JPH09215328A - Switching power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the conversion efficiency by accumulating energy in an energy supplying means by input AC during a period while which it is determined that the voltage value of the input AC exceeds a reference voltage value and supplying energy accumulated in the energy supplying means to a power converter when it is determined that the voltage value of the input AC is lower than the reference voltage value. SOLUTION: A rectifying means 2 full-wave rectifies the AC input and then generates pulsating AC. The voltage value of the pulsating AC is compared with a reference voltage value by a voltage judging means 4 to determine whether the pulsating AC is higher or lower than the reference voltage. When it is determined that the pulsating AC exceeds the reference voltage, an accumulation and supply controlling means 6 supplies the pulsating AC to an energy supply means 5 for the period during which the pulsating AC exceeds the reference voltage. When it is determined that the pulsating AC is lower than the reference voltage, the accumulation and supply controlling means 6 supplies the energy accumulated in the energy supplying means 5 to a power converter 3. By this method, the conversion efficiency can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device provided with a power conversion means for converting an input alternating current into either alternating current or direct current by switching the input alternating current. The present invention also relates to a switching power supply device that supplies the energy stored in the energy supply means to the power conversion means when at least one of the comparison voltages generated based on the input alternating current is lower than the reference voltage.

[0002]

2. Description of the Related Art In recent years, various methods have been adopted in order to improve the input power factor (that is, effective current / average current) in a switching power supply device.
The one described in Japanese Patent Laid-Open No. 103468 is conventionally known. This switching power supply device 101 is shown in FIG.
As shown in 0, the diode bridge D _B , the inverter transformer T1, the transistor Q11, the capacitor C ₁ and the diodes D ₂ and D ₃ are provided.

In this switching power supply device 101, a diode bridge D that full-wave rectifies the voltage of the _AC power supply V _AC
During a period in which the pulsating AC voltage at the positive terminal of _B is higher than the voltage across the terminals of the capacitor C ₁ , the current i ₁ from the _AC power supply V _AC flows through the primary winding N ₁ of the inverter transformer T ₁ and Power the secondary winding of T ₁ . Further, during this period, the charging current i ₂ flows from the primary winding N ₃ to the capacitor C ₁ to charge the capacitor C ₁ . On the other hand, the diode bridge D in the positive terminal voltage between terminals lower than the voltage of the capacitor C ₁ of _B, the discharge from the capacitor C ₁ current i ₃ is the primary winding N
_Since it flows to the diode D ₂ through ₁ , the capacitor C
_The energy stored in ₁ supplies power to the converter circuit arranged on the secondary side of the inverter transformer T ₁ . As described above, in the switching power supply device 101, the input power factor is improved as compared with the capacitor input type rectifier circuit system or the like by making the period in which the current flows through the primary winding N ₁ as long as possible.

[0004]

However, the conventional switching power supply device 101 has the following problems. That is, in the switching power supply device 101, the charging voltage of the capacitor C ₁ is originally set to the operation guarantee minimum voltage Va of the converter circuit, and the pulsating current AC voltage is lower than the operation guarantee minimum voltage Va of the converter circuit. It is preferable that the discharge is started from the moment and the discharge is stopped when the pulsating current AC voltage returns to the operation guarantee minimum voltage Va. However, the voltage across the terminal of the capacitor C ₁ gradually decreases during discharging. Therefore, in order for the capacitor C ₁ to keep the inter-terminal voltage at the voltage Va or higher until the pulsating current AC voltage decreases from the maximum value Vp to the operation guarantee voltage Va, the inter-terminal voltage at the start of discharge is It is necessary to have a voltage V1 that is higher than the voltage Va and that is equal to the pulsating current AC voltage at that time. As a result, the capacitor C ₁ has to store extra energy as much as it is discharged from the voltage V1 higher than the operation guarantee minimum voltage Va at which the converter operation can be sufficiently performed by the pulsating current AC power. There is a point.

Further, when the voltage V1 which is the charging voltage of the capacitor C ₁ is set to a high voltage, the energy accumulated in the capacitor C ₁ increases, but the energy released additionally also increases. Therefore, in this case, a large capacity capacitor is required. On the other hand, when the voltage V1 is set to a low voltage, the amount of energy stored in the capacitor having the same capacity decreases. In other words, the amount of energy E accumulated in the capacitor C ₁ has the following formula, is represented by E = CV ^2/2, because the V in this case corresponds to the inter-terminal voltage, a small value of the voltage between the terminals Then, only a small amount of energy can be accumulated in proportion to the square of the value. Therefore, in order to store the amount of energy required for preventing the output voltage of the converter circuit from decreasing in the capacitor C ₁ , a large capacity capacitor must be used. Thus, the conventional switching power supply device 101
Has a problem in that it requires a large capacity regardless of whether the charging voltage V ₁ is high or low, resulting in an increase in size and cost of the device.

Further, the stored energy of the capacitor C ₁ flows to the primary winding N ₁ of the inverter transformer T ₁ ,
Since the cycle of being stored again in the capacitor C ₁ is repeated, there is a large energy loss, which causes a problem that the conversion efficiency of the switching power supply device as a whole is lowered.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a switching power supply device capable of reducing the size and cost of the device and improving the conversion efficiency. The main purpose.

[0008]

In order to achieve the above object, a switching power supply device according to claim 1 is a power conversion means for converting input AC into either AC or DC by switching the input AC. In a switching power supply device including an energy supply unit that supplies energy to the power conversion unit when the AC voltage is lower than a predetermined voltage, at least a voltage value of the input AC and a comparison voltage generated based on the input AC. A voltage value determining means for determining whether one of the voltage levels exceeds or decreases the reference voltage;
Energy is accumulated by the input alternating current to the energy supply means within the period determined to be exceeded by the voltage value determination means, and is also accumulated in the energy supply means when it is determined to be lowered by the voltage value determination means. Storage and supply control means for supplying the stored energy to the power conversion means. In this case, the voltage value of the input AC and the comparison voltage generated based on the input AC are represented by (k · A ± l) as a general formula when the voltage value of the input AC is A. It is indicated by a voltage value. However, k and l indicate a proportional constant and a superimposed voltage, respectively. Further, the reference voltage includes, of course, a preset fixed reference voltage, and also includes a reference voltage that varies in proportion to the voltage value of the input AC.

In this switching power supply device, the accumulating and supplying means determines within a period that the voltage value determining means determines that at least one of the voltage value of the input AC and the comparison voltage generated based on the input AC exceeds the reference voltage. Since energy is stored in the energy supply means, the energy stored in the energy supply means can be stored up to the maximum value of the voltage value of the input AC. In this case, for example, when a capacitor is used as the energy supply means, the amount of stored energy increases in proportion to the square of the voltage across the terminals of the capacitor, so that a sufficiently large amount of energy can be stored. As a result, a small capacity capacitor can be used. Moreover, since the energy supply means supplies the stored energy to the power conversion means only when necessary, it is not necessary to store excess energy, and a capacitor having a smaller capacity can be used. Further, by storing the input alternating current directly in the energy supply means, the circulation of energy is prevented, and as a result, it is possible to use a capacitor having a smaller capacity.

According to another aspect of the switching power supply device of the present invention,
In the switching power supply device according to claim 1, the power conversion means includes a switching transformer, and the storage and supply control means stores energy in the energy supply means via the winding of the switching transformer. The transformer in this case is a concept including not only a so-called switching transformer used in the case of the forward method but also a transformer functioning as an inductance used in the case of the so-called flyback method.

According to another aspect of the switching power supply device of the present invention,
In the switching power supply device according to a second aspect of the invention, the energy is energy based on a voltage obtained by superposing the winding voltage of the switching transformer on the input AC voltage.

In the switching power supply device according to the second and third aspects, energy is stored in the energy supply means through the winding of the switching transformer. in this case,
If the energy based on the voltage obtained by superposing the winding voltage on the input AC voltage is stored in the energy supply means, for example, when a capacitor is used as the energy supply means, the value of the voltage between the terminals is increased. As a result, it becomes possible to store a larger amount of energy.

According to a fourth aspect of the switching power supply device,
In the switching power supply device according to claim 2 or 3, the switching transformer is provided with an auxiliary winding for supplying control power to the storage and supply control means.

In this switching power supply device, the energy stored in the auxiliary winding normally provided in the switching transformer is used as the control power supply for the storage and supply control means. Therefore, the power supply for control of the storage and supply control means can be configured without increasing the cost.

According to a fifth aspect of the switching power supply device,
The switching power supply device according to any one of claims 1 to 4, wherein the storage and supply control means includes an inrush current blocking means for blocking an inrush current to the energy supply means when the power is turned on. To do.

In this switching power supply device, for example,
When a capacitor is used as the energy supply means, a rush current flows through the capacitor when the power is turned on, but the rush current blocking means blocks the rush current. Therefore, for example, it is not necessary to provide the inrush current blocking means in the main power supply line of the switching power supply device. Also,
In this case, since the capacity of the capacitor can be reduced, it is not necessary to block a large inrush current as the inrush current blocking means, so that the inrush current can be blocked with a simple configuration.

According to a sixth aspect of the switching power supply device,
The switching power supply device according to any one of claims 1 to 5, wherein the storage / supply control unit includes a triac, and the triac is operated to accumulate energy in the energy supply unit and store the energy in the energy supply unit. It is characterized in that energy is supplied to the power conversion means.

In this switching power supply device, the storage / supply means controls both the storage of energy in the energy supply means and the supply of energy from the energy supply means to the power conversion means by the triac. Therefore, since the energy can be stored and supplied by one element, the cost of the device can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a switching power supply according to the present invention will be described below with reference to the accompanying drawings.

First, the operating principle of the switching power supply device according to the present invention will be described with reference to FIG. As shown in the figure, the switching power supply device 1 includes a rectification unit 2, a power conversion unit 3, a voltage value determination unit 4, an energy supply unit 5, and a storage supply control unit 6. An example in which a capacitor is used as the energy supply means 5 in the figure will be described below.

In this switching power supply device 1, for example, a rectifying means 2 composed of a diode bridge or the like.
But by full-wave rectifying an AC input, the maximum voltage value (corresponding to the input AC of the present invention) ripple AC is V _p, as shown in FIG. 2 to generate the V _rip. On the other hand, a reference voltage Vr (see the same figure) is set in the voltage value determination means 4, and the voltage value determination means 4 compares the voltage value of the pulsating current AC _{Vrip with} the voltage value of the reference voltage Vr. Pulsating current exchange V _rip
Is above or below the reference voltage Vr. Specifically, as shown in FIG. 3, time a1 to a2, a3 to a
4, a5 to a6, a7 to a8, the voltage value determination unit 4
Determines that the pulsating current AC _Vrip exceeds the reference voltage Vr. In this period, the storage / supply control unit 6 stores energy by charging the pulsating flow alternating current _Vrip in the energy supply unit 5. In this case, the energy supply means 5 has the maximum charging voltage when the pulsating current AC _Vrip reaches the maximum value Vp, as shown in FIG.
Times a1 to b1, a3 to b2, a5 to b3, a7 to b4
Only when it is charged. This period (time a1 to a2, a
The voltages across the capacitors 3 to a4, a5 to a6, a7 to a8) have the waveforms shown in FIG. During this period, the power conversion means 3 inputs the pulsating current AC V _rip from the rectification means 2 and performs switching to convert the power to DC or AC.

On the other hand, time a2 to a3, a4 to a5, a6
When ~a7 the voltage value determining means 4 determines that the ripple AC V _rip is lower than the reference voltage Vr, and outputs a voltage drop signal S1 to the storage supply control means 6. The storage and supply control unit 6 supplies the energy stored in the energy supply unit 5 to the power conversion unit 3 when the voltage drop signal S1 is input. As a result, the input voltage of the power conversion means 3 has a waveform as shown in FIG. in this case,
The allowable fluctuation range of the input voltage in the power conversion means 3 is set to the reference voltage Vr to Vp (or Vp or more),
Thereby, the voltage conversion means 3 can stabilize the power output value to a predetermined value during the entire period of one cycle of the pulsating current AC _Vrip .

As described above, in this embodiment, energy is accumulated in the energy supply means 5 when the pulsating current V _rip exceeds the minimum voltage of the fluctuation allowable range of the power conversion means 3, and during this time, the energy supply means is supplied. No energy is released from 5. Therefore, for example, when a capacitor is used as the energy supply means 5, the voltage based on the energy (charge) accumulated in the capacitor reaches the maximum value Vp of the pulsating current _Vrip , and therefore, in the above formula of energy amount. As a result of the value of V becoming larger than that of the conventional switching power supply device 101, its energy amount also becomes large. Therefore, energy can be efficiently stored in the small-capacity capacitor, so that the device can be downsized and the cost can be reduced. Further, since the energy supply means 5 supplies energy to the power conversion means 3 only during a period of time equal to or lower than the minimum voltage within the fluctuation allowable range of the power conversion means 3, no extra stored energy is required and a smaller capacity is required. A capacitor can be used. Furthermore, since the amount of energy stored in the capacitor is the minimum necessary,
The charging current for storing energy may be small.

Further, unlike the conventional switching power supply device, there is no energy circulation in which the energy supplied to the power conversion means 3 is supplied again to the energy supply means 5, so that a switching transformer is used for the power conversion means 5, for example. In this case, the capacities of the switching element and the switching transformer as the power conversion means 3 can be reduced, and the power conversion efficiency of the entire device can be improved. Furthermore, since there is no energy circulation, when a capacitor is used as the energy supply means 5, a smaller capacity type can be used. However, in the present invention, it is not a requirement to prevent the circulation of energy, and even if there is circulation, the amount of energy accumulated in the energy supply means 5 can be reduced, and the device can be downsized and the cost can be reduced. Can be achieved.

Next, a specific configuration of the switching power supply device according to the present invention will be described.

(Embodiment 1) FIG. 6 is a diagram in which the switching power supply device 1 in FIG. 1 is configured as a so-called flyback converter type power supply device. First, the correspondence between the components in both figures is shown below. As shown in FIG. 6, the diode bridge 11 and the diodes 12, 1
3 corresponds to the rectifying means 2, resistors 14, 15 and FE
T16 corresponds to the voltage value determination means 4. Also, FET2
1, transistor 22, resistors 23 and 24, diode 2
5 and the capacitor 26 correspond to the storage and supply control means 6, the capacitor 30 corresponds to the energy supply means 5,
Transformer 31, switching circuit 32, diode 33
And the capacitor 34 corresponds to the power conversion means 3.

In this switching power supply device 1, the allowable fluctuation range of the input voltage in the power conversion means 3 such as the switching circuit 32 is set to the reference voltage Vr to Vp (or Vp or more). Under such conditions, when an alternating current is input from the external alternating current power supply 41, the diode bridge 11 and the diodes 12, 13 perform full-wave rectification of the alternating current, so that the maximum voltage value as shown in FIG. Generates a pulsating flow alternating current that is _p . Meanwhile, FE
T16 is, when the pulsating current AC voltage value is the reference voltage Vr,
The drain current is caused to flow by operating the pulsating alternating current with a voltage value that is resistance-divided by the resistors 14 and 15.

When the FET 16 is operating, that is, when the pulsating current AC has a voltage value higher than the reference voltage Vr, the transistor 22 operates to bring the source and the gate of the FET 21 to the same potential, which causes the FET 21 to operate. It is turned off. In this state, FET21
The presence of the internal parasitic diode equivalently constitutes a diode in which a forward current flows from the source to the drain. For this reason, the FET 21 causes the pulsating alternating current to flow into the capacitor 30 and
Is charged to the maximum value Vp of the pulsating alternating current, and the discharge is prevented to keep the voltage across the terminals of the capacitor 30 at the maximum value Vp. On the other hand, the switching circuit 32 is, for example, 5
Switching at 0 KHz causes a pulsating alternating current to flow into the primary coil 31a of the transformer 31, which causes a current I ₁₁ to flow in the secondary coil 31b when the switching circuit 32 is off, thereby reducing the load R _L. A DC current stabilized to a predetermined voltage is supplied to. When the switching is off, the energy stored in the transformer 31 is output to the anode side of the diode 25 via the terminal 31c and rectified by the diode 25 and the capacitor 26 to serve as a control power supply.

When the FET 16 is not operating, that is, when the pulsating current AC is lower than the reference voltage Vr, the operation of the transistor 22 is stopped and the FET 21 is stopped.
The control power source from the capacitor 26 is applied to the gate of the FET, and the FET 21 is activated. In this state, FE
At T21, since the source and the drain are in a conductive state,
The electric charge accumulated in the capacitor 30 is supplied to the primary coil 31a of the transformer 31 according to the switching of the switching circuit 32.

As described above, in the switching power supply device 1 of this embodiment, the voltage value of the pulsating current AC is the reference voltage Vr.
When it is higher than the above, the pulsating current from the diode bridge 11 is supplied to the transformer 31 and the capacitor 30
When the voltage value of the pulsating current AC drops below the reference voltage Vr, the electric charge accumulated in the capacitor 30 is supplied to the transformer 31. Therefore, the AC power supply 41
In one cycle of, the power conversion means 3 can supply the DC power stabilized to a predetermined voltage value to the load R _L. Further, since the capacitor 30 is charged and held up to the maximum value Vp of the pulsating flow alternating current, an extremely large amount of energy can be stored, and as a result, a small capacity capacitor can be used.

Specifically, for example, the AC power supply 41 is a 50 Hz sine wave of AC 90 V to 110 V, and the DC power that can output the power conversion means 3 is 20 W.
In addition, if the operation guarantee minimum voltage (reference voltage Vr) is 50 V and there is no loss in each part, the switching power supply device 1
(Shown as type A in the table below), capacitor input type switching power supply device (shown as type B in the table below), and switching power supply device 101.
The performance of (in the table below, types with voltage V1 of 121V, 110V and 64V are shown as C, D and E, respectively) is shown in the table below.

Type A Type B Type C Type D Type E ・ Capacitor capacity as energy supply means 7.5 μF 18 μF 18 μF 19 μF 76 μF ・ Supply time from capacitor (half cycle) 2.58 mS 6.29 mS 5.29 mS 4.62 mS 2.96 mS ・Supply from capacitor (half cycle) 52mJ 120mJ 106mJ 92mJ 59mJ ・ Circulating power 0W 0W 10.6W 9.2W 5.9W

As shown in the above table, the switching power supply 1 is compared with the conventional capacitor input type switching power supply or the switching power supply 101.
A small-capacity type can be used as the capacitor 30, and in that case, a large amount of energy can be discharged from the capacitor 30. As a result of being able to increase the charging voltage, the capacitor 30 must be of a type having a higher breakdown voltage than the switching power supply device 101. However, considering the fact that the energy that can be stored is proportional to the square of the charging voltage V, the increase in the price and size of the capacitor 30 due to the increase in the withstand voltage is different from the capacitor used in the conventional switching power supply device 101. Much smaller in comparison. In addition,
Although the output power of the power conversion means 3 is set to 20 W in the above table, it goes without saying that the output power of the switching power supply device 1 becomes smaller and the cost of the switching power supply device 1 becomes more remarkable.

As shown in the figure, a diode 27 may be arranged between the intermediate tap 31d of the primary winding of the transformer 31 and the positive side of the capacitor 30. In this case, the voltage charged in the capacitor 30 is, as shown in FIG. 5, the primary coil 3 with respect to the maximum value Vp of the pulsating current AC.
It increases by the voltage value ΔV boosted by 1a. Therefore, the capacitor 30 can store a larger amount of energy, and can be further downsized. In this case, energy circulation occurs in which energy is stored in the capacitor 30 from the capacitor 30 via the primary coil 31a of the transformer 31, but even in such a case, comparison with the conventional switching power supply device 101 is required. Therefore, the capacitor 30 can be downsized.

Further, in this embodiment, since the pulsating current AC is resistance-divided by the resistors 14 and 15, even if the voltage value of the pulsating current AC is lower than the reference voltage Vr, a slight voltage is applied to the gate of the FET 16. Is applied. For this reason, on / off of the FET 16 may not be reliably controlled. In such a case, by disposing a Zener diode between the connection point between the cathodes of the diodes 12 and 13 and the resistor 14, it is possible to reliably control the ON / OFF of the FET 16. Further, the FET 16 and the transistor 2
The ON / OFF of the FET 21 is controlled by means of 2, but in this case, it is necessary to use a high breakdown voltage type FET 16. To improve this point, F
If a photodiode of a photocoupler is used instead of the ET16 and a phototransistor is used to control the gate voltage of the FET 21, without using a high breakdown voltage element,
The on / off of the FET 21 can be surely controlled.

(Embodiment 2) Next, referring to FIG.
An example will be described. This switching power supply device 51 differs from the switching power supply device 1 in the first embodiment in that the power supply of the storage / supply control means 6 is a transformer 52.
Is obtained from the auxiliary winding and the reference voltage Vr is a voltage value obtained by reducing the instantaneous voltage value of the pulsating current AC by a predetermined voltage value. The figure shows a configuration corresponding to the output terminal of the diode bridge 11 in FIG. 6 to the primary coil of the transformer 31. Further, the components shown in FIG. The same reference numerals are used and detailed description thereof is omitted.

In this switching power supply device 51, the energy stored in the auxiliary coil 52b of the transformer 51 when the switching of the switching circuit 32 is on is
Emitted when switching off, diode 25
The capacitor 26 serves as a power supply for controlling the FET 21 and the transistor 53 as the storage / supply control means 6. The auxiliary coil 52b is usually included in the switching transformer, and therefore the cost increase due to the adoption of the auxiliary coil 52b is not caused.

In the switching power supply device 51, in the initial state, no electric charge is stored in the capacitors 30 and 54. Therefore, when the pulsating current AC is input, the pulsating current AC is input to the capacitors 30 and 54 via the parasitic diode of the FET 21. Flows, the capacitors 30 and 54 are charged to the maximum value Vp of the pulsating current AC. On the other hand, when the voltage of the pulsating current AC falls below the maximum value Vp, the FET 21 is reverse biased between its drain and source and is turned off. Further, by setting the Zener voltage of the Zener diode 56 to a predetermined voltage value, the transistor 53 is maintained in the off state, and as a result, the gate voltage is not applied to the FET 21 even through the resistor 57. In this state, capacitors 30, 54
Holds its charge voltage.

On the other hand, when the instantaneous value of the pulsating current AC drops from the maximum value by a predetermined voltage value (corresponding to the case where the instantaneous voltage value of the pulsating current AC reaches the reference voltage Vr in FIG. 2), the base of the transistor 53. The current is the Zener diode 56
To the capacitor 54 via the zener diode 56 and the diode 55.
It flows in the route to. Therefore, the transistor 53 operates, the gate voltage is applied to the gate of the FET 21, and the FET 21 enters the operating state. As a result, the electric charge accumulated in the capacitor 30 flows as the current I ₁₂ shown in the figure and is supplied to the primary coil 52a of the transformer 52. Thereby, the same effect as the switching power supply device 1 in FIG. 6 is exhibited.

(Embodiment 3) Next, referring to FIG.
An example will be described. This switching power supply device 61 is basically different from the switching power supply devices 1 and 51 in the first and second embodiments in that a triac is used for the storage and supply control means 6 and an inrush current to the capacitor 30 when the power is turned on. Is the point that is blocking. It should be noted that the figure shows the diode bridge 1 in FIG.
1 shows the configuration from the output terminal of 1 to the primary coil of the transformer 31, and the same reference numerals are used for the same components shown in FIG. 8 and FIG. 7, and detailed description thereof will be given. Omit it.

In this switching power supply device 61, when the capacitor 30 is initially charged, the capacitor 3
Since a pulsating alternating current flows through the 0, the diode 62 and the resistor 63 to the 0V line, the resistor 63 prevents the initial inrush of current and accumulates electric charges to some extent in the capacitor 30. In this state, the switching circuit 32
When the switching operation is started and a voltage is generated in the winding 52b of the transformer 52, the voltage generated across the resistor 63 causes the transistor 64 to operate, so that the transistor 53 also operates. As a result, the emitter current of the transistor 53 flows and a voltage is applied to the gate of the triac 65. Next, Triac 65
Is conducted, a charging current flows through the capacitor 30, and the capacitor 30 is charged and held to the maximum value Vp of the pulsating current AC. On the other hand, when the capacitor 30 is charged to the maximum value Vp, the current flowing through the capacitor 30 becomes triac 6.
As a result, the triac 65 is automatically turned off.

Next, when the instantaneous voltage value of the pulsating alternating current falls below the reference voltage Vr, the base current of the transistor 53 flows into the capacitor 30 via the resistor 65, the diode 66 and the zener diode 56. As a result, a gate voltage is applied to the gate of the triac 65 via the emitter of the transistor 53 and the resistor 57,
The triac 65 becomes conductive. As a result, the electric charge accumulated in the capacitor 30 flows as a current I ₁₃ shown in the figure and is supplied to the primary coil 52a of the transformer 52.
Thereby, the same effect as the switching power supply device 1 in FIG. 6 is exhibited.

As described above, in this embodiment, by using the inexpensive triac 65, both charging and discharging of the capacitor 30 can be controlled at a low cost. Moreover, by selecting the resistance value of the resistor 63, the value of the inrush current can be freely set.

(Embodiment 4) Next, referring to FIG.
An example will be described. This switching power supply device 71 is the switching power supply device 61 in the third embodiment.
What is basically different from this is that the function of blocking the inrush current to the capacitor 30 when the power is turned on is deleted to simplify the configuration. The same components in FIG. 8 as those in FIG. 8 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this switching power supply device 71, when the power is turned on, the pulsating current AC is applied to the gate of the triac 65 via the capacitor 30, the diode 62 and the resistor 63, so that the triac 65 becomes conductive. Therefore, the triac 65 flows through the capacitor 30 and is charged. At the time of discharging, the current ₁₄ flows in the same path as the current ₁₃ in FIG. 8 to supply energy to the primary coil of the transformer 52.

As described above, in this embodiment, charging / discharging of the capacitor 30 can be controlled with a very simple structure. Further, since the control circuit for accumulating and discharging the charge to and from the capacitor 30 is simplified, the power used for control can be reduced, and as a result, the conversion efficiency of the device can be improved.

Although the FETs or triacs are used to control the charging of the capacitor 30 in the first to fourth embodiments, the present invention is not limited to this, and as the storage and supply control means in the present invention, Switch elements such as transistors and thyristors can be used. Furthermore, although the configuration of the flyback type switching power supply device has been described in the above embodiment, the present invention is not limited to this, and the present invention can be applied to a forward type switching power supply device. Further, the power conversion means 3 can be configured as a constant voltage power supply, a constant current power supply, and a constant power power supply.

In the above embodiment, the capacitor 30 is compared by comparing the voltage value of the pulsating current AC with the reference value.
However, the present invention is not limited to this, and comparing one or both of the voltage value of the pulsating current AC and the comparison voltage generated based on the pulsating current AC with the reference value. The charge and discharge can be controlled by. As the comparison voltage in this case, the pulsating current AC voltage value is A
In this case, the voltage represented by (k · A ± l) can be used as a general formula (where k and l represent a proportional constant and a superimposed voltage, respectively). In particular,
The voltage value (k · A) means a voltage obtained by boosting the pulsating flow alternating current by k times, and the voltage (k · A + 1) means a voltage obtained by superposing the voltage 1 on the voltage obtained by boosting the pulsating current alternating current by k times. The reference voltage includes not only a preset fixed reference voltage but also a reference voltage that varies in proportion to the pulsating current AC voltage value. Specifically, the comparison voltage (k · A) is changed to the voltage (k ₁ · A) (where k ₁ means a proportional constant).
This is the case when comparing with.

[0049]

As described above, according to the switching power supply device of the first aspect, for example, when a capacitor is used as the energy supplying means, the stored energy amount is proportional to the square of the voltage between the terminals of the capacitor. As a result, a sufficiently large energy can be stored, and as a result, a small capacity capacitor can be used. Further, the energy supply means does not store extra energy and can use a capacitor having a smaller capacity. Furthermore, by storing the input alternating current directly in the energy supply means, energy circulation is prevented, so that a capacitor with a smaller capacity can be used.

Further, according to the switching power supply device of the second and third aspects, if the energy based on the voltage obtained by superposing the winding voltage on the input AC voltage is accumulated in the energy supply means, for example, the energy supply means. When a capacitor is used as the result, the value of the voltage between the terminals can be made larger, and as a result, it becomes possible to store a larger amount of energy and a small capacity capacitor can be used.

Further, according to the switching power supply device of the fourth aspect, it is possible to configure the control power supply of the storage and supply control means without increasing the cost.

According to the switching power supply device of the fifth aspect, it is possible to eliminate the need for the inrush current blocking means normally provided in the main power supply line of the switching power supply device. Further, in this case, since the capacitance of the capacitor can be reduced, it is possible to prevent the inrush current with a simple configuration.

Further, according to the switching power supply device of the sixth aspect, since the storage and supply of energy can be controlled together by the inexpensive triac, the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a switching power supply device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of a pulsating flow alternating current generated in the switching power supply device according to the embodiment of the present invention.

FIG. 3A is a signal waveform diagram of a pulsating flow AC for explaining accumulation and supply of energy to an energy supply unit in the present embodiment, and FIG. 3B is a signal waveform diagram of a voltage drop signal. .

FIG. 4A is a signal waveform diagram for explaining a period for charging a capacitor as an energy supply unit in the present embodiment, and FIG. 4B is a signal waveform diagram of a voltage between terminals of the capacitor, c) is a signal waveform diagram of the power supplied to the power conversion means.

FIG. 5 is a signal waveform diagram of electric power supplied to a transformer according to a modification of the first embodiment.

FIG. 6 is a circuit diagram of the switching power supply device according to the first embodiment.

FIG. 7 is a circuit diagram of a switching power supply device according to a second embodiment.

FIG. 8 is a circuit diagram of a switching power supply device according to a third embodiment.

FIG. 9 is a circuit diagram of a switching power supply device according to a fourth embodiment.

FIG. 10 is a circuit diagram of a conventional switching power supply device.

FIG. 11 is a signal waveform diagram of a voltage between terminals of a capacitor in a conventional switching power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching power supply device 3 Power conversion means 4 Voltage value determination means 5 Energy supply means 6 Storage and supply control means 16 FET 21 FET 22 Transistor 30 Capacitor 31 Transformer 51 Switching power supply device 52b Auxiliary coil 53 Transistor 61 Switching power supply device 63 Resistance 65 Triac

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[Procedure amendment]

[Submission date] February 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Title of the invention: Switching power supply device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device provided with a power conversion means for converting an input alternating current into either alternating current or direct current by switching the input alternating current. The present invention also relates to a switching power supply device that supplies the energy stored in the energy supply means to the power conversion means when at least one of the comparison voltages generated based on the input alternating current is lower than the reference voltage.

[0002]

2. Description of the Related Art In recent years, various methods have been adopted in order to improve the input power factor (that is, effective current / average current) in a switching power supply device.
The one described in Japanese Patent Laid-Open No. 103468 is conventionally known. This switching power supply device 101 is shown in FIG.
As shown in FIG. 3, it includes a diode bridge D _B , an inverter transformer T1, a transistor Q11, a capacitor C ₁ and diodes D ₂ and D ₃ .

In this switching power supply device 101, a diode bridge D that full-wave rectifies the voltage of the _AC power supply V _AC
During a period in which the pulsating voltage at the positive terminal of _B is higher than the voltage between the terminals of the capacitor C ₁ , the current i from the _AC power supply V _AC
1 supplies electric power to the secondary winding of the inverter transformer T ₁ flows through the primary winding N ₁ of the inverter transformer T _1.
Further, during this period, the charging current i ₂ flows from the primary winding N ₃ to the capacitor C ₁ to charge the capacitor C ₁ . On the other hand, the diode bridge D in the positive terminal voltage between terminals lower than the voltage of the capacitor C ₁ of _B, the discharge from the capacitor C ₁ current i ₃ is the primary winding N ₁
Through the diode D ₂ through the capacitor C ₁
Electric power is supplied to the converter circuit arranged on the secondary side of the inverter transformer T ₁ by the energy stored in. As a result, the inter-terminal voltage of the capacitor C ₁ varies between the operation-guaranteed minimum voltage Va and the predetermined voltage V ₁ , as shown in FIG. As described above, in the switching power supply device 101, the input power factor is improved as compared with the capacitor input type rectifier circuit system or the like by making the period in which the current flows through the primary winding N ₁ as long as possible.

[0004]

However, the conventional switching power supply device 101 has the following problems. That is, the switching power supply device 101 is essentially configured such that the charging voltage of the capacitor C ₁ is set to the minimum operation guarantee voltage Va of the converter circuit and the pulsating current voltage is lower than the minimum operation guarantee voltage Va of the converter circuit. It is preferable that the discharge is started from and the discharge is stopped when the pulsating voltage returns to the operation guarantee minimum voltage Va. However, the voltage across the terminal of the capacitor C ₁ gradually decreases during discharging. Therefore, in order for the capacitor C ₁ to keep the terminal voltage at or above the voltage Va until the pulsating voltage drops from the maximum value Vp to the operation guarantee minimum voltage Va, the terminal voltage at the start of discharge is It is necessary that the voltage be equal to the pulsating current voltage at that time and that the voltage V1 be higher than the voltage Va. As a result, the capacitor C ₁ has to store extra energy as much as it is discharged from the voltage V 1 higher than the operation guarantee minimum voltage Va at which the converter can operate sufficiently with pulsating current power. There is.

Further, when the voltage V1 which is the charging voltage of the capacitor C ₁ is set to a high voltage, the energy accumulated in the capacitor C ₁ increases, but the energy released additionally also increases. Therefore, in this case, a large capacity capacitor is required. On the other hand, when the voltage V1 is set to a low voltage, the amount of energy stored in the capacitor having the same capacity decreases. In other words, the amount of energy E accumulated in the capacitor C ₁ has the following formula, is represented by E = CV ^2/2, because the V in this case corresponds to the inter-terminal voltage, a small value of the voltage between the terminals Then, only a small amount of energy can be accumulated in proportion to the square of the value. Therefore, in order to store the amount of energy required for preventing the output voltage of the converter circuit from decreasing in the capacitor C ₁ , a large capacity capacitor must be used. Thus, the conventional switching power supply device 101
Has a problem in that it requires a large capacity regardless of whether the charging voltage V ₁ is high or low, resulting in an increase in size and cost of the device.

Further, the stored energy of the capacitor C ₁ flows to the primary winding N ₁ of the inverter transformer T ₁ ,
Since the cycle of being stored again in the capacitor C ₁ is repeated, there is a large energy loss, which causes a problem that the conversion efficiency of the switching power supply device as a whole is lowered.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a switching power supply device capable of reducing the size and cost of the device and improving the conversion efficiency. The main purpose.

[0008]

In order to achieve the above object, a switching power supply device according to claim 1 is a power conversion means for converting input AC into either AC or DC by switching the input AC. In a switching power supply device including an energy supply unit that supplies energy to the power conversion unit when the AC voltage is lower than a predetermined voltage, at least a voltage value of the input AC and a comparison voltage generated based on the input AC. A voltage value determining means for determining whether one of the voltage levels exceeds or decreases the reference voltage;
Energy is accumulated by the input alternating current to the energy supply means within the period determined to be exceeded by the voltage value determination means, and is also accumulated in the energy supply means when it is determined to be lowered by the voltage value determination means. Storage and supply control means for supplying the stored energy to the power conversion means. In this case, the voltage value of the input AC and the comparison voltage generated based on the input AC are represented by (k · A ± l) as a general formula when the voltage value of the input AC is A. It is indicated by a voltage value. However, k and l indicate a proportional constant and a superimposed voltage, respectively. Further, the reference voltage includes, of course, a preset fixed reference voltage, and also includes a reference voltage that varies in proportion to the voltage value of the input AC. The input alternating current in the present invention is a concept including not only general alternating current but also pulsating current which is generally defined as direct current.

In this switching power supply device, the accumulating and supplying means determines within a period that the voltage value determining means determines that at least one of the voltage value of the input AC and the comparison voltage generated based on the input AC exceeds the reference voltage. Since energy is stored in the energy supply means, the energy stored in the energy supply means can be stored up to the maximum value of the voltage value of the input AC. In this case, for example, when a capacitor is used as the energy supply means, the amount of stored energy increases in proportion to the square of the voltage across the terminals of the capacitor, so that a sufficiently large amount of energy can be stored. As a result, a small capacity capacitor can be used. Moreover, since the energy supply means supplies the stored energy to the power conversion means only when necessary, it is not necessary to store excess energy, and a capacitor having a smaller capacity can be used. Further, by storing the input alternating current directly in the energy supply means, the circulation of energy is prevented, and as a result, it is possible to use a capacitor having a smaller capacity.

According to another aspect of the switching power supply device of the present invention,
In the switching power supply device according to claim 1, the power conversion means includes a switching transformer, and the storage and supply control means stores energy in the energy supply means via the winding of the switching transformer. The transformer in this case is a concept including not only a so-called switching transformer used in the case of the forward method but also a transformer functioning as an inductance used in the case of the so-called flyback method.

According to another aspect of the switching power supply device of the present invention,
In the switching power supply device according to a second aspect of the invention, the energy is energy based on a voltage obtained by superposing the winding voltage of the switching transformer on the input AC voltage.

In the switching power supply device according to the second and third aspects, energy is stored in the energy supply means through the winding of the switching transformer. in this case,
If the energy based on the voltage obtained by superposing the winding voltage on the input AC voltage is stored in the energy supply means, for example, when a capacitor is used as the energy supply means, the value of the voltage between the terminals is increased. As a result, it becomes possible to store a larger amount of energy.

According to a fourth aspect of the switching power supply device,
In the switching power supply device according to claim 2 or 3, the switching transformer is provided with an auxiliary winding for supplying control power to the storage and supply control means.

In this switching power supply device, the energy stored in the auxiliary winding normally provided in the switching transformer is used as the control power supply for the storage and supply control means. Therefore, the power supply for control of the storage and supply control means can be configured without increasing the cost.

According to a fifth aspect of the switching power supply device,
The switching power supply device according to any one of claims 1 to 4, wherein the storage and supply control means includes an inrush current blocking means for blocking an inrush current to the energy supply means when the power is turned on. To do.

In this switching power supply device, for example,
When a capacitor is used as the energy supply means, a rush current flows through the capacitor when the power is turned on, but the rush current blocking means blocks the rush current. Therefore, for example, it is not necessary to provide the inrush current blocking means in the main power supply line of the switching power supply device. Also,
In this case, since the capacity of the capacitor can be reduced, it is not necessary to block a large inrush current as the inrush current blocking means, so that the inrush current can be blocked with a simple configuration.

According to a sixth aspect of the switching power supply device,
The switching power supply device according to any one of claims 1 to 5, wherein the storage / supply control unit includes a triac, and the triac is operated to accumulate energy in the energy supply unit and store the energy in the energy supply unit. It is characterized in that energy is supplied to the power conversion means.

In this switching power supply device, the storage / supply means controls both the storage of energy in the energy supply means and the supply of energy from the energy supply means to the power conversion means by the triac. Therefore, since the energy can be stored and supplied by one element, the cost of the device can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a switching power supply according to the present invention will be described below with reference to the accompanying drawings.

First, the operating principle of the switching power supply device according to the present invention will be described with reference to FIG. As shown in the figure, the switching power supply device 1 includes a rectification unit 2, a power conversion unit 3, a voltage value determination unit 4, an energy supply unit 5, and a storage supply control unit 6. An example in which a capacitor is used as the energy supply means 5 in the figure will be described below.

In this switching power supply device 1, for example, a rectifying means 2 composed of a diode bridge or the like.
But by full-wave rectifying an AC input, the maximum voltage value (corresponding to the input AC of the present invention) pulsating a V _p as shown in FIG. 2 to generate the V _rip. On the other hand, a reference voltage Vr (see the same figure) is set in the voltage value determination means 4, and the voltage value determination means 4 compares the voltage value of the pulsating current _{Vrip with} the voltage value of the reference voltage Vr. Ripple flow _Vrip is reference voltage V
It is determined whether r is exceeded or dropped. Specifically, FIG.
As shown in, time a1 to a2, a3 to a4, a5 to a
6, when the A7～a8, voltage value determination unit 4, pulsating V _rip
Is determined to exceed the reference voltage Vr. In this period, the storage / supply control unit 6 stores energy by charging the energy supply unit 5 with the pulsating flow V _rip . In this case, as shown in FIG. 4 (a), the energy supply means 5 has the maximum charging voltage when the pulsating flow V _rip reaches the maximum value Vp, so that the times a 1 to b 1 and a 3 to b are satisfied.
2, a5 to b3, a7 to b4 are charged only. This period (time a1 to a2, a3 to a4, a5 to a6, a
The voltage across the capacitors 7 to a8) has the waveform shown in FIG. During this period, the power conversion means 3
Inputs the pulsating flow V _rip from the rectifying means 2 and performs switching to convert the power into direct current or alternating current.

On the other hand, time a2 to a3, a4 to a5, a6
In the case of up to a7, the voltage value determination means 4 determines that the pulsating current V _rip is lower than the reference voltage Vr, and the voltage drop signal S.
1 is output to the storage / supply control means 6. The storage and supply control unit 6 supplies the energy stored in the energy supply unit 5 to the power conversion unit 3 when the voltage drop signal S1 is input. As a result, the input voltage of the power conversion means 3 has a waveform as shown in FIG. In this case, the allowable range of fluctuation of the input voltage in the power conversion means 3 is set to the reference voltage Vr～Vp (or more Vp), thereby, the voltage conversion unit 3, the total duration of one cycle of the pulsating V _rip In, the power output value can be stabilized at a predetermined value.

As described above, in this embodiment, energy is accumulated in the energy supply means 5 when the pulsating current V _rip exceeds the minimum voltage of the fluctuation allowable range of the power conversion means 3, and during this time, the energy supply means is supplied. No energy is released from 5. Therefore, for example, when a capacitor is used as the energy supply means 5, the voltage based on the energy (charge) accumulated in the capacitor reaches the maximum value Vp of the pulsating current _Vrip , and therefore, in the above formula of energy amount. As a result of the value of V becoming larger than that of the conventional switching power supply device 101, its energy amount also becomes large. Therefore, energy can be efficiently stored in the small-capacity capacitor, so that the device can be downsized and the cost can be reduced. Further, since the energy supply means 5 supplies energy to the power conversion means 3 only during a period of time equal to or lower than the minimum voltage within the fluctuation allowable range of the power conversion means 3, no extra stored energy is required and a smaller capacity is required. A capacitor can be used. Furthermore, since the amount of energy stored in the capacitor is the minimum necessary,
The charging current for storing energy may be small.

Further, unlike the conventional switching power supply device, there is no energy circulation in which the energy supplied to the power conversion means 3 is supplied again to the energy supply means 5, so that a switching transformer is used for the power conversion means 5, for example. In this case, the capacities of the switching element and the switching transformer as the power conversion means 3 can be reduced, and the power conversion efficiency of the entire device can be improved. Furthermore, since there is no energy circulation, when a capacitor is used as the energy supply means 5, a smaller capacity type can be used. However, in the present invention, it is not a requirement to prevent the circulation of energy, and even if there is circulation, the amount of energy accumulated in the energy supply means 5 can be reduced, and the device can be downsized and the cost can be reduced. Can be achieved.

Next, a specific configuration of the switching power supply device according to the present invention will be described.

(Embodiment 1) FIG. 6 is a diagram in which the switching power supply device 1 in FIG. 1 is configured as a so-called flyback converter type power supply device. First, the correspondence between the components in both figures is shown below. As shown in FIG. 6, the diode bridge 11 and the diodes 12, 1
3 corresponds to the rectifying means 2, resistors 14, 15 and FE
T16 corresponds to the voltage value determination means 4. Also, FET2
1, transistor 22, resistors 23 and 24, diode 2
5 and the capacitor 26 correspond to the storage and supply control means 6, the capacitor 30 corresponds to the energy supply means 5,
Transformer 31, switching circuit 32, diode 33
And the capacitor 34 corresponds to the power conversion means 3.

In this switching power supply device 1, the allowable fluctuation range of the input voltage in the power conversion means 3 such as the switching circuit 32 is set to the reference voltage Vr to Vp (or Vp or more). Under such conditions, when an alternating current is input from the external alternating current power supply 41, the diode bridge 11 and the diodes 12, 13 perform full-wave rectification of the alternating current, so that the maximum voltage value as shown in FIG. Generate each pulsating flow that is _p . On the other hand, FET1
When the voltage value of the pulsating current is the reference voltage Vr, 6 operates with a voltage value obtained by resistance-dividing the pulsating current with the resistors 14 and 15 to flow a drain current.

When the FET 16 is operating, that is, when the pulsating current has a voltage value higher than the reference voltage Vr, the transistor 22 operates to bring the source and gate of the FET 21 to the same potential, which turns off the FET 21. It is in a state. In this state, the FET 21 equivalently constitutes a diode in which a forward current flows from the source to the drain due to the presence of the internal parasitic diode. For this reason, the FET 21 charges the capacitor 30 to the maximum value Vp of the pulsating flow by pouring the pulsating current into the capacitor 30, and also prevents the discharge and holds the terminal voltage of the capacitor 30 at the maximum value Vp. On the other hand, the switching circuit 32 switches at 50 KHz, for example, and causes a pulsating current to flow into the primary side coil 31a of the transformer 31. As a result, in the secondary side coil 31b,
By supplying the current I ₁₁ when the switching of the switching circuit 32 is off, the DC current stabilized to a predetermined voltage is supplied to the load R _L. When the switching is off, the energy stored in the transformer 31 is output to the anode side of the diode 25 via the terminal 31c and rectified by the diode 25 and the capacitor 26 to serve as a control power supply.

When the FET 16 is not operating, that is, when the pulsating current is lower than the reference voltage Vr, the transistor 22 stops operating, and the control power source from the capacitor 26 is applied to the gate of the FET 21. F
ET21 is activated. In this state, FET21
Becomes conductive between the source and the drain, the charge accumulated in the capacitor 30 is transferred to the switching circuit 3
The primary coil 3 of the transformer 31 according to the switching of 2
Supply to 1a.

As described above, in the switching power supply device 1 in this embodiment, when the voltage value of the pulsating current is higher than the reference voltage Vr, the pulsating current from the diode bridge 11 is supplied to the transformer 31 and the capacitor 30 is charged. , When the voltage value of the pulsating current becomes lower than the reference voltage Vr, the electric charge accumulated in the capacitor 30 is transferred to the transformer 3
1 to supply. Therefore, in one cycle of the AC power supply 41, the power conversion means 3 can supply the DC power stabilized to a predetermined voltage value to the load _RL . Further, since the capacitor 30 is charged and held up to the maximum value Vp of the pulsating flow, an extremely large amount of energy can be stored, and as a result, a capacitor having a small capacity can be used.

Specifically, for example, the AC power supply 41 is a 50 Hz sine wave of AC 90 V to 110 V, and the DC power that can output the power conversion means 3 is 20 W.
In addition, if the operation guarantee minimum voltage (reference voltage Vr) is 50 V and there is no loss in each part, the switching power supply device 1
(Shown as type A in the table below), capacitor input type switching power supply device (shown as type B in the table below), and switching power supply device 101.
The performance of (in the table below, types with voltage V1 of 121V, 110V and 64V are shown as C, D and E, respectively) is shown in the table below.

Type A Type B Type C Type D Type E ・ Capacitor capacity as energy supply means 7.5 μF 18 μF 18 μF 19 μF 76 μF ・ Supply time from capacitor (half cycle) 2.58 mS 6.29 mS 5.29 mS 4.62 mS 2.96 mS ・Supply from capacitor (half cycle) 52mJ 120mJ 106mJ 92mJ 59mJ ・ Circulating power 0W 0W 10.6W 9.2W 5.9W

As shown in the above table, the switching power supply 1 is compared with the conventional capacitor input type switching power supply or the switching power supply 101.
A small-capacity type can be used as the capacitor 30, and in that case, a large amount of energy can be discharged from the capacitor 30. As a result of being able to increase the charging voltage, the capacitor 30 must be of a type having a higher breakdown voltage than the switching power supply device 101. However, considering the fact that the energy that can be stored is proportional to the square of the charging voltage V, the increase in the price and size of the capacitor 30 due to the increase in the withstand voltage is different from the capacitor used in the conventional switching power supply device 101. Much smaller in comparison. In addition,
Although the output power of the power conversion means 3 is set to 20 W in the above table, it goes without saying that the output power of the switching power supply device 1 becomes smaller and the cost of the switching power supply device 1 becomes more remarkable.

As shown in the figure, a diode 27 may be arranged between the intermediate tap 31d of the primary winding of the transformer 31 and the positive side of the capacitor 30. In this case, the voltage charged in the capacitor 30 is, as shown in FIG. 5, the primary coil 31a with respect to the maximum value Vp of the pulsating current.
The voltage value ΔV boosted by is increased. Therefore, the capacitor 30 can store a larger amount of energy, and can be further downsized. In this case, energy circulation occurs in which energy is accumulated in the capacitor 30 from the capacitor 30 via the primary coil 31a of the transformer 31, but even in such a case, the conventional switching power supply device 101 is used.
It is possible to reduce the size of the capacitor 30 as compared with.

Further, in this embodiment, since the pulsating current is resistance-divided by the resistors 14 and 15, a slight voltage is applied to the gate of the FET 16 even when the voltage value of the pulsating current is lower than the reference voltage Vr. To be done. For this reason, on / off of the FET 16 may not be reliably controlled. In such a case, by disposing a Zener diode between the connection point between the cathodes of the diodes 12 and 13 and the resistor 14, it is possible to reliably control the ON / OFF of the FET 16. Further, the FET 16 and the transistor 22 control the ON / OFF of the FET 21, but in this case, it is necessary to use a high breakdown voltage type FET 16. In order to improve this point, the FET 16
If a photodiode of a photocoupler is used instead of and a phototransistor is used to control the gate voltage of the FET 21, the high breakdown voltage element is not used and the FET2
ON / OFF of 1 can be controlled reliably.

(Embodiment 2) Next, referring to FIG.
An example will be described. This switching power supply device 61 is the switching power supply device 1 in the first embodiment.
Means that the power supply of the storage and supply control means 6 is obtained from the auxiliary winding of the transformer 52, and the voltage value obtained by reducing the instantaneous voltage value of the pulsating current by a predetermined voltage value is used as the reference voltage Vr, and the storage and supply control means 6 It is basically different in that it uses a triac and blocks an inrush current to the capacitor 30 when the power is turned on. The figure shows a configuration corresponding to the output terminal of the diode bridge 11 to the primary coil of the transformer 31 in FIG.

In this switching power supply device 61, the energy stored in the auxiliary coil 52b of the transformer 52 when the switching of the switching circuit 32 is on is
Emitted when switching off, diode 25
The capacitor 26 serves as a power source for controlling the triac 65 and the transistor 53 as the storage / supply control means 6. The auxiliary coil 52b is usually included in the switching transformer, and therefore the cost increase due to the adoption of the auxiliary coil 52b is not caused.

In the switching power supply device 61, when the capacitor 30 is initially charged, a pulsating current flows through the capacitor 30, the diode 62 and the resistor 63 to the 0V line, so that the resistor 63 prevents the initial inrush of current. At the same time, electric charges are accumulated to some extent in the capacitor 30. In this state, when the switching operation by the switching circuit 32 is started and a voltage is generated in the winding 52b of the transformer 52, the transistor 64 is operated by the voltage generated across the resistor 63, and the transistor 53 is also operated. . As a result, the transistor 53
And the voltage is applied to the gate of the triac 65. Then, the triac 65 becomes conductive,
The charging current flows through the capacitor 30, and the capacitor 30
It is charged and held to the maximum value Vp of the pulsating flow. On the other hand, when the capacitor 30 is charged to the maximum value Vp, current does not flow through the capacitor 30 to the triac 65, and as a result, the triac 65 is automatically brought into a non-conducting state.

Next, the instantaneous voltage value of the pulsating current is determined by the reference voltage Vr.
Lower than that, the base current of the transistor 53 becomes
Resistor 65, diode 66 and Zener diode 5
It flows into the capacitor 30 via 6. As a result, a gate voltage is applied to the gate of the triac 65 via the emitter of the transistor 53 and the resistor 57, and the triac 65 becomes conductive. As a result, capacitor 3
The electric charge accumulated in 0 flows as a current I ₁₃ shown in FIG.
It is supplied to the primary coil 52a of the transformer 52. Thereby, the same effect as the switching power supply device 1 in FIG. 6 is exhibited.

As described above, in this embodiment, by using the inexpensive triac 65, both charging and discharging of the capacitor 30 can be controlled at a low cost. Moreover, by selecting the resistance value of the resistor 63, the value of the inrush current can be freely set.

(Embodiment 3) Next, referring to FIG.
An example will be described. This switching power supply device 71 is the switching power supply device 61 in the second embodiment.
What is basically different from this is that the function of blocking the inrush current to the capacitor 30 when the power is turned on is deleted to simplify the configuration. The same components in FIG. 7 as those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this switching power supply device 71, when the power is turned on, the pulsating current is applied to the gate of the triac 65 via the capacitor 30, the diode 62 and the resistor 63, so that the triac 65 becomes conductive. Therefore, the triac 6 is connected via the capacitor 30.
It flows into 5 and charging is performed. At the time of discharging,
The current ₁₄ flows through the same path as the current _{13 in the above} , thereby supplying energy to the primary coil of the transformer 52.

As described above, in this embodiment, charging / discharging of the capacitor 30 can be controlled with a very simple structure. Further, since the control circuit for accumulating and discharging the charge to and from the capacitor 30 is simplified, the power used for control can be reduced, and as a result, the conversion efficiency of the device can be improved.

Although the FET or the triac is used to control the charging of the capacitor 30 in the first to third embodiments, the present invention is not limited to this, and the storage and supply control means in the present invention may be Switch elements such as transistors and thyristors can be used. Furthermore, although the configuration of the flyback type switching power supply device has been described in the above embodiment, the present invention is not limited to this, and the present invention can be applied to a forward type switching power supply device. Further, the power conversion means 3 can be configured as a constant voltage power supply, a constant current power supply, and a constant power power supply.

In the above embodiments, the example in which the charge / discharge of the capacitor 30 is controlled by comparing the voltage value of the pulsating current with the reference value has been described, but the present invention is not limited to this, and the voltage of the pulsating current is not limited to this. The charge / discharge can be controlled by comparing one or both of the reference voltage and the comparison voltage generated based on the value and the pulsating current. As the comparison voltage in this case, when the voltage value of the pulsating current is A, a voltage represented by (k · A ± l) can be used as a general formula (where k and l are proportional constants, respectively). And the superimposed voltage). Specifically, voltage value (k · A)
Means a voltage obtained by boosting the pulsating flow by k times, and the voltage (k · A +
1) means a voltage obtained by superposing the voltage 1 on the voltage obtained by boosting the pulsating flow by k times. The reference voltage includes, of course, a preset fixed reference voltage, and also includes a reference voltage that varies in proportion to the pulsating current voltage value. In particular,
The comparison voltage (k · A) is converted to the voltage (k ₁ · A) (where k ₁
Means a constant of proportionality).

[0046]

As described above, according to the switching power supply device of the first aspect, for example, when a capacitor is used as the energy supplying means, the stored energy amount is proportional to the square of the voltage between the terminals of the capacitor. As a result, a sufficiently large energy can be stored, and as a result, a small capacity capacitor can be used. Further, the energy supply means does not store extra energy and can use a capacitor having a smaller capacity. Furthermore, by storing the input alternating current directly in the energy supply means, energy circulation is prevented, so that a capacitor with a smaller capacity can be used.

Further, according to the switching power supply device of the second and third aspects, if the energy based on the voltage obtained by superposing the winding voltage on the input AC voltage is accumulated in the energy supply means, for example, the energy supply means. When a capacitor is used as the result, the value of the voltage between the terminals can be made larger, and as a result, it becomes possible to store a larger amount of energy and a small capacity capacitor can be used.

Further, according to the switching power supply device of the fourth aspect, it is possible to configure the control power supply of the storage and supply control means without increasing the cost.

According to the fifth aspect of the switching power supply device, it is possible to eliminate the need for the rush current blocking means normally provided in the main power supply line of the switching power supply device. Further, in this case, since the capacitance of the capacitor can be reduced, it is possible to prevent the inrush current with a simple configuration.

Further, according to the sixth aspect of the switching power supply device, the storage and supply of energy can be controlled together by the inexpensive triac, so that the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a switching power supply device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of a pulsating current generated in the switching power supply device according to the embodiment of the present invention.

FIG. 3A is a pulsating flow signal waveform diagram for explaining storage and supply of energy to an energy supply unit in the present embodiment, and FIG. 3B is a signal waveform diagram of a voltage drop signal.

FIG. 4A is a signal waveform diagram for explaining a period for charging a capacitor as an energy supply unit in the present embodiment, and FIG. 4B is a signal waveform diagram of a voltage between terminals of the capacitor, c) is a signal waveform diagram of the power supplied to the power conversion means.

FIG. 5 is a signal waveform diagram of electric power supplied to a transformer according to a modification of the first embodiment.

FIG. 6 is a circuit diagram of the switching power supply device according to the first embodiment.

FIG. 7 is a circuit diagram of a switching power supply device according to a second embodiment.

FIG. 8 is a circuit diagram of a switching power supply device according to a third embodiment.

FIG. 9 is a circuit diagram of a conventional switching power supply device.

FIG. 10 is a signal waveform diagram of a voltage between terminals of a capacitor in a conventional switching power supply device.

[Explanation of reference numerals] 1 switching power supply device 3 power conversion means 4 voltage value determination means 5 energy supply means 6 storage supply control means 16 FET 21 FET 22 transistor 30 capacitor 31 transformer 52b auxiliary coil 53 transistor 61 switching power supply device 63 resistance 65 triac

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Claims (6)

[Claims] 1. A power conversion means for converting an input alternating current into either alternating current or direct current by switching the input alternating current, and supplying energy to the power conversion means when the voltage of the input alternating current is lower than a predetermined voltage. In a switching power supply device having an energy supply means for performing a voltage value determination for determining whether at least one of a voltage value of the input AC and a comparison voltage generated based on the input AC exceeds or drops below a reference voltage. Means for storing energy by the input alternating current with respect to the energy supply means within a period determined by the voltage value determination means, and when the voltage value determination means determines that the energy has decreased. A storage supply for supplying the energy stored in the energy supply means to the power conversion means. Switching power supply unit, characterized in that a control means. 2. The power conversion means includes a switching transformer, and the storage and supply control means stores energy in the energy supply means via a winding of the switching transformer. 1. The switching power supply device according to 1. 3. The switching power supply device according to claim 2, wherein the energy is energy based on a voltage obtained by superposing a winding voltage of the switching transformer on the input AC voltage. 4. The switching power supply device according to claim 2, wherein the switching transformer includes an auxiliary winding for supplying control power to the storage and supply control means. 5. The storage and supply control means comprises an inrush current blocking means for blocking an inrush current to the energy supply means when the power is turned on. The switching power supply device according to. 6. The storage and supply control means includes a triac, and by operating the triac, energy is stored in the energy supply means and energy stored in the energy supply means is transferred to the power conversion means. The switching power supply device according to claim 1, wherein the switching power supply device is supplied.