JP3568666B2 - DC power supply - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a DC power supply device used for OA equipment and the like, and more particularly to a DC power supply device including a rectifier circuit for full-wave rectification of an AC input from an AC power supply and a DC / DC converter having a switching element.
[0002]
[Prior art]
In recent years, energy saving has been proposed as one of the countermeasures against global environmental problems, and high efficiency is also required for switching power supplies that are widely used as DC power supply devices for electronic devices. In order to meet the demand, there are a method of achieving energy saving by increasing efficiency in a wide range of output power to the load, and a method of achieving energy saving by increasing efficiency during standby of the electronic device body.
In order to increase the efficiency of such switching power supplies, various circuit schemes have been conventionally proposed. However, a rectifier circuit for full-wave rectification of alternating current input from an AC power supply and a one-output forward type DC / DC converter are provided. A description will be given of an example of a DC power supply device configured as follows.
[0003]
FIG. 8 is a circuit diagram showing an example of a conventional DC power supply device. This DC power supply device includes a rectifying and smoothing circuit 2 and a forward type DC / DC converter 3. The rectifying and smoothing circuit 2 includes a diode bridge 20, which is a full-wave rectifying circuit including diodes D1 to D4, and a smoothing capacitor C1 connected between its output terminals a and b. Power supply 1 is connected.
The output of the rectifying and smoothing circuit 2 becomes the input of the DC / DC converter 3. Between the output terminals a and b of the diode bridge 20, a series circuit of a resistor R2 and a resistor R3, which are starting resistors, is connected.
[0004]
The positive output terminal a of the diode bridge 20 and one end g of the primary winding L1 of the transformer T1 of the DC / DC converter 3 are connected by a line 16, and the other end h of the primary winding L1 is connected to the anode of a diode D5. One end of a parallel circuit of a resistor R1 and a capacitor C2 is connected to the cathode, and the other end of the parallel circuit is connected to a line 16 to form a snubber circuit.
The switching element Q1 is connected between the other end h of the primary winding L1 and the negative output terminal b of the diode bridge 20, and the gate of the switching element Q1 is connected to the control output terminal of the control circuit 4.
[0005]
Further, an anode of a diode D6 is connected to one end i of a drive power supply winding L2 of the transformer T1, an end of an inductor L4 is connected to its cathode, and a cathode of a diode D7 is connected to a connection point between the diode D6 and the inductor L4. And the anode is connected to the other end j of the drive power supply winding L2. The other end j and the negative output terminal b of the diode bridge 20 are connected by a line 17, the other end of the inductor L4 is connected to the line 17 via a capacitor C3, and a voltage dividing point by resistors R2 and R3. A drive power supply is formed by directly connecting to the drive circuit d, and the voltage at the point d of the drive power supply is applied to the control circuit 4 for controlling ON / OFF of the switching element Q1.
[0006]
An anode of a diode D8 is connected to one end k of a secondary winding L3 of the transformer T1, one end of an inductor L5 is connected to its cathode, and one end of a smoothing capacitor C4 is connected to the other end of the inductor L5. The cathode of diode D9 is connected to the connection point between D8 and inductor L5, and the anode of diode D9 and the other end of capacitor C4 are connected to the other end m of secondary winding L3 to form a rectifying and smoothing circuit.
[0007]
Both ends of the capacitor C4 are connected to output terminals 6 and 7 of the DC / DC converter 3. A voltage detection circuit 5 for detecting the output voltage of the DC / DC converter 3 is connected between the output terminals 6 and 7, and the detection output of the voltage detection circuit 5 is fed back to the control circuit 4.
Note that a generally well-known noise filter may be interposed between the AC power supply 1 and the rectifier circuit 2.
[0008]
The operation of this circuit will be described. When AC is input from the AC power supply 1, full-wave rectification and smoothing are performed in the rectifying and smoothing circuit 2, and a substantially DC voltage is obtained. The substantially DC voltage is applied to the starting resistors R2 and R3, and the smoothing capacitor C3 for the driving power supply is charged by the divided voltage at the point d. When the charged voltage exceeds a certain value, the DC / DC converter 3 Control circuit 4 starts operating, outputs a pulse for turning on / off switching element Q1, and drives switching element Q1.
[0009]
When the switching element Q1 is turned on / off, a current flows intermittently in the primary winding L1 of the transformer T1, and an alternating high voltage is induced in the secondary winding L3, which is caused by the diodes D8 and D9, the inductor L5 and the inductor L5. DC voltage is output between the output terminals 6 and 7 after being rectified and smoothed by the smoothing capacitor C4.
The output voltage is detected by the voltage detection circuit 5 and fed back to the control circuit 4, and the control circuit 4 appropriately controls the pulse width for driving the switching element Q1 so that the output voltage becomes a predetermined voltage.
[0010]
At this time, an AC voltage is also induced in the driving power supply winding L2 of the transformer T1, and is rectified and smoothed by the diodes D6 and D7, the inductor L4, and the capacitor C3. , And the DC / DC converter 3 enters a continuous operation state. In this state, the voltage at the voltage dividing point d between the starting resistors R2 and R3 becomes substantially equal to the voltage between both terminals of the capacitor C3, and the resistance value is set so that almost no current flows through the starting resistors R2 and R3. Have been.
[0011]
FIG. 9 shows another example of a conventional DC power supply device, which includes a diode bridge 20 which is a rectifier circuit for performing full-wave rectification of AC from an AC power supply, a step-up chopper type active filter 13, and a one-output forward filter. And a DC / DC converter 3 of the system. In FIG. 9, the same portions as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.
[0012]
Here, the difference from the DC power supply device shown in FIG. 8 is that only the diode bridge 20 which is a full-wave rectification circuit is used instead of the rectification and smoothing circuit 2 in FIG. 8, and the diode bridge 20 and the DC / DC converter 3 During this time, the input current waveform is controlled to be a sine wave to improve the power factor, and a boost chopper type active filter 13 is interposed as a power factor improving circuit for reducing harmonic components of the input current. Is a point.
[0013]
The active filter 13 includes an inductor L6 and a diode D10 inserted in series with a positive line 16 connecting the diode bridge 20 and the DC / DC converter 3, and a current detecting resistor R4 inserted through a negative line 17. A capacitor C5 connected between the cathode side of the diode 10 of the positive line 16 and the output side of the resistor R4 of the negative line 17, a connection point between the inductor L6 and the anode of the diode D10, and a resistance of the negative line 17; The switching element Q3 is connected to the output side of R4, and the control circuit 14 controls the switching element Q3 to turn on and off.
[0014]
According to the DC power supply device shown in FIG. 9, when AC is input from the AC power supply 1 to the diode bridge 20, full-wave rectification is performed to form a pulsating flow. The pulsating current is applied to the series circuit of the starting resistors R2 and R3, and the voltage of the divided point d charges the smoothing capacitor C3 for the driving power supply. When the charged voltage exceeds a predetermined value, the active filter 13 is turned on. Of the control circuit 14 and the control circuit 4 of the DC / DC converter 3 start operating, and output pulses for driving the respective switching elements Q1 and Q3 on / off.
[0015]
The active filter 13 approximates the input current waveform to be similar to the input voltage waveform by turning on / off the switching element Q3, and the output voltage rectified and smoothed by the diode D10 and the smoothing capacitor C5 becomes a predetermined voltage. Control. When the DC / DC converter 3 enters the continuous operation state, the drive voltage is also supplied from the capacitor C3 to the control circuit 14 of the active filter 13, and the active filter 13 also enters the continuous operation state.
[0016]
[Problems to be solved by the invention]
According to the DC power supply device shown in FIG. 8, AC power input from the AC power supply 1 between the input terminals 21 and 22 is extracted as DC power from between the output terminals 6 and 7. The conversion efficiency at this time is as follows. Usually, it is about 75 to 85%. 15 to 25% of the input power is a loss inside the circuit of the DC power supply.
[0017]
The main loss points are an input noise filter (not shown), a diode bridge 20 and a capacitor C1 of the rectifying / smoothing circuit 2, a transformer T1 of the DC / CD converter 3, a switching element Q1, a control circuit 4, a voltage detection circuit 5, A secondary rectifying / smoothing circuit and an output noise filter (not shown). In the case of the forward type DC / DC converter 3 as shown in FIG. 8, the ratio of the loss of the switching element Q1 to the total loss is usually 20 to 30%, which is considerably large.
[0018]
One method for reducing the loss of the switching element is to increase the switching speed. However, the rating is selected mainly according to the switching frequency, the input voltage, the maximum output power, and the like. An FET transistor which is frequently used as a switching element for a DC / DC converter of several tens kHz to several hundreds kHz generally has an output power of As the value becomes larger, the turn-on time and the turn-off time become longer, and the switching speed decreases.
[0019]
This is the same as operating with a switching element that has a lower switching speed when operating at an output power smaller than the maximum output power compared to a switching element that can switch at the lower output power. As a result, the ratio of the loss of the switching element to the total loss increases, which leads to a decrease in efficiency. As a result, the efficiency of the output power of several tens to several hundreds of watts is about 75 to 85% at the maximum output power, but the efficiency decreases as the output power decreases, and the output power is 10% or less of the maximum output power. Has a drawback of about 40 to 50%.
[0020]
Also, in the DC power supply device shown in FIG. 9, there is a place where power loss occurs in the same manner as described in the DC power supply device shown in FIG. L6, a diode D10, a smoothing capacitor C5, a switching element Q3, a resistor R4, and a loss in the control circuit 14 are added. That is, the loss with respect to the output power of switching element Q3 in FIG. 9 is similar to the loss in switching element Q1 described in FIG. 8, and in the DC power supply device shown in FIG. The decrease is even more remarkable as compared with the DC power supply shown in FIG.
[0021]
That is, in a DC power supply device configured with a rectifier circuit and a DC / DC converter used for OA equipment or the like, or provided with an active filter therebetween, a switching element used for the DC / DC converter and the active filter is: Since the one that can operate at the expected maximum power is used, the lighter the load, the higher the ratio of the loss to the output power, and the lower the efficiency.
[0022]
The present invention has been made in view of the above points, and in a DC power supply device using a switching element, reduces power loss due to the switching element even when operating at an output power considerably lower than the rated power, An object of the present invention is to improve the efficiency of a DC power supply.
[0023]
[Means for Solving the Problems]
The present invention provides a secondary transformer of a transformer by turning on / off a rectifier circuit for full-wave rectifying an alternating current input from an AC power supply and a switching element connected in series with a primary winding of the transformer to which an output of the rectifier circuit is input. In order to achieve the above object, in a DC power supply device comprising a DC / DC converter for rectifying and smoothing a voltage induced in a winding and outputting the same, a plurality of switching elements of the DC / DC converter are provided in parallel, Current detecting means for detecting an output current of the / DC converter or a current proportional to the output current; and one of the plurality of switching elements when a current value detected by the current detecting means is smaller than a preset value. Leaving all other switching elements inactive except forFirstNon-operation control means andIs provided.
Further, an active filter for improving a power factor is provided between the rectifier circuit and the DC / DC converter by turning on / off a switching element. A plurality of switching elements of the active filter are provided in parallel. A second non-operation control unit that, when the detected current value is smaller than a predetermined value, turns off the other switching elements except for one of the plurality of switching elements of the active filter and keeps the other switching elements in an inactive state; Is provided.
[0024]
Alternatively, the switching elements other than one of the plurality of switching elements of the DC / DC converter are set to the non-operation state in which the switching elements are kept off by a signal input from the outside without using the current detection unit.FirstNon-operation control means;Second non-operation control means for setting other switching elements except one of the plurality of switching elements of the active filter to an inoperative state in which the switching elements remain off by a signal also input from the outside;May be provided.
[0025]
[0026]
[0027]
According to the invention, Rectifier circuitDC power supply device composed of a DC / DC converter and an active filter, DC/ DC converter and active filter switching elementRespectivelyMultipleEachWhen the output current of the DC / DC converter is small (light load), each of the other switching elements is left except for one of the switching elements.ToBy setting the device to a non-operating state in which the switching device remains off, power loss due to the switching element can be reduced and efficiency can be improved.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present inventionReference Example andEmbodiments will be specifically described with reference to the drawings.
FIG. 1 and3 and 4 are circuit diagrams of a DC power supply device showing a reference example on which the present invention is based, respectively.FIG. 7 to FIG.ThirdFIG.TherePortions corresponding to the circuit diagrams of the conventional example shown in FIGS. 8 and 9 described above are denoted by the same reference numerals, and description thereof is omitted.
[0029]
[FirstReference example]
First, the first type shown in FIG.Reference exampleWill be described.
The circuit configuration of the DC power supply shown in FIG. 1 is similar to the circuit configuration of the conventional DC power supply shown in FIG. 8, but differs in the following points.
In the DC / DC converter 3, another switching element Q2 is connected in parallel with the switching element Q1, and the switching element Q1 and the switching element Q2 are driven by a drive pulse from the control circuit 4. However, an on / off circuit 10 is interposed between the drive pulse output terminal of the control circuit 4 and the gate of the switching element Q2, and the drive pulse from the control circuit 4 is supplied to the on / off circuit 10.ToThrough the gate of the switching element Q2.
[0030]
Further, a current detection circuit 8 as current detection means for detecting an output current of the DC / DC converter 3 is inserted on the m side of the secondary winding L3 of the transformer T1. Then, a comparison circuit 9 for comparing the current value detected by the current detection circuit 8 with a reference value is provided. According to the comparison result, the on / off circuit 10 is in a non-operating state in which the switching element Q2 remains off, or The operation state is set to one of the operation states in which on / off is repeated by the drive pulse from the control circuit 4. The comparison circuit 9 and the ON / OFF circuit 10 constitute non-operation control means.
[0031]
The operation of this DC power supply will be described. The AC from the AC power supply 1 is rectified and smoothed by the rectifying and smoothing circuit 2. The output voltage is input to the DC / DC converter 3 and applied to the series circuit of the starting resistors R2 and R3, and the driving power supply capacitor C3 is charged by the divided voltage at the point d. When the charging voltage becomes equal to or higher than a predetermined value, the control circuit 4 starts operating, and outputs a driving pulse to the switching element Q1 and the switching element Q2 via the on / off circuit 10.
[0032]
As a result, the switching element Q1 and the switching element Q2 are turned on / off in parallel, so that the current flowing through the primary winding L1 of the transformer T1 is interrupted, and an AC high voltage is induced in the secondary winding L3. The alternating current is rectified and smoothed by diodes D8 and D9, inductor L5 and capacitor C4, and a DC voltage is output between output terminals 6 and 7. The voltage detection circuit 5 detects the DC voltage and feeds it back to the control circuit 4, so that the control circuit 4 controls ON / OFF of the switching elements Q1 and Q2 so that the output voltage becomes a predetermined voltage. I do.
[0033]
A load (not shown) is connected between the output terminals 6 and 7 of the DC / DC converter 3, and the value of a current flowing through the load is detected by a current detection circuit 8. A current value (a value converted into a voltage) detected by the current detection circuit is input to a comparison circuit 9, which compares the current value with a preset reference value, and turns on / off a signal of the comparison result. Output to the circuit 10. When the detected current value is smaller than the reference value, the ON / OFF circuit 10 does not apply the drive pulse from the control circuit 4 to the gate of the switching element Q2, and the switching element Q2 is forcibly kept off. Set to operation state.
[0034]
In this case, only the switching element Q1 performs the switching operation of the primary current of the transformer T1 alone, so that the switching loss and the drive loss of the switching element Q2 can be eliminated, and the efficiency of the DC power supply device can be improved. it can.
Note that the switching elements Q1 and Q2 have a rated current that is １ ／ of that of the switching element Q1 of the conventional DC power supply device shown in FIG.
[0035]
When detecting the AC current by inserting the current detection circuit 8 at the position shown in FIG. 1, a current transformer or a resistor having a small resistance value for current detection can be used. May be detected by a resistor. Alternatively, the current detection circuit 8 may be located anywhere where a current value proportional to the output current of the DC / DC converter 4, such as the current on the primary side of the transformer T1, the output current or the input current of the rectifying / smoothing circuit 2, can be detected. It may be interposed.
[0036]
Also, this firstReference exampleIn the above, two switching elements Q1 and Q2 are connected in parallel and used. However, when three or more switching elements are connected in parallel and the output current becomes smaller than a preset value, Alternatively, the other switching elements except one of the plurality of switching elements may be set to the non-operating state in which the switching elements remain off.
[0037]
FIG. 2 shows a specific circuit example of the current detection circuit 8, the comparison circuit 9, and the on / off circuit 10.
Briefly describing this, in FIG. 2, the current detection circuit 8 uses a current transformer CT to detect an alternating current. Then, the primary winding of the current transformer CT is connected in series between the m-side on the secondary winding side of the transformer T1 of the DC / DC converter 3 shown in FIG. 1 and the anode side of the diode D9.
[0038]
As a result, a current that is inversely proportional to the turns ratio with respect to the current flowing through the primary winding of the current transformer CT flows through the secondary winding. The current is converted into a voltage by the resistor R5, and the detected voltage Vd, that is, a voltage having a value proportional to the output current of the DC / DC converter 3 is input to the negative input terminal of the comparator 30 of the comparison circuit 9, and the 5 V The power supply voltage is divided by the resistors R6 and R7, and a predetermined reference voltage Vr is input to its + input terminal as a comparison voltage.
[0039]
When the output current of the DC / DC converter 3 decreases and the detection voltage Vd becomes lower than the reference voltage Vr, the comparator 30 outputs the + side saturation output voltage (high-level output) to the on / off circuit 10 via the diode D10. Output to Due to the output voltage, a base current flows through the transistor TR1 of the on / off circuit 10, and the transistor TR1 is turned on. As a result, the gate of the switching element Q2 of the DC / DC converter 3 is grounded, forcing the switching element Q2 into the non-operating state.
[0040]
Conversely, when the output current of the DC / DC converter 3 increases and the detection voltage Vd becomes higher than the reference voltage Vr, the output of the comparator 30 becomes low level (0 V) and the transistor TR1 of the on / off circuit 10 is turned off. Therefore, the drive pulse from the control circuit 4 is applied to the gate of the switching element Q2 to start the on / off operation. The capacitor C6 of the on / off circuit 10 is provided for giving a slight delay (time constant) to the on / off of the transistor TR1.
[0041]
Note that instead of the current transformer CT and the current-voltage conversion circuit of FIG. 3, a current detection resistor is connected in series between the m-side of the secondary winding of the transformer T1 and the anode of the diode D9, A voltage value proportional to the output current of the DC / DC converter 3 may be detected based on a voltage generated between both terminals of the resistor.
[0042]
[SecondReference example]
Next, the inventionThe basis ofSecondReference exampleWill be described with reference to FIG.
In the DC power supply device shown in FIG. 3, a resistor R4 is inserted into an output line connected to the negative output terminal b of the diode bridge 20 in the rectifying and smoothing circuit 2 as a current detecting means, and a voltage is generated between both ends of the resistor R4. The detected voltage is detected by the current detection circuit 11 to detect a current value proportional to the output current of the DC power supply device, and the detected value is input to the comparison circuit 9 only.But,This is different from the DC power supply device shown in FIG.
[0043]
In the DC power supply device shown in FIG. 3, a resistor R4 as a current detecting means and an input current detecting circuit 11 constantly detect an input current proportional to an output current between output terminals 6 and 7, and a comparing circuit 9 detects the input current. The detected current value is compared with a preset reference value, and when it is smaller than the reference signal, the on / off circuit 10 forcibly puts the switching element Q2 into a non-operation state. As a result, the switching element Q1 operates alone, switching loss and drive loss in the switching element Q2 can be eliminated, and the efficiency of the DC power supply can be improved.
[0044]
Here, the current detecting means detects the current using the resistor R4.InsteadAlternatively, a current transformer may be used, or a primary current flowing through the primary winding L1 of the transformer T1 may be detected.
[0045]
[ThirdReference example]
Next, the inventionThe basis ofThirdReference exampleWill be described with reference to FIG.
The DC power supply device shown in FIG. 4 is provided with an external signal input terminal 12, and an external signal input from the external signal input terminal 12 is input to the on / off circuit 10 to forcibly switch the switching element Q2. The only point that the device is configured to be in the non-operating state while being turned off is the first device shown in FIG.Reference exampleAnd different.
[0046]
For example, a signal generated by pressing a switching stop button on an operation panel (not shown) of the DC power supply, or a signal of a circuit controlling an electronic device equipped with the DC power supply is supplied to an external signal input terminal. 12 to the on / off circuit 10. In this case, the ON / OFF circuit 10 unconditionally puts the switching element Q2 into a non-operating state, and makes only the switching element Q1 operate alone. Thereby, the switching loss and the drive loss of the switching element Q2 can be eliminated, and the efficiency can be improved.
[0047]
[FirstEmbodiment]
Next, according to the inventionFirstThe embodiment will be described with reference to FIG.
The DC power supply device shown in FIG. 5 has a boost chopper type active filter 13 as a power factor improving circuit between a diode bridge 20 and a DC / DC converter 3 like the conventional DC power supply device shown in FIG. Is provided.
The configuration inside the DC / DC converter 3 is the first configuration shown in FIG.Reference exampleIs the same as
[0048]
The active filter 13 has two switching elements Q3 and Q4 connected in parallel between lines 16 and 17, and both are driven by a drive pulse from the control circuit 14. An on / off circuit 15 is interposed between the output terminal of the control circuit 14 and the gate of the switching element Q4, and the output signal of the comparison circuit 9 in the DC / DC converter 3 is also input to the on / off circuit 15. I have.
Note that the rated current of the switching elements Q3 and Q4 may be １ ／ of the switching element Q3 in the conventional example shown in FIG.
[0049]
In the DC power supply device shown in FIG. 5, similarly to the DC power supply device shown in FIG. 1, the current detection circuit 8 always detects the output current of the DC / DC converter 3, and the comparison circuit 9 outputs the detected current value. Is compared with a preset reference value, and a signal corresponding to the comparison result is output to both the ON / OFF circuit 10 and the ON / OFF circuit 15.
[0050]
here,The comparison circuit 9 and the on / off circuit 10 constitute first non-operation control means;The comparison circuit 9 and the on / off circuit 15 constitute second non-operation control means. When the current value detected by the current detection circuit 8 is smaller than the reference value, the on / off circuit 10 Causes the switching element Q2 to forcibly turn off and the non-operating state, and the on / off circuit 15 forcibly turns the switching element Q4 to the non-operating state while remaining off.
[0051]
As a result, only the switching element Q1 is operated on the DC / DC converter 3 side, and only the switching element Q3 is operated on the active filter 13 side. Thereby, each switching loss and drive loss due to the switching element Q2 of the DC / DC converter 3 and the switching element Q4 of the boost chopper type active filter 13 can be eliminated, and the efficiency of the DC power supply device can be improved. .
[0052]
[SecondEmbodiment]
Next, according to the inventionSecondThe embodiment will be described with reference to FIG.
The DC power supply device shown in FIG.FirstIn a DC power supply device having an active filter 13 similar to that of the embodiment, the current detecting means is the same as that shown in FIG. 3 and is inserted into a line 17 in order to inform the control circuit 14 of the active filter 13 of the input current value. The current detecting means is constituted by the resistor R4 and the current detecting circuit 11 for detecting a current value by a voltage generated between both terminals.
[0053]
In the DC power supply device shown in FIG. 6, the resistor R4 as current detecting means and the current detecting circuit 11 always detect the input current, and when the detected current value is smaller than the reference value, the comparing circuit 9 outputs the output current. The on / off circuits 10 and 15 are respectively controlled by signals to force the switching element Q2 into the non-operation state and also force the switching element Q4 into the non-operation state.Therefore, also in this embodiment, the comparison circuit 9 and the ON / OFF circuit 10 are in the first non-operating state. The comparison circuit 9 and the ON / OFF circuit 15 constitute second non-operation control means.
[0054]
Thereby,When the current value detected by the current detection circuit 11 is smaller than the reference value,In the DC / DC converter 3, only the switching element Q1 operates alone, and in the active filter 13, only the switching element Q3 operates alone. As a result, switching loss and drive loss of switching elements Q2 and Q4 can be eliminated, and the efficiency of the DC power supply can be improved.
[0055]
[ThirdEmbodiment]
Next, according to the inventionThirdThe embodiment will be described with reference to FIG.
thisThe DC power supply shown in FIG. 7 replaces the current detection circuit 11 and the comparison circuit 9 in the DC power supply shown in FIG.Reference exampleSimilarly to the above, an external signal input terminal 12 is provided, and external signals input therefrom are input to the on / off circuits 10 and 15, respectively.
[0056]
For example, a signal generated by pressing a switching stop button on an operation panel (not shown) of the DC power supply, or a signal of a circuit controlling an electronic device equipped with the DC power supply is supplied to the external input terminal 12. To the ON / OFF circuit 10 and the ON / OFF circuit 15, respectively. For input of such external signalsThereforeIn the DC / DC converter 3, the ON / OFF circuit 10 unconditionally sets the switching element Q2 to the non-operating state in which the switching element Q2 remains OFF, and the switching element Q1 alone operates. Also in the active filter 13, the on / off circuit 15 unconditionally sets the switching element Q4 to the non-operating state in which the switching element Q4 remains off, so that only the switching element Q3 operates alone.
[0057]
As a result, switching loss and drive loss due to the switching element Q2 of the DC / DC converter 3 and the switching element Q4 of the active filter 13 can be eliminated, and the efficiency of the DC power supply can be improved.
The method for stopping the operations of the switching elements Q2 and Q4 is to use a control IC as the on / off circuit 10 and to use the on / off function, to cut off the drive power supply for the control IC, or to use a drive signal for the switching element. It is possible to shut off any of the above methods.
[0058]
FIG.In each of the embodiments shown in FIG. 7 to FIG. 7, two switching elements of the DC / DC converter 3 and the boost chopper type active filter 13 are provided in parallel, but three or more switching elements may be provided in parallel. Also, the DC / DC converter has been described as a forward type and the active filter has been described as a boost chopper type.ButIn the flyback method and the half-bridge method, the same effect can be obtained regardless of the combination of the active filter and the step-down chopper method.
[0059]
The present invention can also be applied to a case where the DC / DC converter has multiple outputs. In this case, the output current of two or more outputs is detected, and the detection signal of each current detection circuit is ORed or added. The operating state / non-operating state of the switching element may be determined by inputting to a circuit and calculating the result.
[0060]
【The invention's effect】
According to the present invention, a rectifier circuit for full-wave rectifying an AC power supply is provided.,A DC / DC converter for obtaining one or more DC outputs;,ThatBetween rectifier circuit and DC / DC converterEstablishedActive filter for power factor improvementAnd byA switching element of a DC / DC converter in a configured DC power supply deviceAnd the switching element of the active filterProvided in parallel, when light load, that is, when the output power is small,DC / DC converter and
Active filter provided separatelyOf multiple switching elementsEachSince only one is active and the other switching elements are inactive,DC / DC converter and active filterThe switching loss and drive loss of the switching element can be reduced, and the efficiency of the DC power supply can be improved.
[0061]
[Brief description of the drawings]
FIG. 1 is the present invention.Shows the first reference example that is the basis ofIt is a circuit diagram of a DC power supply device.
FIG. 2 shows a specific example of a current detection circuit 8, a comparison circuit 9, and an on / off circuit 10 in FIG.
It is a circuit diagram.
FIG. 3 is a schematic diagram of the present invention;Shows a second reference example that is the basis ofIt is a circuit diagram of a DC power supply device.
FIG. 4 is the present invention.Shows a third reference example that is the basis ofIt is a circuit diagram of a DC power supply device.
FIG. 5 according to the inventionFirstIt is a circuit diagram of the DC power supply device of the embodiment.
FIG. 6 according to the inventionSecondIt is a circuit diagram of the DC power supply device of the embodiment.
FIG. 7 according to the inventionThirdIt is a circuit diagram of the DC power supply device of the embodiment.
FIG. 8 is a circuit diagram showing an example of a conventional DC power supply device.
FIG. 9 is a circuit diagram showing an example of a DC power supply device provided with a conventional active filter.
[Explanation of symbols]
1: AC power supply 2: Rectifying smoothing circuit
3: DC / DC converter
4: DC / DC converter control circuit
5: Voltage detection circuit
6, 7: DC / DC converter output terminal
8: Current detection circuit 9: Comparison circuit
10, 15: ON / OFF circuit
12: External signal input terminal
13: Active filter
14: Active filter control circuit
20: Diode bridge (full-wave rectifier circuit)
Q1-Q4: Switching element
T1: Transformer

Claims (2)

A rectifier circuit for full-wave rectification of an alternating current input from an AC power supply, and a secondary winding of the transformer by turning on / off a switching element connected in series with a primary winding of the transformer to which an output of the rectifier circuit is input. DC / DC converter for rectifying and smoothing the voltage induced in the DC / DC converter and outputting the rectified and smoothed voltage,
A plurality of switching elements of the DC / DC converter are provided in parallel,
Current detection means for detecting an output current of the DC / DC converter or a current proportional to the current;
When the current value detected by said current detecting means is less than a preset value, the first non-operation of the non-operating state remains off the other switching elements but one of the plurality of switching elements Control means ,
Further, an active filter is provided between the rectifier circuit and the DC / DC converter to improve a power factor by turning on / off a switching element, and a plurality of switching elements of the active filter are provided in parallel.
When the current value detected by the current detecting means is smaller than a preset value, a second operation is performed in which the other switching elements of the active filter are turned off except for one of the plurality of switching elements and remain in the inactive state. A direct current power supply device comprising the non-operation control means . A rectifier circuit for full-wave rectification of an alternating current input from an AC power supply, and a secondary winding of the transformer by turning on / off a switching element connected in series with a primary winding of the transformer to which an output of the rectifier circuit is input. DC / DC converter for rectifying and smoothing the voltage induced in the DC / DC converter and outputting the rectified and smoothed voltage,
A plurality of switching elements of the DC / DC converter are provided in parallel,
An external signal input terminal, and first non-operation control means for setting the other switching elements to an inactive state in which one of the plurality of switching elements is kept off by an external signal input from the input terminal; And
Further, an active filter is provided between the rectifier circuit and the DC / DC converter to improve a power factor by turning on / off a switching element, and a plurality of switching elements of the active filter are provided in parallel.
A second non-operation control means for setting other switching elements except one of the plurality of switching elements of the active filter to an inactive state in which the switching elements are kept off by an external signal input from the external signal input terminal; A DC power supply device characterized by the above-mentioned.

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