JP2013013214A - Constant current power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a constant current power supply device that can ensure stability of a constant current output with respect to an input voltage change while satisfying high frequency regulation.SOLUTION: A constant current power supply device 1 includes: a constant current circuit 20 to output a constant current; and a control part 10 to control the constant current circuit 20. The constant current power supply device 1 also includes a power factor improvement circuit 30 disposed closer to an input side of the constant current power supply device 1 than the constant current circuit 20. The power factor improvement circuit 30 is operated on the basis of a gate signal transmitted from the control part 10 to the constant current circuit 20.

Description

  The present invention relates to a constant current power supply device.

  Conventionally, there is a constant current power supply device as a power source that outputs a constant current. This constant current power supply device is used, for example, to light a light emitting diode (see, for example, Patent Documents 1 and 2).

[Configuration of Constant Current Power Supply Device 100]
FIG. 4 is a circuit diagram of a constant current power supply device 100 according to a conventional example. The constant current power supply device 100 outputs constant current to a plurality of light emitting diodes LED1 to LEDn (n is an integer satisfying n ≧ 3) connected in series using AC power input from the AC power supply Vin. The constant current power supply device 100 includes a rectifying unit RF, a capacitor C4, a control unit 10, and a constant current circuit 20.

  The constant current circuit 20 includes a resistor R, a capacitor C3, a diode D3, an inductor L2, and a switch element Q1 composed of an N-channel MOSFET.

  Both ends of the AC power source Vin are connected to the two input terminals of the rectifying unit RF. One electrode of the capacitor C4, the cathode of the diode D3, one electrode of the capacitor C3, and the anode of the light emitting diode LED1 are connected to the first output terminal of the rectifying unit RF. The other electrode of the capacitor C3 and one end of the inductor L2 are connected to the cathode of the light emitting diode LEDn. The other end of the inductor L2 is connected to the anode of the diode D3 and the drain of the switch element Q1.

  A second output terminal of the rectifying unit RF corresponding to the reference potential point of the constant current power supply device 100 is connected to the source of the switch element Q1 through the resistor R, and the control unit 10 is connected. The control unit 10 is also connected to the gate of the switch element Q1 and the second output terminal of the rectifying unit RF. The other electrode of the capacitor C4 is also connected to the second output terminal of the rectifying unit RF.

[Operation of Constant Current Power Supply Device 100]
The constant current power supply device 100 having the above configuration controls the constant current circuit 20 by the control unit 10 to perform constant current control. Specifically, the control unit 10 controls the switch element Q1 according to the drain current of the switch element Q1, thereby controlling the switch element Q1 according to the output current of the constant current power supply device 100, thereby controlling the constant current. To output a constant current.

  For example, assume that the control unit 10 applies an H level gate signal to the gate of the switch element Q1 to turn on the switch element Q1. Then, the AC power input from the AC power source Vin is rectified by the rectifying unit RF, and the DC power based on the second output terminal is output from the first output terminal. The direct current output from the first output terminal of the rectifying unit RF is transmitted through the light emitting diodes LED1 to LEDn, one end to the other end of the inductor L2, the switch element Q1, and the resistor R, and the rectifying unit RF. It flows to the second output terminal. According to this, since a current flows through the light emitting diodes LED1 to LEDn, the light emitting diodes LED1 to LEDn are turned on. Further, when current flows from one end of the inductor L2 to the other end, energy is stored in the inductor L2.

  The current flowing through the switch element Q1 described above, that is, the drain current of the switch element Q1 is converted into a voltage by flowing through the resistor R and input to the control unit 10. Here, when the switch element Q1 is kept in the on state, the current flowing from one end of the inductor L2 to the other end increases as time passes. Further, during the period when the switch element Q1 is in the ON state, the drain current of the switch element Q1 is equal to the current flowing from one end of the inductor L2 to the other end, that is, the output current of the constant current power supply device 100. The voltage converted from the drain current of the switch element Q1 by the resistor R becomes higher as the drain current of the switch element Q1 increases. As described above, during the period in which the switch element Q1 is in the on state, the above-described voltage input to the control unit 10 increases as time elapses.

  The control unit 10 monitors the above-described voltage input to the control unit 10, that is, the voltage converted from the drain current of the switch element Q1 by the resistor R, and the peak value and average value of this voltage are determined in advance. When the threshold voltage is raised, an L level gate signal is applied to the gate of the switch element Q1. According to this, the switch element Q1 is turned off.

  When the switch element Q1 is turned off, current flows in order from one end of the inductor L2 to the other end, the diode D3, and the light emitting diodes LED1 to LEDn by the energy stored in the inductor L2 during the period when the switch element Q1 is on. The light emitting diodes LED1 to LEDn are turned on. The energy stored in the inductor L2 during the period when the switching element Q1 is in the on state decreases as the current flows in the order described above, and the current flowing in the order described above decreases as the energy stored in the inductor L2 decreases. To do. For this reason, when the switching element Q1 is turned off, the current flowing from one end of the inductor L2 to the other end decreases as time elapses.

  When the switch element Q1 is turned off, the drain current of the switch element Q1 becomes “0”, and thus the voltage input to the control unit 10 becomes “0”.

  When a predetermined time elapses after the above voltage input to the control unit 10, that is, the voltage converted from the drain current of the switch element Q1 by the resistor R becomes “0”, the control unit 10 An H level gate signal is applied to the gate of the element Q1. According to this, the switch element Q1 is turned on.

  The output current of the constant current power supply device 100, that is, the current flowing through the light emitting diodes LED1 to LEDn is smoothed by the capacitor C3.

  Further, the capacitor C4 is charged by the current output from the first output terminal. For this reason, even if the AC voltage input from the AC power supply Vin varies, the constant current power supply device 100 can output a constant current until there is no energy stored in the capacitor C4. That is, the capacitor C4 ensures the stability of the constant current output of the constant current power supply device 100 with respect to the fluctuation of the input voltage.

FIG. 5 is a timing chart of the constant current power supply device 100 according to the capacitance of the capacitor C4 during steady operation. It is assumed that the constant current power supply device 100 in FIG. 5B has a larger capacity of the capacitor C4 than the constant current power supply device 100 in FIG. V _Vin indicates an AC voltage input from the AC power source Vin, that is, an input voltage, V _C4 indicates a voltage of one electrode of the capacitor C4, and I _Vin indicates an AC current input from the AC power source Vin, that is, Indicates the input current.

FIG. 6 is a timing chart of the constant current power supply device 100 according to the capacitance of the capacitor C4 when the input voltage V _Vin suddenly changes. It is assumed that the constant current power supply device 100 in FIG. 6B has a larger capacity of the capacitor C4 than the constant current power supply device 100 in FIG. Further, it is assumed that the sudden change of the input voltage V _Vin occurs in the period from time t11 to t12 in FIG. 6A and occurs in the period from time t21 to t22 in FIG. 6B.

As shown in FIGS. 5 and 6, as the capacitance of the capacitor C4 increases, the stability of the constant current output of the constant current power supply device 100 with respect to fluctuations in the input voltage V _Vin is improved.

JP 2004-355872 A JP 2010-40878 A

  The capacitance of the capacitor C4 cannot be simply increased due to high frequency regulations. Therefore, it is conceivable to provide a power factor correction circuit on the input side of the constant current power supply device 100 from the constant current circuit 20.

  However, when the power factor correction circuit is provided as described above, the number of components increases, and the constant current power supply device becomes large.

  In view of the above-described problems, an object of the present invention is to reduce the size of a constant current power supply device that can ensure the stability of a constant current output with respect to fluctuations in input voltage while satisfying high frequency regulations.

The present invention proposes the following items in order to solve the above-described problems.
(1) The present invention is a constant current power supply device (for example, equivalent to the constant current power supply device 1 in FIG. 1) for supplying a constant current to a load (for example, equivalent to the light emitting diodes LED1 to LEDn in FIG. 1), A constant current circuit that outputs a constant current (for example, equivalent to the constant current circuit 20 in FIG. 1), and a power factor improvement circuit (for example, in FIG. 1) provided on the input side of the constant current power supply device from the constant current circuit. Power factor improvement circuit 30) and control means for controlling the constant current circuit (for example, equivalent to the control unit 10 of FIG. 1), the power factor improvement circuit from the control means to the constant current A constant current power supply device is proposed which operates based on a control signal transmitted to a circuit.

  According to the present invention, a constant current power supply that supplies a constant current to a load is provided with a constant current circuit that outputs a constant current and a control unit that controls the constant current circuit. A power factor correction circuit was provided on the input side of the device. Then, the power factor correction circuit is operated based on a control signal transmitted from the control means to the constant current circuit.

  For this reason, since the control means is shared by the constant current circuit and the power factor correction circuit, the constant current power supply device can be reduced in size.

  Further, since the power factor can be improved by the power factor improving circuit, the high frequency regulation can be satisfied.

  In addition, the capacitance of the capacitor related to the stability of the constant current output with respect to the fluctuation of the input voltage could not be simply increased due to the high frequency regulation in the constant current power supply device 100 described above, but the constant current power supply of (1) In the apparatus, since the high frequency regulation can be satisfied as described above, the size can be increased. For this reason, the stability of the constant current output with respect to the fluctuation of the input voltage can be ensured.

  The output voltage of the power factor correction circuit is a direct current, and this direct current voltage is input to the constant current circuit. For this reason, the output current ripple of a constant current power supply device can be suppressed.

Since the control means is also used as described above, the power factor correction circuit is controlled at the constant current control timing in the constant current circuit. For this reason, since the power factor correction control in the power factor correction circuit is not performed at the optimal timing for the power factor improvement, the output voltage of the power factor correction circuit is dependent on the input voltage. Become. However, since the constant current circuit is provided behind the power factor correction circuit, the output current of the constant current power supply device is after the constant current control in the constant current circuit is performed. Therefore, the constant current power supply device can output a constant current.
(2) The present invention relates to the constant current power supply device according to (1), wherein the constant current circuit includes a first switch element (for example, corresponding to a drain to be described later) that receives a current flowing through the load. For example, the control means includes: a switch element Q1 in FIG. 1; and a current-voltage conversion means (for example, equivalent to the resistor R in FIG. 1) for converting the current flowing in the first switch element. Transmits a control signal (e.g., corresponding to a gate signal described later) to the first switch element based on the voltage converted by the current-voltage conversion means, and the power factor correction circuit outputs the control signal to the control signal. A constant current power supply device characterized by including a second switch element (for example, equivalent to the switch element Q2 in FIG. 1) that is chopper-controlled based on the above is proposed.

  According to the present invention, in the constant current power supply device of (1), the constant current circuit includes the first switch element in which the current flowing through the load is input to the input terminal, and the current flowing through the first switch element as a voltage. Current-voltage conversion means for conversion. Further, the control means transmits the control signal to the first switch element based on the voltage converted by the current-voltage conversion means. The power factor correction circuit is provided with a second switch element that is chopper-controlled based on the control signal.

  Here, the input voltage of the constant current circuit is a direct current as described above. For this reason, the duty ratio of the control signal transmitted from the control means to the first switch element is substantially constant, and the second switch element operates based on the control signal transmitted to the first switch element. The duty ratio of the second switch element is also substantially constant. Therefore, since the input current of the constant current power supply device is proportional to the input voltage of the constant current power supply device, the power factor of the constant current power supply device can be improved.

  Note that if the second switch element is also used as the first switch element, the constant current power supply device can be further reduced in size. However, when combined, not only the current flowing through the load but also the current flowing through the second switch element flows through the first switch element. For this reason, the voltage converted by the current-voltage conversion means includes other than the voltage converted from the current flowing through the load. According to this, since the control means cannot accurately detect the current flowing through the load, the constant current power supply device cannot perform the constant current control accurately and cannot output the constant current. End up. However, according to the present invention, since the first switch element and the second switch element are provided separately, the control means can accurately detect the current flowing through the load. Therefore, the constant current power supply device can perform constant current control accurately and can output a constant current.

  (3) The present invention relates to the constant current power supply device of (1) or (2), which is charged by the output of the power factor correction circuit and outputs a charged energy to the constant current circuit (for example, FIG. 1). And the power factor correction circuit has a booster circuit (e.g., equivalent to a booster chopper circuit described later).

  According to the present invention, in the constant current power supply device of (1) or (2), the capacitor that is charged by the output of the power factor correction circuit and outputs the charged energy to the constant current circuit is provided. Further, the power factor correction circuit is configured by a booster circuit.

  For this reason, the output voltage of the power factor correction circuit is higher than the input voltage input to the constant current power supply device. Therefore, more energy can be stored in the capacitor than when no power factor correction circuit composed of a booster circuit is provided, and power is supplied from the capacitor to the constant current circuit for a long time. Therefore, the constant current power supply device can output a constant current for a long time.

  ADVANTAGE OF THE INVENTION According to this invention, while satisfy | filling high frequency restrictions, while being able to ensure the stability of the constant current output with respect to the fluctuation | variation of input voltage, a constant current power supply device can be reduced in size. Further, the output current ripple of the constant current power supply device can be suppressed.

It is a circuit diagram of the constant current power supply device concerning one embodiment of the present invention. 4 is a timing chart of the constant current power supply device during steady operation. It is a timing chart of the said constant current power supply device in case an input voltage changes suddenly. It is a circuit diagram of the constant current power supply device which concerns on a prior art example. 4 is a timing chart of the constant current power supply device during steady operation. It is a timing chart of the said constant current power supply device in case an input voltage changes suddenly.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the constituent elements in the following embodiments can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. Accordingly, the description of the following embodiments does not limit the contents of the invention described in the claims.

[Configuration of Constant Current Power Supply Device 1]
FIG. 1 is a circuit diagram of a constant current power supply device 1 according to an embodiment of the present invention. The constant current power supply device 1 differs from the constant current power supply device 100 according to the conventional example shown in FIG. 4 in that it includes a power factor correction circuit 30 and a capacitor C2 instead of the capacitor C4. In the constant current power supply device 1, the same components as those of the constant current power supply device 100 are denoted by the same reference numerals, and the description thereof is omitted.

  The power factor correction circuit 30 is provided on the input side of the constant current power supply device 1 from the constant current circuit 20, more specifically, between the constant current circuit 20 and the AC power supply Vin. The power factor correction circuit 30 includes a capacitor C1, diodes D1 and D2, an inductor L1, and a switch element Q2 formed of an N-channel MOSFET.

  The inductor L1 and the diode D1 are connected in series, and the diode D2 is connected in parallel to the inductor L1 and the diode D1 connected in series. Then, the capacitor C2 and the constant current circuit 20 are connected to the first output terminal of the rectifying unit RF via the inductor L1 and the diode D1 connected in series and the diode D2. Specifically, one end of the inductor L1 and the anode of the diode D2 are connected to the first output terminal of the rectifying unit RF. The other end of the inductor L1 is connected to the anode of the diode D1. The cathode of the diode D1 and the cathode of the diode D2 are connected to one electrode of the capacitor C2, the cathode of the diode D3, one electrode of the capacitor C3, and the anode of the light emitting diode LED1.

  One electrode of the capacitor C1 is also connected to the first output terminal of the rectifying unit RF. A second output terminal of the rectifying unit RF is connected to the other electrode of the capacitor C1. The other end of the inductor L1 is connected to the drain of the switch element Q2, and the source of the switch element Q2 is connected to the second output terminal of the rectifying unit RF. The gate of the switch element Q1 is connected to the gate of the switch element Q2.

[Operation of Constant Current Power Supply Device 1]
The constant current power supply device 1 having the above configuration controls the power factor improvement circuit 30 by the control unit 10 that controls the constant current circuit 20 to perform not only constant current control but also power factor improvement control. Specifically, similarly to the constant current power supply device 100, the control unit 10 controls the switch element Q1 according to the drain current of the switch element Q1, so that the switch element according to the output current of the constant current power supply device 1 is obtained. Q1 is controlled, constant current control is performed, and a constant current is output. Further, the control unit 10 controls the switch element Q2 in synchronization with the switch element Q1, performs power factor improvement control, and improves the power factor.

  As described above, the gate of the switch element Q1 is connected to the gate of the switch element Q2. For this reason, since the gate signal applied to the gate of the switch element Q1 is also applied to the gate of the switch element Q2, the switch element Q2 switches in synchronization with the switch element Q1.

  The power factor correction circuit 30 including the switch element Q2 is configured by a so-called boost type chopper circuit. For this reason, the DC voltage output from the first output terminal of the rectifying unit RF is boosted by the power factor correction circuit 30, supplied to the constant current circuit 20, and charges the capacitor C2. The capacitor C2 is charged with a current supplied through the diode D2 when the constant current power supply device 1 is started.

  FIG. 2 is a timing chart of the constant current power supply device 1 during steady operation.

V _Vin indicates an AC voltage input from the AC power source Vin, that is, an input voltage, and I _Vin indicates an AC current input from the AC power source Vin, that is, an input current.

V _C1 indicates the voltage of one electrode of the capacitor C1. One electrode of the voltage _{V C1} of the capacitor C1 is a voltage after rectifying the input voltage _{V Vin} by the rectifying unit RF. Therefore, one of the waveform of the voltage _{V C1} of the electrodes of the capacitor C1 becomes rectified waveform of the input voltage _{V Vin.}

VGS _Q1 and VGS _Q2 indicate the gate-source voltages of the switching elements Q1 and Q2, respectively. Since the gate signal applied to the gate of the switch element Q1 is also applied to the gate of the switch element Q2, the waveform of the gate-source voltage VGS _Q1 of the switch element Q1 and the gate-source voltage VGS of the switch element Q2 are displayed. It is equal to the waveform of _Q2 , and becomes H level voltage VH or L level voltage VL synchronously.

_IL1 indicates a current flowing from one end of the inductor L1 to the other end. The current _IL1 flowing from one end to the other end of the inductor L1 changes according to the switching of the switch element Q2.

V _C2 indicates the voltage of one electrode of the capacitor C2. Voltage _{V C2} of the one electrode of the capacitor C2 will vary according to the input voltage _{V Vin.} However, the amplitude of the voltage V _C2 is significantly narrower than the amplitude of the input voltage V _Vin .

_IL2 indicates a current flowing from one end of the inductor L2 to the other end. The current _IL2 flowing from one end to the other end of the inductor L2 varies according to the switching of the switch element Q1.

I _LED indicates an average current flowing through each of the light emitting diodes LED1 to LEDn. This average current I _LED is equal to the average of the current I _L2 flowing from one end of the inductor L2 to the other end.

FIG. 3 is a timing chart of the constant current power supply device 1 when the input voltage V _Vin suddenly changes.

In FIG. 3, the input voltage V _Vin suddenly changes during the period from time t1 to time t2, and the amplitude of the input voltage V _Vin is smaller than in other periods. For this reason, in the period from the time t1 to the time t2, the voltage V _C1 of one electrode of the capacitor _C1 is lower than that in the other period. However, during the period from time t1 to t2, the stored energy is supplied to the constant current circuit 20 from the capacitor C2 charged during the steady operation. Therefore, in the period from time t1 to t2, since the capacitor C2 from being discharged, although the voltage _{V C2} of the one electrode of the capacitor C2 is reduced, the current _{I L2} flowing from one end of the inductor L2 at the other end, the light emitting The average current I _LED flowing through each of the diodes LED1 to LEDn is the same as that during steady operation.

  According to the above constant current power supply device 1, the following effects can be obtained.

  The constant current power supply device 1 also controls the power factor correction circuit 30 by the control unit 10 that controls the constant current circuit 20. For this reason, since the control part 10 is shared by the constant current circuit 20 and the power factor correction circuit 30, the constant current power supply device 1 can be reduced in size.

  Moreover, the constant current power supply device 1 performs power factor improvement control by the power factor improvement circuit 30 to improve the power factor. For this reason, high frequency regulation can be satisfied.

Further, in the above-described constant current power supply device 100, the capacitance of the capacitor C4 related to the stability of the constant current output with respect to the fluctuation of the input voltage V _Vin cannot be simply increased due to the high frequency regulation. On the other hand, since the constant current power supply device 1 can satisfy the high frequency regulation as described above, the capacitance of the capacitor C2 related to the stability of the constant current output with respect to the fluctuation of the input voltage V _Vin can be increased. it can. For this reason, the stability of the constant current output with respect to the fluctuation of the input voltage can be ensured.

  In addition, since the constant current power supply device 1 also serves as the control unit 10 as described above, the power factor correction circuit 30 is controlled at the constant current control timing in the constant current circuit 20. For this reason, since the power factor correction control in the power factor correction circuit 30 is not performed at the optimal timing for the power factor improvement, the output voltage of the power factor correction circuit 30 is dependent on the input voltage. It will be. However, since the constant current circuit 20 is provided behind the power factor correction circuit 30, the output current of the constant current power supply device 1 is after the constant current control in the constant current circuit 20 is performed. Therefore, the constant current power supply device 1 can output a constant current.

  In the constant current power supply device 1, the output voltage of the power factor correction circuit 30 is a direct current, and this direct current voltage is input to the constant current circuit 20. For this reason, the output current ripple of the constant current power supply device 1 can be suppressed.

  In the constant current power supply device 1, the input voltage of the constant current circuit 20 is a direct current as described above. For this reason, the duty ratio of the gate signal transmitted from the control unit 10 to the switch element Q1 is substantially constant, and the switch element Q2 operates based on the gate signal transmitted to the switch element Q1. The ratio is also substantially constant. Therefore, since the input current of the constant current power supply device 1 is proportional to the input voltage of the constant current power supply device 1, the power factor of the constant current power supply device 1 can be improved.

  Further, if the switch element Q2 is also used as the switch element Q1, the constant current power supply device 1 can be further reduced in size. However, when combined, not only the output current of the constant current power supply device 1 but also the current flowing through the switch element Q2 flows through the switch element Q1. For this reason, since the control part 10 cannot detect the output current of the constant current power supply device 1 accurately, it cannot perform the constant current control accurately and cannot output the constant current. However, since the constant current power supply device 1 includes the switch element Q1 and the switch element Q2 separately, the control unit 10 can accurately detect the output current of the constant current power supply device 1. Therefore, the constant current power supply device 1 can perform constant current control accurately and can output a constant current.

In the constant current power supply device 1, the power factor correction circuit 30 is configured by a so-called boost type chopper circuit. For this reason, the output voltage of the power factor correction circuit 30 is higher than the input voltage V _Vin . Therefore, more energy can be stored in the capacitor C2 than in the case where the power factor correction circuit 30 configured by the boost type chopper circuit is not provided, and the constant current circuit 20 is transferred from the capacitor C2 over a long period of time. Since electric power can be supplied, the constant current power supply device 1 can output a constant current for a long time.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the constant current circuit 20 is configured by a so-called step-down circuit, but is not limited thereto, and may be configured by a step-up circuit.

  In the above-described embodiment, the constant current power supply device 1 supplies a constant current to the light emitting diodes LED1 to LEDn. However, the present invention is not limited to this, and supplies a constant current to a device that requires a constant current, such as a motor. it can.

DESCRIPTION OF SYMBOLS 1,100; Constant current power supply device 10; Control part 20; Constant current circuit 30; Power factor improvement circuit C1-C4; Capacitor D1-D3; Diode L1, L2; Inductor Q1, Q2; LED1-LEDn: Light-emitting diode

Claims (3)

A constant current power supply device for supplying a constant current to a load,
A constant current circuit that outputs a constant current;
A power factor correction circuit provided on the input side of the constant current power supply device from the constant current circuit;
Control means for controlling the constant current circuit,
The power factor correction circuit operates based on a control signal transmitted from the control means to the constant current circuit. The constant current circuit is:
A first switch element in which a current flowing through the load is input to an input terminal;
Current-voltage conversion means for converting the voltage of the current flowing through the first switch element,
The control means transmits a control signal to the first switch element based on the voltage converted by the current-voltage conversion means,
The constant current power supply device according to claim 1, wherein the power factor correction circuit includes a second switch element that is chopper-controlled based on the control signal. A capacitor that is charged by the output of the power factor correction circuit and outputs the charged energy to the constant current circuit;
The constant current power supply device according to claim 1, wherein the power factor correction circuit includes a booster circuit.

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