JP2010273431A - Power factor improved type switching power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power factor improved type switching power supply unit capable of stably supplying voltage to a control circuit and easily reducing loss of activation circuit. <P>SOLUTION: The power supply unit includes a first Zener diode 46, between a gate terminal of a first activation transistor 44 and the ground. The unit includes a choke auxiliary power supply 40 for extracting a voltage from a voltage step-up choke 20, and the unit includes a second transistor 52 with a drain terminal connected to the output of the choke auxiliary power supply 40 and a gate terminal connected to the first Zener diode 46. A first upper limit value V1, capable of being supplied from the source terminal of the first transistor 44 via a first reverse flow prevention diode 42, is higher than the activation starting voltage of an active filter control circuit 32. A second upper limit value V2, capable of being supplied from the source terminal of the second transistor 52 via a second reverse flow prevention diode 54 is higher than the first upper limit value V1. The choke auxiliary power supply 40 outputs a voltage which is higher than the Zener voltage of the first Zener diode 46. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power factor improvement type switching power supply device including an active power source and an auxiliary power source that supplies a voltage to a power supply line of a control circuit that drives an on / off switching element.

  Conventionally, it has been equipped with an active filter that converts a pulsating voltage obtained by full-wave rectification of a commercial AC voltage into a DC boost voltage and outputs it. At the same time, the input current is shaped and the power factor is adjusted by applying predetermined control to the active filter. There is a power factor improvement type switching power supply which improves. In addition, a switching power supply device in which a DC-DC converter is provided after the active filter and converts the boosted voltage into a direct-current voltage that can be directly input to various electronic circuits and electronic devices and outputs the same is widely used.

  This type of power factor improving type switching power supply generally includes two control circuits for turning on and off each switching element of an active filter and a subsequent DC-DC converter, and further supplies power to each control circuit. For this reason, an auxiliary power supply circuit that converts a commercial AC voltage into a low DC voltage and outputs it is provided.

  Conventionally, as a power factor improving type switching power supply device having an active filter and a DC-DC converter in the subsequent stage, there is a switching power supply device disclosed in Patent Document 1, for example. This switching power supply device includes an active filter control circuit for driving a switching element of an active filter and a converter control circuit for driving a switching element of a DC-DC converter, and power lines of the two control circuits are connected to each other, and the power supply A smoothing capacitor is connected between the line and ground. Also, as an auxiliary power supply circuit that supplies voltage to the smoothing capacitor, a startup circuit that supplies voltage when the power is turned on, and a rectified voltage that rectifies the voltage across the auxiliary winding provided in the boost choke of the active filter after startup And a rectifier circuit that outputs a rectified voltage obtained by rectifying the voltage across the auxiliary winding provided in the transformer of the DC-DC converter.

  In the embodiment disclosed in FIG. 1 of Patent Document 1, the start-up circuit includes a MOS-FET whose source terminal is connected to the power supply line, and supplies current from the active filter input to the power supply line, and a gate of the MOS-FET. A first Zener diode connected between the terminal and the ground; and a bias resistor for supplying a bias current from the input of the active filter to the first Zener diode. The first voltage determined by the Zener voltage of the first Zener diode and the gate threshold voltage of the MOS-FET is set to a voltage higher than the starting voltages of the two control circuits.

  Further, the starter circuit is connected to a series circuit of a second Zener diode and a transistor switch in parallel with the first Zener diode. When the transistor switch is turned on, the second voltage determined by the Zener voltage of the second Zener diode and the gate threshold voltage of the MOS-FET is lower than the first voltage, and the two control circuits The voltage is set higher than the stop voltage.

  When the power is turned on, the transistor switch is turned off, each control circuit is started by being supplied with the first voltage from the first MOS-FET, and after each control circuit is started, the transistor switch is turned on. Then, the power supply from the MOS-FET to each control circuit is stopped, and each control circuit continues to operate in response to the supply of the voltage obtained by smoothing the outputs of the choke rectifier circuit and the transformer rectifier circuit.

  As described above, each control circuit of the switching power supply device of Patent Document 1 is ideally supplied with a voltage from the MOS-FET of the start-up circuit for a predetermined short period of time such as at the start-up or when the load suddenly changes, After startup, an operation is performed in which the voltage supply from the MOS-FET with a large loss during operation is stopped and the voltage supply is steadily received from the choke rectifier circuit and the transformer rectifier circuit.

JP 2004-320858 A

  However, in the case of the switching power supply device of Patent Document 1, the choke rectifier circuit is changed by changing the ON width of the switching element of the active filter from the maximum to the minimum in a range where the input voltage and output current of the active filter are statically changed. The voltage obtained by smoothing the output of fluctuates greatly. In particular, in a switching power supply device capable of continuous input of AC 100 V / 200 V system, the voltage fluctuation is remarkable.

  In addition, the voltage obtained by smoothing the output of the transformer rectifier circuit slightly varies within a range in which the input voltage and output current of the DC-DC converter vary statically. In addition, when the switching operation of the DC-DC converter is stopped by a remote control operation that stops power supply to the load or an overvoltage protection operation that prevents continuous application of overvoltage to the load, the voltage supply from the transformer rectifier circuit is stopped. It may disappear completely.

  Therefore, the voltage supply capability of the choke rectifier circuit and the transformer rectifier circuit is reduced depending on the use conditions of the switching power supply device. As a result, the MOS-FET of the start-up circuit operates for a long time, and the MOS-FET has a large loss and heat generation There was a problem that caused.

  As a countermeasure for this problem, for example, in order to make the minimum value of the smoothing voltage that can be supplied from the choke rectifier circuit higher than the first voltage, adjustment is made by a method such as increasing the number of turns of the auxiliary winding of the choke rectifier circuit. Is also possible. However, in the case of this method, the maximum value of the smoothing voltage is also increased in conjunction with this, and there is a possibility that a new adverse effect of exceeding the voltage at which each control circuit can operate normally may occur. There was a limit.

  Further, the active filter control circuit and the converter control circuit generally have different start voltage and stop voltage. Therefore, in the circuit configuration in which the first and second Zener diodes of the starting circuit of the switching power supply device are switched, steady fluctuations in the voltage obtained by smoothing the outputs of the choke rectifier circuit and the transformer rectifier circuit, It is not easy to set circuit constants that realize the above-mentioned ideal operation while taking into consideration the difference between the start and stop voltages.

  The present invention has been made in view of the above-described background art, and can stably and safely supply a voltage to the control circuit of the switching element regardless of use conditions such as an input voltage and a load. It is an object of the present invention to provide a power factor improving switching power supply device that can easily reduce loss.

The invention according to claim 1 includes a step-up chopper type active filter that includes a step-up choke and a first switching element, converts an input full-wave rectified voltage into a DC voltage, and outputs the DC voltage, and the first switching An active filter control circuit that drives the element on and off to control the power factor improvement operation of the active filter, a power supply capacitor connected between a power supply line of the active filter control circuit and the ground, and a drain terminal are A first transistor which is an N-channel MOS FET connected to the input of the active filter and whose source terminal is connected to the power supply capacitor via a first backflow prevention diode, and a cathode terminal is the first transistor The first transistor is connected to the gate terminal of the transistor and the anode terminal is connected to the ground. A first Zener diode that determines a first upper limit value that is an upper limit value of a voltage that can be supplied to the power supply capacitor via the first backflow prevention diode, an input of the active filter, and the first A bias resistor connected between the cathode terminal of the Zener diode and supplying a bias current to the first Zener diode to generate a Zener voltage; a choke auxiliary winding provided in the boost choke; and a generated voltage thereof. In a power factor improving switching power supply comprising a rectifier circuit for rectification, and a choke auxiliary power supply that outputs a rectified voltage generated by the rectifier circuit toward the power supply capacitor,
The drain terminal is connected to the output of the choke auxiliary power supply, the source terminal is connected to the power supply capacitor via a second backflow prevention diode, the gate terminal is connected to the cathode terminal of the first Zener diode, A second transistor which is an N-channel MOS FET provided so as to be able to output a predetermined voltage from the source terminal;
The first upper limit value is higher than a starting start voltage of the active filter control circuit, and is an upper limit value of a voltage that can be supplied from the second transistor to the power supply capacitor via the second backflow prevention diode. The second upper limit value determined by the first Zener diode is higher than the first upper limit value, and the choke auxiliary power supply is This is a power factor improving type switching power supply provided so that a voltage higher than the Zener voltage of the diode can be output.

  According to the second aspect of the present invention, in addition to the configuration of the first aspect, the second switching element for generating an AC voltage by intermittently turning on and off the output voltage of the active filter at the output end of the active filter. A transformer provided with a primary winding to which the AC voltage is applied and a secondary winding magnetically coupled to the primary winding, and a DC voltage by rectifying and smoothing the voltage generated in the secondary winding. An output rectifying / smoothing circuit that generates and supplies an output voltage to a load; a converter control circuit that drives the second switching element on and off to control stabilization of the output voltage; and a tertiary winding provided in the transformer And an auxiliary rectifying / smoothing circuit for rectifying and smoothing the generated voltage, and the output of the auxiliary rectifying / smoothing circuit is connected to the power supply line of the converter control circuit to supply power. A DC-DC converter having a data auxiliary power supply, and an output of the converter auxiliary power supply is connected to a power supply line of the active filter control circuit, and the first backflow prevention diode is connected from the first transistor. The first upper limit value determined by the first Zener diode is the upper limit value of the voltage that can be supplied to the power supply capacitor via the starting voltages of the active filter control circuit and the converter control circuit. In parallel with the first Zener diode, a series circuit of a second Zener diode and a changeover switch arranged in the same direction as the first Zener diode is connected, and when the changeover switch is turned on, Provided from the first transistor to the power supply capacitor through the first backflow prevention diode. The upper limit value of the voltage that can be switched from the first upper limit value to a third upper limit value determined by the second Zener diode, and the third upper limit value is the first upper limit value. Less than the stop voltage of the active filter control circuit and the converter control circuit, the voltage that the converter auxiliary power supply can output is lower than the second upper limit value, and the third The changeover switch is a power factor improvement type switching power supply device that is higher than an upper limit value and is controlled to be turned on when the active filter control circuit or the converter control circuit is activated and operating.

  In addition to the configuration of claim 1, the invention according to claim 3 of the present application is the first switching in which the output voltage of the active filter is intermittently turned on and off to generate an AC voltage at the output end of the active filter. An element, a transformer provided with a primary winding to which the AC voltage is applied and a secondary winding magnetically coupled to the primary winding, and a DC voltage obtained by rectifying and smoothing a voltage generated in the secondary winding. Output rectifying and smoothing circuit that generates an output voltage and supplies an output voltage to a load, a converter control circuit that drives the second switching element on and off to control stabilization of the output voltage, an output of the active filter, and the converter A starting circuit that is provided between the control circuit and the power supply line and supplies a starting voltage to the converter control circuit; a tertiary winding provided in the transformer; A DC-DC converter including a converter auxiliary power supply that supplies power by connecting an output of the auxiliary rectification smoothing circuit to a power supply line of the converter control circuit. Between the power line of the active filter control circuit and the power line of the converter control circuit, a third backflow prevention diode having a cathode terminal side disposed on the power line side of the active filter control circuit is connected, In parallel with the Zener diode, a series circuit of a second Zener diode and a change-over switch arranged in the same direction as the first Zener diode is connected, and when the change-over switch is turned on, the first transistor and the second switch are turned on. Can be supplied to the power supply capacitor through a single backflow prevention diode. The upper limit value of the voltage is switched from the first upper limit value to the third upper limit value determined by the second Zener diode, the third upper limit value is lower than the first upper limit value, In addition, a voltage higher than the stop voltage of the active filter control circuit and capable of being output by the converter auxiliary power supply is lower than a total value of the forward voltage of the third backflow prevention diode and the second upper limit value. And the higher than the total value of the forward voltage of the third backflow prevention diode and the third upper limit value, the changeover switch is activated by an active filter control circuit or a converter control circuit. This is a power factor improving type switching power supply controlled to be turned on when the power is on.

  In addition to the configuration of claim 3, the invention of claim 4 of the present application is arranged such that the cathode terminal side is arranged on the output side of the converter auxiliary power source at the connection point between the third backflow prevention diode and the power source line of the converter control circuit. A third Zener diode having an anode terminal connected to the third backflow prevention diode side is inserted, and the voltage that can be output from the converter auxiliary power supply is the Zener voltage of the third Zener diode and the third Zener diode. Lower than the total value of the forward voltage of the backflow prevention diode and the second upper limit value, and the Zener voltage of the third Zener diode, the forward voltage of the third backflow prevention diode, and the third It is a power factor improving switching power supply set higher than the total value with the upper limit value.

  According to the fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the anode terminal is connected to the output side of the converter auxiliary power supply at the connection point between the output of the converter auxiliary power supply and the power supply line of the converter control circuit. A power factor improving switching power supply device in which a fourth backflow prevention diode having a cathode terminal connected to the converter control circuit side is inserted, and a capacitor is connected between the cathode terminal of the fourth backflow prevention diode and the ground It is.

  According to the power factor improvement type switching power supply device of the present invention, the first power supply operation of the first transistor for supplying the starting voltage is continuously stopped after the active filter control circuit is started, It is possible to easily prevent a large loss from occurring in the transistor. Further, after the start-up, the active filter control circuit is supplied with a stable and safe voltage limited to the second upper limit value or less from the second transistor, so that an excessively high voltage may be applied to the active filter control circuit. There is no.

  Moreover, according to the power factor improvement type switching power supply device provided with the DC-DC converter according to claims 2 to 4 of the present invention, in addition to the above effects, the priority of the choke auxiliary power source and the converter auxiliary power source is set as the use condition. By appropriately switching according to this, voltage supply to the two control circuits can be stably performed with low loss.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a first embodiment of a power factor improving switching power supply device according to the present invention. It is a circuit diagram which shows 2nd embodiment of the power factor improvement type | mold switching power supply device of this invention. It is a circuit diagram which shows the structural example of the output smoothing circuit and converter auxiliary power supply of 2nd embodiment. It is a circuit diagram which shows the other example of a structure of the output smoothing circuit and converter auxiliary power supply of 2nd embodiment. It is a circuit diagram which shows 3rd embodiment of the power factor improvement type | mold switching power supply device of this invention. It is a circuit diagram which shows 4th embodiment of the power factor improvement type | mold switching power supply device of this invention.

  Hereinafter, a first embodiment of a power factor improving type switching power supply device of the present invention will be described with reference to FIG. The power factor improvement type switching power supply device 10 of the first embodiment includes a full-wave rectifier circuit 14 to which a commercial AC power supply 12 is connected to an input and full-wave rectifies and outputs the commercial AC voltage. A power factor improving active filter 16 that converts the full-wave rectified voltage into a predetermined DC voltage and outputs it is connected to the subsequent stage of the full-wave rectifier circuit, and a load 18 is connected to the output terminal.

  The active filter 16 includes a general boost chopper type power conversion unit including a boost choke 20, a first switching element 22, a boost diode 24, and a boost capacitor 26. In other words, the input full-wave rectified voltage is interrupted by the first switching element 22 via the boosting choke 20, and the voltage generated at both ends of the first switching element 22 is rectified and smoothed by the boosting diode 24 and the boosting capacitor 26. To perform the operation. The boost voltage Va and the boost current Ia are supplied to the load 18 connected to both ends of the boost capacitor 26.

  The active filter 16 receives signals from the power detection unit, the Va detection circuit 28 that monitors the boosted voltage Va, the Iin detection circuit 30 that monitors the input current Iin, and the two detection circuits 28 and 30. And an active filter control circuit 32 for driving the first switching element 22 on and off, and a power supply capacitor 36 connected between the power supply line 34 of the active filter control circuit 32 and the ground.

  The active filter control circuit 32 is composed of a general first control IC 32a and other electronic components, and the boosted voltage Va is reduced by adjusting the time ratio based on the signals received from the two detection circuits 28 and 30. At the same time, the input current Iin is shaped into a substantially sinusoidal shape to generate a drive pulse capable of improving the power factor. Then, the drive pulse is output toward the drive terminal of the first switching element 22 to drive the first switching element 22 on and off.

  The active filter control circuit 32 is set with a specific start voltage and stop voltage. In other words, the active filter control circuit 32 starts operating when the power supply line 34 is supplied with a voltage equal to or higher than the start-up voltage, and after start-up, the operation is stopped when the voltage of the power supply line 34 drops below the stop voltage. Here, the start voltage and stop voltage of the first control IC 32a itself are the start voltage and stop voltage of the active filter control circuit 32 as they are. Further, the stop voltage is set lower than the start voltage, and so-called start and stop hysteresis characteristics are given.

  Further, the active filter 16 is an auxiliary power supply circuit that supplies a voltage to the power supply line 34 of the active filter control circuit 32, and supplies a voltage for starting the active filter control circuit 32 from the input end of the active filter 16 when input is turned on. After the activation circuit 38 and the active filter control circuit 32 are activated, a choke auxiliary power supply 40 that supplies a voltage by using a voltage generated in the boost choke is provided.

  The start circuit 38 is a first transistor that is an N-ch MOS FET whose drain terminal is connected to the input of the active filter 16 and whose source terminal is connected to the power supply line 34 via the first backflow prevention diode 42. 44. The gate of the first transistor 44 is connected to the cathode terminal of the first Zener diode 46, and the anode terminal is connected to the ground. Further, a bias resistor 47 for supplying a bias current to the first Zener diode 46 and generating a Zener voltage V46 is connected between the input of the active filter 16 and the cathode terminal of the first Zener diode 46.

The first Zener diode 46 determines the first upper limit value V1, which is the upper limit value of the voltage that can be supplied to the power supply line 34 by the starting circuit 38. The first upper limit value V1 is expressed by the following equation (1). expressed.
V1 = V46− (V44 + V42) (1)
Here, V44 is the gate threshold voltage of the first transistor 44, and V42 is the forward voltage of the first backflow prevention diode 42. For example, the first backflow prevention diode 42 may be configured by connecting a plurality of diodes in series in the same direction. In this case, the total value of the forward voltages of the respective diodes corresponds to V42. The first Zener diode 46 is selected to have a Zener voltage V46 at which the first upper limit value V1 is higher than the starting voltage of the active filter control circuit 32.

  The choke auxiliary power supply 40 includes a choke auxiliary winding 48 magnetically coupled to the boost choke 20 and a rectifier circuit 50 that rectifies and outputs a voltage generated by the choke auxiliary winding 48. The rectified voltage that can be output from the choke auxiliary power supply 40 is set to be at least higher than the Zener voltage V46 of the first Zener diode 46 within a range where the input voltage and the output current Ia change statically. ing.

  The output of the choke auxiliary power supply 40 is connected to the power supply line 34 via the second transistor 52 and the second backflow prevention diode 54. The second transistor is an N-ch MOS type FET, the drain terminal is connected to the output of the choke auxiliary power supply 40, and the source terminal is connected to the power supply line 34 via the second backflow prevention diode 54. The gate terminal is connected to the cathode terminal of the first Zener diode 46.

As described above, a voltage higher than at least the Zener voltage V46 of the first Zener diode 46 is supplied to the drain terminal of the second transistor 52 from the output of the choke auxiliary power supply 40, and the second transistor 52 The voltage supplied to the power supply line 34 via the second backflow prevention diode 54 is limited to the second upper limit value V2 expressed by the equation (2).
V2 = V46− (V52 + V54) (2)
Here, V52 is the gate threshold voltage of the second transistor 52, and V54 is the forward voltage of the second backflow prevention diode 54. For example, the second backflow prevention diode 54 may be configured by connecting a plurality of diodes in series in the same direction. In this case, the total value of the forward voltages of the respective diodes corresponds to V54.

In the second transistor 52, the second backflow prevention diode 54, the first transistor 44, and the first backflow prevention diode 42, the total value of the gate threshold voltage V52 and the forward voltage V54 is the forward value of the gate threshold voltage V44. It is set to be smaller than the total value of the directional voltage V42. Specifically, this condition can be easily satisfied by selecting each transistor element and adjusting the number of each diode. Therefore, the relationship of Formula (3) always holds between the first upper limit value V1 and the second upper limit value V2.
V2> V1 (3)

  The two backflow prevention diodes 42 and 54 and the power supply capacitor 36 serve as a peak hold circuit. Since the voltage input to the active filter 16 is a voltage obtained by full-wave rectification of the commercial AC voltage, a pulsating current that repeatedly rises and falls in the drain terminal and the source terminal of the first transistor 44 at a cycle twice that of the commercial frequency. Voltage is generated. Then, the DC voltage can be supplied to the power supply line 34 by peak-holding the pulsating voltage with the first backflow prevention diode 42 and the power supply capacitor 36. A pulsating voltage that repeatedly rises and falls at a cycle twice that of the commercial frequency is also generated at the drain terminal and the source terminal of the second transistor 52. Then, the DC voltage can be supplied to the power supply line 34 by peak-holding the pulsating voltage with the second backflow prevention diode 54 and the power supply capacitor 36.

  In the power factor improvement type switching power supply device 10 having the above configuration, when the commercial AC power supply 12 is input to the input, the active filter control circuit 32 is connected to the power supply line 34 by the voltage supplied from the first transistor 44. The voltage reaches the starting voltage and starts operation.

  After the start-up, a predetermined voltage is generated in the boost choke 20 by turning on / off the first switching element 22, and the boost voltage Va also increases. When a predetermined voltage is generated in the boost choke 20, the output of the choke auxiliary power supply 40 rises, the voltage supply from the second transistor 52 starts exceeding the Zener voltage V 46 of the first Zener diode 46, and the A voltage corresponding to the upper limit of 2 is generated. At the same time, the voltage between the gate and the source of the first transistor 44 drops below the gate threshold voltage V44, and the voltage supply from the start-up circuit 38 is stopped when the first transistor 44 is turned off.

  As described above, after the active filter control circuit 32 is started, the choke auxiliary power supply 40 operating at a low loss is supplied via the second transistor 52 within a range in which the input voltage and the output current Ia change statically. Since power is constantly supplied to the line 34 and the operation of the first transistor 44 is steadily stopped, no significant loss occurs in the first transistor 44. In addition, this operation is based on the premise that the two upper limit values V1 and V2 satisfy the relationship shown in Expression (3), but the upper limit values V1 and V2 are determined by the fixed characteristic values of each semiconductor component. Although the circuit configuration is simple, the relationship of Expression (3) can be reliably realized.

  Also, even if the output of the choke auxiliary power supply 40 fluctuates higher after use, the voltage supplied to the power supply line 34 is limited to the second upper limit value V2 or less, so that the active filter control circuit 32 There is no risk of applying excessive high voltage.

  Further, for example, when the load 18 suddenly changes during the operation after startup and the boosted voltage Va changes, the active filter control circuit 32 performs control to temporarily narrow the ON pulse width of the first switching element 22. . Then, the output of the choke auxiliary power supply 40 decreases, and a period in which the voltage supply from the second transistor 52 cannot be maintained occurs. However, when the voltage of the power supply line 34 decreases to the first upper limit value V1, the first transistor 44 in the stopped state starts operating instantaneously, and the voltage corresponding to the first upper limit value V1 is set to the power supply line 34. Therefore, the operation of the active filter control circuit 32 does not stop. Further, since the alternative supply by the first transistor 44 occurs only once in a very short time, loss and heat generation in the first transistor 44 are small. Therefore, a small and inexpensive transistor can be selected as the first transistor 44.

  Next, a power factor correction type switching power supply 60 according to a second embodiment of the present invention will be described with reference to FIGS. Here, the same components as those of the power factor improving switching power supply device 10 described above are denoted by the same reference numerals and description thereof is omitted. In addition to the configuration of the power factor improving switching power supply 10 described above, the power factor improving switching power supply 60 is provided with a DC-DC converter 62 after the active filter 16. The voltage Va is converted into an output voltage Vo which is a different DC voltage, and the output voltage Vo and the output current Io are supplied to the load 18 connected to the output terminal. A series circuit of a second Zener diode 64 and a switching transistor 66 that operates as a changeover switch is connected in parallel with the first Zener diode 46 of the starting circuit 38. Furthermore, voltage dividing resistors 68a and 68b are provided between the operation state output terminal 32b of the first control IC 32a and the ground, and the midpoint of the voltage dividing resistors 68a and 68b is connected to the base terminal of the switching transistor 66. ing. Other circuit configurations are the same as those of the power factor improving switching power supply 10. Hereinafter, the newly provided configuration will be described in detail.

  The DC-DC converter 62 is connected to a transformer 70 having a primary winding 70a and a secondary winding 70b, a second switching element 72 connected in series with the primary winding, and an output of the secondary winding 70b. The output converter rectifying / smoothing circuit 74 is provided. That is, the input boosted voltage Va is intermittently generated by the second switching element 72 via the primary winding 70a, and an intermittent voltage is generated in the primary winding 70. Then, the intermittent voltage generated in the secondary winding 70b is rectified and smoothed by the output rectifying and smoothing circuit 74, thereby generating the DC output voltage Vo.

  The DC-DC converter 62 includes, in addition to the above power converter, a Vo detection circuit 76 that monitors the output voltage Vo and amplifies the error, and an overvoltage detection circuit that also monitors the output voltage Vo and detects the occurrence of an overvoltage. 78 and a converter control circuit 80 that receives the signals of the two detection circuits 76 and 78 and controls the on / off operation of the second switching element.

  The converter control circuit 80 includes a general second control IC 80a and other electronic components, and performs a pulse width modulation based on a signal received from the Vo detection circuit 76, thereby stabilizing the output voltage Vo. Is generated. Then, the drive pulse is output toward the drive terminal of the second switching element 72 to drive the second switching element 72 on and off. When a signal indicating that an overvoltage has occurred (hereinafter referred to as an OV signal) is output from overvoltage detection circuit 78 to converter control circuit 80, converter control circuit 80 stops outputting the drive pulse. In addition, a function of stopping the operation of the second switching element 72 is provided.

  The converter control circuit 80 is set with a specific start voltage and stop voltage. That is, the operation starts when the power supply line 84 of the converter control circuit 80 is supplied with a voltage equal to or higher than the activation voltage, and after the activation, the operation stops when the voltage of the power supply line 84 falls below the stop voltage. Here, the start voltage and stop voltage of the second control IC 80a itself are the start voltage and stop voltage of the converter control circuit 80 as they are. Further, the stop voltage is set lower than the start voltage, and hysteresis characteristics of start and stop are given. Note that the start voltage and stop voltage of the converter control circuit 80 and the active filter control circuit 32 are not necessarily the same.

  Further, the DC-DC converter 62 includes a converter auxiliary power supply 86 that supplies a voltage to the power supply line 84 of the converter control circuit 80. The converter auxiliary power source 86 includes a tertiary winding 70c provided in the transformer 70 and an auxiliary rectifying / smoothing circuit 88 that outputs a predetermined DC voltage obtained by rectifying and smoothing the generated voltage. The output of the converter auxiliary power supply 86 (the output of the auxiliary rectifying and smoothing circuit 88) is connected to the power supply line 84, and further connected to the power supply line 34 of the active filter control circuit 32.

  The converter auxiliary power supply 86 can be variously set according to the form of the power conversion unit of the DC-DC converter 62. For example, when the power converter of the DC-DC converter 62 is a flyback system, as shown in FIG. 3, the voltage generated in the tertiary winding 70c is peak-held when the second switching element 72 is off. If the tertiary winding 70c and the auxiliary rectifying / smoothing circuit 88 are configured as described above, the converter auxiliary power source 86 can output a stable DC voltage that is substantially proportional to the output voltage Vo that has been subjected to stabilization control.

  When the power conversion unit of the DC-DC converter 62 is a single forward system, as shown in FIG. 4A, the tertiary winding 70c and auxiliary rectification having the same configuration as the secondary winding 70b and the output rectifier circuit 74 are provided. If the smoothing circuit 88 is configured, the converter auxiliary power supply 86 can output a stable DC voltage that is approximately proportional to the output voltage Vo that has been subjected to stabilization control. Further, as shown in FIG. 4B, the voltage generated in the tertiary winding 70c is peak-held when the second switching element 72 is turned on, and the peak regulator voltage is not necessarily constant. If the configuration is such that the converter auxiliary power supply 86 can output, a stable DC voltage defined by the series regulator 88a can be output.

  However, in the case of the converter auxiliary power supply 86 illustrated in FIG. 3 and FIG. 4, within the range where the boost voltage Va and the output current Io change statically, the above-mentioned substantially constant voltage is set as the upper limit value in most ranges. When the output current Io is zero or very small, such as when the second switch element 72 operates with a very short ON pulse width, the output voltage decreases.

  Here, the converter auxiliary power supply 86 is at least applied to the power supply line 34 of the active filter control circuit 32 at a voltage higher than at least a third upper limit value V3 described later, preferably higher than a fourth upper limit value V4 described later. High voltage can be supplied. On the other hand, the upper limit voltage that converter auxiliary power supply 86 can output is set to a voltage lower than second upper limit value V2.

  The starting circuit 38 has the same configuration as that of the power factor improving switching power supply 10 described above, but the first upper limit value V1 expressed by the equation (1) is determined by the active filter control circuit 32 and the converter control circuit 80. The first Zener diode 46 is selected so as to be higher than each starting voltage. Along with this, the second upper limit value V2 is also determined by the first Zener diode 46 as shown in equations (2) and (3).

  The series circuit of the second Zener diode 64 and the switching transistor 66 connected in parallel to the first Zener diode 46 is switched from the first transistor 44 through the first backflow prevention diode 42 when the switching transistor 66 is turned on. Thus, the upper limit value of the voltage that can be supplied to the power supply capacitor 36 is switched from the first upper limit value V1 to the third upper limit value V3.

The operation state output terminal 32b of the first control IC 32a is a terminal that inverts from a low level to a high level and outputs a constant DC voltage when the active filter control circuit 32 is activated and operated. Therefore, when the active filter control circuit 32 is activated, a constant voltage is generated at the operation state output terminal 32b of the first control IC 32a, and the base terminal of the switching transistor 66 becomes high level via the voltage dividing resistors 68a and 68b. The switching transistor 66 is turned on. When the switching transistor 66 is turned on, the second Zener diode 64 that determines the third upper limit value V3 becomes operable. The third upper limit value V3 at this time is expressed by Expression (4).
V3 = V64− (V44 + V42) (4)

When the switching transistor 66 is turned on, the upper limit value of the voltage that can be supplied from the second transistor 52 to the power supply capacitor 36 via the second backflow prevention diode 54 is also changed from the second upper limit value V2 to the fourth. To the upper limit value V4. The fourth upper limit value V4 is expressed by Expression (5), and the first, third, and fourth upper limit values V1, V3, and V4 satisfy the relationship of Expression (6).
V4 = V64− (V52 + V54) (5)
V1>V4> V3 (6)

  In the power factor improving switching power supply device 60 having the above configuration, the input is turned on with the switching transistor 66 turned off, and the active filter control circuit 32 and the converter control circuit 80 are supplied from the first transistor 44. Start by voltage.

  After the activation, when the active filter control circuit 32 starts operation, the switching transistor 66 is turned on. The fourth upper limit value V4 can be supplied from the choke auxiliary power supply 40 via the second transistor 52 and the second backflow prevention diode 54. In addition, the upper limit value of the voltage that can be supplied via the first transistor 44 and the first backflow prevention diode 42 is switched to the third upper limit value V3 that is lower than the fourth upper limit value V4. Therefore, the first transistor 44 stops its operation, so that a large loss does not occur in the first transistor 44.

  Further, if the upper limit voltage that can be supplied to the power supply lines 34 and 84 by the converter auxiliary power source 86 is set to a voltage higher than the fourth upper limit value V4, the input voltage and the output current almost change statically. In this range, the output of the converter auxiliary power supply 86 is prioritized, and the voltage supply from the choke auxiliary power supply 40 is stopped. Therefore, the predetermined loss generated in the second transistor 52 can be reduced, and the power efficiency of the entire device can be improved in almost the range where the input voltage and the output current change statically.

  Further, even after the start-up, even if voltage supply from the converter auxiliary power supply 86 or the choke auxiliary power supply 40 is temporarily stopped due to a sudden change of the load 18 or the like, at least the first transistor 44 outputs the third upper limit value V3 during that period. Therefore, the active filter control circuit 32 and the converter control circuit 80 can continue to operate without stopping.

  Further, after the start-up, for example, even if an overvoltage is generated in the load 18 and the converter control circuit 84 is continuously stopped by receiving the OV signal from the overvoltage detection circuit 78, the choke auxiliary power supply 40 passes through the second transistor 52. Thus, the voltage corresponding to the fourth upper limit value V4 is supplied, and the operation can be continued without stopping the active filter control circuit 34. At this time, since the first transistor is stopped, no large loss occurs.

  Next, a power factor improving type switching power supply 90 according to a third embodiment of the present invention will be described with reference to FIG. Here, the same components as those of the power factor improving switching power supply devices 10 and 60 described above are denoted by the same reference numerals, and description thereof is omitted. In addition to the configuration of the power factor improving switching power supply 60 described above, the power factor improving switching power supply 90 is provided between the output of the active filter 16 and the power supply line 84 of the converter control circuit 80. The cathode terminal side of the active filter control circuit 32 is connected to the connection point of the output of the start resistor 92, which is a start circuit for supplying the start voltage to the power supply line 34 of the active filter control circuit 32, and the converter auxiliary power supply 86. A connected third backflow prevention diode 94 is inserted. Further, a third Zener diode 96 having an anode terminal connected to the anode terminal of the third backflow prevention diode 94 and a cathode terminal connected to the output of the converter auxiliary power source 86 is provided. The voltage dividing resistors 68a and 68b are connected between the connection point of the third backflow prevention diode 94 and the third Zener diode 96 and the ground. Other circuit configurations are the same as those of the power factor improving switching power supply 60. Hereinafter, the newly provided configuration will be described in detail.

  The power factor improving switching power supply device 90 separates the two power supply lines 34 and 84 by a third backflow prevention diode 94 in order to facilitate the setting of the sequence at the start of the two control circuits 32 and 80. A starting resistor 92 for supplying a voltage for starting the converter control circuit 80 is provided. Further, a third Zener diode 96 is provided to facilitate the setting of the sequence when the two control circuits 32 and 80 are stopped.

  The converter auxiliary power supply 86 has at least the third upper limit value V3, the forward voltage V94 of the third backflow prevention diode 96, and the Zener voltage of the third Zener diode 96 at least on the power supply line 34 of the active filter control circuit 32. A voltage higher than V96, preferably a fourth upper limit value V4 described later, a forward voltage V94 of the third backflow prevention diode 96, and a voltage higher than the Zener voltage V96 of the third Zener diode 96 are set. Has been. On the other hand, the upper limit voltage that can be output by the converter auxiliary power source 86 is lower than a second upper limit value V2 described later, a forward voltage V94 of the third backflow prevention diode 94, and a Zener voltage V96 of the third Zener diode 96. Is set to

  The starting circuit 38 has the same configuration as that of the power factor improving switching power supply 10 described above, and the first upper limit value V1 represented by the equation (1) is higher than the starting voltage of the active filter control circuit 32. The first Zener diode 46 is selected. Along with this, the second upper limit value V2 is also determined by the first Zener diode 46 as shown in equations (2) and (3).

  The series circuit of the second Zener diode 64 and the switching transistor 66 connected in parallel to the first Zener diode 64 is switched from the first transistor 44 through the first backflow prevention diode 42 when the switching transistor 66 is turned on. Thus, the upper limit value of the voltage that can be supplied to the power supply capacitor 36 is switched from the first upper limit value V1 to the third upper limit value V3.

  The switching transistor 66 monitors the voltage generated at the anode terminal of the third Zener diode 96 via the voltage dividing resistors 68a and 68b. The switching transistor 66 is turned on when the voltage is equal to or higher than a certain voltage, and is turned off when the voltage is equal to or lower than the certain voltage. To do. A high level voltage is generated at the anode terminal of the third Zener diode 96 when a pulse voltage is generated in the tertiary winding 70c by turning the second switch element 72 on and off. When 72 is continuously turned off, a stable voltage is not generated when the pulse voltage of the tertiary winding 70c is not generated. That is, by monitoring the anode terminal of the third Zener diode 96, it is detected whether or not the converter control circuit 80 is operating, and the on / off of the switching transistor 66 is controlled. Although the same control is possible even if the third Zener diode 96 is removed by a short circuit, by providing the Zener voltage V96 of the third Zener diode 96, when the input of the switching power supply device 90 is shut off, The effect that the setting of the stop sequence of the control circuits 32 and 80 becomes easy can be obtained. In addition, the third backflow prevention diode 94 may be configured by, for example, connecting a plurality of diodes in series in the same direction, and in this case, the total value of the diode forward voltages corresponds to V94.

  When the converter control circuit 32 is activated and operated, the switching transistor 66 is turned on, and the second Zener diode 64 that determines the third upper limit value V3 becomes operable. The third upper limit value V3 is expressed by Expression (4).

  Further, when the switching transistor 66 is turned on, the upper limit value of the voltage that can be supplied from the second transistor 52 to the power supply capacitor 36 via the second backflow prevention diode 54 is also the second upper limit value V2. To the fourth upper limit value V4. The fourth upper limit value V4 is expressed by Expression (5), and the first, third, and fourth upper limit values V1, V3, and V4 satisfy the relationship of Expression (6).

  In the power factor improving switching power supply device 90 having the above configuration, the input is turned on with the switching transistor 66 turned off, and the active filter control circuit 32 is activated by the voltage supplied from the first transistor 44. Further, converter control circuit 80 is activated by the voltage supplied from activation resistor 92.

  When the converter control circuit 80 starts operating after startup, the switching transistor 66 is turned on. The fourth upper limit value V4 can be supplied from the choke auxiliary power supply 40 via the second transistor 52 and the second backflow prevention diode 54. In addition, the upper limit value of the voltage that can be supplied via the first transistor 44 and the first backflow prevention diode 42 is switched to the third upper limit value V3 that is lower than the fourth upper limit value V4. Therefore, the first transistor 44 stops its operation, so that a large loss does not occur in the first transistor 44.

  In addition, if the upper limit voltage that can be supplied to the power supply line 34 by the converter auxiliary power source 86 is set to a voltage higher than the fourth upper limit value V4, the input voltage and the output current can be almost changed in a static range. The output of the converter auxiliary power supply 86 is prioritized, and the voltage supply from the choke auxiliary power supply 40 is stopped. Therefore, the predetermined loss generated in the second transistor 52 can be reduced, and the power efficiency of the entire device can be improved in almost the range where the input voltage and the output current change statically.

  Further, even after the start-up, even if voltage supply from the converter auxiliary power supply 86 or the choke auxiliary power supply 40 is temporarily stopped due to a sudden change of the load 18 or the like, at least the first transistor 44 or the first or third transistor 44 during this period. Since the supply of the voltage corresponding to the upper limit value V1 or V3 is ensured, the active filter control circuit 32 can continue the operation without stopping.

  Further, after the start-up, for example, even if an overvoltage is generated in the load 18 and the converter control circuit 80 is continuously stopped by receiving the OV signal from the overvoltage detection circuit 78, the choke auxiliary power supply 40 passes through the second transistor 52. Thus, the voltage corresponding to the second upper limit value V2 is supplied, and the active filter control circuit 34 can continue the operation without stopping. At this time, since the first transistor is stopped, no large loss occurs.

  Next, a power factor improving switching power supply apparatus 100 according to a fourth embodiment of the present invention will be described with reference to FIG. Here, the same components as those of the power factor improving switching power supply 10, 60, 90 described above are denoted by the same reference numerals, and the description thereof is omitted. In addition to the configuration of the power factor improving switching power supply 90 described above, the power factor improving switching power supply 100 has an anode terminal at the connection point between the output of the converter auxiliary power supply 86 and the power supply line 84 of the converter control circuit 80. A fourth backflow prevention diode 102 connected to the output side of the auxiliary power supply 86 and having a cathode terminal connected to the converter control circuit 80 side is inserted, and further, between the cathode terminal of the fourth backflow prevention diode 102 and the ground. A capacitor 104 is connected. Other circuit configurations are the same as those of the power factor improving switching power supply 90.

  The operation of supplying power to the active filter control circuit 34 by the power factor improving switching power supply apparatus 100 is the same as that of the power factor improving switching power supply apparatus 90. Furthermore, the power factor improvement type switching power supply device 100 is characterized in that the starting characteristic and the stopping characteristic of the converter control circuit can be adjusted separately.

  When the converter control circuit 84 is activated, the smoothing capacitor included in the converter auxiliary power supply 86 is disconnected by the fourth backflow prevention diode 102. Therefore, the activation characteristic of the converter control circuit 84 is that the capacitor 104 having a relatively small capacity is used. The starting resistance 92 can be set. Further, when converter control circuit 84 is stopped, the stop characteristic can be set by a relatively large capacity capacitor obtained by synthesizing smoothing capacitor built in converter auxiliary power supply 86 and capacitor 104. As a result, it is possible to easily set the start and stop sequences of the control circuits 32 and 80, and to easily apply the intermittent operation mode to the overcurrent protection drooping characteristics of the DC-DC converter 62. Obtainable.

  In addition, this invention is not limited to the said embodiment, You may comprise the changeover switch connected in series with the 2nd Zener diode by electronic switch elements other than a transistor element, a relay, etc.

  Further, the changeover switch only needs to be controlled to be turned on when the active filter control circuit or the converter control circuit is in operation, whether or not there is a voltage generated from the operation state output terminal of each control IC, and the switch element 22 , 72 may be controlled by detecting the presence / absence of a driving pulse voltage for driving on / off, and the presence / absence of a pulse voltage of windings 70a, 70b, 70c of transformer 70.

10, 60, 90, 100 Power factor improving type switching power supply 16 Active filter 20 Boosting choke 22 First switching element 32 Active filter control circuit 32a First control IC
32b Operating state output terminal 34 Power line 36 Power supply capacitor 40 Choke auxiliary power supply 42 First backflow prevention diode 44 First transistor 46 First Zener diode 48 Choke auxiliary winding 50 Rectifier circuit 52 Second transistor 54 Second Reverse current prevention diode 62 DC-DC converter 64 second Zener diode 66 switching transistors 68a and 68b voltage dividing resistor 70 transformer 70a primary winding 70b secondary winding 70c tertiary winding 72 second switching element 74 output rectifying and smoothing circuit 80 Converter control circuit 80a Second control IC
84 Power supply line 86 Converter auxiliary power supply 88 Auxiliary rectifying / smoothing circuit 92 Starting resistor 94 Third backflow prevention diode 96 Third zener diode 102 Fourth backflow prevention diode 104 Capacitor

Claims (5)

A step-up chopper type active filter that has a step-up choke and a first switching element, converts the input full-wave rectified voltage into a DC voltage, and outputs it;
An active filter control circuit for driving on and off the first switching element and controlling the power factor improvement operation of the active filter;
A power supply capacitor connected between the power supply line of the active filter control circuit and the ground;
A first transistor that is an N-channel MOS FET having a drain terminal connected to the input of the active filter and a source terminal connected to the power supply capacitor via a first backflow prevention diode;
The cathode terminal is connected to the gate terminal of the first transistor, the anode terminal is connected to the ground, and the upper limit of the voltage that can be supplied from the first transistor to the power supply capacitor via the first backflow prevention diode A first Zener diode for determining a first upper limit value,
A bias resistor connected between an input of the active filter and a cathode terminal of the first Zener diode, and supplying a bias current to the first Zener diode to generate a Zener voltage;
A choke auxiliary power source provided with the choke auxiliary winding provided in the boost choke and a rectifier circuit that rectifies the generated voltage, and a choke auxiliary power source that outputs the rectified voltage generated by the rectifier circuit toward the power supply capacitor. In the rate improvement type switching power supply,
The drain terminal is connected to the output of the choke auxiliary power supply, the source terminal is connected to the power supply capacitor via a second backflow prevention diode, the gate terminal is connected to the cathode terminal of the first Zener diode, A second transistor which is an N-channel MOS FET provided so as to be able to output a predetermined voltage from the source terminal;
The first upper limit value is higher than the activation start voltage of the active filter control circuit,
The upper limit value of the voltage that can be supplied from the second transistor to the power supply capacitor via the second backflow prevention diode, and the second upper limit value determined by the first Zener diode is Higher than the first upper limit,
The power factor improvement type switching power supply device, wherein the choke auxiliary power supply is provided so that a voltage higher than a Zener voltage of the first Zener diode can be output after the active filter control circuit is activated. At the output end of the active filter,
A second switching element that generates an alternating voltage by intermittently turning on and off the output voltage of the active filter;
A transformer provided with a primary winding to which the AC voltage is applied and a secondary winding magnetically coupled to the primary winding;
An output rectifying / smoothing circuit that rectifies and smoothes a voltage generated in the secondary winding to generate a DC voltage and supplies an output voltage to a load;
A converter control circuit that performs on / off driving of the second switching element and performs stabilization control of the output voltage;
A converter auxiliary power supply comprising a tertiary winding provided in the transformer and an auxiliary rectifying / smoothing circuit for rectifying and smoothing the generated voltage, and supplying the power by connecting the output of the auxiliary rectifying / smoothing circuit to the power supply line of the converter control circuit When,
A DC-DC converter with
The output of the converter auxiliary power supply is connected to the power supply line of the active filter control circuit,
The upper limit value of the voltage that can be supplied from the first transistor to the power supply capacitor via the first backflow prevention diode, and the first upper limit value determined by the first Zener diode is Higher than each starting voltage of the active filter control circuit and the converter control circuit,
In parallel with the first Zener diode, a series circuit of a second Zener diode and a changeover switch arranged in the same direction as the first Zener diode is connected,
When the changeover switch is turned on, the upper limit value of the voltage that can be supplied from the first transistor to the power supply capacitor via the first backflow prevention diode is from the first upper limit value to the second value. Switch to the third upper limit determined by the Zener diode of
The third upper limit value is lower than the first upper limit value and higher than each stop voltage of the active filter control circuit and the converter control circuit,
The voltage that can be output by the converter auxiliary power source is lower than the second upper limit value and higher than the third upper limit value,
2. The power factor improving type switching power supply device according to claim 1, wherein the changeover switch is controlled to be turned on when an active filter control circuit or a converter control circuit is activated and operates. At the output end of the active filter,
A first switching element that generates an alternating voltage by intermittently turning on and off the output voltage of the active filter;
A transformer provided with a primary winding to which the AC voltage is applied and a secondary winding magnetically coupled to the primary winding;
An output rectifying and smoothing circuit that rectifies and smoothes a voltage generated in the secondary winding to generate a DC voltage and supplies an output voltage to a load;
A converter control circuit that performs on / off driving of the second switching element and performs stabilization control of the output voltage;
A starting circuit that is provided between the output of the active filter and a power supply line of the converter control circuit, and supplies a starting voltage to the converter control circuit;
A converter auxiliary power supply comprising a tertiary winding provided in the transformer and an auxiliary rectifying / smoothing circuit for rectifying and smoothing the generated voltage, and supplying the power by connecting the output of the auxiliary rectifying / smoothing circuit to the power supply line of the converter control circuit When,
A DC-DC converter with
The cathode terminal is connected to the power line side of the active filter control circuit and the anode terminal is connected to the output side of the converter auxiliary power source between the power line of the active filter control circuit and the output of the converter auxiliary power source. Three backflow prevention diodes are inserted,
In parallel with the first Zener diode, a series circuit of a second Zener diode and a changeover switch arranged in the same direction as the first Zener diode is connected,
When the change-over switch is turned on, the upper limit value of the voltage that can be supplied from the first transistor to the power supply capacitor via the first backflow prevention diode is from the first upper limit value to the second value. Switch to the third upper limit determined by the Zener diode of
The third upper limit value is lower than the first upper limit value and higher than the stop voltage of the active filter control circuit,
The voltage that the converter auxiliary power supply can output is lower than the total value of the forward voltage of the third backflow prevention diode and the second upper limit value, and the forward voltage of the third backflow prevention diode. Higher than the sum of the third upper limit value and
2. The power factor improving type switching power supply device according to claim 1, wherein the changeover switch is controlled to be turned on when the active filter control circuit or the converter control circuit is activated and operates. A third terminal in which the cathode terminal is connected to the output side of the converter auxiliary power supply and the anode terminal is connected to the third backflow prevention diode side at the connection point between the third backflow prevention diode and the output of the converter auxiliary power supply. Zener diode is inserted,
The voltage that the converter auxiliary power supply can output is lower than the total value of the Zener voltage of the third Zener diode, the forward voltage of the third backflow prevention diode, and the second upper limit value, and 4. The power factor improving switching power supply device according to claim 3, wherein the power factor improving switching power supply device is set higher than a total value of a Zener voltage of a third Zener diode, a forward voltage of the third backflow prevention diode, and the third upper limit value. A fourth reverse flow in which the anode terminal is connected to the output side of the converter auxiliary power supply and the cathode terminal is connected to the converter control circuit side at the connection point between the output of the converter auxiliary power supply and the power supply line of the converter control circuit Prevention diode is inserted,
5. The power factor improving type switching power supply device according to claim 4, wherein a capacitor is connected between the cathode terminal of the fourth backflow prevention diode and the ground.

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