JPH04308469A - Power supply - Google Patents

Abstract

PURPOSE:To suppress fluctuation of output voltage without requiring a transformer by decreasing power supply to a capacitor and a load upon output voltage rise whereas increasing power supply upon output voltage drop. CONSTITUTION:When load current decreases and the output voltage across a capacitor 5 reaches the operating voltage of a constant voltage diode 8a, a transistor (Tr) 10b is turned ON and a voltage appears across a resistor 10a. When that voltage reaches the ON voltage of a Tr 11b, the Tr 11b is turned ON. At the same time, a Tr 10c is turned ON and the output voltage across the capacitor 5 drops. Consequently, the current flowing into a load 13 increases and when the output voltage drops to the operating voltage of a constant voltage diode 9a, a Tr 9b is turned OFF and a Tr 9e is turned ON. Collector-emitter voltage of the Tr 9e goes substantially to 0 and the Tr 10b is turned OFF. Consequently, a first switch circuit 4 is operated through a first voltage reference generating circuit 6.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to power supplies for equipment such as jar pots, rice cookers, irons, and vacuum cleaners, and power supplies in which electronic circuits used in the equipment are not isolated from commercial power sources. It is.

0002

2. Description of the Related Art In recent years, it has become common for electrical appliances used in homes to be equipped with electronic circuits including active elements. When an electronic circuit is installed in a device, the configuration generally consists of a power supply device and other electronic circuits. For convenience of explanation, the commercial power supply will be referred to as a primary circuit below. An example of the power supply for the conventional primary circuit described above will be described below with reference to FIG. 1 is a commercial AC power supply,
20 is an autotransformer for adjusting the voltage of the commercial AC power supply 1 to an appropriate level. 21 is a rectifier, 22 is a capacitor, and 10 is an electronic circuit serving as a load.

The operation of the power supply device configured as described above will be explained. The AC voltage of the commercial AC power supply 1 is voltage-dropped by an autotransformer 20 . The dropped AC voltage is rectified by a rectifier 21, and then smoothed by a capacitor 22 and converted into a DC voltage. The DC voltage obtained at the output at this time is determined by the terminal output voltage of the autotransformer 20.

0004

[Problems to be Solved by the Invention] The conventional power supply device described above uses a transformer, and has problems such as using a large amount of materials, being heavy, large, and inefficient. .

[0005] The present invention aims to solve the problems of the conventional methods and to realize a power supply device that is more convenient to use. The first objective is to realize a power supply device that can reduce fluctuations in output voltage with a configuration that does not use a transformer. A second object is to provide a second means for achieving the first object with a structure that similarly does not use a transformer.

[0006]

[Means for Solving the Problems] A first means of the present invention for achieving the first object includes a rectifier circuit connected to a commercial AC power supply, and a first reference voltage that is derived from the output of the rectifier circuit. a second reference voltage generation circuit that generates a second reference voltage lower than the first reference voltage; and a second reference voltage generation circuit that receives the output of the first reference voltage generation circuit. a first switch control circuit that controls on/off of the first switch circuit; a first current limiting circuit that limits the current flowing through the first switch circuit; a capacitor that is charged by the first switch circuit; a first output voltage detection circuit that detects an output voltage across both ends of the output voltage, a second output voltage detection circuit that detects a second output voltage that is lower than the first output voltage, and outputs of the two output voltage detection circuits. a second switch control circuit that receives the output and selects either the first reference voltage generation circuit or the second reference voltage generation circuit according to the output; and a second switch circuit that switches between the reference voltage generation circuit and the second reference voltage generation circuit, and when the output voltage increases, the power supply to the capacitor and the load is reduced, and when the output voltage decreases, the power supply is increased. It is intended as a power supply device.

A second means of the present invention for achieving the second object includes a rectifier circuit connected to a commercial AC power source;
a first reference voltage generation circuit that generates a first reference voltage from the output of the rectifier circuit; and a first switch control that controls on/off a first switch circuit in response to the output of the first reference voltage generation circuit. a first current limiting circuit that limits the current flowing through the first switch circuit; a second current limiting circuit that allows a current smaller than the first current limiting circuit to flow; and charging by the first switching circuit. a first output voltage detection circuit that detects an output voltage across the capacitor; and a second output voltage detection circuit that detects a second output voltage lower than the first output voltage; a third switch control circuit that receives outputs from two output voltage detection circuits and selects either the first current limiting circuit or the second current limiting circuit according to the output; and the third switch control circuit. and a third switch circuit that switches between the first current limiting circuit and the second current limiting circuit depending on the output of the circuit. It is intended to be a power supply device that increases the supply.

[0008]

[Operation] The first means of the present invention operates as follows. A first output voltage detection circuit and a second output voltage detection circuit monitor the output voltage across the capacitor, and when the output voltage reaches the first voltage, the output voltage is set to the second reference voltage. When a second voltage lower than the first voltage is reached, charging of the capacitor is controlled using the first reference voltage higher than the second reference voltage. In other words, when the output voltage fluctuates due to an increase or decrease in the current flowing through the load, the power supply device can reduce the range of this fluctuation.

The second means of the present invention is that when the output voltage increases or decreases due to an increase or decrease in the load current, the current value during energization is reduced when the output voltage increases by more than a certain value, and the output voltage is kept at a constant value. If the voltage decreases above this level, the current value during energization is increased to reduce the fluctuation width of the output voltage.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply circuit according to an embodiment of the first means of the present invention will be described below with reference to FIG. 1 is a commercial AC power source, and 2 is a rectifier circuit connected to the A side of the commercial AC power source 1, which is a positive half-wave rectifier circuit in this embodiment. A first current limiting circuit 3 limits the current value passing through this line to below a certain level, and is composed of a diode 3a and a resistor 3b. 4 is a first switch circuit that turns on and off the power supply to the capacitor 5 and the load 13; in this embodiment, P
It uses an NP transistor.

The first current limiting circuit 3 operates as follows. That is, when the base current of the transistor constituting the switch circuit 4 flows and the transistor becomes conductive, a voltage of approximately 0.6V is generated between the base and emitter, and a voltage of approximately 1.2V is generated in the diode 3a. Therefore, a voltage of 0.6V is applied to resistor 3b, and resistor 3b is applied with a voltage of 0.6V.
The flowing current is limited by the value of b.

Further, 6 is a first reference voltage generation circuit that generates a first reference voltage. The first reference voltage generation circuit 6 includes a constant voltage diode 6a and a resistor 6 connected in series from the output terminal C of the rectifier circuit to the terminal B of the other commercial power supply.
It consists of b. The voltage at the connection point D between the two is the output terminal of the first reference voltage generation circuit 1. A first switch control circuit 7 receives the output of the first reference voltage generation circuit 6 and controls the first switch circuit 4. The first switch control circuit 7 includes a resistor 7a and a transistor 7b.
It consists of 7c. The connection configuration is such that the collector of the transistor 7b and the base of the transistor 7c are connected, and the collector of the transistor 7b and the resistor 7a are connected, and the other end of the resistor 7a is connected to point C, which is the output terminal of the rectifier circuit 2. ing. Also, transistor 7b and transistor 7
The emitter of c is connected to the B side terminal of the commercial power supply. The base of the transistor 7b is connected to the output terminal D of the first reference voltage generation circuit 6, and the collector of the transistor 7c is connected to the base of the transistor 4 constituting the first switch circuit. In this embodiment, the transistors 7b and 7c are NPN transistors.

Reference numeral 8 denotes a first output voltage detection circuit for detecting the DC voltage across the capacitor 5. The first output voltage detection circuit 8 includes a constant voltage diode 8a and a resistor 8b.
It consists of The constant voltage diode 8a and the resistor 8b are connected in series, and the cathode, which is the other end of the constant voltage diode 8a, is connected to the positive terminal of the capacitor 5. The other end of the resistor 8b is connected to terminal B of the commercial power source. Terminal B of the commercial power supply and the negative terminal of the capacitor 5 are at the same point. Constant voltage diode 8a and resistor 8b
A connection point F is the output terminal of the first output voltage detection circuit 8 and is connected to the second switch control circuit 10. 9
is a second output voltage detection circuit that detects the output voltage across the capacitor 5. The second output voltage detection circuit 9 includes a series connection body of a constant voltage diode 9a and a resistor 9b connected to both ends of the capacitor 5, and a base connected to the resistor 9b.
Transistor 9c and transistor 9c connected to
A transistor 9e whose base is connected to the collector of
and a resistor 9d connected between the collector of the transistor 9c and the positive terminal of the capacitor 5. The cathode of the constant voltage diode is connected to the positive terminal of the capacitor 5, and the other end of the resistor 9b and the emitters of the transistors 9b and 9e are connected to the negative terminal of the capacitor 5. The collector of the transistor 9e is the output of the second output voltage detection circuit, and is connected to the output point F of the first output voltage detection circuit. In this embodiment, transistors 9b and 9e are NPN transistors.

Reference numeral 10 designates a second switch control circuit, which includes a resistor 1 whose one end is connected to the output terminal C of the rectifier circuit 2.
0a and 10d, a transistor 10b whose collector is connected to the other end of the resistor 10a, and a transistor 10c whose base is connected. The emitter of the transistor 10b is connected to the terminal B of the commercial power supply, the base of the transistor 10b is connected to the collector of the transistor 10c and the output terminal F of the first output voltage detection circuit 8, and the emitter of the transistor 10c is connected to one end of the resistor 10d. has been done. In this embodiment, the transistor 10b is an NPN transistor, and the transistor 10c is a PN transistor.
It is a P transistor. Second switch control circuit 1
The output of 0 is connected to the second switch circuit 11 from the collector of the transistor 10b.

The second switch circuit 11 consists of a resistor 11a and a PNP transistor 11b.
One end of a is connected to the output of the second switch control circuit 10. The other end of the resistor 11a is the transistor 11
The base of transistor 11b and the emitter of transistor 11b are connected to output terminal C of rectifier circuit 2. Further, the collector of the transistor 11b, which is the output point of the second switch circuit 11, is connected to the second reference voltage generation circuit 12. The second reference voltage generation circuit 12 includes a constant voltage diode 12
a and a resistor 6b forming the first reference voltage generating circuit. Constant voltage diode 12a
The collector of the transistor 11b is connected to the cathode of
Further, the anode is connected to the base of a transistor 7b constituting the first switch control circuit 7 and one end of a resistor 6b. The other end of the resistor 6b is connected to the B terminal side of the commercial AC power supply 1. Note that the load 13 is connected to both ends of the capacitor 5, and is often an electronic circuit or a constant voltage circuit.

The operation of this embodiment will be explained below. Suppose now that the load current has decreased and the output voltage has increased. The first output voltage detection circuit 8 monitors the output voltage across the capacitor 5, and the output voltage is detected by the voltage regulator diode 8.
When the operating voltage of a is reached or higher, the constant voltage diode 8a
operates, and a voltage is generated across the resistor 8b. This voltage is connected between the base and emitter of the transistor 10b constituting the second switch control circuit 10. Therefore, this voltage is the on-state voltage of transistor 10b of approximately 0.6
When the voltage reaches V, transistor 10b turns on.

Hereinafter, in order to simplify the explanation, it is assumed that the on-voltage of the transistor is completely ignored. That is, when the output voltage across the capacitor 5 reaches the operating voltage of the constant voltage diode 8a of the first output voltage detection circuit 8, the transistor 10b of the second switch control circuit 10 is turned on and voltage is applied across the resistor 10a. occurs. This voltage is
Transistor 11b forming second switch circuit 11
is supplied between the base and emitter of. Therefore, when this voltage reaches the on-voltage of transistor 11b, transistor 11b is turned on. At the same time, the transistor 10c constituting the second switch control circuit is turned on. In this case, that is, when transistor 10b and transistor 10c are both turned on, positive feedback is applied between these two transistors, and this state is maintained. In other words, even if the output voltage across the capacitor 5 drops and becomes below the operating voltage of the voltage regulator diode 8a that constitutes the first output voltage detection circuit 8, the second switch control circuit 10 maintains its previous state. ing. In this way, the second switch circuit 1
When transistor 11 is turned on, conduction occurs between the collector and emitter of transistor 11b, and this voltage becomes approximately 0V. Therefore,
Constant voltage diode 12a of second reference voltage generation circuit 12
and resistor 6b are equivalently connected in series between output terminal C of the rectifier circuit and terminal B of commercial power supply 1. In this way, the constant voltage diode 12a forming the second reference voltage generation circuit 12 generates the second reference voltage.

In this embodiment, the second reference voltage is set to be smaller than the first reference voltage. Therefore, the constant voltage diode 12a constituting the second reference voltage generation circuit 12 acts preferentially to the constant voltage diode 6b constituting the first reference voltage generation circuit 6. That is, the first switch control circuit 7 is operated by the second reference voltage generation circuit 12. That is, the first switch control circuit 7 is turned off when the voltage at the output terminal C of the rectifier circuit 2 is a second reference voltage lower than the voltage generated by the first reference voltage generation circuit 6. That is, capacitor 5 and load 1
The power supplied to 3 will be very small. At this time, a constant voltage diode 9 constituting the second output voltage detection circuit 9
a is turned on because its operating voltage is set lower than the operating voltage of the voltage regulator diode 8a. Therefore, transistor 9b is on and transistor 9e is off. Since transistor 9e is off,
The first output voltage detection circuit 8 is not affected by this second output voltage detection circuit 9.

Next, the operation of the present power supply circuit when the second reference voltage generation circuit is operating will be explained. Until the output voltage of the rectifier circuit 2 reaches the second reference voltage (hereinafter simply referred to as the second reference voltage) which is the operating voltage of the constant voltage diode 12a constituting the second reference voltage generation circuit 12 from 0. During this period, the second reference voltage generating circuit 6 does not generate the voltage. That is, no voltage is generated between both terminals of the resistor 6b. Therefore, the transistor 7b is in an off state, and the transistor 7c is turned on by supplying a bias current to its base by the resistor 7a. Therefore, current flows through the base of the transistor constituting the first switch circuit 4, which is connected to the collector of the transistor 7c. As a result, the first switch circuit 4 is turned on, current flows from the rectifier circuit 2 to the collector of the first switch circuit 4 via its emitter, and the capacitor 5 is charged. Load 13 at the same time
Power is also supplied to the resistor 8d via the resistor 8d. In this case, the charging current of the capacitor 5 and the current flowing to the load 13 are equal to or less than the value limited by the first current limiting circuit 3. That is, when the first switch circuit 4 is turned on, current also flows through the diode 3a connected in series, and a voltage of about 1.2V is generated during this time. On the other hand, a voltage of approximately 0.6V is generated between the base and emitter of transistor 4.
A voltage of about 0.6V, which is a difference from the voltage of the diode 3a of 1.2V, is applied to the resistor 3b. Therefore, by appropriately selecting the value of this resistor 3b, the current flowing through the resistor 3b, in other words, the current flowing through the transistor constituting the first switch circuit 4 is limited.

[0020] When the output voltage of the rectifier circuit 2 rises and exceeds the second reference voltage, and further exceeds the on-voltage between the base and emitter of the transistor 7b constituting the first switch control circuit 7, approximately 0.6V is exceeded. , transistor 7b is turned on,
Current flows into the collector through resistor 7a. As a result, a voltage is generated in the resistor 7a, the base-emitter voltage of the transistor 7c becomes approximately 0V, and the transistor 7c is turned off. When the transistor 7c is turned off, the transistors constituting the first switch circuit 4 are no longer supplied with base current and are turned off. Therefore, no power is supplied to the capacitor 5 and the load 13. When the output voltage of the rectifier circuit 2 again drops below the on-voltage of the transistor 7b constituting the first switch control circuit 7, the transistor 7b is turned off and the transistor 7c is turned on. Therefore, the first switch circuit 4 is turned on and commercial power is supplied to the capacitor 5 and the load 13 again.

Next, when the current flowing through the load 13 increases and the output voltage drops to the operating voltage of the constant voltage diode 9a constituting the second output voltage detection circuit 9, the transistor 9
b is turned off. When transistor 9b is turned off, resistor 9d becomes a bias resistor and transistor 9e is turned on. When the transistor 9e is turned on, a current flows from the resistor 10d of the second switch control circuit 10 and the transistor 10c to the collector-emitter path of the transistor 9e, and the voltage between the collector and emitter of the transistor 9e becomes almost 0, and the transistor 10b is turned off. be done. Therefore, the voltage generated across the resistor 10a becomes 0V. resistance 10
When the voltage across a becomes 0V, the second switch circuit 1
The transistor 11b constituting the transistor 1 is turned off. When the transistor 11b is turned off, the second reference voltage generation circuit stops operating, and the first reference voltage generation circuit 6 starts operating instead. At the same time, the transistor 10c is turned off, the positive feedback is also released, and this state is settled. Therefore, the first switch circuit 4 is operated by the first reference voltage generation circuit 6.

As described above, according to this embodiment, the output voltage across the capacitor 5 is monitored, and when detected by the first output voltage detection circuit 8, the reference voltage is set low and the second output voltage is When detected by the voltage detection means 9, the reference voltage is set to a higher value and a stable power supply device can be obtained.

Next, an embodiment of the second means of the present invention will be explained based on FIG. 14 is a third switch control circuit, which includes resistors 14a and 14d connected to the output terminal C of the rectifier circuit 2, a transistor 14b whose collector is connected to the resistor 14a, and a collector whose collector is connected to the resistor 14d. The transistor 14c is connected to the transistor 14c. The emitter of the transistor 14b is connected to terminal B of the commercial AC power supply, and the base is connected to the collector of the transistor 14c. Further, the base of the transistor 14c is connected to the collector of the transistor 14b. In other words, the transistor 14b and the transistor 14c constitute a positive feedback circuit. Reference numeral 15 denotes a third switch circuit, which is composed of a PNP transistor. The base of this transistor is connected to the resistor 14a, which is the output terminal of the third switch control circuit, and the transistor 14.
It is connected to connection point G of b. Further, the emitter is connected to the output terminal C of the rectifier circuit 2, and the collector is connected to the second current limiting circuit 16. 16 is a second current limiting circuit, which is composed of a diode 16a, a diode 3a forming a first current limiting circuit, and a resistor 3b. In other words, the second current limiting circuit connects the diode 16a and the diode 3 when the first switch circuit 4 is turned on.
The current value is determined from the relationship between the voltage generated by a, the base-emitter voltage of the transistor of the first switch circuit 4, and the resistor 3b.

The operation of this embodiment will be explained below. When the output voltage across the capacitor 5 increases and reaches the operating voltage of the constant voltage diode 8a forming the first output voltage detection circuit 8, the third switch control circuit 14
The transistor 14b constituting the resistor 14a turns on, and the resistor 14a
A voltage is generated across the . Then, the transistor of the third switch circuit 15 is turned on. At the same time, transistor 14c turns on, positive feedback occurs between transistor 14b, and this state is maintained. Therefore, even if the output voltage across the capacitor 5 falls below the voltage of the constant voltage diode 8a, this state is maintained. When the transistor 15 is on, the current flowing from the emitter through the collector flows to the base of the first switch circuit 4 and the transistor 7c via the diode 3a. As a result, the emitter-collector voltage of the transistor 15 is saturated to approximately 0V. This forms a first current limiting circuit. The voltage applied to the resistor 3b at this time is the voltage obtained by subtracting the base-emitter voltage of the transistor of the first switch circuit 4 from the operating voltage of the diode 3a, and is approximately 0.6V in this case. This voltage is applied to resistor 3b
is applied to Therefore, the flowing current is limited by the resistance value of this resistor 3b.

Next, when the output voltage across the capacitor 5 drops and reaches the operating voltage of the constant voltage diode 9a of the second output voltage detection circuit 9, the transistor 9b is turned off and the transistor 9e turns off the resistor 9d. Turn it on with a bias resistor. When the transistor 9e turns on, the transistor 9e passes through the resistor 14d and the transistor 14c.
A current flows through the collector and emitter of transistor 9e.
The collector-emitter voltage of is saturated to approximately 0V. Therefore, the transistor 14b constituting the third switch control circuit is turned off, and at the same time, the transistor 14c is also turned off, and the positive feedback formed by these two transistors is canceled. At this time, the voltage across the resistor 14a is 0V, and the third switch circuit 15 is turned off. Therefore, the current flowing through the first switch circuit 4 is limited from the first current limiting circuit 3 to the second current limiting circuit 16. The voltage applied to the resistor 3b at this time is the voltage obtained by subtracting the base-emitter voltage of the transistor of the first switch circuit 4 from the operating voltage of the sum of the diode 16a and the diode 3a. In other words, in the case of this example,
The voltage will be approximately 1.2V. In other words, the limited current increases compared to when the output voltage across the capacitor 5 increases, and the output current increases.

In this embodiment, since there are two diodes 3a, the current value can be switched at a ratio of 2:1 by switching the current limiting circuit, but the switching current value can be changed by adjusting the number of diodes used. It is easy to adjust.

As described above, according to this embodiment, when the load current decreases and the output voltage increases, the energizing current is decreased to reduce the power supplied to the output, and the load current increases and the output voltage decreases. Then, the power supplied to the output can be increased by increasing the energizing current.

[0028]

As described above, according to the first means of the present invention, when the output voltage fluctuates as the load current increases or decreases in a configuration that does not use a transformer, the switching reference voltage can be adjusted to reduce the output voltage. The purpose of this invention is to realize a power supply device in which the fluctuation range of the voltage is small. According to the second means of the present invention,
Similarly, when the output voltage fluctuates, a power supply device is realized that adjusts the current supplied to the output to reduce the fluctuation width of the output voltage. Therefore, when using the power supply device according to the first means of the present invention, the parts used are those with low withstand voltage ratings,
It can generate less heat. Similarly, the components used in the second means of the present invention can be those that generate little heat and have low component ratings.

[Brief explanation of drawings]

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

[Fig. 2] A block diagram showing an embodiment of the second means.

[Figure 3
] Block diagram showing a conventional power supply device

[Explanation of symbols]

1 Commercial AC power supply 2 Rectifier circuit 3 First current limiting circuit 4 First switch circuit 5 Capacitor 6 First reference voltage generation circuit 7 First switch control circuit 8 First output voltage detection circuit 9 Second output voltage detection circuit 10 Second switch control circuit 11 Second switch circuit 12 Second reference voltage generation circuit

Claims (2)

[Claims] 1. A rectifier circuit connected to a commercial AC power source, a first reference voltage generating circuit that generates a first reference voltage from the output of the rectifier circuit, and a second reference voltage lower than the first reference voltage. a second reference voltage generation circuit that generates a reference voltage; a first switch control circuit that receives the output of the first reference voltage generation circuit and controls on/off the first switch circuit; a first current limiting circuit that limits the flowing current; a capacitor that is charged by the first switch circuit; a first output voltage detection circuit that detects the output voltage across the capacitor; and the first output voltage. a second output voltage detection circuit that detects a lower second output voltage; and a second reference voltage generation circuit that receives outputs from the two output voltage detection circuits and, in response to the outputs, generates a second reference voltage. a second switch control circuit that selects one of the generation circuits; and a second switch circuit that switches between the first reference voltage generation circuit and the second reference voltage generation circuit based on the output of the second switch control circuit. A power supply device that reduces power supply to the capacitor and load when the output voltage increases, and increases power supply when the output voltage decreases. 2. A rectifier circuit connected to a commercial AC power supply, a first reference voltage generation circuit that generates a first reference voltage from the output of the rectification circuit, and an output of the first reference voltage generation circuit. a first switch control circuit that controls on/off the first switch circuit based on the received signal; a first current limit circuit that limits the current flowing through the first switch circuit; and a current that is smaller than the first current limit circuit. a second current limiting circuit, a capacitor charged by the first switch circuit, a first output voltage detection circuit for detecting an output voltage across the capacitor, and a second output voltage lower than the first output voltage; a second output voltage detection circuit that detects the output voltage; and a second output voltage detection circuit that receives outputs from the two output voltage detection circuits and selects either the first current limiting circuit or the second current limiting circuit according to this output. a third switch control circuit;
A third switch circuit is provided that switches between the first current limiting circuit and the second current limiting circuit based on the output of the third switch control circuit, and reduces the power supply to the capacitor and the load when the output voltage increases. , a power supply that increases power supply when the output voltage decreases.