JPH11136942A - Switching power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery backed-up type switching power source which has a higher harmonic current suppressing function, does not use many number of part items, and can be reduced effectively in size and cost. SOLUTION: A PFC converter 12 charges a smoothing capacitor 13 by switching the rectified output of a rectifier circuit 11. A main converter 2 switches the DC voltage V1 which appears between the terminals of the capacitor 13 and supplies a DC output voltage Vo to a load L, by converting the switching output into a DC voltage. In a backup circuit 3, a secondary battery 31 is charged with energy supplied from an input circuit 1 and, when a switching element 35 is turned on, the charges stored in the battery 31 are discharged through the element 35. The output voltage V1 of the PFC converter 12 is substantially proportioned to the charging voltage V2 of the battery 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a switching power supply, and more particularly, to a switching power supply having a function of backing up by a storage element such as a battery.

[0002]

2. Description of the Related Art This type of switching power supply is used for applications that need to maintain its operation by a battery backup even when a commercial power supply fails, for example, a power supply for a PHS base station. Types have been proposed. For example, Japanese Patent Application Laid-Open No. 9-56085 discloses that a charge / discharge circuit having a backup element composed of a battery is connected to the secondary side of a conversion transformer provided in a power conversion circuit, and the charge / discharge circuit is generated in a secondary winding of the conversion transformer. When the backup element is charged using the induced voltage and the supply of commercial AC power is stopped, the energy stored in the backup element is converted by a converter circuit provided in the charging circuit without passing through a conversion transformer. Discloses a power supply device for supplying converted power to a load.

[0003] Japanese Patent Application Laid-Open No. 8-275521 discloses that a constant current circuit is connected to a secondary winding of a conversion transformer constituting a power conversion circuit, a battery is charged by the constant current circuit, and the battery is charged when a commercial AC power source fails. A power supply device that supplies a charging voltage to an inverter and supplies power from the inverter to a load is disclosed.

The reason why a backup circuit is provided with a converter is to stabilize a DC voltage supplied to a load even during backup by a battery and to control a battery charging voltage.

[0005]

By the way, in a switching power supply using a commercial power supply, a harmonic current generated by the switching operation flows to the commercial AC power supply side, which adversely affects the power system. As means for coping with this, various high-frequency current suppressing means have been proposed. The most common high-frequency current suppression means is active.
This is a high-frequency current suppression converter called a filter.

As can be seen in the prior art documents mentioned above,
The conventional switching power supply is provided with a dedicated converter for converting the power of a backup battery, separately from a main converter that operates using a commercial AC power supply as an input, and is configured to cope with a power failure of the AC power supply by switching between both converters. . Therefore, when a converter for suppressing a high-frequency current is used to cope with the regulation of the harmonic current, three converters of a main converter, a backup converter and a converter for suppressing a high-frequency current are required. For this reason, the number of parts increases remarkably, resulting in an increase in size and cost.

An object of the present invention is to provide a battery backup type switching power supply having a harmonic current suppressing function.

Another object of the present invention is to provide a battery-backup type switching power supply which has a small number of parts and is effective for miniaturization and cost reduction.

[0009]

In order to solve the above-mentioned problems, a switching power supply according to the present invention comprises an input circuit, a main converter, and a backup circuit. Converter and a smoothing capacitor. The rectifier circuit rectifies and outputs a commercial AC voltage. The harmonic current suppressing converter switches a rectified output of the rectifier circuit. The smoothing capacitor is charged by a switching output of the harmonic current suppressing converter.

The main converter switches a DC voltage appearing between terminals of the smoothing capacitor, converts a switching output into a DC voltage, and supplies a DC output voltage to a load.

[0011] The backup circuit includes a secondary battery and a charge / discharge circuit. When the AC voltage is supplied, the secondary battery is charged by energy supplied from the input circuit or the main converter. When the supply of the AC voltage is stopped, the energy stored in the secondary battery is discharged to supply the DC output voltage to the load.

In the switching power supply according to the present invention,
The input circuit includes a rectifier circuit, a converter for suppressing harmonic current, and a smoothing capacitor. Then, the commercial AC voltage is rectified and output by the rectifier circuit, the rectified output of the rectifier circuit is switched by the harmonic current suppression converter, and the smoothing capacitor is charged by the switching output of the harmonic current suppression converter. A typical example of this configuration is active. By controlling the switching operation of the harmonic current suppression converter, which is a filter, a substantially continuous pseudo sine wave current can be made to flow to the commercial AC power supply side, so that the harmonic current can be suppressed.

The main converter switches the DC voltage appearing between the terminals of the smoothing capacitor, converts the switching output to a DC voltage, and supplies the DC output voltage to the load. Can supply a DC output voltage from the main converter to the load.

The secondary battery constituting the backup circuit includes:
When the AC voltage is supplied, the battery is charged by the energy supplied from the input circuit. As described above, the input circuit includes the converter for suppressing harmonic current, and the output voltage is almost stabilized. In the present invention, this characteristic of the converter for suppressing harmonic current is utilized, and the secondary battery of the backup circuit is charged by the output voltage.

In some cases, the secondary battery is charged with energy supplied from the main converter. In this case, the secondary battery can be charged with a more stabilized voltage.

In this case, the output voltage of the harmonic current suppressing converter is made substantially proportional to the charging voltage of the secondary battery (substantially equal to the full charging voltage). With such a configuration, the secondary battery can be directly charged using the output voltage of the harmonic current suppression converter without requiring a converter for charging. In the backup operation, the charging voltage of the secondary battery can be directly converted by the main converter.

Therefore, in the present invention, since a converter dedicated to the backup circuit is not required, it is possible to obtain a switching power supply having a small number of parts and having a harmonic current suppressing function effective for downsizing and cost reduction. Can be.

The backup circuit discharges energy stored in the secondary battery and supplies a DC output voltage to the load when the supply of the AC voltage is stopped. Thereby, when the commercial AC power supply is interrupted, backup can be performed using the energy stored in the secondary battery.

The secondary battery included in the backup circuit is
It can be arranged on the secondary side of the conversion transformer. In this case, the output voltage of the harmonic current suppression converter may be set to the converted charging voltage of the secondary battery via the conversion transformer. According to this configuration, even if the charging voltage of the secondary battery is significantly different from the input voltage of the main converter when the commercial AC power is input power, the winding of the conversion transformer connected to the backup circuit, By selecting the turns ratio of the windings of the conversion transformer connected to the main converter, the secondary battery of the backup circuit can be directly charged by the forward voltage generated in the windings.

Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The drawings are merely examples.

[0021]

FIG. 1 is an electric circuit diagram of a switching power supply according to the present invention. As shown, the switching power supply according to the present invention includes an input circuit 1 and a main converter 2.
And a backup circuit 3. Reference numeral 4 indicates a control circuit.

The input circuit 1 includes a rectifier circuit 11, a converter 12 for suppressing harmonic current, and a smoothing capacitor 13. The rectifier circuit 11 rectifies and outputs the commercial AC voltage Ein supplied to the AC input terminals 61 and 62. The illustrated rectifier circuit 11 is a full-wave rectifier circuit including a diode bridge.

The harmonic current suppressing converter 12 switches the rectified output of the rectifier circuit 11. The smoothing capacitor 13 is charged by the switching output of the harmonic current suppression converter 12. A typical example of such a configuration is active. Filter. Active. By controlling the switching operation of the filter type harmonic current suppressing converter 12, a substantially continuous pseudo sine wave current can be supplied to the commercial AC power supply e side. Rate can be improved. Therefore, the harmonic current suppressing converter 12 can also be called a power factor improvement circuit. Since the power factor correction circuit is called a PFC circuit (Power Factor correction Circuit) by those skilled in the art, the converter 12 for suppressing harmonic current is hereinafter referred to as a PFC converter.

The main converter 2 switches the DC voltage V1 appearing between the terminals of the smoothing capacitor 13, converts the switching output into a DC voltage, and supplies the load L with the DC output voltage Vo. In the embodiment, the main converter 2
Includes a power conversion circuit 21 and an output circuit 22. The power conversion circuit 21 includes a conversion transformer 23 and a switch element 2
4 is included. The conversion transformer 23 includes a first winding 23
The first winding 231 receives the DC voltage V1 from the input circuit 1 including the first and second windings 232.

The switching element 24 switches the DC voltage V1 supplied through the first winding 231. The switch element 24 receives the signal S1 supplied from the control circuit 4.
Controls the switching operation. Signal S
1 is usually given as a pulse width modulated signal. The switch element 24 is controlled by the pulse width modulation signal S1 so that the DC output voltage Vo becomes constant. The switch element 24 is typically constituted by a field effect transistor (FET), but may be another three-terminal switch element such as a bipolar transistor. The main electrode circuit of the switch element 24 is connected in series to the first winding 231 of the conversion transformer 23.

The output circuit 22 is connected to the second winding 232, converts a switch output appearing on the second winding 232 into a DC voltage, and supplies a DC output voltage Vo to the load L.
The illustrated output circuit 22 constitutes a so-called forward converter circuit, and stores a diode 221 that conducts when the switch element 24 is on and a choke coil 223 while the switch element 24 is off. A rectifier circuit including a diode 222 that emits the converted energy, and an output smoothing capacitor 224.
However, it is needless to say that the present invention is not limited to such a circuit configuration.

The backup circuit 3 includes a secondary battery 31 and
And a charge / discharge circuit 32. When the commercial AC power supply e is normal and the AC voltage Ein is supplied, the input circuit 1
The secondary battery 31 is charged by the energy supplied from. In the embodiment, the charging / discharging circuit 32 includes a charging circuit including a diode 33 and a current limiting resistor 34, and a discharging circuit including a switch element 35. During charging, the switch element 35 is off,
The secondary battery 31 is charged through a charging circuit including a diode 33 and a current limiting resistor 34. When the switch element 35 is turned on, the electric charge accumulated in the secondary battery 31 becomes
It is discharged through the switch element 35. Switch element 3
The switching operation of 5 is controlled by a signal S2 supplied from the control circuit 4.

In the switching power supply according to the present invention, the case where the AC power supply e is normal and the AC voltage Ein is supplied to the AC input terminals 61 and 62 will be described. The input circuit 1 uses the rectifier circuit 11 to supply the commercial AC voltage E
rectified and output by the PFC converter 12
The rectification output of the rectification circuit 11 is switched, and the smoothing capacitor 13 is charged by the switching output of the PFC converter 12. At this time, by controlling the switching operation of the PFC converter 12, a substantially continuous pseudo sine wave current can be caused to flow toward the commercial AC power supply e, so that harmonic current can be suppressed.

The main converter 2 switches the DC voltage V1 appearing between the terminals of the smoothing capacitor 13, converts the switching output into a DC voltage, and supplies the load L with the DC output voltage Vo. That is, from the AC power supply e to the input terminal 6
The DC output voltage Vo is supplied from the main converter 2 to the load L while the AC voltage Ein is normally supplied to 1, 62.

Secondary battery 3 constituting backup circuit 3
1 is charged by the energy supplied from the input circuit 1. During charging, the switch element 35 is off,
The secondary battery 31 is charged through a charging circuit including a diode 33 and a current limiting resistor 34. Input circuit 1
Includes the PFC converter 12, as described above, and its output voltage V1 is almost stabilized. In the present invention, utilizing this characteristic of the PFC converter 12, the secondary battery 31 of the backup circuit 3 is charged to the charging voltage V2 by the output voltage V1.

The output voltage V1 of the PFC converter 12 is
It is made substantially proportional to the charging voltage V2 of the secondary battery 31. In the case of the embodiment, the output voltage V1 of the PFC converter 12 is substantially equal to the charging voltage V2 of the secondary battery 31 (proportionality constant 1).
With such a configuration, the secondary battery 31 can be directly charged using the output voltage V1 of the PFC converter 12. In the backup operation, the secondary battery 31
Can be directly converted by the main converter 2.

Therefore, in the present invention, since a converter dedicated to the backup circuit 3 is not required, a switching power supply having a small number of parts and having a harmonic current suppressing function effective for downsizing and cost reduction is obtained. be able to.

Next, the AC power supply e is cut off, and the input terminal 6
The case where the supply of the AC voltage Ein to the first and the second 62 is stopped will be described. In this case, the switch element 35 of the backup circuit 3 turns on. When the switch element 35 is turned on, the electric charge accumulated in the secondary battery 31 is discharged through the switch element 35. In the case of the embodiment, the charging voltage V2 of the secondary battery 31 is supplied to the winding 231 of the conversion transformer 23 constituting the main converter 2 through the switch element 35.
And the main switch element 14. And
The charging voltage V2 of the secondary battery 31 is switched by the switch element 24, and the switching output is transmitted from the winding 231 of the conversion transformer 23 to the winding 232. The switching output appearing on the winding 232 is converted to a DC voltage by the output circuit 22 and applied to the load L by the DC output voltage Vo.
Is supplied.

FIG. 2 is an electric circuit diagram showing still another embodiment of the switching power supply according to the present invention. In the figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals. The feature of this embodiment is that the backup secondary battery 31 is disposed on the secondary side of the conversion transformer 23 and the third winding 23 provided in the conversion transformer 23 is provided.
2 is connected. Next, a specific description will be given.

The backup circuit 3 includes a charge / discharge circuit 32
, The third winding 233, and the secondary battery 31. In the illustrated charging / discharging circuit 32, the third winding 2
A circuit loop including the diode 23, the diode 33, the current limiting resistor 34, and the secondary battery 31 forms a charging circuit CH. When the main switch element 24 is turned on, the diode 33 constituting the charging circuit CH is connected to the forward voltage V appearing in the third winding 233 having the illustrated polarity (shown by a black circle in the figure).
It is oriented so as to be forward with respect to F.
In the charging circuit CH, a rectifying / smoothing circuit is formed by the diode 33 and the capacitor 37. The rectifying / smoothing circuits 33 and 37 rectify and smooth the forward voltage VF, and charge the secondary battery 31 with the rectified and smoothed voltage. .

Further, a circuit loop including the secondary battery 31, the diode 36, the third winding 233, and the switch element 35 forms a discharge circuit. The diode 36 forming the discharge circuit DH is oriented so as to be forward with respect to the forward voltage VF. Reference numeral 37 is a capacitor.

The switch element 35 is composed of a three-terminal element, and is connected so that the main electrode circuit is in series with the discharge circuit DH including the third winding 233 and the secondary battery 31. A three-terminal element suitable for the switch element 35 is an FET. When the switch element 35 is an FET, the source of the FET. Since the inter-drain diode can be used as the diode 33, the circuit configuration of the charge / discharge circuit 32 can be further simplified.

When the main converter 2 is operating, the backup circuit 3 is switched so that the charging / discharging circuit 32 becomes the charging circuit CH. When switching to the charging circuit CH is performed, the secondary battery 31 is charged by the electric power supplied from the third winding 233 of the conversion transformer 23. Therefore, by the switching operation of the power conversion circuit 21,
The secondary battery 31 is charged by the voltage induced in the third winding 233 of the conversion transformer 23. In the circuit configuration shown in the embodiment, charging of the secondary battery 31 is performed by the forward voltage VF appearing on the third winding 233 during the ON period of the main switch element 24. Since the DC voltage V1 input to the main converter 2 is stabilized to some extent by the PFC converter 12, the voltage that can be obtained by rectifying and smoothing the forward voltage VF appearing in the third winding 233 is also substantially stable. I have. Therefore, the secondary battery 31 can be charged with the stabilized forward voltage VF.

In the embodiment shown in FIG. 2, the output voltage V1 of the PFC
Is set to the charging voltage V2 of the secondary battery 31 converted between the winding 233 and the first winding 231. The conversion factor includes a turn ratio between the third winding 233 and the first winding 231 and a leakage inductance. With this configuration, even if the charging voltage V2 of the secondary battery 31 is significantly different from the input voltage of the main converter 2 when the commercial AC power supply e is used as input power, the conversion transformer 23 connected to the backup circuit 3 A third winding 233,
By appropriately selecting the turns ratio of the first winding 231 of the conversion transformer 23 connected to the main converter 2, the forward winding generated in the third winding 233 can be performed without requiring a converter or the like. The secondary battery 31 of the backup circuit 3 can be charged by the voltage VF.

Next, when the AC power supply e fails, the backup circuit 3 is switched to the discharge circuit DH. When the mode is switched to the discharge mode, the secondary battery 31 becomes a power supply source. The switch element 35 of the backup circuit 3 performs a switching operation under the control of the control signal S2 supplied from the control circuit 4, switches the energy supplied from the secondary battery 31, and outputs the switching output to the third winding 233. To supply.

The third winding 233 is a winding of the conversion transformer 23 and is inductively coupled to the second winding 232 of the conversion transformer 23, and thus switches the energy supplied from the secondary battery 31. The third current is obtained by the obtained current.
When the winding of the winding 233 is excited, the energy is transmitted from the third winding 233 to the second winding 232.
The output circuit 22 is connected to the second winding 232 of the conversion transformer 23.
Is connected, the switching output of the backup circuit 3 appearing in the second winding 232 is converted into a DC voltage by the output circuit 22, and the DC output voltage Vo is supplied to the load L.

As is apparent from the above description, in the embodiment shown in FIG.
Each component that should be provided in the switching power supply,
That is, since the conversion transformer 23 and the output circuit 22 are shared with the main converter 2 to supply the energy of the secondary battery 31 to the load L, the number of components is reduced and the size is reduced. Can be achieved.

Further, the backup operation by the backup circuit 3 can be easily realized by selecting the switch element 35 and the main switch element 24 which constitute the charge / discharge circuit 32.

FIG. 3 is an electric circuit diagram showing still another embodiment of the switching power supply according to the present invention. 3, the same components as those shown in FIG. 2 are denoted by the same reference numerals. In this embodiment, P
Control circuit 1 for controlling output voltage V1 of FC converter 2
7, the output voltage signal S4 of the backup circuit 3 is fed back to the control circuit 17. With such a configuration, even when the forward voltage VF generated in the third winding 233 fluctuates under the condition of the load L, the charging voltage signal S4, which is a rectified smoothed voltage, is fed back to the control circuit 17, and the PFC converter 12 Can be controlled so that the forward voltage VF is stabilized. Therefore, the secondary battery 31 can be charged so as to have a constant charging voltage regardless of a load change or the like.

FIG. 3 also shows a specific circuit configuration of the PFC converter 12. The illustrated PFC converter 12 is a very common boost type active. A filter, a switch element 14, an inductor 15,
And a diode 16. Reference numeral 17 is a control circuit,
Reference numeral 18 is a current detection resistor.

In the PFC converter 12, the energy stored in the inductor 15 during the ON period of the switch element 14 is transferred to the smoothing capacitor 13 through the diode 16 when the switch element 14 is OFF. A superimposed voltage of a rectified voltage output from the rectifier circuit 11 and an electromotive force generated in the inductor 15 is applied to the smoothing capacitor 13. The control circuit 17 for controlling the switching operation of the switch element 14 receives a current detection signal S7, an output voltage detection signal S3, and a voltage signal S6 for detecting a power failure, which are supplied from the current detection element 18,
The control circuit 17 controls the switch element 14 based on these signals so that a substantially continuous pseudo sine wave current flows to the commercial AC power supply e.

Next, the impedance of the secondary battery 31 generally varies depending on the temperature. Therefore, the ambient temperature of the secondary battery 31 or the temperature of the secondary battery 31 is detected, a temperature detection signal is supplied to the control circuit 17, and the output voltage V1 of the PFC converter 12 is changed according to the temperature. . FIG. 4 shows a specific example.

In FIG. 4, the output voltage V1 of the PFC converter 12 is divided by resistors 171 and 172, and the ambient temperature of the secondary battery 31 or the temperature of the secondary battery 31 is set in parallel with the resistor 172. A temperature detecting element 173 to be detected is connected. Resistance 171 and resistance 1
The connection point between the temperature detection element 72 and the temperature detection element 173 is connected to the input terminal (+) of the error amplifier 175. Error amplifier 1
A reference voltage from a reference voltage source 174 is supplied to the other input terminal (−) of 75. The error amplification signal S5 of the error amplifier 175 is supplied to a control unit 176 forming the control circuit 17. As the temperature detecting element 173, an NTC thermistor is generally used, but a PTC thermistor or the like may be used.

In the circuit of FIG. 4, it is assumed that the secondary battery 31 has a characteristic that the charging voltage decreases as the temperature increases.
The case where an NTC thermistor is used as the temperature detecting element 173 will be described as an example. When the ambient temperature of the secondary battery 31 or the temperature of the secondary battery 31 rises,
The resistance value of the NTC thermistor constituting the temperature detection element 173 decreases, and an error occurs between the divided voltage input to the input terminal (−) of the error amplifier 175 and the reference voltage input to the input terminal (+). Is generated. This error is amplified by the error amplifier 175 and input to the control unit 176. Control unit 1
Reference numeral 76 controls the PFC converter 12 in a direction to reduce the output voltage V1 of the PFC converter 12 and eliminate the error. Thereby, the output voltage V of the PFC converter 12
1 can be changed to follow the temperature. In the embodiment of FIG. 4, the error amplifier 175 has a PFC
Instead of the output voltage V1 of the converter 12, the charging voltage V
2 may be supplied.

Although the contents of the present invention have been described with reference to the specific embodiments, those skilled in the art can make various modifications and alterations based on the basic technical idea and teaching of the present invention. It is obvious that it is possible.

[0051]

As described above, according to the present invention, it is possible to provide a battery-backup-type switching power supply having a harmonic current suppressing function, a small number of parts, and effective for downsizing and cost reduction. it can.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a switching power supply according to the present invention.

FIG. 2 is an electric circuit diagram showing another embodiment of the switching power supply according to the present invention.

FIG. 3 is an electric circuit diagram showing still another embodiment of the switching power supply according to the present invention.

FIG. 4 is an electric circuit diagram of a control circuit used in the switching power supply according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input circuit 2 Main converter 21 Power conversion circuit 22 Output circuit 3 Backup circuit 31 Secondary battery 32 Charge / discharge circuit

Claims (6)

[Claims] 1. A switching power supply including an input circuit, a main converter, and a backup circuit, wherein the input circuit includes a rectifier circuit, a harmonic current suppression converter, and a smoothing capacitor. The rectifier circuit rectifies and outputs a commercial AC voltage, the converter for harmonic current suppression switches a rectified output of the rectifier circuit, the smoothing capacitor is charged by a switching output of the converter for harmonic current suppression, The main converter switches a DC voltage appearing between the terminals of the smoothing capacitor, converts a switching output to a DC voltage, and supplies a DC output voltage to a load.The backup circuit includes a secondary battery, a charging / discharging circuit. And the energy supplied from the input circuit or the main converter when the AC voltage is supplied. Therefore, when the secondary battery is charged and the supply of the AC voltage is stopped, the energy stored in the secondary battery is discharged to supply the DC output voltage to the load, and the harmonic current suppressing converter A switching power supply, wherein the output voltage of the switching power supply is approximately proportional to the charging voltage of the secondary battery. 2. The switching power supply according to claim 1, wherein the backup circuit is connected to the smoothing capacitor in parallel. 3. The switching power supply according to claim 1, wherein the main converter includes a conversion transformer that transmits the switching output to the load side. A switching power supply shared by the main converter and the backup circuit; 4. The switching power supply according to claim 3, wherein an output voltage of the harmonic current suppression converter is set to a charging voltage of the secondary battery converted via the conversion transformer. Switching power supply. 5. The switching power supply according to claim 1, further comprising a control circuit for controlling an output voltage of the harmonic current suppressing converter, wherein the control circuit includes: Switching power supply to which the output voltage signal of the backup circuit is fed back. 6. The switching power supply according to claim 5, wherein the control circuit is supplied with a temperature detection signal of the secondary battery, and detects an output voltage of the harmonic current suppression converter by the temperature detection. Switching power supply controlled based on signals.