JP6736205B1 - AC output power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC output power supply capable of reducing the number of circuit stages. An AC output power supply according to the present invention includes a rectifier 11 that rectifies an input AC 10 into a DC, and an inverter 12 that converts the DC from the rectifier 11 into an AC having a higher frequency than the input AC 10. The primary side and the secondary side are insulated, and the alternating current converted by the inverter 12 input to the primary side via the circuit 21 having the inductance means L is output to the load 22 connected to the secondary side. And a transformer 13 that operates. [Selection diagram] Figure 2

Description

The present disclosure relates to an AC output power supply that supplies AC power to a load.

An AC output power supply that supplies AC power to a load such as a UV lamp is known (for example, see Patent Document 1). FIG. 1 is a diagram illustrating an AC output power source described in Patent Document 1. In this specification, 100 Hz or less is a low frequency, 100 to 1 kHz is a medium frequency, and 1 kHz or more is a high frequency.

JP, 07-106087, A

The AC output power source as disclosed in Patent Document 1 includes a rectifier 11 for converting commercial AC into DC, an inverter 12 for converting the DC into high-frequency AC, an insulating transformer 13 for boosting the AC, and its output to DC again. A rectifier 14 for conversion and an inverter 15 for converting its direct current into rectangular wave alternating current of a desired frequency are provided. As described above, the conventional AC output power supply has a problem in terms of cost, size, weight, price, and control because it is configured to connect many circuits in multiple stages.

Therefore, it is an object of the present invention to provide an AC output power supply that can reduce the number of circuit stages in order to solve the above problems.

In order to achieve the above object, in the AC output power supply according to the present invention, the rectifier and the inverter are arranged only on the commercial power supply side of the transformer.

Specifically, the AC output power source according to the present invention is
A rectifier that rectifies the input AC into DC,
An inverter for converting direct current from the rectifier to alternating current,
A transformer that is insulated from the primary side and the secondary side, and outputs the alternating current input to the primary side to a load connected to the secondary side,
A circuit in which an inductance means and two capacitors having different capacities are connected in series, the alternating current converted by the inverter is input, and an alternating current generated at both ends of the capacitor having a smaller capacity is applied to the primary side of the transformer. A resonant circuit that is input to
Equipped with.

Further, another AC output power source according to the present invention is
A rectifier that rectifies the input AC into DC,
An inverter for converting direct current from the rectifier to alternating current,
A single winding type transformer that outputs the alternating current input to the primary side to an ungrounded load connected to the secondary side,
A circuit in which an inductance means and two capacitors having different capacities are connected in series, the alternating current converted by the inverter is input, and an alternating current generated at both ends of the capacitor having a smaller capacity is applied to the primary side of the transformer. A resonant circuit that is input to
Equipped with.

This AC output power supply has a resonance circuit between the primary side of the transformer and the inverter, and controls the voltage, current, and power supplied to the load by adjusting the frequency of the AC output by the inverter. Therefore, the present AC output power supply can eliminate the load side rectifier and the inverter, and can improve the cost, size, weight, price, and control aspects. Therefore, the present invention can provide an AC output power supply that can reduce the number of circuit stages.

The present invention can provide an AC output power supply that can reduce the number of circuit stages to be connected.

It is a figure explaining the alternating current output power supply relevant to this invention. It is a figure explaining the alternating current output power supply which concerns on this invention. It is a figure explaining the circuit of the inverter with which the alternating current output power supply concerning this invention is equipped. It is a figure explaining the alternating current output power supply which concerns on this invention. It is a figure explaining the electric current which flows into the load of a constant time, or the waveform applied to a load. It is a figure explaining the waveform which is applied to the electric current which flows through a load at the time of performing PWM or PPM, or a load. It is a figure explaining the electric current which flows into the load at the time of performing PFM, or the waveform applied to a load. It is a figure explaining the alternating current output power supply concerning this invention. It is a figure explaining operation|movement of the alternating current output power supply which concerns on this invention. It is a figure explaining operation|movement of the alternating current output power supply which concerns on this invention. It is a figure explaining the alternating current output power supply which concerns on this invention. It is a figure explaining the threshold which a detector with which the alternating current output power supply concerning the present invention has is provided.

Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In addition, in the present specification and the drawings, components having the same reference numerals indicate the same components.

[Embodiment 1]
FIG. 2 is a diagram illustrating the AC output power supply of this embodiment. This AC output power supply is
A rectifier 11 that rectifies the input AC 10 into DC,
An inverter 12 for converting direct current from the rectifier 11 into alternating current;
A transformer 13 which is insulated from the primary side and the secondary side, and outputs an alternating current input to the primary side to a load 22 connected to the secondary side,
This is a circuit in which the inductance means L and two capacitors (C1, C2) having different capacities are connected in series, and the alternating current converted by the inverter 12 is input to generate an alternating current generated at both ends of the smaller capacitor C2. A resonance circuit 21 input to the primary side of the transformer 13,
Equipped with.

The alternating current 10 is a commercial power supply of 50 Hz and 100 V, for example. The rectifier 11 converts AC 10 into DC and outputs the DC to the inverter 12. The inverter 12 converts direct current into alternating current and outputs it. FIG. 3 is a diagram illustrating a circuit of the inverter 12. The inverter 12 is bridge-connected with four switches (SW A to D), and can switch from direct current to alternating current by turning on or off these switches at a predetermined timing.

A lamp load such as a UV lamp is preferably driven by alternating current rather than direct current in order to avoid wear of electrodes. And if the AC waveform continues to be at zero volt (zero amperes), the lamp may go out (light off). To prevent this, the AC waveform with zero cross should be square wave, trapezoidal wave, triangular wave, or sine wave. Is said to be good. The inverter 12 of FIG. 3 is connected to the circuit 21 having the inductance means L and can easily form an alternating current by driving four switches (SW A to D).

Further, when the UV lamp of the load 22 is ground-faulted, or when the resistance to ground is low, it is necessary to insulate the commercial power source 10 from the alternating current 19 that outputs. Therefore, the transformer 13 is a multi-winding transformer. If the UV lamp of the load 22 is sufficiently insulated from the ground (not grounded), the transformer 13 may be a single-winding transformer.

Since the resonance circuit 21 has one inductance means L and two capacitors (C1, C2), it has two resonance frequencies. Then, the values of the inductance means L and the two capacitors (C1, C2) are set in accordance with the load 22, and the frequency of the alternating current output by the inverter 12 is switched to the resonance frequency of the resonance circuit 21 or a frequency near the resonance frequency of the resonance circuit 21. Power corresponding to the operation of 22 can be supplied to the load 22.

The case where the load 22 is a UV lamp will be described below as a specific example. For example, the inductance means L and the two capacitors (C1 and C2) forming the resonance circuit 21 have the following values.
L=1mH
C1=158μF
C2=28nF

(Operation in steady state)
Next, the operation of the inverter 12 when the UV lamp is turned on and a certain time has passed and the steady state (at the rated time) is reached will be described. The inverter 12 is characterized by switching by the converted alternating current so that the capacitor C1 having a larger capacitance and the inductance means L are brought into a resonance state. Specifically, the inverter 12 is switched so that the frequency fs of the converted alternating current becomes the resonance frequency (first resonance frequency) fr ₁ of the capacitor C1 having a larger capacitance and the inductance means L ₁ or a frequency in the vicinity thereof. To do. In the case of this example, the first resonance frequency fr ₁ is 400 Hz.

The "near-resonance frequency" means the following (the same applies in the following description).
In an actual AC output power supply, the resonance frequency is calculated based on the design values of the capacitors C1, C2 and the inductance means L to control the operation of the inverter 12. However, the actual capacitance of the capacitor and the actual inductance of the inductance means may deviate from the designed values due to manufacturing errors or the like. For example, the error is 0 to ±20% for a capacitor and 0 to ±15% for an inductance means. Furthermore, the resonance circuit 21 itself and the transformer 13 also have capacitance and inductance components. For this reason, the resonance frequency calculated from the design value does not always match the resonance point (resonance frequency fr ₁ ) of the entire device, and is therefore expressed as “a frequency near the resonance frequency”.
Alternatively, the AC output power supply may be operated in advance to measure the resonance point, and the operation of the inverter 12 may be controlled at that frequency.

When the inverter 12 outputs an alternating current of frequency fs=400 Hz, the inductance means L and the two capacitors (C1, C2) have the following impedances.
Inductance means L:
ZL=jωL=j2πfs1×L=j2π×400 Hz×1 mH=j2.5Ω
Capacitor C1:
ZC1=1/(jωC1)=1/(j2π×400 Hz×158 μF)=−j2.5Ω
Capacitor C2:
ZC2=1/(jωC2)=1/(j2π×400 Hz×28 nF)=−j14 kΩ
At this time, the inductance means L and the capacitor C1 form an ideal series resonance circuit (Zr=0Ω), and this AC output power supply becomes the equivalent circuit of FIG.
Since the impedance of the capacitor C2 is as high as 14 kΩ, which is a negligible value, it does not participate in the steady-state operation.

FIG. 5 is a diagram illustrating a current flowing through the load 22 in a steady state or a waveform applied to the load 22. The waveform at the time of rating is a sine wave waveform as shown in FIG. 5 because it is in a resonance state.

(At light load)
When the power to the load side may be smaller than that in the steady state such as when the UV lamp is off, the inverter 12 performs PWM (pulse width control), PPM (pulse phase shift control), or PFM (pulse frequency control). FIG. 6 is a diagram illustrating the waveform of the current flowing through the load 22 or the voltage applied to the load 22 when PWM or PPM is performed. The switching frequency fs of the inverter 12 remains fr ₁ , but the time to which the current flows through the load 22 or the time when the voltage is applied to the load 22 is adjusted to reduce the power to the load 22. For example, as shown in FIG. 6, the current flowing through the load 22 or the voltage applied to the load 22 is temporarily forced to zero by switching. FIG. 7 is a diagram illustrating a current flowing through the load 22 or a waveform applied to the load 22 when the PFM is performed. For example, when fs>fr _{1 in the} PFM, the impedance of the resonance circuit 21 rises, so that the amplitude becomes lower than when fs=fr ₁ , and the power to the load 22 decreases.

(Operation at startup)
Next, the operation of the inverter 12 when turning on the UV lamp will be described. The inverter 12 is characterized by performing a start-up operation in which the converted alternating current causes the capacitor C2 having a smaller capacity and the inductance means L to switch to a resonance state. Specifically, the inverter 12 performs a start-up operation in which the converted frequency fs of the alternating current is switched to the resonance frequency fr ₂ of the capacitor C 2 and the inductance means L, which have smaller capacities, or a frequency near the resonance frequency fr ₂ . In the case of this example, the second resonance frequency fr ₂ is 30 kHz.

When the inverter 12 outputs an alternating current having a frequency fs=30 kHz, the inductance means L and the two capacitors (C1, C2) have the following impedances.
Inductance means L:
ZL=jωL=j2πfs1×L=j2π×30 kHz×1 mH=j188Ω
Capacitor C1:
ZC1=1/(jωC1)=1/(j2π×30 kHz×158 μF)=−j34 mΩ
Capacitor C2:
ZC2=1/(jωC2)=1/(j2π×30 kHz×28 nF)=−j188Ω
At this time, the impedance of the capacitor C1 is very small compared to the other impedances and can be ignored. Therefore, the inductance means L and the capacitor C2 are parallel resonance circuits (Zr=∞Ω) when viewed from the load side, and the AC output power supply of FIG. It becomes the equivalent circuit of. In this case, the voltage of the capacitor C2 rises up to about twice the output voltage of the inverter 12.

When the UV lamp is cold, a higher voltage is required to turn on the UV lamp (ignition=ignition) than in the steady state. For example, when an output voltage of 800V is required on the secondary side of the transformer 13 during steady state, 1500V is required during lighting. This AC output power supply causes the inverter 12 to output AC with a frequency fs=30 kHz when the UV lamp is turned on, thereby increasing the output voltage of the inverter 12 or changing the ignition ratio of the UV lamp without changing the winding ratio of the transformer 13. Obtainable.

[Embodiment 2]
Phase control by THY (thyristor) is usually adopted for a power supply of a commercial frequency (low frequency 50 or 60 Hz). THY has high resistance and is not easily damaged, but it has a characteristic that it cannot be turned off while current is flowing, and is not suitable for instantaneous transient response. Therefore, in the inverter 12 of the present embodiment, the switching element is configured by an insulated gate bipolar transistor (IGBT) or a field effect transistor (FET) instead of THY. The instantaneous transient response of the AC output power supply according to this embodiment will be described with reference to FIGS. 9 and 10. 9A and 9B, FIG. 9A is a circuit diagram, FIG. 9B is a voltage waveform applied to the load, and FIG. 9C is a current waveform on the secondary side of the transformer.

[1] Load Short Circuit FIG. 9 is a diagram for explaining the operation when the impedance of the load sharply decreases (during load short circuit). When a load short circuit occurs, the applied voltage of the load 22 decreases or the secondary side current of the transformer 13 increases. When a detector or the like detects LV (low voltage) or OC (overcurrent), the operation of the inverter 12 must be stopped in order to reduce damage to the load 22. Here, when the switching element of the inverter 12 is composed of THY as in the conventional case, the switching element operates until the current becomes zero, and the current continues to flow to the load 22 for a maximum of half cycle. (FIG. 9(C)). On the other hand, when the switching element of the inverter 12 is composed of the IGBT or the FET as in the present embodiment, the switching element can be stopped at high speed after detecting LV or OC. Therefore, the AC output power supply of the present embodiment can reduce the damage to the load 22 without causing the current to continue to flow to the load 22 for a maximum of a half cycle unlike THY.

[2] Load release FIG. 10 is a diagram for explaining the operation when the load impedance sharply rises (when the load is released) such as when the UV lamp goes out. When the load is released, the applied voltage of the load 22 increases or the secondary side current of the transformer 13 decreases. When a detector or the like detects OV (overvoltage) or LC (low current), the operation of the inverter 12 must be stopped in order to reduce damage to the load 22. Here, when the switching element of the inverter 12 is composed of THY as in the conventional case, the switching element operates until the voltage becomes zero, and the voltage is applied to the load 22 for a maximum of half cycle. (FIG. 10(B)). On the other hand, when the switching element of the inverter 12 is composed of the IGBT or the FET as in the present embodiment, the switching element can be stopped at high speed after detecting OV or LC. Therefore, the AC output power supply of the present embodiment can reduce the damage to the load 22 without the voltage being continuously applied to the load 22 for a maximum half cycle like THY.

(Embodiment 3)
FIG. 11: is a figure explaining the alternating current output power supply of this embodiment. This AC output power supply is the same as the AC output power supply of FIG.
A detector 31 that detects the output voltage of the inverter 12, the voltage of the secondary side of the transformer 13, the current of the primary side of the transformer 13, or the current of the secondary side of the transformer 13 as a determination value;
A control circuit 32 that causes the inverter 12 to perform the starting operation when the determination value reaches a first threshold value, and stops the switching of the inverter 12 when the determination value reaches a second threshold value;
Is further provided.

When the UV lamp is extinguished, the load impedance sharply rises from the state of full ignition, so the load applied voltage sharply rises as shown in FIG. 10(B). At this time, even if the detector 31 detects an increase in the applied voltage to the load, it is preferable that the control circuit 32 does not immediately stop the inverter 12 as an abnormal voltage alarm due to an error but retry as follows.

The control circuit 32 has a two-step threshold value for the detection value of the detector 31 (load applied voltage in this example) as shown in FIG. When the load application voltage rises from the rated voltage and becomes equal to or higher than the first threshold value (OV1) and equal to or lower than the second threshold value (OV2), the control circuit 32 immediately causes the inverter 12 to perform an error stop as an abnormal voltage alarm. Rather, the comparator 12 or the like suppresses the increase of the load applied voltage at high speed (limit control), and causes the inverter 12 to perform a retry (re-ignition) operation. Here, the retry operation is the "operation at startup" described in the first embodiment.

Further, when the load applied voltage rises from the rated voltage and becomes equal to or higher than the second threshold value (OV2), the control circuit 32 immediately stops the inverter 12 as described in the second embodiment.
For example, OV1 can be set to 105% of the rated Vn, and OV2 can be set to 110% of the rated value.

In the present embodiment, the target detected by the detector 31 is the load applied voltage (voltage on the secondary side of the transformer 13), but the output voltage of the inverter 12, the current on the primary side of the transformer 13, or the voltage on the secondary side of the transformer 13. The secondary side current may be used as the detected value.

10: Input AC 11: Rectifier 12: Inverter 13: Transformer 14: Rectifier 15: Inverter 19: Output AC 21: Resonance circuit 22: Load 24: Power output terminal 31: Detector 32: Control circuit

Claims (6)

A rectifier that rectifies the input AC into DC,
An inverter that converts direct current from the rectifier to alternating current,
A transformer for outputting the load connected to the AC input to the primary side to the secondary side,
A circuit in which an inductance means and two capacitors having different capacities are connected in series, the alternating current converted by the inverter is input, and an alternating current generated at both ends of the capacitor having the smaller capacity is generated on the primary side of the transformer. A resonant circuit that is input to
Equipped with
The inverter is an alternating current obtained by the conversion, AC output power and said inductance means and said capacitor towards larger capacity you characterized in that switching to a resonant state. The AC output according to claim 1 , wherein the inverter adjusts a time during which a voltage is applied to a load via the transformer or a time during which a current flows through the load by pulse width control or pulse phase shift control. Power supply. A rectifier that rectifies the input AC into DC,
An inverter that converts direct current from the rectifier to alternating current,
A transformer for outputting the load connected to the AC input to the primary side to the secondary side,
A circuit in which an inductance means and two capacitors having different capacities are connected in series, the alternating current converted by the inverter is input, and an alternating current generated at both ends of the capacitor having the smaller capacity is generated on the primary side of the transformer. A resonant circuit that is input to
Equipped with
The inverter switches so that the frequency of the converted alternating current deviates from the resonance frequency of the capacitor having a larger capacity and the inductance means, and the power to the load has a large frequency of the converted alternating current. An AC output power source, which is lower than the power to the load when the resonance frequency of one of the capacitors and the inductance means is the same . A rectifier that rectifies the input AC into DC,
An inverter that converts direct current from the rectifier to alternating current,
A transformer for outputting the load connected to the AC input to the primary side to the secondary side,
A circuit in which an inductance means and two capacitors having different capacities are connected in series, the alternating current converted by the inverter is input, and an alternating current generated at both ends of the capacitor having the smaller capacity is generated on the primary side of the transformer. A resonant circuit that is input to
Equipped with
The AC output power supply is characterized in that the inverter performs a start-up operation by switching the capacitor having a smaller capacity and the inductance means by the converted AC so as to be in a resonance state . The inverter, AC output power according to any one of claims 1 to 4, characterized in that the switching element is constituted by an insulated gate bipolar transistor or a field effect transistor. A detector that detects the output voltage of the inverter, the voltage of the secondary side of the transformer, the current of the primary side of the transformer, or the current of the secondary side of the transformer as a determination value,
A control circuit for causing the inverter to perform the starting operation when the determination value reaches a first threshold value, and stopping switching for the inverter when the determination value reaches a second threshold value;
The AC output power supply according to claim 4, further comprising: or claim 5 quoting claim 4 .

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