JP2015139266A - Dc/dc converter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress oscillation of an output side circuit in the case of an adaptive change in time ratio with load fluctuation in a DC/DC converter circuit.SOLUTION: The DC/DC converter circuit 10 includes: an input side circuit 14 having a power supply 20; and an output side circuit 16 for receiving and supplying to a load 8 energy supplied from the input side circuit 14 by magnetic coupling. The input side circuit 14 supplies energy to the output side circuit 16 on the basis of a time ratio D variable with fluctuation of the load 8. A circuit constant of at least one of the input side circuit 14 and the output side circuit 16 is set such that an input side resonance frequency fis not lower than a predetermined frequency higher than an output side resonance frequency f.

Description

  The present invention relates to a DCDC converter circuit.

  The DCDC converter circuit includes an input side circuit having an input side coil for storing electric power supplied from a power source as electromagnetic energy, and an output side circuit having an output side coil magnetically coupled to the input side coil. When the load connected to the output side circuit fluctuates, in order to change the output voltage according to this fluctuation, the time ratio of the first switch element of the input side circuit is changed. Then, the resonance frequency of the input side circuit varies. When the resonance frequency of the input side circuit approaches the vicinity of the resonance frequency of the output side circuit, the resonance frequency component of the input side circuit is amplified by the output side circuit, and vibration is superimposed on the output of the output side circuit.

  As a technique related to the present invention, for example, Patent Document 1 discloses a DCDC converter circuit including an input side capacitor connected in parallel to an input side coil and a second switch element connected in series to the input side capacitor. It is disclosed. When the first switch element is on, the second switch element is turned off to charge the input side capacitor while accumulating energy in the input side coil. When the first switch element is off, the second switch element is turned on. Thus, a configuration is disclosed in which current is passed from the input side capacitor to the input side coil, thereby reversing the excitation. Furthermore, a configuration is disclosed in which a resistor is inserted in series with the input-side capacitor to secure a phase margin of the transfer function of the DCDC converter circuit, thereby preventing the input-side circuit from oscillating.

JP 2002-199721 A

  In the configuration of Patent Document 1, a configuration is disclosed in which a resistor is inserted in series with the input-side capacitor to provide a phase margin of the DCDC converter circuit. However, when the load connected to the output-side circuit fluctuates, No consideration is given to the oscillation of the output voltage when changing the duty ratio of the first switch element of the input side circuit.

  An object of the present invention is to provide a DCDC converter circuit that suppresses vibration of an output side circuit when responding by changing a duty ratio in accordance with a change in load.

  A DCDC converter circuit according to the present invention is a DCDC converter circuit comprising an input side circuit having a power source and an output side circuit that receives energy supplied from the input side circuit by magnetic coupling and supplies the energy to a load. The side circuit supplies the energy to the output side circuit based on a duty ratio D that is changed in accordance with a change in the load, and at least one circuit constant of the input side circuit and the output side circuit is the input constant The input side resonance frequency of the side circuit is set to be equal to or higher than a predetermined frequency exceeding the output side resonance frequency of the output side circuit.

Further, in the DCDC converter circuit according to the present invention, the input side circuit is provided with a power source, an input side coil provided in parallel to the power source, and in series with the input side coil, and the time ratio D in one cycle. A first switch element that is turned on in an on period determined by the time ratio D and turned off in an off period determined by the duty ratio D, an input side capacitor provided in parallel with the input side coil, and provided in series with the input side capacitor, A second switch element that is turned off while the first switch element is turned on and turned on while the first switch element is turned off. An output side coil to be coupled; a smoothing capacitor connected in series to the output side coil; a smoothing coil connected in series to the output side coil and the smoothing capacitor; A, the input-side resonant frequency, the value L _I of the input-side coil, defined based on the value C _I and the time ratio D of the input side capacitor, the output-side resonant frequency, the value of the smoothing coil Preferably, it is determined based on L _O and the value C _{O of the} smoothing capacitor.

  In the DCDC converter circuit according to the present invention, it is preferable that the predetermined frequency is twice the output side resonance frequency.

  With the above configuration, at least one circuit constant of the input side circuit and the output side circuit is set so that the input side resonance frequency of the input side circuit is equal to or higher than a predetermined frequency exceeding the output side resonance frequency of the output side circuit. Thereby, even when the load connected to the output side circuit fluctuates, a sufficient difference between the input side resonance frequency of the input side circuit and the output side resonance frequency of the output side circuit can be secured. Therefore, the vibration of the output side circuit can be suppressed when responding by changing the duty ratio in accordance with the change of the load.

1 is a circuit diagram of a DCDC converter circuit according to an embodiment of the present invention. In the DCDC converter circuit of a prior art, it is a circuit characteristic view when a horizontal axis is a time ratio and a vertical axis is a resonance frequency of an input side circuit. In the DCDC converter circuit of a prior art, it is a circuit characteristic view when a horizontal axis is a frequency and a vertical axis is a gain of an output side circuit. In the DCDC converter circuit of the prior art, the horizontal axis is time, the vertical axis is output voltage, duty ratio D, and load Δ variation ΔI _L. FIG. In the DCDC converter circuit of embodiment which concerns on this invention, it is a circuit characteristic figure when a horizontal axis is a time ratio and a vertical axis | shaft is made into the resonant frequency of the input side circuit. In the DCDC converter circuit of embodiment which concerns on this invention, it is a circuit characteristic figure when a horizontal axis is a frequency and a vertical axis | shaft is made into the gain of an output side circuit. In the DCDC converter circuit according to the embodiment of the present invention, the horizontal axis represents time, and the vertical axis represents output voltage, duty ratio D, and load 8 variation ΔI _L.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. Also, in the following, corresponding elements in all drawings are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a circuit diagram of the DCDC converter circuit 10. The DCDC converter circuit 10 is a circuit that includes an input side circuit 14, an output side circuit 16 that receives energy from the input side circuit 14 by magnetic coupling, and supplies the energy to the load 8, and a control circuit 18. The load 8 is not a component of the DCDC converter circuit 10, but is, for example, an air conditioner or an AV device mounted on a car.

  The input side circuit 14 is a circuit that is magnetically coupled to the output side circuit 16. The input side circuit 14 includes a power source 20, an input side coil 22, a first switch element 24, and a clamp circuit 25. The input side circuit 14 has a function of orthogonally transforming the power supplied from the power supply 20 and supplying the orthogonally transformed power to the output side circuit 16.

  The power source 20 is a direct current source having one end connected to one end of the input side coil 22 and one end of the clamp circuit 25 and the other end connected to the other end of the first switch element 24. As the power source 20, for example, a lithium ion secondary battery having a negative electrode made of a carbon material, an electrolytic solution for moving lithium ions, and a positive electrode active material capable of reversing lithium ions can be used. .

  The input side coil 22 is a reactor having one end connected to one end of the power supply 20 and one end of the clamp circuit 25, and the other end connected to one end of the first switch element 24 and the other end of the clamp circuit 25. .

  The first switch element 24 is a transistor having one end connected to the other end of the input side coil 22 and the other end of the clamp circuit 25 and the other end connected to the other end of the power supply 20. The first switch element 24 is, for example, an IGBT (Insulated Gate Bipolar Transistor). The first switch element 24 is on / off controlled by the control circuit 18.

Here, the ratio of the ON period in one cycle T of the ON / OFF control of the first switch element 24 is a time ratio D. The first switch element 24 is ON / OFF controlled so that a desired output voltage V _O is output from the output side circuit 16 by changing the duty ratio D according to the variation of the load 8.

  The clamp circuit 25 is a circuit that prevents the voltage across the input side coil 22 from exceeding a predetermined voltage, and is an active clamp that is clamped only at a desired timing using the first switch element 24 and the second switch element 26. Circuit.

  Here, when the first switch element 24 is on, the second switch element 26 is turned off, and the electric power supplied from the power source 20 is accumulated as electromagnetic energy in the input side coil 22 while the parasitic diode of the second switch element is The input side capacitor 28 is charged via Then, when the first switch element 24 is off, the second switch element 26 is turned on, and current is passed from the input side capacitor 28 to the input side coil 22 to reverse the excitation.

  The clamp circuit 25 has one end connected to one end of the power supply 20 and one end of the input side coil 22, and the other end connected to the other end of the input side coil 22 and one end of the first switch element 24. The clamp circuit 25 includes a second switch element 26 and an input side capacitor 28.

  The second switch element 26 is a transistor having one end connected to the other end of the input side capacitor 28 and the other end connected to the other end of the input side coil 22 and one end of the first switch element 24. As the second switch element 26, for example, an IGBT is used. The second switch element 26 is on / off controlled by the control circuit 18.

  The input side capacitor 28 is a capacitor having one end connected to one end of the power supply 20 and one end of the input side coil 22 and the other end connected to one end of the second switch element 26.

  The output side circuit 16 includes an output side coil 30, a rectifier circuit 32, and a smoothing circuit 34. The output side circuit 16 is a circuit that supplies the load 8 with power that has been rectified and smoothed from the power supplied from the input side circuit 14.

  The output side coil 30 is a reactor that is magnetically coupled to the input side coil 22. The output side coil 30 has one end connected to the anode terminal of the first diode 36 and the other end connected to the anode terminal of the second diode 38 and the other end of the smoothing circuit 34. The input side coil 22 and the output side coil 30 are combined to form a transformer of the DCDC converter circuit 10.

  The rectifier circuit 32 is a circuit including a first diode 36 and a second diode 38. The rectifier circuit 32 is a circuit that rectifies the power supplied from the input side circuit 14.

  The first diode 36 is a rectifying element whose anode terminal is connected to one end of the output side coil 30 and whose cathode terminal is connected to one end of the smoothing circuit 34 and the cathode terminal of the second diode 38.

  The second diode 38 has a cathode terminal connected to the cathode terminal of the first diode 36 and one end of the smoothing circuit 34, and an anode terminal connected to the other end of the output side coil 30 and the other end of the smoothing circuit 34. It is.

  The smoothing circuit 34 is a circuit that includes a smoothing coil 40 and a smoothing capacitor 42. The smoothing circuit 34 is a circuit that smoothes the power rectified by the rectifying circuit 32 and supplies the smoothed power to the load 8.

  The smoothing coil 40 is a reactor having one end connected to the cathode terminal of the first diode 36 and the cathode terminal of the second diode 38 and the other end connected to one end of the smoothing capacitor 42 and one end of the load 8.

  The smoothing capacitor 42 is a reactor having one end connected to the other end of the smoothing coil 40 and one end of the load 8, and the other end connected to the anode terminal of the second diode 38 and the other end of the load 8.

Based on the output current or output voltage of the input side circuit 14 and the output side circuit 16, the control circuit 18 keeps the output voltage V _O output from the output side circuit 16 constant. On / off control of the switch element 26 is performed.

The control circuit 18 turns on the first switch element 24 in the _ON period T _ON determined by the time ratio D in the predetermined switching period T, and first in the OFF period T _OFF (= T−T _ON ) determined by the time ratio D. The switch element 24 is turned off. The control circuit 18 turns off the second switch element 26 in the on period T _ON and turns on the second switch element 26 in the off period T _OFF .

Next, the resonance frequency f _IN of the input side circuit 14 will be described. Assuming that the value of the input side coil 22 is L _I and the value of the input side capacitor 28 is C _I , f _IN = 1 / (2π × √ ((L _I × C _I ) / (1-D) ² )) The relational expression is established.

The resonance frequency f _OUT of the output side circuit 16 will be described. When the value of the smoothing coil 40 is L _O and the value of the smoothing capacitor 42 is C _O , the relational expression f _OUT = 1 / (2π × √ (L _O × C _O )) is established.

The value L _I of the input side coil 22, the value C _I of the input side capacitor 28, the value L _O and the value C _O smoothing capacitor 42 of the smoothing coil 40, so as to satisfy a relational expression _{f IN ≧ (f OUT + f} th) Respectively. Note that f _IN preferably satisfies the relational expression when f _th = 0.75 × f _OUT , and more preferably satisfies the relational expression when f _th = f _OUT .

Next, the operation of the DCDC converter circuit 10 will be described. First, in order to make the operational effects of the DCDC converter circuit 10 easier to understand, a conventional DCDC converter circuit will be described as a comparative example. FIG. 2 is a circuit characteristic diagram in which the horizontal axis is the duty ratio and the vertical axis is the resonance frequency of the input side circuit. FIG. 3 is a circuit characteristic diagram in which the horizontal axis represents frequency and the vertical axis represents output circuit gain. FIG. 4 is a circuit characteristic diagram in which the horizontal axis represents time, and the vertical axis represents output voltage V _O , duty ratio D, and load Δ variation ΔI _L.

First, when the value of the input side capacitor 28 is set to C _I = 0.5 μF so that f _IN <(f _OUT + f _th ), the resonance frequency f _OUT of the output side circuit 16 is as shown in FIG. However, the resonance frequency f _IN of the input side circuit 14 varies according to the value of the time ratio D. When D ₀ = 0.18, f _IN0 = about 28 kHz, but when D ₁ = 0.42, f _IN1 = about 21 kHz and approaches the frequency of f _OUT .

As shown in FIG. 3, when f _IN0 = about 28 kHz, the gain is about −4 dB. When f _IN1 = about 21 kHz, the gain is about 16 dB and is amplified by the output side circuit 16. You can see that Specifically, as shown in FIG. 4, vibration is superimposed on the output voltage V _O when the load 8 increases between 0.5 ms and 1.0 ms and the duty ratio D increases. I understand.

Next, a case where the value of the input side capacitor 28 is set to C _I = 0.1 μF so as to satisfy the relational expression of f _IN ≧ (f _OUT + f _th ) in the DCDC converter circuit 10 will be described. FIG. 5 is a circuit characteristic diagram in which the horizontal axis is the duty ratio and the vertical axis is the resonance frequency of the input side circuit. FIG. 6 is a circuit characteristic diagram in which the horizontal axis represents frequency and the vertical axis represents output circuit gain. FIG. 7 is a circuit characteristic diagram in which the horizontal axis represents time, and the vertical axis represents output voltage V _O , duty ratio D, and load Δ variation ΔI _L.

When the value of the input side capacitor 28 is set to C _I = 0.1 μF, as shown in FIG. 5, when D ₀ = 0.18, f _IN0 = about 60 kHz, but D ₁ = 0. In the case of 42, f _IN1 = about 42 kHz, which is a frequency nearly twice as high as f _OUT .

As shown in FIG. 6, when f _IN0 = about 60 kHz, the gain is about −20 dB, but when f _IN1 = about 42 kHz, it is about −12 dB and is not amplified by the output side circuit 16. Specifically, as shown in FIG. 7, even when the load 8 increases between 0.5 ms and 1.0 ms and the duty ratio D increases, vibration is superimposed on the output voltage V _O. do not do.

Thus, in the DCDC converter circuit 10, so as to satisfy a relational expression _{f IN ≧ (f OUT + f} th), the value L _I of the input side coil 22, the value C _I of the input side capacitor 28, the value of the smoothing coil 40 L _O and the value C _O of the smoothing capacitor 42 are set. Thereby, even when the load 8 connected to the output side circuit 16 fluctuates, a sufficient difference between the resonance frequency f _IN0 of the input side circuit 14 and the resonance frequency f _OUT of the output side circuit can be secured. Therefore, the vibration of the output side circuit can be suppressed when responding by changing the duty ratio in accordance with the change of the load.

  8 load, 10 DCDC converter circuit, 14 input side circuit, 16 output side circuit, 18 control circuit, 20 power supply, 22 input side coil, 24 first switch element, 25 clamp circuit, 26 second switch element, 28 input side capacitor , 30 output side coil, 32 rectifier circuit, 34 smoothing circuit, 36, 38 diode, 40 smoothing coil, 42 smoothing capacitor.

Claims (3)

A DCDC converter circuit comprising: an input side circuit having a power supply; and an output side circuit that receives supply of energy from the input side circuit by magnetic coupling and supplies the energy to a load.
The input side circuit supplies the energy to the output side circuit based on a time ratio D that is changed according to a change in the load,
The circuit constant of at least one of the input side circuit and the output side circuit is set such that the input side resonance frequency of the input side circuit is equal to or higher than a predetermined frequency exceeding the output side resonance frequency of the output side circuit. DCDC converter circuit characterized by the above. The DCDC converter circuit according to claim 1,
The input side circuit is:
Power supply,
An input side coil provided in parallel with the power source;
A first switching element that is provided in series with the input side coil, and is turned on in an on period determined by the time ratio D in one cycle and turned off in an off period determined by the time ratio D;
An input side capacitor provided in parallel with the input side coil;
A second switch element that is provided in series with the input-side capacitor and is turned off while the first switch element is on, and turned on while the first switch element is off;
Have
The output side circuit is:
An output side coil magnetically coupled to the input side coil;
A smoothing capacitor connected in series to the output side coil;
A smoothing coil connected in series to the output side coil and the smoothing capacitor;
Have
The input side resonance frequency is determined based on the value L _I of the input side coil, the value C _I of the input side capacitor, and the duty ratio D,
The output-side resonance frequency is determined based on a value L _{O of the} smoothing coil and a value C _{O of the} smoothing capacitor. The DCDC converter circuit according to claim 1 or 2,
The DCDC converter circuit, wherein the predetermined frequency is twice the output-side resonance frequency.

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