JP2009118589A - Dc voltage booster circuit and guiding light device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC voltage booster circuit which highly efficiently realizes boost-up at a high boosting ratio from low battery voltage. <P>SOLUTION: A series circuit of a boosting coil 1 and FET (field effect transistor) 2 is connected to a battery 51, and current flowing in the boosting coil 1 is disconnected by FET2. Thus, a smoothing capacitor 4 is charged to voltage higher than that of the battery 51. Power is supplied to a control circuit 6 from the smoothing capacitor 4 charged by boosted voltage and the circuit applies a sufficiently high voltage signal Sg operating FET 2 with low on-resistance to a gate. Since on-resistance can be made small by applying sufficiently high voltage to the gate of FET2, circuit loss can be reduced and low battery voltage can highly efficiently be boosted with the high boosting ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC booster circuit and a guide lamp device.

  For example, in the case of an emergency such as a power outage, in a guide lamp device that lights a plurality of LEDs (Light Emitting Diodes) from a battery using a DC booster circuit, the LEDs are connected in series and driven at a constant current for the purpose of suppressing uneven brightness of the LEDs. It is common to turn on the light (see, for example, Patent Document 1). In addition, when connecting a plurality of LEDs in parallel, a constant current circuit is inserted in series with the LEDs in order to suppress uneven brightness of individual LEDs, but a constant current circuit proportional to the number of LEDs in parallel is required. Since the circuit scale increases and the circuit loss increases, the LEDs are generally connected in series as described above.

JP 2002-246190 A (paragraph number 0029 and FIG. 1)

  The conventional DC booster circuit is configured as described above, and in order to turn on the induction lamp in the event of an emergency when the AC power supply fails, a low battery voltage and a high voltage capable of lighting a plurality of LEDs connected in series Must be boosted. For example, when six LEDs connected in series (forward voltage Vf = about 4V) are lit by two batteries (end-of-discharge voltage of about 2.0V), the DC booster circuit that drives the LED has an input voltage of 2V. It is necessary to increase the voltage by about 13 times to about 26 V (4 V × 6 pieces + about 2 V voltage drop of the constant current circuit).

  However, when control is performed using a low battery voltage as the power source of the DC booster circuit, the booster switching element of the DC booster circuit, for example, an FET (field effect transistor) cannot be driven in a sufficiently low on-resistance state. There was a problem of increasing the loss. Further, in order to avoid an increase in circuit loss, the capacity for lighting the LED for a predetermined time (for example, 20 minutes) is sufficient with two batteries, but it is necessary to connect three or more batteries in series. This leads to an increase in the size and price of the device.

  The present invention has been made to solve the above-described problems, and can provide a DC boost circuit capable of boosting from a low battery voltage with high efficiency and a high boost ratio, and a small and inexpensive guide lamp device. The purpose is to obtain.

  The DC booster circuit according to the present invention includes a switching circuit, an energy storage circuit, and a control circuit. The switching circuit is connected to a battery, and has an inductance element having an inductance and an open / close signal. A switching element having a control terminal to be input is connected in series, and the energy storage circuit is a unidirectional conducting element and a capacitor connected in series, and is connected in parallel to the switching element. In addition, a load is connected to the capacitor, and the control circuit receives power from the capacitor and applies an opening / closing signal of a predetermined voltage to the control terminal of the switching element to control the opening and closing of the switching element. By switching the flowing battery current, the capacitor is connected to the battery voltage. It is also intended to charge the high voltage.

  The guide lamp device according to the present invention includes a DC booster circuit as described above, a battery to which the DC booster circuit is connected, and an LED connected in series, and is connected to the DC booster circuit as a load. It has an LED lamp.

  A DC booster circuit according to the present invention includes a switching circuit, an energy storage circuit, and a control circuit, and the switching circuit is connected to a battery, and an inductance element having an inductance and a switching signal are input. A switching element having a control terminal to be connected is connected in series, and the energy storage circuit is formed by connecting a one-way conducting element and a capacitor in series and connected in parallel to the switching element. In addition, a load is connected to the capacitor, and the control circuit receives power from the capacitor and gives a switching signal of a predetermined voltage to the control terminal of the switching element to control the switching element to flow to the inductance element. Capacitor higher than battery voltage by interrupting battery current Since it is intended to charge the pressure, can reduce the circuit loss by reducing the on-resistance of the switching element, it is possible to realize a DC boost circuit for a and a lower voltage with high efficiency can be boosted by the high step-up ratio.

  The guide lamp device according to the present invention includes a DC booster circuit as described above, a battery to which the DC booster circuit is connected, and an LED connected in series, and is connected to the DC booster circuit as a load. Since it has an LED lamp, power loss is small, and it can be made small and inexpensive.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a configuration of a guide lamp device including a DC booster circuit according to Embodiment 1 for carrying out the present invention. In FIG. 1, a DC booster circuit 100 has input terminals P1 and N1 and output terminals P2 and N2, and the input terminals P1 and N1 function as a switching circuit between a booster coil 1 as an inductance element and an FET2 as a switching element. A series circuit is connected. In this embodiment, the FET 2 uses a MOS FET (Metal Oxide Field Effect Effect Transistor), the drain is connected to the step-up coil 1, the source is connected to the input terminal N1, and the gate serving as the control terminal is described later. It is connected to the circuit 6.

  The smoothing capacitor 4 as a capacitor has one terminal Cp connected to the FET 2 side of the booster coil 1 via a rectifier diode 3 as a one-way conducting element, and the other terminal Cn connected to the input terminal N1. . A series circuit of the rectifier diode 3 and the smoothing capacitor 4 is the energy storage circuit in the present invention.

  One terminal Cp of the smoothing capacitor 4 is connected to the output terminal P2, and the other terminal Cn is connected to the output terminal N2 via the constant current control resistor 5. Electric power for the operation is supplied to the control circuit 6 from one terminal Cp and the output terminal N2 of the smoothing capacitor 4 via the regulator circuit 7. An open / close control signal Sg for performing pulse width modulation control is applied from the terminal PWM of the control circuit 6 to the gate of the FET 2. A battery 51 in which two batteries are connected in series is connected to the input terminals P1, N1, and an LED lamp 52 composed of six LEDs connected in series is connected to the output terminals P2, N2. A guide light device is configured.

  In the DC booster circuit 100 as described above, a voltage obtained by subtracting the voltage drops of the booster coil 1, the rectifier diode 3, and the regulator circuit 7 from the terminal voltage of the battery 51 is supplied to the terminal Vcc of the control circuit 6. Thus, if the voltage is equal to or higher than the minimum gate voltage of the FET 2, it can be started without any problem. When the voltage of the battery 51 is sufficiently higher than the minimum gate voltage of the FET 2, for example, when the minimum gate voltage of the switching element is 1.8 V and the voltage of the battery 51 is secured to 3.0 V or more, there is no problem. Can be activated.

  After the DC booster circuit 100 is started, the voltage between the output terminals P2 and N2, that is, the output voltage of the DC booster circuit 100 is supplied to the terminal Vcc and the terminal F / B of the control circuit 6 via the regulator circuit 7 and output. An opening / closing control signal Sg is output from the terminal PMW so that the voltage becomes a predetermined value. If the output voltage of the DC booster circuit 100 exceeds the withstand voltage limit value of the gate of the control circuit 6 or the FET 2, the control circuit 6 or the FET 2 may be destroyed. Therefore, the regulator circuit 7 is interposed between the smoothing capacitor 4 and the control circuit 6. Is inserted to prevent a voltage higher than a predetermined voltage from being supplied to the control circuit 6 to protect against overvoltage.

  Further, optimizing the gate application voltage of the FET 2 reduces the resistance loss due to the on-resistance of the FET 2. For example, when the FET having a minimum gate voltage of 1.8V is used, the range of the adjustment voltage in the regulator circuit 7 is preferably about 5 to 10V, which is 3 to 5 times the minimum gate voltage. Here, the applied voltage applied to the booster coil 1 is a value obtained by subtracting the voltage drop due to the ON resistance of the FET 2 from the voltage of the battery 51, but a voltage sufficiently higher than the minimum gate voltage of the FET 2 is supplied to the gate. As a result, the on-resistance of the FET 2 can be reduced, and the voltage applied to the booster coil 1 can be secured even when the battery voltage is lower.

As described above, according to this embodiment, it is possible to reduce a circuit loss by reducing the on-resistance of the switching element, and it is possible to realize a DC boost circuit capable of boosting a low voltage with a high boost ratio with high efficiency. Moreover, if this DC booster circuit is used in a guide lamp device for lighting an LED lamp, a small and inexpensive guide lamp device with low power loss can be obtained.
In this embodiment, the voltage between the output terminals P2 and N2 is supplied to the control circuit 6, but the charging voltage of the smoothing capacitor 4 is directly supplied without passing through the constant current control resistor 5. You may do it.

Embodiment 2. FIG.
FIG. 2 is a configuration diagram illustrating a configuration of a guide lamp device including the DC booster circuit according to the second embodiment. In the DC booster circuit 200, two cathodes of an input backflow prevention diode 18 and an output backflow prevention diode 19 via the regulator circuit 7 are connected in common and connected to the power supply terminal Vcc of the control circuit 6, and the voltage of the battery 51 is boosted. The control circuit 6 can be directly supplied without passing through the coil 1 and the rectifier diode 3, and the voltage of the smoothing capacitor 4 is also supplied. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted.

  In this embodiment, when the DC booster circuit 200 is activated, the voltage of the battery 51 is directly supplied to the control circuit 6 via the input backflow prevention diode 18 without passing through the booster coil 1 and the rectifier diode 3. Thus, unlike the first embodiment, since it is not affected by the voltage drop in the booster coil 1 and the rectifier diode 3 at the time of startup, the voltage of the battery 51 decreases and the startup circuit 100 of the first embodiment cannot be started. Even if it is bootable. After startup, the boosted voltage is supplied from the smoothing capacitor 4, and the voltage applied to the gate is controlled to an optimum value so that the on-resistance of the FET 2 becomes sufficiently low.

  Thereby, it is possible to obtain a DC boosting circuit capable of boosting at a high boosting ratio from a low voltage with a low loss. Further, by connecting the input backflow prevention diode 18 and the cathode of the output backflow prevention diode 19 together, the smoothing capacitor 4 in which the power supply for supplying power to the control circuit 6 is boosted from the direct supply from the battery 51 after startup. Automatically switch to supply from. Of course, by providing the regulator circuit 7 between the smoothing capacitor 4 and the output backflow prevention diode 19, even when the output voltage of the DC booster circuit is high, the voltage supplied to the control circuit 6 is the withstand voltage of the control circuit 6. It is adjusted so that it does not exceed, and overvoltage is prevented.

  In the above embodiment, the FET is shown as the switching element. However, the present invention is not limited to this, and the same effect can be obtained even with other voltage-driven switching elements. Further, the load is not limited to the LED lamp but may be other loads.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of the guide lamp apparatus provided with the direct current | flow voltage | pressure booster circuit which is Embodiment 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of the guide lamp apparatus provided with the direct current | flow voltage | pressure booster circuit which is Embodiment 1 of this invention.

Explanation of symbols

1 step-up coil, 2 FET, 3 rectifier diode, 4 smoothing capacitor,
6 control circuit, 7 regulator circuit, 18 input backflow prevention diode,
19 Output backflow prevention diode, 51 battery, 52 LED lamp.

Claims (5)

A switching circuit, an energy storage circuit, and a control circuit,
The switching circuit is connected to a battery, and an inductance element having an inductance and a switching element having a control terminal to which an open / close signal is input are connected in series,
In the energy storage circuit, a one-way conduction element and a capacitor are connected in series, and connected in parallel to the switching element, and a load is connected to the capacitor.
The control circuit receives power from the capacitor and applies an open / close signal of a predetermined voltage to the control terminal of the switching element, thereby controlling the switching element to open / close, and intermittently current of the battery flowing through the inductance element. By charging the capacitor to a voltage higher than the voltage of the battery,
DC booster circuit. 2. The DC booster circuit according to claim 1, wherein the control circuit receives power from the capacitor via a regulator circuit that adjusts an output voltage within a predetermined range. 3. The DC booster circuit according to claim 2, wherein the control circuit is configured to receive power from the battery without passing through the inductance element and the one-way conduction element. 4. The DC booster circuit according to claim 1, wherein the switching element is a field effect transistor. 5. 5. A DC booster circuit according to claim 1, a battery to which the DC booster circuit is connected, and an LED are connected in series and connected to the DC booster circuit as the load. An LED lamp device having an LED lamp.

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