JPH08154379A - Dc power supply device - Google Patents

Abstract

PURPOSE: To lower the breakdown voltage of an input smoothing capacitor for a switching power supply device whose power factor can be improved. CONSTITUTION: A smoothing capacitor 10 is connected to a rectifier and smoothing circuit 3 via a reactor 4 and via a primary winding 7 for a transformer 6. A series circuit composed of the primary winding 7 of the transformer 6 and of a switch 8 is connected in parallel with the capacitor 10. A secondary winding 11 of the transformer 6 is connected to an output smoothing capacitor 13 via a diode 12. During a period in which the switch 8 is turned off, the sum signal of the voltage of the rectifier circuit 3 and the voltage of the reactor 4 is applied to a series circuit composed of the primary winding 7 and of the capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device capable of improving power factor.

[0002]

2. Description of the Related Art When a DC power supply of a switching power supply is constructed by connecting a rectifying and smoothing circuit to a commercial AC power supply, a charging current flows through a smoothing capacitor only in the peak region of a sine wave AC voltage, and an input current waveform and force The rate gets worse. In order to solve this kind of problem, a power factor correction circuit may be provided in the preceding stage of the switching regulator circuit. However, if the power factor correction circuit and the switching regulator circuit are separately provided, the power supply device becomes large and costly.

In order to solve this kind of problem, it is conceivable to share the switch with the power factor correction and the switching regulator as shown in FIG. In the DC power supply device of FIG. 1, a bridge type rectifier circuit 3 including diodes D1, D2, D3 and D4 is connected to AC power supply terminals 1 and 2 to which a commercial AC power supply is connected via a high frequency filter (not shown). Is connected, and the reactor (inductance circuit element) 4, the diode 5, and the primary winding 7 of the output transformer 6 are connected between the one output terminal and the other output terminal (ground).
And a series circuit of a switch 8 composed of a field effect transistor are connected. A diode 9 is connected between the output end of the reactor 4 and the upper end of the switch 8, and a smoothing capacitor 10 is connected between the cathode of the diode 5 and the lower terminal of the rectifier circuit 3. Transformer 6 2
The secondary winding 11 is connected to an output rectifying / smoothing circuit including an output rectifying diode 12 and an output smoothing capacitor 13. The diode 12 has a directivity to be turned on when the switch 8 is off. A pair of DC output terminals 14
a and 14b are connected to both ends of the capacitor 13.

The switch 8 has a repetition frequency (for example, 20 kHz) higher than the frequency of the AC power supply terminals 1, 2 of, for example, 50 Hz.
The control circuit 15 for turning on / off at z) has resistors 16 and 17 as voltage detecting means connected between the output terminals 14a and 14b, and one input terminal of the resistors 16 and 17.
Of the reference voltage source 18 connected to the voltage dividing point of
An error amplifier 19 connected to the triangular wave generator 20, a triangular wave generator 20 that generates a triangular wave at a switching cycle, one input terminal connected to the output of the error amplifier 19, and the other input terminal connected to the triangular wave generator 20. A voltage comparator 21 whose output terminal is connected to the control terminal (gate) of the switch 8.
It consists of and. The error amplifier 19 outputs a voltage corresponding to the difference between the detected voltage and the reference voltage, and the comparator 21 compares the triangular wave with the error output to form a PWM pulse, which is sent to the switch 8.

While the switch 8 is on in the circuit of FIG. 1, a current flows through the circuit of the reactor 4, the diode 9 and the switch 8, and energy is stored in the reactor 4. During the off period of the switch 8, the diode 5 is turned on by the output voltage of the rectifier circuit 3 and the voltage (stored energy) of the reactor 4, and the capacitor 10 is charged.
When the switch 8 is turned on while the capacitor 10 is charged, a current flows through the reactor 4 by the circuit of the reactor 4, the diode 9 and the switch 8, and the capacitor 10, the primary winding 7 and the switch 8 are closed as a DC power source. Current also flows through the circuit. At this time, since a downward voltage is generated in the secondary winding 11, the output rectifying diode 12 is kept off and magnetic energy is stored in the transformer 6.
During the subsequent OFF period of the switch 8, the capacitor 10 is charged and the transformer 6 is charged as described above.
Is discharged, the output rectifying diode 12 is turned on, and a charging current flows through the capacitor 13. The capacitor 10 functioning as a DC power supply is charged to a voltage higher than the peak of the output voltage of the rectifier circuit 3 (about twice the power supply voltage) by the boosting action of the reactor 4.

When the output voltage of the circuit of FIG. 1 becomes lower than a desired value, the duty ratio of the PWM wave becomes large and the ON time width of the switch 8 becomes long. On the contrary, when the output voltage becomes higher than the desired value, the duty ratio of the PWM wave becomes small and the ON time width of the switch 8 becomes short.

[0007]

By the way, since the capacitor 10 is charged higher than the power supply voltage, an expensive and large-sized capacitor having a high breakdown voltage is required.

Therefore, an object of the present invention is to provide a DC power supply device which can be downsized, reduced in cost, and improved in power factor.

[0009]

The present invention for achieving the above object provides a rectifier circuit connected to an AC power supply terminal, a reactor whose one end is connected to one output terminal of the rectifier circuit, and One end of which is connected to the other end of the reactor and the other end of which is connected to the other output terminal of the rectifier circuit; an interrupting switch primary winding connected to one end of the switch; A power supply capacitor connected in parallel to the series circuit of the secondary winding and the switch, a secondary winding of the transformer, a rectifying / smoothing circuit connected to the secondary winding, and the AC power supply terminal. The present invention relates to a DC power supply device comprising: a control circuit that controls ON / OFF of the switch at a repetition frequency higher than the frequency of the applied AC voltage. As described in claim 2, it can be connected to the tap (intermediate terminal) of the primary winding of the reactor. Further, as described in claim 3, a DC bias power source can be connected in series with the reactor. Further, as described in claim 4, the DC bias power source can be composed of a capacitor and a diode which charges the DC bias power source using the voltage of the primary winding. Further, as described in claim 5, a diode for charging the bias power supply capacitor can be connected between the power supply side terminal or tap (intermediate terminal) of the reactor and one end or tap of the primary winding. Further, as described in claim 6, it is possible to provide a diode and a capacitor switch for performing a resonance operation.

[0010]

According to the inventions of the claims, the power supply capacitor is not directly connected to the output stage of the reactor but is connected through the primary winding of the transformer. Therefore, the sum of the output voltage of the rectifier circuit and the voltage of the reactor obtained during the off period of the switch is divided and applied to the primary winding and the capacitor. Therefore, the voltage of the power supply capacitor is lower than that of the conventional circuit of FIG. 1, and the power supply capacitor can be downsized and the cost can be reduced. Since the amplitude of the current flowing in the reactor changes in accordance with the amplitude of the AC power supply voltage, the waveform improving effect and the power factor improving effect can be obtained as in the conventional circuit. When the DC bias power supply is provided as described in claim 3, the charging voltage of the power supply capacitor can be increased, and the current can be passed through the reactor even in a period in which the amplitude of the AC power supply voltage is low. As described in claims 4 and 5, charging of the power supply capacitor is performed by 1
If the voltage of the secondary winding is used, the charging circuit can be simplified. According to the sixth aspect, it is possible to obtain the effect of reducing the switching loss due to resonance.

[0011]

[First Embodiment] Next, a DC power supply apparatus according to a first embodiment of the present invention will be described with reference to FIGS. However, FIG.
In FIG. 1, parts that are substantially the same as those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted. The DC power supply device of FIG. 2 omits the diodes 5 and 9 from the circuit of FIG. 1, except that the upper end of the capacitor 10 is not connected to the reactor (inductance) 4 via the diode 5 but only to the primary winding 7. , The same as that of FIG. Therefore, in the circuit of FIG. 2, the capacitor 10 is connected to the reactor 4 via the primary winding 7.
It is connected to the.

[0012]

[Operation] The comparator 21 outputs a comparison output pulse of the triangular wave V1 supplied from the triangular wave generation circuit 20 and the voltage V2 supplied from the error amplifier 19 as shown in FIG. appear. When this pulse is supplied to the gate of the switch 8, the switch 8 responds to this to perform on / off operation (intermittent operation), and the drain current Id flows during the on period as shown in FIG. 3 (C).

During the ON period of the switch 8, current flows through the rectifier circuit 3, the reactor 4 and the circuit of the switch 8. If the capacitor 10 has already been charged, then the capacitor 1
Current flows even in the closed circuit of 0, the primary winding 7, and the switch 8. When a current flows through the primary winding 7 from top to bottom, a downward voltage is generated in the secondary winding 11, so that the diode 12 is kept off and energy is stored in the transformer 6. The current I1 flowing through the reactor 4 is shown in FIG.
As shown in the enlarged view of (E), it has a slope and increases, and this peak value is the output voltage Vin of the rectifier circuit 3 shown in FIG.
Changes according to the amplitude of. During the off period of the switch 8, the rectifier circuit 3, the reactor 4, the primary winding 7, and the capacitor 10
Current flows through the circuit. While the charging voltage of the capacitor 10 is higher than the sum of the output voltage Vin of the rectifying circuit 3 and the voltage of the reactor 4, the charging current passing through the reactor 4 does not flow. Since the sum of the output voltage Vin of the rectifier circuit 3 and the voltage of the reactor 4 during the off period of the switch 8 is added to the series circuit of the primary winding 7 and the capacitor 10, a very high voltage is not applied to the capacitor 10. During the off period of the switch 8, the diode 12 is turned on, and the current based on the discharge of the stored energy of the transformer 6 and the charging current of the capacitor 10 flows through the diode 12 to the smoothing capacitor 13 and the load. The control for keeping the voltage between the output terminals 14a and 14b constant is the same as in the circuit of FIG.

As is apparent from the above, the capacitor 10 is not charged to a high value, so that the miniaturization, the low breakdown voltage, and the cost reduction can be achieved. Also, AC power supply terminals 1, 2
3E is smoothed by connecting a high-frequency filter (not shown) here, and the current flowing in the waveform becomes a waveform having a good approximation to a sine wave and the power factor is also improved.

[0015]

[Second Embodiment] Next, a DC power supply device according to a second embodiment of the present invention will be described with reference to FIG. However, in FIG. 4, parts that are substantially the same as those in FIGS. 1 and 2 are given the same reference numerals, and descriptions thereof will be omitted. In FIG. 4, the output terminal of the reactor 4 is connected to the center tap of the primary winding 7 of the transformer 6, and the configuration is the same as that of FIG.

When the connection point of the reactor 4 is moved to the tap of the primary winding 7 as shown in FIG. 4, a part of the primary winding 7 is connected between the reactor 4 and the switch 8, so that the switch 8 is connected. The current I1 flowing in the reactor 4 during the ON period of becomes small. On the other hand, the charging voltage of the capacitor 10 becomes high. Therefore, the voltage of the capacitor 10 can be adjusted. The circuit of FIG. 4 basically has the same configuration as the circuit of FIG. 2, and therefore has the same operation and effect.

[0017]

[Third Embodiment] Next, a DC power supply apparatus according to a third embodiment will be described with reference to FIG. However, in FIG. 5, parts that are substantially the same as those in FIGS. 1 and 2 are given the same reference numerals, and descriptions thereof will be omitted. The circuit of FIG. 5 is the same as that of FIG. 2 except that a bias power supply capacitor 22 and a diode 23 are added to the circuit of FIG. The bias power supply capacitor 22 is connected between the reactor 4 and one end of the primary winding 7, and the diode 23 is connected between one end of the capacitor 22 and the tap of the primary winding 7.
There is a directionality for charging so that the right end of 2 becomes a positive electrode.
Since the capacitor 22 is charged with the downward voltage of the primary winding 7 and the capacitor 22 is connected in series with the reactor 4, the voltage of the rectifier circuit 3, the voltage of the reactor 4, and the voltage of the bias power supply capacitor 22 are distributed. Sum is the primary winding 7
In addition to the series circuit of capacitor 10
Can be charged higher than in FIG. In addition, a period in which the above sum voltage is higher than the voltage of the capacitor 10 is shown in FIG.
2 is longer than that of the circuit of FIG. 2, so that the power factor improving effect is larger than that of the circuit of FIG. The basic circuit configuration of FIG. 5 is shown in FIG.
5 has the same effects as those of FIG.

[0018]

[Fourth Embodiment] The direct-current power supply device of the fourth embodiment shown in FIG. 6 is the one in which the positions of the capacitor 22 and the diode 23 of FIG. ing. That is, the capacitor 22 is connected to the reactors 4 and 1
It is connected between the tap of the next winding 7. Since the circuit configuration of FIG. 6 is obtained by adding the capacitor 22 to the circuit of FIG. 4 similarly to FIG. 5, it has both the effect of the circuit of FIG. 4 and the effect of the capacitor 22 of FIG. The diode 2
As shown by the dotted line, the connection position of the cathode of No. 3 is the primary winding 7
Can be transferred to the top of.

[0019]

[Fifth Embodiment] The DC power supply device of the fifth embodiment shown in FIG. 7 is the same as that of FIG. 5 except that the connecting position of the diode 23 of FIG. 5 is changed.
Is configured the same as. The diode 23 is connected between the center tap of the reactor 4 and the upper end of the primary winding 7. As a result, the bias capacitor 22 can be charged with the smoothing action of the reactor 4. In addition, the anode of the diode 23 is moved to the left end of the reactor 4 as shown by the dotted line, the cathode of the diode 23 is connected to the tap of the primary winding 7, and the capacitor 22
Can be connected to the tap of the primary winding 7 as shown by the dotted line. Since the circuit of FIG. 7 is basically the same as the circuit of FIG. 5, it has the same operation and effect.

[0020]

[Sixth Embodiment] Next, a DC power supply device according to a sixth embodiment will be described with reference to FIGS. However, in FIG. 8, the substantially same parts as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. The circuit of FIG. 8 is the same as that of FIG. 4 except that a resonance capacitor Cx and a resonance switch Qx composed of a field effect transistor are added to the circuit of FIG. A series circuit of the resonance capacitor Cx and the switch Qx is connected in parallel to the intermittent switch 8.
Since the two switches 8 and Qx are both insulated gate field effect transistors whose sources are connected to the substrate (bulk), as shown in FIG.
It has diodes D1 and D2 in antiparallel with S2, and has stray capacitances C1 and C2 in parallel with main switches S1 and S2. However, the diodes D1, D2 and the capacitor C1
, C2 can also be connected as separate components.

The control circuit 24 for controlling the resonance switch Qx is for turning on the switch Qx during the off period of the control signal Vg1 shown in FIG. 10B obtained from the control circuit 15 of the intermittent switch 8. The control signal Vg2 is shown in FIG.
It occurs as shown in (D). In addition, an idle period in which both are turned off is provided between the on periods of the first and second control signals Vg1 and Vg2.

FIG. 10 shows the state of each part of FIG. 8, and (A) and (C) show the voltages (drain-source voltage) V1 and Vq between the terminals of the switch 8 and Qx, respectively.
(B) and (D) show control signals Vg1 and Vg2 applied to the gates of the switches 8 and Qx, and (E) and (F) flow to the main switches S1 and S2 of the switch 8 and Qx shown in FIG. Currents IS1 and IS2 are shown, and (G) is a resonance capacitor Cx.
The voltage Vcx is shown.

The circuit of FIG. 8 has the same effect as that of FIG. 4, and also has the effect of reducing the switching loss due to the partial resonance operation.

In the circuit of FIG. 8, t1 to t2 of FIG.
During the ON period of the switch 8 shown in FIG.
While the current flows through the closed circuit of the secondary winding 7 and the switch 8,
Current flows through the closed circuit of the rectifier circuit 3, the reactor 4, and the switch 8. When the on / off switch 8 is controlled to be turned off at time t2, a current flows through the stray capacitance C1 of the switch 8 shown in FIG. 9 and is gradually charged. Therefore, the voltage V1 of the intermittent switch 8 is t2 as shown in FIG.
It gradually rises in the ~ t3 period. This achieves zero volt switching at turn-off and reduces switching loss. When the stray capacitance C1 is charged at time t3, the capacitor 10, the primary winding 7 and the capacitor C
current flows through a closed circuit composed of x and the main switch S2 of the resonance switch Qx or the diode D2, the rectifier circuit 3, the reactor 4, a part of the primary winding 7, and the capacitor C.
Current flows in a closed circuit consisting of x and the main switch S2 or diode D2. Next, the capacitor Cx enters the discharge mode, and the capacitor Cx, the primary winding 7 and the capacitor 10
In the closed circuit composed of the main switch S2 and the main switch S2, the current flows in the opposite direction (upward), and also in the closed circuit composed of the rectifier circuit 3, the reactor 4, the primary winding 7 and the capacitor 10. Since the capacitor Cx has a relatively large capacity, the voltage Vcx is maintained at a substantially constant DC voltage after being initially charged so that the right side becomes positive, as shown in FIG. Be drunk When the switch Qx is turned off at time t4, the stray capacitance C1 of the disconnecting switch 8 is reversely charged, and this voltage, that is, the voltage V1 of the disconnecting switch 8 decreases as shown in FIG. 10 (A). Capacity C1
The reverse charging current of 1 flows in the closed circuit of the capacitor 10, the capacitance C1 and the primary winding 7. As a result, the charge of the capacitance C1 is returned to the capacitor 10 or the secondary side capacitor 13. At time t5, the intermittent switch 8 is turned on, and when the current I1 flows through the switch 8, the voltage of the switch 8 is almost zero volt, and the switching loss becomes small.

The circuit of the capacitor Cx and the switch Qx can be added to the circuits of FIGS. 2, 5, 6, and 7. As a result, the same effect as that of FIG. 8 can be obtained.

[0026]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The switch 8 can be a semiconductor switch such as a bipolar transistor. (2) The polarities of the rectifier circuit 3 and the switch 8 can be reversed. (3) The bias capacitor 22 can be used as a battery power source. Further, a tertiary winding for charging the capacitor 22 can be provided in the transformer 6, and this voltage can be rectified by a diode and added to the capacitor 22. The voltage of the capacitor 22 can be variably controlled. (4) In each embodiment, as shown in FIG. 11, the polarities of the windings 7 and 11 of the transformer 6 may be set to the forward type, and the diode 12 may be turned on during the ON period of the switch 8. . In this case, a smoothing reactor L0 and a diode D0 are added. (5) In each embodiment, as shown in FIG. 12, the secondary winding 11 of the transformer 6 may be of a center tap type and rectified by the two diodes 12a and 12b. In this case, the diode 12a is turned on during the on period of the switch 8 and the diode 12b is turned on during the off period. (6) In each example, as shown in FIG.
It is possible to add a diode D0 and a reactor L0 to the circuit. This improves the smoothness when the switch 8 is on. (7) In each embodiment, as shown in FIG.
The smoothing reactor L0 can be added to the circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional DC power supply device.

FIG. 2 is a circuit diagram showing a DC power supply device according to a first embodiment.

FIG. 3 is a waveform diagram showing a state of each part of FIG.

FIG. 4 is a circuit diagram showing a DC power supply device of a second embodiment.

FIG. 5 is a circuit diagram showing a DC power supply device of a third embodiment.

FIG. 6 is a circuit diagram showing a DC power supply device of a fourth embodiment.

FIG. 7 is a circuit diagram showing a DC power supply device of a fifth embodiment.

FIG. 8 is a circuit diagram showing a DC power supply device of a sixth embodiment.

9 is an equivalent circuit diagram of part of FIG. 8. FIG.

10 is a waveform diagram of each part of FIG.

FIG. 11 is a diagram showing a transformer secondary side circuit of a modified example.

FIG. 12 is a diagram showing a transformer secondary side circuit of another modification.

FIG. 13 is a diagram showing a transformer secondary side circuit according to still another modification.

FIG. 14 is a diagram showing a transformer secondary side circuit of still another modification.

[Explanation of symbols]

 4 Reactor 6 Transformer 8 Switch 10 Capacitor

Claims (6)

[Claims] 1. A rectifier circuit connected to an AC power supply terminal, a reactor having one end connected to one output terminal of the rectifier circuit, one end connected to the other end of the reactor, and the other end connected to the other end. An intermittent switch connected to the other output terminal of the rectifier circuit, a primary winding of an output transformer connected to one end of the switch, and a parallel connection to a series circuit of the primary winding and the switch. A power supply capacitor, a secondary winding of the transformer, a rectifying / smoothing circuit connected to the secondary winding, and the switch at a repetition frequency higher than the frequency of the AC voltage applied to the AC power supply terminal. A DC power supply device having a control circuit for controlling ON / OFF of the power supply. 2. The DC power supply device according to claim 1, wherein the other end of the reactor is connected to a tap of the primary winding instead of being connected to one end of the switch. 3. The DC power supply device according to claim 1, further comprising a DC bias power supply connected in series to the reactor. 4. The DC power supply according to claim 3, wherein the DC bias power supply includes a bias capacitor that functions as a bias power supply and a diode that charges the bias capacitor by the voltage of the primary winding. apparatus. 5. The DC bias power supply includes a bias capacitor connected between the other end of the reactor and one end of the switch or a tap of the primary winding, one end or tap of the reactor and the one 4. The DC power supply device according to claim 3, comprising a diode connected between a terminal or a tap of the next winding on the power supply capacitor side. 6. A stray capacitance equivalently connected in parallel to the interrupting switch or an individual capacitor connected in parallel to the interrupting switch, and a built-in or separate capacitor connected in antiparallel to the interrupting switch. A first resonance diode; a resonance switch connected in parallel to the intermittent switch via a capacitor; and a resonance switch having a direction opposite to that of the first resonance diode. A built-in or individual second resonance diode connected in parallel with the first and the second resonance diodes, and from the time point slightly delayed from the start of the off period of the intermittent switch to the time point slightly before the end of the off period of the intermittent switch. A DC power supply device according to any one of claims 1 to 5, further comprising a control circuit for turning on the resonance switch.