JP6829220B2 - Switching power supply and its control method - Google Patents

Description

The present invention relates to a switching power supply device that generates a boosted voltage from an input voltage and further transforms the boosted voltage to generate an output voltage, and a control method thereof.

Conventionally, as disclosed in FIG. 1 of Patent Document 1, a boost chopper (force factor improving circuit) that generates a boost voltage from an input voltage and a full bridge converter that further transforms the boost voltage to generate an output voltage. There was a DC power supply consisting of (inverter circuit, transformer and rectifying smoothing circuit). Further, FIG. 2 shows a DC power supply device in which two of the above-mentioned boost choppers are connected in parallel to perform an interleave operation.

Further, as disclosed in Patent Document 2, the first arm is composed of first and second switching elements connected in series from the high side side, and the end portion on the low side side is connected to the ground. A second arm composed of third and fourth switching elements connected in series from the high side side and connected in parallel to the first arm, a high side end of the first arm, and an input power supply. A boosting inductor connected between the two, a fifth switching element whose one end is connected to the high side end of the first arm, and the other end of the fifth switching element connected to the ground. A transformer having a step-up capacitor and input and output windings, the input winding of which is connected between the connection points of the first and second switching elements and the connection points of the third and fourth switching elements. There was a converter composed of a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate a DC output voltage. This converter is an improvement of the DC power supply device shown in FIG. 1 of Patent Document 1, and has a configuration in which the switching element of the step-up chopper is also used as the switching element of the full bridge converter.

Japanese Unexamined Patent Publication No. 2011-130578 USP6038142

In the DC power supply device of FIG. 1 of Patent Document 1, a large ripple current flows through the boosting capacitor (output capacitor of the boosting chopper), so that a large boosting capacitor having a large allowable value of the ripple current is required. Further, in the DC power supply device of FIG. 2, since the ripple current is canceled by the interleaving operation, a small boosting capacitor can be used, but the number of switching elements (main switching element and rectifying element) increases. Further, both DC power supply devices have a problem that it is difficult to soft-switch the switching element of the step-up chopper.

The converter of Patent Document 2 can reduce the number of switching elements as compared with the DC power supply device of FIG. 2 of Patent Document 1, but since a large ripple current flows through the boosting capacitor, a large boosting capacitor is required.

Further, the converter of Patent Document 2 has a problem that it is difficult to increase the efficiency of the device when applied to a power supply device having a wide input voltage range. In Fig. 2 of Patent Document 1, energy is stored in the boost inductor during the period when the current i114 increases upward (this time is Tx), and if one switching cycle is Tsw, The boost ratio (= boost voltage / input voltage) increases as the time ratio Tx / Tsw increases, and decreases as the time ratio Tx / Tsw decreases. In addition, power is sent from the boost capacitor to the rectifying smoothing circuit through the transformer during the period when the voltage Vgs115 is at a high level (this time is Ty), and the transformation ratio (= output voltage / boost voltage) is the time ratio Ty. The higher / Tsw, the higher, and the lower, the lower. However, in order for this converter to operate normally, the relationship Tsw> Tx + Ty must be satisfied. For example, if the time ratio Tx / Tsw is increased, the time ratio Ty / Tsw will automatically decrease. It ends up.

Normally, when designing a power supply device with a wide input voltage range, a wide variable range of boost ratio is required to facilitate control of the output voltage, and when using this converter, the time ratio Tx / Tsw is variable. The time ratio Ty / Tsw must be set low to increase the width. On the other hand, in full-bridge converters, it is known that if the time ratio Ty / Tsw is set low, the transformer utilization efficiency decreases and the power loss increases, so keep the time ratio Ty / Tsw as high as possible. There is a situation that I want to. Therefore, the converter of Patent Document 2 is difficult to use for a power supply device having a wide input voltage range.

The present invention has been made in view of the above background technology, and can realize an operation of boosting an input voltage and further transforming it to generate an output voltage with a simple configuration, and can widen the variable range of the boost ratio. An object of the present invention is to provide a switching power supply device and a control method thereof.

The present invention is a circuit block composed of first, second and third switching elements connected in series in order , and one end of the third switching element, which is a low-side end of the circuit block, is An input voltage is applied to one end of the first arm connected to the ground, and the other end is connected to the connection points of the first and second switching elements to connect the first step-up inductor and the high side of the first arm. A circuit block consisting of a first step-up capacitor connected between a side end and the ground and fourth, fifth, and sixth switching elements connected in series in order , the circuit block. One end of the sixth switching element, which is the end on the low side , is connected to the ground, and the input voltage is applied to one end, and the other end is the fourth and fifth switching elements. It has a second step-up inductor connected to the connection point, a second step-up capacitor connected between the high-side end of the second arm and the ground, and an input winding and an output winding. Then, the transformer in which the input winding is connected between the connection point of the second and third switching elements and the connection point of the fifth and sixth switching elements, and the voltage generated in the output winding. A rectifying and smoothing circuit that generates a DC output voltage by rectifying and smoothing the above, and a switching control circuit that controls the output voltage by turning on and off the first to sixth switching elements at a predetermined switching cycle.
The first to fourth operation modes are set in the switching control circuit, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, and the third switching is performed. An operation mode in which the element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. The second operation mode is the first switching. The element is turned on, the second switching element is turned off, the third switching element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. The third operation mode is an operation mode, in which the first switching element is turned on, the second switching element is turned on, the third switching element is turned off, the fourth switching element is turned off, and the like. An operation mode in which the fifth switching element is turned on and the sixth switching element is turned on, and the fourth operation mode is the operation mode in which the first switching element is turned on and the second switching element is turned on. In the operation mode in which the third switching element is turned off, the fourth switching element is turned on, the fifth switching element is turned off, and the sixth switching element is turned on, the switching control circuit is one switching. It is a switching power supply device that controls the output voltage by sequentially executing the first to fourth operation modes in a cycle and adjusting the time ratio of each operation mode.

In this case, in the switching control circuit, when the first operation mode is started, after turning off the first and sixth switching elements, the voltage across the third and fifth switching elements is equal to or less than a certain value. When the third and fifth switching elements are controlled to be turned on and the second operation mode is started, the second switching element is turned off and then the first switching element is started. When the control to turn on the first switching element is performed at the timing when the voltage across the above drops below a certain level and the third operation mode is started, after turning off the third and fourth switching elements, When the second and sixth switching elements are controlled to be turned on at the timing when the voltage across the second and sixth switching elements drops below a certain level and the fourth operation mode is started, the fifth operation mode is started. After turning off the switching element, it is preferable to control the fourth switching element to be turned on at the timing when the voltage across the fourth switching element drops below a certain level. Further, the second step-up capacitor may also be used as the first step-up capacitor.

Further, the present invention has a first arm having first, second and third switching elements connected in series from the high side side, and an end portion on the low side side connected to the ground, and an input at one end. A voltage is applied and the other end is connected to the connection points of the first and second switching elements. The boost inductor is connected to the high-side end of the first arm and the ground. A transformer having an input winding and an output winding, one end of the input winding connected to a connection point of the second and third switching elements, and a voltage half of the voltage across the booster capacitor. A bias circuit that generates and supplies the voltage to the other end of the input winding, a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate a DC output voltage, and the first switching cycle. A switching control circuit that turns on / off the first to third switching elements and controls the output voltage is provided.
The first to third operation modes are set in the switching control circuit, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, and the third switching is performed. It is an operation mode in which the element is turned on, and the second operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned off, and the third switching element is turned on. The third operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off, and the switching control circuit is one. It is a switching power supply device that controls the output voltage by sequentially executing the first to third operation modes in a switching cycle and adjusting the time ratio of each operation mode.

In this case, when the switching control circuit starts the first operation mode, the first switching element is turned off, and then the voltage across the third switching element drops below a certain level. When the control to turn on the third switching element is performed and the second operation mode is started, after the second switching element is turned off, the voltage across the first switching element drops below a certain level. When the control to turn on the first switching element is performed at the timing and the third operation mode is started, after the third switching element is turned off, the voltage across the second switching element is equal to or less than a certain value. It is preferable to control to turn on the second switching element at the timing when the value drops to.

A resonance capacitor and a resonance inductor for forming a sinusoidal waveform of the current passing through the transformer may be provided at a position in series with the input winding. Further, the input voltage is a full-wave rectification of a sine wave voltage, and the switching control circuit may be configured to perform control to improve the power factor by bringing the waveform of the input current closer to the waveform of the input voltage. ..

Further, the present invention is a circuit block composed of first, second and third switching elements connected in series in order , and one end of the third switching element which is an end on the low side side of the circuit block. A first arm whose portion is connected to the ground, an input voltage is applied to one end, and the other end is connected to the connection points of the first and second switching elements to form a first step-up inductor and the first arm. A circuit block consisting of a first step-up capacitor connected between an end on the high side side and the ground, and fourth, fifth, and sixth switching elements connected in series in order , the circuit. A second arm in which one end of the sixth switching element, which is the end on the low side side of the block , is connected to the ground, and the input voltage is applied to one end and the other end is the fourth and fifth switching. A second step-up inductor connected to the connection point of the element, a second step-up capacitor connected between the high-side end of the second arm and the ground, and an input winding and an output winding. The input winding is generated in the output winding and the transformer connected between the connection point of the second and third switching elements and the connection point of the fifth and sixth switching elements. A switching in which the output voltage is controlled by turning on / off the first to sixth switching elements in a predetermined switching cycle, including a rectifying / smoothing circuit that rectifies and smoothes the voltage to be generated to generate a DC output voltage. It is a control method of the power supply
The first to fourth operation modes are set, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, the third switching element is turned on, and the fourth. Is an operation mode in which the switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. In the second operation mode, the first switching element is turned on and the second switching element is turned on. This is an operation mode in which the switching element is turned off, the third switching element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. In the operation mode 3, the first switching element is turned on, the second switching element is turned on, the third switching element is turned off, the fourth switching element is turned off, and the fifth switching element is turned on. , The sixth operation mode is an operation mode in which the sixth switching element is turned on, and in the fourth operation mode, the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off. , The fourth switching element is turned on, the fifth switching element is turned off, and the sixth switching element is turned on. The first to fourth operation modes are set in one switching cycle. Is a control method of a switching power supply device that controls the output voltage by sequentially executing the above steps and adjusting the time ratio of each operation mode.

In this case, when the first operation mode is started, after the first and sixth switching elements are turned off, the voltage across the third and fifth switching elements drops below a certain level. When the third and fifth switching elements are turned on and the second operation mode is started, the voltage across the first switching element drops below a certain level after the second switching element is turned off. When the first switching element is turned on at the timing and the third operation mode is started, after the third and fourth switching elements are turned off, the voltage across the second and sixth switching elements The second and sixth switching elements are turned on at the timing when the voltage drops below a certain level, and when the fourth operation mode is started, the fifth switching element is turned off, and then the fourth switching element is started. It is preferable to turn on the fourth switching element at the timing when the voltage across the above drops below a certain level. Further, the second boosting capacitor may be used in common with the first boosting capacitor to operate.

Further, the present invention has a first arm having first, second and third switching elements connected in series from the high side side, and an end portion on the low side side connected to the ground, and an input at one end. A booster is applied and the other end is connected to the connection points of the first and second switching elements, and the booster is connected between the high-side end of the first arm and the ground. A transformer having a capacitor, an input winding and an output winding, one end of the input winding connected to a connection point of the second and third switching elements, and a voltage of half the voltage across the booster capacitor. A bias circuit that generates and supplies to the other end of the input winding, and a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate a DC output voltage, with a predetermined switching cycle. A control method for a switching power supply device in which the output voltage is controlled by turning on / off the first to third switching elements.
The first to third operation modes are set, and the first operation mode is an operation mode in which the first switching element is turned off, the second switching element is turned on, and the third switching element is turned on. The second operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned off, and the third switching element is turned on, and the third operation mode is Is an operation mode in which the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off, and the first to third operations are performed in one switching cycle. This is a control method of a switching power supply device that controls the output voltage by executing modes in order and adjusting the time ratio of each operation mode.

In this case, when the first operation mode is started, after the first switching element is turned off, the third switching element is turned on at the timing when the voltage across the third switching element drops below a certain level. When the second operation mode is turned on and the second operation mode is started, the first switching element is turned on at the timing when the voltage across the first switching element drops below a certain level after the second switching element is turned off. When the third operation mode is turned on and the third operation mode is started, the second switching element is turned on at the timing when the voltage across the second switching element drops below a certain level after the third switching element is turned off. It is preferable to turn it on.

The switching power supply device and its control method of the present invention can perform the operation of boosting the input voltage and further transforming the boosted voltage to generate an output voltage with a small number of switching elements. Moreover, since the variable width of the boost ratio can be widened, it becomes easy to design a power supply device having a wide input voltage range.

In addition, all switching elements can be easily soft-switched (for example, zero-volt switching), and the efficiency and noise of the power supply device can be reduced.

It is a circuit diagram which shows the 1st Embodiment of the switching power supply device of this invention. It is a time chart which shows the operation at the steady state of the switching power supply apparatus of 1st Embodiment. It is the figure (a) which shows the equivalent circuit of a switching element, the figure (b) which shows the equivalent circuit of a rectifying element, and the figure (c) which shows the equivalent circuit of a transformer. It is an equivalent circuit which shows the operation of the period T11 of the switching power supply device of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T12 of the switching power supply device of the first embodiment. It is an equivalent circuit which shows the operation of the period T13 of the switching power supply apparatus of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T14 of the switching power supply device of the first embodiment. It is an equivalent circuit which shows the operation of the period T15 of the switching power supply apparatus of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T16 of the switching power supply device of the first embodiment. It is an equivalent circuit which shows the operation of the period T21 of the switching power supply device of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T22 of the switching power supply apparatus of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T23 of the switching power supply device of the first embodiment. It is an equivalent circuit which shows the operation of the period T24 of the switching power supply apparatus of 1st Embodiment. It is an equivalent circuit which shows the operation of the period T25 of the switching power supply device of the first embodiment. It is an equivalent circuit which shows the operation of the period T26 of the switching power supply device of the first embodiment. It is a circuit diagram which shows one modification of the switching power supply device of 1st Embodiment. It is a circuit diagram which shows the 2nd Embodiment of the switching power supply device of this invention. It is a time chart which shows the operation at the steady state of the switching power supply apparatus of the 2nd Embodiment. It is an equivalent circuit which shows the operation of the period T11 of the switching power supply device of the 2nd Embodiment. It is an equivalent circuit which shows the operation of the period T21 of the switching power supply device of the second embodiment. It is a circuit diagram which shows one modification of the switching power supply device of 2nd Embodiment. It is a circuit diagram which shows the 3rd Embodiment of the switching power supply device of this invention. It is a time chart which shows the operation at the steady state of the switching power supply apparatus of 3rd Embodiment. It is an equivalent circuit which shows the operation of the period T51 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T52 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T53 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T54 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T55 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T56 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T61 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T62 of the switching power supply device of the third embodiment. It is an equivalent circuit which shows the operation of the period T63 of the switching power supply device of the third embodiment. It is a circuit diagram which shows one modification of the switching power supply apparatus of 3rd Embodiment. It is a circuit diagram which shows the 4th Embodiment of the switching power supply device of this invention. It is a time chart which shows the operation at the steady state of the switching power supply apparatus of 4th Embodiment. It is an equivalent circuit which shows the operation of the period T51 of the switching power supply device of 4th Embodiment. It is an equivalent circuit which shows the operation of the period T61 of the switching power supply device of 4th Embodiment. It is a circuit diagram which shows one modification of the switching power supply device of 4th Embodiment.

Hereinafter, the first embodiment of the switching power supply device of the present invention and the control method thereof will be described with reference to FIGS. 1 to 16. The switching power supply device 10 of this embodiment is a device that outputs a constant output voltage Vo, generates a boosted voltage Vc from a DC input voltage Vi, and further transforms the boosted voltage Vc to generate an output voltage Vo. To do. The main circuit configuration is a unique configuration that combines a boost chopper (2 units) and a current resonance type full bridge converter (1 unit). Further, the control method of this embodiment is executed by a switching control circuit (not shown) of the switching power supply device 10, and the switching control circuit may be appropriately configured by a known analog circuit, a digital processing IC, or a circuit combining them. it can.

As shown in FIG. 1, the switching power supply device 10 includes first and second arms 14 and 16 composed of a plurality of switching elements 12. The first arm 14 is a circuit block composed of first, second, and third switching elements 12 (1) to 12 (3) connected in series in order, and is a low-side end of the circuit block . One end of the switching element 12 (3) of No. 3 is connected to the ground 18. The second arm 16 is a circuit block composed of fourth, fifth, and sixth switching elements 12 (4) to 12 (6) connected in series in order, and is a low-side end of the circuit block . One end of the switching element 12 (6) of No. 6 is connected to the ground 18. As the switching elements 12 (1) to 12 (6), for example, an N-channel MOS type FET is suitable.

One end of the first step-up inductor 20 (1) is connected to the connection points of the first and second switching elements 12 (1) and 12 (2). The other end of the first step-up inductor 20 (1) is a terminal to which an input voltage Vi is applied from the input power supply 22, and an input capacitor 24 is connected between this terminal and the ground 18. Similarly, one end of the second step-up inductor 20 (2) is connected to the connection points of the fourth and fifth switching elements 12 (4) and 12 (5). The other end of the second step-up inductor 20 (2) is a terminal to which the input voltage Vi is applied from the input power supply 22, and is connected to one end of the input capacitor 24. The first and second boost inductors 20 (1) and 20 (2) are the same component.

A first step-up capacitor 26 is connected between the high-side end of the first arm 14 and the ground 18. A second step-up capacitor is also connected between the high-side end of the second arm 14 and the ground 18, but here, the second step-up capacitor is also used by the first step-up capacitor 26. ..

Transformers 32 that insulate input and output between the input winding 28 and the output winding 30 are connected to the first and second arms 14 and 16. Since the output winding 30 is used by drawing out the intermediate point, one side thereof is referred to as an output winding 30 (1) and the other side is referred to as an output winding 30 (2) with the intermediate point interposed therebetween. The dots attached to each winding in FIG. 1 indicate the polarity.

The input winding 28 is located between the connection points of the second and third switching elements 12 (2) and 12 (3) and the connection points of the fifth and sixth switching elements 12 (5) and 12 (6). The resonance capacitor 34 and the resonance inductor 36 are inserted at positions connected to the input winding 28 in series with the input winding 28. The resonance capacitor 34 and the resonance inductor 36 form a sinusoidal waveform of the current passing through the transformer 32, that is, the current flowing into the input winding 28 and flowing out from the output windings 30 (1) and 30 (2). To work. The resonance inductor 36 may utilize the leakage inductance inside the transformer 32.

A rectifying smoothing circuit 38 that rectifies and smoothes the voltage generated in the output windings 30 (1) and 30 (2) to generate a DC output voltage Vo is connected to the output windings 30 (1) and 30 (2). Has been done. The rectifying and smoothing circuit 38 is composed of a rectifying element 40 (1) connected to the output winding 30 (1), a rectifying element 40 (2) connected to the output winding 30 (2), and a smoothing capacitor 42. It is a center tap type rectifying and smoothing circuit, generates an output voltage Vo across the smoothing capacitor 42, and supplies an output voltage Vo and an output current Io toward the load 44. The rectifying elements 40 (1) and 40 (2) may be diodes, but here, in order to reduce the conduction loss, an N-channel MOS type FET having a small voltage drop during conduction is used.

The switching elements 12 (1) to 12 (6) and the rectifying elements 40 (1) and 40 (2) are driven by a switching control circuit (not shown). The switching control circuit turns the switching elements 12 (1) to 12 (6) and the rectifying elements 40 (1) and 40 (2) on and off at a predetermined switching cycle Tsw so that the output voltage Vo becomes a constant value. To control.

As shown in Table 1 below, the switching control circuit is set with the first to fourth operation modes. In the first operation mode, the first switching element 12 (1) is turned off, the second switching element 12 (2) is turned on, the third switching element 12 (3) is turned on, and the fourth switching element 12 ( This is an operation mode in which 4) is turned on, the fifth switching element 12 (5) is turned on, and the sixth switching element 12 (6) is turned off. In the second operation mode, the first switching element 12 (1) is turned on, the second switching element 12 (2) is turned off, the third switching element 12 (3) is turned on, and the fourth switching element 12 ( This is an operation mode in which 4) is turned on, the fifth switching element 12 (5) is turned on, and the sixth switching element 12 (6) is turned off. The third operation mode is that the first switching element 12 (1) is turned on, the second switching element 12 (2) is turned on, the third switching element 12 (3) is turned off, and the fourth switching element 12 ( This is an operation mode in which 4) is turned off, the fifth switching element 12 (5) is turned on, and the sixth switching element 12 (6) is turned on. Then, in the fourth operation mode, the first switching element 12 (1) is turned on, the second switching element 12 (2) is turned on, the third switching element 12 (3) is turned off, and the fourth switching element is turned on. This is an operation mode in which the 12 (4) is turned on, the fifth switching element 12 (5) is turned off, and the sixth switching element 12 (6) is turned on.

スイッチング制御回路は、１つのスイッチング周期Tswの中で、表１の第１から第４の動作モードを順番に実行し、これをスイッチング周期Tsw毎に繰り返す。

The switching control circuit sequentially executes the first to fourth operation modes in Table 1 in one switching cycle Tsw, and repeats this for each switching cycle Tsw.

Since this switching control circuit causes each of the switching elements 12 (1) to 12 (6) to perform zero-volt switching (ZVS), when each operation mode is started, the on / off timing is slightly shifted. Specifically, when starting the first operation mode, after turning off the first and sixth switching elements 12 (1) and 12 (6), the third and fifth switching elements 12 (3) ), 12 (5) is controlled to turn on the third and fifth switching elements 12 (3) and 12 (5) at the timing when the voltage across them drops below a certain level. When starting the second operation mode, after turning off the second switching element 12 (2), the first switching is performed at the timing when the voltage across the first switching element 12 (1) drops below a certain level. Control is performed to turn on the element 12 (1). When starting the third operation mode, after turning off the third and fourth switching elements 12 (3) and 12 (4), the second and sixth switching elements 12 (2) and 12 (6) are started. ), The second and sixth switching elements 12 (2) and 12 (6) are turned on at the timing when the voltage across the device drops below a certain level. Then, when the fourth operation mode is started, after the fifth switching element 12 (5) is turned off, the fourth operation mode is started at the timing when the voltage across the fourth switching element 12 (4) drops below a certain level. The switching element 12 (4) of the above is controlled to be turned on.

In addition, the on / off states of the rectifying elements 40 (1) and 40 (2) are also set for each operation mode, which will be described in detail later in the operation description.

FIG. 2 is a time chart showing the steady operation of the switching power supply device 10. Periods T11 to T26 are one switching cycle Tsw, periods T11 to T13 are the first operating mode, periods T14 to T16 are the second operating mode, periods T21 to T23 are the third operating mode, and periods T24 to T26. Is the period of the fourth operation mode. Within one switching period Tsw, the lengths of periods T11 to T13 (first operating mode) and periods T21 to T23 (third operating mode) are almost the same, and periods T14 to T16 (third operating mode). The length of the operation mode) and the length of the periods T24 to T26 (fourth operation mode) are almost the same.

Further, in FIG. 2, in order to make the operation waveform easier to see, the periods T11 and T12, the periods T14 and T15, the periods T21 and T22, and the periods T24 and T25 are drawn longer than they actually are. However, in reality, the periods T11 and T12 are transient short periods when the first operating mode is started, and the period T13 is substantially the period of the first operating mode. Similarly, periods T14 and T15 are transient short periods at the start of the second mode of operation, with period T16 being the period of the substantial second mode of operation. Similarly, periods T21 and T22 are transient short periods at the start of the third operating mode, with period T23 being the effective period of the third operating mode. Similarly, periods T24 and T25 are transient short periods at the start of the fourth operating mode, with period T26 being the effective period of the fourth operating mode.

Vg (1) to Vg (3) in FIG. 2 are waveforms of the voltage between each gate and source of the switching elements 12 (1) to 12 (3), and the source side is used as a reference potential. Vd (1) and Vd (3) are waveforms of the voltage between the drain and the source of the switching elements 12 (1) and 12 (3), and the source side is set as the reference potential. Further, I (20 (1)) is a current waveform of the first step-up inductor 20 (1), and the direction of outflow toward the first arm 14 is the positive direction.

Vg (4) to Vg (6) are waveforms of the voltage between each gate and source of the switching elements 12 (4) to 12 (6), and the source side is set as a reference potential. Vd (4) and Vd (6) are waveforms of the voltage between the drain and the source of the switching elements 12 (4) and 12 (6), and the source side is set as the reference potential. Further, I (20 (2)) is a current waveform of the second step-up inductor 20 (2), and the direction of outflow toward the second arm 16 is the positive direction.

V (28) is the voltage waveform of the input winding 28, and the side without dots is set as the reference potential. I (28) is a current waveform of the input winding 28, and the direction of inflow to the side with dots is the positive direction. I (40 (1)) and I (40 (2)) are the current waveforms of the rectifying elements 40 (1) and 40 (2), and the direction of outflow from the drain is the positive direction. Io is the waveform of the output current. Here, the load 44 is a constant current load or a constant resistance load, and the output current Io is the average value of the currents I (40 (1)) and I (40 (2)).

Next, the operation of the switching power supply device 10 will be described with reference to the equivalent circuits (FIGS. 4 to 15) of T11 to T26 for each period. In the equivalent circuit, as shown in FIG. 3A, the switching elements 12 (1) to 12 (6) are represented by switch symbols, and the parasitic capacitance between the drain and source and the parasitic capacitance between the drain and source are also included. It is described. Further, as shown in FIG. 3B, the rectifying elements 40 (1) and 40 (2) are represented by switch symbols.

Further, as shown in FIG. 3C, the transformer 32 is represented by an exciting inductance Lm and an ideal transformer 32a (input winding 28a, output winding 30 (1), 30 (2)). The waveform of the current I (28) shown in FIG. 2 is a combination of the current I (Lm) flowing through the exciting inductance Lm and the current I (28a) of the input winding 28a, and is the waveform of the current I (28). The part indicated by the broken line (triangular wave-shaped part) is the current I (Lm), and the part indicated by the hatching (arc-shaped part) is the current I (28a).

Further, in FIGS. 4 to 15, the upper equivalent circuit shows the operation of generating the boost voltage Vc from the input voltage Vi, and the lower equivalent circuit shows the operation of generating the output voltage Vo from the boost voltage Vc. .. The arrows in the figure are the main current flows, and in the actual circuit, the current written in the equivalent circuit in the upper row and the current written in the lower row are flowing at the same time.

Hereinafter, the operations of the periods T11 to T26 will be described in order. In the state immediately before the period T11, that is, the state of the period T26, the first switching element 12 (1) is on, the second switching element 12 (2) is on, and the third switching element 12 (3) is off. The fourth switching element 12 (4) is on, the fifth switching element 12 (5) is off, the sixth switching element 12 (6) is on, the rectifying element 40 (1) is on, and the rectifying element 40. (2) is off.

In the period T11, when the current I (40 (1)) of the rectifying element 40 (1) becomes zero, the first and sixth switching elements 12 (1) and 12 (6) turn off, and the rectifying element It starts when 40 (1) turns off. The on / off states of the other switching elements and rectifying elements are the same as in the previous period T26.

The turn-off timings of the first and sixth switching elements 12 (1) and 12 (6) do not have to be exactly the same. However, in order to reduce the fluctuation width of the potential of the transformer 32 with respect to the ground 18 and prevent unnecessary noise from being radiated, it is preferable that the turn-off timings coincide with each other.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 4, the switching elements 12 (1), 12 (3), 12 (5), 12 (6) and the rectifying element 40. Since (1) and 40 (2) are off, power transmission from the first step-up capacitor 26 to the load 44 is not performed, and the output current Io is supplied from the smoothing capacitor 42. During this period, the current indicated by the solid line arrow for charging the parasitic capacitances of the first and sixth switching elements 12 (1) and 12 (6) flows from the first step-up capacitor 26, and the voltages Vd (1) and Vd ( 6) rises toward + Vc, voltage Vd (3) and voltage Vd (5) fall toward zero, and voltage V (28) reverses from positive voltage to negative voltage.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 4, the second boost inductor 20 (2) releases energy, so that the current I (20 (2) )) Flows toward the first step-up capacitor 26. Since the first switching element 12 (1) of the first step-up inductor 20 (1) is off, the current I (20 (1)) that emits energy does not flow to the first step-up capacitor 26. The period T11 ends at the timing when the voltages Vd (3) and Vd (5) cross zero, and the period T12 shifts to the next period T12.

In the period T12, the parasitic diodes of the third and fifth switching elements 12 (3) and 12 (5) start to conduct at the timing when the voltage Vd (3) and the voltage Vd (5) cross zero, and further, the rectifying element 40 It starts when (2) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T11.

In the operation of generating the output voltage Vo from the boost voltage Vc, as shown in the equivalent circuit in the lower part of FIG. 5, a counter electromotive force is generated in the exciting inductance Lm to keep the current flowing at the end of the period T11. Then, the current I (Lm) indicated by the solid line arrow flows to conduct the parasitic diodes of the third and fifth switching elements 12 (3) and 12 (5), and as a result, both ends of the input winding 28a and the exciting inductance Lm. -Vc is applied to. Since the rectifying element 40 (2) is on, the resonance current from the resonance capacitor 34 to the resonance inductor 36 flows in the path indicated by the broken line arrow. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (2)) in FIG.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 5, the second boost inductor 20 (2) releases energy, so that the current I (20 (2) )) Flows toward the first step-up capacitor 26. This is similar to period T11. On the other hand, in the first boost inductor 20 (1), an input voltage Vi is applied to both ends by conducting the parasitic diode of the third switching element 12 (3), and the current I (20 (1)) indicated by the solid line arrow. Flows and energy is stored. The period T12 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T13.

The period T13 starts when the third and fifth switching elements 12 (3) and 12 (5) are turned on. The on / off states of the other switching elements and rectifying elements are the same as in the previous period T12.

In the operation of generating the output voltage Vo from the boost voltage Vc, as shown in the equivalent circuit in the lower part of FIG. 6, -Vc is applied to both ends of the input winding 28a and the exciting inductance Lm, and from the first boost capacitor 26, The current I (Lm) indicated by the solid line arrow that excites the exciting inductance Lm flows. Further, since the rectifying element 40 (2) is on, the current indicated by the broken line arrow flows from the first boosting capacitor 26, and power is transmitted from the first boosting capacitor 26 to the load 44. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (2)) in FIG.

The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 6, and the same operation is continued during the period T12 (FIG. 5). However, in the waveform of the current I (20 (1)) in FIG. 2, the direction of the current I (20 (1)) is reversed from the negative direction to the positive direction almost at the same time when the period T13 starts. In the equivalent circuit in the upper part of FIG. 6, the direction of the solid line arrow is reversed. The timing at which the direction of the current I (20 (1)) is reversed depends on the setting of the L value of the first boost inductor 20 (1).

Another characteristic of period T13 is that the turn-on of the third and fifth switching elements 12 (3) and 12 (5) is when the voltages across the ends Vd (3) and Vd (5) are almost zero volts (parasitic diode). It is done when it is conducting). By this ZVS operation, the switching loss of the third and fifth switching elements 12 (3) and 12 (5) becomes very small, and the generation of switching noise is also significantly suppressed. The timing at which the period T13 ends is determined by the switching control circuit so that the output voltage Vo becomes a constant value, and the period shifts to the next period T14.

The period T14 starts when the second switching element 12 (2) turns off. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T13.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 7, and the same operation as in the period T13 (FIG. 6) is continued.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 7, the second boost inductor 20 (2) releases energy, so that the current I (20 (2) )) Flows toward the first step-up capacitor 26. This is similar to period T13. On the other hand, in the first step-up inductor 20 (1), since the second switching element 12 (2) is off, energy storage is stopped and the current I (20 (1)) indicated by the solid arrow that releases energy flows. .. Then, the parasitic capacitance of the second switching element 12 (2) is charged, the voltage Vd (2) rises toward + Vc, and the voltage Vd (1) falls toward zero. The period T14 ends at the timing when the voltage Vd (1) crosses zero, and shifts to the next period T15.

The period T15 starts when the parasitic diode of the first switching element 12 (1) starts to conduct at the timing when the voltage Vd (1) crosses zero. The on / off state of each switching element and rectifying element is the same as that of the previous period T14.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 8, and the same operation as in the period T14 (FIG. 7) is continued. However, in the waveform of the current I (Lm) in FIG. 2, the direction of the current I (Lm) is reversed from the positive direction to the negative direction in the middle of the period T15. Therefore, in the equivalent circuit in the lower part of FIG. The direction of the solid line arrow is the direction after reversal. The timing at which the direction of the current I (Lm) is reversed depends on the setting of the exciting inductance Lm.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 8, since the second boost inductor 20 (2) releases energy, the current I (20 (2) )) Flows toward the first step-up capacitor 26. This is similar to period T14. However, in the waveform of the current I (20 (2)) in FIG. 2, the direction of the current is reversed from the positive direction to the negative direction in the middle of the period T15. Therefore, in the equivalent circuit in the upper part of FIG. The direction of the arrow is the direction after reversal. On the other hand, in the first step-up inductor 20 (1), since the parasitic diode of the first switching element 12 (1) conducts, the path of the current I (20 (1)) that releases energy is as shown by the solid line arrow. It changes and flows toward the first step-up capacitor 26. The period T15 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T16.

The period T16 starts when the first switching element 12 (1) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T15.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 9, and the same operation as in the period T15 (FIG. 8) is continued. The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 9, and the same operation as in the period T15 (FIG. 8) is continued.

Another characteristic of the period T16 is that the turn-on of the first switching element 12 (1) is performed when the voltage Vd (1) across the ends is almost zero volt (when the parasitic diode is conducting). .. By this ZVS operation, the switching loss of the first switching element 12 (1) becomes very small, and the generation of switching noise is also significantly suppressed. The period T16 ends at the timing when the current I (40 (2)) of the rectifying element 40 (2) becomes zero, and shifts to the next period T21.

In the period T21, when the current I (40 (2)) of the rectifying element 40 (2) becomes zero, the third and fourth switching elements 12 (3) and 12 (4) turn off, and the rectifying element It starts when 40 (2) turns off. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T16.

The turn-off timings of the third and fourth switching elements 12 (3) and 12 (4) do not have to be exactly the same. However, in order to reduce the fluctuation width of the potential of the transformer 32 with respect to the ground 18 and prevent unnecessary noise from being radiated, it is preferable that the turn-off timings coincide with each other.

As shown in the equivalent circuit in the lower part of FIG. 10, the operation of generating the output voltage Vo from the boosted voltage Vc is as follows: the switching elements 12 (2), 12 (3), 12 (4), 12 (6) and the rectifying element 40. Since (1) and 40 (2) are off, power transmission from the first step-up capacitor 26 to the load 44 is not performed, and the output current Io is supplied from the smoothing capacitor 42. During this period, the current indicated by the solid line arrow for charging the parasitic capacitances of the third and fourth switching elements 12 (3) and 12 (4) flows from the first step-up capacitor 26, and the voltages Vd (3) and Vd ( 4) rises toward + Vc, voltage Vd (2) and voltage Vd (6) fall toward zero, and voltage V (28) reverses from negative voltage to positive voltage.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 10, since the first boost inductor 20 (1) releases energy, the current I (20 (1) )) Flows toward the first step-up capacitor 26. In the second step-up inductor 20 (2), since the fourth switching element 12 (4) is off, the current I (20 (2)) that emits energy does not flow through the first step-up capacitor 26. The period T21 ends at the timing when the voltages Vd (2) and Vd (6) cross zero, and shifts to the next period T22.

In the period T22, the parasitic diodes of the second and sixth switching elements 12 (2) and 12 (6) start to conduct at the timing when the voltage Vd (2) and the voltage Vd (6) cross zero, and further, the rectifying element 40 It starts when (1) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T21.

In the operation of generating the output voltage Vo from the boost voltage Vc, as shown in the equivalent circuit in the lower part of FIG. 11, a counter electromotive force is generated in the exciting inductance Lm to keep the current flowing at the end of the period T21. Then, the current I (Lm) indicated by the solid line arrow flows to conduct the parasitic diodes of the second and sixth switching elements 12 (2) and 12 (6), and as a result, both ends of the input winding 28a and the exciting inductance Lm. + Vc is applied to. Since the rectifying element 40 (1) is on, the resonance current from the resonance capacitor 34 to the resonance inductor 36 flows in the path indicated by the broken line arrow. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (1)) in FIG.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 11, the first boost inductor 20 (1) releases energy, so that the current I (20 (1) )) Flows toward the first step-up capacitor 26. This is similar to period T21. On the other hand, in the second boost inductor 20 (2), the input voltage Vi is applied to both ends by conducting the parasitic diode of the sixth switching element 12 (6), and the current I (20 (2)) indicated by the broken line arrow. Flows and energy is stored. The period T22 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T23.

The period T23 starts when the second and sixth switching elements 12 (2) and 12 (6) are turned on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T22.

In the operation of generating the output voltage Vo from the boost voltage Vc, + Vc is applied to both ends of the input winding 28a and the exciting inductance Lm as shown in the equivalent circuit in the lower part of FIG. 12, and from the first boost capacitor 26, The current I (Lm) indicated by the solid line arrow that excites the exciting inductance Lm flows. Further, since the rectifying element 40 (1) is on, the current indicated by the broken line arrow flows from the first boosting capacitor 26, and power is transmitted from the first boosting capacitor 26 to the load 44. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (1)) in FIG.

The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 12, and the same operation is continued during the period T22 (FIG. 11). However, in the waveform of the current I (20 (2)) in FIG. 2, the direction of the current I (20 (2)) is reversed from the negative direction to the positive direction almost at the same time as the period T23 starts. , In the upper equivalent circuit of FIG. 12, the direction of the broken line arrow is reversed. The timing at which the direction of the current I (20 (2)) is reversed depends on the setting of the L value of the second boost inductor 20 (2).

Another characteristic of the period T23 is that the turn-on of the second and sixth switching elements 12 (2) and 12 (6) is when the voltages across the ends Vd (2) and Vd (6) are almost zero volts (parasitic diode). It is done when it is conducting). By this ZVS operation, the switching loss of the second and sixth switching elements 12 (2) and 12 (6) becomes very small, and the generation of switching noise is also significantly suppressed. The timing at which the period T23 ends is determined by the switching control circuit so that the output voltage Vo becomes a constant value, and the period shifts to the next period T24.

The period T24 starts when the fifth switching element 12 (5) turns off. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T23.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 13, and the same operation as in the period T23 (FIG. 12) is continued.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 13, the first boost inductor 20 (1) releases energy, so that the current I (20 (1) )) Flows toward the first step-up capacitor 26. This is similar to period T23. On the other hand, in the second boost inductor 20 (2), since the fifth switching element 12 (5) is off, energy storage is stopped and the current I (20 (2)) indicated by the broken line arrow that releases energy flows. .. Then, the parasitic capacitance of the fifth switching element 12 (5) is charged, the voltage Vd (5) rises toward + Vc, and the voltage Vd (4) falls toward zero. The period T24 ends at the timing when the voltage Vd (4) crosses zero, and shifts to the next period T25.

The period T25 starts when the parasitic diode of the fourth switching element 12 (4) starts to conduct at the timing when the voltage Vd (4) crosses zero. The on / off state of each switching element and rectifying element is the same as that of the previous period T24.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 14, and the same operation as in the period T24 (FIG. 13) is continued. However, in the waveform of the current I (Lm) in FIG. 2, the direction of the current I (Lm) is reversed from the negative direction to the positive direction in the middle of the period T25. Therefore, in the equivalent circuit in the lower part of FIG. The direction of the solid line arrow is the direction after reversal. The timing at which the direction of the current I (Lm) is reversed depends on the setting of the exciting inductance Lm.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 14, the first boost inductor 20 (1) releases energy, so that the current I (20 (1) )) Flows toward the first step-up capacitor 26. This is similar to period T24. However, in the waveform of the current I (20 (1)) in FIG. 2, the direction of the current is reversed from the positive direction to the negative direction in the middle of the period T25, so that the equivalent circuit in the upper part of FIG. The direction of the arrow is the direction after reversal. On the other hand, in the second step-up inductor 20 (2), since the parasitic diode of the fourth switching element 12 (4) conducts, the path of the current I (20 (2)) that releases energy is as shown by the broken line arrow. It changes and flows toward the first step-up capacitor 26. The period T25 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T26.

The period T26 starts when the fourth switching element 12 (4) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T25.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 15, and the same operation as in the period T25 (FIG. 14) is continued. The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 15, and the same operation as in the period T25 (FIG. 14) is continued.

Another characteristic of the period T26 is that the turn-on of the fourth switching element 12 (4) is performed when the voltage across Vd (4) is almost zero volt (when the parasitic diode is conducting). .. By this ZVS operation, the switching loss of the fourth switching element 12 (4) becomes very small, and the generation of switching noise is also significantly suppressed. The period T26 ends at the timing when the current I (40 (1)) of the rectifying element 40 (1) becomes zero, and shifts to the next period T11.

As described above, the switching power supply device 10 has a first operation mode (period T11 to T13), a second operation mode (period T14 to T16), and a third operation mode (period) in one switching cycle Tsw. T21 to T23) and the fourth operation mode (periods T24 to T26) are executed in order, and this is repeated for each switching cycle Tsw.

Next, an example of the output voltage Vo control method performed by the switching control circuit will be described. Here, for the sake of simplicity, the length of each period is described as "T13 >> T11, T12", "T16 >> T14, T15", "T23 >> T21, T22", "T26 >> T24, T25". Assuming that, the states of the first and second step-up inductors 20 (1) and 20 (2) and the states of the input winding 28 in each operation mode can be arranged as shown in Table 2. The length of each fixed period is T13 ≒ T23 and T16 ≒ T26.

From the changes in the states of the first and second step-up inductors 20 (1) and 20 (2) shown in Table 2, the step-up ratio Vc / Vi increases as the time ratios T13 / Tsw and T23 / Tsw increase. It can be seen that the lower the value, the lower the value. This is the same principle as a normal boost chopper. Further, from the change in the state of the input winding 28, it can be seen that the transformation ratio Vo / Vc is fixed to be substantially constant. This is the same principle as a normal resonant full bridge converter.

Therefore, in the switching control circuit, for example, when the input voltage Vi is fixed and the output current Io increases, the switching cycle Tsw is lengthened to adjust the resonance condition so that the boost ratio Vc / Vi does not change. In addition, the periods T13 and T23 are lengthened by the same ratio as the switching period Tsw. As a result, the output voltage Vo can be controlled to a constant value.

In addition, for example, when the input voltage Vi becomes high while the output current Io is fixed, the boost ratio Vc / Vi is lowered by the amount that the input voltage Vi becomes high while keeping the switching cycle Tsw constant. , Shorten the periods T13 and T23 and lengthen the periods T16 and T26. As a result, the output voltage Vo can be controlled to a constant value.

As described above, according to the switching power supply device 10 and its control method, substantially the same function can be realized with a smaller number of switching elements than the DC power supply device of Patent Document 1 (FIG. 2). Further, all the switching elements 12 (1) to 12 (6) can be easily operated in ZVS, and high efficiency and low noise can be achieved.

Further, the switching power supply device 10 has one more switching element than the converter of Patent Document 2, but is interleaved (operation in which the currents I (20 (1)) and I (20 (2)) are out of phase). As a result, the ripple current of the first boosting capacitor 26 becomes smaller, and the first boosting capacitor 26 can be miniaturized. Further, the step-up ratio Vc / Vi can be adjusted regardless of the transformation ratio Vo / Vc, and the step-up ratio Vc / Vi can be increased while keeping the transformer utilization efficiency high. Therefore, the variable width of the boost ratio Vc / Vi can be widened without significantly reducing the power loss of the power supply device, and it is easy to apply to the power supply device having a wide range of the input voltage Vi.

In addition, the switching power supply device 10 can be provided with a power factor improving function by changing a part of the configuration like the switching power supply device 46 of the modified example. As shown in FIG. 16, the switching power supply device 46 is provided with a rectifier circuit 50 that rectifies the AC voltage Ve supplied from the input power supply 48 at the input stage of the switching power supply device 10, and is provided with the first and second rectifier circuits. The voltage (input voltage Vi) input to one end of the step-up inductors 20 (1) and 20 (2) is a waveform obtained by full-wave rectifying a sinusoidal wave. Then, a switching control circuit (not shown) controls the output voltage Vo to a constant value, and at the same time performs control to bring the waveform of the input current Ii closer to the waveform of the input voltage Vi to improve the power factor. According to the switching power supply device 46, the same effect as that of the switching power supply device 10 can be obtained, and a power supply device having a power factor improving function can be easily configured.

Next, a second embodiment of the switching power supply device and the control method thereof of the present invention will be described with reference to FIGS. 17 to 21. Here, the same configurations as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted. The switching power supply device 52 of this embodiment is a device that outputs a constant output voltage Vo, generates a boosted voltage Vc from a DC input voltage Vi, and further transforms the boosted voltage Vc to generate an output voltage Vo. To do. Generally speaking, the circuit configuration is a unique configuration in which a boost chopper (2 units) and a non-resonant type full bridge converter (1 unit) are combined. Further, the control method of this embodiment is executed by the switching control circuit of the switching power supply device 52.

The switching power supply 52 is similar in configuration to the switching power supply 10 described above, except that the resonance capacitor 34 and the resonance inductor 36 are omitted, and the rectifying smoothing circuit 38 has a smoothing inductor 54. An additional part that smoothes the voltage after rectification is a low-pass filter composed of a smoothing inductor 54 and a smoothing capacitor 42.

FIG. 18 is a time chart showing the steady operation of the switching power supply device 52. I (54) in FIG. 18 is a current waveform of the smoothing inductor 54, and the direction of outflow from one end on the smoothing capacitor 42 side is the positive direction. Here, too, the load 44 is a constant current load or a constant resistance load, and the output current Io is the average value of the currents I (54) that are continuous in a triangular wave shape.

Like the switching power supply device 10 described above, the switching power supply device 52 has four operation modes shown in Table 1, and the first operation mode (periods T11 to T13) and the first operation mode in one switching cycle Tsw. The second operation mode (period T14 to T16), the third operation mode (period T21 to T23), and the fourth operation mode (period T24 to T26) are executed in order, and this is repeated for each switching cycle Tsw.

Since the switching power supply 52 is a non-resonant converter, the current I (28) of the transformer 32 does not have a sinusoidal shape, but the ZVS operations of the switching elements 12 (1) to 12 (6) are performed in the same manner.

Further, the operations of the rectifying elements 40 (1) and 40 (2) are slightly different between the periods T11 and T21. In the period T11, as shown in the equivalent circuit in the lower part of FIG. 19, the rectifying elements 40 (1) and 40 (2) are turned on, and the current that the smoothing inductor 54 releases energy is the output winding 30 (1). ), 30 (2) (current of solid arrow). Similarly, even in the period T21, as shown in the equivalent circuit in the lower part of FIG. 21, the rectifying elements 40 (1) and 40 (2) are turned on, and the current that the smoothing inductor 54 releases energy is the output winding. It flows through 30 (1) and 30 (2) (current indicated by the solid arrow).

The states of the first and second step-up inductors 20 (1) and 20 (2) and the states of the input winding 28 in each operation mode are arranged as shown in Table 2 in the same manner as in the above switching power supply device 10. be able to. Therefore, in the case of the switching power supply device 52 as well, the boost ratio Vc / Vi becomes higher when the time ratios T13 / Tsw and T23 / Tsw are increased, and decreases when the time ratios T13 / Tsw are decreased. This is the same principle as a normal boost chopper. In addition, the transformation ratio Vo / Vc will be fixed almost constant. This is the same principle as a normal non-resonant full bridge converter.

Since the switching power supply 52 is a non-resonant type, the switching control circuit keeps the length of each period as it is when the output current Io increases while the input voltage Vi is fixed, so that the boost ratio Vc / Vi Do not change. This is because it is not necessary to adjust the resonance condition, and the output voltage Vo can be easily controlled. When the input voltage Vi increases while the output current Io is fixed, the boost ratio Vc / Vi is lowered by the increase in the input voltage Vi, as in the switching power supply device 10, so the period T13, T23 Is lengthened to shorten the periods T16 and T26. As a result, the output voltage Vo can be controlled to a constant value.

As described above, according to the switching power supply device 56 and its control method, the same effect as that of the switching power supply device 10 can be obtained, and the control by the switching control circuit becomes easy. Further, the switching power supply device 52 can be provided with a power factor improving function by changing a part of the configuration like the switching power supply device 56 of the modified example. As shown in FIG. 21, the switching power supply device 56 is provided with a rectifier circuit 50 that rectifies the AC voltage Ve supplied from the input power supply 48 at the input stage of the switching power supply device 52, and is the first and second. The voltage (input voltage Vi) input to one end of the step-up inductors 20 (1) and 20 (2) is characterized in that it becomes a waveform obtained by full-wave rectifying a sinusoidal wave. Then, a switching control circuit (not shown) controls the output voltage Vo to a constant value, and at the same time performs control to bring the waveform of the input current Ii closer to the waveform of the input voltage Vi to improve the power factor. According to the switching power supply device 56, the same effect as that of the switching power supply device 52 can be obtained, and a power supply device having a power factor improving function can be easily configured.

Next, a third embodiment of the switching power supply device and the control method thereof of the present invention will be described with reference to FIGS. 22 to 33. Here, the same configuration as that of the above embodiment will be described with the same reference numerals. The switching power supply device 58 of this embodiment is a device that outputs a constant output voltage Vo, generates a boosted voltage Vc from a DC input voltage Vi, and further transforms the boosted voltage Vc to generate an output voltage Vo. To do. Generally speaking, the circuit configuration is a unique configuration in which a boost chopper (1 unit) and a resonance type half-bridge converter (1 unit) are combined. Further, the control method of this embodiment is executed by the switching control circuit of the switching power supply device 58.

As shown in FIG. 22, the switching power supply device 58 includes a first arm 14 composed of a plurality of switching elements 12. The first arm 14 is composed of first, second and third switching elements 12 (1) to 12 (3) connected in series from the high side side, and the end portion on the low side side is connected to the ground 18. ing. As the switching elements 12 (1) to 12 (3), for example, an N-channel MOS type FET is suitable.

One end of the first step-up inductor 20 (1) is connected to the connection points of the first and second switching elements 12 (1) and 12 (2). The other end of the first step-up inductor 20 (1) is a terminal to which an input voltage Vi is applied from the input power supply 22, and an input capacitor 24 is connected between this terminal and the ground 18. Similarly, one end of the second step-up inductor 20 (2) is connected to the connection points of the fourth and fifth switching elements 12 (4) and 12 (5).

A first step-up capacitor 26 is connected between the high-side end of the first arm 14 and the ground 18. The first boosting capacitor 26 is obtained by connecting two boosting capacitors 26 (1) and 26 (2) having the same capacitance in series, and at the connection point, a voltage Vc / which is almost half of the boosting voltage Vc. It also operates as a bias circuit that generates 2.

A transformer 32 that insulates input and output between the input winding 28 and the output winding 30 is connected to the first arm 14. Since the output winding 30 is used by drawing out the intermediate point, one side thereof is referred to as an output winding 30 (1) and the other side is referred to as an output winding 30 (2) with the intermediate point interposed therebetween. The dots attached to each winding in FIG. 22 indicate the polarity.

The input winding 28 is connected between the connection points of the second and third switching elements 12 (2) and 12 (3) and the connection points of the step-up capacitors 26 (1) and 26 (2) to form dots. One end on the side not attached is biased by + Vc / 2 of the bias circuit. A resonance capacitor 34 and a resonance inductor 36 are inserted at positions in series with the input winding 28. The resonance capacitor 34 and the resonance inductor 36 function to make the current waveform flowing through the transformer 32 sinusoidal. The resonance inductor 36 may utilize the leakage inductance inside the transformer 32.

A rectifying smoothing circuit 38 that rectifies and smoothes the voltage generated in the output windings 30 (1) and 30 (2) to generate a DC output voltage Vo is connected to the output windings 30 (1) and 30 (2). Has been done. The rectifying / smoothing circuit 38 has the same configuration as the rectifying / smoothing circuit 38 of the switching power supply device 10.

The switching elements 12 (1) to 12 (3) and the rectifying elements 40 (1) and 40 (2) are driven by a switching control circuit (not shown). The switching control circuit turns the switching elements 12 (1) to 12 (3) and the rectifying elements 40 (1) and 40 (2) on and off at a predetermined switching cycle Tsw so that the output voltage Vo becomes a constant value. To control.

As shown in Table 3 below, the switching control circuit is set with the first to third operation modes. The first operation mode is an operation mode in which the first switching element 12 (1) is turned off, the second switching element 12 (2) is turned on, and the third switching element 12 (3) is turned on. The second operation mode is an operation mode in which the first switching element 12 (1) is turned on, the second switching element 12 (2) is turned off, and the third switching element 12 (3) is turned on. The third operation mode is an operation mode in which the first switching element 12 (1) is turned on, the second switching element 12 (2) is turned on, and the third switching element 12 (3) is turned off. ..

スイッチング制御回路は、１つのスイッチング周期Tswの中で、表３の前記第１から第３の動作モードを順番に実行し、これをスイッチング周期Tsw毎に繰り返す。

The switching control circuit sequentially executes the first to third operation modes in Table 3 in one switching cycle Tsw, and repeats this for each switching cycle Tsw.

Since this switching control circuit causes each of the switching elements 12 (1) to 12 (3) to perform zero-volt switching (ZVS), when each operation mode is started, the on / off timing is slightly shifted. Specifically, when the first operation mode is started, the timing at which the voltage across the third switching element 12 (3) drops below a certain level after the first switching element 12 (1) is turned off. Controls to turn on the third switching element 12 (3). When starting the second operation mode, after turning off the second switching element 12 (2), the first switching is performed at the timing when the voltage across the first switching element 12 (1) drops below a certain level. Control is performed to turn on the element 12 (1). Then, when starting the third operation mode, after turning off the third switching element 12 (3), the second operation mode is performed at the timing when the voltage across the second switching element 12 (2) drops below a certain level. The switching element 12 (2) of the above is controlled to be turned on.

In addition, the on / off states of the rectifying elements 40 (1) and 40 (2) are also set for each operation mode, which will be described in detail later in the operation description.

FIG. 23 is a time chart showing the steady operation of the switching power supply device 58. The periods T51 to T63 are one switching cycle Tsw, the periods T51 to T53 are the first operation mode, the periods T54 to T56 are the second operation modes, and the periods T61 to T63 are the periods of the third operation mode. Within one switching cycle Tsw, the total length of periods T51 to T53 (first operating mode) and periods T54 to T56 (second operating mode) and the length of periods T61 to T63 (third operating mode) Is almost the same.

Further, in FIG. 23, the periods T51 and T52, the periods T54 and T55, and the periods T61 and T62 are drawn longer than they actually are in order to make the operation waveform easier to see. However, in reality, the periods T51 and T52 are transient short periods when the first operating mode is started, and the period T53 is substantially the period of the first operating mode. Similarly, periods T54 and T55 are transient short periods when the second mode of operation is initiated, with period T56 being the period of the substantial second mode of operation. Similarly, periods T61 and T62 are transient short periods at the start of the third mode of operation, with period T63 being the period of the substantial third mode of operation.

Vg (1) to Vg (3) in FIG. 23 are waveforms of the voltage between each gate and source of the switching elements 12 (1) to 12 (3), and the source side is used as a reference potential. Further, I (20 (1)) is a current waveform of the first step-up inductor 20 (1), and the direction of outflow toward the first arm 14 is the positive direction. V (28) is the voltage waveform of the input winding 28, and the side without dots is set as the reference potential. I (28) is a current waveform of the input winding 28, and the direction of inflow to the side with dots is the positive direction. I (40 (1)) and I (40 (2)) are the current waveforms of the rectifying elements 40 (1) and 40 (2), and the direction of outflow from the drain is the positive direction. Io is the waveform of the output current. Here, the load 44 is a constant current load or a constant resistance load, and the output current Io is the average value of the currents I (40 (1)) and I (40 (2)).

Next, the operation of the switching power supply device 58 will be described with reference to the equivalent circuits (FIGS. 24 to 32) of T51 to T63 for each period. In the equivalent circuit, as shown in FIG. 3A, the switching elements 12 (1) to 12 (6) are represented by switch symbols, and the parasitic capacitance between the drain and source and the parasitic capacitance between the drain and source are also included. It is described. Further, as shown in FIG. 3B, the rectifying elements 40 (1) and 40 (2) are represented by switch symbols.

Further, as shown in FIG. 3C, the transformer 32 is represented by an exciting inductance Lm and an ideal transformer 32a (input winding 28a, output winding 30 (1), 30 (2)). The waveform of the current I (28) shown in FIG. 23 is a combination of the current I (Lm) flowing through the exciting inductance Lm and the current I (28a) of the input winding 28a, and is the waveform of the current I (28). The part indicated by the broken line (triangular wave-shaped part) is the current I (Lm), and the part indicated by the hatching (arc-shaped part) is the current I (28a).

Further, in FIGS. 24 to 32, the upper equivalent circuit shows an operation of generating a boost voltage Vc from the input voltage Vi, and the lower equivalent circuit shows an operation of generating an output voltage Vo from the boost voltage Vc. .. The arrows in the figure are the main current flows, and in the actual circuit, the current written in the equivalent circuit in the upper row and the current written in the lower row are flowing at the same time.

Hereinafter, the operations of the periods T51 to T63 will be described in order. In the state immediately before the period T51, that is, the state of the period T63, the first switching element 12 (1) is on, the second switching element 12 (2) is on, and the third switching element 12 (3) is off. Yes, the rectifying element 40 (1) is on and the rectifying element 40 (2) is off.

In the period T51, the first switching element 12 (1) is turned off and the rectifying element 40 (1) is turned off at the timing when the current I (40 (1)) of the rectifying element 40 (1) becomes zero. Start with. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T63.

In the operation of generating the output voltage Vo from the boosted voltage Vc, the switching elements 12 (1) and 12 (3) and the rectifying elements 40 (1) and 40 (2) are turned off, as shown in the equivalent circuit in the lower part of FIG. Therefore, the power is not transmitted from the step-up capacitors 26 (1) and 26 (2) to the load 44, and the output current Io is supplied from the smoothing capacitor 42. During this period, the current indicated by the solid line arrow that charges the parasitic capacitance of the first switching element 12 (1) flows from the step-up capacitor 26 (1), the voltage Vd (1) rises toward + Vc, and the voltage Vd. (3) drops toward zero, and the voltage V (28) reverses from positive voltage to negative voltage.

The operation of generating the boost voltage Vc from the input voltage Vi stops. That is, as shown in the equivalent circuit in the upper part of FIG. 24, the first boost inductor 20 (1) passes the current I (20 (1)) that releases energy, but the first switching element 12 (1) passes through it. Since it is off, it does not flow to the step-up capacitors 26 (1) and 26 (2). The period T51 ends at the timing when the voltage Vd (3) crosses zero, and shifts to the next period T52.

The period T52 starts when the parasitic diode of the third switching element 12 (3) starts to conduct at the timing when the voltage Vd (3) crosses zero, and the rectifying element 40 (2) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T51.

In the operation of generating the output voltage Vo from the boost voltage Vc, as shown in the equivalent circuit in the lower part of FIG. 25, a counter electromotive force is generated in the exciting inductance Lm to keep the current flowing at the end of the period T51. Then, the current I (Lm) indicated by the solid line arrow flows and the parasitic diode of the third switching element 12 (3) becomes conductive, and as a result, -Vc / 2 is applied to both ends of the input winding 28a and the exciting inductance Lm. To. Since the rectifying element 40 (2) is on, the resonance current from the resonance capacitor 34 to the resonance inductor 36 flows in the path indicated by the broken line arrow. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (2)) in FIG.

The operation of generating the boost voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 25, in which the parasitic diode of the third switching element 12 (3) is conducted to conduct the first boost inductor 20 (1). The input voltage Vi is applied to both ends of), and the current I (20 (1)) indicated by the solid line arrow flows to store energy. The period T52 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T53.

Period T53 begins with the third switching element 12 (3) turning on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T52.

In the operation of generating the output voltage Vo from the boost voltage Vc, -Vc / 2 is applied to both ends of the input winding 28a and the exciting inductance Lm as shown in the equivalent circuit in the lower part of FIG. 26, and the boost capacitor 26 (2) From, the current I (Lm) of the solid line arrow that excites the exciting inductance Lm flows. Further, since the rectifying element 40 (2) is on, the current indicated by the broken line arrow flows from the boosting capacitor 26 (2), and power is transmitted from the boosting capacitor 26 (2) to the load 44. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (2)) in FIG.

The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 26, and the same operation as in the period T52 (FIG. 25) is continued. However, in the waveform of the current I (20 (1)) in FIG. 23, the direction of the current I (20 (1)) is reversed from the negative direction to the positive direction almost at the same time when the period T53 starts. In the equivalent circuit in the upper part of FIG. 26, the direction of the solid line arrow is reversed. The timing at which the direction of the current I (20 (1)) is reversed depends on the setting of the L value of the first boost inductor 20 (1).

Another characteristic of period T53 is that the turn-on of the third switching element 12 (3) is performed when the voltage across Vd (3) is almost zero volt (when the parasitic diode is conducting). .. By this ZVS operation, the switching loss of the third switching element 12 (3) becomes very small, and the generation of switching noise is also significantly suppressed. The timing at which the period T53 ends is determined by the switching control circuit so that the output voltage Vo becomes a constant value, and the period shifts to the next period T54.

The period T54 starts when the second switching element 12 (2) turns off. The on / off states of the other switching elements and rectifying elements are the same as in the previous period T53. The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 27, and the same operation as in the period T53 (FIG. 26) is continued.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 27, since the second switching element 12 (2) is off, the energy to the first boost inductor 20 (1) is generated. Accumulation is stopped, and the current I (20 (1)) of the solid arrow that releases energy flows. Then, the parasitic capacitance of the second switching element 12 (2) is charged, the voltage Vd (2) rises toward + Vc, and the voltage Vd (1) falls toward zero. The period T54 ends at the timing when the voltage Vd (1) crosses zero, and shifts to the next period T55.

The period T55 starts when the parasitic diode of the first switching element 12 (1) starts to conduct at the timing when the voltage Vd (1) crosses zero. The on / off state of each switching element and rectifying element is the same as that of the previous period T54.

The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 28, and the same operation as in the period T54 (FIG. 27) is continued. However, in the waveform of the current I (Lm) in FIG. 23, the direction of the current I (Lm) is reversed from the positive direction to the negative direction in the middle of the period T55. Therefore, in the equivalent circuit in the lower part of FIG. The direction of the solid line arrow is the direction after reversal. The timing at which the direction of the current I (Lm) is reversed depends on the setting of the exciting inductance Lm.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 28, the parasitic diode of the first switching element 12 (1) conducts, so that the first boost inductor 20 (1) ) Changes the path of the current I (20 (1)) that releases energy as shown by the solid arrow, and flows toward the step-up capacitors 26 (1) and 26 (2). The period T55 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T56.

The period T56 starts when the first switching element 12 (1) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T55. The operation of generating the output voltage Vo from the boosted voltage Vc is as shown in the equivalent circuit in the lower part of FIG. 29, and the same operation as in the period T55 (FIG. 28) is continued. The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 29, and the same operation as in the period T55 (FIG. 28) is continued.

Another characteristic of the period T56 is that the turn-on of the first switching element 12 (1) is performed when the voltage Vd (1) across the ends is almost zero volt (when the parasitic diode is conducting). .. By this ZVS operation, the switching loss of the first switching element 12 (1) becomes very small, and the generation of switching noise is also significantly suppressed. The period T56 ends when the current I (40 (2)) of the rectifying element 40 (2) becomes zero, and the period T56 shifts to the next period T61.

In the period T61, when the current I (40 (2)) of the rectifying element 40 (2) becomes zero, the third switching element 12 (3) turns off and the rectifying element 40 (2) turns off. Start with. The on / off states of the other switching elements and rectifying elements are the same as in the previous period T56.

In the operation of generating the output voltage Vo from the boosted voltage Vc, the switching elements 12 (2) and 12 (3) and the rectifying elements 40 (1) and 40 (2) are turned off, as shown in the equivalent circuit in the lower part of FIG. Therefore, the power is not transmitted from the step-up capacitors 26 (1) and 26 (2) to the load 44, and the output current Io is supplied from the smoothing capacitor 42. During this period, the current indicated by the solid line arrow that charges the parasitic capacitance of the third switching element 12 (3) flows from the step-up capacitor 26 (2), the voltage Vd (3) rises toward + Vc, and the voltage Vd. (2) drops toward zero, and the voltage V (28) reverses from negative voltage to positive voltage.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 30, since the first boost inductor 20 (1) releases energy, the current I (20 (1) )) Flows toward the step-up capacitors 26 (1) and 26 (2). The period T61 ends at the timing when the voltage Vd (2) crosses zero, and shifts to the next period T62.

The period T62 starts when the parasitic diode of the second switching element 12 (2) starts to conduct at the timing when the voltage Vd (2) crosses zero, and the rectifying element 40 (1) turns on. The on / off state of the other switching elements and the rectifying element is the same as that of the previous period T61.

In the operation of generating the output voltage Vo from the boost voltage Vc, as shown in the equivalent circuit in the lower part of FIG. 31, a counter electromotive force is generated in the exciting inductance Lm to keep the current flowing at the end of the period T21. Then, the current I (Lm) indicated by the solid line arrow flows to conduct the parasitic diodes of the second and sixth switching elements 12 (2) and 12 (6), and as a result, both ends of the input winding 28a and the exciting inductance Lm. + Vc is applied to. Since the rectifying element 40 (1) is on, the resonance current from the resonance capacitor 34 to the resonance inductor 36 flows in the path indicated by the broken line arrow. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (1)) in FIG.

In the operation of generating the boost voltage Vc from the input voltage Vi, as shown in the equivalent circuit in the upper part of FIG. 11, the first boost inductor 20 (1) releases energy, so that the current I (20 (1) )) Flows toward the first step-up capacitor 26. This is similar to period T61. The period T62 is a very short time, and the operation of the switching control circuit promptly shifts to the next period T63.

The period T63 starts when the second switching element 12 (2) turns on. The on / off states of the other switching elements and rectifying elements are the same as in the previous period T62.

In the operation of generating the output voltage Vo from the boost voltage Vc, + Vc / 2 is applied to both ends of the input winding 28a and the exciting inductance Lm as shown in the equivalent circuit in the lower part of FIG. 32, and the boost capacitor 26 (1) From, the current I (Lm) of the solid line arrow that excites the exciting inductance Lm flows. The direction of this current I (Lm) reverses from the negative direction to the positive direction in the middle of the period T63. Further, since the rectifying element 40 (1) is on, the current indicated by the broken line arrow flows from the boosting capacitor 26 (1), and power is transmitted from the boosting capacitor 26 (1) to the load 44. The current indicated by the broken line arrow appears in the waveforms of the currents I (28a) and I (40 (1)) in FIG.

The operation of generating the boosted voltage Vc from the input voltage Vi is as shown in the equivalent circuit in the upper part of FIG. 32, and the same operation as in the period T62 (FIG. 31) is continued. The direction of this current I (Lm) reverses from the positive direction to the negative direction in the middle of the period T63.

Another characteristic of the period T63 is that the turn-on of the second switching element 12 (2) is performed when the voltage across Vd (2) is almost zero volt (when the parasitic diode is conducting). .. By this ZVS operation, the switching loss of the second switching element 12 (2) becomes very small, and the generation of switching noise is also significantly suppressed. The period T62 ends when the current I (40 (1)) of the rectifying element 40 (1) becomes zero, and shifts to the next period T51.

As described above, the switching power supply device 58 has a first operation mode (period T51 to T53), a second operation mode (period T54 to T56), and a third operation mode (period) in one switching cycle Tsw. T61 to T63) are executed in order, and this is repeated every switching cycle Tsw.

Next, an example of the output voltage Vo control method performed by the switching control circuit will be described. Here, for the sake of simplicity, assuming that the length of each period is "T53 >> T51, T52", "T56 >> T54, T55", and "T63 >> T61, T62", each operation mode The states of the first step-up inductor 20 (1) and the input winding 28 in the above can be arranged as shown in Table 3 above. The length of each fixed period is T53 + T56 ≒ T63.

From the change in the state of the first boost inductor 20 (1) shown in Table 3, it can be seen that the boost ratio Vc / Vi increases as the time ratio T53 / Tsw increases, and decreases as the time ratio T53 / Tsw decreases. This is the same principle as a normal boost chopper. Further, from the change in the state of the input winding 28, it can be seen that the transformation ratio Vo / Vc is fixed to be substantially constant. This is the same principle as a normal resonant half-bridge converter.

Therefore, in the switching control circuit, for example, when the input voltage Vi is fixed and the output current Io increases, the switching cycle Tsw is lengthened to adjust the resonance condition so that the boost ratio Vc / Vi does not change. In addition, the period T53 is lengthened by the same ratio as the switching period Tsw. As a result, the output voltage Vo can be controlled to a constant value.

In addition, for example, when the input voltage Vi becomes high while the output current Io is fixed, the boost ratio Vc / Vi is lowered by the amount that the input voltage Vi becomes high while keeping the switching cycle Tsw constant. , Shorten the period T53 and lengthen the periods T56 and T63. As a result, the output voltage Vo can be controlled to a constant value.

The switching power supply device 58 has a unique configuration in which a step-up chopper (1 unit) and a current resonance type half-bridge converter (1 unit) are combined, and the same effect as that of the switching power supply device 10 can be obtained. .. However, in the case of the switching power supply device 58, since the interleaving operation as in the switching power supply device 10 is not performed, the ripple currents of the step-up capacitors 26 (1) and 26 (2) become large as in the conventional DC power supply device.

Further, the switching power supply device 58 can be provided with a power factor improving function by changing a part of the configuration like the switching power supply device 60 of the modified example. As shown in FIG. 33, the switching power supply device 60 is provided with a rectifier circuit 50 that rectifies the AC voltage Ve supplied from the input power supply 48 at the input stage of the switching power supply device 58, and is a first step-up inductor. The voltage (input voltage Vi) input to one end of 20 (1) is characterized in that it becomes a waveform obtained by full-wave rectifying a sinusoidal wave. Then, a switching control circuit (not shown) controls the output voltage Vo to a constant value, and at the same time performs control to bring the waveform of the input current Ii closer to the waveform of the input voltage Vi to improve the power factor. According to the switching power supply device 60, the same effect as that of the switching power supply device 58 can be obtained, and a power supply device having a power factor improving function can be easily configured.

Next, a fourth embodiment of the switching power supply device of the present invention and the control method thereof will be described with reference to FIGS. 34 to 38. Here, the same configurations as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted. The switching power supply device 62 of this embodiment is a device that outputs a constant output voltage Vo, generates a boosted voltage Vc from a DC input voltage Vi, and further transforms the boosted voltage Vc to generate an output voltage Vo. To do. Generally speaking, the circuit configuration is a unique configuration in which a boost chopper (1 unit) and a non-resonant type half-bridge converter (1 unit) are combined. Further, the control method of this embodiment is executed by the switching control circuit of the switching power supply device 62.

The switching power supply device 62 is similar in configuration to the switching power supply device 58 described above, except that the resonance capacitor 34 and the resonance inductor 36 are omitted, and the rectifying smoothing circuit 38 has a smoothing inductor 54. An additional part that smoothes the voltage after rectification is a low-pass filter composed of a smoothing inductor 54 and a smoothing capacitor 42.

FIG. 35 is a time chart showing the steady operation of the switching power supply device 62. I (54) in FIG. 35 is a current waveform of the smoothing inductor 54, and the direction of outflow from one end on the smoothing capacitor 42 side is the positive direction. Here, too, the load 44 is a constant current load or a constant resistance load, and the output current Io is the average value of the currents I (54) that are continuous in a triangular wave shape.

Similar to the switching power supply device 58 described above, the switching power supply device 62 has the three operation modes shown in Table 3, and the first operation mode (periods T51 to T53) and the first operation mode in one switching cycle Tsw. The second operation mode (period T54 to T56) and the third operation mode (period T61 to T63) are executed in order, and this is repeated for each switching cycle Tsw.

Since the switching power supply device 62 is a non-resonant type converter, the current I (28) flowing through the transformer 32 does not have a sinusoidal shape, but the ZVS operations of the switching elements 12 (1) to 12 (6) are performed in the same manner.

Further, the operations of the rectifying elements 40 (1) and 40 (2) are slightly different between the periods T51 and T61. In the period T51, as shown in the equivalent circuit in the lower part of FIG. 36, the rectifying elements 40 (1) and 40 (2) are turned on, and the current that the smoothing inductor 54 releases energy is the output winding 30 (1). ), 30 (2) (current of solid arrow). Similarly, even in the period T61, as shown in the equivalent circuit in the lower part of FIG. 37, the rectifying elements 40 (1) and 40 (2) are turned on, and the current that the smoothing inductor 54 releases energy is the output winding. It flows through 30 (1) and 30 (2) (current indicated by the solid arrow).

The states of the first step-up inductor 20 (1) and the input winding 28 in each operation mode can be arranged as shown in Table 3 in the same manner as in the switching power supply device 58 described above. Therefore, in the case of the switching power supply device 62 as well, the boost ratio Vc / Vi increases as the time ratio T53 / Tsw increases, and decreases as the time ratio T53 / Tsw decreases. This is the same principle as a normal boost chopper. In addition, the transformation ratio Vo / Vc will be fixed almost constant. This is the same principle as a normal non-resonant half-bridge converter.

Since the switching power supply 62 is a non-resonant type, the switching control circuit keeps the length of each period as it is when the output current Io increases while the input voltage Vi is fixed, so that the boost ratio Vc / Vi Do not change. This is because it is not necessary to adjust the resonance condition, and the output voltage Vo can be easily controlled. When the input voltage Vi becomes high while the output current Io is fixed, the boost ratio Vc / Vi is lowered by the amount that the input voltage Vi is raised, so that the period T53 is lengthened as in the case of the switching power supply 58. Then shorten the periods T56 and T63. As a result, the output voltage Vo can be controlled to a constant value.

As described above, according to the switching power supply device 62 and its control method, the same effect as that of the switching power supply device 58 can be obtained, and the control by the switching control circuit becomes easy. Further, the switching power supply device 62 can be provided with a power factor improving function by changing a part of the configuration like the switching power supply device 64 of the modified example. As shown in FIG. 38, the switching power supply device 64 is provided with a rectifier circuit 50 that rectifies the AC voltage Ve supplied from the input power supply 48 at the input stage of the switching power supply device 58, and is provided with a first boost inductor 20. The characteristic is that the voltage (input voltage Vi) input to one end of (1) becomes a waveform obtained by full-wave rectifying a sinusoidal wave. Then, a switching control circuit (not shown) controls the output voltage Vo to a constant value, and at the same time performs control to bring the waveform of the input current Ii closer to the waveform of the input voltage Vi to improve the power factor. According to the switching power supply device 64, the same effect as that of the switching power supply device 58 can be obtained, and a power supply device having a power factor improving function can be easily configured.

The switching power supply device and its control method of the present invention are not limited to the above-described embodiment. For example, in the above embodiment, since the ZVS operation of each switching element is performed, the switching element is turned on after the parasitic diode of the target switching element is conducted. However, if the loss caused by the current flowing through the parasitic diode cannot be ignored, the turn-on may be performed shortly before the current starts flowing through the parasitic diode, that is, when the voltage across the circuit drops to a predetermined low value. Even if the configuration is changed to perform such a soft switching operation, the cross loss and switching noise of the switching element can be sufficiently reduced.

The switching power supply devices 10, 46, 52, and 56 described above are configured to perform interleave operation by using the second boosting capacitor as the first boosting capacitor 26, but the allowable value of the ripple current of the boosting capacitor is large. If it is large, the second boost capacitor may be provided separately from the first boost capacitor 26. In addition, the two step-up inductors 20 (1) and 20 (2) are magnetically coupled with an appropriate degree of coupling to obtain the waveform and ripple component magnitude of the currents I (20 (1)) and I (20 (2)). It may be possible to make fine adjustments.

The rectifying smoothing circuit 38 included in each embodiment is a so-called center tap type, but can be changed to a bridge type, a current doubler type, or another type. Further, various accessory circuits (for example, noise filter, inrush current suppression circuit, overcurrent protection circuit, etc.) may be attached as long as the operation of the object of the present invention is not hindered. Further, the switching control circuit may be configured by using any kind of hardware, for example, it may be configured in a dedicated IC, or it may be configured by combining digital processing and an analog circuit.

In addition, the above-mentioned output voltage control method (method of varying the length of each operation mode period) executed by each switching control circuit shows a preferable example in which the output voltage is controlled to a constant value in a steady state. Therefore, the output voltage may be controlled by a control method different from the above depending on the situation such as when the input is turned on, when the input voltage is suddenly changed, and when the output current is suddenly changed, as well as in the steady state.

10,46,52,56,58,60,62,64 Switching power supply 12 (1) to 12 (6) Switching element 14 1st arm 16 2nd arm 18 Ground 20 (1) 1st step-up inductor 20 ( 2) Second step-up inductor 26 First step-up capacitor 26 (1), 26 (2) Booster capacitor (first step-up capacitor)
28 Input winding 30 (30 (1), 30 (2)) Output winding 32 Transformer 34 Resonance capacitor 36 Resonance inductor 38 Rectifier smoothing circuit 40 (1), 40 (2) Rectifier element 42 Smoothing capacitor 54 Smoothing inductor
Ii input current
Io output current
Vc boost voltage
Vi input voltage
Vo output voltage
Tsw switching cycle

Claims (11)

A circuit block composed of first, second, and third switching elements connected in series in order , and one end of the third switching element, which is a low-side end of the circuit block , is connected to the ground. An input voltage is applied to one end of the first arm, and the other end is connected to the connection points of the first and second switching elements to connect the first step-up inductor and the high-side end of the first arm. A circuit block consisting of a first step-up capacitor connected between the ground and the ground, and fourth, fifth, and sixth switching elements connected in series in order , the low-side end of the circuit block. One end of the sixth switching element, which is a unit , is connected to the second arm connected to the ground, and the input voltage is applied to one end and the other end is connected to the connection point of the fourth and fifth switching elements. It has a second step-up inductor, a second step-up capacitor connected between the high-side end of the second arm and the ground, and an input winding and an output winding. A transformer whose windings are connected between the connection points of the second and third switching elements and the connection points of the fifth and sixth switching elements, and the voltage generated in the output windings are rectified and smoothed. A rectifying and smoothing circuit that generates a DC output voltage and a switching control circuit that controls the output voltage by turning on / off the first to sixth switching elements at a predetermined switching cycle are provided.
The first to fourth operation modes are set in the switching control circuit, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, and the third switching is performed. An operation mode in which the element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. The second operation mode is the first switching. The element is turned on, the second switching element is turned off, the third switching element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. The third operation mode is an operation mode, in which the first switching element is turned on, the second switching element is turned on, the third switching element is turned off, the fourth switching element is turned off, and the like. It is an operation mode in which the fifth switching element is turned on and the sixth switching element is turned on, and the fourth operation mode is the operation mode in which the first switching element is turned on and the second switching element is turned on. This is an operation mode in which the third switching element is turned off, the fourth switching element is turned on, the fifth switching element is turned off, and the sixth switching element is turned on.
The switching control circuit is characterized in that the first to fourth operation modes are sequentially executed in one switching cycle, and the output voltage is controlled by adjusting the time ratio of each operation mode. Switching power supply. The switching control circuit
When the first operation mode is started, after the first and sixth switching elements are turned off, the third and third and fifth switching elements are at the timing when the voltage across the third and fifth switching elements drops below a certain level. Control to turn on the fifth switching element
Control to turn on the first switching element at the timing when the voltage across the first switching element drops below a certain level after the second switching element is turned off when the second operation mode is started. And
When starting the third operation mode, after turning off the third and fourth switching elements, the second and sixth switching elements drop to a certain level or less at the timing when the voltage across the second and sixth switching elements drops below a certain level. Control to turn on the sixth switching element
Control to turn on the fourth switching element at the timing when the voltage across the fourth switching element drops below a certain level after the fifth switching element is turned off when the fourth operation mode is started. The switching power supply device according to claim 1. The switching power supply device according to claim 1 or 2, wherein the second step-up capacitor is also used as the first step-up capacitor. A first arm having first, second and third switching elements connected in series from the high side side, the end on the low side side connected to the ground, and an input voltage applied to one end, and others. A step-up inductor whose ends are connected to the connection points of the first and second switching elements, a step-up capacitor connected between the high-side end of the first arm and the ground, and an input winding. And an output winding, one end of the input winding is connected to the connection point of the second and third switching elements, and a voltage half of the voltage across the booster capacitor is generated, and the input A bias circuit supplied to the other end of the winding, a rectifying and smoothing circuit that rectifies and smoothes the voltage generated in the output winding to generate a DC output voltage, and the first to third switching in a predetermined switching cycle. It is equipped with a switching control circuit that turns the element on and off and controls the output voltage.
The first to third operation modes are set in the switching control circuit, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, and the third switching is performed. It is an operation mode in which the element is turned on, and the second operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned off, and the third switching element is turned on. The third operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off.
The switching control circuit is characterized in that the first to third operation modes are sequentially executed in one switching cycle, and the output voltage is controlled by adjusting the time ratio of each operation mode. Switching power supply. The switching control circuit
Control to turn on the third switching element at the timing when the voltage across the third switching element drops below a certain level after the first switching element is turned off when the first operation mode is started. And
Control to turn on the first switching element at the timing when the voltage across the first switching element drops below a certain level after the second switching element is turned off when the second operation mode is started. And
Control to turn on the second switching element at the timing when the voltage across the second switching element drops below a certain level after the third switching element is turned off when the third operation mode is started. 4. The switching power supply device according to claim 4. The switching power supply device according to any one of claims 1 to 5, wherein a resonance capacitor and a resonance inductor are provided at a position in series with the input winding to make the waveform of the current passing through the transformer into a sinusoidal shape. .. The input voltage is a full-wave rectification of a sine wave voltage, and the switching control circuit controls to improve the power factor by bringing the waveform of the input current closer to the waveform of the input voltage. The switching power supply described. A circuit block composed of first, second, and third switching elements connected in series in order , and one end of the third switching element, which is a low-side end of the circuit block , is connected to the ground. An input voltage is applied to one end of the first arm, and the other end is connected to the connection points of the first and second switching elements to connect the first step-up inductor and the high-side end of the first arm. A circuit block consisting of a first step-up capacitor connected between the ground and the ground, and fourth, fifth, and sixth switching elements connected in series in order , the low-side end of the circuit block. One end of the sixth switching element, which is a unit , is connected to the second arm connected to the ground, and the input voltage is applied to one end and the other end is connected to the connection point of the fourth and fifth switching elements. It has a second boosting inductor, a second boosting capacitor connected between the high-side end of the second arm and the ground, and an input winding and an output winding. A transformer whose windings are connected between the connection points of the second and third switching elements and the connection points of the fifth and sixth switching elements, and the voltage generated in the output windings are rectified and smoothed. A control method for a switching power supply that is equipped with a rectifying and smoothing circuit that generates a DC output voltage, and whose output voltage is controlled by turning on / off the first to sixth switching elements at a predetermined switching cycle. There,
The first to fourth operation modes are set, and in the first operation mode, the first switching element is turned off, the second switching element is turned on, the third switching element is turned on, and the fourth. Is an operation mode in which the switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. The second operation mode is the operation mode in which the first switching element is turned on and the second switching element is turned on. This is an operation mode in which the switching element is turned off, the third switching element is turned on, the fourth switching element is turned on, the fifth switching element is turned on, and the sixth switching element is turned off. In the operation mode 3, the first switching element is turned on, the second switching element is turned on, the third switching element is turned off, the fourth switching element is turned off, and the fifth switching element is turned on. , The sixth operation mode is an operation mode in which the sixth switching element is turned on, and in the fourth operation mode, the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off. , The operation mode in which the fourth switching element is turned on, the fifth switching element is turned off, and the sixth switching element is turned on.
A control method for a switching power supply device, characterized in that the output voltage is controlled by sequentially executing the first to fourth operation modes in one switching cycle and adjusting the time ratio of each operation mode. .. When the first operation mode is started, after the first and sixth switching elements are turned off, the third and third and fifth switching elements are at the timing when the voltage across the third and fifth switching elements drops below a certain level. Turn on the fifth switching element,
When starting the second operation mode, after turning off the second switching element, the first switching element is turned on at the timing when the voltage across the first switching element drops below a certain level.
When starting the third operation mode, after turning off the third and fourth switching elements, the second and sixth switching elements drop to a certain level or less at the timing when the voltage across the second and sixth switching elements drops below a certain level. Turn on the sixth switching element,
A claim that, when starting the fourth operation mode, after turning off the fifth switching element, the fourth switching element is turned on at a timing when the voltage across the fourth switching element drops below a certain level. Item 8. The method for controlling a switching power supply device according to item 8. A first arm having first, second and third switching elements connected in series from the high side side, the end on the low side side connected to the ground, and an input voltage applied to one end, etc. A boost inductor whose ends are connected to the connection points of the first and second switching elements, a boost capacitor connected between the high-side end of the first arm and the ground, and an input winding. A transformer having an output winding and one end of the input winding connected to a connection point of the second and third switching elements, and a voltage half of the voltage across the booster capacitor are generated to generate the input. A bias circuit for supplying to the other end of the winding and a rectifying and smoothing circuit for rectifying and smoothing the voltage generated in the output winding to generate a DC output voltage are provided, and the first to third circuits are provided in a predetermined switching cycle. It is a control method of a switching power supply device in which the output voltage is controlled by turning on / off the switching element of the above.
The first to third operation modes are set, and the first operation mode is an operation mode in which the first switching element is turned off, the second switching element is turned on, and the third switching element is turned on. The second operation mode is an operation mode in which the first switching element is turned on, the second switching element is turned off, and the third switching element is turned on, and the third operation mode is Is an operation mode in which the first switching element is turned on, the second switching element is turned on, and the third switching element is turned off.
A control method for a switching power supply device, characterized in that the output voltage is controlled by sequentially executing the first to third operation modes in one switching cycle and adjusting the time ratio of each operation mode. .. When starting the first operation mode, after turning off the first switching element, the third switching element is turned on at the timing when the voltage across the third switching element drops below a certain level.
When starting the second operation mode, after turning off the second switching element, the first switching element is turned on at the timing when the voltage across the first switching element drops below a certain level.
A claim that, when starting the third operation mode, after turning off the third switching element, the second switching element is turned on at a timing when the voltage across the second switching element drops below a certain level. Item 10. The method for controlling a switching power supply device according to item 10.

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