JPH09215326A - Switching power source apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power source apparatus which controls a rush current and assures high efficiency. SOLUTION: During the period where an AC power source VAC turns on and a switching element Q11 is on, a current i2 due to the rectified output of a diode bridge circuit D11 flows. In this case, a current i1 from the positive output terminal of D11 flows. With this current i1 , an energy is accumulated in the capacitor C11 and an energy is temporarily accumulated (held) in a choke coil L11. During the period where Q11 is OFF, the energy temporarily accumulated in the L11 generates a reverse electromotive force and flows as i3 and charges C11. That is, the energy temporarily accumulated in the L11 is recovered in the C11 to repeat the switching operation. Thereby, the energy is accumulated (C11 is charged). This accumulated energy provides the smoothed full-wave rectified output. Thereby, it is no longer required to use a rush current preventing circuit and an active filter circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device having a high power factor.

[0002]

2. Description of the Related Art Conventionally, this type of switching power supply device has been constructed as shown in FIG. As shown in FIG.
The output from the AC power supply VAC (eg, 100 V, 50 Hz) is full-wave rectified by the diode bridge circuit D60 and smoothed by the capacitor C60, so that the capacitor C
A DC voltage Vc is obtained across 60. This DC voltage Vc
Is switched at a high speed (for example, 20 kHz or higher) by the transistor Q60 and is applied to the primary winding of the inverter transformer T60. As a result, the inverter transformer T
AC voltage induced in the secondary winding of the diode 60
The output voltage V _out to be rectified and smoothed by the rectification smoothing circuit composed of the capacitor 61 and the capacitor C61 and supplied to the load is obtained. 6
2 is a control circuit for controlling the output voltage V _out by changing the duty ratio and the like of the signal applied to the base of the transistor Q60 based on the output voltage V _out information. Then, at the time of starting, the switch S60 between both ends of the charging resistor R60 provided between the diode bridge circuit D60 and the capacitor C60 is open in order to prevent an excessive inrush current from flowing in the capacitor C60, Therefore, the charging resistor R60 causes the capacitor C6 to
0 is charged to a predetermined voltage while suppressing an excessive inrush current, and after reaching a predetermined voltage, the switch S60 is closed.

However, in the above conventional example,
A switch S60 and a charging resistor R60 must be provided in order to prevent an excessive inrush current to the capacitor C60 at the time of start-up, and the failure of the switch S60 may account for many of the causes of failure of the entire device. Therefore, the presence of the switch S60 reduces the reliability of the device.

FIG. 7 shows the waveform of the input current I _in when power is supplied from the AC power supply VAC of 50 Hz in the above conventional example. As shown in FIG. 7, a rush current that gradually decreases until the capacitor C60 is charged to a predetermined voltage continues, and when the capacitor C60 reaches a predetermined voltage and the switch S60 is closed, a pulsed harmonic component is generated. Charging current will flow. As described above, in the above-described conventional example, since the input current I _in includes a large amount of harmonic current during the normal operation, the power factor is reduced to about 0.5 to 0.6.

Therefore, as shown in FIG. 8, the circuit for obtaining the voltage Vc applied to the inverter transformer may be an active rectifying filter circuit to improve the power factor. This circuit stores energy in the choke coil L60 when the transistor Q60 conducts,
The energy released from the choke coil L60 when 60 is not conducting charges the capacitor C60. Then, the control circuit 63 turns on the transistor Q60 based on the Vc information so that the input current I _in becomes a sine wave.
By performing the off control, the power factor can be improved to about 0.9.

[0006]

Inrush current cannot be prevented even with such an active rectifying filter circuit. That is, an excessive current flows through the capacitor C60 through the choke coil L60 as an inrush current. Therefore, as shown in FIG. 8, a resistor R61 and a diode D63 connected in series are connected to the rectified sine output terminal of the diode bridge circuit D60 and the cathode of the diode D62 as shown in FIG. To cope with this, an inrush prevention circuit composed of the resistor R60 and the switch S60 is inserted.

However, in the active rectifying filter circuit as shown in FIG. 8, it is necessary to further provide an inverter circuit (switching circuit) after that to form a switching power supply device.
It is not preferable because it becomes a place. Further, in such a switching power supply device, it is necessary to use a large capacity choke coil L60, which increases the cost of the device.

Therefore, an object of the present invention is to solve the above problems, effectively reduce the harmonic components of the input current without using an active rectifying filter circuit, and further without using an inrush current prevention circuit. Another object of the present invention is to provide a high power factor switching power supply device capable of preventing an inrush current.

[0009]

According to the present invention, an inverter transformer and an alternating current from an alternating current power source are rectified, and one output terminal of a direct current obtained by the rectification is a first terminal of a primary winding of the inverter transformer. The connected rectifier circuit, the other output terminal of the rectifier circuit and the inverter transformer 1
Energy is temporarily held by a switching element provided between the second terminal of the secondary winding and a current flowing through the switching element without passing through the primary winding only when the switching element is closed; By accumulating the retained energy when the switching element is opened,
Energy storage means for supplying the stored energy to the primary winding when the switching element is closed.

Further, in the present invention, the one output terminal is a negative output terminal, the other output terminal is a positive output terminal, and the energy storage means is a first terminal of a primary winding of the inverter transformer. A first diode having a cathode connected thereto, a second diode having a cathode connected to the second terminal of the primary winding, and one end connected to a connection point between the anode of the first diode and the anode of the second diode. The choke coil connected, the capacitor connected between the other end of the choke coil and the first terminal of the inverter transformer, and the cathode connected to the connection point between the capacitor and the other end of the choke coil. And a third diode whose anode is connected to the negative output terminal of.

Further, according to the present invention, the one output terminal is a negative output terminal, the other output terminal is a positive output terminal, and the energy storage means is a first terminal of a primary winding of the inverter transformer. A first diode having an anode connected to the first winding, a second diode having an anode connected to the second terminal of the primary winding, and one end at a connection point between the cathode of the first diode and the cathode of the second diode. Is connected to the choke coil, a capacitor connected between the other end of the choke coil and the first terminal of the inverter transformer, and an anode is connected to a connection point between the capacitor and the other end of the choke coil. And a third diode whose cathode is connected to the positive output terminal of the circuit.

Further, according to the present invention, the inverter transformer is set to 2 when the switching element on the primary winding side is closed.
It is characterized in that the rectifying means on the secondary winding side is configured to be in a non-conducting state.

Further, according to the present invention, the inverter transformer is set to 2 when the switching element on the primary winding side is closed.
It is characterized in that the rectifying means on the secondary winding side is configured to be in a conductive state.

Further, according to the present invention, the switching element is switching-controlled by self-excitation based on energy from the inverter transformer.

Further, in the present invention, a rectifier circuit in which the first choke coil and the alternating current from the alternating current power source are rectified, and the positive electrode output terminal of the direct current obtained by the rectification is connected to the first terminal of the first choke coil. A switching element provided between a negative output terminal of the rectifier circuit and a second terminal of the first choke coil; a first diode having a cathode connected to the first terminal of the first choke coil; A second diode having a cathode connected to the second terminal; a second choke coil having one end connected to a connection point between the anode of the first diode and the anode of the second diode; and a second choke coil of the second choke coil. The other end and the first
A capacitor connected between the first terminals of the choke coil, and a third diode having a cathode connected to a connection point between the capacitor and the other end of the second choke coil and an anode connected to a negative output terminal of the rectifier circuit. And having.

Further, according to the present invention, the first choke coil and the alternating current from the alternating current power source are rectified, and the negative electrode output terminal of the direct current obtained by the rectification is connected to the first terminal of the first choke coil. A circuit, a switching element provided between the positive output terminal of the rectifier circuit and the second terminal of the first choke coil, and a first diode whose anode is connected to the first terminal of the first choke coil. A second diode whose anode is connected to the second terminal, a second choke coil whose one end is connected to a connection point between the cathode of the first diode and the cathode of the second diode, and the second choke coil The other end of the first
A capacitor connected between the first terminals of the choke coil, and a third diode having an anode connected to the connection point between the capacitor and the other end of the second choke coil and a cathode connected to the positive output terminal of the rectifier circuit. And having.

[0017]

1 is a circuit diagram of a switching power supply device according to the present invention. As shown in FIG. 1, T11
Is an inverter transformer, D11 is a diode bridge circuit, and full-wave rectifies the output from the AC power supply VAC,
The positive output terminal is connected to the first terminal 11a of the primary winding of the inverter transformer T11. Second of the primary winding
The terminal 11b is connected to the drain of a switching element Q11 composed of a MOSFET (may be another semiconductor element such as a bipolar transistor), and the source of the switching element Q11 is connected to the negative output terminal of the diode bridge circuit D11.

The anode of a diode D0 for rectification is connected to the second terminal 11d of the secondary winding of the inverter transformer T11, and a smoothing is provided between the cathode of the diode D0 and the first terminal 11c of the secondary winding. A capacitor C0 is connected, and a DC output voltage V _{out is} output from both ends of this capacitor C0.
Is taken out. Reference numeral 12 denotes a control circuit that supplies a high-speed (for example, 20 kHz or more) switching signal to the gate of the switching element Q11, and, for example, a duty ratio of the switching signal given to the gate of the switching element Q11 based on the output voltage V _out. The output voltage V _out is controlled by changing the above.

An inverter transformer T1 as shown in FIG.
The connection method between 1 and other configurations (D11, Q11, D0, C0) is called an ON / OFF method, and the diode D0 is OFF during the ON (closed) period of the switching element Q11. It has been called in this way. That is, during the ON period of the switching element Q11, the diode bridge circuit D11 goes from the first terminal 11a to the second terminal 11b of the primary winding of the inverter transformer T11.
Current i ₂ flows from and the energy due to this i ₂ is 1
It is accumulated in the secondary winding (at this time, the induced current is blocked from flowing on the secondary winding side due to the polarity of the diode D0). Then, during the OFF period of the switching element Q11, the energy accumulated in the primary winding of the inverter transformer T11 is taken out from the secondary winding through the diode D0 and supplied to the load as the output voltage V _out .

When transmitting energy in the inverter transformer T11, the energy transmission efficiency and the like can be controlled by providing a gap in the core of the transformer and adjusting the magnetic permeability thereof.

Further, in the present invention, as shown in FIG. 1, only when the switching element Q11 is closed, the positive output terminal of the diode bridge circuit D11 is passed through the switching element Q11 without passing through the primary winding of the inverter transformer T11. It has energy storage means for temporarily holding energy by the flowing current i ₁ and storing the held energy when the switching element Q11 is opened. That is, the energy storage means includes a first diode D1 having a cathode connected to the first terminal 11a of the primary winding of the inverter transformer T11 and a first diode D1 having a cathode connected to the second terminal 11b of the primary winding. 2 diode D
2, a choke coil L11 whose one end is connected to a connection point between the anode of the first diode D1 and the anode of the second diode D2, and the other end of the choke coil L11 and the first terminal 11a of the inverter transformer T11. And a third diode D3 having a cathode connected to a connection point between the capacitor C11 and the other end of the choke coil L11 and an anode connected to a negative output terminal of the diode bridge circuit D11.

By including the energy storage means having the above structure, the switching power supply device operates as follows.

First, while the AC power supply VAC is on and the switching element Q11 is on, the positive output terminal of the diode bridge circuit D11, the primary winding of the inverter transformer T11, the switching element Q11, and the negative output of the diode bridge circuit D11. A current i ₂ due to the rectified output of the diode bridge circuit D11 flows through the terminal. At this time, the diodes D1 and D3 are off, while
Through the capacitor C11, the choke coil L11, and the switching element Q11, the diode bridge circuit D11
The current i ₁ flows from the positive electrode output terminal of. This current i ₁
As a result, energy is temporarily stored (held) in the choke coil L11.

Next, while the switching element Q11 is off, the energy temporarily stored in the choke coil L11 generates a counter electromotive force, which flows as a current i ₃ and charges the capacitor C11 through the first diode D1. To do. That is, the energy temporarily stored in the choke coil L11 is regenerated in the capacitor C11 and the switching is repeated to store (charge) the energy.

After the AC power supply VAC is turned on,
As the switching element Q11 repeatedly turns on and off, the charging voltage of the capacitor C11 rises until it reaches a steady state, but the charging voltage of the capacitor C11 is higher than the rectified output voltage of the AC power supply VAC at the positive output terminal of the diode bridge circuit D11. When the side voltage is high, during the ON period of the switching element Q11, instead of the current i ₂ ,
The current i ₄ generated by the discharge from the capacitor C11 is the primary winding of the inverter transformer T11 and the switching element Q1.
1, through diode D3.

Here, the AC power supply VA in the steady state
The voltage waveform of C, the full-wave rectified voltage waveform at the output of the diode bridge circuit D11, and the inverter transformer T1
The relationships between the voltage waveform and the current waveform of the first terminal 11a of the primary winding of No. 1 are shown in FIGS. In steady state, the first
The voltage of the terminal 11a tends to change in the same manner as the full-wave rectified voltage waveform of FIG. 5, but as described above, due to the charging voltage of the capacitor C11, the valley portion does not become 0V but a constant voltage. Hold. That is, the first terminal 11a
In, the current i ₂ flows in most of the voltage waveform except the valley portion, and the current i ₄ (discharge current of the capacitor C11) flows in the valley portion (constant voltage). Thus, even if the capacitance of the capacitor C11 is much smaller than that of the conventional example (thus, the inrush current can be suppressed), the smoothing action can be obtained. That is, the capacitor C11 need only gradually reach a predetermined charging voltage before the switching power supply device reaches a steady state, and therefore requires a smaller capacity than the capacitor C60 shown in FIG. Even without using an inrush current prevention circuit like (Fig. 6)
There are few paths through which the inrush current flows when the AC power supply VAC is turned on, and there is no cause for it. Also, the choke coil L11 is
Since it is sufficient to successively supply a small amount of charging energy to the capacitor C11 as described above, a smaller capacity than that of the choke coil L60 in the active rectification filter circuit shown in FIG. 8 is required, and the active rectification filter circuit is not used. Also, from the AC power supply VAC to the diode bridge circuit D
The harmonic component of the input current to 11 is remarkably reduced, and a high power factor is secured.

[0027]

EXAMPLE In the circuit shown in FIG. 1, the AC power supply VAC is 50 Hz and 100 VAC, and the value of the capacitor C11 is 1 of that of the conventional example (capacitor C60: 1000 μF in FIG. 6).
/ 4 or less, that is, between 250 μF, the value of the choke coil L11 is about 1 mH, and the switching frequency of the signal (duty ratio 50%) to the gate of the switching element Q11 is 100 kHz. 4A and 4B show how the voltage V _D , the voltage V _B between both ends of the third diode D3, the output voltage V _out , and the voltage V _C between both ends of the capacitor C11 are from the ON state of the AC power supply VAC to the steady state. , C. In the steady state, V _D (secondary winding of the primary winding of the inverter transformer T11
The voltage of the terminal 11b) is as shown in FIG. 9 (the maximum voltage is about 300V, the voltage at the valley is 140V), and at this time, 1
1a (voltage of the first terminal 11a of the primary winding of the inverter transformer T11) is as shown in FIG. That is, FIG.
As shown in (3), the valley portion of the full-wave rectified voltage waveform does not become 0V, but maintains about 70V. The energy for filling this portion (hatched portion) is the switching element Q11.
When is on, through C11, L11, D2, C11
The energy stored in the choke coil L11 and the energy stored in the choke coil L11 is regenerated by the capacitor C11 through the first diode D1 when the switching element Q11 is off, and is provided by the energy obtained as a result of charging.

The present invention is a separately excited type ON / O described above.
It is applicable not only to the FF type switching power supply device but also to a self-excited ON / OFF type switching power supply device. FIG. 2 shows an example in which the present invention is applied to an RCC (ringing choke converter). In FIG. 2, reference numerals of the energy storage means are shown in the same manner as in FIG. Further, in FIG. 2, reference numeral 21 denotes a control circuit for switching and stabilizing the output voltage, which is well known and may have another configuration.

Further, the present invention is not limited to the ON / OFF method, but when the switching element Q12, which is switching-controlled by the control signal based on the output voltage V _OUT information from the control circuit 121 as shown in FIG. 12, is ON. Rectifier diode D12 on the secondary winding side of the inverter transformer T12
Can be similarly applied to an ON / ON type switching power supply device in which the power is turned on. Further, as shown in FIG. 3, a choke coil L31 is used instead of the inverter transformer.
Can be applied to a system in which a transistor Q31 that is switching-controlled by a signal from the control circuit 31 is used.
It can also be applied to a partial resonance type converter, a multi-output type converter having a plurality of circuits on the secondary side, and the like.

In addition, as shown in FIG. 13, the present invention can be applied to a connection configuration (polarity) which is completely opposite to the configuration of FIG. 1. As shown in FIG. The present invention can also be applied to a connection configuration of completely opposite (polarity).

In addition, the present invention is based on FIG. 15 and FIG.
It can be applied to a fluorescent lamp inverter device as shown in FIG. That is, FIG. 15 is based on the basic configuration of FIG. 1 and includes a choke coil between the midpoint (first terminal 110a) of the primary winding of the inverter transformer T110 and the positive output terminal of the diode bridge circuit D11. L12
0 is connected between the second terminal 110b and the third terminal 110c at both ends of the primary winding of the inverter transformer T110 and the negative output terminal of the diode bridge circuit D11.
The switching element Q110 and the second switching element Q120 are respectively connected, the capacitor C _T is connected between the second terminal 110b and the third terminal 110c, and the capacitor C10 is connected across the secondary winding of the inverter transformer T110.
A fluorescent lamp 150 as a load is connected via 0, and the control terminals (gates) of the first switching element Q110 and the second switching element Q120 have the same frequency (180 degrees out of phase from the control circuit 120). It is controlled by each control signal of, for example, 100 kHz. According to such a configuration, the energy accumulated and released in the choke coil L120 responds to the switching of the two switching elements Q110 and Q120 from the midpoint (first terminal 110a) of the primary winding of the inverter transformer T110. Flow alternately to the second terminal 110b side and the third terminal 110c side to generate an AC output on the secondary winding side and supply the AC output to the fluorescent lamp 150 which is a load.

Therefore, according to the configuration as shown in FIG. 15, an inrush current preventing circuit is not required, and an inverter device for a fluorescent lamp with less "flickering" can be obtained. Note that FIG.
16 is an “externally excited type” by the control circuit 120.
, The switching elements Q110 and Q12
"Self-excited type" using an inverter transformer T110 having a winding 160 for self-excitation for obtaining a control signal of 0
The present invention can be applied to the above inverter device for fluorescent lamps. Further, the inverter transformer T11 shown in FIGS.
It is also possible to construct a DC power supply device by rectifying the output of the secondary winding of 0 without supplying it to the fluorescent lamp load.

[0033]

As described above, according to the present invention, the inrush current can be effectively suppressed without using the conventional inrush current prevention circuit composed of the resistor and the switch, and the conventional active rectification can be performed. The harmonic components of the input current can be significantly reduced without using a filter circuit. Therefore, compared to the case of using an active rectification filter circuit to improve the power factor, not only can the device be made less expensive, the size and weight can be reduced, but the failure caused by the inrush current prevention circuit can be completely eliminated. A switching power supply device of high power factor type which can be eliminated and has higher reliability can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of another embodiment of the present invention.

FIG. 3 is a circuit diagram of still another embodiment of the present invention.

FIG. 4 is a diagram showing voltage waveforms at various parts of the embodiment of the present invention.

5 is a diagram showing voltage and current waveforms at various parts of the device of FIG.

FIG. 6 is a diagram showing a circuit example of a conventional switching power supply device.

7 is a diagram showing a current waveform based on the circuit example of FIG.

FIG. 8 is a diagram showing a circuit example of a power supply device using a conventional active filter rectifier circuit.

9 is a detailed waveform diagram of V _{D in} FIG. 1. FIG.

10 is a detailed waveform diagram of V _B of FIG. 1. FIG.

FIG. 11 is an explanatory diagram of the same V _B.

FIG. 12 is a circuit diagram of still another embodiment of the present invention.

FIG. 13 is a circuit diagram of still another embodiment of the present invention.

FIG. 14 is a circuit diagram of still another embodiment of the present invention.

FIG. 15 is a circuit diagram of still another embodiment of the present invention.

FIG. 16 is a circuit diagram of still another embodiment of the present invention.

[Explanation of symbols]

 D11 Diode bridge circuit D1, D2, D3, D0 Diode C11, C0 Capacitor L11 Choke coil T11 Inverter transformer Q11 Switching element 12 Control circuit

Claims (8)

[Claims] 1. An inverter transformer, a rectifier circuit for rectifying alternating current from an alternating current power source, and one output terminal of direct current obtained by the rectification being connected to a first terminal of a primary winding of the inverter transformer. A switching element provided between the other output terminal of the rectifier circuit and the second terminal of the primary winding of the inverter transformer, and through the switching element without passing through the primary winding only when the switching element is closed. Energy is temporarily retained by the flowing current, and the retained energy is accumulated when the switching element is opened, so that the accumulated energy is 1 when the switching element is closed.
A switching power supply device comprising an energy storage means capable of supplying the secondary winding. 2. The first output terminal is a negative output terminal, the other output terminal is a positive output terminal, and the energy storage means is a first terminal of a primary winding of the inverter transformer. A first diode having a cathode connected to the first winding, a second diode having a cathode connected to the second terminal of the primary winding, and one end at a connection point between the anode of the first diode and the anode of the second diode A choke coil connected to the choke coil, a capacitor connected between the other end of the choke coil and the first terminal of the inverter transformer, and a cathode connected to a connection point between the capacitor and the other end of the choke coil. A switching power supply device comprising: a third diode whose anode is connected to a negative output terminal of the circuit. 3. The output terminal according to claim 1, wherein the one output terminal is a negative output terminal, the other output terminal is a positive output terminal, and the energy storage means is a first terminal of a primary winding of the inverter transformer. A first diode having an anode connected to the first winding, a second diode having an anode connected to the second terminal of the primary winding, and one end at a connection point between the cathode of the first diode and the cathode of the second diode. Is connected to the choke coil, a capacitor connected between the other end of the choke coil and the first terminal of the inverter transformer, and an anode is connected to a connection point between the capacitor and the other end of the choke coil. A switching power supply device comprising: a third diode whose cathode is connected to a positive output terminal of the circuit. 4. The inverter transformer according to claim 1, wherein the rectifying means on the secondary winding side is non-conductive when the switching element on the primary winding side is closed. A switching power supply device characterized by the above. 5. The inverter transformer according to claim 1, wherein the rectifying means on the secondary winding side is in a conductive state when the switching element on the primary winding side is closed. Switching power supply device characterized by. 6. The switching power supply device according to claim 4, wherein the switching element is switching-controlled by self-excitation based on energy from the inverter transformer. 7. The first choke coil and the positive electrode output terminal of the direct current obtained by rectifying the alternating current from the alternating current power source and rectifying the first alternating current of the first choke coil.
A rectifier circuit connected to the terminal, a switching element provided between the negative output terminal of the rectifier circuit and the second terminal of the first choke coil, and a cathode connected to the first terminal of the first choke coil. A first diode, a second diode whose cathode is connected to the second terminal, and a second choke coil whose one end is connected to a connection point between the anode of the first diode and the anode of the second diode. A capacitor connected between the other end of the second choke coil and the first terminal of the first choke coil, and a cathode connected to a connection point between the capacitor and the other end of the second choke coil And a third diode whose anode is connected to the negative output terminal of the switching power supply device. 8. The first choke coil and a first negative electrode of the first choke coil, which rectifies alternating current from an alternating current power source and has a negative electrode output terminal of direct current obtained by the rectification.
A rectifier circuit connected to the terminal, a switching element provided between the positive output terminal of the rectifier circuit and the second terminal of the first choke coil, and an anode connected to the first terminal of the first choke coil A first diode, a second diode whose anode is connected to the second terminal, and a second choke coil whose one end is connected to a connection point between the cathode of the first diode and the cathode of the second diode. A capacitor connected between the other end of the second choke coil and the first terminal of the first choke coil, and an anode connected to a connection point between the capacitor and the other end of the second choke coil, and the rectifier circuit And a third diode whose cathode is connected to the positive output terminal of the switching power supply device.