JP2000299985A - Power supply circuit and power supply device using the same - Google Patents

Abstract

(57) [Problem] To provide a small-sized power supply circuit having a high efficiency with a simple configuration, which is suitable for a low power supply. SOLUTION: A rectifier circuit comprising rectifier diodes 5 and 6 for rectifying an input AC voltage from an AC power supply 1, and a capacitor 2 connected in series between the AC power supply 1 and the rectifier circuit. Power is supplied by the discharge current. Further, the resistor 3 and the coil 4 are connected in series to the capacitor 2 to prevent surge noise of the AC power supply 1.

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 having a small size and high efficiency, and more particularly to a power supply circuit suitable for a control circuit of a small control device and the like, and a main power supply circuit for supplying operating power and a control circuit. And a sub power supply circuit for supplying power to the power supply device.

[0002]

2. Description of the Related Art In recent years, with the spread of microcomputers, it has been widely practiced to mount microcomputers on various electric devices and control the operation thereof. Accordingly, electric appliances having a main power supply circuit for supplying operating power and a sub-power supply circuit for a low-voltage and low-power control circuit connected in parallel to the main power supply circuit are increasing.

A conventional power supply circuit used for a small control device, a sub power supply circuit and the like will be described with reference to a circuit diagram of FIG. In FIG. 8, the primary winding of the voltage conversion transformer 32 is connected to an AC power supply 31 of a commercial frequency.
The secondary winding of the voltage conversion transformer 32 is connected between both input terminals of the rectifier bridge circuit 33. A smoothing capacitor 34 is connected between both output terminals of the rectifying bridge circuit 33. An output voltage stabilizing capacitor 36 is connected in parallel to the smoothing capacitor 34 via a voltage stabilizing circuit 35. Capacitor 36 for stabilizing output voltage
The load 37 is connected in parallel. With this power supply circuit, the AC voltage of the AC power supply 1 is converted into a low-voltage AC voltage by the transformer 32, rectified by the rectifier circuit 33, smoothed by the smoothing capacitor 34, and supplied to the load 37 through the voltage stabilizing circuit.

[0004]

The frequency of the AC power supply 31 is 50 Hz or 60 Hz, and the voltage is 100 V or more. On the other hand, since the required voltage of the load, which is a small control device, is as low as several volts, it is necessary to increase the turns ratio between the primary winding and the secondary winding in the step-down transformer for obtaining the low voltage. . Therefore, it is necessary to increase the number of turns of the primary winding of the transformer. Further, it is necessary to ensure a safe distance of withstand voltage between the windings and between the input and output terminals according to the safety standard, which also has a problem that the transformer 32 becomes large. In addition, if the wire diameter of the winding is reduced in order to make the transformer as small as possible, the winding resistance increases and the stability decreases. When trying to stabilize the output voltage, the loss of the voltage stabilizing circuit 35 increases, and the heat generation increases. As a result, the conventional power supply circuit has a problem that a large amount of heat is generated in spite of a low power supply to a required load.

On the other hand, a small-sized switching power supply is sometimes used as this kind of power supply circuit. If the switching frequency is increased to reduce the size of the transformer, there is a problem that the switching loss increases and a power supply circuit with high efficiency cannot be realized. Further, when the above-described conventional power supply circuit is used as an electric device having a longer standby time than the operation time, for example, as a sub power supply circuit for a home air conditioner having a remote control circuit, the efficiency during the standby time is low due to poor efficiency. There is a problem that power cannot be saved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small and highly efficient power supply circuit suitable for a low output power supply. Another object of the present invention is to provide a main power supply circuit for supplying operating power,
It is an object of the present invention to provide a power supply device including a main power supply circuit and a small and highly efficient sub-power supply circuit for supplying a small power for a control circuit and a standby power supply connected in parallel.

[0007]

A power supply circuit according to the present invention comprises: a rectifier circuit for rectifying an input voltage from an AC power supply to convert the input voltage to a DC voltage;
It is characterized by having a capacitor connected in series.
According to this power supply circuit, since no transformer is used, no power is lost in the transformer coil or core. Further, power can be supplied by charging / discharging current of the capacitor. Therefore, a small power supply circuit that can supply small power with high efficiency can be realized.

In this power supply circuit, it is desirable to have voltage clamp means connected to the output circuit. A switch connected in parallel to at least one rectifying element constituting the rectifier circuit; and, when the output voltage rises above a predetermined value, the switch is turned on, and the output voltage falls below the value. Then, it is desirable to have switch control means for turning off the switch means. Further, it is desirable to have switch control means for turning on and off the switch means at a frequency equal to the frequency of the AC power supply and with a predetermined phase difference. Further, it is preferable to use a constant voltage diode as a rectifying element constituting the rectifying circuit. According to the power supply circuit having this configuration, a voltage stabilization circuit is not required, and a small-sized constant-voltage power supply circuit capable of supplying small electric power with high efficiency with greatly reduced heat generation due to loss of the voltage stabilization circuit can be realized.

Further, the switch control means includes an AD converter for converting an output voltage into digital data, and a comparator for comparing the digital data with a predetermined voltage and outputting a control signal for turning on and off the switch means. Is preferable. According to the power supply circuit having this configuration, analog control of output voltage control becomes unnecessary, and voltage control can be performed using a microcomputer used for the control circuit. As means for preventing surge noise of the AC power supply, it is desirable to connect a resistor or a coil or both in series to the capacitor. Further, it is desirable to have an overvoltage protection circuit for preventing an abnormal increase in the output voltage.

A power supply according to the present invention has a main power supply circuit for supplying operating power to electric equipment, and a sub-power supply circuit for a control circuit connected in parallel with the main power supply circuit or for backup or standby. Wherein the power supply circuit of the present invention is used as a sub power supply circuit.
In addition, it is preferable that the operation of the sub power supply circuit is stopped when the main power supply circuit operates. According to this power supply,
When the main power supply circuit operates, the operating power can be supplied from the main power supply circuit and the small power for the control circuit can be supplied from the sub power supply circuit with high efficiency. Further, power saving can be achieved during a standby time during which the main power supply circuit does not operate. Further, when the sub power supply circuit is used as a power supply circuit for supplying backup power, unnecessary power consumption can be prevented by stopping the operation of the sub power supply circuit which becomes unnecessary when the main power supply circuit operates.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a power supply circuit and a power supply device using the same according to the present invention will be described below with reference to FIGS.

Embodiment 1 A power supply circuit according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram of a power supply circuit according to Embodiment 1 of the present invention. In FIG. 1, both terminals of a commercial frequency AC power supply 1 include a resistor 3 for noise suppression, a coil 4, a capacitor 2, and a rectifier diode 5.
Connected in series. A series connection of a rectifier diode 6 and a smoothing capacitor 7 is connected in parallel with the rectifier diode 5. A load 17 is connected in parallel with the smoothing capacitor 7. The value of the resistor 3 and the value of the coil 4
Is set sufficiently lower than the impedance value of the capacitor 2 at the commercial frequency. Further, the capacitance of the smoothing capacitor 7 is set to a value such that the ripple voltage of the output voltage becomes sufficiently low.

In the power supply circuit of the first embodiment, when the output voltage is sufficiently lower than the input voltage, the value of the resistor 3 is sufficiently low. ). Here, C indicates the capacitance of the capacitor 2, V _{(pp )} indicates a voltage between the maximum value and the minimum value of the input voltage, and F indicates the frequency of the AC power supply.

I = C × V _(pp) × F (1)

As described above, the current I flowing through the capacitor 2
Is not affected by the resistance component. Therefore, no heat is generated for voltage conversion, and the resistor 3 and the coil 4 are used as a power supply circuit.
Has a sufficiently low impedance value, the loss due to heat generation is extremely small. Although the configuration of the rectifier circuit has been described as an example configured with the rectifier diodes 5 and 6, it goes without saying that a bridge circuit may be used. In the case of a bridge circuit,
The current can be doubled. Also, a rectifier circuit of a negative voltage in which the polarity of the rectifier diode is reversed operates in the same manner. Note that the resistor 3 and the coil 4 are for noise suppression and do not directly participate in the operation of the power supply circuit of the present invention.

Embodiment 2 A power supply circuit according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram of a power supply circuit according to Embodiment 2 of the present invention. As shown in FIG. 2, the power supply circuit of the second embodiment has a configuration in which a constant voltage diode 8 is added in parallel to a load 17 of the power supply circuit of the first embodiment as voltage clamping means. In the power supply circuit of the first embodiment, the output voltage changes according to the voltage, frequency, and load current value of the AC power supply 1. However, in the power supply circuit according to the second embodiment, since the above-described change can be absorbed by the constant voltage diode 8, a stable voltage can be supplied to the load 17. The power supply circuit according to the second embodiment includes a load 17 as a voltage clamping unit.
The example in which the constant voltage diode 8 is connected in parallel to the above has been described. However, the same effect can be obtained even if at least one of the rectifier diodes 5 and 6 constituting the rectifier circuit is a constant voltage diode as the voltage clamp means.

Embodiment 3 A power supply circuit according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 shows the third embodiment.
3 is a circuit diagram of a power supply circuit of FIG. The power supply circuit of the third embodiment is obtained by adding a circuit for controlling the output voltage to a predetermined output voltage to the power supply circuit of the second embodiment. Therefore, the same portions as those of the second embodiment are denoted by the same reference numerals, and the description is omitted. As shown in FIG. 3, a difference between a reference voltage source 11 that generates a preset voltage and an output voltage is amplified by an error amplifier 10 and a control signal for turning on and off a switching transistor 9 is output. If the output voltage is higher than the reference voltage,
The switching transistor 9 connected in parallel with the rectifier diode 5 is turned on to stop supplying power. When the output voltage is lower than the reference voltage, the switching transistor 9 is turned off to supply power. Heat value P at this time
Is represented by equation (2). Here, I indicates the current flowing through the capacitor 2, and R indicates the on-resistance of the switching transistor 9.

P = I × I × R (2)

The power supply circuit according to the third embodiment controls the on / off driving of the switching transistor 9 by the error amplifier 10.
The example in which the output is performed has been described. However, a preset voltage may be set by two comparators.
It can also be realized by a comparator having hysteresis. By using the error amplifier 10 as a comparator, the switching operation of the switching transistor 9 is not an analog operation but an on-off operation, so that the on-resistance R can be sufficiently reduced and heat generation can be extremely reduced.

In the power supply circuit according to the second embodiment, the heat generated by the constant voltage diode 8 causes a loss. However, according to the power supply circuit according to the third embodiment, since an excessive voltage is not applied to the constant voltage diode 15, 15 generates less heat. Therefore, a power supply circuit with less loss can be realized. With the power supply circuit of the third embodiment, the output voltage is 5 V and the output current is 5 m
As a result of trial production of the power supply circuit A, a power supply circuit having an efficiency of 90% or more was realized irrespective of the input voltage and frequency of the AC power supply.

Embodiment 4 A power supply circuit according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 4 shows the fourth embodiment.
3 is a circuit diagram of a power supply circuit of FIG. The power supply circuit of the fourth embodiment is different from the power supply circuit of the third embodiment in that the synchronization signal detector 12 and the synchronization circuit 1
3, and a switching transistor 14 is added in parallel with the rectifier diode 6. Therefore, the same portions as those of the third embodiment are denoted by the same reference numerals, and the description is omitted. In FIG. 4, the synchronization signal detection circuit 12
A synchronizing signal synchronized with the frequency of the AC power
Output to The synchronization circuit 13 outputs on / off drive signals for the switching transistors 9 and 14 output from the error amplifier 10 to the switching transistors 9 and 14 with a phase difference that minimizes heat generation with respect to the synchronization signal. According to the power supply circuit of the fourth embodiment, the switching transistors 9 and 14
, The heat generated by the on / off driving of the device can be minimized. Therefore, the loss can be further reduced.

A power supply circuit according to another embodiment of the fourth embodiment will be described with reference to FIG. FIG. 5 is a circuit diagram of a power supply circuit according to another embodiment of the fourth embodiment. As shown in FIG.
The power supply circuit according to another embodiment of the fourth embodiment does not use one of the switching transistors 14 and uses the synchronization signal detection circuit 1
2 is connected to a power supply capacitor 2 and a diode 5
Connected to the connection section. In this power supply circuit, similarly to the power supply circuit of the fourth embodiment, the on / off drive signal of the switching transistor 9 can be output with a phase difference that minimizes heat generation with respect to the synchronization signal.

Embodiment 5 A power supply circuit according to Embodiment 5 of the present invention will be described with reference to FIG. FIG. 6 shows a fifth embodiment.
3 is a circuit diagram of a power supply circuit of FIG. The power supply circuit according to the fifth embodiment uses the AD converter 16 and the comparator 10a as switch control means for controlling on / off of the switching transistor of the power supply circuit according to the fourth embodiment. Therefore,
The same parts as those in the fourth embodiment are denoted by the same reference numerals, and the description is omitted. In FIG. 6, a comparator 10a is used instead of the error amplifier 10 of the fourth embodiment, and the output of the AD converter 16 connected in parallel to the output circuit is input to the comparator 10a. The output voltage value converted into digital data by the AD converter 16 is compared with a predetermined reference voltage by a comparator 10a.
a, the switching transistors 9 and 14
On and off.

When used as a power supply for a control device using a microcomputer, the power supply circuit according to the fifth embodiment does not require analog control and can easily perform power supply voltage control as described above. For this reason, power supply voltage control does not burden the microprocessor. As a result, control of the entire apparatus including control of the power supply voltage can be performed by one microprocessor, and a high-performance power supply with low power consumption and high reliability can be realized with a small number of components.

Embodiment 6 A power supply according to Embodiment 6 of the present invention will be described with reference to FIG. FIG. 7 shows Embodiment 6.
FIG. 3 is a circuit diagram of the power supply device of FIG. Here, in the power supply device according to the sixth embodiment, the power supply circuit according to the second embodiment described above is used as the sub power supply circuit 22. Therefore, the same parts as those of the second embodiment are denoted by the same reference numerals, and the description is omitted. In FIG. 7, the power supply device according to the sixth embodiment includes a main power supply circuit 20 of a commercial AC power supply 19 that supplies operation power to a high-power main load 18.
And a sub power supply circuit 22 connected in parallel to the main power supply circuit 20 and supplying power to a control circuit 21 for controlling the operation of the main load 18. The control circuit 21 includes a microcomputer, a memory, or a remote control receiving circuit, a liquid crystal display device, and the like, and its power consumption is several watts. However, even when the main switch 23 is turned off and the operation of the main load 18 is stopped, the backup power is always supplied from the sub power supply circuit 22 to the control circuit 21 such as the memory, the remote control receiving circuit, and the display device.

For example, in the power supply device according to the sixth embodiment, the efficiency of the sub power supply circuit is 90%, and the operation time of the 500 W main load 18 is 2 hours a day, 24 hours a day. Consumes 0.09
W, this power supply in one day is 1002.4Wh
Of power. When a conventional power supply circuit is used as a sub-power supply circuit, if the power consumption of a power supply circuit using a conventional transformer is 0.9 W, the power consumption is 102 W
4 W, which means that power saving of 20 Wh can be achieved in almost one day.

As described above, according to the present invention, it is possible to provide a small, high-efficiency, low-power power supply. Therefore, a power supply device having a main power supply circuit for supplying operating power, and a low-power sub-power supply circuit for a control circuit and a backup,
Power consumption can be reduced by using the power supply circuit of the present invention as a sub power supply circuit. For example, when the power supply circuit of the present invention is used as a sub power supply circuit as a power supply device for a control circuit of an air conditioner or the like, the control circuit power is also supplied from the main power supply circuit during operation, and the power supply of the present invention is used as a sub power supply circuit during standby. Use a circuit. As a result, in an air conditioner in which the standby time is longer than in the operation, the power consumption can be significantly reduced. Further, when the power supply circuit of the present invention is used as a backup auxiliary power supply circuit, power consumption can be further reduced by stopping the operation of an unnecessary auxiliary power supply circuit when the main power supply circuit operates. .

[0028]

As is apparent from the detailed description of the embodiments, the present invention has the following effects.
That is, according to the power supply circuit of the present invention, by inserting a capacitor in series between the rectifier circuit and the AC power supply, a small and high-efficiency small power supply that can supply power with a charge / discharge current of the capacitor. Can provide power. To stabilize the output voltage, a constant voltage diode may be used.However, a power supply circuit that can supply a stable output voltage with higher efficiency by turning on and off the power supply to the rectifier circuit using a switching transistor Can be provided. According to the power supply device using this power supply circuit as a sub power supply circuit,
A great effect is obtained in that it can be used for a wide range of electrical equipment and can achieve energy saving in electrical equipment that has a long standby time during which the main power supply circuit stops.

[Brief description of the drawings]

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

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

FIG. 3 is a circuit diagram of a power supply circuit according to a third embodiment of the present invention.

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

FIG. 5 is a circuit diagram of a power supply circuit according to another embodiment of Example 4 of the present invention.

FIG. 6 is a circuit diagram of a power supply circuit according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of a power supply device according to Embodiment 6 of the present invention.

FIG. 8 is a circuit diagram of a conventional power supply circuit.

[Explanation of symbols]

 1, 19 AC power supply 2 Capacitor 3 Resistor 4 Coil 5, 6 Rectifier diode 7 Smoothing capacitor 8 Constant voltage diode 9, 14 Switching transistor 10 Error amplifier 10a Comparator 11 Reference voltage source 12 Synchronous signal detector 13 Synchronous circuit 15 Protection constant voltage Diode 16 AD converter 17 Load 18 Main load 20 Main power supply circuit 21 Control circuit 22 Sub power supply circuit 23 Main switch

Claims (10)

[Claims] 1. A power supply circuit comprising: a rectifier circuit for rectifying an input voltage from an AC power supply to convert the input voltage to a DC voltage; and a capacitor connected in series between the AC power supply and the rectifier circuit. 2. The power supply circuit according to claim 1, further comprising voltage clamp means connected to the output circuit. 3. A switch connected in parallel to at least one rectifier element constituting the rectifier circuit, and when the output voltage rises above a predetermined value, the switch is turned on, and the output voltage falls below the value. 2. The power supply circuit according to claim 1, further comprising switch control means for turning off said switch means when the power supply voltage drops to a value below. 4. The power supply circuit according to claim 3, further comprising switch drive means for turning on and off the switch means at a frequency equal to the frequency of the AC power supply and with a predetermined phase difference. 5. The apparatus according to claim 1, further comprising noise prevention means for preventing surge noise of the AC power supply connected in series between the AC power supply and the capacitor.
Power supply circuit as described. 6. The power supply circuit according to claim 1, wherein an overvoltage protection circuit for preventing an abnormal rise in the output voltage is connected to the output unit. 7. The power supply circuit according to claim 1, wherein the rectifier element forming the rectifier circuit is a constant voltage diode. 8. The switch control means includes an AD converter for converting an output voltage into digital data, and a comparator for comparing the digital data with a predetermined voltage value to turn on / off the switch means. Claim 3
Or the power supply circuit according to 4. 9. A power supply device comprising: a main power supply circuit for supplying electric power to an electric device; and a sub power supply circuit for supplying electric power to a control circuit of the electric device connected in parallel to the main power supply circuit. A power supply device using the power supply circuit according to any one of claims 1 to 8. 10. The power supply device according to claim 9, wherein the operation of the sub power supply circuit is stopped when the main power supply circuit operates.