JP2795389B2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply having an inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as a power supply device of this type, for example, a configuration shown in FIG. 7 has been known.

In the power supply device shown in FIG. 7, an AC power supply E is connected to a filter circuit 1 composed of an inductor L1 and a capacitor C1, and this filter circuit 1 is connected to an input terminal of a full-wave rectifier circuit 2 composed of a diode bridge. ing. A switching transistor Q1 is connected to an output terminal of the full-wave rectifier circuit 2 via an inductor L2, and a charging capacitor C2 is connected via a diode D1 in a forward polarity.
Are connected. The high-frequency inverter circuit 3 is connected to the charging capacitor C2.

[0004] One end of each filament electrode FLa, FLb of the discharge lamp FL is connected to the output terminal of the high-frequency inverter circuit 3 via a resonance capacitor C4. Further, a starting capacitor C5 is connected between the other ends of the filament electrodes FLa and FLb of the discharge lamp FL.

The high-frequency inverter circuit 3 has a transformer.
A series circuit of a primary winding Tra of the Tr and a switching transistor Q2, a resonance capacitor C6 connected in parallel to the primary winding Tra of the transformer Tr, and a diode D2 connected in parallel to the transistor Q2. And the transformer Tr 1
A series circuit of the secondary winding Tra and the transistor Q2 is connected in parallel to the charging capacitor C2, and the secondary winding Trb of the transformer Tr is used as an output terminal.

Further, a control circuit 4 is connected to the transistor Q1.

When the high-frequency switching operation is performed by the control circuit 4, the energy stored in the inductor L2 by the current supplied from the pulsating voltage rectified by the full-wave rectifier circuit 2 when the transistor Q1 is on is reduced. When the transistor Q1 is turned off, the charge is superimposed on the pulsating voltage and charged into the charging capacitor C2 via the diode D1. Further, the switching operation of the transistor Q1 is performed continuously, so that the charging voltage of the charging capacitor C2 is smoothed. Then, a current having a peak at an envelope corresponding to the pulsating voltage flows through the inductor L2. Since the rectification by the switching becomes a sine wave current in the same phase as the AC voltage of the AC power supply E in the filter circuit 1, the input current does not include a harmonic component and has a high power factor.

The charging voltage of the charging capacitor C2 is:
The power supply for the high frequency inverter circuit 3 and the transistor Q2
Of the transformer Tr, the resonance circuit of the primary winding Tra of the transformer Tr and the resonance capacitor C4 is operated, and the resonance voltage is transmitted to the secondary winding Trb of the transformer Tr.
Supplied to FL. Then, the discharge lamp FL is connected by the capacitor C5.
The filament electrodes FLa and FLb are preheated, and a high voltage generated across the capacitor C5 is applied between the filament electrodes FLa and FLb of the discharge lamp FL, and the discharge lamp FL is turned on.

[0009]

However, in the conventional power supply shown in FIG. 7, since the transistor Q1 is chopper-controlled, the input current contains almost no harmonics. The DC input line rectification is continuously supplied in all sections of the pulsating voltage due to the loss of the load circuit including the electric light FL, so the energy processing amount of each element is large and the element capacity is large, that is, large. And high price.

Further, the control circuit 4 for controlling the switching of the transistor Q1 is provided with a switching transistor 5 so that the DC voltage of the pulsating current, whose instantaneous value constantly changes, is continuously and constantly kept so that no energy is stored in the inductor L2.
Is switched every cycle, so that the control method and configuration are complicated and the size is increased.

Further, since the energy processing for switching the transistor Q1 is continuously performed in all sections of the pulsating DC voltage, the switching loss of the transistor Q1 is large, and the current flowing through the switching is a continuous triangular wave. , The amount of noise generated increases.

Furthermore, since an excessive rush current flows into the charging capacitor C2 when the power is turned on, the capacity of the components connected to the power supply line must be increased as a countermeasure. Have problems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can reduce harmonic components in an input current.
It is an object of the present invention to provide a power supply device capable of reducing the price and simplifying the configuration and reducing the amount of noise generated.

[0014]

According to a first aspect of the present invention, there is provided a power supply device comprising: a rectifier circuit for rectifying an alternating current from an AC power supply; a capacitor connected in parallel to an output terminal of the rectifier circuit; A rectifying element connected in series with forward polarity, and an inverter circuit having a charging circuit having a charging capacitor and an inductor element connected to the rectifying circuit via the rectifying element, and an output of the rectifying circuit is provided. The output frequency of the inverter circuit is changed correspondingly.

According to a second aspect of the present invention, in the power supply unit of the first aspect, the frequency of the inverter circuit is changed only when the output level of the rectifier circuit is lower than the charge level of the charging capacitor.

[0016]

According to the first aspect of the present invention, the rectifier circuit rectifies the AC from the AC power supply, and charges the capacitor with the pulsating current rectified by the rectifier circuit. Then, power is supplied to the inverter circuit via the rectifying element, and the inverter circuit oscillates. The oscillation of the inverter circuit changes the output frequency corresponding to the output of the rectifier circuit. That is, depending on the voltage input from the rectifier circuit, the harmonic component increases, so that the frequency is changed to suppress the harmonic component and make the voltage waveform and the current waveform have the same phase.

According to a second aspect of the present invention, when the output level of the rectifier circuit is higher than the charge level of the charging capacitor, the output power is not changed and the frequency control is performed. Is prevented from being disabled, and depending on the voltage input from the rectifier circuit, harmonics are likely to be generated, so the output frequency is changed to suppress the generation of harmonics.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply device of the present invention will be described below with reference to a discharge lamp lighting device shown in the drawings.

As shown in FIG. 1, an input terminal of a full-wave rectifier circuit 11 composed of a diode bridge is connected to a commercial AC power supply E via an inductor L11.
A first capacitor C11 is connected in parallel to an output terminal of the first capacitor C1 via a diode D11 as a rectifier. The second capacitor C12 is connected in parallel to the first capacitor C11 via a diode D12 as a rectifying element with a forward polarity.

Further, a charging circuit 12 composed of a series circuit of a diode D13 of opposite polarity, an inductance element L12 and a charging capacitor C13 is connected in parallel to the second capacitor C12.

A single-type high-frequency inverter circuit 16 is connected to the second capacitor C12. This high-frequency inverter circuit 16 has a series circuit of a primary winding Tr11a of a transformer Tr11 and a switching transistor Q11.
A resonance capacitor C14 is connected to the primary winding Tr11a of the transformer Tr11.
Are connected in parallel, and a circulating diode D14 is connected in parallel to the transistor Q11. And transformer Tr
A series circuit of an eleventh primary winding Tr11a and a transistor Q11 is connected in parallel to a second capacitor C12. Also,
A control circuit 17 is connected to the transistor Q11 so that the transistor Q11 performs a high-frequency switching operation.

A voltage detection circuit 18 connected between the output terminals of the full-wave rectifier circuit 11 and a current detection circuit 19 connected to one end of the output terminal of the full-wave rectifier circuit 11 are connected to the control circuit 17. Have been.

Further, one end of each filament electrode FLa, FLb of the discharge lamp FL is connected to a secondary winding Tr11b of the transformer Tr11 via a capacitor C15. A starting capacitor C16 is connected between the other ends of the filament electrodes FLa and FLb of the discharge lamp FL.

Further, a tertiary winding Tr11 is connected to the transformer Tr11.
The tertiary winding Tr11c is connected in parallel to a charging capacitor C13 via a diode D15.

The second capacitor C12, the diode
D13, inductance element L12, charging capacitor C13
, Tertiary winding Tr11c of transformer Tr11 and diode D15
The circuit consisting of forms the oscillation circuit 21.

Next, the operation of the above embodiment will be described.

First, during operation, the voltage of the commercial AC power supply E is rectified by the full-wave rectifier circuit 11 and the diode D11, and a voltage Vc11 shown in FIG. 2A is generated between both ends of the first capacitor C11. I do.

Further, in order to make the explanation easy to understand, the case where the inductor L12 is not provided and the capacity of the second capacitor C12 is made large enough so as not to hinder the operation of the high-frequency inverter circuit 16. Thus, a voltage Vc12a shown in FIG. 2B is generated between both ends of the second capacitor C12.

When the high-frequency inverter circuit 16 is oscillating by the switching operation of the transistor Q11, the primary winding Tr11a of the transformer Tr11 and the primary winding of the transformer Tr11 by the resonance action of the resonance capacitor C14.
A high-frequency voltage is generated in Tr11a, and a high-frequency voltage corresponding to the turn ratio with the primary winding Tr11a is also induced in the tertiary winding Tr11c. This voltage charges the charging capacitor C13 via the diode D15. Also, charging capacitor C1
The charging voltage Vc6 of FIG. 3 is lower than the peak value Vpeak of the pulsating voltage, which is the voltage Vc12a between both ends of the second capacitor C12, as shown in FIG. 2B.

The section in which the pulsating voltage rectified by the full-wave rectifier circuit 11 is higher than the charging voltage Vc6 of the charging capacitor C13 is referred to as section TA, and the section in which the pulsating voltage is low is referred to as section TB.

First, the operation in the section TA will be described.

When the transistor Q11 of the high-frequency inverter circuit 16 is turned on at an arbitrary time in the section TA,
The current supply to the primary winding Tr11a of the transformer Tr11 is the first
From the second capacitor C11 and the second capacitor C12 at the same time. Then, the first capacitor C11 and the second capacitor C11
The combined capacitance of the capacitor C12 and the high-frequency inverter circuit
16 has enough capacity to provide the energy needed.

Further, in accordance with the current supply from the first capacitor C11 and the second capacitor C12, energy flows from the commercial AC power source E as the input current I1. The transistor Q1 responds to the change in the pulsating voltage.
This is performed in accordance with the switching operation of No. 1 and a small and equal high-frequency amplitude of the inverter operation is superimposed on the entire section TA along the sine wave value of the AC voltage. That is, in this section TA, the combined value of the first capacitor C11 and the second capacitor C12 is a value in which the energy given by the supply pulsating voltage is satisfied with respect to the energy required by the high-frequency inverter circuit 16. I have.

Therefore, the first and second capacitors C11
, C12 also have small ripple components and small heat generation,
Operation reliability can be improved.

Then, in this section TA, the charging from the tertiary winding Tr11c to the charging capacitor C13 is performed when the transistor Q11 is turned off. In this section TA, the discharging from the charging capacitor C13 to the high-frequency inverter circuit 16 is not performed.

Next, the operation in the section TB will be described.

In this section TB, when the transistor Q11 is turned on when the level of the pulsating sine wave voltage starts to decrease with respect to the charging voltage Vc6 of the charging capacitor C13, the primary winding Tr11a of the transformer Tr11. Current supply to the second
From the capacitor C12. Since the capacity of the second capacitor C12 is insufficient to provide the energy required by the high-frequency inverter circuit 16, the second current increases as the current flowing through the primary winding Tr11a increases after the transistor Q11 turns on. The voltage Vc12 of the capacitor C12 decreases. Also, from the time when the voltage Vc12 drops to the voltage Vc11 of the first capacitor C11, the first capacitor C11 supplies energy to the high-frequency inverter circuit 16 which is insufficient in the second capacitor C12.

This operation is performed until the transistor Q11 is turned off. However, after the energy supply from the first capacitor C11 is started, the second capacitor C1 is turned off.
2, the decrease in the voltage Vc12 is reduced. Further, in supplying energy from the first capacitor C11 to the high-frequency inverter circuit 16, a corresponding amount of energy flows from the commercial AC power supply E side as the input current I1.

On the other hand, the charging voltage V of the charging capacitor C13
In c13, the release of energy is delayed due to the transient impedance of the inductance element L12, and the energy is released immediately before the transistor Q11 is turned off. Then, when the transistor Q11 is turned off, the charging voltage Vc13 of the charging capacitor C13 becomes the inductance element L12, the diode
It provides a voltage supply to a series circuit consisting of D13 and a second capacitor C12. Here, since the inductance element L12 and the second capacitor C12 are set so as to obtain an oscillating resonance, the charging of the second capacitor C12 is performed in a sine wave shape. This charging is increased to a level at which the energy supply does not become insufficient when the transistor Q11 is turned on next time in the high-frequency inverter circuit 16.

The charging voltage V of the charging capacitor C13
As compared with c13, the voltage Vc12 of the second capacitor C12 decreases as the voltage Vc11 of the first capacitor C11 decreases, and the inductance element decreases as the voltage Vc12 decreases.
The amplitude due to L12 and the second capacitor C12 increases.
Although the input current I1 decreases, the current flows continuously.

Thus, the actual voltage Vc12 of the second capacitor C12 has the waveform shown in FIG. The input current I1 and the input voltage V1 have waveforms shown in FIG.

As described above, the input current I1 from the commercial AC power supply E continuously flows, thereby preventing a harmonic component from intervening in the input current I1.

Next, frequency control by the control circuit 17 will be described.

First, as shown in FIG. 4A, when a current waveform having the same phase with respect to the voltage is generated from the commercial AC power supply E, the voltage detection circuit 18 and the current detection circuit 19 output the waveform shown in FIG.
The waveform shown in FIG.

A capacitor C14, a second capacitor C12, which is a component of the high-frequency inverter circuit 16, etc.
When the transistor Q11, the transformer Tr11, and the inductance element L12 fluctuate by about ± 5 to 10%, which is a general tolerance, the energy consumed by the high-frequency inverter circuit 16 is increased by a sine wave input current. When the energy does not match the energy supplied to the input current, the waveform of the input current is distorted as shown in FIGS.

In the case of an inductive load as shown in FIG. 1, this distortion is obtained by utilizing the phenomenon that the impedance of the load increases and the energy consumption decreases as the frequency increases. Decreases, and FIG.
As shown in (c), when the current value increases with respect to the sine wave, the frequency of the transistor Q11 is increased by the control circuit 17, and the energy consumption is increased to make the waveform close to the sine wave. Conversely, by utilizing the phenomenon that the impedance of the load decreases and the energy consumption increases due to the decrease in the frequency, that is, the load increases, as shown in FIGS. 3B and 3D. As described above, when the current value decreases with respect to the sine wave, the frequency of the transistor Q11 is reduced by the control circuit 17, and the energy consumption is reduced to make the waveform close to the sine wave.

On the other hand, when the distortion is a capacitive load, the phenomenon that the impedance of the load decreases and the energy consumption increases due to the decrease in the frequency, that is, the load increases, As shown in FIGS. 3B and 3D, when the current value decreases with respect to the sine wave, the frequency of the transistor Q11 is reduced by the control circuit 17 so that the energy consumption is reduced and the sine wave is approximated. Make a waveform. On the other hand, by utilizing the phenomenon that the impedance of the load increases due to the increase in the frequency and the energy consumption decreases, that is, the load decreases, as shown in FIG.
As shown in (c), when the current value is increased with respect to the sine wave, the frequency of the transistor Q11 is increased by the control circuit 17, and the energy consumption is increased to make the waveform close to the sine wave.

Returning to the general operation, when the transistor Q11 turns on, the collector current IQ1 flows.
Since the supply voltage is the highest at this point, the collector current IQ1 is large. On the other hand, at points P2 and P3, the current is determined by the level of the charging voltage Vc13, but decreases gradually. The amount of the current Ic12 flowing through the second capacitor C12 when the transistor Q11 is turned on is small, and as shown by the current ID1, the current Ic12 passes through the first capacitor C1 via the diode D11.
Supplied from 1. Since this supply is sufficient, the voltage Vc12 hardly fluctuates. Therefore, the input current I1 flows continuously from the commercial AC power supply E based on the current ID1 in a form to supplement the released energy.

Further, as the supply voltage decreases at points P2 and P3, the inductance element L12 and the second capacitor C12
The amplitude of the oscillating voltage due to the
Is turned on to a level that supplies sufficient energy to the transistor Q11 when the second capacitor C1 is turned on.
2 is raised to a sufficient level.

Therefore, the high-frequency inverter circuit 16 performs a stable oscillation operation over the entire section in which the transistor Q11 is on. And the sine wave voltage is P1
As the point decreases to points P2 and P3, an input current I1 commensurate with the reduced voltage flows from the commercial AC power supply E side, and as a result, the input current I1 flows continuously. That is, as shown in FIG. 2D, an input current I1 having a very small continuous harmonic component flows.

As described above, even at the point P3 where the AC pulsating voltage is close to zero, the inductor L12 generated by the charging voltage Vc13 of the charging capacitor C13 and the second capacitor C12
It is important that the oscillating voltage is generated in accordance with the on / off timing of the transistor Q11 so that the oscillating operation of the high-frequency inverter circuit 16 is performed stably.

If this condition is not satisfied, the oscillation condition of the inductance element L12 and the second capacitor C12 in the oscillation circuit is bad, and the voltage Vc12 of the second capacitor C12 is not sufficiently increased and energy supply to the high-frequency inverter circuit 16 is not performed. Run out. Then, due to energy shortage, the current flowing through the transistor Q11 becomes a sharp spike-like current.

Further, even if the switching ripple of the transistor Q11 is superimposed on the input current I1, it is removed by the first capacitor C11.

Furthermore, the rush current when the power is turned on is the first
The second capacitor C11, C12 has a whisker-like inrush current, which is negligibly smaller than the inrush current of the conventional device, and does not cause any trouble to circuit components connected to the power supply line. Therefore, a small component having a low withstand voltage can be used as a circuit component, and the main components are the first and second capacitors C11 and C12, the charging capacitor C13,
It can be composed of the inductance element L12, diodes D12 and D13 and the tertiary winding Tr11c, and the configuration is simple.

Therefore, in the above embodiment, the harmonic component in the input current can be reduced, and the size, the price, and the configuration can be simplified.

Next, a specific circuit of the circuit shown in FIG. 1 will be described with reference to FIG.

The circuit shown in FIG. 5 is different from the circuit shown in FIG. 1 in that two resistors R11 and R1 are used as the voltage detection circuit 18.
2, a current transformer CT11 is used as the current detection circuit 19. Further, an operational amplifier OP11 for comparing the outputs of the voltage detecting circuit 18 and the current detecting circuit 19 is provided. The output of the operational amplifier OP11 is connected to the control circuit 17, and the reference voltage is a resistor connected to the full-wave rectifier circuit 11. Obtained in a series circuit of R13 and capacitor C21. Further, the control circuit 17 includes a current transformer having a detection winding CT12a connected between the capacitor C15 and the filament electrode FLb of the discharge lamp FL at the base of the transistor Q11.
The output winding CT12b of CT12 is connected. Further, capacitors C22 and C23 and a field effect transistor FET1 for varying the impedance are connected to the output winding CT12b.

When the input voltage becomes higher than the input current, the operational amplifier OP11 performs an H level output, and increases the apparent capacitance of the capacitor C22 by applying the gate voltage of the field effect transistor FET1. The frequency of the high-frequency inverter circuit 16 is reduced, the impedance of the high-frequency inverter circuit 16 and the like is reduced, and the waveform of the input current approaches a sine wave.

On the other hand, when the input voltage becomes lower than the input current, the operational amplifier OP11 performs an L level output, and does not apply the gate voltage of the field effect transistor FET1, thereby reducing the apparent capacitance of the capacitor C22. The frequency of the high-frequency inverter circuit 16 is increased to increase the impedance of the high-frequency inverter circuit 16 and the like, so that the waveform of the input current approaches a sine wave.

The same effect can be obtained without providing the capacitor C23.

The driving of the high-frequency inverter circuit 16 is not limited to the separately excited type, but may be a self-excited type. In the case of the self-excited type, the capacitance connected to the base is changed as described above. What is necessary is just to control a frequency.

Next, another embodiment will be described with reference to FIG.

The circuit shown in FIG. 6 is different from the circuit shown in FIG. 4 in that a sensing winding L22 magnetically coupled to the inductance element L12 is provided, and a diode D21, a capacitor C24 and a resistor are provided on the output side of the sensing winding L22. Connect R14.
A field effect transistor is also used for the capacitor C23.
Provide FET2. Then, a bypass transistor Q21 is connected to a connection point between the output terminal of the operational amplifier OP11 and the gate of the field effect transistor FET1, and the field effect transistor F
The bypass transistor Q22 is connected to the gate of ET2.

In the circuit shown in FIG. 6, the control circuit 17 controls the frequency only in the discharge period TB during which the charging capacitor C13 discharges.

That is, when the charging capacitor C13 is charged, an L level current is supplied to the base of the transistor Q21, the output from the operational amplifier OP11 is bypassed, and a voltage is applied to the gate of the field effect transistor FET1. That is what we do not do. However, if the field effect transistor FET1 is not simply controlled, the capacitance of the capacitor C22 becomes zero, so that the frequency of the high-frequency inverter circuit 16 becomes high, and the energy becomes too small. Is performed, the gate voltage of the field effect transistor FET2 is controlled. Since the transistor Q22 and the transistor Q23 have opposite characteristics, when the field-effect transistor FET1 is controlled, the field-effect transistor FE
T2 is not controlled, and conversely, a field-effect transistor
If FET2 is controlled, field-effect transistor FET1
Is not controlled.

According to the circuit shown in FIG. 6, when the output level of full-wave rectifier circuit 11 is higher than the charging level of charging capacitor C13, the frequency control is disabled without changing the output frequency. In the case where the voltage from the full-wave rectifier circuit 11 is low, harmonics are easily generated, so that the output frequency can be changed to suppress the generation of harmonics.

In each of the above embodiments, a single-type inverter is used, but other types of inverters can be used.

Regarding control, digital control may be performed and integrated in order to reduce the size and multifunction of the product.
For example, if the output from the operational amplifier OP11 is digitized by an analog-to-digital converter and this digitized output is generated by counting the pulse width of the drive frequency, the count is increased if you want to increase the frequency. If it is desired to reduce the pulse width to shorten the pulse width, and conversely, to lower the frequency, the oscillation frequency of the high-frequency inverter circuit 16 can be set by increasing the count number and increasing the pulse width. In addition, other methods of digital control can be performed.

Although each of the embodiments has been described as applied to a discharge lamp lighting device, it can be used for devices other than a discharge lamp lighting device.

[0070]

According to the power supply device of the present invention, the AC from the AC power supply is rectified by the rectifier circuit, and the pulsating current rectified by the rectifier circuit is charged to the capacitor. Then, power is supplied to the inverter circuit via the rectifying element, and the inverter circuit oscillates. The oscillation of this inverter circuit is
The output frequency is changed according to the output of the rectifier circuit. That is, depending on the voltage input from the rectifier circuit, the harmonic component increases, so that the harmonic component can be suppressed by changing the frequency, the voltage waveform and the current waveform can be made in phase, and approximate to a sine wave.

According to the power supply device of the second aspect, in the power supply device of the first aspect, when the output level of the rectifier circuit is higher than the charge level of the charging capacitor, the output frequency is not changed. It is possible to prevent the frequency control from being disabled, and to generate harmonics depending on the voltage input from the rectifier circuit, so that the output frequency can be changed to suppress the generation of harmonics.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a power supply device of the present invention.

FIG. 2 is a waveform chart showing a voltage waveform and a current waveform of each part of the above.

FIG. 3 is a waveform chart showing various input current waveforms according to the first embodiment;

FIG. 4 is a waveform chart showing a relationship between an input voltage and an input current.

FIG. 5 is a circuit diagram showing a power supply device according to another embodiment of the present invention;

FIG. 6 is a circuit diagram showing a power supply device according to another embodiment of the present invention;

FIG. 7 is a circuit diagram showing a conventional power supply device.

[Explanation of symbols]

 11 Full-wave rectifier circuit 12 Charging circuit 16 High-frequency inverter circuit C13 Charging capacitor D11 Diode as rectifying element E Commercial AC power supply

Claims (2)

(57) [Claims] 1. A rectifier circuit for rectifying an alternating current from an AC power supply, a capacitor connected in parallel to an output terminal of the rectifier circuit, and a rectifier element connected in series to one end of the capacitor with forward polarity. An inverter circuit having a charging capacitor connected to the rectifier circuit via the rectifier element and a charging circuit having an inductor element; and changing an output frequency of the inverter circuit in accordance with an output of the rectifier circuit. Power supply device characterized by the following. 2. The power supply device according to claim 1, wherein the frequency of the inverter circuit is changed only when the output level of the rectifier circuit is lower than the charge level of the charging capacitor.