JP2003284348A - Power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform an efficiency improvement and downsizing by reducting circuit loss. <P>SOLUTION: A power unit controls the switching of switching elements Q1-Q3 by a control circuit so that a period when an inductor L1 exists within a closed loop including an input power source E and a load LD at the same time is not generated. Accordingly, the number of elements can be reduced by the common use of the inductor L1, and the circuit can largely be downsized by making the waveform of the current flowing to the inductor roughly trapezoid, thereby suppressing the peak of a current and downsizing the inductor L1. Moreover, since an input current IL<SB>1</SB>flowing to the inductor L1 in all periods (first to third periods T1-T3) contributes to at least either an input current or an output current at all times, the current IL<SB>1</SB>flowing to the inductor L1 can largely be reduced more than conventional examples 1 and 2, and the large downsizing of the device becomes possible by the reduction of loss induced by the power conversion and the downsizing of the inductor L1. <P>COPYRIGHT: (C)2004,JPO

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.

[0002]

2. Description of the Related Art A conventional power supply device is shown in FIG. This power supply device (conventional example 1) uses an AC power supply AC.
And a rectifier circuit DB including a diode bridge, an inductor L1, a switching element Q1, a diode D1 and a smoothing capacitor C0, and a boost type PFC for boosting a pulsating voltage rectified by the rectifier circuit DB to a desired DC voltage. (Power factor improvement) A buck type DC / D that is composed of a converter, a switching element Q2, a diode D2 and an inductor L2 and reduces the DC voltage output from the PFC converter to a desired level and supplies it to the load LD.
And a C converter. PFC converter and DC
Each of the / DC converters has a conventionally well-known configuration, and performs desired power conversion by switching the switching elements Q1 and Q2 at a high frequency by a control circuit (not shown).

Here, the operation of the prior art example 1 will be briefly described with reference to FIGS. First, in the PFC converter, as shown in FIG. 23B, the switching element Q1 is switched by the drive signal VQ1 having a frequency sufficiently higher than the power supply frequency of the AC power supply AC, so that the power supply voltage of the AC power supply AC is higher than the peak. It outputs the DC voltage boosted to a high level. As shown in FIG. 24 (a), when the switching element Q1 is turned on by the drive signal VQ1, the inductor L from the AC power supply AC via the rectifier circuit DB.
1 and the switching element Q1, an input current flows, energy is accumulated in the inductor L1, and the switching element Q1
When 1 is turned off, as shown in FIG.
Also, the smoothing capacitor C0 is charged by the release of the energy stored in the inductor L1, and the capacitor C0 is charged.
At both ends of 0, a DC voltage boosted to a level higher than the peak of the power supply voltage of the AC power supply AC is obtained. Note that, as shown in FIG. 23A, a triangular-wave current I _L1 that increases during the ON period of the switching element Q1 and decreases during the OFF period flows through the inductor L1.

On the other hand, the DC / DC converter has a load LD.
It becomes a current limiting element for the alternating current, and as shown in FIG.
Drive signal with a frequency sufficiently higher than the power frequency of the power supply AC
No. VQ2 switches the switching element Q2
As a result, a desired current is supplied to the load LD. Figure 24 (a)
As shown in, the switching element Q is driven by the drive signal VQ2.
When 2 turns on, the charge stored in the capacitor C0 is released.
By doing so, the current flows and is limited by the inductor L2.
It is supplied to the load LD. Then, the switching element Q2
When is turned off, the energy stored in the inductor L2 is released.
The current continues to flow in the load LD due to the output. In addition,
Switching to the ductor L2 as shown in FIG.
A triangular wave that increases during the on period of element Q2 and decreases during the off period
Current I _L2Flows.

Next, another conventional example is a power supply device shown in FIG. This conventional example (conventional example 2) is an AC power supply AC.
The switching element Q1, the inductor L3, the diode D2, and the smoothing capacitor C0 are connected in series between the output terminals of the rectifier circuit DB for full-wave rectifying the inductor L3.
Further, the switching element Q2 is connected in parallel with the diode D2, the switching element Q3 is connected between the connection point of the inductor L3 and the diode D2 and the low potential side output terminal of the rectifier circuit DB, and the switching element Q4 and the load LD are connected. The diode D1 is connected in parallel with the switching element Q3, and the diode D1 is connected in parallel with the inductor L3 and the switching element Q3.

The operation of the conventional example 2 will be described with reference to FIGS. Drive signals VQ1 to VQ4 are given to the respective switching elements Q1 to Q4 by a control circuit (not shown) to alternately switch the switching elements Q1 and Q2 as shown in FIGS. They are switching alternately.

First, during a period in which the switching elements Q1 and Q3 are on and the switching elements Q2 and Q4 are off (first period T1), as shown in FIG.
A closed loop of C → rectifier circuit DB → switching element Q1 → inductor L3 → switching element Q3 → rectifier circuit DB → AC power supply AC is formed and current flows. Then, the switching element Q1 is turned on and the switching elements Q2 and Q are turned on.
27, during a period in which Q3 and Q4 are off (second period T2).
As shown in (b), AC power supply AC → rectifier circuit DB → switching element Q1 → inductor L3 → diode D2 →
A closed loop of the capacitor C0 → rectifier circuit DB → AC power supply AC is formed, and a current flows. Next, in a period in which the switching elements Q1 and Q3 are off and the switching elements Q2 and Q4 are on (third period T3), as shown in FIG. 27C, the capacitor C0 → the switching element Q2 → the inductor L3 → the switching element. A closed loop of Q4 → load LD → capacitor C0 is formed and a current flows through the load LD.
Further, during the period in which the switching elements Q1, Q2, Q3 are off and the switching element Q4 is on (fourth period T4), the energy stored in the inductor L3 is released and the inductor L3 is released as shown in FIG. 27 (d). → switching element Q4 → load LD → diode D1 → inductor L
A closed loop 3 is formed, and a current flows through the load LD. Thus, by repeating one cycle of the first to fourth periods T1 to T4 in a period sufficiently shorter than the power source cycle of the AC power source AC, the boost type of the first and second periods T1 and T2 can be obtained. The function of the back type DC / DC converter is realized in the PFC converter and the second and fourth periods T3 and T4. Note that the inductor L3 is increased in the first and third periods T1 and T3 as shown in FIG.
The electric current of the triangular wave I _L3 that decreases in the periods T2 and T4 flows.

[0008]

However, the above-mentioned conventional example 1
In the above, since two independent converters of a boost type PFC converter and a buck type DC / DC converter are connected in series, there is a problem that the power conversion efficiency of the entire power supply device is reduced, and Since the inductors L1 and L2 are provided, there is a problem that the circuit becomes large.

On the other hand, in Conventional Example 2, although the number of elements can be reduced because the same function as in Conventional Example 1 can be achieved by using only one inductor L3, the peak of the current I _L3 flowing through the inductor L3 as shown in FIG. Is larger than the peaks of the currents I _L1 and I _L2 flowing through the inductors L1 and L2 in the conventional example 1, the inductor L3 becomes larger than the inductors L1 and L2, and the efficiency and the size of the circuit are improved. It is not possible.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a power supply device capable of improving efficiency and downsizing by reducing circuit loss.

[0011]

In order to achieve the above object, the present invention provides a power for converting an input from an input power source by including a switching element and an inductor and having a power factor improving function. The converter includes a converter, a switching element and the inductor, which limits the supply current to the load, and a controller which controls the switching of the switching element. The switching element is characterized in that a closed loop including one of the loads is always formed, and the switching element is controlled so as not to have a period for forming the closed loop including the inductor, the input power supply, and the load at the same time.

According to a second aspect of the present invention, in the first aspect of the present invention, the control means has a frequency sufficiently higher than the power supply frequency of the input power source with at least three periods as one cycle, and the inductor is used in the three periods. It is characterized in that the switching control is performed so that the voltage applied to the circuit is sequentially decreased.

According to a third aspect of the present invention, in the second aspect of the present invention, the power conversion means is provided with a smoothing capacitor at an output stage, and the control means controls the first period of the three periods. Switching so as to form a closed loop that discharges at least the charge charged in the capacitor, form a closed loop that does not include the capacitor in the second period, and form a closed loop that flows at least a charging current to the capacitor in the third period. It is characterized by controlling.

The invention of claim 4 relates to claim 1 or 2 or 3.
In the invention, a rectifying circuit for rectifying an AC power supply, a first switching element connected between output terminals of the rectifying circuit, the inductor, a fourth diode, a load, a third diode and a second switching element. And a third circuit connected in parallel with the fourth diode and the load.
Switching element, a first diode connected in anti-parallel to the series circuit between the output terminals of the rectifier circuit, a second diode whose cathode is connected to the low potential side output terminal of the rectifier circuit, and A series circuit of a fourth switching element connected between the anode of the second diode and the anode of the third diode, and a smoothing circuit connected between the anode of the second diode and the cathode of the third diode. And a capacitor.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) As shown in FIG. 1, a power supply device of this embodiment is connected between an AC power supply AC, a rectifier circuit DB including a diode bridge, and an output terminal of the rectifier circuit DB. Switching element Q1, inductor L
1, a diode D4, a load LD, a diode D3 and a switching element Q2 in a series circuit, a cathode is connected to a connection point of the switching element Q1 and the inductor L1, and an anode is connected to a low potential side output end of the rectifier circuit DB. Diode D1 and the cathode is a rectifier circuit DB
, A series circuit of a diode D2 connected to the low potential side output terminal and a switching element Q4 connected between the anode of the diode D2 and the anode of the diode D3, and a switching element connected in parallel with the diode D4 and the load LD. It is provided with Q3 and a smoothing capacitor C0 connected between the anode of the diode D2 and the cathode of the diode D3. Here, the four switching elements Q1 to Q4 are switching-controlled by drive signals VQ1 to VQ4 supplied from a control circuit (not shown).

Next, the operation of this embodiment will be described with reference to the time charts of the drive signals VQ1 to VQ4 of FIG. 2 and FIG.

First, the control circuit outputs drive signals VQ2 and VQ.
4 is output to turn on the switching elements Q2 and Q4 and turn off the switching elements Q1 and Q3 (first period T
In 1), as shown in FIG. 3A, capacitor C0 → switching element Q2 → diode D1 → inductor L1.
→ diode D4 → load LD → switching element Q4 →
A current flows in the closed loop of the capacitor C0. The equivalent circuit of this closed loop is shown in FIG. That is, the load LD is connected to both ends of the capacitor C0 via the inductor L1, and the current generated by the discharge of the capacitor C0 is limited by the inductor L1 and supplied to the load LD.

Subsequently, in a period (second period T2) in which the control circuit outputs the drive signal VQ4 to turn on the switching element Q4 and turn off the switching elements Q1 to Q3, as shown in FIG. 3 (b). L1 → diode D4
→ load LD → switching element Q4 → diode D2 →
A current flows in a closed loop of the diode D1 and the inductor L1. The equivalent circuit of this closed loop is shown in FIG. That is, a current is supplied to the load LD by discharging the energy stored in the inductor L1.

Next, drive signals VQ1 and VQ are sent from the control circuit.
3 is output to turn on the switching elements Q1 and Q3 and turn off the switching elements Q2 and Q4 (third period T
In 3), as shown in FIG. 3C, AC power supply AC → rectifier circuit DB → switching element Q1 → inductor L1 → switching element Q3 → diode D3 → capacitor C0.
→ Diode D2 → Rectifier circuit DB → Current flows in the closed loop of AC power supply AC. The equivalent circuit of this closed loop is shown in Fig. 4.
It is represented by (c). That is, DC power supply (AC power supply AC
The capacitor C0 is connected to the rectifier circuit DB) E via the inductor L1, and the charging current is supplied from the DC power supply E to the capacitor C0 via the inductor L1.

Thus, the above first to third periods T1 to T3
The operation with one cycle is more than the cycle of the AC power supply AC.
By repeating in a short period of time, in the third period T3
Boost-Type PFC Converter of Conventional Example 1, First and Second
Back type DC / DC of Conventional Example 1 in the periods T1 and T2 of 2
It realizes the function of the converter, and 1
One inductor L1 can be used for two types of converters
With, the number of elements can be reduced. Furthermore, in the first period T1
Voltage V across inductor L1_L1Is shown in FIG.
V from equivalent circuit_L1= V_C0-V_LDAnd the second period T2
Voltage V across inductor L1 at_L1’Is shown in FIG.
From the equivalent circuit of (b), V_L1’= -V_LDAnd the third period
Voltage V across inductor L1 during interval T3_L1"Is the figure
From the equivalent circuit of 4 (c), V_L1"= V_E-V_C0Becomes However
And then V_EIs the power supply voltage of the DC power supply E, V_LDIs both load LD
Edge voltage, V_C0Indicates the voltage across capacitor C0.
is doing. Here, the voltage V across the capacitor C0_C0Is P
The power supply voltage V of the DC power supply E by the function of the FC converter_E
Is always higher than that of the first to third periods T1 to T3.
Voltage V across inductor L1 at_L1, V_L1’,
V_L1In between_L1> V_L1’V_L1"The relationship of magnitude is always
It will be established. Therefore, the inductor L1
Current I_L1, I_L1’, I_L11st-3rd period T1 of
Slope ΔI at ~ T3 _L1, ΔI_L1’, ΔI_L1”
I_L1> ΔI_L1’＞ ΔI_L1The magnitude relationship of "is established, and
The current I flowing through the inductor L1 as shown_L1Is a trapezoidal wave
Becomes

That is, the power conversion amount increases / decreases in proportion to the average value of the amount of current flowing through the inductor L1, but in the present embodiment, the waveform of the current I _L1 flowing through the inductor L1 is substantially trapezoidal. The average value of the current amount can be maintained at substantially the same level while suppressing the peak value of the current I _L1 as compared with the triangular wave as in the conventional examples 1 and 2. As a result, in the present embodiment, the inductor L1 can be downsized as compared with the inductor L3 of the second conventional example, and thus the entire circuit can be downsized.

By the way, in the conventional example 2, the boost converter operates as the boost converter in the first and second periods T1 and T2.
Although it operates as a buck converter in the fourth periods T3 and T4, if the input / output voltage is the same and the voltage across the capacitor C0 is twice the input / output voltage, the current I _L1 flowing in the inductor _L1 is input. The time contributing to the current and the time contributing to the output current (load current) are equally divided (50% each). This means that the individual power conversion of the boost converter or the buck converter must be performed within a half period of the conventional example 1, and the conventional examples 1 and 2 are so-called critical current mode (current flowing in the inductor L1. Is operated in an operation mode in which the switching element is switched at a critical point at which is discontinuous to continuous, the peak value of the current I _L3 flowing through the inductor L3 of Conventional Example 2 is the current flowing through the inductors L1 and L2 of Conventional Example 1. I
_It is about twice the peak value of _L1 and _IL2 .

However, in this embodiment, the inductor L is used in all the periods (first to third periods T1 to T3).
Since the current I _L1 flowing in 1 always contributes to at least one of the input current and the output current, the inductor L1
The current I _L1 flowing in the inductor can be significantly reduced as compared with the conventional examples 1 and 2, and the loss due to the power conversion and the inductor L can be reduced.
It is possible to reduce the size of the entire device by reducing the size of item 1.

In this embodiment, the input power source E and the load L
In order to prevent a period in which the inductor L1 exists in the closed loop including D at the same time, the control circuit uses the switching element Q1.
Switching control is performed on 1 to Q4. Here, if the circuit loss is ignored, the input power before power conversion and the output power after conversion are the same, so if the load voltage V _LD is much higher than the power supply voltage V _E , the output current (load current) will be the input current. This is much smaller than the current, and the period during which the current I _L1 flowing in the inductor L1 contributes to the output current may be short.

On the other hand, when a closed loop in which the input current flows directly to the load LD via the inductor L1 is formed, power conversion is directly performed from the input power source E to the load LD,
It often improves the efficiency of power conversion. However, such direct power conversion is effective when the period of the power conversion has a higher temporal ratio than other periods, but as described above, the load voltage V _LD is higher than the power supply voltage V _E. Since the above-mentioned temporal ratio is extremely small under the condition of being extremely high, the adverse effect due to the increase in switching loss becomes greater.

Therefore, the power supply device of the present embodiment prevents the period in which the inductor L1 exists in the closed loop that simultaneously includes the input power supply E and the load LD as described above, and therefore the load voltage V _LD is equal to the power supply voltage. It can be said that the power supply device is suitable when it is extremely higher than V _E.

(Embodiment 2) The power supply device of this embodiment is
The circuit configuration is the same as that of the first embodiment, but the timing of switching control of the switching elements Q1 to Q4 by the control circuit is different. Therefore, the illustration and description of the circuit configuration are omitted, and the operation characteristic of the present embodiment will be described with reference to FIGS. 6 and 7.

First, the control circuit outputs drive signals VQ2 and VQ.
4 is output to turn on the switching elements Q2 and Q4 and turn off the switching elements Q1 and Q3 (first period T
In 1), similarly to the first period T1 in the first embodiment, as shown in FIG. 7A, capacitor C0 → switching element Q2 → diode D1 → inductor L1 → diode D4 → load LD → switching element Q4 → capacitor. Current flows in the closed loop of C0. The equivalent circuit of this closed loop is shown in FIG. That is, the load LD is connected to both ends of the capacitor C0 via the inductor L1, and the current generated by the discharge of the capacitor C0 is applied to the inductor L1.
And the current is supplied to the load LD.

Then, drive signals VQ1 and VQ are output from the control circuit.
Q3, VQ4 are output to output switching elements Q1, Q3
During a period in which Q4 is turned on and switching element Q2 is turned off (second period T2), as shown in FIG. 7B, AC power supply AC → rectifier circuit DB → switching element Q1 → inductor L1 → switching element Q3 → switching element Q4
→ Diode D2 → Rectifier circuit DB → Current flows in the closed loop of AC power supply AC. The equivalent circuit of this closed loop is shown in FIG.
It is represented by (b). That is, the inductor L1 is connected to the DC power supply E, and the current is supplied from the DC power supply E to the inductor L1.

Next, drive signals VQ1 to VQ are sent from the control circuit.
During a period (third period T3) in which all the switching elements Q1 to Q4 are turned off without outputting 4 as shown in FIG. 7C, the inductor L1 → diode D4 → load LD → diode D3 → capacitor C0 → A current flows in a closed loop of diode D2 → diode D1 → inductor L1. The equivalent circuit of this closed loop is shown in FIG.
That is, the load LD and the capacitor C0 are connected in series at both ends of the inductor L1, and a current is supplied to the load LD and the capacitor C0 by discharging the energy accumulated in the inductor L1.

Thus, the above first to third periods T1 to T3
Is repeated for a period sufficiently shorter than the power supply cycle of the AC power supply AC, so that the boost-type PFC converter of the first conventional example in the second and third periods T2 and T3, the first and the third In the periods T1 and T3, the function of the buck type DC / DC converter of Conventional Example 1 is realized. Further, the voltage V _L1 across the inductor L1 during the first period T1 is V _L1 = V _C0 −V _LD from the equivalent circuit of FIG. 8A, and the voltage V _L1 ′ across the inductor L1 during the second period T2. Is V _L1 ′ = V _E from the equivalent circuit of FIG. 8B, and the voltage V _L1 ″ across the inductor L1 in the third period T3 is V _L1 ″ = −V from the equivalent circuit of FIG. 8C. _C0
-V _LD . Therefore, like the first embodiment, the first to third
Voltage V across the inductor L1 in the period T1 to T3 of
_Since the magnitude relationship of V _L1 > V _L1 '> V _L1 ″ is always established between _{L 1} , V _L1 ′, and V _L1 ″, the inductor L 1
ΔI _L1 > ΔI _L1 ′> ΔI _L1 ″ in the gradients ΔI _L1 , ΔI _L1 ′, ΔI _L1 ″ of currents I _L1 , I _L1 ′, I _L1 ″ flowing in the first to third periods T 1 to T 3 The relationship is established, and the current I _L1 flowing in the inductor L1 becomes a substantially trapezoidal wave as shown in FIG.

Therefore, similarly to the first embodiment, the present embodiment can also improve the efficiency and reduce the size by reducing the circuit loss as compared with the conventional examples 1 and 2.

(Embodiment 3) The power supply device of this embodiment is
The circuit configuration is the same as that of the first embodiment, but the timing of switching control of the switching elements Q1 to Q4 by the control circuit is different. Therefore, the illustration and description of the circuit configuration are omitted, and the operation characteristic of the present embodiment will be described with reference to FIGS. 10 and 11.

First, the control circuit outputs drive signals VQ1 to VQ.
4 is outputted and all the switching elements Q1 to Q4 are turned on (first period T1), as shown in FIG. 11A, AC power supply AC → rectifier circuit DB → inductor L1 →
A current flows in a closed loop of switching element Q3 → switching element Q4 → capacitor C0 → switching element Q2 → rectifier circuit DB → AC power supply AC. The equivalent circuit of this closed loop is shown in FIG. That is, the inductor L1 is provided at both ends of the series circuit of the DC power source E and the capacitor C0.
Are connected to supply current to the inductor L1 due to discharge of the DC power source E and the capacitor C0.

Subsequently, in the period (second period T2) in which the drive signal VQ4 is output from the control circuit to turn on the switching element Q4 and turn off the switching elements Q1 to Q3, the second period T2 of the first embodiment is set. Similarly, as shown in FIG. 11B, inductor L1 → diode D4 → load LD →
Switching element Q4 → diode D2 → diode D
1 → Current flows in a closed loop of inductor L1. The equivalent circuit of this closed loop is shown in FIG. That is, a current is supplied to the load LD by discharging the energy stored in the inductor L1.

Next, drive signals VQ1 to VQ are sent from the control circuit.
In the period in which all the switching elements Q1 to Q4 are turned off without outputting 4 (third period T3),
11C, the inductor L1 → the diode D4 → the load LD → the diode D3 as in the period T3.
→ capacitor C0 → diode D2 → diode D1 →
A current flows in the closed loop of the inductor L1. The equivalent circuit of this closed loop is shown in FIG. That is, the load LD and the capacitor C0 are connected in series at both ends of the inductor L1, and a current is supplied to the load LD and the capacitor C0 by discharging the energy accumulated in the inductor L1.

Thus, the above first to third periods T1 to T3
Is repeated for a period sufficiently shorter than the power supply cycle of the AC power supply AC, so that the boost-type PFC converter, the second and third PFC converters according to the conventional example 1 are executed in the first and third periods T1 and T3. The functions of the Buck type DC / DC converter of Conventional Example 1 are realized in the periods T2 and T3. Further, the voltage V _L1 across the inductor L1 in the first period T1 is V _L1 = V _E + V _C0 from the equivalent circuit of FIG.
Therefore, the voltage V _L1 ′ across the inductor L1 during the second period T2 is V _L1 ′ = − from the equivalent circuit of FIG.
It becomes V _LD , and the voltage V _L1 ″ across the inductor L1 during the third period T3 is V _L1 ″ from the equivalent circuit of FIG.
= The -V _C0 -V _LD. Therefore, both end voltages V _L1 of the inductor L1 in the first to third periods T1~T3 similarly to Embodiment 1, V _L1 ', V _L1 between V _L1 "> V _L1'> V
"Because so that the magnitude relationship is always established, the current I _L1, I _L1 flowing to inductor L1 _L1 ', I _L1" gradient [Delta] I _L1 in the first to third periods T1~T3 of, [Delta] I _L1', delta
I _L1 ″ also satisfies the magnitude relationship of ΔI _L1 > ΔI _L1 ′> ΔI _L1 ″, and the current I _L1 flowing through the inductor L ₁ becomes a substantially trapezoidal wave (see FIG. 5).

Therefore, in the present embodiment as well as in the first embodiment, the efficiency can be improved and the size can be reduced by reducing the circuit loss as compared with the conventional examples 1 and 2.

(Embodiment 4) The power supply device of this embodiment is
The circuit configuration is the same as that of the first embodiment, but the timing of switching control of the switching elements Q1 to Q4 by the control circuit is different. Therefore, the illustration and description of the circuit configuration are omitted, and the operation characteristic of the present embodiment will be described with reference to FIGS. 13 and 14.

First, the control circuit outputs drive signals VQ1 to VQ.
4 is output to turn on all the switching elements Q1 to Q4 (first period T1), as in the first period T1 of the third embodiment, as shown in FIG. → Rectifier circuit DB → Inductor L1 → Switching element Q3 → Switching element Q4 → Capacitor C0 → Switching element Q2 → Rectifier circuit DB → Current flows in the closed loop of the AC power supply AC. The equivalent circuit of this closed loop is shown in FIG.
It is represented by (a). That is, the inductor L1 is connected to both ends of the series circuit of the DC power supply E and the capacitor C0, and the current generated by the discharge of the DC power supply E and the capacitor C0 is supplied to the inductor L1.

Subsequently, drive signals VQ1 and VQ are output from the control circuit.
Q3, VQ4 are output to output switching elements Q1, Q3
During the period in which Q4 is turned on and the switching element Q2 is turned off (second period T2), as in the second period T2 of the second embodiment, as shown in FIG. 14B, the AC power source AC → rectifier circuit DB → Switching element Q1 → inductor L1 → switching element Q3 → switching element Q4 → diode D2 → rectifier circuit DB → current flows in a closed loop of AC power supply AC. The equivalent circuit of this closed loop is shown in FIG. That is, the inductor L1 is connected to the DC power supply E, and the current is supplied from the DC power supply E to the inductor L1.

Next, drive signals VQ1 to VQ are sent from the control circuit.
In the period in which all the switching elements Q1 to Q4 are turned off without outputting 4 (third period T3),
14C, the inductor L1 → the diode D4 → the load LD → the diode D3 as in the period T3.
→ capacitor C0 → diode D2 → diode D1 →
A current flows in the closed loop of the inductor L1. The equivalent circuit of this closed loop is shown in FIG. That is, the load LD and the capacitor C0 are connected in series at both ends of the inductor L1, and a current is supplied to the load LD and the capacitor C0 by discharging the energy accumulated in the inductor L1.

Thus, the above first to third periods T1 to T3
The operation with one cycle is more than the cycle of the AC power supply AC.
By repeating for a short period of time, the second and third periods
Boost type PFC converter of conventional example 1 between T2 and T3
In the third period T3, the back type DC / DC of the conventional example 1
It realizes the function of the converter. Furthermore, the first period
Voltage V across inductor L1 at T1_L1Is shown in FIG.
From the equivalent circuit of (a), V_L1= V_E+ V_C0And then the second
Voltage V across inductor L1 during period T2_{L 1}’
From the equivalent circuit of FIG._L1’= V_EAnd third
Voltage V across inductor L1 during period T3 of_L1”
Is V from the equivalent circuit of FIG._L1"= -V_C0-V_LD
Becomes Therefore, similar to the first embodiment, the first to third periods
The voltage V across the inductor L1 at T1 to T3_L1, V
_L1’, V_L1In between_L1> V_L1’V_L1Relationship between
Is always satisfied, the current flows to inductor L1.
Current I_L1, I_L1’, I_L1In the first to third periods T1 to
Slope ΔI at T3_L1, ΔI _L1’, ΔI_L1Also in ΔI
_L1> ΔI_L1’＞ ΔI_L1The magnitude relationship of
Current I flowing through_L1Becomes a trapezoidal wave (see Figure 9).
See).

Therefore, similarly to the first embodiment, the present embodiment can improve efficiency and downsize by reducing the circuit loss as compared with the conventional examples 1 and 2.

(Embodiment 5) The power supply device of this embodiment is
The circuit configuration is the same as that of the first embodiment, but the timing of switching control of the switching elements Q1 to Q4 by the control circuit is different. Therefore, the illustration and description of the circuit configuration are omitted, and the operation characteristic of the present embodiment will be described with reference to FIGS. 16 and 17.

First, the control circuit outputs drive signals VQ1 to VQ.
4 is output to turn on all the switching elements Q1 to Q4 (first period T1), as in the first period T1 of the third embodiment, as shown in FIG. → Rectifier circuit DB → Inductor L1 → Switching element Q3 → Switching element Q4 → Capacitor C0 → Switching element Q2 → Rectifier circuit DB → Current flows in the closed loop of the AC power supply AC. The equivalent circuit of this closed loop is shown in FIG.
It is represented by (a). That is, the inductor L1 is connected to both ends of the series circuit of the DC power supply E and the capacitor C0, and the current generated by the discharge of the DC power supply E and the capacitor C0 is supplied to the inductor L1.

Subsequently, in the period (second period T2) in which the control circuit outputs the drive signal VQ4 to turn on the switching element Q4 and turn off the switching elements Q1 to Q3, the second period T2 of the first embodiment is set. Similarly, as shown in FIG. 17B, inductor L1 → diode D4 → load LD →
Switching element Q4 → diode D2 → diode D
1 → Current flows in a closed loop of inductor L1. The equivalent circuit of this closed loop is shown in FIG. That is, a current is supplied to the load LD by discharging the energy stored in the inductor L1.

Next, the control circuit outputs drive signals VQ1 and VQ.
3 is output to turn on the switching elements Q1 and Q3 and turn off the switching elements Q2 and Q4 (third period T
3), similar to the third period T3 of the first embodiment, as shown in FIG.
As shown in 7 (c), current flows in a closed loop of AC power supply AC → rectifier circuit DB → switching element Q1 → inductor L1 → switching element Q3 → diode D3 → capacitor C0 → diode D2 → rectifier circuit DB → AC power supply AC. The equivalent circuit of this closed loop is shown in FIG. That is, the capacitor C0 is connected to the DC power source E via the inductor L1, and the charging current is supplied from the DC power source E to the capacitor C0 via the inductor L1.

Thus, the above first to third periods T1 to T3
Is repeated for a period sufficiently shorter than the power source cycle of the AC power supply AC, so that the boost-type PFC converter of the first conventional example and the second period T2 in the first and third periods T1 and T3 are repeated. Then, the back type DC / DC of Conventional Example 1
It realizes the function of the converter. Further, the voltage V _L1 across the inductor L1 in the first period T1 is as shown in FIG.
From the equivalent circuit of (a), V _L1 = V _E + V _C0 , and the voltage _{VL 1} ′ across the inductor L1 during the second period T2 is
From the equivalent circuit of FIG. 18B, V _L1 ′ = −V _LD , and the voltage V _L1 ″ across the inductor L1 during the third period T3.
18 will be V _L1 ″ = V _E −V _C0 from the equivalent circuit of FIG. 18C. Therefore, as in the first embodiment, the first to third periods T
The voltage V _L1 across the inductor L1 at 1 to T3,
Since the magnitude relation of V _L1 > V _L1 '> V _L1 ″ is always established between V _L1 ′ and V _L1 ″, the first of the currents I _L1 , I _L1 ′, I _L1 ″ flowing in the inductor L ₁ is determined. 1st to 3rd period T1
Also, the slopes ΔI _L1 , ΔI _L1 ′, and ΔI _L1 ″ at T3 are also Δ.
The magnitude relation of I _L1 > ΔI _L1 ′> ΔI _L1 ″ is established, and the current I _L1 flowing through the inductor L ₁ becomes a substantially trapezoidal wave (see FIG. 5).

Therefore, in the present embodiment as well as in the first embodiment, the efficiency can be improved and the size can be reduced by reducing the circuit loss as compared with the conventional examples 1 and 2.

(Embodiment 6) The power supply device of this embodiment is
The circuit configuration is the same as that of the first embodiment, but the timing of switching control of the switching elements Q1 to Q4 by the control circuit is different. Therefore, the illustration and description of the circuit configuration are omitted, and the operation characteristic of the present embodiment will be described with reference to FIGS. 19 and 20.

First, the control circuit outputs drive signals VQ2 and VQ.
4 is output to turn on the switching elements Q2 and Q4 and turn off the switching elements Q1 and Q3 (first period T
In 1), as in the first period T1 in the first embodiment, as shown in FIG. 20A, capacitor C0 → switching element Q2 → diode D1 → inductor L1 → diode D4 → load LD → switching element Q4 → capacitor. Current flows in the closed loop of C0. The equivalent circuit of this closed loop is shown in FIG. That is, the load LD is connected to both ends of the capacitor C0 via the inductor L1, and the current generated by the discharge of the capacitor C0 is limited by the inductor L1 and supplied to the load LD.

Subsequently, drive signals VQ1 and VQ are output from the control circuit.
Q3, VQ4 are output to output switching elements Q1, Q3
During the period in which Q4 is turned on and the switching element Q2 is turned off (second period T2), as in the second period T2 of the second embodiment, as shown in FIG. Switching element Q1 → inductor L1 → switching element Q3 → switching element Q4 → diode D2 → rectifier circuit DB → current flows in a closed loop of AC power supply AC. The equivalent circuit of this closed loop is shown in FIG. That is, the inductor L1 is connected to the DC power supply E, and the current is supplied from the DC power supply E to the inductor L1.

Next, drive signals VQ1 and VQ are sent from the control circuit.
3 is output to turn on the switching elements Q1 and Q3 and turn off the switching elements Q2 and Q4 (third period T
3), as in the third period T3 of the first embodiment, as shown in FIG.
As shown in 0 (c), current flows in a closed loop of AC power supply AC → rectifier circuit DB → switching element Q1 → inductor L1 → switching element Q3 → diode D3 → capacitor C0 → diode D2 → rectifier circuit DB → AC power supply AC. The equivalent circuit of this closed loop is shown in FIG. That is, the capacitor C0 is connected to the DC power source E via the inductor L1, and the charging current is supplied from the DC power source E to the capacitor C0 via the inductor L1.

Thus, the above first to third periods T1 to T3
The operation with one cycle is more than the cycle of the AC power supply AC.
By repeating for a short period of time, the second and third periods
Boost type PFC converter of conventional example 1 between T2 and T3
In the first period T1, the buck type DC / DC of the conventional example 1
It realizes the function of the converter. Furthermore, the first period
Voltage V across inductor L1 at T1_L121
From the equivalent circuit of (a), V_L1= V_C0-V_LDAnd then the second
Voltage V across inductor L1 during period T2 _L1’
From the equivalent circuit of FIG._L1’= V_EAnd third
Voltage V across inductor L1 during period T3 of_L1”
Is V from the equivalent circuit of FIG._L1"= V_E-V_C0When
Become. Therefore, as in the first embodiment, the first to third periods T
Voltage V across inductor L1 at 1-T3_L1，
V_L1’, V_L1In between_L1> V_L1’V_L1“Okozeki
Since the relationship is always established, the inductor L1 flows
Current I_L1, I_L1’, I_L11st-3rd period T1 of
Slope ΔI at ~ T3_L1, ΔI _L1’, ΔI_L1”
I_L1> ΔI_L1’＞ ΔI_L1The magnitude relationship of “
Current I flowing through the inductor L1_L1Becomes a trapezoidal wave (see Figure 9).
See).

Therefore, in the present embodiment as well as in the first embodiment, compared with the conventional examples 1 and 2, the efficiency can be improved and the size can be reduced by reducing the circuit loss.

[0057]

Since the present invention is configured as described above, the number of elements can be reduced by using the power conversion means and the current limiting means as an inductor, and the waveform of the current flowing through the inductor can be reduced. By using a trapezoidal shape, the peak value of the current can be suppressed and the average value of the amount of current can be maintained at substantially the same level, and the shared inductor can be downsized, and the entire circuit can be downsized. In addition, since the current flowing in the inductor always contributes to either the input current or the output current (load current), the peak value of the current flowing in the inductor is larger than the peak value of the current flowing in the conventional dual-purpose inductor. It is possible to reduce the loss due to power conversion and to reduce the size of the inductor to reduce the size of the entire device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a timing chart of drive signals in the above.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is an operation explanatory diagram of the above.

FIG. 5 is a waveform diagram of a current flowing through the inductor in the above.

FIG. 6 is a timing chart of drive signals according to the second embodiment.

FIG. 7 is an operation explanatory diagram of the above.

FIG. 8 is an operation explanatory diagram of the above.

FIG. 9 is a waveform diagram of a current flowing through the inductor in the above.

FIG. 10 is a timing chart of drive signals according to the third embodiment.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is an explanatory diagram of an operation of the above.

FIG. 13 is a timing chart of drive signals according to the fourth embodiment.

FIG. 14 is an explanatory diagram of an operation of the above.

FIG. 15 is an operation explanatory diagram of the above.

FIG. 16 is a timing chart of drive signals according to the fifth embodiment.

FIG. 17 is an explanatory diagram of the same operation as above.

FIG. 18 is an operation explanatory diagram of the above.

FIG. 19 is a timing chart of drive signals according to the sixth embodiment.

FIG. 20 is an operation explanatory diagram of the above.

FIG. 21 is an operation explanatory diagram of the above.

FIG. 22 is a circuit diagram showing a first conventional example.

FIG. 23 is a timing chart for explaining the same operation as above.

FIG. 24 is an explanatory diagram of the operation of the above.

FIG. 25 is a circuit diagram showing a second conventional example.

FIG. 26 is a timing chart for explaining the operation in the above.

FIG. 27 is an explanatory diagram of the operation of the above.

FIG. 28 is an explanatory diagram of the operation of the above.

[Explanation of symbols]

AC AC power supply DB rectifier circuit L1 inductor Q1-Q3 switching elements C0 capacitor D1 to D3 diode LD load

Claims (4)

[Claims] 1. A power conversion unit that includes a switching element and an inductor and that has a power factor correction function to convert the power from an input power source into an electric power, and a switching element and the inductor that limit the supply current to a load. Current limiting means for flowing current, and control means for controlling switching of the switching element, the control means always forms a closed loop including the inductor and either the input power supply or the load, and the inductor and the input. A power supply device characterized by performing switching control of the switching element so as not to have a period for forming a closed loop including a power supply and a load at the same time. 2. The control means performs switching such that at least three periods are set as one cycle and the voltage applied to the inductor is sequentially lowered at a frequency sufficiently higher than the power source frequency of the input power source and in the three periods. The power supply device according to claim 1, which is controlled. 3. The power conversion means includes a smoothing capacitor in an output stage, and the control means forms a closed loop that discharges at least a charge charged in the capacitor in a first period of the three periods. The switching control is performed so that a closed loop not including the capacitor is formed in a second period, and a closed loop in which at least a charging current to the capacitor is caused to flow is formed in a third period. Power supply. 4. A rectifier circuit for rectifying an AC power supply, and a first switching element connected between output terminals of the rectifier circuit,
A series circuit of the inductor, the fourth diode, the load, the third diode and the second switching element, a third switching element connected in parallel with the fourth diode and the load, and an output terminal of the rectifying circuit. A first diode connected in anti-parallel with the series circuit, a second diode whose cathode is connected to the low-potential-side output end of the rectifier circuit, and an anode of the second diode and a third diode; A series circuit of a fourth switching element connected between the anodes, and a smoothing capacitor connected between the anode of the second diode and the cathode of the third diode. The power supply device according to item 1 or 2 or 3.