JPH11341809A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a power source circuit and reduce the size of a current transforming means. SOLUTION: A power source circuit is provided with a rectifying means 2, a clipping means 3, a smoothing means 4, and a voltage stabilizing means 5, and is constituted by connecting the clip means 3 to the plus-side output terminal of the rectifying means 2, the anode terminal of a thyristor 3-1 to the anode terminal of a diode 3-2, the cathode terminal of the diode 302 to the cathode terminal of a Zener diode 3-3 and one terminal of the smoothing means, the node terminal of the Zener diode 3-3 to the gate terminal of the thyristor 3-1 and one terminal of a resistor 3-4, and the cathode terminal of the thyristor 3-1 and the other terminal of the resistor 3-4 to a reference potential, which is the negative/side output terminal of the rectifying means 2. When the voltage level prior to the power source circuit stabilization becomes equal to the Zener voltage of the Zener diode 3-3 or higher, the thyristor 3-1 is on- controlled.

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 receives an AC current and outputs a stabilized DC voltage, and more particularly to an improvement of a power supply circuit having a current transformer for insulation.

[0002]

2. Description of the Related Art Conventionally, a power supply circuit having a current transformer for insulation and outputting a stabilized DC voltage with an AC current as an input has been known because of an increase in an input current and a decrease in an output load. If the energy on the secondary side becomes excessive,
In order to prevent the secondary voltage of the current transformer from rising above the voltage level allowable by the smoothing circuit and the constant voltage circuit, the voltage is clipped at a predetermined voltage by a Zener diode.

FIG. 14 is a circuit diagram showing a configuration example of a conventional power supply circuit of this kind. As shown in FIG. 14, in the conventional power supply circuit, an input current is insulated by a current transformer 1 and a rectifier 2
Rectifies the current on the secondary side of the current transformer 1, connects the cathode terminal of the Zener diode 3-7 and one terminal of the smoothing capacitor 4 in the subsequent stage to the plus side output terminal of the rectifier 2, The anode terminal of the zener diode 3-7 and the other terminal of the smoothing capacitor 4 are connected to the output terminal so that the voltage at the previous stage of the constant voltage circuit 5 is clipped to the zener voltage of the zener diode 3-7 or less. I have to.

[0004]

However, in the conventional power supply circuit as described above, the voltage generated on the secondary side of the current transformer 1 is clipped by the zener diode 3-7 in order to suppress the voltage to a predetermined level. Therefore, the energy consumed by the Zener diode 3-7 is a wasteful loss, and lowers the efficiency of the power supply circuit.

Further, since the efficiency of the power supply circuit is low, it is necessary to use the current transformer 1 having a large burden, and there is a problem that the core size of the current transformer 1 cannot be reduced. An object of the present invention is to short-circuit the secondary side of a current transformer when the energy on the secondary side of the current transformer becomes excessive due to an increase in input current and a decrease in output load. It is an object of the present invention to provide a power supply circuit capable of improving power supply circuit efficiency by setting a mode and reducing the load on the current transformer by reducing the size of the current transformer.

[0006]

In order to achieve the above object, in a power supply circuit for inputting an alternating current and outputting a stabilized DC voltage, the invention according to the first aspect of the present invention provides a power supply circuit insulated from an input current. Rectifying means for rectifying the current on the secondary side of the means, clipping means for suppressing the voltage generated on the secondary side of the current transformer to a predetermined level, and smoothing means for smoothing the voltage output from the clipping means, Constant voltage stabilizing means for stabilizing the voltage after smoothing by the smoothing means to a voltage of a predetermined level, wherein the clip means is connected to the anode terminal of the thyristor and the anode terminal of the diode to the positive output terminal of the rectifying means. The cathode terminal of the diode is connected to the cathode terminal of the zener diode and one terminal of the smoothing means, and the anode terminal of the zener diode is connected to the gate terminal of the thyristor. The thyristor cathode terminal and the other terminal of the resistor are connected to the reference potential, which is the negative output terminal of the rectifier, so that the voltage level before stabilization is the Zener voltage of the Zener diode. When this is the case, the thyristor is controlled to be ON.

Therefore, in the power supply circuit according to the first aspect of the present invention, when the voltage level before the stabilization becomes equal to or higher than the Zener voltage of the Zener diode, the thyristor of the clipping means is controlled to be ON so that the current changing means is controlled. By suppressing the voltage generated on the secondary side to the ON voltage of the thyristor, the input load can be reduced, the power supply circuit efficiency can be improved, and the load on the current transformer can be reduced. Core size can be reduced.

[0008] According to the second aspect of the present invention, there is provided a rectifier for rectifying a current on a secondary side of the current transformer for insulating an input current.
Clipping means for suppressing the voltage generated on the secondary side of the current transformer to a predetermined level; smoothing means for smoothing the voltage output from the clipping means; and voltage smoothed by the smoothing means to a voltage of a predetermined level. A voltage stabilizing means for stabilizing, wherein the clip means is connected to the first and second terminals of the triac on the secondary side of the current transformer, and the cathode terminal of a zener diode is connected to the positive output terminal of the rectifier. And one terminal of the smoothing means are connected, the anode terminal of the zener diode is connected to the gate terminal of the triac and one terminal of the resistor, and the other terminal of the resistor is connected to the reference potential which is the negative output terminal of the rectifier. When the voltage level before the stabilization becomes equal to or higher than the Zener voltage of the Zener diode, the triac is turned on.

Therefore, in the power supply circuit according to the second aspect of the present invention, when the voltage level before the stabilization becomes equal to or higher than the Zener voltage of the Zener diode, the triac of the clipping means is controlled to be ON, so that the current changing means is controlled. By suppressing the voltage generated on the secondary side to the ON voltage of the triac, the input load can be reduced, the power supply circuit efficiency can be improved, and the load on the current transformer can be reduced, and the current transformer can be reduced. Core size can be reduced.

Further, according to the third aspect of the present invention, a rectifier for rectifying a current on a secondary side of a current transformer for insulating an input current;
Clipping means for suppressing the voltage generated on the secondary side of the current transformer to a predetermined level; smoothing means for smoothing the voltage output from the clipping means; and voltage smoothed by the smoothing means to a voltage of a predetermined level. A voltage stabilizing means for stabilizing, the clipping means being connected to a positive output terminal of the rectifying means, a drain terminal of a field effect transistor (FET) and an anode terminal of the diode, and a cathode terminal of the diode being connected to a Zener diode. The cathode terminal is connected to one terminal of the smoothing means, the anode terminal of the Zener diode is connected to the gate terminal of the field effect transistor and one terminal of the resistor, and the source terminal of the field effect transistor and the other terminal of the resistor are connected to the negative terminal of the rectifier. Connected to the reference potential, which is the output terminal of the And so as to ON control field effect transistor when a diode Zener voltage or more.

Therefore, in the power supply circuit according to the third aspect of the present invention, when the voltage level before stabilization becomes equal to or higher than the Zener voltage of the Zener diode, the current is controlled by turning on the field effect transistor of the clipping circuit. By suppressing the voltage generated on the secondary side of the transformer to the ON voltage of the field effect transistor, the input load can be reduced, the power supply circuit efficiency can be improved, and the load on the current transformer can be reduced. Accordingly, the core size of the current transformer can be reduced.

[0012] On the other hand, in the invention of claim 4, the above-mentioned claim 1 is provided.
In the power supply circuit according to any one of the third to third aspects, the constant voltage generating means is a series regulator circuit formed of a three-terminal regulator IC.

Therefore, in the power supply circuit according to the fourth aspect of the present invention, the voltage determined by the three-terminal regulator IC can be used as the output voltage by configuring the constant voltage generating means with the three-terminal regulator IC.

According to the fifth aspect of the present invention, the above first aspect is provided.
In the power supply circuit according to any one of the first to third aspects, the constant voltage generating means is a series regulator circuit including a transistor, a zener diode, and a resistor.

Therefore, in the power supply circuit according to the fifth aspect of the invention, the constant voltage means is a series regulator circuit composed of a transistor, a zener diode and a resistor. The voltage obtained by subtracting the intermediate voltage can be used as the output voltage.

According to a sixth aspect of the present invention, in the power supply circuit according to any one of the first to third aspects, the constant voltage means is constituted by a switching regulator circuit.

Accordingly, in the power supply circuit according to the sixth aspect of the present invention, the efficiency of the voltage regulating means can be further improved by forming the voltage regulating means from a switching regulator circuit.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment: Corresponding to Claim 1) FIG. 1 is a circuit diagram showing a configuration example of a power supply circuit according to the present embodiment.
The same elements as those in FIG. 14 are denoted by the same reference numerals.

That is, as shown in FIG. 1, the power supply circuit according to the present embodiment has a rectifier 2 which is a rectifier which rectifies a current on the secondary side of a current transformer 1 which is a current transformer which insulates an input current. A clipping circuit 3 as clipping means for suppressing a voltage generated on the secondary side of the current transformer 1 to a predetermined level, and a smoothing capacitor 4 as smoothing means for smoothing a voltage output from the clipping circuit 3. And a voltage stabilizing circuit 5 which is a voltage stabilizing means for stabilizing the voltage after smoothing by the smoothing capacitor 4 to a voltage of a predetermined level and outputting a DC voltage.

Here, the clip circuit 3 connects the anode terminal of the thyristor 3-1 and the anode terminal of the diode 3-2 to the positive output terminal of the rectifier 2, and connects the cathode terminal of the diode 3-2 to the Zener diode 3-2. 3, the anode terminal of the zener diode 3-3 is connected to the gate terminal of the thyristor 3-1 and the one terminal of the resistor 3-4, and the cathode terminal of the thyristor 3-1 is connected. And resistor 3-
4 is connected to a reference potential, which is a negative output terminal of the rectifier 2, and when the voltage level before stabilization becomes equal to or higher than the Zener voltage of the Zener diode 3-3,
The thyristor 3-1 is controlled to be ON.

Next, the operation of the power supply circuit of the present embodiment configured as described above will be described. In FIG. 1, the input current is insulated by a current transformer 1, and the current on the secondary side of the current transformer 1 is converted into a signal rectified by a rectifier 2.

The signal rectified by the rectifier 2 is input to a clipping circuit 3, the signal output from the clipping circuit 3 is smoothed by a smoothing capacitor 4, and the smoothed signal is stabilized by a constant voltage circuit 5. It is output as a converted DC voltage.

Here, when the voltage level across the smoothing capacitor 4 is equal to or lower than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, no current flows through the Zener diode 3-3 and the thyristor 3-1 does not flow. Since no voltage is applied to the gate terminal, the thyristor 3-1 is turned off.

On the other hand, when the voltage level across the smoothing capacitor 4 is equal to or higher than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, a current flows through the Zener diode 3-3 and the gate terminal of the thyristor 3-1. Is applied with a positive voltage, the thyristor 3-1 is turned on.

When the thyristor 3-1 is turned on, the output terminals of the rectifier 2 are short-circuited, and the voltage between the output terminals of the rectifier 2 becomes thyristor 3-1.
And the secondary voltage of the current transformer 1 is about 1.5 V obtained by adding the drop voltage of the rectifier 2 (for one diode) to the voltage between the output terminals of the rectifier 2.
Can be suppressed.

When the stabilized DC output voltage level output from the constant voltage circuit 5 is set to, for example, plus 5 V, and the minimum input voltage of the constant voltage circuit 5 that can be normally stabilized is set to plus 7 V, The Zener voltage level of the Zener diode 3-3 may be about (7V + α) of about 8 V. In this case, the input voltage level of the constant voltage circuit 5 is changed even when the output load condition and the input current condition change. And the Zener voltage of the Zener diode 3-3 does not exceed about 8V.

The voltage between the output terminals of the rectifier 2 on the anode terminal side of the diode 3-2 is not clipped when the voltage across the smoothing capacitor 4 is equal to or less than the zener voltage of the zener diode 3-3. Zener diode 3-3
When the voltage is higher than the Zener voltage, the voltage is intermittently clipped to about 1 V or less.

FIG. 2 is a diagram showing an example of the voltage waveform of each part by simulation in the present power supply circuit. FIG.
In A, A represents the output voltage waveform of the rectifier 2, B represents the input voltage waveform of the voltage regulating circuit 5, and C represents the output voltage waveform of the voltage regulating circuit 5.

The constant voltage circuit 5 increases the input voltage by 5 V
The voltage is stabilized, and the Zener voltage of the Zener diode 3-3 is set to 8V. As described above, in the power supply circuit of the present embodiment, the energy required for the constant voltage circuit 5 is ensured, and the excess energy on the secondary side of the current transformer 1 due to an increase in the input current and a decrease in the output load. Only in the state, the input load can be reduced by clipping the secondary side of the current transformer 1, the power supply circuit efficiency can be improved, and the load on the current transformer 1 can be reduced to reduce the load. The core size of the flower 1 can be reduced.

Further, by improving the efficiency of the power supply circuit, it is possible to obtain a power supply circuit in which heat generation is suppressed. (Modification 1: Corresponding to Claim 4) FIG. 3 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment. The description is omitted, and only different portions are described here.

That is, in the power supply circuit of the present embodiment, as shown in FIG. 3, the constant voltage circuit 5 in FIG. 1 is a series regulator circuit composed of a three-terminal regulator IC 5-1.

Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effect as described above, the constant voltage circuit 5 is constituted by the three-terminal regulator IC 5-1 so that the three-terminal regulator IC 5- The voltage determined by 1 can be used as the output voltage.

FIG. 4 is a circuit diagram showing another example of the configuration of the power supply circuit according to the present embodiment, in which the same parts as those in FIG. A description thereof is omitted, and only different portions will be described here.

That is, as shown in FIG. 4, the power supply circuit according to the present embodiment comprises a constant voltage conversion circuit 5 shown in FIG. 1 including a transistor 5-2, a Zener diode 5-4, and a resistor 5-3.
The positive terminal of the smoothing capacitor 4 is connected to the collector terminal of the transistor 5-2 and one terminal of the resistor 5-3, and the other terminal of the resistor 5-3 is connected to the transistor 5-2. And the cathode terminal of the Zener diode 5-4,
The anode terminal of the Zener diode 5-4 is connected to the negative terminal of the smoothing capacitor 4.

Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effects as described above, the constant voltage circuit 5 includes the transistor 5-2, the zener diode 5-4, and the resistor 5-3. With the series regulator circuit configured, a voltage obtained by subtracting the base-emitter voltage of the transistor 5-2 from the zener voltage of the zener diode 5-4 can be used as the output voltage.

(Modification 3 corresponds to claim 10) FIG.
FIG. 3 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment. The same portions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different portions will be described here.

That is, in the power supply circuit of the present embodiment, as shown in FIG. 5, the constant voltage circuit 5 in FIG. 1 is constituted by a switching regulator circuit 5-5. Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effects as described above, the efficiency of the voltage regulating circuit 5 is improved by forming the voltage regulating circuit 5 from the switching regulator circuit 5-5. Can be further improved.

(Second Embodiment: Corresponding to Claim 2) FIG. 6 is a circuit diagram showing a configuration example of a power supply circuit according to the present embodiment, and the same elements as those in FIG. Is shown.

That is, as shown in FIG. 6, the power supply circuit according to the present embodiment includes a rectifier 2 that is a rectifier that rectifies a current on the secondary side of a current transformer 1 that is a current transformer that insulates an input current. A clipping circuit 3 as clipping means for suppressing a voltage generated on the secondary side of the current transformer 1 to a predetermined level, and a smoothing capacitor 4 as smoothing means for smoothing a voltage output from the clipping circuit 3. And a voltage stabilizing circuit 5 which is a voltage stabilizing means for stabilizing the voltage after smoothing by the smoothing capacitor 4 to a voltage of a predetermined level and outputting a DC voltage.

Here, the clipping circuit 3 connects the first and second terminals (T
1 and T2 terminals), the cathode terminal of the zener diode 3-3 and one terminal of the smoothing capacitor 4 are connected to the positive output terminal of the rectifier 2, and the anode terminal of the zener diode 3-3 is connected to the triac 3-5. The gate terminal and one side terminal of the resistor 3-4 are connected, the other side terminal of the resistor 3-4 is connected to a reference potential which is a negative side output terminal of the rectifier 2, and the voltage level before stabilization is the Zener diode 3-3. When the Zener voltage is equal to or higher than the zener voltage, the triac 3-5 is ON-controlled.

Next, the operation of the power supply circuit of the present embodiment configured as described above will be described. In FIG. 6, the input current is insulated by the current transformer 1 and the current on the secondary side of the current transformer 1 is connected to the triac 3 connected between the secondary sides of the current transformer 1.
The signal is converted into a signal rectified by the rectifier 2 through -5.

The signal rectified by the rectifier 2 is smoothed by a smoothing capacitor 4 via a clip circuit 3, and the smoothed signal is output as a DC voltage stabilized by a constant voltage circuit 5. You.

Here, when the voltage level across the smoothing capacitor 4 is equal to or lower than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, no current flows through the Zener diode 3-3 and the triac 3-5 Since no voltage is applied to the gate terminal, the triac 3-5 is turned off.

On the other hand, when the voltage level across the smoothing capacitor 4 is equal to or higher than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, a current flows through the Zener diode 3-3 and the gate terminal of the triac 3-5. , The triac 3-5 is turned on.

When the triac 3-5 is turned on, the secondary terminals of the current transformer 1 are short-circuited, and the voltage between the secondary terminals of the current transformer 1 becomes triac 3-5. 5 is suppressed to about 1 V or less, which is the ON voltage.

When the stabilized DC output voltage level output from the constant voltage circuit 5 is set to, for example, plus 5 V and the minimum input voltage of the constant voltage circuit 5 that can be normally stabilized is set to plus 7 V, The Zener voltage level of the Zener diode 3-3 may be about (7V + α) of about 8 V. In this case, the input voltage level of the constant voltage circuit 5 is changed even when the output load condition and the input current condition change. And the Zener voltage of the Zener diode 3-3 does not exceed about 8V.

The secondary voltage of the current transformer 1 is not clipped when the voltage between both ends of the smoothing capacitor 4 is equal to or lower than the Zener voltage of the Zener diode 3-3. When the voltage is higher than the voltage, the clip is intermittently applied to about 1 V or less.

As described above, in the power supply circuit of the present embodiment, the energy required for the constant voltage circuit 5 is ensured, and the secondary side of the current transformer 1 is increased due to an increase in the input current and a decrease in the output load. Clipping the secondary side of the current transformer 1 only when the energy is excessive, the input load can be reduced, the power supply circuit efficiency can be improved, and the load on the current transformer 1 can be reduced. Thus, the core size of the current transformer 1 can be reduced.

Further, by improving the power supply circuit efficiency, it is possible to obtain a power supply circuit in which heat generation is suppressed. FIG. 7 is a circuit diagram showing another example of the configuration of the power supply circuit according to the present embodiment. The same parts as those in FIG. The description is omitted, and only different portions are described here.

That is, in the power supply circuit of the present embodiment, as shown in FIG. 7, the constant voltage circuit 5 in FIG. 6 is a series regulator circuit composed of a three-terminal regulator IC 5-1.

Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effects as described above, the constant voltage circuit 5 is constituted by the three-terminal regulator IC 5-1 so that the three-terminal regulator IC 5 The voltage determined by -1 can be used as the output voltage.

FIG. 8 is a circuit diagram showing another example of the configuration of the power supply circuit according to the present embodiment, in which the same parts as those in FIG. A description thereof is omitted, and only different portions will be described here.

That is, as shown in FIG. 8, the power supply circuit according to the present embodiment comprises a constant voltage circuit 5 shown in FIG. 6 including a transistor 5-2, a Zener diode 5-4, and a resistor 5-3.
The positive terminal of the smoothing capacitor 4 is connected to the collector terminal of the transistor 5-2 and one terminal of the resistor 5-3, and the other terminal of the resistor 5-3 is connected to the transistor 5-2. And the cathode terminal of the Zener diode 5-4,
The anode terminal of the Zener diode 5-4 is connected to the negative terminal of the smoothing capacitor 4.

Therefore, in the power supply circuit of the present embodiment, in addition to having the same effect as described above, the constant voltage circuit 5 is formed by the transistor 5-2, the Zener diode 5-4, and the resistor 5-3. With the series regulator circuit configured, a voltage obtained by subtracting the base-emitter voltage of the transistor 5-2 from the zener voltage of the zener diode 5-4 can be used as the output voltage.

(Variation 3: Corresponding to claim 11) FIG.
FIG. 9 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment. The same parts as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, in the power supply circuit of the present embodiment, as shown in FIG. 9, the constant voltage circuit 5 in FIG. 6 is constituted by a switching regulator circuit 5-5. Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effects as described above, the efficiency of the voltage regulating circuit 5 is improved by forming the voltage regulating circuit 5 from the switching regulator circuit 5-5. Can be further improved.

(Third Embodiment: Corresponding to Claim 3) FIG. 10 is a circuit diagram showing an example of the configuration of a power supply circuit according to the third embodiment. The same elements as those in FIG. Is shown.

That is, as shown in FIG. 10, the power supply circuit of the present embodiment has a rectifier 2 that is a rectifier that rectifies a current on the secondary side of a current transformer 1 that is a current transformer that insulates an input current. A clipping circuit 3 serving as clipping means for suppressing a voltage generated on the secondary side of the current transformer 1 to a predetermined level;
A smoothing capacitor 4 as a smoothing means for smoothing the voltage output from the clip circuit 3 and a constant voltage means for stabilizing the voltage after smoothing by the smoothing capacitor 4 to a voltage of a predetermined level and outputting a DC voltage. And a certain constant voltage conversion circuit 5.

Here, the clip circuit 3 is connected to a positive output terminal of the rectifier 2 by a field effect transistor (hereinafter referred to as an FET).
Drain terminal of 3-6 and diode 3-
2, the cathode terminal of the diode 3-2 is connected to the cathode terminal of the zener diode 3-3 and one terminal of the smoothing capacitor 4, and the anode terminal of the zener diode 3-3 is connected to the gate terminal of the FET 3-6. Connected to one terminal of the resistor 3-4, the source terminal of the FET 3-6 and the other terminal of the resistor 3-4 are connected to a reference potential which is a negative output terminal of the rectifier 2, and the voltage level before stabilization is reduced. When the voltage exceeds the Zener voltage of the Zener diode 3-3, the FET 3-6 is controlled to be ON.

Next, the operation of the power supply circuit of the present embodiment configured as described above will be described. In FIG.
The input current is insulated by the current transformer 1, and the current on the secondary side of the current transformer 1 is converted into a signal rectified by the rectifier 2.

The signal rectified by the rectifier 2 is input to the clipping circuit 3, the signal output from the clipping circuit 3 is smoothed by the smoothing capacitor 4, and the smoothed signal is stabilized by the constant voltage circuit 5. It is output as a converted DC voltage.

If the voltage level across the smoothing capacitor 4 is lower than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, no current flows through the Zener diode 3-3 and the gate of the FET 3-6 is turned off. Since no voltage is applied to the terminal, the FET 3-6 is turned off.

On the other hand, when the voltage level between both ends of the smoothing capacitor 4 is equal to or higher than the Zener voltage of the Zener diode 3-3 of the clipping circuit 3, a current flows through the Zener diode 3-3, and the current flows to the gate terminal of the FET 3-6. Since the plus voltage is applied, the FET 3-6 is turned on.

When the FET 3-6 is turned on, the output terminals of the rectifier 2 are short-circuited, and the voltage between the output terminals of the rectifier 2 becomes the O-state of the FET 3-6.
The voltage on the secondary side of the current transformer 1 is suppressed to about 1.5 V obtained by adding the drop voltage of the rectifier 2 (for one diode) to the voltage between the output terminals of the rectifier 2. Can be

The stabilized DC output voltage level output from the voltage stabilizing circuit 5 is set to, for example, +5 V, and the minimum input voltage of the voltage stabilizing circuit 5 that can be normally stabilized is +7 V.
In this case, the Zener voltage level of the Zener diode 3-3 may be set to (7 V + α) of about 8 V. In this case, the input voltage level of the constant voltage conversion circuit 5 depends on the output load condition and the input current condition. Even if there is a change, the Zener voltage of the Zener diode 3-3 does not exceed about 8V.

The voltage between the output terminals of the rectifier 2 on the anode terminal side of the diode 3-2 is clipped when the voltage across the smoothing capacitor 4 is less than or equal to the zener voltage of the zener diode 3-3. Zener diode 3-3
When the voltage is higher than the Zener voltage, the voltage is intermittently clipped to about 1 V or less.

As described above, in the power supply circuit of the present embodiment, the energy required for the constant voltage circuit 5 is ensured, and the secondary side of the current transformer 1 is increased due to an increase in input current and a decrease in output load. Clipping the secondary side of the current transformer 1 only when the energy is excessive, the input load can be reduced, the power supply circuit efficiency can be improved, and the load on the current transformer 1 can be reduced. Thus, the core size of the current transformer 1 can be reduced.

Further, by improving the power supply circuit efficiency, it is possible to obtain a power supply circuit with reduced heat generation. FIG. 11 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment.
The same reference numerals are given to the same portions as 0, and the description thereof will be omitted.
Here, only different parts will be described.

That is, as shown in FIG. 11, the power supply circuit of the present embodiment comprises
It is a series regulator circuit composed of a three-terminal regulator IC 5-1.

Therefore, in the power supply circuit according to the present embodiment, in addition to having the same effects as described above, the constant voltage circuit 5 is constituted by the three-terminal regulator IC 5-1 so that the three-terminal regulator IC 5 The voltage determined by -1 can be used as the output voltage.

(Modification 2: Corresponding to claim 9) FIG.
FIG. 11 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment. The same parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, the power supply circuit of the present embodiment, as shown in FIG.
Transistor 5-2, Zener diode 5-4, and resistor 5
-3, and the positive terminal of the smoothing capacitor 4 is a transistor 5-2.
And the collector terminal of the resistor 5-3 and one terminal of the resistor 5-3.
The other terminal of the resistor 5-3 is connected to the base terminal of the transistor 5-2 and the cathode terminal of the Zener diode 5-4, and the anode terminal of the Zener diode 5-4 is connected to the minus terminal of the smoothing capacitor 4. I have.

Therefore, in the power supply circuit of the present embodiment, in addition to having the same effects as described above, the constant voltage circuit 5 is formed by the transistor 5-2, the Zener diode 5-4, and the resistor 5-3. With the series regulator circuit configured, a voltage obtained by subtracting the base-emitter voltage of the transistor 5-2 from the zener voltage of the zener diode 5-4 can be used as the output voltage.

(Modification 3: Corresponding to Claim 12) FIG.
11 is a circuit diagram showing another configuration example of the power supply circuit according to the present embodiment. The same parts as those in FIG. 10 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.

That is, the power supply circuit of the present embodiment, as shown in FIG.
It comprises a switching regulator circuit 5-5. Accordingly, in the power supply circuit of the present embodiment, in addition to having the same effects as described above,
By using the switching regulator circuit 5-5, the efficiency of the constant voltage circuit 5 can be further improved.

[0076]

As described above, according to the power supply circuit of the present invention, when the energy on the secondary side of the current transformer becomes excessive due to an increase in the input current and a decrease in the output load, the energy is reduced. The power supply circuit efficiency is improved by setting the secondary side of the current transformer to the short-circuit mode only during the excessive time, and the current transformer can be downsized by reducing the load on the current transformer. Further, by improving the power supply circuit efficiency, it is possible to obtain a power supply circuit in which heat generation is suppressed.

[Brief description of the drawings]

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

FIG. 2 is an exemplary view showing an example of voltage waveforms of respective units by simulation in the power supply circuit according to the first embodiment.

FIG. 3 is a circuit diagram showing a first modification of the first embodiment of the power supply circuit according to the present invention;

FIG. 4 is a circuit diagram showing a second modification of the first embodiment of the power supply circuit according to the present invention.

FIG. 5 is a circuit diagram showing a third modification of the power supply circuit according to the first embodiment of the present invention;

FIG. 6 is a circuit diagram showing a configuration example of a power supply circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram showing a first modification of the power supply circuit according to the second embodiment of the present invention;

FIG. 8 is a circuit diagram showing a second modification of the power supply circuit according to the second embodiment of the present invention;

FIG. 9 is a circuit diagram showing a third modification of the power supply circuit according to the second embodiment of the present invention;

FIG. 10 is a circuit diagram showing a configuration example of a third embodiment of the power supply circuit according to the present invention.

FIG. 11 is a circuit diagram showing a first modification of the third embodiment of the power supply circuit according to the present invention.

FIG. 12 is a circuit diagram showing a second modified example of the third embodiment of the power supply circuit according to the present invention.

FIG. 13 is a circuit diagram showing a third modification of the power supply circuit according to the third embodiment of the present invention.

FIG. 14 is a circuit diagram illustrating a configuration example of a conventional power supply circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Current transformer, 2 ... Rectifier, 3 ... Clip circuit, 3-1 ... Thyristor, 3-2 ... Diode, 3-3 ... Zener diode, 3-4 ... Resistance, 3-5 ... Triac, 3-6 ... FET, 3-7 Zener diode, 4 Smoothing capacitor, 5 Constant voltage circuit, 5-1 3-terminal regulator, 5-2 Transistor, 5-3 Resistor, 5-4 Zener diode, 5 -5: Switching regulator circuit, A: Output voltage waveform of rectifier 2, B: Input voltage waveform of constant voltage circuit 5, C: Output voltage waveform of constant voltage circuit 5.

Claims (6)

[Claims] 1. A power supply circuit that receives an AC current and outputs a stabilized DC voltage, comprising: a rectifier that rectifies a current on a secondary side of a current transformer that insulates an input current; Clipping means for suppressing a voltage generated on the next side to a predetermined level; smoothing means for smoothing a voltage output from the clipping means; and stabilizing the voltage after smoothing by the smoothing means to a voltage of a predetermined level. A clipping means; a thyristor anode terminal and a diode anode terminal connected to a positive output terminal of the rectifying means; a cathode terminal of the diode being a cathode terminal of a Zener diode and the smoothing means. And the anode terminal of the Zener diode is connected to the gate terminal of the thyristor and one terminal of a resistor. When the cathode terminal of the thyristor and the other terminal of the resistor are connected to a reference potential which is a negative output terminal of the rectifier, and the voltage level before stabilization is equal to or higher than the Zener voltage of the Zener diode A power supply circuit, wherein the thyristor is controlled to be ON. 2. A power supply circuit which receives an AC current and outputs a stabilized DC voltage, comprising: a rectifier for rectifying a current on a secondary side of a current transformer for insulating an input current; Clipping means for suppressing a voltage generated on the next side to a predetermined level; smoothing means for smoothing a voltage output from the clipping means; and stabilizing the voltage after smoothing by the smoothing means to a voltage of a predetermined level. And a clipping means, and a first and a second triac on the secondary side of the current transformer.
, The cathode terminal of the Zener diode and one terminal of the smoothing means are connected to the positive output terminal of the rectifier, and the anode terminal of the Zener diode is connected to the gate terminal of the triac and one terminal of the resistor. The other side terminal of the resistor is connected to a reference potential which is a negative output terminal of the rectifier, and the triac is turned off when the voltage level before stabilization becomes equal to or higher than the Zener voltage of the Zener diode. A power supply circuit characterized in that ON control is performed. 3. A power supply circuit for inputting an alternating current and outputting a stabilized DC voltage, comprising: a rectifier for rectifying a current on a secondary side of a current transformer for insulating an input current; Clipping means for suppressing the voltage generated on the side to a predetermined level; smoothing means for smoothing the voltage output from the clipping means; and a constant for stabilizing the voltage after smoothing by the smoothing means to a voltage of a predetermined level. A voltage generating means, wherein the clipping means is connected to a drain terminal of a field effect transistor (FET) and an anode terminal of a diode to a positive output terminal of the rectifying means, and a cathode terminal of the diode is a cathode terminal of a Zener diode. And an anode terminal of the Zener diode connected to one terminal of the smoothing means, and a gate terminal of the field effect transistor. And a resistor connected to one terminal of the resistor, and a source terminal of the field-effect transistor and another terminal of the resistor connected to a reference potential which is a negative output terminal of the rectifier. When the voltage exceeds the Zener voltage of the Zener diode, the field-effect transistor is turned on.
A power supply circuit characterized in that N control is performed. 4. The method according to claim 1, wherein
3. The power supply circuit according to claim 1, wherein the constant voltage generating means is a series regulator circuit including a three-terminal regulator IC. 5. The method according to claim 1, wherein
3. The power supply circuit according to claim 1, wherein the constant voltage generating means is a series regulator circuit including a transistor, a zener diode, and a resistor. 6. The method according to claim 1, wherein
3. The power supply circuit according to claim 1, wherein the constant voltage generating means is constituted by a switching regulator circuit.