JPH06269161A - Power supply - Google Patents

Abstract

PURPOSE:To provide a power supply in which surge current is eliminated and distortion of input current is suppressed while enhancing input power factor and conversion efficiency. CONSTITUTION:A chopper circuit can set a booster chopper operation or a step-up/step-down chopper operation by means of a switch element SW1. If the peak value of an AC power supply AC voltage V1 is higher than an output voltage V0, the switch element SW1 is turned to side (a), i.e., step-up/step-down chopper operation, thus preventing surge current. When the output voltage V0 exceeds the peak value of power supply voltage V1, the switch element SW1 is turned to side (b), i.e., booster chopper operation, thus enhancing conversion efficiency and improving harmonic distortion.

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 for converting an AC power supply into a DC power supply.

[0002]

2. Description of the Related Art As a power supply device for converting an AC power supply into a DC power supply, as shown in FIG. 6, a so-called capacitor input type power supply device for simply rectifying and smoothing an AC power supply to obtain a direct current,
Conventionally, there is a power supply device using a step-up chopper circuit as shown in FIG. 9 or a power supply device using a step-up / down chopper (or a polarity reversal type chopper circuit) shown in FIG.

The operation of these power supply devices will be briefly described. First, since the capacitor input type power supply device shown in FIG. 6 is a peak value charging type, when the line-operated type power supply uses an AC power supply AC of 100 V as an input power supply, the maximum pulsating current output of the diode bridge DB is obtained. The smoothing capacitor C is charged to a value of about 140V. However, as shown in FIG. 7A, when the voltage value of the pulsating current becomes lower due to the voltage relationship between the terminal voltage V ₀ of the smoothing capacitor C and the pulsating current, the charging current to the smoothing capacitor C becomes as shown in FIG. It does not flow as shown in (b). But even during this time,
The load connected to the both ends of the smoothing capacitor C continues to discharge the accumulated charge of the smoothing capacitor C, so that the terminal voltage V ₀ of the smoothing capacitor C gradually decreases with time, and the slope of this decrease is due to the load resistance R and the smoothing. It is determined by the time constant of the capacitance of the capacitor C and the terminal voltage V ₀ after a certain time t elapses.
Can be expressed as V _C = V _P · ε ^{-t / CR} , where V _P is the maximum charging voltage.

Next, when the pulsating current voltage starts to rise again and becomes higher than the terminal voltage V ₀ of the capacitor C, the charging current flows again and the terminal voltage V ₀ also rises accordingly. The fluctuation of the terminal voltage V ₀ becomes the output ripple voltage. Therefore, for a certain load resistance R, the larger the capacitance of the smoothing capacitor C is, the more gradually the falling slope of the voltage in the period t ₂ shown in FIG. 7 becomes, and the ripple voltage becomes a small value.

The charging current of the smoothing capacitor C does not flow in the entire period of the AC cycle as described above, but flows only in the period of t ₁ as shown in FIG. 7B. This t ₁ period is called a conduction angle, but since the average value of the charging current to the smoothing capacitor C must be equal to the DC output current I ₀ ,
It can be expressed as the following formula (1).

[0006]

[Equation 1]

That is, the area of the charging current in FIG.
It means equal to ₀ . However, in order to flow the same output current I ₀ , the maximum value i _P of the charging current must be increased as the conduction angle t ₁ becomes smaller. Therefore, the effective value i _RMS of the charging current is
It becomes a very large value like the formula.

[0008]

[Equation 2]

Therefore, there is a problem that the electrolytic capacitor used as the smoothing capacitor C has a shortened life due to temperature rise due to internal loss. Therefore,
In order to make a highly reliable power supply device, it is necessary to reduce the charging peak current i _P to the smoothing capacitor C as much as possible and reduce the ripple current. Since the charging current to the smoothing capacitor C in the line operate type regulator flows in the same waveform as the current of the input side AC circuit, when viewed from the AC power supply AC, the apparent power factor (c
osφ = W / VA) decreases. The apparent power factor of the rectifying / smoothing circuit is not the phase shift but the ratio of the effective power W to the apparent power VA. In the ordinary capacitor input type rectification, W / VA≈0.6. It's a pretty bad number. This is a problem that occurs because the effective value of the current indicating the apparent power is large. Further, as can be seen from the input current waveform in FIG. 8, there is a problem that there are many harmonic components with respect to the fundamental wave. Furthermore, since the smoothing capacitor C is charged rapidly when the AC power supply AC is turned on, a larger inrush current than that in the steady state flows, which adversely affects the switch that opens and closes the AC power supply AC.

In the step-up chopper circuit shown in FIG. 9, a switching element Q ₁ composed of a transistor is connected between an inductance element L and a ground. When the switching element Q ₁ is turned on, the AC power supply AC is switched to a diode bridge DB. rectified current i ₁ flows through the inductance element L from the input supply V _iN obtained, the current i ₁ flowing to the inductance element L increases monotonically in proportion to time as shown in FIG. 10, i ₁ = (V _IN / L ₁ ) · t. Here, the voltage effect due to the switching element Q ₁ is omitted. At this time, since the collector-emitter voltage of the switching element Q ₁ is the saturation voltage V _{CE (sat)} , the relationship with the output voltage V ₀ is V ₀ > V _{CE (sat)} .
Therefore, no current flows through the diode D to the output side. After that, when the conduction period of the switching element Q ₁ is t = t _ON , i ₁ reaches its maximum value, and at this time, energy is stored in the inductance element L, and this energy P _L is the on / off repetition frequency of the switching element Q ₁ being f. ,
The per unit time, and _{P L = (L 1/2} ) · i 1P 2 · f = ^{_{[(V IN 2 · t ON 2}} ) / 2L 1 ] · f.

When the switching element Q ₁ is turned off, a counter electromotive force is generated in the inductance element L, and a current i ₂ flows out while charging the smoothing capacitor C through the diode D. Ignoring the directional voltage drop, the voltage applied to the switching element Q ₁ is V _CE = V ₀ , so the voltage _VL across the inductance element _L is _VL = V ₀ −V _IN .

In this type of chopper, the maximum values of i ₁ and i ₂ are equal, so that i ₂ decreases linearly from i _1P , i ₂ = i _1P − (V _L / L) · t = [(V _IN / L) · t _ON ] − [(V ₀ −V _IN ) / L) · t].

The voltage across the capacitor C is the output voltage V
_Therefore , assuming that the output current is I ₀ and the load resistance is R, the output power P ₀ and the stored power of the inductance element L must be equal. Therefore, P ₀ = I ₀ · V ₀ = V ₀ ² / R = [(V _IN ² · t _ON ² ) / 2L] · f. From this equation, the output voltage V ₀ is V ₀ = [(V _IN ² · t _ON ² ) / (2L · I ₀ )] · f.

From this equation, when the input voltage or the output current changes, the output voltage V ₀ can be kept stable by changing the _ON time t _ON of the switching element Q _{1 in} the opposite direction. Unlike the capacitor input type, the power supply device using this step-up chopper circuit switches the pulsating current waveform a which is full-wave rectified by the diode bridge DB at a frequency of several tens of kHz or more over the entire period, as shown in FIG. To do. By doing this, the waveform of the input current b becomes the average value of each cycle of each switching current c, and even if there is a large capacitor in the load, it will be equivalent to a pure resistance load, and the input switching current c will be In general, it flows as a sine wave. Even if the input voltage fluctuates or the load current changes, if the maximum value of each switching current is changed accordingly, the output voltage can be made constant and the ripple of the smoothing capacitor C can be changed. The current can be reduced significantly.

As described above, in the case of the step-up chopper circuit, the input power factor is improved, the harmonic components of the input current are reduced, the output voltage can be stabilized, and the conversion efficiency can be increased relatively easily. There is an advantage that you can. In the power supply device using the buck-boost chopper circuit shown in FIG. 12, when the switching element Q ₁ composed of a transistor is turned on, the current i is passed through the inductance element L from the input power supply V _IN obtained by rectifying the AC power supply AC with the diode bridge DB. ₁ flows, flows into the inductance element L, and stores energy in the inductance element L. When the period during which the switching element Q ₁ and t _ON, the maximum value i _1P of i ₁ becomes _{i 1P = (V IN / L} ) · t. Therefore, the stored energy P of the inductance element L
_L, when the repetition frequency of the on-off switching element Q ₁ is is f, the unit _{time, = P L = (L /} 2) · i 1P 2 · f ^{_{[(V IN 2 · t ON 2}} ) / 2L ]・ It becomes f.

When the switching element Q ₁ is turned off after t _ON , a back electromotive force is generated in the inductance element L, and a current i ₂ flows through the capacitor C and the diode D ₂ by this back electromotive force, and this current i ₂ Causes a DC voltage with the polarity shown in the figure across capacitor C,
This voltage becomes the negative output voltage V ₀ . Since the applied voltage is V _CE = V ₀ , the voltage _VL across the inductance element _L is V _L = V ₀ −V _IN .

Assuming that the output current is I ₀ , the accumulated power P _L accumulated in the inductance element L becomes equal to the output power P ₀ , so P ₀ = I ₀ · V ₀ = [(V _IN ² · t _ON ² ) / 2L] · f. As can be seen from this equation, even if the output current I ₀ or the input voltage V _IN changes, the output voltage V ₀ can be kept stable if the _ON time t _ON of the switching element Q ₁ is changed accordingly. .

In FIG. 13, the current i ₂ for charging the capacitor C is due to the counter electromotive force of the inductance element L, but the current flowing through the inductance element L tends to become discontinuous. Therefore, the waveform tends to decrease from the maximum current i _1P when the switching element Q ₁ is on. That is, the current i ₂ is as follows. i ₂ = i _1P − (V ₀ / L) · t In this formula, the current i ₂ has the minimum value at t = t _OFF , and the change width of the current i ₂ is considerably large. ΔV ₀ becomes large. Therefore, as the smoothing capacitor C, a capacitor having a sufficient capacity and internal impedance is used. This step-up / step-down chopper circuit has an advantage that there is no inrush current, and has an advantage that the output voltage V ₀ can be made higher or lower than the input voltage.

[0019]

As described above, the power supply device using the boost chopper circuit is characterized in that the input power factor can be improved, which is a problem of the capacitor input type rectification type power supply device. However, there are problems that the inrush current is large and the output voltage becomes higher than the input voltage.

Further, in the power supply device using the step-up / down chopper circuit, it is necessary to use a smoothing capacitor having a large capacity and a sufficient internal impedance.
Further, there is a problem that it is more difficult to design the harmonic component of the input current, and it is more difficult to improve the conversion efficiency than the boost chopper circuit. The present invention has been made in view of the above-mentioned problems, and the object thereof is to have no inrush current, moreover, input current distortion is small, input power factor is high, conversion efficiency is high, and transient It is to provide a power supply device capable of adjusting the output voltage in a wide range.

[0021]

In order to achieve the above object, according to the invention of claim 1, in a power supply device for converting an AC power supply into a DC power supply by using a chopper circuit, the operation of the chopper circuit is a boost chopper operation. And a switching switch element for switching between the step-up and step-down chopper operation.

According to a second aspect of the present invention, in the first aspect of the present invention, a rectifying circuit for rectifying an AC power source and a switching element are connected between output terminals of the rectifying circuit via an inductance element, and the switching element is connected to the switching element. A capacitor is connected in parallel via a unidirectional changeover switch element, and a diode is connected between the connection point between the capacitor and the unidirectional changeover switch element and the connection point between the inductance element and the rectifier circuit, When the switching element is turned on, the energy of the inductor element accumulated when the switching element is turned on forms a boost chopper circuit that charges the capacitor when the switching element is turned off.When the switching element is turned off, the switching element is turned on. When the switching element is turned off, the accumulated energy of the inductor element is Inductor scan elements, and constitutes a capacitor, a diode, a buck-boost chopper circuit that releases a closed circuit of the inductor scan element.

According to a third aspect of the present invention, in the first or second aspect of the invention, the step-up / down chopper operation is performed for a certain period,
The changeover switch element is set to change so as to perform the step-up chopper operation in a steady state. According to the invention of claim 4,
In the invention of claim 3, the certain period is set after the power is turned on.

According to a fifth aspect of the invention, in the invention of the third aspect, the load connected to both ends of the capacitor is a discharge lamp ballast using an inverter circuit, and the certain period is the preceding preheating period of the discharge lamp or It is assumed that the discharge lamp is not mounted or the power supplied to the discharge lamp is below the rating.

[0025]

According to the invention of claim 1, when the peak value of the input power supply voltage is higher than the output voltage, the operation of the chopper circuit is set to the step-up / down chopper operation side by the changeover switch element to prevent the inrush current. On the contrary, when the peak value of the input power supply voltage becomes higher than the output voltage, the operation of the chopper circuit is set to the boost chopper operation side by the changeover switch element to improve the high conversion efficiency and harmonic distortion. be able to.

According to the second aspect of the present invention, the step-up chopper circuit and the step-up / step-down chopper circuit share the switching element, the inductance element, and the capacitor, and the step-up chopper circuit and the step-up / step-down chopper circuit are formed by turning on / off the changeover switch element. Since it can be configured, the chopper circuit has a simple configuration and can be manufactured at low cost. According to the invention of claim 3, when the output voltage lower than the input voltage is required for a short time, the buck-boost chopper operation is set to obtain a low voltage, and the boost chopper operation provides high conversion efficiency during the steady operation. Harmonic distortion can be improved.

In particular, according to the invention of claim 4, the step-up / step-down chopper operation is set for a certain period when the power is turned on, and the boost chopper operation is set by the subsequent steady operation, so that the inrush current at the time of turning on the power can be prevented, and It is possible to improve the conversion efficiency during normal operation and harmonic distortion. Claim 5
According to the invention, the output voltage can be suppressed by the buck-boost chopper operation when it is necessary to suppress the output voltage, such as during the preceding preheating period, when the discharge lamp is not mounted, or when the power supplied to the discharge lamp is less than the rating. In addition, the boost chopper operation can be set in a steady state requiring a high voltage, and the discharge lamp can be turned on with a high conversion efficiency and improved harmonic distortion.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a basic configuration of the present embodiment. The chopper circuit 1 can set a boost chopper operation and a step-up / step-down chopper operation by switching a changeover switch element SW _1. Therefore, when the power supply switch SW ₂ is turned on and the peak value of the power supply voltage V _I of the AC power supply AC is higher than the output voltage V ₀ , the changeover switch element SW ₁ is switched to the a side to operate the chopper circuit 1 in the buck-boost chopper. Set to operation to prevent inrush current from flowing.

When the voltage of the output voltage V ₀ becomes higher than the peak value of the power supply voltage V _I of the AC power supply AC, the changeover switch element SW _{1 is changed over} to the side b, and the chopper operation is set to the step-up chopper operation and converted. It improves efficiency and harmonic distortion. Further, for example, in normal use, the changeover switch element SW ₁ is set to the b side, and when a voltage lower than the input power supply voltage V _I is required for a short time, the changeover switch element S 1 is set.
A low voltage can be obtained by setting W ₁ to the a side.

FIG. 2 shows a concrete example of the chopper circuit 1 of the present embodiment, in which a switching element Q _{1 formed of,} for example, a transistor is connected via an inductance element L between output terminals of a diode bridge DB for rectifying an AC power supply AC. And a capacitor C is connected between both ends of the switching element Q ₁ via a changeover switch element SW ₁ .

Changeover switch element SW₁And the capacitor C
Connection point and diode bridge DB ₁The positive output end of
Between the connection point of the inductance element L and the diode block
Ridge DB₁Connect the diode D in the opposite direction as seen from
is there. Changeover switch element SW₁Is like a transistor
It consists of a unidirectional switching element,
It is turned on / off by the control signal. Also chopper operation
Switching element Q for₁Control signal from control circuit 2
To switch at a specified repetition frequency
Has become.

The control circuit 2 detects the voltage across the capacitor C, that is, the output voltage V _0, and when the output voltage V ₀ becomes larger than the peak value V _{1 (PEAK) of} the input power supply voltage V _I , the changeover switch element SW ₁ The input power supply voltage V _I
When the output voltage V ₀ becomes smaller than the peak value V _{1 (PEAK) of the} above, the changeover switch element SW ₁ is turned off.

When the power switch SW ₂ is turned on, V ₀ <V _{1 (PEAK)} , so the control circuit 2 turns off the changeover switch element SW ₁ . Therefore, when the switching element Q ₁ is turned on, a current flows in a loop of diode bridge DB → inductance element L → switching element Q ₁ → diode bridge DB to store energy in the inductance element L, and when the switching element Q ₁ is off, the inductance is increased. Due to the counter electromotive force of the element L, a current flows in the loop of the inductance element L → capacitor C → diode D → inductance element L, and the buck-boost chopper operation is performed, so that no rush current flows.

Eventually, the output voltage V ₀ rises, and V
_{When 0} > V _{1 (PEAK)} , the control circuit 2 turns on the changeover switch element SW ₁ . Therefore, switching element Q ₁
When the switch is turned on, a current flows through the loop of diode bridge DB → inductance element L → switching element Q ₁ → diode bridge DB as in the step-up / down chopper operation, energy is stored in the inductance element L, and the switching element Q ₁ is turned off. Sometimes inductance element L
By the counter electromotive force of the inductance element L → capacitor C → changeover switch element SW ₁ → diode bridge DB
→ Current flows through the loop of the inductance element L, and the step-up chopper operation is performed, so that the conversion efficiency and the input current distortion are improved. Since V ₀ > V _{1 (PEAK)} at this point, there is no concern about inrush current.

Here, when the change-over switch element SW ₁ is in the ON state and the switching element Q ₁ is in the OFF state, it is considered that the current flows through the loop of the above-mentioned loop, but the present inventors have conducted experiments. It was confirmed that there was no problem in practical use because almost no current flowed through the loop. The experiment was conducted using an input power supply voltage V _I of 100 V _(DC) , an inductance value of 1 mH, an inductance element L, a capacitor C having a capacitance of 30 μF, and a load consisting of a resistance of 100 Ω. The current flowing in 2 is 2 mA, and the current flowing in the loop is 2.
It was 5A.

(Second Embodiment) In the first embodiment, the control circuit 2 detects the output voltage V ₀ , and the changeover switch element SW ₁
However, in the present embodiment, the output phototransistor of the photocoupler ₃ is used as the changeover switch element SW ₁ as shown in FIG. 3, and the voltage sensing element 4 including a surge absorbing element such as ZNR is used. , A resistor R ₁ and a series circuit of the light emitting diode LED on the input side of the photocoupler 3 are connected in parallel to the capacitor C, and the voltage across the capacitor C, that is, the output voltage V ₀ is the breakover voltage of the voltage sensing element 4. When the voltage exceeds the voltage sensing element 4, the resistor R _1, and the light emitting diode LED on the input side of the photocoupler 3.
When a current flows through the series circuit of, the light emitting diode LED emits light, and the changeover switch element SW ₁ is turned on.

Thus, in this embodiment, when the output voltage V ₀ is less than the breakover voltage of the voltage sensing element 4,
Since no current flows in the light emitting diode LED, the switch element SW _{1 including the} phototransistor of the photocoupler 3
Is turned off, and the step-up / down chopper operation is performed as in the first embodiment. Eventually, when the output voltage V ₀ rises and exceeds the breakover voltage of the voltage sensing element 4, a current flows through the light emitting diode LED, and the changeover switch element SW ₁ composed of the phototransistor of the photocoupler 3 is turned on, which is the same as the first embodiment. Similarly, the boost chopper operation is performed.

Since the phototransistor of the photocoupler 3 has a small collector current, means for further amplifying it may be provided. Further, although the output voltage V _{0 is} detected by using the voltage sensing element 4 formed of a surge absorbing element such as ZNR, the voltage may be detected by using another voltage sensitive element. Although the photocoupler 3 is used, the changeover switch element SW _{1 formed} of a transistor or the like may be directly driven by the conduction current of the voltage sensing element 4.

(Embodiment 3) In this embodiment, as shown in FIG. 4, a discharge lamp ballast 6 using a self-excited inverter circuit is used as a load, and the filament of the fluorescent lamp La is preheated during the preheating. In order to reduce the output voltage V ₀ , a control circuit 5 for controlling the changeover switch element SW ₁ is provided so as to perform the step-up / down chopper operation during the preceding preheating period and perform the step-up chopper operation during the start-up lighting. is there.

That is, when the fluorescent lamp La is turned on, in order to prevent the life of the lamp from being shortened, a method is used in which a preceding preheating period for heating the filament is set before starting and the starting lighting is performed after preceding preheating. In the discharge lamp ballast 6 using the self-excited inverter circuit, unlike the separately excited type, it is difficult to perform control such as setting the preceding preheating period.

In view of this point, in this embodiment, the operation of the chopper circuit 1 is switched to obtain the above lighting process. Then, when the power switch SW ₂ is turned on, the control circuit 2 starts the operation as shown in FIG. 5A to switch the switching element Q ₁ . At the same time, the control circuit 5 detects the closing of the power switch SW ₂ by the output of the diode bridge DB and turns off the changeover switch element SW ₁ . That is, the operation of the chopper circuit 1 after the power is turned on is the buck-boost chopper operation. Therefore, the output voltage V ₀ during the step-up / down chopper operation becomes a low voltage substantially close to the peak value of the AC power supply AC as shown in FIG. 5C, and therefore the output voltage of the discharge lamp ballast 6 is also low and the fluorescent lamp L
Only a preheat will be performed without lighting a.

The control circuit 5 has a timer function, and when the time corresponding to the preset preheating period t ₁ is counted, the resistance R is added to the base of the changeover switch element SW _1.
The drive signal is output via ₂ as shown in FIG.
The changeover switch element SW ₁ is turned on. That is, the operation of the chopper circuit 1 is switched to the boost chopper operation. Therefore, the output voltage V ₀ rises, and the output of the discharge lamp ballast 6 also rises due to this rise of the output voltage V ₀ , and the fluorescent lamp La is started and lit.

Considering the breakdown voltage of the switching element Q ₁ and the capacitor C, the output voltage V ₀ is generally 50
Although it is suppressed to less than 0V, when the voltage of the AC power supply AC is 200V system in Japan or 277V system in the United States, the output voltage V ₀ is about 280V corresponding to each peak value even if the boost chopper operation is stopped. , A high value of about 390V. Thus, even if the minimum value of the output voltage V ₀ becomes high,
Since the practical maximum value does not change to about 500 V or less, the difference between the minimum value and the maximum value of the output voltage V ₀ becomes small, and the discharge lamp ballast 6 using the self-excited inverter circuit can be used under any condition. It may be difficult to perform pre-heating of the fluorescent lamp La and to design so as to satisfy the condition that the fluorescent lamp La is always started and turned on under any condition.

However, such difficulty can be overcome by using this embodiment. That is, even if the voltage of the AC power supply AC is 227 V and the output voltage V _{0 (max)} is 450 V, the operation of the chopper circuit 1 is the buck-boost chopper operation during the preceding preheating period, and the output voltage V ₀ is 140 V.
It can be done to some extent. In this case, the conversion efficiency is reduced and the harmonic distortion of the input current is increased, but since the preceding preheating period is only about 2 seconds, the circuit itself is not adversely affected.

At the start-up lighting, the output voltage V ₀ is set to 450 V by setting the operation of the chopper circuit 1 to the boost chopper operation. At this time, the conversion efficiency is increased and the harmonic distortion of the input current is also improved. In this way, by setting the operation of the chopper circuit 1, it is possible to generate the output voltage V ₀ corresponding to the preceding preheating period and the starting lighting, respectively. Therefore, the discharge lamp ballast 6 using the self-excited inverter circuit can be used. The design can be facilitated and the desired operation can be reliably performed.

The output voltage V ₀ may be gradually increased by the step-up / step-down chopper operation when shifting from the preceding preheating period to the starting lighting period. The portion X in FIG. 5C shows the change in the output voltage V _{0 in} this case. In addition to the preheating preceding period, for example, during dimming with low power consumption,
The output voltage V ₀ may be lower than the step-up / down chopper operation when there is no load.

In each of the above embodiments, the changeover switch element SW ₁ is formed by using a transistor, but it is also possible to use a structure for manually changing over by using a pattern changing means, a jumper wire or the like.

[0048]

According to the invention of claim 1, in a power supply device for converting an AC power supply into a DC power supply by using a chopper circuit, a changeover switch element for switching the operation of the chopper circuit between a boost chopper operation and a buck-boost chopper operation is provided. Therefore, when the peak value of the input power supply voltage is higher than the output voltage, the inrush current is prevented by setting the operation of the chopper circuit to the buck-boost chopper operation side with the changeover switch element.
On the contrary, when the peak value of the input power supply voltage becomes higher than the output voltage, high conversion efficiency and higher harmonic distortion can be improved by setting the operation of the chopper circuit to the boost chopper operation side by the changeover switch element. The effect is that you can do it.

According to a second aspect of the present invention, a rectifier circuit for rectifying an AC power source and a switching element are connected between output terminals of the rectifier circuit via an inductance element, and a capacitor is unidirectionally connected in parallel with the switching element. Connected via the changeover switch element of, the diode is connected between the connection point of the capacitor and the one-way changeover switch element, and the connection point of the inductance element and the rectifier circuit, and by the ON setting of the changeover switch element. , The energy of the inductor element accumulated when the switching element is turned on forms a boost chopper circuit that charges the capacitor when the switching element is turned off.By setting the changeover switch element off, the inductor element accumulated when the switching element is turned on. Energy is transferred to the inductor element and capacitor when the switching element is off. Since a buck-boost chopper circuit that discharges by a closed circuit of a capacitor, a diode, and an inductor element is configured, the switching element, the inductance element, and the capacitor of the boost chopper circuit and the buck-boost chopper circuit are made common, and the switching switch element is turned on / off. Since the boost chopper circuit and the buck-boost chopper circuit can be configured,
The chopper circuit has a simple structure and can be manufactured at low cost.

According to the third aspect of the present invention, since the changeover switch element is switched and set so that the step-up / step-down chopper operation is performed for a certain period and the step-up chopper operation is normally performed, an output voltage lower than the input voltage is required for a short time. In such a case, the buck-boost chopper operation is set to obtain a low voltage, and in the steady operation, the boost chopper operation has a high conversion efficiency and higher harmonic distortion.

According to the fourth aspect of the present invention, the step-up / step-down chopper operation is performed for a certain period of time, and the changeover switch element is switched and set so as to steadily perform the step-up chopper operation. Therefore, inrush current at power-on can be prevented, and moreover, The conversion efficiency during steady operation,
There is an effect that the harmonic distortion can be improved. According to a fifth aspect of the present invention, the load connected to both ends of the capacitor is a discharge lamp ballast using an inverter circuit, and the predetermined period is the preceding preheating period of the discharge lamp or when the discharge lamp is not attached or when the discharge lamp is not installed. Since the supplied power is below the rating,
The output voltage can be lowered by setting the buck-boost chopper operation when it is necessary to suppress the output voltage, as in the case of the preceding preheating period or when the discharge lamp is not attached or when the power supplied to the discharge lamp is less than the rating. Also, in a steady state where a high voltage is required, the boost chopper operation can be set to turn on the discharge lamp with high conversion efficiency and improved harmonic distortion, facilitating the design of the discharge lamp ballast. Moreover, there is an effect that safety can be improved.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a first embodiment of the present invention.

FIG. 2 is a specific circuit diagram of the above.

FIG. 3 is a specific circuit diagram of the second embodiment of the present invention.

FIG. 4 is a specific circuit diagram of a fourth embodiment of the present invention.

FIG. 5 is a timing chart for explaining the above operation.

FIG. 6 is a circuit diagram of a conventional example.

FIG. 7 is a waveform diagram for explaining the same operation as above.

FIG. 8 is a waveform diagram of the input current of the above.

FIG. 9 is a circuit diagram of another conventional example.

FIG. 10 is a timing chart for explaining the operation of the above.

FIG. 11 is a waveform diagram for explaining the operation of the above.

FIG. 12 is a circuit diagram of another conventional example.

FIG. 13 is a timing chart for explaining the above operation.

[Explanation of symbols]

1 Chopper circuit SW ₁ Changeover switch element AC AC power supply V _I Power supply voltage V ₀ Output voltage

Claims (5)

[Claims] 1. A power supply device for converting an AC power supply into a DC power supply using a chopper circuit, comprising a changeover switch element for switching the operation of the chopper circuit between a boost chopper operation and a step-up / down chopper operation. Power supply. 2. A rectifier circuit for rectifying an AC power source, a switching element connected between output terminals of the rectifier circuit via an inductance element, and a capacitor in parallel with the switching element, which is a unidirectional changeover switch element. Connected via a diode, connect a diode between the connection point between the capacitor and the unidirectional changeover switch element and the connection point between the inductance element and the rectifier circuit, and turn on the switching element by turning on the changeover switch element. The energy of the inductor element accumulated at the time forms a boost chopper circuit that charges the capacitor when the switching element is off, and the energy of the inductor element accumulated when the switching element is turned on is set by turning off the changeover switch element. When off, inductors, capacitors, diodes, Power supply according to claim 1, characterized in that it constitutes a buck-boost chopper circuit that releases a closed circuit of Ndakutasu element. 3. The power supply device according to claim 1, wherein the changeover switch element is switched and set so that the step-up / step-down chopper operation is performed for a certain period and the step-up chopper operation is normally performed. 4. The power supply device according to claim 3, wherein the fixed period is set after the power is turned on. 5. A load connected to both ends of the capacitor is a discharge lamp ballast using an inverter circuit, and the constant period is a preceding preheating period of the discharge lamp, or when the discharge lamp is not mounted, or power supplied to the discharge lamp. 4. The power supply device according to claim 3, wherein is below the rating.