JPH04347575A - Power source circuit - Google Patents

Abstract

PURPOSE:To reduce the number of components, the size, and the cost and to improve a transient response characteristic of a DC output voltage. CONSTITUTION:In a power source circuit in which two sets of switching power sources are coupled in a cascade connection by including active filters 64, 70, a power factor is improved by the first stage and a DC is maintained constant by the second stage, and insulating converter transformer 60 for obtaining insulation of primary and secondary windings is used as a converter transformer of the filter 64 of the first stage, and the filter 64 of the front stage is constituted so as to vary a DC output voltage in proportion to an AC input voltage. The filter 70 of the second stage is constituted so as to perform control of maintaiing at least the average value of the DC output voltage constant to variation in the AC input voltage and control of stabilizing the DC voltage due to a variation in load by controlling a DC control current of a control winding of an orthogonal type power regulation transformer.

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, and more particularly to a switching power supply circuit for generating a constant voltage.

0002

2. Description of the Related Art As a conventional switching power supply circuit intended for power factor improvement and voltage constantization, a power supply device as shown in FIG. 6, for example, is known. In the figure, 1 is a DC power supply, which supplies a voltage of VAC=80 to 144 VAC to the bridge circuit. IAC indicates the current flowing through the bridge circuit. The bridge circuit is constructed by connecting four diodes 2 to 5 in a bridge manner. A capacitor 6 is connected to the output side of the bridge circuit, as well as a half-bridge resonant converter including switching transistors 7 and 8. Let the voltage across capacitor 6 be Ei. The first half-bridge resonant converter includes a switching transistor 7, resistors 8, 9, a capacitor 10, a diode 11 and a converter drive transformer (CDT) 12.
The winding 12a is a part of the winding 12a. The second half-bridge resonant converter is a switching transistor 1
3, resistor 14, 15, capacitor 16, diode 17
and a part of the winding 12b of the converter drive transformer (CDT) 12.

The converter drive transformer 12 has a primary
Insulation is ensured for both secondary and split bobbins. The transistor 7 has a winding 12a, a resistor 9 and a capacitor 10.
It is driven by a series resonant circuit consisting of. Similarly, transistor 13 is driven by a series resonant circuit consisting of winding 12b, resistor 15 and capacitor 16. The secondary side of the converter drive transformer 12 also constitutes a half-bridge resonant converter including its winding. That is, the third half-bridge resonant converter includes a switching transistor 21, a resistor 22, and a capacitor 2.
3. It is composed of a diode 24 and a part of the winding 12c of the converter drive transformer 12. The fourth half-bridge resonant converter includes a switching transistor 25, a resistor 26, a capacitor 27, a diode 28, and a part of the winding 12 of the converter drive transformer 12.
d. The transistor 21 has a winding 12c
, the transistor 25 is driven by a series resonant circuit consisting of a resistor 22 and a capacitor 23;
d, is driven by a series resonant circuit consisting of a resistor 26 and a capacitor 27. Note that each transistor 7, 13
, 21, 25 are respectively IQ1~
Let's assume IQ is 4.

A portion of the winding 12e of the converter drive transformer 12 is connected via a capacitor 29 to the primary winding of a quadrature power regulation transformer (PRT) 30. Let I1 be the current flowing through the winding 12e. The secondary winding of the power regulation transformer 30 is connected to a capacitor 32 via a diode 31, from which a 15V DC voltage is extracted. Further, the secondary winding of the power regulation transformer 30 is a diode 33.
, 34 to a capacitor 35 from which the DC output E0 is taken out, and further connected to a control circuit 36. The control circuit 36 is the transistor 4
1, 42, resistors 43 to 46, a capacitor 47, a Zener diode 48, and a control winding 30c of a power regulation transformer 30.
Control the control current flowing through c. In addition, the winding ratio of the power regulation transformer 30 is N1 /N2
/NC. Nc indicates the number of turns of the control winding 30c.

The collector of the switching transistor 21 in the third half-bridge resonant converter is connected to a capacitor 35. The collector of the switching transistor 25 in the fourth half-bridge resonant converter is connected to the primary winding of a second orthogonal power regulation transformer (PRT) 50 via a capacitor 49. The secondary winding of the power regulation transformer 50 is connected to the capacitor 5 via diodes 51 and 52.
3, from which a 15V/1A DC output is taken out. In addition, power regulation transformer 50
The secondary winding of is connected to a capacitor 56 via diodes 54 and 55, from which a 135V/1A DC output E
135 is taken out and is further connected to a similar control circuit 57. The control circuit 57 controls the control current flowing through the control winding 50c of the power regulation transformer 50. Note that the winding ratio of the power regulation transformer 50 is N1'/N21', N22
'/Nc'. Nc' indicates the number of turns of the control winding 50c.

[0006] In such a power supply circuit, two sets of switching power supplies (F-Z power supplies) using current resonant converter circuits using a fixed switching frequency series resonance frequency control system are connected in series, and the first stage performs power factor correction, and the second stage performs power factor correction. Works for voltage purposes. In addition, since the insulation between the primary and secondary of the power regulation transformer is ensured by the power regulation transformer 30 in the previous stage, the power regulation transformer 50 in the latter stage may be non-insulated, and the switching frequency is synchronized between the former stage and the latter stage. For this reason, the converter drive transformer 12 uses split bobbins for both the primary and secondary to ensure insulation.

FIG. 7 shows the operating signal waveform of the power factor correcting switching power supply, and in this active filter circuit, the voltage VAC of the input AC power supply 1 is 100 V, the current IAC flowing through the bridge circuit, and the output voltage E of the bridge circuit.
Orthogonal power regulation transformer 3 for i
The changes in the current I1 flowing through the secondary winding 30e and the DC output voltage E0 are shown. In this case, an AC ripple voltage twice the commercial frequency is superimposed on the DC output voltage E0, and the average value E0 = 180V is taken as a constant value.

FIG. 8 also shows a switching power supply (F
-Z power supply), and the AC ripple voltage is suppressed, resulting in a stabilized DC output voltage of E135 = 135V. In addition, power regulation transformer 5
Let the current flowing through the primary winding of 0 be I1'.

[0009]

[Problems to be Solved by the Invention] However, in such conventional power supply circuits, the power factor is improved to cosΦ=0.95 by using a switching power supply using a current resonant converter circuit with a fixed switching frequency and series frequency control method, and the resulting commercial The DC output voltage is superimposed with a ripple voltage twice the frequency, and a non-insulated switching power supply is used to suppress the ripple voltage and make the DC output voltage constant against fluctuations in load power. 20
When the power was 0W or more, the following problems occurred. (a) Since two sets of switching power supplies are connected vertically, two sets of orthogonal power regulation transformers are required, as well as two sets of control circuits that control the control current of the control winding, which requires many components and is expensive. It's cost. (b) Since the power factor correction active filter circuit is controlled so that the average value of the DC output voltage is constant, the high-speed transient response characteristic of the DC output voltage due to a sudden change in load power becomes slow, and the performance deteriorates. The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a power supply circuit that can reduce the number of component parts and reduce the size to reduce costs, and improve the high-speed transient response characteristics of the DC output voltage. There is.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, a power supply circuit according to the present invention includes a switching power supply using a current resonant converter circuit with a fixed switching frequency series resonant frequency control system and an active filter circuit. In a power supply circuit in which two sets are connected vertically, the switching power supply system converts an AC input voltage into a predetermined DC output voltage, and the power factor is improved in the front stage of the switching power supply, and the DC voltage is made constant in the latter stage. ,
The converter transformer of the active filter circuit in the front stage of the switching power supply that performs power factor correction is
An insulated converter transformer whose secondary winding is insulated is used, and at least an EE type or UU type ferrite core is used. Further, the active filter circuit at the front stage of the switching power supply is configured so that the DC output voltage changes in proportion to the AC input voltage. Furthermore, the active filter circuit in the latter stage of the switching power supply is directly controlled to maintain at least the average value of the DC output voltage constant against fluctuations in the AC input voltage, and to stabilize the DC output voltage due to load fluctuations. This is performed by controlling the DC control current of the control winding of the type power regulation transformer.

[0011]

[Operation] In the present invention, an insulated converter transformer in which insulation of the primary and secondary windings is ensured is used as the first orthogonal power regulation transformer in the conventional example, and
Since it is composed of an E-type or UU-type ferrite magnetic core, it is smaller and lighter, and at the same time, the control circuit and 15V rectifier circuit are removed from the active filter circuit in the previous stage related to the first orthogonal power regulation transformer. Therefore, the number of components is reduced and costs are reduced. Furthermore, since the active filter circuit simply functions to change the DC output voltage in proportion to the AC input voltage, the transient response characteristics of the DC output voltage to sudden changes in load power are improved.

0012

Embodiments Hereinafter, embodiments of the power supply circuit of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a power supply circuit according to a first embodiment of the present invention. In describing FIG. 1, the same components as those of the power supply circuit shown in FIG. 6 as a conventional example are given the same reference numerals, and redundant explanation will be omitted. The power supply circuit of this embodiment is different from the power supply circuit of FIG.
) 60, it becomes an EE coupling or UU coupling transformer, and is constituted by an EE type or UU type ferrite magnetic core. The secondary side of the isolated converter transformer 60 is connected to a capacitor 63 via diodes 61 and 62, from which a DC output Eo is taken out, and further connected to an active filter circuit 6.
It is connected to the collector of transistor 21, which is part of 4. The active filter circuit 64 is composed of an isolation converter transformer 60, diodes 61, 62, and a capacitor 65.

Second, the active filter circuit 64 in the previous stage
The control circuit and 15V rectifier circuit shown in FIG. 6 have been removed from , and the active filter circuit 64 simply operates to vary the DC output voltage in proportion to the AC input voltage. Therefore, when the AC input voltage changes from 80 to 120V, the DC output voltage changes from 160 to 200V.

On the other hand, the active filter circuit 70 in the subsequent stage
is a second orthogonal power regulation transformer 50,
It is composed of diodes 51, 52, 54, 55, a control circuit 57, and capacitors 53, 56. This active filter circuit 70 has a control function that keeps at least the average value of the DC output voltage constant against fluctuations in the AC input voltage, as in the conventional case, and a function that stabilizes the DC output voltage due to load fluctuations. These functions are achieved by controlling the DC control current Ic' of the control winding 50c of the orthogonal power regulation transformer 50.

In the above configuration, generally, a switching power supply (F-Z power supply) using a current resonant converter circuit with a fixed switching frequency series resonant frequency control method is isolated between the primary and secondary windings of the orthogonal power regulation transformer. It is possible to select any DC output voltage by selecting the turns ratio, and it is possible to design with high performance, low noise, and low cost. However, the drawback is that a ripple voltage twice the commercial frequency is superimposed on the DC output voltage, and the AC input voltage,
Due to the slow response of the DC output voltage to sudden changes in load, in order to suppress ripple voltage and improve high-speed transient response, two sets of switching power supplies are connected vertically.
The first stage has a power factor improvement function, and the second stage has a constant voltage function. However, in the conventional example, this power factor improvement and constant voltage power supply requires two sets of switching power supplies, and the power conversion efficiency is the product of the respective conversion efficiencies, resulting in a decrease in overall efficiency. Furthermore, the two sets of transformers, the orthogonal power regulation transformer and the converter drive transformer, are of an insulated type, and the circuit configuration is complicated, resulting in a large number of component parts, resulting in an increase in size and cost.

The operation of the power supply circuit of this embodiment is shown in the timing charts of FIGS. 2 and 3. FIG. 2 is a timing chart mainly from AC input to obtaining DC output voltage Eo through the active filter circuit 64 in the previous stage. When the voltage VAC of the input AC power supply 1 changes in the range of 80 to 120V, the isolated converter drive transformer (PIT
) 60, the changes in the current I1 flowing through the primary winding and the DC output voltage Eo are shown. Then, a DC input voltage is controlled by a switching power supply (F-Z power supply) using a current resonant converter circuit using a switching frequency fixed series resonant frequency control method using transistors 21 and 25 in the subsequent stage, a series resonant capacitor 49, and an orthogonal power regulation transformer 50. The DC output voltage is stabilized at E0 = 135V against changes in voltage, suppression of AC ripple voltage, and load fluctuations. Figure 3 shows the converter drive transformer (CDT)
) 12 secondary winding 12c and the control current Ic' of the direct power regulation transformer 50.
Each current change including .

In this case, the first orthogonal power regulation transformer is replaced with an isolated converter transformer (PIT) 60 that ensures insulation of the primary and secondary windings, and is constructed with an EE type or UU type ferrite core. Because of this, the transformer is smaller and lighter than before, and at the same time, unlike before, the control circuit and 15V rectifier circuit are removed from the active filter circuit 64 in the previous stage, so the number of components is reduced. It will be cheaper. Furthermore, since the control circuit and 15V rectifier circuit are eliminated, the high-speed transient response characteristics of the active filter circuit 64 are improved, resulting in improved performance. Note that, as in this embodiment, it is impossible to use the device for common use in Japan and North America in a range where the AC input voltage VAC varies from 80 to 144V. Therefore, in Japan, VAC = 80 to 120
In North America, VAC is guaranteed to be 108 to 144V.

Next, FIG. 4 is a diagram showing the configuration of a power supply circuit according to a second embodiment of the present invention. The difference between the embodiment shown in FIG. 4 and the first embodiment is that the converter drive transformer (CDT)
) 12 is non-insulated. Therefore, since both the converter drive transformer (CDT) 12 and the isolated converter transformer (PIT) 60 are non-insulated and the insulation is provided by the second orthogonal power regulation transformer 50, especially the converter drive transformer (C
DT) 12 and isolation converter transformer (PIT) 6
It becomes possible to reduce the size and weight of 0. In other words, there is no need for insulation in the active filter circuit at the previous stage, and the cost can be reduced, especially by downsizing the converter drive transformer (CDT) 12. In Figure 5, the capacitance of capacitor 65 is 4.
70μF, 13 when the capacitance of capacitor 56 is 100μF
135V with switching load condition on 5V line
5 is a timing chart showing high-speed transient response characteristics of the line. Compared to the conventional case in FIG. 1 where the capacitance of the capacitor 35=the capacitance of the capacitor 56=100 μF, this embodiment improves the ripple voltage and response time.

[0019]

As described above, according to the present invention, an insulated converter transformer in which insulation of the primary and secondary windings is ensured is used as the first orthogonal power regulation transformer, and an EE type or UU Since it is constructed using a shaped ferrite magnetic core, the power supply circuit can be made smaller and lighter, and at the same time, the control circuit and 15V rectifier circuit are removed from the active filter circuit in the previous stage related to the first orthogonal power regulation transformer. Therefore, the number of components of the power supply circuit can be reduced, and costs can be reduced. Furthermore, since the active filter circuit simply functions to change the DC output voltage in proportion to the AC input voltage, it is not possible to improve the high-speed transient response characteristics of the DC output voltage to sudden changes in load power. can.

[Brief explanation of drawings]

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

FIG. 2 is a timing chart of the operation on the front stage side of the embodiment shown in FIG. 1;

FIG. 3 is a timing chart of operations at a later stage of the embodiment shown in FIG. 1;

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

FIG. 5 is a timing chart of operations at a later stage of the embodiment shown in FIG. 4;

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

FIG. 7 is a timing chart of operations on the front stage side of a conventional power supply circuit.

FIG. 8 is a timing chart of the operation of the latter stage of the conventional power supply circuit.

[Explanation of symbols]

1: AC power supply 7, 13, 21, 25: switching transistor 12
:Converter drive tribe transformer (CDT) 57
: Control circuit 50: Second orthogonal power regulation transformer (
PRT) 60: Isolated converter transformer (PIT) 64, 70:
active filter circuit

Claims (1)

[Claims] [Claim 1] Two sets of switching power supplies using current resonant converter circuits with a fixed switching frequency and series resonance frequency control system are connected in series including an active filter circuit, and the switching power supplies convert an AC input voltage to a predetermined DC output voltage. In a power supply circuit that performs power factor improvement at the front stage of the switching power supply and makes the DC constant voltage at the rear stage, a converter transformer in the active filter circuit at the front stage of the switching power supply that performs the power factor improvement is used as a primary converter transformer. The insulation of the secondary winding is ensured, an insulated converter transformer is used, and it is configured with at least an EE type or UU type ferrite core, and the active filter circuit in the previous stage is configured so that the DC output voltage changes in proportion to the AC input voltage. The active filter circuit in the latter stage of the switching power supply is configured such that the control for keeping at least the average value of the DC output voltage constant against fluctuations in the AC input voltage and the control for stabilizing the DC output voltage due to load fluctuations are carried out orthogonally. A power supply circuit characterized in that the power supply circuit is configured to perform control by controlling a DC control current of a control winding of a type power regulation transformer.