JPH0870573A - Power supply - Google Patents

Abstract

PURPOSE: To enable stabilized output voltage to be obtained, to a wide range of input voltage, and also, improve power factor. CONSTITUTION: A first energy transmission path transmits the energy accumulated in a transformer during the ON period of a first switching element 4 to output side through the output winding 32 of the transformer 3 in the next period. A second energy transmission path transmits energy to output side from input side through the output winding 32 when a second switching element 5 is on, having a second switching element 5 and the output winding 32 inserted and connected within the circuit loop making a round of an input end 11, an output end 21, load, an output end 22, and an input end 12. A control circuit 9 controls the ON time of the first switching element 4 and the second switching element 5 and the timing of ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device. The power supply device according to the present invention is used as a power supply input circuit connected to the preceding stage of the switching power supply or used as the switching power supply itself.

[0002]

2. Description of the Related Art As a power supply device of this type,
The boost type and the buck-boost type are well known. The step-up power supply device includes a rectifier circuit and a smoothing capacitor, a choke coil is connected between the rectifier circuit and the smoothing capacitor, and a switching element is connected between the choke coil and a power supply line at a subsequent stage to perform switching. It is often the one that has a basic circuit configuration in which a diode is connected in series to the power supply line at the stage subsequent to the element, an output capacitor is connected between the power lines at the subsequent stages of this diode, and both ends of the output capacitor are led to the output end Are known. In this circuit configuration, the energy supplied from the power supply and the energy stored in the choke coil during the ON period of the switching element are used to charge the output capacitor in one direction through the diode and boost the voltage across the output capacitor. Generate a voltage.

A typical example of a step-up / down type power supply device is that a switching element is connected in series to the input winding of a conversion transformer and the energy accumulated in the conversion transformer during the ON period of the switching element is loaded during the next OFF period. It is a flyback converter system that transmits to the side.

As another example of the step-up / down type power supply device, the one disclosed in JP-A-2-307365 is also known. The power supply device disclosed in Japanese Patent Laid-Open No. 2-307365 includes a full-wave rectifier circuit, a capacitor is connected between the rectified output terminals of the rectifier circuit, and another switching element is provided between the rectifier circuit and the inductor. Provided,
Both switching elements are turned on and off almost at the same time to obtain a stepped up or stepped down output voltage.

However, the above conventional power supply device has the following problems. First, in the boost type power supply device, the switching element is connected only between the power supply lines,
It does not have a switching element connected in series to the power supply line. Therefore, when the switching element stops the switching operation and is in the off state, the input voltage is output as it is. In addition, if the output terminal is short-circuited or overloaded, overcurrent protection may not be possible, or inrush current may flow through the smoothing capacitor, causing a momentary drop in the power supply voltage or electrical breakdown of the rectifier circuit. , In addition,
Since the output voltage is always higher than the input voltage, a problem such as requiring a DC-DC converter with a high allowable input voltage in the subsequent stage occurs.

Next, in the step-up / down power supply device, since the input end and the output end are insulated by the conversion transformer, unlike the step-up power supply device, there is no switching element connected in series to the power supply line. There is no problem caused by it.
However, all the energy has to be transmitted via the conversion transformer. Therefore, the energy conversion efficiency is lowered and the circuit itself is increased in size.

In the power supply device disclosed in Japanese Patent Laid-Open No. 2-307365, it is difficult to control the two switching elements because they must be controlled to be turned on and off in a complicated manner. Further, since the two switching elements and the two diodes are connected in series with the choke coil, power loss increases when energy is stored in the choke coil and when stored energy is released from the choke coil. For this reason,
Efficiency is reduced.

[0008]

An object of the present invention is to provide a power supply device capable of improving the power factor.

Another object of the present invention is to provide a power supply device capable of suppressing an inrush current without lowering efficiency.

Another object of the present invention is to provide a power supply device capable of obtaining a stable and constant output voltage for a wide range of input voltages.

Another object of the present invention is to provide a power supply device capable of protecting an overcurrent when an output is short-circuited.

Another object of the present invention is to provide a power supply device which reduces the load on the conversion transformer and has a high conversion efficiency.

Another object of the present invention is to provide a power supply device capable of improving efficiency by reducing circuit elements that are connected in series and by reducing loss.

Another object of the present invention is to provide a power supply device which does not require a dedicated choke coil and is suitable for reducing the number of parts, downsizing and cost reduction.

[0015]

In order to solve the above problems, a power supply device according to the present invention includes a first energy transmission circuit, a second energy transmission circuit, and a control circuit, and outputs from an input end. Transfer power to the end.

The first energy transfer circuit includes a transformer and a first switching element, the first switching element being connected in series to an input winding of the transformer, and the first switching element A circuit is configured to transfer the energy stored in the transformer during the on period to the output terminal through the output winding of the transformer during the next off period. This means that the power supply device according to the present invention includes the circuit operation as the flyback type buck-boost power supply device described above.

The second energy transfer circuit includes a second switching element and an output winding of the transformer. The second switching element and the output winding are
It is inserted and connected in a circuit loop that returns from one of the input ends to one of the output ends, the load and the other of the output ends to the other of the input ends, and through the output winding when the second switching element is turned A circuit for transmitting energy to the output end is configured. Therefore, the energy supplied from the power supply can be transmitted to the output end, and the energy stored in the transformer during the on period of the second switching element can be transmitted to the output end during the next off period. In this case, the output winding of the transformer is also used as the choke coil. Therefore, a dedicated choke coil is not required, and the number of parts can be reduced, downsizing and cost reduction can be achieved.

The control circuit controls the on-time and on-timing of the first switching element and the second switching element. With this control operation, appropriate control can be performed according to the purpose such as keeping the output voltage constant or improving the power factor. For example, when the output voltage is controlled to be constant, the output voltage is monitored, and the on-duty of the first switching element and the second switching element is controlled so that the output voltage becomes constant. This ensures that even if the input voltage is higher than the target output voltage,
A constant regulated output voltage can be obtained, whether low or equal. Therefore, the output voltage can be adjusted to a constant value for a wide range of input voltages.

Further, by controlling the on-time and on-timing of the first switching element and the second switching element, energy transfer from the input side to the output side can be continuously performed as long as the input voltage is present. be able to. Therefore, a continuous input voltage such as a full-wave rectified output can be supplied and an input current can be continuously supplied. This provides the basis for power factor improvement.

Moreover, when transmitting energy from the input end to the output end, it is not necessary to transmit all the energy through electromagnetic coupling between the input winding and the output winding of the transformer, so that the burden on the transformer is increased. Is reduced and the conversion efficiency is increased.

When the output terminal is short-circuited or overloaded, the first switching element and the second switching element
By reducing the on-duty of the switching element or turning it off, transmission energy can be reduced or cut off, and overcurrent protection at the time of output short circuit can be achieved.

Further, since the output current can be limited by lowering the on-duty of the first switching element and the second switching element, the inrush current to the smoothing capacitor can be suppressed without adding a new circuit. .

Further, since the first switching element and the second switching element are in parallel when viewed from the input end, even when the first switching element and the second switching element are turned on at the same time, the energy is not transmitted. The current is shunted, and the power loss due to the switching element can be reduced.

As a concrete circuit suitable for improving the power factor, the control circuit uses the detection signal of the output voltage appearing between the output terminals and the detection signal of the current flowing through the first switching element as input signals, and outputs the output voltage detection signal. The phase is shifted by about 90 degrees, the signal after the phase shift is used as a command value, the signal after the phase shift and the current detection signal are compared, and the first based on the comparison output signal.
Control the switching element of.

[0025]

FIG. 1 is a circuit diagram of a power supply device according to the present invention. The power supply device according to the present invention includes input terminals 11 and 12, output terminals 21 and 22, a transformer 3, a first switching element 4, a second switching element 5, a first diode 6, and a first diode 6. It includes a diode 7 of 2, a capacitor 8 and a control circuit 9. A rectified voltage or a DC voltage is supplied to the input ends 11 and 12. A load is connected to the output terminals 21 and 22.

The first energy transmission circuit is the transformer 3
, The first switching element 4, and the first diode 6
And a capacitor 8 are included. The transformer 3 has an input winding 31 and an output winding 32.
The black circle indicates the beginning of winding. The first switching element 4 is a FET, a bipolar transistor, a thyristor,
It is composed of a three-terminal element such as a triac or IGBT, or other semiconductor element with a control pole, its main electrode circuit is connected in series to the input winding 31, and the circuit connected in series is connected to the input terminals 11 and 12, Switches the current flowing in the series circuit. The first diode 6 is connected to the output winding 3
2 is connected in series, and the series circuit is connected to the output terminals 21 and 22. The polarity of the first diode 6 is oriented in a forward direction with respect to the voltage (flyback voltage) generated in the output winding 32 when the first switching element 4 is off. A flyback voltage V2 having the illustrated polarity is generated in the output winding 32 when the first switching element 4 is off. The first diode 6 is in the forward direction with respect to the flyback voltage V2.

The second energy transfer circuit includes a second diode 7, an output winding 32 of the transformer 3, a second switching element 5, and a capacitor 8. One end of the second diode 7 is connected to one end of the first diode 6 in the same polar relationship. The second switching element 5 is a three-terminal element such as FET,
The main electrode circuit constitutes a series circuit together with the output winding 32, the second diode 7 and the capacitor 8 when viewed from the input ends 11 and 12. In the embodiment, the anode of the second diode 7 is connected to the input end 11, and the cathode is connected to the output winding 32 and the cathode of the first diode 6. The anode of the first diode 6 is connected to the output end 22. Second switching element 5
Are connected between the input end 12 and the output end 22.
The capacitor 8 is connected in parallel to the output terminals 21 and 22.

The first diode 6, the capacitor 8 and the output winding 32 constitute an energy emission circuit, and the energy stored in the transformer 3 through the energy transmission process of the first energy transmission circuit and the second energy transmission circuit. To release.

The control circuit 9 includes the first switching element 4
Also, the ON time and the ON timing of the second switching element 5 are controlled. This makes it possible to stabilize the output voltage and improve the power factor. For example, when the output voltage Vo is kept constant, the output voltage Vo of the output terminals 21 and 22 is set as the input condition Si, and the first control having the ON time width according to the deviation between the output voltage Vo and the target output voltage Vr. The signal S1 is supplied to the first switching element 4. The control circuit 9 supplies the second control signal S2 to the second switching element 5 so that the second switching element 5 may be turned on when the first control signal S1 is off.
The second switching element 5 may be turned on when the first switching element 4 is turned on, or may be turned on when the first switching element 4 is turned off. In short, the 1st switching element 4 and the 2nd switching element 5 should just perform the ON / OFF operation suitable for a control mode.

By controlling the on-time and on-timing of the first switching element 4 and the second switching element 5, energy transfer from the input side to the output side can be continuously performed as long as the input voltage is present. be able to. Therefore, a continuous input voltage such as a full-wave rectified output can be supplied and an input current can be continuously supplied. This provides the basis for power factor improvement.

Next, a specific operation example of the power supply device according to the present invention will be described with reference to the time chart of FIG. In the figure, when the input voltage Vi is lower than the output voltage Vo, when the input voltage Vi is equal to the target output voltage Vo, the input voltage Vi
Is higher than the target output voltage Vo. Reference numeral I1 is the first switching element 4
, Reference voltage V1 indicates a terminal voltage of the first switching element 4, reference numeral I2 indicates a current flowing through the second switching element 5, and reference numeral I4 indicates a current flowing through the first diode 6. The operation of the power supply device according to the present invention shown in FIG. 1 will be described with reference to FIG. Input end 1
The input voltage Vi supplied to the terminals 1 and 12 and the output terminals 21 and 2
The relationship between the target output voltage Vo to be obtained in 2 is Vi <
Each case of Vo, Vi> Vo, and Vi = Vo will be individually described.

A. When Vi <Vo The operation of the first energy transfer circuit is performed as follows. First, at time t1, the first switching element 4 is turned on and the current I1 flows. Energy corresponding to the current I1 is accumulated in the transformer 3. At this time, a voltage having a positive polarity on the black circle side is generated in the output winding 32. Since the first diode 6 has a direction opposite to the voltage generated in the output winding 32, the current I4 does not flow. Second
Since the diode 7 is also in the opposite direction to the voltage generated in the output winding 32, the output terminals 21 and 22 to the input terminal 11,
Prevent backflow to 12.

Next, at time t2, the first switching element 4 is turned off and the second switching element 5 is turned on. When the first switching element 4 is turned off, the first
Based on the energy accumulated when the switching element 4 is turned on, a flyback voltage V2 having a negative polarity on the black circle side is generated in the output winding 32.

The operation of the second energy transmission circuit will be described. At time t2, when the first switching element 4 is turned off and the second switching element 5 is turned on, the input terminal 11 → the second diode 7 → the output winding 32 → the output terminal 2
A circuit loop is formed by 1 → load → output end 22 → second switching element 5 → input end 12, and a current I2 flows. As a result, the capacitor 8 is charged to a voltage obtained by adding the input voltage Vi and the flyback voltage V2, and the corresponding output voltage Vo appears at the output terminals 21 and 22. The output voltage Vo is Vo = Vi + n · Vi · D / (1−D), where n is the turn ratio of the transformer 3 and D is the on-duty of the first switching element 4. As is clear from the above equation, a constant output voltage can be obtained by controlling the on-duty ratio D of the first switching element 4. Since the sum of the input voltage and the flyback voltage is the output voltage,
It is not necessary to perform all the energy transfer from the input side to the output side through the electromagnetic coupling of the input winding 31 and the output winding 32 of the transformer 3, the burden on the transformer is reduced, and the conversion efficiency is increased. In addition, the transformer can be downsized.

Further, in this case, the first switching element 4 has a long ON period and when the second switching element 5 is ON, it enters the next cycle and is turned ON. Therefore, the current I4 does not flow.

B. When Vi> Vo Since the operation of the first energy transfer circuit is similar to that described above, the circuit operation of the second energy transfer circuit will be mainly described. When the first switching element 4 is turned off at t2 and the second switching element 5 is turned on,
Input terminal 11 → second diode 7 → output winding 32 → output terminal 21 → load → output terminal 22 → second switching element 5
→ A circuit loop is formed by the input terminal 12, and the current I2 flows. The transformer 3 stores energy accumulated when the first switching element 4 is turned on and energy corresponding to the difference between the input voltage Vi and the output voltage Vo when the second switching element 5 is turned on.

At time t3, when the second switching element 5 is turned off, the energy stored in the transformer 3 is released to the load side via the first diode 6 and the output terminals 21 and 22, and the current I4 becomes the first value. It flows through the diode 6 of 1.

The output voltage Vo obtained in this case is Vo = Vi, where n is the turn ratio of the transformer 3, D is the on-duty of the first switching element 4, and d is the on-duty of the second switching element 5. (ND + d) / (1−D).

Therefore, a constant output voltage can be obtained by controlling the on-duty ratios of the first switching element 4 and the second switching element 5. Also in this case, when the energy is transmitted from the input end to the output end, it is not necessary to transmit all the energy through the electromagnetic coupling between the input winding 31 and the output winding 32 of the transformer 3, so that the transformer is not required. The burden of 3 is reduced,
Higher conversion efficiency.

C. When Vi = Vo The operation of the first energy transfer circuit is as described above. When the first switching element 4 is turned off at t2, the flyback voltage V2 is generated by the energy stored while the first switching element 4 is on. In this state, when the second switching element 5 is turned on at t2, the input terminal 11 → the second diode 7 → the output winding 3
A circuit loop is formed by 2 → output end 21 → load → output end 22 → second switching element 5 → input end 12, and a current I2 flows. The current I2 becomes a load current. The capacitor 8 is charged with the input voltage Vin.

At time t3, when the second switching element 5 is turned off, the energy stored in the transformer 3 is released through the first diode 6 and the current I4
Flows through the first diode 6.

The output voltage Vo obtained in this case is Vo = n, where n is the turn ratio of the transformer 3, D is the on-duty of the first switching element 4, and d is the on-duty of the second switching element 5.・ Vi ・ D / (1-Dd).

As can be understood from the above description, whether the input voltage Vi is lower than the output voltage Vo or the input voltage Vi is higher than the output voltage Vo, the first
A constant output voltage can be obtained by controlling the on-duty ratios of the switching element 4 and the second switching element 5. Therefore, it is possible to obtain the power supply device capable of adjusting the output voltage Vo to a constant voltage with respect to the input voltage Vi in a wide range.

In addition, in the entire voltage range of the input voltage Vi, currents (I1, I2) as input currents flow. Therefore, when the input voltage Vi is given as a continuous wave such as a full-wave rectified output, the input current continuously flows, which can provide a basis for power factor improvement.

When the output terminals 21 and 22 are overloaded or short-circuited, the on-duty of the first switching element 4 and the second switching element 5 is reduced or turned off. It is possible to reduce or cut off the transmission energy and to protect against overcurrent when the output is short-circuited.

Furthermore, the first switching element 4 and the second switching element 4
Since the switching elements 5 are parallel when viewed from the input ends 11 and 12, even when the first switching element 4 and the second switching element 5 are turned on at the same time, the current for energy transmission is shunted and the switching elements The power loss due to can be reduced.

When the transformer 3 releases the stored energy, it is performed through the first diode 6 or the second diode 7, but since the same current does not flow through the two diodes, the power loss by the diode is lost. Can be reduced.

Further, the control circuit 9 has a first ON time width corresponding to the deviation between the output voltage Vo and the target output voltage Vr.
Since the control signal S1 of 1 is supplied to the first switching element 4, the output voltage Vo can be made constant without monitoring both the input voltage Vi and the output voltage Vo.

Further, since the control circuit 9 turns on the second switching element 5 when the first switching element 4 is turned off and turns it off after a certain period of time, the output voltage Vo is kept constant by a simple control. can do.

FIGS. 3 to 6 are circuit diagrams showing another embodiment of the power supply device according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components.

In the embodiment of FIG. 3, the second switching element 5 is connected between the input end 11 and the anode of the second diode 7. The second switching element 5 is connected to the input ends 11 and 12 via the second diode 7, the output winding 32 of the transformer 3, and the output ends 21 and 22. Others are the same as the embodiment of FIG.

In the embodiment of FIG. 4, the first switching element 4 is connected between the input end 11 and the input winding 31. Others are the same as the embodiment of FIG.

The embodiment of FIG. 5 shows a case where the polarities of the output windings 32 of the transformer 3 are reversed. Output winding 3
2 is a terminal that generates a positive voltage (terminal on the black circle side)
Is connected to the output end 22, and the other end is connected to the second switching element 5. The first diode 6 has an anode connected to the second switching element 5 and a cathode connected to the output end 21. The second diode 7 is
The anode is connected to the input end 11, and the cathode is the output end 2
Connected to 1. The positive terminal of the output winding 32 is connected to the cathode of the first diode 6 via the output end 22, the load, and the output end 21, and the other end is connected to the anode of the first diode 6. . Transformer 3 and first
The polarity of the diode 6 is the same as that of the embodiment of FIG. A circuit loop is formed by the input terminal 11 → the second diode 7 → the output terminal 21 → the load → the output terminal 22 → the output winding 32 → the second switching element 5 → the input terminal 12.

The embodiment shown in FIG. 6 is different from the embodiment shown in FIG.
The second switching element 5 and the second diode 7 are replaced with each other. The first diode 6 and the second diode 7 have the same effects as the embodiment shown in FIG. 1 in any embodiment in which the anodes are commonly connected.

FIG. 7 is a circuit diagram showing another embodiment of the power supply device according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. As shown
In this embodiment, a full-wave rectifier circuit 111 is included. The full-wave rectifier circuit 111 full-wave rectifies the AC input Ei and supplies the full-wave rectified output to the input terminals 11 and 12. Therefore, a continuous input voltage is applied to the input terminals 11 and 12, and
As described above, the first switching element 4 included in the energy transfer circuit and the second switching element 5 included in the second energy transfer circuit are controlled so that the input current flows in the entire range of the input voltage. , Can give the basis for power factor improvement. The capacitor 112 is a noise filter that absorbs the switching noise generated by the switching operation of the first switching element 4 and the second switching element 5. Note that it is not a smoothing capacitor.

Next, a specific example of the control circuit 9 suitable for improving the power factor will be described with reference to FIG. The control circuit 9 includes a detection signal Vd of the output voltage Vo appearing between the output terminals 21 and 22.
And the detection signal Id of the current I1 flowing through the first switching element 4 is input. In the control circuit 9, the difference between the detection signal Vd of the output voltage Vo and the reference voltage is amplified, and the phase is shifted by about 90 degrees. The signal Vod after the phase shift is compared with the detection signal Id of the current I1, and the first switching element 4 is controlled based on the comparison output signal.

In the embodiment, the output voltage Vo is the resistance R
The voltage is divided by 1 and R2, and the divided voltage is supplied to the input terminal (−) of the error amplifier 911 as the detection signal Vd through the resistor R3. A reference voltage is applied from the reference power supply 912 to the input terminal (+) of the error amplifier 911. The error amplifier 911 has a capacitor Co between the input / output terminal (−) and the output terminal. The error amplifier 911 operates as an integrator having a time constant Co · R3 defined by the capacitor Co and the resistor R3 as an integration time constant, shifts the phase of the detection signal Vd by about 90 degrees, and amplifies the output Vod. Is obtained. The output Vod is supplied to the input terminal (−) of the comparator 913 provided in the next stage.

The current I flowing through the first switching element 4
1 is detected by the current detection means 914. As the current detecting means 914, various kinds of conventionally known sensors can be used. It is typically a current transformer. The detection signal Id obtained by the current detecting means 914 is supplied to the comparator 91.
3 is supplied to the input terminal (+). Therefore, the comparator 91
3 compares the signal Vod with the detection signal Id of the current I1, and based on the comparison output, the first switching element 4
Control. Comparator 913 and first switching element 4
A flip-flop 915 is inserted between and, and a control signal S1 for turning on / off the first switching element 4 is supplied to the first switching element 4 depending on the presence / absence of a comparison output. After the first switching element 4 is turned off, the control signal S2 is supplied to the second switching element 5, so that the second switching element 5 is turned on for a certain period of time.

Next, the operation of the power supply device having the control circuit 9 shown in FIG. 8 will be described with reference to the waveform chart shown in FIG. FIG. 9A shows the waveform of the full-wave rectified voltage V11 output from the full-wave rectified diode 111. The full-wave rectified voltage V11 receives the switching action of the first switching element 4 and the second switching element 5, and is taken out to the output terminals 21 and 22. FIG. 9B is a waveform of the output voltage Vo seen at the terminal of the output capacitor 8. The output voltage Vo is the full-wave rectified voltage V1 shown in FIG.
It has a phase difference of about 90 degrees with respect to 1.

The output voltage Vo is divided by the resistors R1 and R2, and the divided voltage is supplied to the input terminal (-) of the error amplifier 911 as the detection signal Vd. The error amplifier 911 includes the capacitor Co and the resistor R3 as described above.
It operates as an integrator having a time constant Co · R3 determined by and as an integration time constant. As a result, as shown in FIG. 9C, the error amplifier 91 amplifies the difference between the detection signal Vd and the reference voltage, and further shifts the phase by about 90 degrees to output Vo.
d is obtained. The output Vod is the comparator 9 provided in the next stage.
It is supplied to 13 input terminals (-).

On the other hand, the switching operation of the first switching element 4 causes a current I1 as shown in FIG. 9D to flow in the circuit loop including the first switching element 4 and the winding 31 of the transformer 3. The current I1 flowing through the first switching element 4 is detected by the current detection means 914. The detection signal Id obtained by the current detection means 914 is supplied to the input terminal (+) of the comparator 913. The comparator 913 compares the signal Vod with the detection signal Id of the current I1, and controls the first switching element 4 based on the comparison output signal. In the case of the embodiment, the comparator 9
The output Vcp of 13 has a logical value of 0 in the range where the current detection signal Id is smaller than the error amplification signal Vod, and has a logic value of 1 when the current detection signal Id becomes substantially equal to the error amplification signal Vod.

Comparator 913 and first switching element 4
The flip-flop 915 provided between and is reset when the comparison output Vcp becomes the logical value 1 to generate the reset output having the logical value 0. Flip flop 915
Further, when the set signal input from the oscillator 916 becomes the logical value 1 after the comparison output Vcp becomes the logical value 0, the set signal having the logical value 1 is generated. The reset signal of logic 0 and the set signal of logic 1 of the flip-flop 915 are supplied to the first switching element 4 as the control signal S1.

The first switching element 4 has a control signal S
1 turns on when the logical value becomes 1 and the control signal S1 becomes logical value 0
Will turn off.

At the timing when the flip-flop 915 outputs the control signal S2 having a logical value of 0, and as a result, the first switching element 4 is turned off, the detection signal Id detected by the current detection means 914 is the error amplifier 911. Becomes almost equal to the signal Vod output from the comparator 913.
This is the timing when the output Vcp of becomes the logical value 1. Therefore, the first switching element 4 has the error amplifier 911.
The signal Vod output from the device is used as a command value, and the first switching element 4 is turned off and the current I1 is cut off at the timing when the current I1 flowing through the first switching element 4 becomes substantially equal to this command value.

The detection signal Id detected by the current detecting means 914 is the signal V output from the error amplifier 911.
When the set signal supplied from the oscillator 916 has a logical value of 1 in a state lower than od, the flip-flop 9
15 outputs the control signal S1 having the logical value 1 again, and the first switching element 4 is turned on.

Here, the signal Vod serving as the command value is shown in FIG.
As shown in (c), it is in phase with the full-wave rectified voltage V11 shown in FIG. 9 (a). The first switching element 4 is controlled so that the signal Vod is used as a command value and a current I1 according to the command value is supplied. As a result, the current I
1 flows in the same phase as the signal Vod as shown in FIGS. 9 (d) and 9 (e).

The current I flowing through the output side of the full-wave rectifier circuit 111 is the current Iav flowing through the first switching element 4.
(Fig. 9 (e)) and the current I2 (Fig. 9 (f)) flowing through the second switching element 5 are summed. The current I2 flowing through the second switching element 5 is as shown in FIG. 9 (f) because the second switching element 5 operates with a constant ON width. Therefore, the current I flowing to the output side of the full-wave rectification circuit 111 is the same as the current Iav in FIG.
FIG. 9 obtained by adding the current I2 shown in FIG.
The waveform is as shown in (g).

Therefore, the current Iac flowing on the AC input side of the full-wave rectifier circuit 111 has a continuous sine wave shape as shown in FIG. 9 (h). Therefore, the power factor is significantly improved.

Although FIG. 8 shows an embodiment based on the power supply device shown in FIG. 3, the teaching of FIG. 8 is shown in FIGS. 1, 3, 4, 5, 6 and 7. It can also be applied to power supplies.

FIG. 10 is an electric circuit diagram showing still another embodiment of the power supply device according to the present invention. In this embodiment, the control circuit 9 changes the ON time width of the second switching element 5 according to the level of the input voltage Vi. As the means, in the embodiment of FIG. 10, the control circuit 9
Includes a first control circuit 91 that controls the first switching element 4 and a second control circuit 92 that controls the second switching element 5, and the second control circuit 92
The ON time width of the second switching element 5 is changed according to the level of the input voltage Vi. The first control circuit 91 can have the circuit configuration shown in FIG.

The ON time of the second switching element 5 is set to T
If it is on and the switching cycle is T, then Vi · Ton / T = Vo.

In a region where the input voltage Vi is lower than the output voltage Vo, the ON time Ton of the second switching element 5 is lengthened and the period of operation as the boost converter is lengthened to improve the efficiency. But,
As is clear from the above equation, the second switching element 5
When the ON time Ton of is long, the output voltage Vo becomes too high, which makes it difficult to stabilize the output.

As is clear from the above equation, the output voltage Vo is determined by (Vi.Ton / T). Therefore, when the input voltage Vi is low, the ON time Ton of the second switching element 5 is lengthened and boosted. Efficiency is improved by prolonging the period of operation as a converter. FIG. 11 shows a waveform diagram when the input voltage Vi is low. Figure 11
(A) is a switching waveform of the first switching element 4, and (b) is a switching waveform of the second switching element 5. FIG. 11C shows the first switching element 4
Of the voltage waveform appearing between the terminals of the first switching element 4 at the time of turning on and off, FIG.
The waveform of the current I1 flowing in the second switching element 5 is shown in (e).

When the input voltage Vo is high, the ON time Ton of the second switching element 5 is shortened and the output voltage V
Control so that o does not become excessive. FIG. 12 shows a waveform diagram when the input voltage Vi is high. FIG. 12A is a switching waveform of the first switching element 4, FIG.
Is a switching waveform of the second switching element 5. FIG. 12C is a voltage waveform appearing between the terminals of the first switching element 4 when the first switching element 4 is turned on and off, FIG. 12D is a waveform of the current I1 flowing through the first switching element 4, and FIG. ) Is the waveform of the current I2 flowing through the second switching element 5.

As is apparent from the comparison between FIG. 11B and FIG. 12B, when the input voltage Vi becomes low, the ON time Ton of the second switching element 5 is lengthened.
When the input voltage Vi becomes high, the ON time Ton of the second switching element 5 is shortened. First control circuit 9
1 has the input voltage Vi as an input signal, and the input voltage Vi
The on time Ton can be controlled based on n.

Since the input voltage Vi and the output voltage Vo satisfy the relationship of Vi · Ton / T = Vo as described above, the control circuit 9 determines whether the output voltage Vo is high or low.
The ON time width Ton of the switching element 5 may be controlled.

FIG. 10 shows an embodiment based on the power supply device shown in FIG. 1. The teaching of FIG. 10 is shown in FIGS.
The power supply device shown in FIGS. 5, 6 and 7 can also be applied.

FIG. 13 is an electric circuit diagram showing still another embodiment of the power supply device according to the present invention. In this embodiment, the control circuit 9 inhibits the operation of the second switching element 5 until the output voltage Vo reaches a constant value. While the power supply device is not operating, the accumulated charge of the output capacitor 8 is almost zero. Therefore, if the second switching element 5 is turned on at the same time when the power supply device is activated, a high voltage is applied to the transformer 3. This means that a large transformer is needed. In the case of the embodiment shown in FIG. 13, the control circuit 9 prohibits the operation of the second switching element 5 until the output voltage Vo reaches a constant value.
By the time the second switching element 5 is turned on,
A considerable amount of charge is stored in the output capacitor 8. Therefore, the voltage applied to the transformer 3 at the time of startup can be lowered.

In the present embodiment, the control circuit 9 includes a first control circuit 91 for controlling the first switching element 4,
Second control circuit 9 for controlling the second switching element 5
2 and the second control circuit 92 outputs the output voltage V
The operation of the second switching element 5 is prohibited until o reaches a constant value. The second control circuit 92 includes a comparator 922.
Thus, the voltage signal Si of the output voltage Vo is compared with the reference voltage of the reference voltage source 923, and when the voltage signal Si becomes higher than the reference voltage, the AND gate 924 outputs the control signal S2. Until the control signal S2 is output,
The operation of the second switching element 5 is prohibited. The first control circuit 91 can have the circuit configuration shown in FIG. 13 shows an embodiment based on the power supply device shown in FIG. 1, the teaching of FIG. 13 is shown in FIGS.
The power supply device shown in FIGS. 5, 6 and 7 can also be applied.

FIG. 14 is an electric circuit diagram showing still another embodiment of the power supply device according to the present invention. The control circuit 9 uses the induced voltage generated in the third winding 33 wound around the transformer 3 as an auxiliary power supply. With this configuration, the power supply device can be downsized. The auxiliary power supply circuit preferably includes a full-wave rectification circuit 34, and the full-wave rectification output is smoothed by a capacitor 35. According to this auxiliary power supply circuit, a stabilized auxiliary power supply voltage can be obtained. Although not shown,
The control circuit 9 can have the circuits shown in FIGS. 8, 10 and 13. Although FIG. 14 shows an embodiment based on the power supply device shown in FIG. 1, the teaching of FIG. 14 applies to the power supply devices shown in FIGS. 3, 4, 5, 6, and 7. Applicable.

By the way, in the power supply apparatus shown in FIGS. 1, 3 to 8, 10, 13, and 14, a high voltage is applied to the first switching element 4 immediately before the first switching element 4 is turned on. V1 is applied. Therefore, the switching loss when the first switching element 4 is turned on becomes large, and the efficiency is reduced. In addition, a large charge is accumulated in the junction capacitance of the first switching element 4,
Due to this accumulated charge, the turn-on speed of the first switching element 4 becomes slow. To solve this problem,
The control circuit 9 turns on the second switching element in two periods after the first switching element 4 is turned on and immediately before it is turned on.

FIG. 15 shows the first switching element 4 and the second switching element 4.
FIG. 6 is a diagram showing an operation timing with the switching element of FIG. FIG. 15A is a switching waveform of the first switching element 4, and FIG. 15B is a second switching element 5.
15C shows the waveform of the voltage V1 applied to the first switching element 4, and FIG. 15D shows the waveform of the current I1 flowing through the first switching element 4.

The second switching element 5 is shown in FIG.
As is clear from the comparison between (a) and (b), the first switching element 4 is turned on during the two periods Ton1 and Ton2 immediately after the first switching element 4 is turned on and immediately before the first switching element 4 is turned on. When the second switching element 5 is turned on in the period Ton2 immediately before the first switching element 4 is turned on, the voltage V1 applied to the first switching element 4 becomes
As shown in FIG. 5 (c), it decreases by ΔV1. Voltage V1
Is due to the leakage inductance of the transformer 3,
Actually, it decreases along the dotted line P1 in FIG.
Thereby, the switching loss of the first switching element 4 can be reduced and the efficiency can be improved. An object is to provide a power supply device that can improve the power factor.

[0084]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a power supply device that can suppress an inrush current without causing a reduction in efficiency. (B) It is possible to provide a power supply device that can obtain a stabilized and constant output voltage for a wide range of input voltages. (C) It is possible to provide a power supply device that can achieve overcurrent protection when the output is short-circuited. (D) It is possible to reduce the load on the conversion transformer and provide a power supply device with high conversion efficiency. (E) It is possible to provide a power supply device capable of improving efficiency by reducing circuit elements that are connected in series and reducing loss. (F) It is possible to provide a power supply device that does not require a dedicated choke coil and is suitable for reducing the number of parts, downsizing, and cost reduction.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to the present invention.

FIG. 2 is a time chart explaining the operation of the power supply device according to the present invention.

FIG. 3 is a circuit diagram showing another embodiment of the power supply device according to the present invention.

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

FIG. 5 is a circuit diagram showing another embodiment of the power supply device according to the present invention.

FIG. 6 is a circuit diagram showing another embodiment of the power supply device according to the present invention.

FIG. 7 is a circuit diagram showing another embodiment of the power supply device according to the present invention.

FIG. 8 is a circuit diagram showing still another embodiment of the power supply device according to the present invention.

9 is a voltage and current waveform diagram of each part of the power supply device shown in FIG.

FIG. 10 is a circuit diagram showing still another embodiment of the power supply device according to the present invention.

11 is a waveform diagram illustrating one of control methods in the power supply device shown in FIG.

12 is a waveform diagram illustrating another control method in the power supply device shown in FIG.

FIG. 13 is a circuit diagram showing still another embodiment of the power supply device according to the present invention.

FIG. 14 is a circuit diagram showing still another embodiment of the power supply device according to the present invention.

FIG. 15 is a waveform diagram illustrating still another control method in the power supply device according to the present invention.

[Explanation of reference symbols]

 11, 12 Input end 21, 22 Output end 3 Transformer 31 Input winding 32 Output winding 4 First switching element 5 Second switching element 6 First diode 7 Second diode 8 Capacitor 9 Control circuit Vi input voltage Vo output voltage S1 first control signal S2 second control signal

Claims (13)

[Claims] 1. A power supply device including a first energy transmission circuit, a second energy transmission circuit, and a control circuit, for transmitting electric power from an input end to an output end, the first energy transmission circuit Includes a transformer and a first switching element, the first switching element being connected in series with an input winding of the transformer,
The first energy transfer circuit constitutes a circuit that transfers the energy stored in the transformer during the ON period of the first switching element to the output end through the output winding of the transformer during the next OFF period. The second energy transfer circuit includes a second switching element and an output winding of the transformer, and the second switching element and the output winding are connected from one input terminal to an output terminal. On the other hand, a circuit that is inserted and connected in a circuit loop that passes through the other of the load and the output end and returns to the other of the input end, and transfers energy from the input end to the output end through the output winding when the second switching element is turned on. The control circuit controls the on-time and the on-timing of the first switching element and the second switching element. 2. The power supply device according to claim 1, wherein the first energy transfer circuit includes a first diode and a capacitor, and the first diode is the first diode. Is connected in series with the output winding and has a directivity with respect to the voltage generated in the output winding when the switching element is turned off, and the series circuit is led to the output end of the pair. And the capacitor is connected between the output terminals. 3. The power supply device according to claim 2, wherein the second energy transfer circuit includes a second diode, and the second diode is inserted and connected in the circuit loop. One end of the second diode is connected to the one end of the first diode in the same polar relationship. 4. The power supply device according to claim 2, wherein the first diode and the output winding configure an energy emission circuit, and the first energy transfer circuit and the second energy are included. The energy stored in the transformer is released through the energy transmission process of the transmission circuit. 5. The power supply device according to claim 1, wherein the control circuit controls such that the second switching element has an ON period when the first switching element is OFF. To do. 6. The power supply device according to claim 5, wherein the control circuit turns on the second switching element when the first switching element turns off, and turns off after a lapse of a predetermined time. Let 7. The power supply device according to claim 1, further comprising a full-wave rectifier circuit, the full-wave rectifier circuit rectifies an AC input, and supplies the rectified output to the input end. 8. The power supply device according to claim 1, wherein the control circuit inputs a detection signal of an output voltage appearing between the output terminals and a detection signal of a current flowing through the first switching element as an input signal. The phase of the output voltage detection signal is shifted by about 90 degrees, the signal after the phase shift is compared with the current detection signal, and the first switching element is controlled based on the comparison output signal. 9. The power supply device according to claim 1, wherein the control circuit changes the on-time width of the second switching element according to the magnitude of the input voltage. 10. The power supply device according to claim 1, wherein the control circuit controls the on-time width of the second switching element according to the magnitude of the output voltage. 11. The power supply device according to claim 1, wherein the control circuit prohibits the operation of the second switching element until the output voltage reaches a constant value. 12. The power supply device according to claim 1, wherein the control circuit uses an induced voltage generated in a third winding wound around the transformer as an auxiliary power supply. 13. The power supply device according to claim 1, wherein the control circuit has the second switching element in two periods after the first switching element is turned on and immediately before the first switching element is turned on. Turn on.