JP2009142020A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device wherein excessive voltage is not applied to between the ends of a switching element of a boost circuit in whatever phase alternating-current voltage is. <P>SOLUTION: Before rectified voltage from a rectifying circuit 2 reaches a certain level and MOSFET 5 starts operation, a rush current prevention circuit 31 turns off a thyristor 20. Even though a rush current occurs immediately after the power is turned on, therefore, the rush current can be effectively limited by a rush current prevention resistor 21. When the rectified voltage thereafter reaches the certain level and the MOSFET 5 starts operation and driving voltage for turning on the thyristor 20 is given by induced voltage from auxiliary winding 12, the following takes place: a holding circuit 36 utilizes the induced voltage from the auxiliary winding 12 to keep the thyristor 20 on regardless of fluctuation in the rectified voltage. For this reason, a surge current to the power supply device goes through the thyristor 20 and voltage rise in the rush current prevention resistor 21 due to surge current can be avoided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply device in which an auxiliary winding is wound around a choke coil of a booster circuit, and an inrush current is prevented by using a voltage generated in the auxiliary winding, and in particular, a power supply device for improving lightning surge resistance About.

  In general, as a power supply device of this type, for example, Patent Document 1 discloses a rectifier circuit that rectifies an AC input voltage, a booster circuit that obtains a boosted DC voltage that is higher than the rectified voltage from the rectifier circuit, and a switch element. A device including a parallel circuit with an inrush current preventing resistor and including an inrush current preventing circuit for suppressing an inrush current when power is turned on is known.

  In particular, there is another patent document 2 or patent in which an auxiliary winding is wound around the choke coil of the booster circuit and the switch element of the inrush current prevention circuit is controlled using the voltage generated in the auxiliary winding. It is disclosed in Document 3.

  FIG. 4 shows an example of such a power supply device in the prior art. In the figure, reference numeral 1 is an AC power supply for supplying an AC input voltage to the power supply device, and 2 is a rectifier circuit for full-wave rectification of the AC input voltage from the AC power supply 1, which includes four known bridge-connected diodes. It is comprised by 2A-2D. 3 is a booster circuit that boosts the rectified output from the rectifier circuit 2 and supplies a DC voltage to the DC-DC converter 9 in the subsequent stage. This circuit comprises a series circuit of the choke coil 4 and the MOSFET 5 serving as a switching element. A series circuit of a diode 6 and a smoothing capacitor 7 is connected between the output terminals of the rectifier circuit 2 and connected between both ends of the MOSFET 5, that is, between the drain and source. Although not shown here, the booster circuit 3 is provided with control means for supplying a drive signal to the gate of the MOSFET 5, and this control means receives the rectified voltage from the rectifier circuit 2, On / off of the MOSFET 5 is controlled so that the input current waveform to the booster circuit 3 becomes a sine wave. That is, the booster circuit 3 here has a function as a power factor correction circuit that supplies a DC voltage with a high power factor to the DC-DC converter 9. The DC-DC converter 9 as a voltage converter receives the DC voltage from the booster circuit 3, converts it to an appropriate DC output voltage, and supplies it to a load (not shown).

  Reference numeral 11 denotes an inrush current prevention circuit for preventing an inrush current to the booster circuit 3 and thus the DC-DC converter 9 when the power is turned on. The inrush current prevention circuit 11 includes an auxiliary winding 12 that is magnetically coupled to the choke coil 4 of the booster circuit 3, resistors 13, 14, and 15, capacitors 16 and 17, and backflow prevention diodes 18 and 19; The thyristor (SCR) 20 as a switching element and an inrush current preventing resistor 21 as a current limiting element are connected to one end of the auxiliary winding (dot side terminal) and one end of the resistors 13 and 15 and the capacitor 17 respectively. The anode of the diode 18 is connected to the other end of the resistor 13, the anode of another diode 19 is connected to the cathode of the diode 18, and the connection point between the diodes 18 and 19 and the other end of the auxiliary winding (non-dot side terminal) ) And the capacitor 16 are inserted and connected. Further, one end of the resistor 14 is connected to the cathode of the diode 19, the gate of the thyristor 20 is connected in common to the other end of the resistor 14, and a parallel circuit of the resistor 15 and the capacitor 17 provided as a gate absorber of the thyristor 20 is The thyristor 20 is connected between the gate and the cathode, and the anode and the cathode which are both ends of the thyristor 20 are inserted and connected to a voltage supply line extending from the rectifier circuit 2 to the DC-DC converter 9. Between the cathode and the cathode, an inrush current preventing resistor 21 is connected in parallel.

Immediately after the power is turned on, the AC input voltage from the AC power source 1 is full-wave rectified by the rectifier circuit 2, and the rectified voltage is applied to the choke coil 4 of the booster circuit 3 and the drive voltage is supplied to the MOSFET 5. When the operation is started, a voltage proportional to the applied voltage of the choke coil 4 is induced across the auxiliary winding 12. Thereby, a current flows directly from the auxiliary winding 12 to the gate of the thyristor 20. Therefore, until the rectified voltage reaches a certain level and the MOSFET 5 starts to operate, a current sufficient to turn on the thyristor 20 does not flow to the gate, and the thyristor 20 is turned off. The inrush current is limited by the inrush current preventing resistor 21. Thereafter, when the rectified voltage reaches a certain level or more and the MOSFET 5 starts to operate, a current sufficient to turn on the thyristor 20 flows to the gate, the inrush current preventing resistor 21 is short-circuited, and the boost circuit 3 passes through the thyristor 20. An input current flows through the DC-DC converter 9.
JP 10-155272 A Utility Model Registration No. 2600225 JP 2006-121808 A

  As described above, the power supply device shown in FIG. 4 receives the rectified voltage from the rectifier circuit 2 and starts the operation of the booster circuit 3. Then, a current flows from the auxiliary winding 12 to the gate of the thyristor 20, and after a predetermined time. The circuit configuration is such that the thyristor 20 is turned on.

  However, when the phase of the AC input voltage is close to 0 ° or 180 °, the level of the rectified voltage is reduced to near 0 V, and the voltage induced in the auxiliary winding 12 is almost eliminated. The current flowing through the gate cannot be held, and eventually the thyristor 20 of the inrush current prevention circuit 11 is turned off. This state is shown in the waveform diagram of FIG. 5, and the gate voltage Vg of the thyristor 20 shown in the upper stage is lowered when the phase of the AC input voltage Vac below it is around 0 ° or 180 °. In the thyristor 20, a certain off section Toff is repeatedly generated.

  At the timing of this off section Toff, the thyristor 20 is in an off state, so that a steady current flows into the smoothing capacitor 7 of the booster circuit 3 via the inrush current preventing resistor 21 and between both ends of the inrush current preventing resistor 21. A voltage is generated by integrating the resistance value of the inrush current preventing resistor 21 and the steady current. The voltage Vb generated between both ends of the inrush current preventing resistor 21 during the steady operation is shown in the lower part of FIG.

  Further, when a surge voltage is applied to the power supply device in the off section Toff, the surge current flows into the smoothing capacitor 7 of the booster circuit 3 via the inrush current prevention resistor 21 and is inserted between both ends of the inrush current prevention resistor 21. Generates a voltage obtained by integrating the resistance value of the inrush current preventing resistor 21 and the surge current. The voltage Vb between both ends of the inrush current preventing resistor 21 at this time is much larger than that in the steady operation shown in FIG. 5, and the between the drain and source of the MOSFET 5 incorporated in the booster circuit 3 is for preventing inrush current. A voltage obtained by adding the voltage across both ends of the smoothing capacitor 7, that is, the boosted voltage and the voltage drop of the diode 6, to the voltage Vb between both ends obtained by integrating the resistance value of the resistor 21 and the surge current is generated, and the rated voltage of the MOSFET 5 is obtained. There is a risk of exceeding.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply device in which an excessive voltage is not applied between both ends of a switching element of a booster circuit regardless of the phase of an AC input voltage.

  A power supply device according to claim 1 of the present invention includes a rectifier circuit that rectifies an AC input voltage, a booster circuit that includes a choke coil and a switching element for boosting a rectified voltage from the rectifier circuit, and the choke coil. An auxiliary winding provided in the auxiliary winding, a switching element driven by an induced voltage from the auxiliary winding, and a current limiting element connected between both ends of the switching element, and the rectified voltage applied to the choke coil is at a constant level. And an inrush current prevention circuit that turns off the switch element until the booster circuit starts to operate. In the power supply device, the rectified voltage reaches a certain level, the booster circuit starts operating, and the switch A holding circuit for holding the switch element in an on state by an induced voltage from the auxiliary winding after the element is turned on; .

  According to the first aspect of the present invention, even if an inrush current occurs immediately after the power is turned on, the inrush current prevention circuit turns off the switch element until the rectified voltage from the rectifier circuit reaches a certain level and the booster circuit starts operating. Therefore, the inrush current can be effectively limited by the current limiting element. After that, when the rectified voltage reaches a certain level and the booster circuit starts to operate, when the drive voltage for turning on the switch element is given by the induced voltage from the auxiliary winding, the holding circuit is not affected by the fluctuation of the rectified voltage. Since the switching element is kept on using the induced voltage from the auxiliary winding, even if a surge current flows into the power supply device, the surge current passes through the switching element, not the current limiting element, and becomes a surge current. It is possible to avoid an increase in the voltage of the current limiting element due to this. Therefore, it is possible to provide a power supply device in which an excessive voltage is not applied across the switching elements of the booster circuit regardless of the phase of the AC input voltage.

  Hereinafter, preferred embodiments of a power supply device according to the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same location as FIG. 4 shown in the prior art example, and description of a common location is abbreviate | omitted as much as possible to avoid duplication.

  FIG. 1 shows a circuit diagram of a power supply apparatus as a basic configuration in the first embodiment of the present invention. The difference from the conventional example is the configuration of the inrush current prevention circuit 31. Here, the auxiliary winding 12, the resistor 13, the resistor 15, the capacitor 16, the capacitor 17, the diode 18, the diode 19, the thyristor 20, and the inrush current prevention are described here. In addition to the resistor 21, a MOSFET 32 serving as a switch element, resistors 33 and 34, and a capacitor 35 are provided. In each of these elements, the gate of the MOSFET 32 is connected to the cathode of the diode 19, the gate of the thyristor 20 is connected to the source of the MOSFET 32, and the resistor 34 is connected to the drain of the MOSFET 32. A parallel circuit of a resistor 33 and a capacitor 35 is connected between one end of the auxiliary winding 12 and the cathode of the diode 19. Other configurations are the same as those in FIG. 4 shown in the conventional example.

  In the inrush current prevention circuit 11 of the conventional example, the cathode of the diode 19 is directly connected to the gate of the thyristor 20 via the resistor 14. However, the inrush current prevention circuit 31 of this embodiment has the cathode of the diode 19 and the thyristor 20. A holding circuit 36 that keeps the thyristor 20 on is provided between the gate and the gate. The holding circuit 36 includes a MOSFET 32, resistors 33 and 34, and a capacitor 35. The rectified voltage from the rectifier circuit 2 is applied to the choke coil 4, and a positive induced voltage is generated at one end of the auxiliary winding 12. Then, charges are stored in the capacitor 35, and when the induced voltage reaches a certain level, the MOSFET 32 is turned on and the thyristor 20 is turned on. Thereafter, the gate voltage of the MOSFET 32 is held by the charge stored in the capacitor 35. However, the thyristor 20 is kept on regardless of the phase of the input AC voltage.

  Next, the operation of the above configuration will be described. Immediately after the power is turned on, the AC input voltage from the AC power source 1 is full-wave rectified by the rectifier circuit 2, and the rectified voltage is applied to the choke coil 4 of the booster circuit 3. . When the rectified voltage reaches a certain level and the MOSFET 5 starts to operate, a voltage proportional to the voltage applied to the choke coil 4 is induced across the auxiliary winding 12, and this induced voltage accumulates electric charge in the capacitor 35. The gate of the MOSFET 32 is charged. Eventually, as the gate potential of the MOSFET 32 rises, the MOSFET 32 is turned on, and when a current flows to the gate of the thyristor 20 through the resistor 34 and the MOSFET 32, the thyristor 20 is also turned on and between both ends of the inrush current preventing resistor 20 However, since the thyristor 20 is off until then, the transient inrush current that tries to enter the booster circuit 3 is limited by the inrush current preventing resistor 20.

  After that, when the phase of the AC input voltage becomes near 0 ° or 180 °, the level of the rectified voltage decreases to near 0V, and the voltage induced in the auxiliary winding 12 is almost eliminated, but is stored in the capacitor 35 until then. The gate voltage of the MOSFET 32 is maintained at a level at which the MOSFET 32 is continuously turned on by the electric charge, and the thyristor 20 continues to be kept on. Therefore, unless the supply of the AC input voltage is interrupted, the thyristor 20 is always on regardless of the phase of the AC input voltage, and the input current flows from the booster circuit 3 to the DC-DC converter 9 through the thyristor 20.

  Further, even if a surge voltage is applied from the AC power supply 1 to the power supply device in this state, the surge current does not flow into the inrush current prevention resistor 21 but flows into the smoothing capacitor 7 through the thyristor 20. Therefore, a voltage obtained by adding the voltage drop of the diode 6 to the voltage across the smoothing capacitor 7 is generated between the drain and source of the MOSFET 5 incorporated in the booster circuit 3, and the drain-source voltage of the MOSFET 5 increases. Can be suppressed. At the same time, an increase in voltage between the anode and cathode of the thyristor 20 can be suppressed.

  As described above, in this embodiment, the rectifier circuit 2 that rectifies the AC input voltage and the choke coil 4 and the MOSFET 5 that is a switching element are connected to the output terminal of the rectifier circuit 2 in order to boost the rectified voltage from the rectifier circuit 2. A chopper type booster circuit 3 connected between the auxiliary winding 12 provided in the choke coil 4, a thyristor 20 as a switching element driven by an induced voltage from the auxiliary winding 12, and between both ends of the thyristor 20. A rush current preventing resistor 21 as a current limiting element connected between a certain anode and cathode is provided, and the thyristor 20 is operated until the rectified voltage applied to the choke coil 4 reaches a certain level and the MOSFET 5 of the booster circuit 3 starts operating. In the power supply device including the inrush current prevention circuit 31 that is turned off, the rectified voltage from the rectifier circuit 2 becomes a constant level. And, MOSFET 5 is started to operate, after the thyristor 20 is turned on, and includes the inrush current preventing circuit 31 a holding circuit 36 which utilizes the induced voltage from the auxiliary winding 12 for holding the thyristor 20 in the ON state.

  In this case, even if an inrush current occurs immediately after the power is turned on, the inrush current prevention circuit 31 turns off the thyristor 20 until the rectified voltage from the rectifier circuit 2 reaches a certain level and the MOSFET 5 starts to operate. The inrush current can be effectively limited by the inrush current preventing resistor 21. After that, when the rectified voltage reaches a certain level, the MOSFET 5 starts to operate, and a driving voltage for turning on the thyristor 20 is given by the induced voltage from the auxiliary winding 12, the holding circuit 36 does not depend on the fluctuation of the rectified voltage, Since the induced voltage from the auxiliary winding 12 is used to keep the thyristor 20 in the ON state, even if a surge current flows into the power supply device, the surge current passes through the thyristor 20 instead of the inrush current preventing resistor 21 and is An increase in voltage of the inrush current preventing resistor 21 due to the current can be avoided. Therefore, it is possible to provide a power supply device in which an excessive voltage is not applied between both ends of the MOSFET 5 of the booster circuit 3 regardless of the phase of the AC input voltage.

  FIG. 2 is a circuit diagram as an actual example of the power supply device in the second embodiment of the present invention. In the figure, the difference from the first embodiment is that a constant voltage circuit composed of resistors 41 and 42 and a Zener diode 43 is interposed between the cathode of the diode 19 and the gate of the MOSFET 32. Here, a series circuit of resistors 41 and 42 is connected between the cathode of the diode 19 and one end of the auxiliary winding 12, and the gate of the MOSFET 32 is connected to the connection point of the resistors 41 and 42. Further, a Zener diode 43 is connected between both ends of a resistor connected between the gate of the MOSFET 32 and one end of the auxiliary winding 12. Other configurations and operations are as described in the first embodiment.

  In this example, the gate-source voltage of the MOSFET 32 is kept constant by the Zener diode 43. Therefore, the MOSFET 32 can be kept stably in the on state as compared with the first embodiment, and the thyristor 20 is surely kept in the on state after the rectified voltage from the rectifier circuit 2 reaches a certain level. Is possible.

  FIG. 3 is a circuit diagram as an actual example of the power supply device according to the third embodiment of the present invention. In the figure, the second embodiment differs from the second embodiment in that the parallel circuit of the thyristor 20 and the inrush current preventing resistor 21 is not between the cathode of the diode 6 constituting the booster circuit 3 and one end of the capacitor 7 but rectified. This is in the point of being inserted and connected between the output end of the circuit 2 and the choke coil 4. Other configurations and operations are the same as described in the first and second embodiments.

  In this case, since the parallel circuit of the thyristor 20 and the inrush current prevention resistor 21 is provided in the previous stage of the booster circuit 3, the inrush current generated immediately after the power is turned on is prevented from entering the booster circuit 3 with certainty. Can do.

  In addition, this invention is not limited to the said Example, It can change in the range which does not deviate from the meaning of this invention. For example, a transistor or the like may be used as the switching element in addition to the MOSFET 5, and a triac (bidirectional thyristor) may be used as the switching element in addition to the thyristor 20. Furthermore, the rectifier circuit 2 is not limited to the full-wave rectifier circuit as in the embodiment, and a half-wave rectifier circuit, a voltage doubler rectifier circuit, or the like may be applied. Further, as the power supply device, the DC-DC converter 9 that outputs a stable DC voltage is incorporated in the above-described embodiment. However, for example, a DC-AC converter that outputs an AC voltage may be incorporated instead. The output may be directly used as the output voltage of the power supply device.

It is a circuit diagram which shows the power supply device in 1st Example of this invention. It is a circuit diagram which shows the example of a real machine of the power supply device in 2nd Example of this invention. It is a circuit diagram which shows the example of a real machine of the power supply device in 3rd Example of this invention. It is a circuit diagram which shows the power supply device of a prior art example. It is a wave form diagram which shows the operation state of each part same as the above.

Explanation of symbols

2 Rectifier circuit 3 Booster circuit 4 Choke coil 5 MOSFET (switching element)
12 Auxiliary winding 20 Thyristor (switch element)
21 Inrush current prevention resistor 31 Inrush current prevention circuit 36 Holding circuit

Claims (1)

A rectifier circuit for rectifying an AC input voltage;
A step-up circuit including a choke coil and a switching element to step up a rectified voltage from the rectifier circuit;
An auxiliary winding provided in the choke coil, a switch element driven by an induced voltage from the auxiliary winding, and a current limiting element connected between both ends of the switch element, and the rectified voltage applied to the choke coil is In a power supply device comprising an inrush current prevention circuit that turns off the switch element until reaching a certain level and the booster circuit starts to operate,
A holding circuit for holding the switch element in an ON state by an induced voltage from the auxiliary winding after the rectified voltage reaches a certain level, the booster circuit starts operating, and the switch element is turned on; A featured power supply.