JP5238447B2 - DC-DC converter - Google Patents

Description

  The present invention relates to a DC-DC converter that boosts or steps down a DC voltage from a DC power supply.

A DC-DC converter that keeps an output voltage constant even when an input voltage from a power source such as a battery fluctuates is known (see, for example, Patent Document 1).
JP 2007-295663 A

  Conventionally, when the input voltage of the DC-DC converter falls outside the rated range, the voltage for driving the control circuit that controls the voltage conversion circuit cannot be maintained, and the control circuit is stopped to stop the output of the DC-DC converter. It was. However, there is a case where it is desired to continue the operation as much as possible even if the voltage drops depending on the load or the device on the power supply side. For example, in the case of medical equipment, communication infrastructure equipment, etc., there are devices that should be able to move as much as possible even when the input voltage drops (devices that stop in a safe state, security devices, emergency communication devices, etc.), and the battery voltage drops However, if the DC-DC converter is stopped, the above-mentioned device is also stopped or the function is remarkably deteriorated.

  In order to avoid such a state, the rated range of the input voltage of the DC-DC converter can be widened, but the cost increases due to a decrease in efficiency in the steady state and the need to increase the breakdown voltage of the semiconductor element. There was a problem of upsizing.

  Therefore, in order to solve the above problems, the present invention can output direct-current power to a load or a power supply side device even if the input voltage is outside the rated range, and has high efficiency, low cost, and small DC-DC. An object is to provide a converter.

  In order to achieve the above object, the DC-DC converter according to the present invention outputs a voltage different from the rated value when the input voltage is out of the rated range, and continues to operate so as not to exceed the capability of the voltage conversion circuit. It was decided.

  Specifically, the DC-DC converter according to the present invention includes a voltage conversion circuit that converts a DC input voltage on the input side into an output voltage and outputs the output voltage, and the output voltage within the rated range. And the voltage conversion circuit is controlled so that the output voltage becomes a predetermined value different from the rated value of the output voltage when the input voltage is out of the rated range. A control circuit.

  The DC-DC converter according to the present invention has a voltage within the capability range of the voltage conversion circuit, a load, and a device on the power supply side even when the input voltage drops momentarily (instantaneous drop) or drops for a long time. It is possible to output an output voltage that does not affect the output. For this reason, the DC-DC converter according to the present invention can be connected to a medical device, a communication infrastructure device, or the like which is a system that is related to human life and places the highest importance on safety and cannot stop power supply. In addition, since the rated range of the input voltage can be reduced, the efficiency of the apparatus is increased, and the cost can be reduced by selecting an optimum element that does not overspecify the semiconductor element.

  Therefore, the DC-DC converter according to the present invention can output direct-current power to a load or a device on the power supply side even if the input voltage is outside the rated range, and can be highly efficient and can be reduced in size at low cost.

  The control circuit of the DC-DC converter according to the present invention includes an arithmetic unit that generates a control signal for controlling the voltage conversion circuit, the input voltage on the input side of the voltage conversion circuit, and the output of the voltage conversion circuit It is preferable to have a switch that selects any one of the output voltages on the side as control power to be supplied to the arithmetic unit.

  The DC-DC converter according to the present invention can secure the control power for the control circuit even when the input voltage drops momentarily or drops for a long time, and the power conversion circuit can be controlled by the monitor and the calculation unit. Therefore, the DC-DC converter according to the present invention can safely stop the system or continuously supply power at a predetermined voltage when the input voltage drops momentarily or drops for a long time. Can do.

  The switch of the control circuit can select the input voltage when the input voltage is within a rated range, and can select the output voltage when the input voltage is outside the rated range. Even when the input voltage decreases, by switching the switch, the power of the output voltage boosted by the voltage conversion circuit can be supplied to the control circuit, and the control of the voltage conversion circuit can be continued.

The switch of the control circuit can select one of the input voltage and the output voltage that is closer to the rated voltage of the control power supplied to the control circuit . It is possible to select an appropriate control power to be supplied to the control circuit by comparing the input voltage and the output voltage.

  The present invention can provide direct current power to a load or a device on the power supply side even when the input voltage is outside the rated range, and can provide a small-sized DC-DC converter with high efficiency and low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
In FIG. 1, the schematic block diagram of the DC-DC converter 301 of this embodiment is shown. The DC-DC converter 301 converts a DC input voltage Vin on the input side into an output voltage Vout and outputs it to the output side, and the output voltage Vout becomes a rated value when the input voltage Vin is within a rated range. A control circuit 14 for controlling the voltage conversion circuit 12 so that the output voltage Vout becomes a predetermined value different from the rated value of the output voltage when the input voltage Vin is outside the rated range. Prepare.

  The DC power supply 11 is connected to the input side of the DC-DC converter 301, and DC power whose voltage is the input voltage Vin is supplied. The DC power supply 11 is a battery or a solar cell, for example. In the present embodiment, the DC power supply 11 is a battery. On the other hand, the power supplied device 13 is connected to the output side of the DC-DC converter 301, and the power of the output voltage Vout is supplied from the DC-DC converter 301. The power supplied device 13 is, for example, a motor control device, a security device, or an emergency communication device.

  The voltage conversion circuit 12 converts the input voltage Vin to the output voltage Vout and outputs it. The voltage conversion circuit 12 is a step-up circuit, a step-down circuit or a step-up / step-down circuit. The booster circuit is a circuit that performs voltage conversion so that the output voltage Vout is higher than the input voltage Vin. The step-down circuit is a circuit that performs voltage conversion so that the output voltage Vout is lower than the input voltage Vin. The step-up / step-down circuit is a circuit that converts the voltage so that the output voltage Vout is higher than the input voltage Vin and converts the voltage so that the output voltage Vout is lower than the input voltage Vin. .

  In the present embodiment, the voltage conversion circuit 12 is a booster circuit. The voltage conversion circuit 12 uses, for example, a semiconductor switch that turns on and off at high speed. The control circuit 14 controls the on / off time ratio of the semiconductor switch with the control signal S to adjust the output voltage Vout. The voltage conversion circuit 12 may have a configuration in which, for example, the input direct current is converted into alternating current, boosted using a transformer, and converted into direct current again. Even when a transformer is used, the output voltage can be controlled by the control signal S as described above.

  The control circuit 14 measures the input voltage Vin and the output voltage Vout. When the input voltage Vin is within the rated range, the control circuit 14 controls the voltage conversion circuit 12 so that the output voltage Vout becomes the rated value, and the input voltage Vin decreases. When the voltage is out of the rated range, the voltage conversion circuit 12 is controlled so that the output voltage Vout becomes a guaranteed voltage value lower than the rated value of the output voltage. The control circuit 14 controls the output voltage Vout of the voltage conversion circuit 12 with the control signal S. The guaranteed voltage value is a voltage at which the power-supplied device 13 can operate, and is a voltage that can drive the calculation unit 42 described later.

The operation of the DC-DC converter 301 will be described with reference to FIG. For example, the rated range of the input voltage Vin is 10V to 14V, and the rated value of the output voltage Vout is 24V. When the input voltage Vin is in the rated range (time t _{10 to} t ₁₁ ), the DC-DC converter 301 supplies the output voltage Vout stabilized at 24 V to the power supplied device 13. On the other hand, when the input voltage Vin becomes 10 V or less (time t _{11 to} t ₁₂ ), the DC-DC converter 301 can supply power and the power supplied device 13 can operate. The output voltage Vout is lowered to a certain voltage (for example, 12 V or 10 V), and the power supply to the power supplied device 13 is continued.

When the input voltage Vin returns to within the rated range (time t _{12 to} t ₁₃ ), the DC-DC converter 301 supplies the output voltage Vout stabilized at 24 V to the power supplied device 13 again.

  Next, an internal circuit of the control circuit 14 will be described. The control circuit 14 includes a calculation unit 42 that generates a control signal S for controlling the voltage conversion circuit 12, an input voltage Vin on the input side of the voltage conversion circuit 12, and an output voltage Vout on the output side of the voltage conversion circuit 12. And a switch 43 that selects one of them as control power to be supplied to the calculation unit 42.

The computing unit 42 may be constituted by a microcomputer, for example. The calculation unit 42 measures the input voltage Vin and the output voltage Vout, determines which one is selected as the control power, and outputs a switching signal to the switch 43. For example, the calculation unit 42 outputs a switching signal to the switch 43 so that the input voltage Vin is selected when the input voltage Vin is within the rated range, and the output voltage Vout is selected when the input voltage Vin is outside the rated range. Also good. In addition, the calculation unit 42 may output a switching signal to the switch 43 so as to select one of the input voltage Vin and the output voltage Vout that is closer to the rated voltage of the control power supplied to the calculation unit 42.

  The power selected by the switch 43 is input to the power supply circuit 41, adjusted to control power for driving the calculation unit 42, and supplied to the calculation unit 42. The power supply circuit 41 has, for example, a function of removing high frequency components and a function of adjusting so as to have a constant voltage.

For example, the operation of the control circuit 14 of the DC-DC converter 301 in which the rated range of the input voltage Vin is 10V to 14V and the rated value of the output voltage Vout is 24V will be described. When the input voltage Vin is within the rated range (time t _{10 to} t ₁₁ ), the arithmetic unit 42 outputs a switching signal so as to select the input voltage Vin, and the switch 43 selects the input signal Vin and supplies it to the power supply circuit 41. To do. On the other hand, the input voltage Vin is 10V or less (e.g., 7V) when it is (time _t 11 _{~t 12),} computing unit 42 outputs a switching signal to select the output voltage Vout, the switch 43 output signal Vout Is selected and supplied to the power supply circuit 41. At the same time, the calculation unit 42 outputs a control signal S that lowers the output voltage Vout (for example, lowers to 10 V) to the voltage conversion circuit 12. Even if the input voltage Vin falls below the rated range, since the output voltage Vout boosted by the voltage conversion circuit 12 is selected, the calculation unit 42 can continue the calculation, and the control circuit 14 controls the voltage conversion circuit 12. Can continue.

When the input voltage Vin returns to within the rated range (time t _{12 to} t ₁₃ ), the calculation unit 42 outputs a switching signal so as to select the input voltage Vin, and the switch 43 selects the input signal Vin to select the power supply circuit. 41 is supplied. At the same time, the calculation unit 42 outputs a control signal S for returning the output voltage Vout to 24V to the voltage conversion circuit 12.

The DC-DC converter 301 may operate as shown in FIG. Assume that the voltage (input voltage Vin) of the DC power supply 11 gradually decreases as shown in FIG. When the input voltage Vin is in the rated range (time t _{20 to} t ₂₁ ), the DC-DC converter 301 supplies the output voltage Vout stabilized at 24 V to the power supplied device 13. Further, the calculation unit 42 outputs a switching signal so as to select the input voltage Vin, and the switch 43 selects the input signal Vin and supplies it to the power supply circuit 41.

When the input voltage Vin becomes lower than the rated range (time t _{21 to} t ₂₂ ), the DC-DC converter 301 supplies the output voltage Vout that is decreased in conjunction with the decrease of the input voltage Vin to the power supplied device 13. To do. Further, the arithmetic unit 42 outputs a switching signal so as to select the output voltage Vout, and the switch 43 selects the output signal Vout and supplies it to the power supply circuit 41.

(Embodiment 2)
This embodiment will be described with reference to FIG. Reference numerals not described below are the same as those in the first embodiment. In the present embodiment, the DC power supply 11 is a solar battery. The voltage conversion circuit 12 is a step-up / down circuit. The power supply circuit 41, the calculation unit 42, and the switch 43 operate as described in the first embodiment.

In the case of a solar cell, the input voltage Vin varies greatly depending on the weather and time. However, it is desirable that the power supplied device 13 is supplied with power at a constant voltage. FIG. 4 is a diagram for explaining the operation of the DC-DC converter 301 of the present embodiment. Time _t 30 _{~t 31} is before sunrise time _t 31 _{~t 32} time until the generated voltage of the solar cell reaches 10V, the time _t 32 _{~t 35} time generated voltage is above 10V solar cells, the time t ₃₅ ~t ₃₆ time until sunset will be less than the power generation voltage is 10V of solar cells, the time _{t 36} after a time after sunset. Energy can be effectively used by controlling in this way.

Since the input voltage Vin is 6 V or less of the stop voltage after the time t _{30 to} t ₃₁ and the time t ₃₆ , the DC-DC converter 301 stops the power supply to the power supplied device 13. Moreover, the calculating part 42 outputs the control signal S which stops voltage conversion to the voltage conversion circuit 12, and stops itself.

At times t _{31 to} t ₃₂ and times t _{35 to} t ₃₆ , the generated voltage of the solar cell is below the rated range of the input voltage Vin of the DC-DC converter 301, so that the DC-DC converter 301 drops from the rated value. The output voltage Vout (10 V) is supplied to the power supplied device 13. Further, the arithmetic unit 42 outputs a switching signal so as to select the output voltage Vout, and the switch 43 selects the output signal Vout and supplies it to the power supply circuit 41.

At times t _{32 to} t ₃₅ , since the power generation voltage of the solar cell is larger than the lower limit of the rated range of the input voltage Vin of the DC-DC converter 301, the DC-DC converter 301 is supplied with a stable output voltage Vout at 24 V. Supply to the device 13. Further, the calculation unit 42 outputs a switching signal so as to select the input voltage Vin, and the switch 43 selects the input signal Vin and supplies it to the power supply circuit 41. Incidentally, during the time _t 33 _{~t 34,} since the power generation voltage of the solar cell is greater than the upper limit of the rated range of the input voltage Vin of the DC-DC converter 301, the voltage conversion circuit 12 operates as a step-down circuit. That is, since the input voltage Vin is higher than the output voltage Vout, the control circuit 14 outputs the control signal S so that the output voltage Vout becomes 24V which is the rated value.

  The DC-DC converter according to the present invention can be applied to medical equipment, communication infrastructure equipment, and the like.

1 is a schematic configuration diagram of a DC-DC converter according to the present invention. It is a figure explaining the relationship between the input voltage of the DC-DC converter which concerns on this invention, an output voltage, and the voltage of a control power supply. (A) is the input voltage Vin, (b) is the output voltage Vout, (c) is the voltage of the control power supply. It is a figure explaining the relationship between the input voltage of the DC-DC converter which concerns on this invention, an output voltage, and the voltage of a control power supply. (A) is the input voltage Vin, (b) is the output voltage Vout, (c) is the voltage of the control power supply. It is a figure explaining the relationship between the input voltage of the DC-DC converter which concerns on this invention, an output voltage, and the voltage of a control power supply. (A) is the input voltage Vin, (b) is the output voltage Vout, (c) is the voltage of the control power supply.

Explanation of symbols

11: DC power supply 12: Voltage conversion circuit 13: Power supplied device 14: Control circuit 41: Power supply circuit 42: Calculation unit 43: Switch 301: DC-DC converter

Claims (1)

A voltage conversion circuit that converts a DC input voltage on the input side to an output voltage and outputs the output voltage to the output side to which the power-supplied device is connected ;
The voltage conversion circuit is controlled so that the output voltage becomes a rated value when the input voltage is within the rated range, and the output voltage is equal to the output voltage when the input voltage is outside the rated range where the input voltage is reduced from the voltage within the rated range. A control circuit for controlling the voltage conversion circuit so as to have a predetermined value different from the rated value;
Equipped with a,
The control circuit includes:
Measure the input voltage on the input side of the voltage conversion circuit and the output voltage on the output side of the voltage conversion circuit, determine which one to select as control power, and control signals for controlling the voltage conversion circuit A computing unit to generate,
A switch that selects any one of the input voltage and the output voltage as the control power to be supplied to the arithmetic unit;
A power supply circuit that adjusts one of the input voltage and the output voltage selected by the switch to the control power that drives the arithmetic unit and supplies the control power to the arithmetic unit;
Have
The arithmetic unit outputs a switching signal to the switch so as to select the input voltage when the input voltage is within a rated range, and supplies the input voltage to the power supply circuit as the control power. The voltage conversion circuit is controlled so that the output voltage becomes a rated value, and when the input voltage is lower than a voltage within a rated range, the input voltage stops the power supply to the power supplied device. When the output voltage is higher than the rated value, the voltage conversion circuit is controlled so that the output device is a voltage at which the power-supplied device can operate and the operation unit can be controlled. , and outputs a switching signal to the switch to select the output voltage, DC-DC converter, characterized by supplying to the power supply circuit the output voltage as the control power .

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