JPH08275538A - Power supply - Google Patents

Abstract

PURPOSE: To obtain a power supply for improving harmonic distortion of input current through the high frequency operation at an inverter section comprising an LC circuit and an oscillation circuit including a load in which a stabilized power is fed to the load by suppressing ripples of load current for such operation as the waveform of load current contains ripples substantially similar indirectly to the high frequency ripples of input voltage. CONSTITUTION: The power supply comprises a main circuit 1 including a rectifier section 11, an inverter section 12 and a load 13, and a control circuit 2 including a load current ripple detecting section 21 for detecting increase/ decrease of load current at a frequency twice as high as the AC power supply frequency, a section 23 for controlling the operating frequency of a switching element at the inverter section 12, and a section 22 for switching the frequency such that the operating frequency of load current is higher at a projecting part than at a recessed part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having improved input current distortion from an AC power supply.
It is used for an electronic ballast of a discharge lamp lighting device.

[0002]

2. Description of the Related Art FIG. 17 is a circuit diagram of a conventional inverter device (Japanese Patent Application No. 3-186251). The circuit configuration will be described below. The AC power supply Vs is connected to the AC input terminal of the full-wave rectifier DB through a filter circuit including a transformer L ₃ and capacitors C ₅ and C ₆ .
The smoothing capacitor C ₁ is connected to the DC output terminal of the full-wave rectifier DB through the diode D ₃ . The smoothing capacitor C ₁ is connected to a series circuit of switching elements Q ₁ and Q ₂ . Diodes D ₁ and D ₂ are connected in antiparallel to the switching elements Q ₁ and Q ₂ , respectively. One end of the capacitor C ₃ is connected to the connection point of the diode D ₃ and the rectifier DB, and one end of the inductor L ₁ is connected to the connection point of the switching elements Q ₁ and Q ₂ . The power supply side terminal of the filament of the discharge lamp La is connected between the other end of the capacitor C _{3 and} the other end of the inductor L ₁ . A capacitor C ₂ is connected in parallel between the non-power supply side terminals of the filament of the discharge lamp La.
A capacitor C ₄ is connected in parallel with both ends of the diode D ₃ .

The operation of the above circuit will be described below.
First, the operation of the inverter will be described. The inverter has switching elements Q ₁ , Q ₂ and a diode D ₁ ,
It is composed of D ₂ , an inductor L ₁ , capacitors C ₂ , C ₃ and a discharge lamp La. Switching elements Q ₁ , Q ₂
Alternately turn on and off at a high speed to convert the DC voltage of the smoothing capacitor C ₁ into a high frequency and turn on the discharge lamp La at a high frequency. The capacitor C ₂ constitutes a preheating current conducting path of the filament of the discharge lamp La, and the inductor L
_It also functions as a resonance capacitor with ₁ . Capacitor C ₃
Is a coupling capacitor for cutting the DC component.

In the above circuit, the switching element Q ₂
When is turned on, the capacitors C ₁ to C ₄ ,
After passing through the capacitor C ₃ , the discharge lamp La and the capacitor C ₂ , the inductor L ₁ , and the switching element Q ₂ , the capacitor C 3
_The current flows in the route returning to ₁ . At this time, the voltages appearing in the respective elements have a relationship of V ₁ ≈V ₄ + V ₃ + V ₂ + V ₆ . What is connected to the output terminal of the full-wave rectifier DB is a series circuit of the capacitor C ₃ , the discharge lamp La and the capacitor C ₂ , and the inductor L _1. Therefore, | Vin |> V ₃
When + V ₂ + V ₆ ≈V ₁ −V ₄ is established, the capacitor C ₃ , the discharge lamp La and the capacitor C from the full-wave rectifier DB.
₂ , a current flows through a path returning to the full-wave rectifier DB through the inductor ₂ , the inductor L ₁ and the switching element Q ₂ . That results in the capacitor C ₄ inserted between the output terminal and the capacitor C ₁ of the full-wave rectifier DB to bear the voltage difference between the voltage V ₁ of the rectified output voltage and capacitor C ₁ of the full-wave rectifier DB, input voltage | Vin | is also lower than the voltage V ₁ of the capacitor C _1, as shown in FIG. 18, flows the input current Iin. Therefore, the input power factor becomes high. Further, the input current waveform obtained by removing the high frequency component by the filter circuit including the capacitors C ₅ and C ₆ and the transformer L ₃ is
The waveform can be close to a sine wave with few harmonic components.

[0005]

In the above-mentioned conventional example, the capacitor C ₄ is used by utilizing the high frequency operation of the inverter by turning on / off the switching elements Q ₁ and Q _2.
It is charged and discharged to improve the distortion of input current. Therefore, in order to make the input current substantially sinusoidal, the voltage V ₁ of the smoothing capacitor C ₁ is substantially constant, and therefore the capacitor C _1
The voltage borne by ₄ changes according to the pulsating current of the input voltage. Then, the resonance state on the inverter side also changes,
As a result, the current flowing through the load changes in accordance with the input pulsating current, resulting in unevenness. In the conventional example, the current of the discharge lamp La which is the load is as shown in FIG. 19, and the input voltage | Vin
Speaking of |, there is a problem that it shows an inversely similar ripple waveform and CF (crest factor) becomes worse.

[0006]

FIG. 1 is a block diagram showing the basic configuration of the present invention. The main circuit 1 includes a rectifying unit 11, an inverter unit 12, and a load 13. The control circuit 2 also includes a load current ripple detection unit 21, a frequency switching signal output unit 22, and a frequency control unit 23. In order to recognize the load current ripple, the load current ripple detector 21 mainly detects a detection signal that is substantially anti-similar to the load current ripple or a detection signal that is substantially similar to the load current ripple, as shown in FIG. It is obtained from a predetermined detection point in the circuit 1. The frequency switching signal output unit 22 receives the load current ripple detection signal from the load current ripple detection unit 21 and outputs the frequency switching signal to the frequency control unit 23. The frequency control unit 23 receiving the output controls the load current so that the convex portion has a higher oscillation frequency than the concave portion. Frequency switching may be performed in any number of steps or may be continuous.

[0007]

According to the present invention, as described above, the main circuit is provided with the detection points showing a similar or anti-similar shape to the ripple of the load current, and the unevenness of the load current is detected from the detection signal. Since the control means is provided to switch the operating frequency so that the operating frequency of the convex portion becomes higher than the operating frequency of the concave portion, uneven ripples of the load current can be suppressed and a stable output can be supplied.

[0008]

FIG. 3 shows the basic construction of the first embodiment of the present invention.
FIG. 4 is a block circuit diagram, and FIG. 4 is a specific circuit diagram thereof.
The main circuit uses the same principle as the conventional example shown in FIG.
It is an inverter circuit that does good. DC of full wave rectifier DB
Output terminal and smoothing capacitor C₁Between the Impeda
A sense element Z (including a diode) is inserted. Figure
In the concrete circuit shown in FIG. 4, the impedance element Z of the main circuit is used.
In the same manner as the conventional example shown in FIG. 17,
Capacitor C_FourAnd diode D₃Has been inserted
It In addition, the ripple of the load current (see Fig. 19 (b))
In order to suppress the control, in the loop where the load current flows
Transformer T for detection₁The load current ripple
Detect the state. Transformer T for detection₁For half-wave rectification
Diode D₈The anode of is connected to the dio
Code D₈Capacitor C for high frequency cutting on the cathode of
_TenAnd discharge resistor R₉And comparator CP₁The minor
Input terminal is connected. Capacitor C_TenCapacity
Is a transformer T for detection ₁To diode D₈Through
The load is not large enough to smooth the current flowing in
The increase and decrease of the ripple of the current is similar to that of the capacitor C_Ten
Appearing at the potential of the frequency switching signal output unit 22
CP₁Input to the negative input terminal of. Compare
Data CP₁The positive side input terminal of the
The reference potential for determining the
Is changed from concave to convex, the comparator CP₁
The negative input terminal level of is the positive input terminal level
Beyond the comparator CP₁Output is low level
Become.

Then, the oscillator IC ₁ of the frequency control unit 23
The intersection point of the resistors R ₅ and R ₆ connected to the 6th terminal of (NEC μPC1094) is dropped to the low level. Oscillator IC ₁ (NEC Ltd. MyuPC1094) is a connected between the sixth terminal and the ground resistance, the oscillation frequency is determined by capacitor C ₇ connected between the fifth terminal and ground, the output of the comparator CP ₁ Becomes low level, the resistor R ₆ is short-circuited, the resistance value connected to the 6th terminal is lowered, and the oscillation frequency is increased. as a result,
Since the operating frequency increases at the convex portion of the load current ripple, the output of the inverter (LC resonance) is weakened, the protrusion of the convex portion is suppressed, and the ripple of the entire load current is suppressed. Note that the oscillator IC ₁ (NEC μPC109
The drive circuit IC ₂ (IR2111) connected to the output terminal of the 10th pin of 4) is a high breakdown voltage gate driver for directly driving the switching elements Q ₁ and Q ₂ .

FIG. 5 is a modification of the first embodiment, in which the load current ripple detector 21 utilizes the detection of the input voltage | Vin |. As described above, in the present inverter circuit, the load current ripple is affected by the power supply voltage, and exhibits a ripple that is substantially inversely similar to the ripple of the input voltage | Vin |. That is, the convex portion of the load current corresponds to the valley portion of the ripple of the input voltage | Vin |, and the concave portion of the load current corresponds to the peak portion of the ripple of the input voltage | Vin |. Utilizing this, input voltage for detecting load current ripple |
By using Vin | detection, the load current ripple detection unit 21 can be formed by a simple circuit without using the transformer T ₁ , the diode D ₈ , the capacitor C _10, etc. as shown in FIG.
Has been realized. In addition, it is not affected by changes in the load state or output changes such as dimming. However, detection can detect signals in contrary to the case of FIG. 4, since a load current ripple and inverse similar shape, is input to the positive input terminal of the comparator CP _1. The reference potential is input to the negative input terminal of the comparator CP ₁ , and the reference potential becomes higher in the valley portion of the input voltage | Vin |
The output of ₁ becomes Low level and the oscillation frequency rises,
The load current ripple is suppressed. An operation time chart of the circuits of FIGS. 4 and 5 is shown in FIG. In the figure, (a) is FIG.
5B shows the operation of the circuit of FIG. 5, and FIG. 5B shows the operation of the circuit of FIG. Further, (c) is the output of the comparator CP ₁ , (d)
Indicates the operating frequency, and (e) indicates the load current.

In the present circuit system, as described above, the potential borne by the capacitor C ₄ changes according to the input voltage | Vin |. Therefore, the resonance condition on the inverter side also changes, and as shown in FIG. 7 (a), the peak operation of the input voltage | Vin | is slow-phase operation, but the valley operation proceeds as shown in FIG. 7 (b). It may become a phase operation. Further, even if the phase delay operation is performed in a steady state, the phase may advance toward the phase advance direction when the power supply voltage decreases, and the resonance near the valley of the input voltage | Vin | may be in the phase advance state. The present invention has the effect of increasing the oscillation frequency at the valley of the input voltage | Vin | and shifting the phase in the lagging direction to avoid such a phase advance operation near the valley of the input voltage | Vin |. There is also.

FIG. 8 shows a second embodiment of the present invention, FIG. 9 shows a third embodiment of the present invention, and FIG. 10 shows a fourth embodiment of the present invention. Specific examples of the main circuit of each embodiment include US Pat. No. 4,949,013 and US Pat. No. 5,31, respectively.
3,142, JP-A-5-9918 and the like.
In these circuit systems, in order to improve the input distortion by utilizing the high frequency operation of the inverter, the effect of the input voltage ripple appears in the inverter section.

The main circuit in the second and third embodiments has a structure in which an impedance element Z is connected between the power source and a part of the LC oscillation loop of the inverter. This impedance element Z is similar to the capacitor C _{4 of the} conventional example in that the input voltage | Vin | and the voltage V of the smoothing capacitor C ₁
The potential difference of ₁ is borne and the input current is made to flow even at | Vin | <V ₁ to improve the input distortion. In the second embodiment, the output terminal of the full-wave rectifier DB, that is, the impedance element Z is connected after power supply rectification, whereas in the third embodiment, the impedance element Z is connected before power supply rectification.
Is connected. Further, the main circuit in the fourth embodiment is a high frequency superposition circuit in which a loop for returning the high frequency voltage generated on the inverter side to the power supply unit by using a transformer or the like is added.

In the power supply devices for these main circuits, if the input current is controlled so as to have a substantially sinusoidal wave, the current flowing through the connected load will have an input voltage | Vin | as shown in FIG.
And shows an uneven ripple of an anti-similarity. Therefore, as shown in FIG. 8, FIG. 9, and FIG. 10, a load current ripple detection unit 21 based on detection from the main circuit is provided, and from the detection result, a signal for switching the frequency from the convex portion to the concave portion of the load current ripple is frequency-switched. Output from the signal output unit 22, and according to the signal, the frequency control unit 23 controls the oscillation frequency of the convex portion to be higher than the oscillation frequency of the concave portion, whereby the load ripple is suppressed and a stable output waveform is obtained. . Further, in the second and third embodiments, the phase advancing operation at the valley of the input voltage | Vin | becomes a problem as in the first embodiment, but the convex portion of the load current, that is, the input voltage | Vi
By controlling the frequency to be high in the valley portion of n |, there is also an effect of avoiding the phase advance operation in the valley portion.

FIG. 11 shows a fifth embodiment of the present invention. Real
The main circuit of the embodiment is a diode D in the conventional example.₆, D₇And i
Inductor L₂And capacitor C₉Add and fill in the valley
(Partial smoothing) circuit is configured. Where the valley filling circuit
14 will be briefly described.
Smoothing capacitor C₁Is the switching element Q₁Is on
Then, from the positive side output terminal of the rectifier DB to the diode D
₃, D₆, Inductor L ₂Be charged through. But
Inductor L in the charging loop₂Because there is
Indexer C₁Smoothing potential V₁Is the input voltage | Vin |
Voltage Vp to inductor L₂Voltage drop Vx at
Subtracted voltage V₁= Vp-Vx and smoothed. Obedience
Vp> V₁And, | Vin |> V₁At
Is the switching element Q₁, Q₂Voltage applied to both ends of
Pressure is | Vin | and | Vin | <V₁At
Is the switching element Q₁, Q₂The voltage across is the smoothed voltage
V₁Therefore, the power source becomes a buried valley power source as shown in Fig. 12 (b).
It Also, smoothing capacitor C₁In the charging loop of
L₂Exists, so the inrush current at power-on
There is also an effect that can be suppressed.

As a result, the power source of the inverter is as shown in FIG.
As shown in (b), the load current becomes as shown in FIG. 12 when combined with the circuit system of the conventional example in which the power source becomes a valley power source and the load current shows a ripple similar to the ripple of the input voltage | Vin |.
As shown in (c), the ripple is suppressed as compared with the conventional example. An operation time chart when the control of the present invention is applied to this main circuit is shown in FIG. In the figure, a (a) is positive and the voltage of the negative input terminal of the comparator CP _1, (b) the output of the comparator CP _1, (c) operating frequency, (d) the load current.

In this embodiment, the capacitor C ₉ shown in FIG. 11 is used as a detection unit for detecting the load current ripple.
Of both ends, that is, the voltage waveform of the valley power supply is used.
The relationship between the valley-filled power supply ripple and the load current ripple is
As shown in FIG. 12, the constant potential portion of the valley portion of the valley-filled power source is on the convex portion of the load current ripple, so the frequency at that portion is increased. Therefore, in the load current ripple detector 21, the potentials across the capacitor C ₉ are divided by the resistors R ₁ and R ₂ , and the voltage dividing point Q is divided by the comparator CP.
Connect to the positive input terminal of ₁ . Comparator CP ₁
The potential of the negative side input terminal of the resistors R ₃ and R is set so that the output of the comparator CP ₁ is inverted in the valley portion of the valley power source.
_The reference potential is set by ₄ and the comparator CP ₁
When the output of is changed from the high level to the low level, the operating frequency is increased and the output of the load current is controlled so as to be suppressed. As a result, the load current becomes as shown in FIG. 13D, and stable operation with less ripple can be realized. Further, as described in the embodiment, in the main circuit system, there is a phase advance problem in the valley portion of the input voltage | Vin | at the time of power supply drop. However, the main circuit of the present embodiment is Since the power supply of the inverter is low at the valley of the input voltage | Vin | from the steady state, the phase advance mode is more likely to occur. However, by applying the control of the present invention, the operating frequency at the valley portion of the input voltage | Vin | becomes high, and the phase advance operation can be avoided.

The valley filling circuit is the sixth one shown in FIG.
The circuit 14a of the embodiment, the circuit 14b of the seventh embodiment shown in FIG. 15, the circuit 14c of the eighth embodiment shown in FIG. 16 and the like can be mentioned, but any circuit may be used as long as it generates a valley filling voltage. By adding these valley filling circuits to the first to fourth embodiments, as in the fifth embodiment, as shown in FIG.
(C) shows the ripple waveform of the load current, and the same effect that the ripple of the load current can be suppressed by adding the control of the present invention can be obtained. The sixth embodiment is the main circuit of the second embodiment, the seventh embodiment is the main circuit of the third embodiment, the eighth embodiment is the fourth embodiment, and a valley filling circuit is added. However, any combination of each main circuit and each valley filling circuit may be used.

[0019]

According to the present invention, the harmonic distortion of the input current can be improved by utilizing the high frequency operation of the inverter section having the oscillating circuit including the LC circuit and the load. For the operation that shows a ripple waveform that is almost anti-similar to the commercial frequency ripple of the input voltage, the ripple of the load current is detected so that the operating frequency in the convex portion of the load current becomes higher than the operating frequency in the concave portion.
Since the frequency is switched, a stable output can be supplied to the load. Therefore, flicker can be reduced when an illumination load such as a discharge lamp is connected. The load current ripple can be further reduced by providing a partial smoothing circuit instead of the smoothing capacitor on the output side of the rectifying unit.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a basic configuration of the present invention.

FIG. 2 is an operation waveform diagram of the present invention.

FIG. 3 is a block circuit diagram showing the basic configuration of the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a specific configuration of the first exemplary embodiment of the present invention.

FIG. 5 is a circuit diagram showing a modification of the first embodiment of the present invention.

FIG. 6 is an operation waveform diagram in an AC cycle according to the first embodiment of the present invention.

FIG. 7 is an operation waveform diagram in a switching cycle according to the first embodiment of this invention.

FIG. 8 is a circuit diagram showing a second embodiment of the present invention.

FIG. 9 is a circuit diagram showing a third embodiment of the present invention.

FIG. 10 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 11 is a circuit diagram showing a fifth embodiment of the present invention.

FIG. 12 is an operation waveform diagram before ripple suppression in the fifth embodiment of the present invention.

FIG. 13 is an operation waveform diagram after ripple suppression in the fifth embodiment of the present invention.

FIG. 14 is a circuit diagram showing a sixth embodiment of the present invention.

FIG. 15 is a circuit diagram showing a seventh embodiment of the present invention.

FIG. 16 is a circuit diagram showing an eighth embodiment of the present invention.

FIG. 17 is a circuit diagram of a conventional example.

FIG. 18 is an operation waveform diagram showing an input voltage and an input current of a conventional example.

FIG. 19 is an operation waveform diagram showing a rectified voltage and a load current in a conventional example.

[Explanation of symbols]

 1 Main Circuit 2 Control Circuit 11 Rectifier 12 Inverter 13 Load 21 Load Current Ripple Detector 22 Frequency Switching Signal Output 23 Frequency Controller

Claims (8)

[Claims] 1. A rectification unit for full-wave rectifying an AC power supply, an inverter unit for converting the output of the rectification unit into a high frequency, a load connected to the output of the inverter unit, and an ON / OFF switching element of the inverter unit. In a power supply device having a control unit that obtains an AC input current that is substantially similar to an AC voltage and that obtains a load current that increases and decreases in the opposite direction to the AC voltage, an increase / decrease in load current with respect to twice the frequency of the AC power supply is detected Load current ripple detector, a frequency controller that controls the operating frequency of the switching element of the inverter, and a frequency switching signal that switches the frequency so that the operating frequency in the convex portion of the load current is higher than the operating frequency in the concave portion. A power supply device comprising an output section. 2. The inverter section includes a smoothing capacitor connected to both ends of the rectifying section via impedance elements,
The first and second switching elements connected in series to both ends of the smoothing capacitor, and the LC circuit connected to both ends of at least one of the switching elements and an oscillating circuit including a load are provided. The power supply device according to claim 1, wherein the impedance element is included in a loop of a vibrating circuit including the element. 3. The inverter section includes a smoothing capacitor connected to both ends of the rectifying section via a diode, first and second switching elements connected in series to both ends of the smoothing capacitor, and at least one of the switching elements. The power supply device according to claim 1, further comprising an LC circuit connected to both ends of the element and an oscillating circuit including a load, wherein the diode is included in a loop of the oscillating circuit including the LC circuit, the load, and a switching element. . 4. The inverter unit includes a smoothing capacitor connected to both ends of the rectifying unit, first and second switching elements connected in series to both ends of the smoothing capacitor, and to both ends of at least one of the switching elements. An LC circuit to be connected and a vibrating circuit including a load are provided, an AC power source is connected to a part of the vibrating circuit via an impedance element, and a connection point between the AC power source and the impedance element and the smoothing capacitor. The power supply device according to claim 1, wherein the diodes are connected in a forward direction. 5. The inverter unit includes a smoothing capacitor connected to both ends of the rectifying unit, first and second switching elements connected in series to both ends of the smoothing capacitor, and to both ends of at least one of the switching elements. An LC circuit to be connected and a vibrating circuit including a load are provided, an AC power source is connected to a part of the vibrating circuit via an impedance element, and a connection point between the rectifying unit and the impedance element and the smoothing capacitor. The power supply device according to claim 1, wherein the diodes are connected in a forward direction. 6. The power supply device according to claim 1, wherein smoothing capacitors are provided at both ends of the rectifying unit, and a circuit for returning a part of the output of the inverter unit to the AC input side of the rectifying unit is provided. 7. The power supply device according to claim 2, wherein a partial smoothing circuit is connected instead of the smoothing capacitor. 8. The load current ripple detector is a means for detecting an increase / decrease in load current with respect to a frequency twice as high as that of an AC power source, at a portion showing a substantially similar shape or a substantially reverse similar shape to the rectified output of the rectifier. The power supply device according to claim 1, wherein the power supply device is a power supply device.