apparatus of this invention is demonstrated.

  FIG. 4 is a circuit diagram showing a schematic configuration of Embodiment 2 of the power supply apparatus of the present invention. In this figure, the same components as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.

  In the power supply apparatus 10 according to the first embodiment, independent (one by one) forward conversion units 22 and 42 are connected to the two AC power sources 16 and 18, respectively, and AC power having different frequencies is supplied to the inverse conversion units 24 and 44. On the other hand, in the power supply apparatus 100 of the second embodiment, AC power is input from one AC power supply 102 to one forward conversion unit 104, and two reverse conversion units are input from this one forward conversion unit 104. A feature is that DC power is input to 106 and 108. In addition, the power supply device 100 according to the second embodiment is also characterized in that a device for controlling the AC power output from each of the two inverse conversion units 106 and 108 is provided.

  The power supply apparatus 100 supplies AC power having two different frequencies to one induction heating coil 14 for induction heating the object to be heated 12 such as a gear. The frequency of the AC power is obtained by appropriately converting the frequency of the AC power from the AC power source (commercial power source) 102. The power supply apparatus 100 is roughly divided into a forward conversion unit 104 that converts AC power output from the AC power source 102 into DC power, and first and second DC power that is converted by the forward conversion unit 104 is input. The impedances of the inverse conversion units 106 and 108 and the object to be heated 12 and the induction heating coil 14 (an example of the predetermined load referred to in the present invention) are matched with the output impedances from the first and second inverse conversion units 106 and 108. And a matching unit 60 for matching.

  The first reverse conversion unit (MF reverse conversion unit) 106 converts the DC power output from the forward conversion unit 104 into AC power having a predetermined first frequency (for example, a frequency in the range of 1 kHz to 50 kHz). It is. The second reverse conversion unit (HF reverse conversion unit) 108 converts the DC power output from the forward conversion unit 104 into AC power having a predetermined second frequency (for example, a frequency within a range of 100 kHz to 2.0 MHz). To do. Since the configuration and operation of the matching unit 60 are the same as those of the matching unit 60 of the first embodiment, a description thereof is omitted here.

  The power supply apparatus 100 includes a low-frequency DC current sensor CT1a that detects a DC current (Idc1) output from the forward conversion unit 104 and before being input to the first reverse conversion unit 106, and a first reverse conversion unit 106. And a low-frequency output current sensor CT1b that detects a direct current (Io1) before being input to the matching unit 60. Further, the power supply apparatus 100 includes a high-frequency DC current sensor CT2a that detects a DC current (Idc2) that is output from the forward conversion unit 104 and before being input to the second reverse conversion unit 108, and a second reverse conversion unit. And a high frequency side output current sensor CT2b that detects a direct current (Io2) before being output from 108 and input to the matching unit 60.

The power supply apparatus 100 also receives a power constant control circuit 116 to which the DC current Idc1 detected by the low frequency side DC current sensor CT1a is input and a DC current Idc2 detected by the high frequency side DC current sensor CT2a. The power constant control circuit 118 is provided. The two power constant control circuits 116 and 118 also receive the DC voltage Vdc of the DC power output from the forward conversion unit 104. The constant power control circuit 116 compares a power setting signal ^* Pdc1 input from the outside such as an operation panel (not shown) with a DC power signal Pdc1 generated based on the DC voltage Vdc and the DC current Idc1. An error signal (control voltage signal) ΣV1 in a voltage format necessary for frequency shift control is generated and output to the voltage frequency converter 136. That is, the constant power control circuit 116 generates ΣV1 based on ΣV1 = A · ( ^* Pdc1−Pdc1). A is a coefficient.

Similarly, in the constant power control circuit 118, a power setting signal ^* Pdc2 input from the outside such as an operation panel (not shown) is used as a DC power signal Pdc2 generated based on the DC voltage Vdc and the DC current Idc2. By comparison, an error signal (control voltage signal) ΣV2 in a voltage format necessary for frequency shift control is generated and output to the voltage frequency converter 138. That is, the constant power control circuit 118 generates ΣV2 based on ΣV2 = A · ( ^* Pdc2−Pdc2). A is a coefficient.

  Further, the power supply apparatus 100 has a frequency lower limit detector 126 to which the current Io1 detected by the low frequency side output current sensor CT1b is input and a frequency to which the current Io2 detected by the high frequency side output current sensor CT2b is input. A lower limit detector 128 is provided. The frequency lower limit detector 126 also receives the voltage Vo1 of AC power output from the first inverse conversion unit 106. Similarly, the voltage lower limit detector 128 also receives the voltage Vo2 of AC power output from the second inverse conversion unit 108. As is well known, current lag occurs in a range higher than the resonance point and current advance occurs in a range lower than the resonance point. Therefore, the frequency lower limit detector 126 monitors the phase relationship between both the input current Io1 and the voltage Vo1. By detecting the progress of both the current Io1 and the voltage Vo1, a limit signal of maximum power is obtained, and this limit signal is output to the constant power control circuit 116. Similarly, the frequency lower limit detector 128 obtains a maximum power limit signal by monitoring the phase relationship between both the input current Io2 and the voltage Vo2 and detecting the advance of both the current Io2 and the voltage Vo2. The signal is output to the constant power control circuit 118.

  Further, the power supply apparatus 100 includes a voltage / frequency conversion which is a V / F circuit (a circuit for making the ratio of the voltage V and the frequency F substantially constant) that converts the frequency to a predetermined frequency proportional to the input error signal ΣV1. And a voltage / frequency converter 138 which is a V / F circuit for converting to a predetermined frequency proportional to the input error signal ΣV2. In the voltage frequency converter 136, when the error signal ΣV1 is, for example, 0 to 15V, the voltage is converted so as to be a predetermined frequency within a range of 1 kHz to 50 kHz, and a Gate1 signal representing this frequency is output to the first inverse conversion unit 106. To do. The first inverse conversion unit 106 converts DC power into AC power so as to have a frequency represented by the input Gate1 signal. On the other hand, in the voltage frequency converter 138, when the error signal ΣV2 is 0 to 15 V, for example, the voltage signal is converted to a predetermined frequency within the range of 100 kHz to 2.0 MHz, and the Gate2 signal representing this frequency is subjected to the second inverse conversion. Output to the unit 108. The second inverse conversion unit 108 converts the DC power into AC power so as to have the frequency represented by the input Gate2 signal. Therefore, the frequency of the AC power output from the first inverse conversion unit 106 is the first frequency within the range of 1 kHz to 50 kHz, and the frequency of the AC power output from the second inverse conversion unit 108 is 100 kHz to 2.0 MHz. Is the second frequency within the range.

  The AC power having two different frequencies output from the first inverse conversion unit 106 and the second inverse conversion unit 108 is input to the matching unit 60, and the induction heating is performed in the same manner as the power supply apparatus 10 of the first embodiment. AC power is supplied to the coil 14 and the object to be heated 12 is induction-heated.

  As described above, in the power supply apparatus 100 according to the second embodiment, only one AC power source 102 and one forward conversion unit 104 are required, and thus the power conversion apparatus 100 having a simple configuration can be obtained. The power factor PF of the output power is the same as that in the first embodiment.

  With reference to FIG. 5, Example 3 of the electric power supply apparatus of this invention is demonstrated.

  FIG. 5 is a circuit diagram showing a schematic configuration of Embodiment 3 of the power supply apparatus of the present invention. In this figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

  The power supply device 200 of the third embodiment is different from the power supply device 10 of the first embodiment (see FIG. 1) in that the configuration of the matching unit 210 of the power supply device 200 of the third embodiment is the power of the first embodiment. This is different from the configuration of the matching device 60 of the supply device 10. The matching device 210 includes a current transformer 220 for impedance conversion on the low frequency (first frequency) side, and a matching capacitor C3 connected in series to the primary winding 221 of the current transformer 220. This point is different from the matching unit 60 of the power supply apparatus 10. This difference will be described, but the description of the same configuration will be omitted.

  The matching unit 210 is formed with a series resonance circuit 230 corresponding to AC power having the first frequency oscillated from the first oscillator 20. As described above, according to the electric circuit principle that “the maximum power can be supplied to the load when the output impedance of the power supply matches the load impedance”, the output impedance (resistance) of the power supply and the impedance (resistance) of the resonance circuit are It is necessary to match (match). For this matching, the matching device 210 is formed with a series resonance circuit 230 and a series resonance circuit 64. The current transformer 220 is for matching the impedance of the induction heating coil 14 with the output impedance of the first oscillator 20.

  The series resonance circuit 230 for the first oscillator 20 includes a reactor L1 of several μH, a matching capacitor C3, a current transformer 210 for matching load impedance, an induction heating coil 14 having an equivalent inductance L0, and the like. The equivalent inductance L0 is several μH.

  In the third embodiment, since the current transformer 220 is arranged in the matching unit 210, the output current of the first oscillator 20 and the value of the current flowing through the series resonance circuit 230 can be reduced, and the circuit loss can be reduced. Further, a matching capacitor C3 is connected to the primary winding 221 of the current transformer 220, and two bypass capacitors C2A and C2B are connected to the secondary winding 222. Since the alternating current having a high frequency (second frequency) oscillated from the second oscillator 40 passes through the two bypass capacitors C2A and C2B, the two bypass capacitors C2A and C2B are connected to the alternating current having the second frequency. Dedicated bypass. Since the second frequency is a high frequency, the capacity of the two bypass capacitors C2A and C2B can be reduced, and this capacity can be about one-tenth of the capacity of the matching capacitor C3. Further, as the two bypass capacitors C2A and C2B, a small-capacitance capacitor having excellent high frequency characteristics can be used. As described above, the matching capacitor C3 is connected to the primary winding 221 of the current transformer 210, and a capacitor for high voltage (small current) can be used, so that circuit loss can be reduced. The power factor PF of the output power is the same as that in the first embodiment.

It is a circuit diagram which shows schematic structure of an example of the electric power supply apparatus of this invention. It is a perspective view which shows typically the transformer etc. which are used in the circuit of FIG. (A) shows an equivalent circuit of a series resonance circuit corresponding to AC power having a first frequency oscillated from a first oscillator, and (b) shows an equivalent circuit when bypass capacitors C2A and C2B are ignored. Show. It is a circuit diagram which shows schematic structure of Example 2 of the electric power supply apparatus of this invention. It is a circuit diagram which shows schematic structure of Example 3 of the electric power supply apparatus of this invention. (A) shows a series-parallel resonant circuit, and (b) shows an equivalent circuit of the circuit of (a) in operation.

Explanation of symbols

10, 100, 200 Power supply device 16, 18 AC power supply (commercial power supply)
20 First Oscillator 22 First Forward Converter 24 First Inverse Converter 40 Second Oscillator 42 Second Forward Converter 44 Second Inverse Converters 60 and 210 Matching Device 62 Series Resonant Circuit 64 Series Resonant Circuit 70 Current Transformer 71 Current transformer primary winding 72 Current transformer secondary winding 220 Current transformer C2A, C2B Bypass capacitor C3 Matching capacitor L1 Reactor

Claims (6)

A first oscillator that outputs AC power having a predetermined first frequency; a second oscillator that outputs AC power having a second frequency higher than the first frequency; and impedances of a predetermined load that are the first and second impedances. A matching unit that matches the output impedance of the two oscillators,
The first oscillator
A first forward conversion unit for converting AC power into DC power, a first smoothing capacitor for smoothing the DC power output from the first forward conversion unit, and DC power smoothed by the first smoothing capacitor A voltage type having a first inverse conversion unit for converting to
The second oscillator is
A second forward conversion unit for converting AC power into DC power, a second smoothing capacitor for smoothing the DC power output from the second forward conversion unit, and the DC power smoothed by the second smoothing capacitor A voltage type with a second inverse conversion unit for converting to
In the power supply apparatus that supplies the AC power output from the first and second oscillators to one inductive load,
The matching unit is:
A reactor through which an alternating current having a first frequency oscillated from the first oscillator flows to the inductive load, and a matching capacitor connected in series to the reactor;
A bypass capacitor through which an alternating current having a second frequency oscillated from the second oscillator flows to the inductive load;
The bypass capacitor is
Preventing the alternating current oscillated from the second oscillator from entering the first oscillator, and
An electric power supply device comprising two capacitors of equal capacity that are electrically connected in series and whose connection point is grounded. A first oscillator that outputs AC power having a predetermined first frequency; a second oscillator that outputs AC power having a second frequency higher than the first frequency; and impedances of a predetermined load that are the first and second impedances. A matching unit that matches the output impedance of the two oscillators,
The first oscillator
A first forward conversion unit for converting AC power into DC power, a first smoothing capacitor for smoothing the DC power output from the first forward conversion unit, and DC power smoothed by the first smoothing capacitor A voltage type having a first inverse conversion unit for converting to
The second oscillator is
A second forward conversion unit for converting AC power into DC power, a second smoothing capacitor for smoothing the DC power output from the second forward conversion unit, and DC power smoothed by the second smoothing capacitor A voltage type with a second inverse conversion unit for converting to
In the power supply apparatus that supplies the AC power output from the first and second oscillators to one inductive load,
The matching unit is:
A reactor through which an alternating current having a first frequency oscillated from the first oscillator flows to the inductive load, and a matching capacitor connected in series to the reactor;
A bypass capacitor through which an alternating current having a second frequency oscillated from the second oscillator flows to the inductive load;
The reactor and the matching capacitor are:
Forming a series resonant circuit that compensates for the power factor of a given inductive load,
The bypass capacitor is
Preventing the alternating current oscillated from the second oscillator from entering the first oscillator, and
An electric power supply device comprising two capacitors of equal capacity that are electrically connected in series and whose connection point is grounded. A transformer having a primary side winding to which the second reverse conversion unit is connected and a secondary side winding to which the first reverse conversion unit is connected;
The secondary winding of the transformer is
The power supply device according to claim 1 or 2, wherein the power supply device is divided into a first part secondary winding and a second part secondary winding. The two capacitors of equal capacity are connected between the first part secondary winding and the second part secondary winding,
4. The power supply device according to claim 3, wherein the other end of each of the two capacitors having the same capacity is connected to the first inverse conversion unit. 5. The reactor and the matching capacitor are:
5. The power supply device according to claim 4, wherein the power supply device is electrically connected in series between the first partial secondary winding and the first inverse conversion unit. The first inverse conversion unit includes a transformer having a primary winding connected via the reactor and the matching capacitor, and a secondary winding connected to the two capacitors having the same capacity;
The power supply device according to any one of claims 1 to 5, wherein the transformer is configured to match an impedance of a predetermined inductive load with an output impedance of the first oscillator.

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