JPH10117480A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the total power consumption and increase the efficiency of a power supply by lessening a voltage drop by load current and a resistor, when converting commercial AC power into DC. SOLUTION: This power supply device is provided with (n) loads 5, 6, 7 which are serially connected in the after stage of a rectifying circuit 2 and a resistor 1, a capacitor 11, and a controlling circuit 12 which serially connects the capacitor 11 to the load when power is supplied to the resistor 1 and parallelly connects the capacitor 11 to the load, when power is not supplied to the resistor 1. The controlling circuit 12 supplies the control current to the (m) loads out of the (n) loads, where (m) is less than (n).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit which is not insulated from a commercial AC power supply used in household electric appliances such as electric carpets.

[0002]

2. Description of the Related Art A conventional power supply of this type has a configuration as shown in FIG. 6 or FIG. The one in FIG.
A power supply unit composed of a resistor 1 for rectifying and smoothing a commercial AC power supply and converting it to DC, a rectifier diode 2, a capacitor 3, and a Zener diode 4 has three loads 5.
6, 7 are connected in parallel.

FIG. 7 shows three loads 5, 6, 7
Are used when operating at different voltages. That is, the voltage drop means 8 is provided between the load 5 and the load 6, and the voltage drop means 9 is provided between the load 6 and the load 7.
Are connected. This configuration also has three loads 5, 6, and 7 connected in parallel.
It is the same as FIG.

[0006] In FIGS. 6 and 7, a resistor 1 and a diode 2 connected in series are connected in reverse.

[0005] In this conventional example, a DC voltage is obtained by half-wave rectification of one diode, but there is also one in which the current utilization rate is doubled by full-wave rectification. There is also a power supply device configured with a negative power supply with the polarity of the diode 2 reversed.

Further, although the commercial voltage is reduced to an appropriate voltage by using the resistor 1, there is also a device using a transformer instead of the resistor 1.

[0007] The above power supply device needs to supply power to these three parallel loads, and a relatively large current capacity is required. As shown in FIG. 8, even when the power is not supplied from the commercial AC power supply 10 to the power supply device, the loads 5, 6, 7
The capacitor 3 is set to have a relatively large capacitance so that power can be supplied to the capacitor 3. Therefore, in order to charge the capacitor 3 with a sufficient charge, the current supply capacity also needs to be set large, and the resistance value of the resistor 1 is set small to realize.

The three loads 5, 6, 7 are actually electronic circuits, and the output voltage across the capacitor 3 is low for electronic circuits. Therefore, the voltage dropped by the resistor 1 is large. Further, by setting the value of the resistor 1 to a small value as described above, the current of the resistor 1 increases, and the voltage that drops further is large. Therefore, the power consumption of the resistor 1 is large, and the heat generation amount is also large. It has become something. This situation is also shown in FIG.

With such a setting, the current supply capacity of the power supply device is considerably larger than the load current when power is supplied from the commercial AC power supply 10. However, since a general load operates on DC, the current consumption is also a constant value of DC. Therefore, the current that does not flow to the load flows to the Zener diode 4 and is consumed there.

The conventional example shown in FIGS. 6 and 7 will be described with specific numbers. However, all of the following are provisional estimates,
It goes without saying that the present invention is not limited to this.

In FIG. 6, the load 5 is 24 V, 10 m
A, load 6 is 24V, 15mA, load 7 is 24V, 15
Assume that the rating is mA. It is assumed that a capacitor 3 of about 500 μF is required to stabilize the DC power supply.
In this case, the resistance 1 must be about 1 kΩ. At this time, power not consumed by the load is consumed only by the resistor 1. It consumes about 3.4W on average. Further, considering various conditions, the Zener diode 4 needs to have a rating of about 0.5 W or more.

Next, as shown in FIG.
When the load A is 5 V and 15 mA, the power loss of the voltage drop means 8 and 9 is further added. Voltage drop means 8
Is 0.36 W, and the power consumption of the voltage drop means 9 is 0.1 W.

[0013]

However, in the prior art, when converting a commercial voltage into a DC voltage of an appropriate magnitude, a large voltage load and a large current load are required for the resistor as the voltage drop means. Because of the large power consumption, it is necessary to use components with a large power rating, resulting in large heat generation and high temperature. As a result, there is a problem that the mounting becomes large.

In order to secure a necessary current supply capacity and a stable voltage, while power is supplied from a commercial AC power supply, the current that can be supplied is considerably larger than the operating current of the load. However, not all of the resulting power is used effectively, and merely increasing the power consumption of the resistor, which is the voltage dropping means, consumes completely useless power. In addition, there is a problem that a capacitor with a large capacitance is required to obtain a stable DC voltage, and a large power burden is required for the Zener diode, resulting in large heat generation, high temperature, and further increase in mounting size. Had.

[0015]

In order to solve the above-mentioned problems, the present invention provides a rectifier circuit connected to a resistor, a commercial AC power supply, and having at least one of an input and an output connected to the resistor. A circuit and n loads connected in series at the subsequent stage of the resistor, a capacitor, and when power is supplied to the resistor, the capacitor is connected in series to the load, and when power is not supplied to the resistor. Has a control circuit for connecting the capacitor in parallel with the load, and the control circuit supplies the control current to any m of the n loads, which are smaller than n.

According to the present invention, when power is supplied to the resistor, the capacitor acts as a voltage drop means, and the current flowing through the resistor and the capacitor is n.
Flows into the load. When power is not supplied to the resistor, the capacitor is connected in parallel with the n loads connected in series and serves as an auxiliary power supply for the entire load. Further, the control current of the control circuit acts as a supply current of a relatively large load m in addition to a current supplied from a commercial AC power supply through a resistor and a capacitor.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a rectifier circuit connected to a resistor, a commercial AC power supply, and having at least one of an input and an output connected to a resistor, and an n connected in series to a stage subsequent to the rectifier circuit and the resistor. A load, a capacitor, and a control circuit that connects the capacitor in series with the load when power is supplied to the resistor, and connects the capacitor in parallel with the load when power is not supplied to the resistor. , The control circuit supplies the control current to any m of the n loads less than n.

When power is supplied to the resistor,
The capacitor acts as a voltage drop means, and the current flowing through the resistor and the capacitor flows through n loads connected in series. When power is not supplied to the resistor, the capacitor is connected in parallel with the n loads connected in series and serves as an auxiliary power supply for the entire load. Further, the control current of the control circuit acts as a supply current of a relatively large load m in addition to a current supplied from a commercial AC power supply through a resistor and a capacitor.

Also, a resistor, a rectifier circuit connected to a commercial AC power supply and having a resistor connected to at least one of the input and output, a first load connected downstream of the rectifier circuit, and power supplied to the rectifier circuit. A load control circuit is provided that energizes the first load when supplied and shuts off the first load when power is not supplied to the rectifier circuit.

When power is supplied to the rectifier circuit, the first load is energized, and when power is not supplied to the rectifier circuit, the first load is cut off.

Further, the first load is connected in parallel with the first load.
The power supply device includes a capacitor and a second load that constantly consumes current.

When the power is supplied to the rectifier circuit, the capacitor is charged while the first load is supplied and the second load is supplied. When the power is not supplied to the rectifier circuit, the first load is supplied. The load is cut off, and the second load is energized by discharging the capacitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a circuit configuration diagram of a power supply device according to Embodiment 1 of the present invention. A resistor 1 and a rectifier circuit 2 are connected in series to one end 10a of the commercial AC power supply 10. Rectifier circuit 2
Is a half-wave rectifier circuit with one diode in this embodiment. Three loads 5 connected in series are connected between the other end of the rectifier circuit 2 and the other end 10b of the commercial AC power supply 10,
6 and 7 are connected. In this embodiment, the number n of loads is set to three. Reference numeral 11 denotes a first capacitor. Control circuit 1
2 is composed of diodes 12a, 12b and 12c, a transistor 12d and resistors 12e and 12f. Further, the resistor 12f has a common connection point with the load 5 and the load 6, and the current flowing through the resistor 12f is supplied to the load 6 and the load 7.

Here, three second to fourth capacitors 3, 15, 16 connected in parallel to the three loads 5, 6, 7 respectively suppress voltage fluctuations of the loads 5, 6, 7 respectively. I have. This is not always necessary when the voltage operation condition of the load does not require stabilization. However, since a load that operates under a stable voltage is generally used, it is described here that the load requires stabilization. In addition, three loads 5, 6, 7
Three Zener diodes 4 connected in parallel to
Reference numerals 13 and 14 limit the operating voltages of the loads 5, 6 and 7, and allow the current to pass to other loads when the load is stopped, that is, when no current flows through the load. Is not always necessary when the operating voltage condition is satisfied or when the load operates continuously. These capacitors 3, 15, 16 and Zener diode 4,
The versatility of this embodiment is expanded by connecting the loads 13 and 14 in parallel with the loads 5, 6 and 7, and the operation is completely the same even when they are not connected.

Next, the operation will be described. When the voltage on the terminal 10a side of the commercial AC power supply 10 is higher than a predetermined voltage in a positive cycle, the current flowing through the resistor 1 is the diode 2, the capacitor 11, the diode 12b, the first, second, and third loads 5,
Flow through 6,7. At this time, the diode 12a to the resistor 12
f, a forward voltage is generated between the diode 2 and the diode 12a, and the transistor 12
d becomes 0, the transistor 1
This is to cut off between the 2d collector and emitter. The current flowing through the resistor 1 and the capacitor 11 is supplied to first, second, and third loads 5, 6, and 7 connected in series.
At the same time, the first, second and third Zener diodes 4, 1
3, 14, and second, third, and fourth capacitors 3, 15, 1,
6 is also supplied with current. At the same time, the current flowing through the diode 12a and the resistor 12f is supplied to the load 6 and the load 7.

When the voltage of the commercial AC power supply 10 is smaller than a predetermined voltage or when the polarity is inverted and the terminal 10a side becomes a negative cycle, the power supply from the commercial AC power supply 10 is stopped, and the current is supplied to the diodes 2 and 12a. Stops flowing. At this time, the transistor 12d conducts from the diode 12c using the capacitor 11 as a power supply to the collector / emitter using the resistor 12f as a bias resistor.
When the transistor 12d conducts, the capacitor 11 is connected in parallel to the first to third loads 5, 6, and 7 equivalently connected in series via the diode 12c. That is, the capacitor 11 functions as an auxiliary power supply for supplying power to the first load 5, the second load 6, and the third load 7 at this time. Resistor 1 at the same time
The bias current of the transistor 12d flowing through 2f is supplied to the load 6 and the load 7.

The capacitor 3 and the Zener diode 4
Means that the first load 5 acts as first voltage stabilizing means, and the capacitor 15 and the Zener diode 13 act as second voltage stabilizing means for the second load 6. The capacitor 16 and the Zener diode 14
Means the third load 7 acting as third voltage stabilizing means. These are not necessarily required depending on the operation requirements of the loads 5 to 7. Further, the first load 5, the second load 6, and the third load 7 are constituted by electronic circuits.

In the present embodiment, the loads 5 to 7 are configured as three sets of loads, but any number of loads may be configured.

The loads 5, 6, and 7 each operating at the same voltage may be configured such that one or more loads are connected in parallel.

Although the rectifier circuit 2 is a half-wave rectifier circuit with one diode, the operation is the same even if the rectifier circuit 2 is constituted by a full-wave rectifier circuit.

As described above, each of the capacitors 1
Since the load 1 and the loads 5 to 7 are connected, the voltage borne by the resistor 1 becomes extremely small. That is, the magnitude of the voltage dropped from the commercial voltage can be made extremely small as compared with a conventional configuration in which loads are connected in parallel.

The current flowing through the resistor 1 is a current determined by the current used by the largest one of the three loads 5 to 7. When there is a surplus current other than the maximum load, the surplus current flows through the Zener diodes connected in parallel to each other. For example, when the load 7 is the maximum load, the current not consumed among the currents supplied to the loads 5 and 6 is consumed by the Zener diodes 4 and 13.

That is, by setting the current consumption of the three loads 5 to 7 as equal as possible, the resistance 1
Current flowing through the power supply can be reduced. At the same time, the current consumption of the Zener diode connected in parallel to the load can be reduced.

If the current consumption of the three loads 5 to 7 can be set to be completely equal, the Zener diodes connected in parallel can be eliminated.

However, even when the loads are actually combined so that the total value of the respective currents becomes equal, it is often difficult to make the loads of the completely equal currents. Zener diodes 4, 13, 14
Works as a means for absorbing the current difference between the loads 5 to 7, but the Zener diodes 4, 13,
The current flowing through 14 simply leads to wasteful power consumption, and merely increases the component ratings of the Zener diodes 4, 13, and 14 and increases heat generation.

In this embodiment, the resistor 12f is configured to have a common connection point with the load 5 and the load 6, so that the control current of the control circuit 12 can be supplied to the load 6 and the load 7. With this configuration, the currents of the load 6 and the load 7 can be set to a combination of currents larger than that of the load 5. That is, even the current necessary for operating the control circuit 12 can be supplied to the load 6 and the load 7 and used, so that it is possible to use the current for the operation of the load without waste. There can be no configuration at all.

In this embodiment, the connection point of the resistor 12f is common to the load 5 and the load 6, and the operating current of the load 6 and the load 7 is larger than that of the load 5. However, the resistor 12f is connected to the load 6 and the load 6. By making the connection point common to the load 7, it is needless to say that the operating current of the load 7 can be set larger than that of the loads 5 and 6.

Further, although the case where a positive power supply is constituted is described here, it goes without saying that the same applies to a case where a negative power supply is constituted.

Here, the description will be made using specific numbers. However, it is needless to say that all of the following are provisional approximate numerical values and are not limited to these.

It is assumed that a load similar to that of the conventional example shown in FIG. 7 is formed. That is, it is assumed that the load 5 is 24 V and 10 mA, the load 6 is 12 V and 15 mA, and the load 7 is 5 V and 15 mA. In order to stabilize the DC voltage as in FIG.
A μF capacitor 11 is required. In this case, the resistor 1 needs to have a resistance of 3 kΩ. The resistance 12f is 5 kΩ.
And The power consumption of the resistor 1 in this case is 0.3
W and the power consumption of the resistor 12f are 0.5W.

That is, the conventional capacitor 3 has a voltage of 24 V
In contrast to the necessity of 500 μF, in the first embodiment of the present invention, a voltage of 41 V and 100 μF is possible. In general, the size of a capacitor is often determined by (withstand voltage * capacitance), but the size of the capacitor can be realized with a volume of about 1/3.

The power not consumed by the load is about 4.4 W in the conventional example, but is 0.8 W in the first embodiment of the present invention.
And the power consumption is reduced to about 1/6.

As described above, according to the first embodiment of the present invention,
The current of the resistor 1 is reduced to one load, and at the same time, the voltage drop is reduced, the capacitor 11 can be used as an auxiliary power supply, and the control current of the control circuit 12 can be supplied to the load. This allows the power consumption of the resistor 1 to be smaller,
In addition, the overall power consumption is small, and the rating and heat generation of the constituent parts are suppressed to be small, and at the same time the temperature is lowered. Therefore, the power supply device of the present embodiment has high power supply efficiency, can be mounted in a small size, and can be configured at low cost.

(Embodiment 2) Next, a power supply unit according to Embodiment 2 will be described with reference to FIGS.

A resistor 1 and a rectifier circuit 2 are connected in series to one end 10a of the commercial AC power supply 10. Rectifier circuit 2
Is a half-wave rectifier circuit with one diode in this embodiment. A first load 18 is connected in series between the other end of the rectifier circuit 2 and the other end 10b of the commercial AC power supply 10.

The zener diode 4 connected in parallel to the first load 18 allows the current to pass when the load is stopped, that is, when no current flows through the load, and limits the operating voltage of the first load 18. Things. The Zener diode 4 is connected to the first load 18 in parallel so that the versatility of the present embodiment is expanded. Even when the Zener diode 4 is not connected, the operation is completely the same.

Here, a load control circuit 17 is further connected to one end 10 a of the commercial AC power supply 10 and the first load 18 to control conduction of the first load 18.

The operation will be described. When the terminal 10a side of the commercial AC power supply 10 rises in a positive cycle, the voltage value of the commercial AC power supply 10 becomes a predetermined voltage value, and the current capacity that can be supplied by the power supply device exceeds the operating current of the first load 18. In the phase, the load control circuit 17 performs control to make the first load 18 conductive.

Next, when the terminal 10a side of the commercial AC power supply 10 descends in a negative cycle, the voltage value of the commercial AC power supply 10 becomes a predetermined voltage value, and the current capacity that can be supplied by the power supply device becomes the first load 18 The load control circuit 17 performs control to cut off the first load 18 at a phase lower than the operating current of the first load.

A load driven by a DC voltage is generally operated by applying a stabilized voltage. However, there are many loads that can be sufficiently operated in practice even by pulse driving, such as a light emitting diode used for display and a solenoid coil such as a relay. As described above, when a load that is originally operated at a stabilized DC voltage is driven by a pulse,
In order to secure a sufficient load capability and perform stable operation, it is usually necessary to set the operating average current to be approximately equal to the rated current. That is, it is necessary to set the operating voltage of the first load 18 several times higher than the rated voltage in inverse proportion to the duty of the driving pulse.

When the load is operated with a stabilized DC power supply as shown in FIG. 8, the current supply capacity as a power supply device is as follows.
It is necessary to set the minimum capacity equal to or larger than the load current. That is, in order to secure the minimum current capacity even in the negative cycle of the commercial AC power supply 10, a sufficient charge must be stored in the capacitor-3, so that the current supply capacity in the positive cycle is several times larger than the load current. turn into. The large current of the resistor 1 also flows through the Zener diode 4,
The heat is also increased. Therefore, the value of the resistor 1 as the voltage drop means becomes small, and the power loss of the resistor 1 and the Zener diode 4 becomes extremely large due to the large voltage drop and the large passing current. The power rating and heat generation of the resistor 1 and the Zener diode 4 also increase, and the restrictions on temperature, mounting, and cost also increase.

However, in this embodiment, as shown in FIG. 3, the current capacity only needs to be ensured during the period when the voltage of the commercial AC power supply 10 is equal to or higher than the predetermined value, that is, during the load energizing period. Can operate with a magnitude substantially equal to the operating current of the first load 18.

Further, since the current of the Zener diode 4 becomes small, not only the power rating of the Zener diode 4 can be reduced, but also it can be deleted depending on the operation requirements of the load.

For this reason, the burden on the voltage drop means 1 is that although the passing current is several times larger, the current passing period is almost equal to the duty of the load driving time, and the passing charge per cycle of the commercial AC power supply 10 is the first. It is almost equal to the charge consumed by the load 18. Therefore, the current load can be reduced to a fraction of the conventional example in which a load is driven by a stabilized DC power supply.

The operation setting voltage of the first load 18 is
Since the voltage value is several times larger than that in the case of operating with the stabilized DC voltage, the voltage load on the voltage drop unit 1 can be set small.

As described above, since the current burden and the voltage burden on the resistor 1 are reduced, the power loss can be extremely small.

For this reason, the component rating and heat generation of the resistor 1 can be reduced, and the temperature, mounting and cost are less restricted.

Although the case where the first load 18 is one is described here, it goes without saying that the same operation is performed when a plurality of loads operating at the same voltage are connected.

In this case, the connection structure of the load may be connected in series like the loads 5, 6, and 7 shown in FIG. 1, or may be connected like the loads 5, 6, and 7 shown in FIGS. The same applies to the case of parallel connection.

Further, as in the first embodiment, the present embodiment describes a case where a positive power supply is configured. However, it is needless to say that the same applies when a negative power supply is configured.

Here, the description will be made using specific numbers. However, it is needless to say that all of the following are provisional approximate numerical values and are not limited to these.

That is, the first load 18 is rated at 24 V, 4
Assume 0 mA, ie 600Ω. In this case, resistance 1
Needs to be 200Ω. The power consumption of the resistor 1 is 0.02 W.

That is, the power not consumed by the load is about 3.9 W in the conventional example 1, but can be realized at 0.02 W in the second embodiment of the present invention, and the power consumption is reduced to about 1/200. Have been.

As described above, according to the second embodiment, the driving of the first load 18 is performed only during the time of power supply.
Since the current load and the voltage load of the resistor 1 can be reduced, the power loss can be reduced to a very small value.

Since the current of the Zener diode 4 is also reduced, not only can the power rating of the Zener diode 4 be reduced, but it can be eliminated depending on the operation requirements of the load.

For this reason, there are few restrictions on the component rating, the heat generation temperature, and the mounting surface, and the configuration can be made extremely cheap and compact.

Embodiment 3 Next, a power supply device according to Embodiment 3 will be described with reference to FIGS.

The following means are provided in addition to the second embodiment. A second load 19 that constantly consumes current is connected in parallel with the first load 18, and the capacitor 3 is further connected in parallel.

The operation of the third embodiment will be described below. As shown in FIG. 5, when the terminal 10a side of the commercial AC power supply 10 rises in a positive cycle, when the voltage value of the commercial AC power supply 10 reaches a predetermined voltage value, the load control circuit 17 turns on the first load 18. Perform control. At the same time, the current supplied from the commercial AC power supply 10 is the second load 19 that constantly consumes the current.
And the capacitor 3 is also charged.

Next, when the terminal 10a side of the commercial AC power supply 10 descends in a negative cycle, the voltage value of the commercial AC power supply 10 becomes a predetermined voltage value, and the current capacity that can be supplied by the power supply device becomes the first load 18 The load control circuit 17 performs control to cut off the first load 18 at a phase lower than the operating current of the first load. At the same time, when the current is no longer supplied from the commercial AC power supply 10, the capacitor 3 discharges, so that the current is continuously supplied to the second load 19 from the capacitor 3.

As described in the second embodiment, some loads may be driven in a pulsed manner and do not hinder practical operation. However, there is a load that does not operate unless current is constantly supplied. When these are connected to different DC power supplies, the number of peripheral components is merely increased unnecessarily. Therefore, when connected to the same DC power supply, the configuration can be made inexpensively.

In the third embodiment, the second load 19, which constantly consumes current, is set to a minimum, and a minimum capacitance is set in order to secure a current consumption in the negative cycle of the commercial AC power supply 10. This can be realized by the capacitor 3 provided.

When the supply current capacity is large in the positive cycle of the commercial AC power supply 10, another first load 1 that can be pulse-driven is used.
By supplying the current to the power supply 8, the power burden on the resistor 1 can be reduced similarly to the second embodiment, and the supply current can be used effectively.

Further, since the DC power supply voltage is stabilized by the capacitor 3, the loads 5 to 7 and the load control circuit 1 are controlled.
Also, the voltage of 7 does not become large, and it is not necessary to use a component having a large voltage rating.

As in the second embodiment, the first load 18
However, it is needless to say that the same operation is performed when a plurality of loads operating at the same voltage are connected.

The same applies to the second load 19. Also, as in the first embodiment, the present embodiment describes a case where a positive power supply is configured. However, it is needless to say that the same applies to a case where a negative power supply is configured.

As described above, according to the present embodiment, the second embodiment
In addition to the case, without increasing other peripheral parts,
Since the DC power supply voltage is stabilized by the capacitor 3, the voltages of the loads 5 to 7 and the load control circuit 17 do not become large, and components having a small voltage rating can be used.

[0078]

As is clear from the above description, the power supply device of the present invention has the following effects.

When power is supplied to the n loads, the capacitor, and the resistor connected in series at the subsequent stage of the rectifier circuit and the resistor, the capacitor is connected in series to the load, and when the power is not supplied to the resistor, And a control circuit in which a capacitor is connected in parallel to the load. The control circuit is configured to supply the control current to m loads smaller than n out of the n loads. It is possible to reduce the voltage drop, reduce the voltage drop, use the capacitor as an auxiliary power supply, and also supply the control current of the control circuit to the load, so that the power consumption of the resistor can be further reduced, and the rating and heat generation can be reduced. At the same time, the temperature is lowered. Therefore, it is possible to obtain an inexpensive power supply device with high power supply efficiency, small mounting, and low cost.

Further, a load control circuit for energizing the load when power is supplied to the rectifier circuit and shutting off the load when power is not supplied to the rectifier circuit is provided. By performing only at the time, the current load and the voltage load of the resistor can be suppressed small, so that the power loss can be suppressed extremely small.

Further, not only can the capacitance of the capacitor be kept small, but it can also be eliminated depending on the operation requirements of the load.

Further, since the current of the Zener diode 4 is also reduced, not only can the power rating of the Zener diode 4 be reduced, but also it can be eliminated depending on the operation requirements of the load.

Therefore, it is possible to obtain a small power supply unit which is advantageous in terms of component rating, heat generation, temperature and cost.

Further, since a configuration is provided that includes a capacitor connected in parallel with the first load and a second load connected in parallel with the first load and constantly consuming current, other peripheral components are provided. The DC power supply voltage is stabilized by the capacitor 3 without increasing the number of components, the voltages of the loads 5 to 7 and the load control circuit 17 do not increase, and components having a small voltage rating can be used.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a power supply device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing waveforms of a power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a power supply device according to a third embodiment of the present invention.

FIG. 5 is a diagram showing waveforms of a power supply device according to a third embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of a conventional power supply device.

FIG. 7 is a circuit configuration diagram of a conventional power supply device.

FIG. 8 is a diagram showing waveforms of a conventional power supply device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resistor 2 rectifier circuit 3 capacitor 5, 6, 7 load 10 commercial AC power supply (n loads) 11 capacitor 12 control circuit 17 load control circuit 18 first load 19 second load

Claims (3)

[Claims] A rectifier circuit connected to a commercial AC power supply and having at least one of an input and an output connected to the resistor; and n loads connected in series at a stage subsequent to the rectifier circuit and the resistor. A capacitor and a control circuit for connecting the capacitor in series to the load when power is supplied to the resistor, and connecting the capacitor in parallel to the load when power is not supplied to the resistor. And a power supply device, wherein the control circuit supplies the control current to an arbitrary m loads smaller than n out of the n loads. 2. A rectifier circuit connected to a commercial AC power supply and having at least one of an input and an output connected to the resistor, a first load connected to a stage subsequent to the rectifier circuit, and the rectifier circuit. And a load control circuit for energizing the first load when power is supplied to the rectifier circuit and shutting off the first load when power is not supplied to the rectifier circuit. 3. The power supply device according to claim 2, further comprising a capacitor connected in parallel with the first load, and a second load that constantly consumes current.