JP2008245388A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply, such as a booster circuit, wherein loss in a switching element due to the recovery current of a diode for rectification is reduced. <P>SOLUTION: A choke coil 12 and a pair of switching elements 15-16 are connected in series with an input power supply. A diode 13 and a capacitor 14 for smoothing are connected in series with both ends of the switching elements 15-16, and a load 19 is connected across the capacitor 14 for smoothing. In addition, an additional chock coil 18 and an additional capacitor 17 are connected in series between the point of common connection between the pair of switching elements 15-16 and the input side of the diode 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply device, and more particularly to a switching power supply device that converts an input power supply voltage into a desired voltage and supplies it to a load.

  Electronic devices and electronic application devices are configured to include an electronic or electric circuit including a plurality of active devices and passive elements, and a power source is required to operate the circuit. In many electronic devices and electronic applied devices, particularly portable devices, a necessary power source is obtained from a primary or secondary battery. However, the output voltage of such a battery is often different from the voltage required by the load, and in order to obtain a stable output voltage from a battery that fluctuates with time, the battery voltage is boosted (or stepped down) to stabilize output. Need to get voltage. Therefore, a switching power supply device with high voltage conversion efficiency is generally used.

Conventional techniques related to switching power supply devices are disclosed in many technical documents. A method of controlling a power supply circuit that uses a step-up chopper type active filter to improve efficiency is disclosed (see, for example, Patent Document 1). Further, a power supply harmonic suppression method and circuit for an inverter device that obtains a desired DC output voltage from a DC voltage obtained by rectifying an AC power supply by suppressing harmonics are disclosed (for example, see Patent Document 2). ). Furthermore, a soft switching power factor correction circuit that achieves soft switching and a high power factor and a control method thereof are disclosed (for example, see Patent Document 3). Further, a chopper operation type DC power supply device that reduces the loss of the diode by reducing the recovery current is disclosed (for example, see Patent Document 4).
Japanese Patent Laid-Open No. 5-184139 (page 2, FIG. 1) JP 7-203681 A (page 3, FIG. 1) Japanese Patent Laid-Open No. 10-94248 (page 2, FIG. 1) Japanese Patent Laid-Open No. 11-341796 (second page, FIG. 1)

  A general conventional booster circuit will be described with reference to FIG. The booster circuit 40 includes a choke coil 42, a rectifying diode 43, a smoothing capacitor (capacitor) 44, and a switching element 46. The booster circuit 40 converts the voltage of the input power source 41 such as a battery into a desired output voltage, and loads 49 To supply.

  In the booster circuit 40 of FIG. 4, the input power supply 41 is connected in series to the choke coil 42 and the switching element 46. A diode 43 and a capacitor 44 are connected in series across the switching element 46. The load 49 is connected to both ends of the capacitor 44.

  The operation of the booster circuit 40 shown in FIG. 4 will be described. The switching element 46 is controlled to be ON or OFF (conducting / non-conducting) by a control signal of a control terminal (for example, gate) of the switching element (for example, transistor) 46. When the switching element 46 is ON, a current flows from the input power supply 41 via the choke coil 42, and electromagnetic energy is stored in the choke coil 42. Next, when the switching element 46 is turned off, the electromagnetic energy stored in the choke coil 42 charges the capacitor 44 via the diode 43. The load 49 is driven by the boosted charging voltage across the capacitor 44. Here, the magnitude of the boost, which is a DC voltage charged in the capacitor 44, depends on the electromagnetic energy stored in the choke coil 42 when the switching element 46 is turned on, and directly on the ON period of the switching element 46.

  In the conventional circuit as described above, that is, the booster circuit 40 including the choke coil 42, the rectifying diode 43, the smoothing capacitor 44, and the switching element 46, the diode is instantaneously switched from the OFF state to the ON state. A recovery current inevitably flows from 43 toward the switching element 46. Due to this recovery current, there is a problem that the switching loss of the switching element 46 increases and the conversion efficiency decreases.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a switching power supply device that can reduce the decrease in conversion efficiency due to such problems, that is, loss of switching elements.

  The switching power supply according to the present invention employs the following characteristic configuration.

(1) In a switching power supply circuit that includes a choke coil, a switching element, and a diode, converts the voltage of the input power supply to a desired output voltage and supplies it additionally.
A first switching element and a second switching element are used as the switching elements connected in series to the input power source together with the choke coil, and the ON / OFF operation timings of the first and second switching elements are shifted to change the switching elements. Switching power supply unit that suppresses loss.
(2) In a switching power supply apparatus that includes a choke coil, a switching element, and a diode, converts a voltage of an input power supply into a desired output voltage and supplies the voltage to a load.
A switching power supply apparatus using a pair of switching elements connected in series to the choke coil as the switching elements, and providing an additional choke coil and an additional capacitor connected in series between a common connection point of the switching elements and the input side of the diode .
(3) The switching power supply device according to (2), wherein control signals for ON / OFF control of the pair of switching elements are shifted in time.
(4) The switching power supply device according to (1) or (2), wherein the transition timing from the OFF state to the ON state of the pair of switching elements is shifted, and the transition from the ON state to the OFF state is performed substantially simultaneously.
(5) The switching power supply device according to (1) or (2), wherein the pair of switching elements are turned ON / OFF alternately at different timings.
(6) The switching power supply device according to any one of (1) to (5), wherein the switching element is a MOS transistor or a bipolar transistor.

  According to the switching power supply device of the present invention, the following characteristics peculiar in practice can be obtained by the characteristic configuration as described above. That is, the loss of the switching element due to the recovery current of the diode that occurs transiently when the switching element shifts from the ON state to the OFF state can be suppressed. The reason is that a series circuit of an additional choke coil and an additional capacitor is provided between the common connection point of the pair of switching elements and the input side of the diode.

  By suppressing the loss of the switching element, the heat dissipation means (heat sink) of the switching element can be omitted or miniaturized. In some cases, a small and inexpensive switching element can be used, and an electronic device using such a switching power supply device can be used. It is possible to suppress temperature rise in the device and improve stability and reliability.

  Hereinafter, the configuration and operation of a preferred embodiment of a switching power supply device and loss reduction method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

  First, a description will be given with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a first embodiment of a switching power supply device according to the present invention.

  1 includes a choke coil 12, a pair of switching elements 15-16, a rectifying diode (hereinafter simply referred to as a diode) 13, a smoothing capacitor 14, an additional capacitor 17, and an additional choke coil 18. Has been.

  The input power supply 11 is connected to a series circuit of main current paths of the choke coil 12 and the pair of switching elements 15-16. A diode 13 and a smoothing capacitor 14 are connected in series to both ends of a pair of switching elements 15-16 connected in series, and a load 19 is connected to both ends of the smoothing capacitor 14. The additional capacitor 17 and the additional choke coil 18 are connected in series between the node A that is a common connection point of the pair of switching elements 15-16 and the node B that is a common connection point of the choke coil 12, the diode 18, and the switching element 15. It is connected.

  Next, the operation of the switching power supply device 10 shown in FIG. 1 will be described. Substantially equal control signals are input to the control terminals (for example, gates) of the switching elements 15-16, and these switching elements 15-16 are ON / OFF controlled substantially simultaneously. When the pair of switching elements 15-16 is ON, a current flows from the input power source 11 to the choke coil 12, and electromagnetic energy substantially proportional to the ON period is stored. When the switching element 15-16 is turned off, the smoothing capacitor 14 is charged via the diode 13 by the sum of the energy stored in the input power supply 11 and the choke coil 12. Accordingly, the smoothing capacitor 14 is charged with a voltage larger than the voltage of the input power supply 11, and the smoothed DC voltage is supplied to the load 19. Therefore, the switching power supply device 10 can boost the voltage of the input power supply (for example, battery) and supply it to the load 19.

  The additional capacitor 17 and the additional choke coil 18 suppress the peak value (or peak value) of the above-described recovery current flowing in the diode 13 transiently when the switching element 15-16 is turned OFF. Reduce 16 losses. If the loss of the switching element is reduced, a low-rated (inexpensive) device can be used as the switching element, or the heat dissipation device can be reduced in size or omitted, and the operation can be stabilized.

  Next, a second embodiment of the switching power supply device according to the present invention will be described with reference to FIG. FIG. 2A is a circuit diagram of this switching power supply circuit. FIG. 2B is a waveform diagram of a control signal for controlling ON / OFF of the pair of switching elements in FIG. This switching power supply device 20 is an example applied to a power factor correction circuit of a power supply device.

  2A includes a choke coil 22, a pair of switching elements 25-26, a diode 23, a smoothing capacitor 24, an additional capacitor 27, and an additional choke coil 28. Except that the input power source 21 is a power source obtained by rectifying an AC power source (for example, a commercial power source) with a full-wave rectifier circuit, the configuration is the same as that in FIG. That is, a choke coil 22 and a pair of switching elements 25-26 are connected in series to the input power source 21, a diode 23 and a smoothing capacitor 24 are connected in series to both ends of the switching element 25-26, and both ends of the smoothing capacitor 24 are connected. Is connected to a load 29. An additional choke coil 28 and an additional capacitor 27 are connected in series between the nodes A and B.

  In addition, a control signal that is turned ON / OFF substantially simultaneously is input to the control terminals of the switching elements 25-26. However, according to an embodiment specific to the present invention, as shown in FIG. 2B, control signals S1 and S2 that are slightly out of phase are input to switching elements 25-26. The control signal S1 of the switching element 25 is turned on (conductive) at time t1, and is turned off (non-conductive) at time t2. On the other hand, the control signal S2 of the switching element 26 is turned on at time t0 and turned off at time t2. That is, the control signals of both the switching elements 25-26 are such that the ON start time of the switching element 25 is delayed by T (= t1-t0) from the ON start time of the switching element 26, and the transition time to the OFF state is substantially simultaneous ( Time t2). In other words, the switching element 26 shifts to the ON state earlier than the switching element 25 by a slight time difference T.

  Next, the operation of the switching power supply device 20 shown in FIG. 2A will be described with reference to the operation waveform diagram of the switch elements 25-26 in FIG. As shown in FIG. 2B, the switching element 26 is turned on before the switch element 25. As a result, the sum of the current flowing through the choke coil 22, the additional capacitor 27, the additional choke coil 28 and the switching element 26 and the current flowing through the diode 23, the additional capacitor 27, the additional choke coil 28 and the switching element 26 is supplied to the switching element 26. Flows. At this time, the current flowing through the switching element 26 flows through the additional choke coil 28, and the rising waveform of the current is reduced. As a result, the switching loss that occurs when the switching element 26 shifts from the OFF state to the ON state is suppressed. Can do.

  Thereafter, when the switching element 25 is turned on, current flows through the choke coil 22, the switching element 25, and the switching element 26, and energy is stored in the choke coil 22. Therefore, when the switching element 25 and the switching element 26 are turned off, the energy stored in the choke coil 22 flows to the smoothing capacitor 24 through the diode 23 and is charged. Therefore, the output voltage supplied to the load 29 can be boosted to a voltage higher than the input voltage.

  Next, still another embodiment of the switching power supply device according to the present invention will be described with reference to FIG. FIG. 3A is a circuit diagram of the switching power supply device 30 of such another embodiment. FIG. 3B is a waveform diagram of control signals for turning on / off the pair of switching elements of the switching power supply device 30 shown in FIG.

  The switching power supply device 30 shown in FIG. 3A has the same configuration as the switching power supply device 20 shown in FIG. That is, it is constituted by a DC input power supply 31 obtained by full-wave rectification of an AC power supply, a choke coil 32, a diode 33, a smoothing capacitor 34, a pair of switching elements 35-36, an additional capacitor 37, and an additional choke coil 38. A load 39 is connected to both ends of the smoothing capacitor 34. Since the connection relationship between these components or elements 31 to 39 is the same as that shown in FIG.

  In this switching power supply device 30, the control signal input to the control terminals of the switching element 35 and the switching element 36 or the switching timing is different from the case of FIG. Switching control signals of the switching elements 35 and 36 are shown as signals S3 and S4 in FIG. In FIG. 3B, the switching element 35 and the control signals S3 and S4 of the switching element 35 are turned on / off with substantially opposite polarities. In the switching power supply device 30 of this embodiment, the switching elements 35 and the switching elements 36 are turned ON / OFF substantially alternately. Thereby, the loss of the switching element 36 can be reduced similarly to the switching power supply device 20 of the embodiment shown in FIG.

  The preferred embodiment of the switching power supply device according to the present invention has been described in detail above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist and spirit of the present invention. For example, as the switching element, a bipolar transistor or the like can be used instead of the illustrated MOS transistor.

It is a circuit diagram which shows the basic composition of the switching power supply circuit by this invention. 1 shows a first embodiment of a switching power supply device according to the present invention, in which (A) is a circuit diagram and (B) is a waveform diagram of control signals of a pair of switching elements in (A). The 2nd Embodiment of the switching power supply circuit by this invention is shown, (A) is a circuit diagram, (B) is a wave form diagram of the control signal of a pair of switching element in (A). The circuit diagram of the conventional booster circuit is shown.

Explanation of symbols

10, 20, 30 Switching power supply device 12, 22, 32 Choke coil 13, 23, 33 Diode 14, 24, 34 Smoothing capacitor 15-16, 25-26, 35-36 Switching element 17, 27, 37 Additional capacitor 18 , 28, 38 Additional choke coil 19, 29, 39 Load

Claims (6)

In a switching power supply circuit that includes a choke coil, a switching element, and a diode, converts the voltage of the input power supply into a desired output voltage and supplies it additionally.
A first switching element and a second switching element are used as the switching elements connected in series to the input power source together with the choke coil, and the ON / OFF operation timings of the first and second switching elements are shifted to change the switching element. A switching power supply characterized by suppressing loss. In a switching power supply device that includes a choke coil, a switching element, and a diode, converts a voltage of an input power supply into a desired output voltage and supplies the voltage to a load.
A pair of switching elements connected in series to the choke coil is used as the switching element, and an additional choke coil and an additional capacitor connected in series are provided between the common connection point of the switching elements and the input side of the diode. Switching power supply device.   The switching power supply according to claim 2, wherein a control signal for ON / OFF control of the pair of switching elements is shifted in time.   The switching power supply according to claim 1 or 2, wherein the transition timing from the OFF state to the ON state of the pair of switching elements is shifted, and the transition from the ON state to the OFF state is performed substantially simultaneously.   The switching power supply according to claim 1 or 2, wherein the pair of switching elements are alternately turned on and off at different timings. 6. The switching power supply device according to claim 1, wherein the switching element is a MOS transistor or a bipolar transistor.

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