JP2011217561A - Switched capacitor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switched capacitor device for transmitting an electrical energy to a load in a stable state while suppressing a loss in a process of transmitting the electrical energy to the load.SOLUTION: The switched capacitor device includes: a control part 1 for alternately executing charge control for charging a capacitor C by turning on a switch Q1 for charge and turning off a switch Q2 for discharge; and discharge control for discharging the capacitor by turning off the switch Q2 for charge and turning on the switch Q2 for discharge. A charge circuit for charging the capacitor C is formed by connecting the switch Q1 for charge, the capacitor C, and the load 2 between positive and negative electrodes of a DC power source E. The switch Q2 for discharge and the load 2 are connected in series between one end and the other end of the capacitor C, thus forming a discharge circuit for discharging the capacitor C. The control part 1 controls a time ratio of the switch Q1 for charge to the switch Q2 for discharge, and controls a value of current flowing in the load 2 by discharge of the capacitor C.

Description

  The present invention relates to a switched capacitor device.

  In a small-sized device such as a cellular phone, a switched capacitor that lowers the voltage value of DC power output from a DC power source such as a battery is used to drive an element such as an LED. This type of switched capacitor is exemplified in Patent Document 1.

  FIG. 20 shows a circuit configuration of this type of switched capacitor. In the switched capacitor 100, when the capacitors C101 to C104 are discharged and the inter-terminal voltage decreases, the switching elements Q201 to Q204 are simultaneously turned off, and the switching elements Q100 and Q101 are simultaneously turned on.

  Then, a charging path is formed from the positive electrode of the DC power source E to the negative electrode through the capacitor C101, the charging diode D101, the capacitor C102, the charging diode D102, the capacitor C103, the charging diode D103, and the capacitor C104. Thereby, charging of the capacitors C101 to C104 is started.

  When the voltage between terminals of each capacitor rises due to charging of the capacitors C101 to C104, the switching elements Q100 and Q101 are simultaneously turned off and the switching elements Q201 to Q204 are simultaneously turned on.

  Then, a discharge path is formed from one end of the capacitor C101 to the other end of the capacitor C101 through the smoothing capacitor Co and the discharge diode D201, and the discharge of the capacitor C101 is started. Further, a discharge path is formed from one end of the capacitor C102 to the other end of the capacitor C102 through the smoothing capacitor Co and the discharge diode D202, and the discharge of the capacitor C102 is started.

  Further, a discharge path is formed from one end of the capacitor C103 to the other end of the capacitor C103 through the smoothing capacitor Co and the discharge diode D203, and the discharge of the capacitor C103 is started. In addition, a discharge path is formed from one end of the capacitor C104 to the other end of the capacitor C104 through the smoothing capacitor Co and the discharge diode D204, and the discharge of the capacitor C104 is started.

  As a result, the smoothing capacitor Co is charged, and power having a magnitude corresponding to the inter-terminal voltage of the smoothing capacitor Co generated at that time is applied to the LED 200.

  By repeating the above operation, the LED 200 can obtain DC power that is stepped down to a voltage value smaller than the voltage value of the DC power output from the DC power source E.

JP 2003-33009 A

  In general, a switched capacitor is said to be able to realize the same function as a voltage drop by a resistor without loss of electrical energy.

  In practice, however, there is a loss of electrical energy in the switched capacitor. This will be described below.

  The inventor investigated the loss of electrical energy between the two capacitors by assembling the charge / discharge circuit shown in FIG. The capacitance of each capacitor is the same.

  In the circuit shown in FIG. 21, when the switching element SW100 is turned on while the switching element SW100 is turned on, the capacitor C200 is charged. Thereafter, when switching element SW100 is turned off and switching element SW200 is turned on, capacitor C200 is discharged and capacitor C300 is charged.

  FIG. 22 is a diagram illustrating a simulation result of a voltage between terminals of each capacitor and a current flowing between the capacitors when charging and discharging are performed in the charging / discharging circuit of FIG. In the following description, it is assumed that the impedance of the entire circuit, such as the impedance of wiring, is small.

  Time t1 is the time when the switching element SW200 is turned off while the switching element SW100 is turned on. At this time, the capacitor C200 is charged and the inter-terminal voltage V200 of the capacitor C200 rises to the potential difference Vo (here, 10V) of the DC power source E. Note that the current value of the current I200 flowing between the capacitor C200 and the capacitor C300 is 0 because the switching element SW200 is off.

  Time t2 is the time when switching element SW200 is turned on while switching element SW100 is turned off. At this time, discharging of the capacitor C200 is started and charging of the capacitor C300 is started. Finally, the inter-terminal voltages V200 and V300 of each capacitor are equal to the voltage value Vo of the DC power output from the DC power source E. It becomes 1 / 2Vo (here 5V) which is half.

  At time t2, the switching element SW100 is turned off, while the switching element SW200 is turned on. At the instant when the switching element SW200 is turned on, the impedance of the entire circuit, such as the wiring impedance, is reduced. In addition, a current having a current value close to infinity flows instantaneously.

Here, attention is focused on the amount of change in electrostatic energy of the charge / discharge circuit after time t1. Assuming that the capacitance of each capacitor is C, at time t1 <time t <time t2, the formula A of electrostatic energy P1 of the capacitor C100 = (1/2) × C × Vo ² is established.

On the other hand, at time t <b> 2 <time t, the formula B of electrostatic energy P <b> 2 of the capacitor C <b> 100 = (1/2) × C × (Vo / 2) ² = (1/8) × C × Vo ² is established. Further, the electrostatic energy P3 of the capacitor C200 = (1/2) × C × (Vo / 2) ² = (1/8) × C × Vo ² is established. Thereby, the formula D of the total electrostatic energy P2 + P3 = (1/4) × C × V ^{2 of} each capacitor is established.

  Referring to these equations A to D, it can be seen that half of the electrostatic energy P1 of the capacitor C100 is lost in the process in which the electrostatic energy P1 is distributed to each capacitor.

  Such energy loss is caused by the fact that a current having a current value close to infinity is instantaneously flowing between the capacitors C200 and C300 at time t2.

  Thus, in order to prevent a current having a current value close to infinity from flowing instantaneously between the capacitors C200 and C300 at the time t2, a resistor is provided between the capacitors C200 and C300. It is possible to intervene.

  However, when a resistor is interposed, part of the electrostatic energy is changed to Joule heat in the resistor in the process of transferring the electrostatic energy from the capacitor C200 to the capacitor C300. Therefore, interposing a resistor is not an effective means of suppressing power loss.

  Further, from the viewpoint of the current flowing into the capacitor C200, when the capacitor C200 is charged by the DC power source E, a power loss occurs as in the case where the capacitor C200 is discharged and the capacitor C300 is charged. Can be analogized.

That is, assuming that the potential difference in the DC power source E is V, the resistance component such as wiring is r, the capacitance of the capacitor C200 is C, and the potential of the capacitor C200 is Vc1, the charging current ic1 of the capacitor C200 = (V−Vc1) × e. Formula E consisting of ^{−t / c1 × r} / r is established.

  Referring to Equation E, if the resistance component r of the wiring or the like is zero, a current having an infinite peak value flows instantaneously at the start of charging of the capacitor C200, while if the resistance component r exists, the direct current Part of the electrical energy from the power source E is released to the outside as Joule heat in the resistance component r.

  Therefore, it can be seen that when the capacitor C200 is charged by the DC power source E, a loss similar to that in the case of charging the capacitor C300 by discharging the capacitor C200 occurs.

  When this is applied to the switched capacitor in FIG. 20, it can be seen that energy loss occurs when the capacitors C101 to C104 are charged with the DC power output from the DC power source E. Thus, it can be seen that power loss occurs in the process in which the electrical energy from the DC power source E is transmitted to the LED 200.

  Therefore, it is desired to suppress a loss that occurs in the process in which the electric energy from the DC power source E is transmitted to the LED 200.

  In the switched capacitor device of FIG. 20, when the voltage value of the DC power from the DC power source E varies due to disturbance, the current value of the current flowing through the LED 2 varies. In order to drive a solid state light emitting device such as the LED 2, it is desirable that the current value of the current flowing through the solid state light emitting device is stable.

  Therefore, it is possible to suppress the current value of the current flowing through the LED 2 from fluctuating due to the fluctuation of the voltage value of the DC power from the DC power source E, and to transmit the electric energy from the DC power source E to the load in a stable state. desired.

  The present invention has been made in view of the above circumstances, and is capable of transmitting the electrical energy to the load in a stable state while suppressing loss that occurs in the process of the electrical energy being transmitted to the load. It is an object to provide a data device.

  A switched capacitor device according to one aspect of the present invention is a switched capacitor device for driving a load, and includes a DC power source that outputs DC power, a capacitor that receives the DC power and performs charging and discharging, and ON / OFF A charging switch for controlling charging in the capacitor by operating; a discharging switch for controlling discharging in the capacitor by turning on and off; turning on the charging switch and turning off the discharging switch; A charging unit that charges the capacitor, and a controller that alternately turns off the charging switch and discharges the capacitor by turning on the discharging switch and discharging the capacitor. Between the positive electrode and the negative electrode of the power source, the charging switch, the capacitor, and A charging circuit for charging the capacitor is formed by connecting the load in series, and the discharging switch and the load are connected in series between one end and the other end of the capacitor. A discharge circuit for discharging the capacitor is formed by being connected, and the control unit controls a time ratio between the charge switch and the discharge switch, and the load is discharged by discharging the capacitor. The current value of the current flowing through the control circuit is controlled (claim 1).

  According to this configuration, a charging switch, a capacitor, and a load are connected in series between the positive electrode and the negative electrode of the DC power source, thereby forming a charging circuit for charging the capacitor.

  As a result, a current that instantaneously flows through the charging circuit at the start of charging of the capacitor flows through the load. Therefore, the current value of the current that instantaneously flows through the charging circuit at the start of charging of the capacitor is suppressed by the impedance of the load. Further, if there is no load, a part of the electric energy that is lost as a loss can be used as the effective power of the load.

  Further, according to this configuration, the control unit controls the current ratio of the current flowing through the load by discharging the capacitor by controlling the time ratio of the charging switch and the discharging switch.

  As a result, the current flowing through the load by discharging the capacitor can be eliminated without adding a dedicated component such as a switching element for controlling the amount of current flowing into the load or a constant current circuit for making the amount of current flowing through the load constant. The current value can be held at a constant value.

  As a result, the electric energy from the DC power source is not lost by the dedicated component as when a dedicated component is added, and the current value of the current flowing through the load is kept constant at a low cost. can do.

  As described above, according to this configuration, it is possible to transmit the electric energy in a stable state to the load while suppressing a loss that occurs in the process in which the electric energy is transmitted to the load without loading a dedicated component. it can.

  In the above configuration, a plurality of the discharge switches are arranged, and a plurality of the capacitors are further connected in series between the positive electrode and the negative electrode of the DC power source, and one end of each capacitor It is preferable that a plurality of the discharge circuits are formed by connecting each of the discharge switches and the load in series with the other end.

  According to this configuration, in the charging circuit formed between the positive electrode and the negative electrode of the DC power source, a plurality of capacitors are connected in series, and each discharging capacitor is connected between one end and the other end of each capacitor. A plurality of discharge circuits for discharging each capacitor are formed by connecting the switch and the load in series.

  As a result, by charging each capacitor, the voltage between terminals generated in each capacitor becomes the voltage value of the DC power by the DC power source divided according to the number of capacitors. Further, at the time of discharging each capacitor, the same potential difference as the voltage between terminals of each capacitor is generated at both ends of the load.

  Therefore, at the time of discharging each capacitor, a voltage across the terminals that is divided according to the number of capacitors and is the same as the voltage value by the DC power source is applied to the load. Therefore, the step-down ratio can be changed as appropriate according to the number of capacitors.

  In the above configuration, a plurality of charging diodes arranged in series adjacent to the load side in each capacitor and connected so that the charging current of each capacitor is in the forward direction are arranged, Each discharging switch is connected in parallel to each capacitor and a charging diode adjacent to the load side of each capacitor, a terminal of the load opposite to the charging diode, and each capacitor And a connection point between each charging diode and a discharging diode in a forward direction in the discharging direction of each capacitor, and when the discharge control is executed, each capacitor is Via a plurality of discharge circuits comprising one or more of the plurality of discharge switches, the load, and each discharge diode. It is preferred to electricity (claim 3).

  According to this configuration, each discharging switch is connected in parallel to each capacitor and a charging diode that is adjacent to the load side of each capacitor and in which the charging current of each capacitor is in the forward direction.

  Thereby, when each capacitor is charged, the voltage between the terminals of each capacitor becomes a value obtained by dividing the voltage value of the DC power from the DC power source according to the number of capacitors.

  Thereby, since the voltage applied to the discharge switch corresponding to the capacitor at the time of charging each capacitor becomes the voltage value of the DC power by the DC power source divided according to the number of capacitors, A switching element with a low breakdown voltage can be used.

  In the above configuration, a plurality of charging diodes arranged in series adjacent to the load side in each capacitor and connected so that the charging current of each capacitor is in the forward direction are arranged, When the number of combinations of each capacitor and the charging diode adjacent to the load side of each capacitor is n (where n is a positive integer), the most load side combination and the most load side combination The discharge switches are connected in parallel to each of the n-1 combinations up to the i-th combination (where i is an integer of 2 to n), and for the charging in the load Between the terminal opposite to the diode and the connection point between each capacitor and each charging diode, the direction of the forward direction in the discharging direction of each capacitor When each of the discharge diodes is connected and the discharge control is executed, each capacitor discharges via a plurality of discharge circuits including the discharge switches, the load, and the discharge diodes. (Claim 4).

  According to this configuration, the capacitor located at the most load side and the capacitor and the charging diode, and the capacitor located at the i th (where i is an integer from 2 to n) counted from the most load side combination. Each of the discharging switches is connected in parallel to each of n-1 combinations up to the combination of the charging diode and the charging diode.

  When the discharge control is executed, each capacitor discharges through each discharge circuit in which one or more of the plurality of discharge switches, a load, and each discharge diode are connected in series.

  For this reason, the magnitude of the voltage applied to each discharge switch during discharge control is not a magnitude corresponding to each capacitor, but the current flowing through each discharge switch is a current due to the discharge of one capacitor. Therefore, the current value of the current flowing through each discharge switch can be equalized to the current value of the current due to the discharge of one capacitor.

  The above configuration further includes an inductor arranged in common to the charging circuit and the discharging circuits, and the control unit sets a time ratio of the charging switch to 100 / (1 + n) (%) or more. While controlling within the range of less than%, it is preferable to control the duty ratio of the discharge switch within the range of more than 0% and not more than 100 n / (1 + n) (%).

  According to this configuration, since the control unit controls the charging switch and the discharging switch within the above range, the charging switch and the charging switch and the discharging switch are not used without using a separate unit for controlling the current value of the current flowing through the load. The load current value can be controlled so that the maximum current value of the current flowing through the load can be obtained while suppressing the occurrence of switching loss in the discharge switch.

  A switched capacitor device according to another aspect of the present invention is a switched capacitor device for driving a load, and includes a DC power source that outputs DC power, and a plurality of charging and discharging devices that receive the DC power and perform charging and discharging. A capacitor, a charging switch for controlling charging in each capacitor by on / off operation, a plurality of discharging switches for controlling discharge in each capacitor by on-off operation, and turning on the charging switch And charging control for turning off each discharging switch to charge each capacitor, and discharging control for turning off each charging switch and turning on each discharging switch to discharge each capacitor alternately. A control unit, and between the positive electrode and the negative electrode of the DC power source, A charging circuit for charging the capacitor is formed by connecting the power switch, the capacitors, and the load in series, and for each capacitor, between one end and the other end of the capacitor. The discharge switch and the load are connected in series to form a discharge circuit for discharging the capacitor, and an inductor is disposed in common with the charge circuit and the discharge circuit. The control unit controls the drive frequency of the charging switch and each discharging switch to control the current value of the current flowing through the load by discharging the capacitor. ).

  According to this configuration, the driving frequency of the charging switch and each discharging switch is controlled to control the current value of the current flowing through the load by discharging the capacitor. The current value of the current can be controlled without using any other means.

  In the above configuration, when the voltage value of the DC power by the DC power source changes, the voltage value is each of a plurality of voltage values obtained in the process of changing the voltage value. When the drive frequency of the charging switch and each discharging switch is changed under the conditions, the current value of the current flowing through the load at the time of discharging each capacitor is preset, and the control unit When the voltage value of the DC power of the DC power source changes, and the current value of the current flowing through the load changes when the capacitors are discharged, the voltage value of the DC power changes after the change. Under the condition that the voltage value, the current value before the change is obtained as the current value of the current flowing through the load, obtain the driving frequency of the charging switch and each discharging switch, It is preferable to drive the charge switch and the switch each discharged at the driving frequency (Claim 7).

  According to this configuration, when the voltage value of the DC power of the DC power source changes and the current value of the current flowing through the load changes when each capacitor is discharged, the voltage value after the change after the voltage value of the DC power changes is changed. The charging switch and each discharging switch are driven at the driving frequency of the charging switch and each discharging switch that can obtain the current value before the change as the current value of the current flowing through the load under the condition of the voltage value.

  As a result, even if the current value of the current flowing through the load changes when each capacitor is discharged due to fluctuations in the power source of the DC power source, the charging switch and each discharging switch are driven at a driving frequency that can obtain the current value before the change Thus, the current value flowing through the load returns to the current value before the change.

  Therefore, it is possible to appropriately control the current value of the current flowing through the load when each capacitor is discharged, without adding a separate configuration for controlling the current value flowing through the load, in response to the power supply fluctuation of the DC power source .

  A switched capacitor device according to still another aspect of the present invention is a switched capacitor device for driving a load, and includes a plurality of DC power sources that output DC power, and a plurality of charging and discharging devices that receive the DC power. A capacitor, a charging switch for controlling charging in the capacitor by on / off operation, a plurality of discharging switches for controlling discharging in the capacitor by on / off operation, and turning on the charging switch Charging control for charging each capacitor by turning off each discharging switch and discharging control for discharging each capacitor by turning off each charging switch and turning on each discharging switch are alternately executed. A control unit, wherein the capacitors are connected in series with the charging switch. And a first series circuit connected to the load is connected between a positive electrode and a negative electrode of the DC power source as a charging circuit for charging each capacitor, and one end and the other end of each capacitor A plurality of discharge circuits for discharging the capacitors are formed so that a series circuit of the discharge switches and the load is connected to each other. In each of the discharge circuits, The discharging switch is connected in parallel to one end and the other end of each capacitor, and the control unit is configured to turn one or more of the discharging switches while the charging switch is turned on. The discharge switch is turned on, and the current value of the current flowing through the load is controlled by discharging the capacitor (Claim 8).

  According to this configuration, a series circuit including a charging switch, each capacitor, and a load is connected as a charging circuit for charging the capacitor between the positive electrode and the negative electrode of the DC power source.

  As a result, a current that instantaneously flows through the charging circuit at the start of charging of each capacitor flows through the load. Therefore, the current value of the current that instantaneously flows through the charging circuit at the start of charging of each capacitor is suppressed by the impedance of the load. Further, if there is no load, a part of the electric energy that is lost as a loss can be used as the effective power of the load.

  Furthermore, according to this configuration, each discharging switch is connected in parallel to one end and the other end of each capacitor. Further, one or more discharge switches among the discharge switches are turned on while the charge switches are turned on.

  Thus, when the charging switch is on, one or more discharging switches are turned on, and both ends of the capacitors corresponding to the one or more discharging switches are short-circuited. As a result, the number of capacitors that can be charged is reduced by the number of capacitors corresponding to the discharging switch that is turned on.

  As a result, the voltage between the terminals when the chargeable capacitor is charged increases as the chargeable capacitor decreases, and as a result, the current value of the current flowing through the load increases.

  Therefore, while the charging switch is turned on, one or more of the discharging switches are turned on to control the current value of the current flowing through the load, so that the electric energy from the DC power source is loaded. The amount transmitted to can be controlled.

  As a result, the current flowing through the load by discharging the capacitor can be eliminated without adding a dedicated component such as a switching element for controlling the amount of current flowing into the load or a constant current circuit for making the amount of current flowing through the load constant. The current value can be held at a constant value.

  As a result, the electric energy from the DC power source is not lost by the dedicated component as when a dedicated component is added, and the current value of the current flowing through the load is kept constant at a low cost. can do.

  As described above, according to this configuration, it is possible to transmit the electric energy in a stable state to the load while suppressing a loss that occurs in the process in which the electric energy is transmitted to the load without loading a dedicated component. it can.

  In the above configuration, it is preferable that the control unit further controls a time ratio of the charging switch and each discharging switch to control a current value of a current flowing through the load by discharging each capacitor. Item 9).

  According to this configuration, the control unit can further control the current ratio of the current flowing through the load by further controlling the time ratio of the charging switch and each discharging switch. Therefore, the electric energy from the DC power source can be transmitted to the load in a more stable state.

  In the above configuration, the load is preferably a solid light emitting element.

  In order to cause the solid light emitting element to emit light stably, it is important to maintain the current value of the current flowing through the solid light emitting element at a constant value.

  According to this configuration, since the load is a solid state light emitting device, the current value of the current flowing through the solid state light emitting device is held at a constant value by discharging the capacitor. Thereby, a solid light emitting element can be light-emitted stably.

  According to the present invention, the electrical energy can be transmitted to the load in a stable state while suppressing a loss that occurs in the process in which the electrical energy is transmitted to the load without loading a dedicated component.

It is the figure which showed the reference example of the switched capacitor apparatus. It is the figure which showed an example of the circuit structure of the switched capacitor apparatus which concerns on 1st Embodiment, and is a figure in case the number of capacitors is one. FIG. 3 is a circuit configuration diagram when a smoothing capacitor and an inductor are added to the switched capacitor device shown in FIG. 2. It is a figure showing an example of circuit composition of a switched capacitor device concerning a 1st embodiment, and is a figure in case the number of capacitors is two or more. It is a figure showing an example of circuit composition of a switched capacitor device concerning a 1st embodiment, and is a figure in case the number of capacitors is two or more. It is the table | surface which showed the relationship between the voltage value of a direct-current power source, the number of capacitors, and the largest series number of LED for the electrical energy by a direct-current power source to be suitably transmitted to LED. It is the figure which showed an example of the specific structure of the control part in 1st Embodiment. It is the figure which showed an example of the specific structure of the electric current value detection part used in combination with the control part shown in FIG. It is the figure which showed the waveform of the various signals used in the control part shown in FIG. It is a timing chart for demonstrating the time ratio of the switch for charge, and the switch for discharge. It is the figure which showed an example of the output characteristic of a switched capacitor apparatus in case the number of switched capacitors is one. It is the figure which showed an example of the output characteristic of a switched capacitor apparatus in case the number of switched capacitors is two or more. It is the figure which showed an example of the output characteristic of a switched capacitor apparatus in case the number of switched capacitors is two or more. It is the figure which showed an example of the output characteristic at the time of changing the drive frequency of the switch for charge and the switch for discharge on the conditions from which the voltage value of a DC power source differs, respectively. It is the figure which showed an example of the circuit structure of the switched capacitor apparatus which concerns on 2nd Embodiment of this invention. It is the figure which showed the other example of the circuit structure of the switched capacitor apparatus which concerns on 2nd Embodiment of this invention. It is the figure which showed an example of the waveform of the pulse signal output from a control part in 2nd Embodiment. It is the figure which showed an example of the structure of the control part in 2nd Embodiment. It is the figure which showed the other example of the structure of the control part in 2nd Embodiment. It is the figure which showed the conventional switched capacitor apparatus. It is a figure for demonstrating the energy loss in the conventional switched capacitor apparatus. It is a figure showing the energy loss in the conventional switched capacitor apparatus.

  For example, a switched capacitor shown in FIG. 1 can be used as a switched capacitor device capable of suppressing loss generated in the process of transmitting electric energy from a DC power source to a load and transmitting the electric energy to the load in a stable state. Apparatus.

  A switched capacitor device B1 shown in FIG. 1A includes a switched capacitor SC for stepping down a DC voltage output from a DC power source E and transmitting the voltage to an LED (load) 2. The switched capacitor SC includes a charging switch Q102, a capacitor C, a charging diode D1, a discharging switch Q103, and a discharging diode D2.

  In the switched capacitor device B1, a series circuit composed of a charging switch Q102, a capacitor C, a charging diode D1, an LED2, and a switching element Q is used as a charging circuit for charging the capacitor C. It is connected between the negative electrode.

  In the switched capacitor device B1, a discharging switch Q103 made of a MOSFET is connected in parallel with a series circuit made up of a capacitor C and a charging diode D1.

  Then, the discharge diode D2 has a connection point between the capacitor C and the charging diode D1 in a state where the cathode terminal of the discharge diode D2 faces the connection point between the capacitor C and the charging diode D1. It is connected between the negative electrode of the DC power source E.

  Thus, a discharge circuit is formed from one end of the capacitor C to the other end of the capacitor C via the discharge switch Q103, LED2, switching element Q, and discharge diode D2.

  According to the switched capacitor device B1, the LED 2 is arranged in the charging path. Therefore, the current that instantaneously flows through the charging path at the start of charging of the capacitor C is suppressed by the impedance of the LED 2. Moreover, since the electric power consumed by LED2 is utilized for light emission of LED2, electric power is used effectively.

  Thereby, the energy loss at the time of transmitting the electrical energy generated by the DC power source E to the capacitor C can be suppressed. As a result, energy loss in the process of transmitting electrical energy generated by the DC power source E to the LED 2 can be suppressed.

  The switching element Q forms and cuts off the current path of the LED 2 by performing an on / off operation. The switching element Q is driven by a PWM (Pulse Width Modulation) signal, and the on / off timing is determined by the duty ratio of the PWM signal. Therefore, the current path of the LED 2 is formed and cut at a timing according to the duty ratio of the PWM signal. Thereby, the current value of the current flowing through the LED 2 is controlled by the on / off operation of the switching element Q.

  As a result, the magnitude of the DC power transmitted to the LED 2 can be controlled by the on / off operation of the switching element Q. Therefore, in the switched capacitor device B1, the electric energy from the DC power source E can be transmitted to the LED 2 in a stable state.

  Further, in the switched capacitor device B2 shown in FIG. 1B, a switching element Q1 having the same function as the switching element Q is arranged in place of the switching element Q in the switched capacitor device B1 shown in FIG. In addition, a constant current circuit 6 including a switching element Q2, a comparator 3, a reference voltage source Vref, and a resistor r is disposed.

  Thereby, in the switched capacitor device B2, the loss caused in the process in which the electric energy from the DC power source E is transmitted to the LED 2 can be suppressed, and the electric energy from the DC power source E is supplied to the LED 2 by the constant current circuit 6. It can be transmitted in a stable state.

  As described above, according to the switched capacitor devices B1 and B2 shown in FIG. 1, a state in which the electric energy is stabilized in the LED 2 while suppressing loss that occurs in the process in which the electric energy from the DC power source E is transmitted to the LED 2 is suppressed. Can be transmitted.

  However, the switched capacitor devices B1 and B2 require a switching element and a constant current circuit in order to transmit electric energy to the LED 2 in a stable state. Thus, adding a new component such as a switching element or a constant current circuit may cause electric energy from the DC power source E to be lost due to the newly added component, which may increase costs. There is also.

  The present inventor has focused on such a point and has come up with a switched capacitor device as described below.

Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.
(First embodiment)
FIG. 2 is a diagram illustrating an example of a circuit configuration of the switched capacitor device according to the first embodiment, and is a diagram in the case where the number of capacitors is one. In the switched capacitor device D, a charging switch Q1, a capacitor C1, and a cathode terminal including a resistor r, LED2, and a MOSFET for detecting a current flowing through the LED2 are provided between the positive electrode and the negative electrode of the DC power source E. A charging circuit for charging the capacitor C1 through the LED 2 is formed by connecting the charging diode D1 facing the direction of the capacitor C1 in series.

  Further, a discharging switch Q2 made of a MOSFET is connected between both ends of the series circuit made up of the capacitor C and the charging diode D1 so as to be in parallel with the series circuit.

  Then, the discharge diode D2 has a connection point between the capacitor C1 and the charging diode D1 in a state where the anode terminal of the discharge diode D2 faces the connection point between the capacitor C1 and the charging diode D1. It is connected between the positive electrode of the DC power source E.

  Thus, a discharge circuit is formed from one end of the capacitor C1 to the other end of the capacitor C1 via the discharge diode D2, the resistor r, the LED2, and the discharge switch Q2.

  In the switched capacitor device D having such a configuration, the charging switch Q1 and the discharging switch Q2 are controlled by the control unit 1.

  The control unit 1 includes a charging switch Q1 and a discharging switch so that the discharging switch Q2 is off while the charging switch Q1 is on and the discharging switch Q2 is on while the charging switch Q1 is off. Pulses are alternately output to Q2.

  When the charging switch Q1 is turned on and the discharging switch Q2 is turned off, the DC power source passes from the positive electrode of the DC power source E through the LED 2, the charging diode D1, the capacitor C1, and the charging switch Q1. A charging path to the negative electrode of E is formed. Thereby, charging of the capacitor C1 is started.

  On the other hand, when the charging switch Q1 is turned off and the discharging switch Q2 is turned on, the other end of the capacitor C1 is passed from one end of the capacitor C1 through the discharging diode D2, LED2, and the discharging switch Q2. A discharge path leading to is formed. Thereby, the discharge of the capacitor C1 is started.

  According to the switched capacitor device D, the LED 2 is arranged in the charging path. Therefore, the current that instantaneously flows through the charging path at the start of charging of the capacitor C1 is suppressed by the impedance of the LED2. Moreover, since the electric power consumed by LED2 is utilized for light emission of LED2, electric power is used effectively.

  Thereby, the energy loss at the time of transmitting the electrical energy generated by the DC power source E to the capacitor C1 can be suppressed. As a result, energy loss in the process of transmitting electrical energy generated by the DC power source E to the LED 2 can be suppressed.

  FIG. 3 is a circuit configuration diagram when a smoothing capacitor and an inductor are added to the switched capacitor device shown in FIG.

  In the switched capacitor device D1, in the switched capacitor device D shown in FIG. 2, a smoothing capacitor Co and an inductor L are arranged to smooth the current flowing through the LED2. The function of the switched capacitor device D1 is the same as that of the switched capacitor device D shown in FIG.

  According to the switched capacitor device D shown in FIG. 2 and the switched capacitor device D1 shown in FIG. 3, the time ratio of the pulse signals output to the charging switch Q1 and the discharging switch Q2 is controlled to discharge the capacitor C1. Thus, the current value of the current flowing through the LED 2 is held at a constant value.

  In the switched capacitor devices D and D1, in order to control the time ratio of the pulse signal to the charging switch Q1 and the discharging switch Q2, the current value detection unit 4 that detects the current value of the current flowing through the LED 2, and the LED A voltage detector 5 for detecting the voltage between the terminals is arranged.

  2 and 3, the current value detector 4 detects the current value of the current flowing through the LED 2, so that a resistor r is provided between the positive electrode of the DC power source E and the anode terminal of the LED 2. Has been placed. Since the current flowing through the LED 2 passes through the resistor r, the resistor r causes a voltage drop due to the passed current. The current value detection unit 4 detects the magnitude of the voltage drop caused by the current flowing through the resistor r as the current value of the current flowing through the LED 2.

  4 and 5 are diagrams illustrating an example of a circuit configuration of the switched capacitor device according to the first embodiment, and are diagrams in a case where the number of capacitors is two or more. Here, FIG. 4A shows an example in which the number of capacitors is two. FIG. 4B shows an example in which the number of capacitors is three. FIG. 5A and FIG. 5B show an example in which the number of capacitors is four.

  A switched capacitor device D2 shown in FIG. 4A includes a circuit comprising a capacitor C1, a discharging switch Q21, a charging diode D11, and a discharging diode D21, a capacitor C2, a discharging switch Q22, a charging diode D12, And, it is configured by cascading two circuits composed of the discharge diode D22.

  In the switched capacitor device D2, when the charging switch Q1 is turned on while the discharging switches Q21 and Q22 are off, the resistor r, LED2, inductor L, charging diode D12, capacitor C2, The charging currents of the capacitors C1 and C2 flow through the diode D11, the capacitor C1, and the charging switch Q1. Thereby, the capacitors C1 and C2 are charged.

  Next, when the charging switch Q1 is turned off and the discharging switches Q21 and Q22 are turned on, the charge of the capacitor C1 is changed to the discharging diode D21, the resistor r, the LED2, the inductor L, and the discharging switches Q22 and Q21. It is discharged through.

  At the same time, the charge of the capacitor C2 is discharged through the discharge diode D22, the resistor r, the LED2, the inductor L, and the discharge switch Q22.

  Thereafter, the switched capacitor device D2 continuously supplies power to the LED 2 while repeating the above operation.

  A switched capacitor device D3 shown in FIG. 4B includes a circuit comprising a capacitor C1, a discharging switch Q2, a charging diode D1, and a discharging diode D2, a capacitor C2, a discharging switch Q22, a charging diode D12, In addition, a circuit composed of a discharge diode D22 and a circuit composed of a capacitor C3, a discharge switch Q23, a charge diode D13, and a discharge diode D23 are connected in cascade.

  In the switched capacitor device D3, when the charging switch Q1 is turned on while the discharging switches Q21 to Q23 are off, the resistor r, LED2, inductor L, charging diode D13, capacitor C3, charging are performed from the DC power source E. The charging currents of the capacitors C1 to C3 flow through the diode D12, the capacitor C2, the charging diode D11, the capacitor C1, and the charging switch Q1. Thereby, the capacitors C1 to C3 are charged.

  Next, when the charging switch Q1 is turned off and the discharging switches Q21 to Q23 are turned on, the charge of the capacitor C1 is changed to the discharging diode D21, the resistor r, the LED2, the inductor L, and the discharging switches Q23, Q22, And Q21.

  At the same time, the electric charge of the capacitor C2 is discharged through the discharge diode D22, the resistor r, the LED2, the inductor L, and the discharge switches Q23 and Q22.

  Furthermore, at the same time, the electric charge of the capacitor C3 is discharged through the discharging diode D23, the resistor r, the LED2, the inductor L, and the discharging switch Q23.

  Thereafter, the switched capacitor device D3 continuously supplies power to the LED 2 while repeating the above operation.

  A switched capacitor device D4 shown in FIG. 5A includes a circuit comprising a capacitor C1, a discharge switch Q21, a charging diode D11, and a discharging diode D21, a capacitor C2, a discharging switch Q22, a charging diode D12, A circuit composed of a discharge diode D22, a capacitor C3, a discharge switch Q23, a charge diode D13, and a circuit composed of a discharge diode D23, a capacitor C4, a discharge switch Q24, a charge diode D14, and It is configured by cascade-connecting four circuits each including a discharge diode D24.

  In this switched capacitor device D4, when the charging switch Q1 is turned on while the discharging switches Q21 to Q24 are off, the resistor r, LED2, inductor L, charging diode D14, capacitor C4, charging are performed from the DC power source E. The charging currents of the capacitors C1 to C4 flow through the diode D13, the capacitor C3, the charging diode D12, the capacitor C2, the charging diode D11, the capacitor C1, and the charging switch Q1. Thereby, the capacitors C1 to C4 are charged.

  Next, when the charging switch Q1 is turned off and the discharging switches Q21 to Q24 are turned on, the charge of the capacitor C1 is changed to the discharging diode D21, the resistor r, the LED2, the inductor L, and the discharging switches Q24, Q23, Discharged via Q22 and Q21.

  At the same time, the charge of the capacitor C2 is discharged through the discharge diode D22, the resistor r, the LED2, the inductor L, and the discharge switches Q24, Q23, and Q22.

  Furthermore, at the same time, the electric charge of the capacitor C3 is discharged through the discharge diode D23, the resistor r, the LED2, the inductor L, and the discharge switches Q24 and Q23.

  Furthermore, at the same time, the electric charge of the capacitor C4 is discharged through the discharging diode D24, the resistor r, the LED2, the inductor L, and the discharging switch Q24.

  Thereafter, the switched capacitor device D4 continuously supplies power to the LED 2 while repeating the above operation.

  According to the switched capacitor devices D2 to D5 described above, when each capacitor is charged, the voltage between terminals of each capacitor is divided according to the voltage value of the DC power from the DC power source E according to the number of capacitors. Value.

  As a result, the voltage applied to the discharge switch arranged corresponding to the capacitor when charging each capacitor becomes a voltage value by the DC power source E divided according to the number of capacitors. As the switch, a switching element with a low breakdown voltage can be used.

  Moreover, according to the switched capacitor apparatus D2-D5 shown above, in each discharge circuit, each capacitor is connected with LED2 in parallel. Thereby, at the time of discharge of each capacitor, the same potential difference as the voltage between terminals of each capacitor is generated at both ends of the LED 2.

  In the switched capacitor devices D2 to D5, as described above, the terminal voltage generated in each capacitor by charging is a voltage value by the DC power source E divided according to the number of capacitors.

  Thereby, when each capacitor is discharged, the voltage across the terminals, which is divided according to the number of capacitors and is the same as the voltage value by the DC power source E, is applied to both ends of the LED 2, as shown in FIGS. 2 and 3. As a result, a step-down output can be obtained as compared with the case where the number of capacitors is one.

  FIG. 5B shows an example in which the number of capacitors is four, in which one discharge switch corresponding to the capacitor is arranged in each capacitor to form a discharge path for each capacitor.

  That is, in the switched capacitor device D5 shown in FIG. 5B, the discharging switch Q21 includes the capacitor C1, the charging diode D11, the capacitor C2, the charging diode D12, the capacitor C3, the charging diode D13, the capacitor C4, and It is connected in parallel to a series circuit composed of a charging diode D14.

  Thus, a discharge path is formed from one end of the capacitor C1 to the other end of the capacitor C1 through the discharge diode D21, the resistor r, the LED2, the inductor L, and the discharge switch Q21.

  In the switched capacitor device D5, the discharging switch Q22 is connected in parallel to a series circuit including the capacitor C2, the charging diode D12, the capacitor C3, the charging diode D13, the capacitor C4, and the charging diode D14. .

  Thus, a discharge path is formed from one end of the capacitor C2 to the other end of the capacitor C2 via the discharge diode D22, the resistor r, the LED2, the inductor L, and the discharge switch Q22.

  Further, in the switched capacitor device D5, the discharge switch Q23 is connected in parallel to a series circuit including the capacitor C3, the charging diode D13, the capacitor C4, and the charging diode D14.

  This forms a discharge path from one end of the capacitor C3 to the other end of the capacitor C3 via the discharge diode D23, the resistor r, the LED2, the inductor L, and the discharge switch Q23.

  Further, in the switched capacitor device D5, the discharging switch Q24 is connected in parallel to a series circuit including the capacitor C4 and the charging diode D14.

  As a result, a discharge path is formed from one end of the capacitor C4 to the other end of the capacitor C4 through the discharge diode D24, the resistor r, the LED2, the inductor L, and the discharge switch Q24.

  As described above, according to the switched capacitor device D5 shown in FIG. 5B, when each capacitor is discharged, the charge of each capacitor is discharged through the discharge switch corresponding to the capacitor. The current flowing through the switch is made uniform.

  FIG. 6 shows that the inventor of the switched-capacitor devices D and D1 to D5 according to the first embodiment shows the DC power from the DC voltage source E under the condition that the ON voltage of one LED 2 is 3.3V. This is obtained by conducting an experiment in which each of the voltage value Vin, the number of capacitors, and the number of LEDs 2 is varied.

  In this experiment, the inventor obtained the voltage value Vin, the number of capacitors, and the number of LEDs 2 when the electric energy from the DC power source E is suitably transmitted to the LEDs 2, and is shown in FIG. It is summarized in a table. In the table of FIG. 6, “DC-Vin” indicates the average voltage value of the input DC power, and “AC-Vin” indicates the input AC power corresponding to each of the average voltage values of the input DC power. The effective voltage value is shown. For example, the voltage value of DC power obtained by rectifying and smoothing AC power of AC 100 Vrms (root mean square) is 140V. Therefore, the input DC power having an average voltage value of 140V corresponds to the input AC power having an effective voltage value of 100V.

  The table of FIG. 6 preferably corresponds to the average voltage value of DC power given as input (indicated as “DC-Vin” in FIG. 6) and the number of capacitors C (1 to 8). The maximum series number of LEDs 2 to which power is supplied is shown.

  In the table of FIG. 6, the LED 2 can appropriately emit light for each combination of the DC power voltage value “DC-Vin” and the AC power effective value “AC-Vin” in the row direction. The number of LEDs 2 is shown. In the column direction, the number of LEDs 2 that allow the LEDs 2 to emit light appropriately is shown according to the number of capacitors.

  From such a table, for example, when the voltage value “DC-Vin” of the DC power from the DC power source E is 140 V, in order to make the six LEDs 2 connected in series suitably emit light, It can be seen that the number 6 is optimal.

  Further, from the row L indicated by hatching in the table of FIG. 6, when the voltage value “DC-Vin” of the DC power is 140 V and the number of capacitors is reduced to 5, the LED 2 emits light suitably. It can be seen that the number of LEDs 2 that can be used is seven. On the other hand, from the row L indicated by hatching in the table of FIG. 6, when the voltage value “DC-Vin” of the DC power is 140 V and the number of capacitors is increased to 7, the LED 2 emits light suitably. It can be seen that the number of LEDs 2 that can be used is five.

  FIG. 7 is a diagram illustrating an example of a specific configuration of the control unit 1 in the first embodiment. FIG. 8 is a diagram showing an example of a specific configuration of the current value detection unit 4 used in combination with the control unit 1 shown in FIG. FIG. 9 is a diagram showing waveforms of various signals used in the control unit 1 shown in FIG.

  In the control unit 1 illustrated in FIG. 7, an oscillator IC1, resistors R1 and R2, and a capacitor C1 constitute an astable multivibrator. This astable multivibrator generates a rectangular wave reference signal (see FIG. 9A) having a predetermined frequency (for example, 1 MHz).

  The rectangular wave reference signal generated by the astable multivibrator charges the capacitor C2 through the buffer IC2 by a current mirror composed of the pair transistor Q1 and the resistor R3.

  Further, the rectangular wave reference signal generated by the astable multivibrator is inverted in phase by the NOT circuit IC3 to be an inverted reference signal (see (A) of FIG. 9), and is output to the switching element Q2. As a result, the switching element Q2 performs an on / off operation in synchronization with the inverted reference signal, short-circuits between the terminals of the capacitor C2, and discharges the capacitor C2.

  Since the inverted reference signal is obtained by inverting the phase of the rectangular wave reference signal, the phase is delayed by 180 degrees with respect to one period of the rectangular wave reference signal.

  As a result, the capacitor C2 is charged without short-circuiting between the terminals while receiving the pulse of the rectangular wave reference signal, and between the terminals is not receiving the pulse of the rectangular wave reference signal. Short circuit and discharge. As a result, a triangular wave (see FIG. 9C) is periodically generated.

  The triangular wave generated by the capacitor C2 is input to the inverting input terminal of the comparator IC4, and the current value of the current flowing through the LED 2 measured by the current value detection unit 4 is input to the non-inverting input terminal of the comparator IC4. The voltage value is input through the photocoupler PC.

  Here, the voltage value input to the non-inverting input terminal of the comparator IC4 is used as the threshold value Vth by the comparator IC4.

  In the comparator IC4, the voltage value of the triangular wave input to the inverting input terminal is compared with the voltage value (Vth) representing the current value of the current flowing through the LED 2 input to the non-inverting input terminal, and the voltage is applied to the inverting input terminal. When the voltage value of the input triangular wave is smaller than the voltage value (Vth) input to the non-inverting input terminal, a pulse is output. Thereby, the comparator IC4 outputs the pulse signal shown in FIG. 9D to one end of the AND circuit IC5.

  The AND circuit IC5 receives the pulse signal output from the comparator IC4 toward one end and the pulse signal output from the multivibrator toward the other end through the buffer IC2, and calculates the logical product of the voltage values at both ends. And output to the buffer IC 6 to which the charging switch Q1 is connected and the NOT circuit IC 7 to which the discharging switch Q2 is connected.

  As a result, the pulse signal shown in FIG. 9 (e) is output to the charging switch Q1, and the pulse signal shown in FIG. 9 (f) is output to the discharging switch Q2. As a result, as shown in FIG. 10C, after a pulse signal with a 25% duty ratio is output to the charging switch Q1, a pulse signal with a 75% duty ratio is output to the discharging switch Q2. Is repeated.

  8 includes an error amplifier IC8 having a non-inverting input terminal connected to one end of a resistor r and an inverting input terminal connected to a reference voltage source Vref. The error amplifier IC8 amplifies the difference between the voltage value of the non-inverting input terminal and the voltage value of the inverting input terminal, and outputs the amplified difference toward the base of the switching element Q3 made of a transistor.

  A photocoupler PC is connected to the collector terminal of the switching element Q3, and the difference between the current value of the current flowing through the LED 2 and the voltage value of the reference voltage source Vref is fed back to the control unit 1.

  In the current value detection unit 4 shown in FIG. 8, if the LED 2 is arranged instead of the resistor r, a voltage detection unit that detects the voltage between the terminals of the LED 2 can be configured.

  FIG. 10 is a timing chart for explaining the duty ratio of the charging switch Q1 and the discharging switch Q2.

  The control unit 1 charges a pulse signal having an on / off period of period T as shown in FIG. 10 so that pulses are alternately output to the charging switch Q1 and the discharging switches Q2, Q21 to Q24. Output to the switch Q1 and the discharge switch Q2.

  FIG. 10A shows a waveform of a pulse signal with a time ratio of 50% output to the charging switch Q1, and a waveform of a pulse signal with a time ratio of 50% output to the discharge switch Q2. Is shown.

  When the time ratio of the pulse signal output to the charging switch Q1 and the time ratio of the pulse signal output to the discharging switch Q2 are both 50%, the period T1 during which the pulse is output to the charging switch Q1 is This is the same as the period T2 during which a pulse is output to the discharge switch Q2.

  FIG. 10B shows a waveform of a pulse signal with a time ratio of 75% output to the charging switch Q1, and a waveform of a pulse signal with a time ratio of 25% output to the discharge switch Q2. Is shown.

  When the time ratio of the pulse signal output to the charging switch Q1 is 75% and the time ratio of the pulse signal output to the discharging switch Q2 is 25%, the period during which the pulse is output to the charging switch Q1 T1 is three times the period T2 during which a pulse is output to the discharge switch Q2.

  FIG. 10C shows a waveform of a pulse signal with a time ratio of 25% output to the charging switch Q1, and a waveform of a pulse signal with a time ratio of 75% output to the discharge switch Q2. Is shown.

  When the time ratio of the pulse signal output to the charging switch Q1 is 25% and the time ratio of the pulse signal output to the discharging switch Q2 is 75%, the period during which the pulse is output to the charging switch Q1 T1 is 1/3 times the period T2 during which a pulse is output to the discharge switch Q2.

  Below, the process which controls the time ratio of the pulse signal output to the switch Q1 for charging by the control part 1 and the pulse signal output to the switch Q2 for discharge is demonstrated.

  FIG. 11 is a diagram showing the output characteristics of the switched capacitor device D1 (see FIG. 3). The output characteristics shown in FIG. 11 are obtained by experiments by the present inventors.

  That is, the inventor of the present invention, in the switched capacitor device D1, the voltage value of the DC power source E is 140V, the number of capacitors is one, the number of LEDs 2 is 21, the capacitance of the smoothing capacitor Co is 500 nF, and the inductance of the inductor L is On the condition that the drive frequency of the charge switch and the discharge switch is 1 MHz, the time ratio of the pulse signal output to the charge switch Q1, and the time ratio of the pulse signal output to the discharge switch Q2, An experiment was conducted to measure the current value of the current flowing through the LED 2 while changing.

  From the table shown in FIG. 11, when the time ratio of the pulse signal output to the charging switch Q1 is approximately 30% or less (the time ratio of the pulse signal output to the discharging switch Q2 is approximately 70% or more), It can be seen that the change in the current value of the current flowing through the LED 2 is large with respect to the change in the time ratio of the charging switch Q1 and the discharging switch Q2.

  Further, even when the time ratio of the pulse signal output to the charging switch Q1 is approximately 70% or more (the time ratio of the pulse signal output to the discharging switch Q2 is approximately 30% or less), the charging switch Q1 and the discharging switch It can be seen that the change of the current value of the current flowing through the LED 2 is large with respect to the change of the duty ratio of the switch Q2.

  As a result, in the switched capacitor device D1, in order to energize the LED 2, a pulse with a time ratio in the range of 0% to 30% or in the range of 70% to 100% with respect to the charging switch Q1 and the discharging switch Q2. Output a signal.

  And the time ratio of the pulse signal output to the switch Q1 for charge and the switch Q2 for discharge is controlled within the said range.

  When the current value of the current flowing through the LED 2 that is detected by the current value detection unit 4 fluctuates, the control unit 1 has a time ratio in the range of 0% to 30%, or in the range of 70% to 100%, A pulse signal with a time ratio is outputted to the charging switch Q1 and the discharging switch Q2 so that the current value of the current flowing through the LED 2 becomes the current value before the fluctuation.

  Or the control part 1 monitors the voltage between the terminals of LED2 detected by the voltage detection part 5. FIG.

  When the voltage between the terminals of the LED 2 detected by the voltage detection unit 5 fluctuates, the control unit 1 has a time ratio in the range of 0% to 30%, or in the range of 70% to 100%. A pulse signal having a time ratio such that the inter-voltage becomes the inter-terminal voltage before fluctuation is output to the charging switch Q1 and the discharging switch Q2.

  Thereby, when the current value of the current flowing through the LED 2 fluctuates, the current value can be appropriately controlled to return to the current value before the fluctuation. As a result, DC power can be transmitted to LED 2 in a stable state.

  In the switched capacitor device D1, in addition to the current value detection unit 4 and the voltage detection unit 5, in order to correct the output of the switched capacitor device according to the power supply fluctuation of the DC power source E, the DC A voltmeter that measures the voltage value of power may be arranged between the positive electrode and the negative electrode of the DC power source E.

  In this case, when the voltage value measured by the voltmeter fluctuates, the control unit 1 predicts the fluctuation of the current value of the current flowing through the LED 2 due to the influence of the fluctuation of the voltage value, and changes the fluctuation of the current value. The DC power from the DC power source E is controlled so as to be suppressed. This control is so-called feedforward control.

  Such feedforward control can also transmit DC power to LED 2 in a stable state.

  As described above, since the value of the current flowing through the LED 2 can be changed by changing the time ratio between the charging switch Q1 and the discharging switch Q2, reference examples of the switched capacitor device (FIG. 1A and FIG. A separate current control means such as the switching element Q and the constant current circuit 6 shown in b) can be omitted.

  12 and 13 are diagrams showing the output characteristics of the switched capacitor device when there are a plurality of capacitors. Here, FIG. 12 (a) shows an example of the output characteristics of the switched capacitor device D2 shown in FIG. 4 (a). FIG. 12B shows an example of output characteristics of the switched capacitor device D3 shown in FIG. FIG. 13A shows an example of output characteristics of the switched capacitor device D4 shown in FIG.

  FIG. 13B shows a circuit composed of a capacitor, a charging diode, a discharging diode, and a discharging switch in the switched capacitor device D4 of FIG. 5A. The circuit includes a capacitor C4, a charging diode D14, and a discharging switch. An example of the output characteristics of the circuit further connected in cascade to the circuit composed of the diode D24 and the discharge switch Q24 is shown.

  Here, as shown in FIG. 11, when the number of capacitors is one, when the duty ratio of the charging switch Q1 changes from 80% to 95% at which the current value of the LED current starts to decrease, The degree of decrease in the current value of the LED current when the duty ratio of the switch Q1 increases by 1% is (500-125) (mA) / (95-80) (%) = 25 mA /%.

  On the other hand, in the case of FIG. 12A, when the duty ratio of the charging switch Q1 changes from 75% to 95% where the current value of the LED current starts to decrease, the duty ratio of the charging switch Q1. When the current value increases by 1%, the degree of decrease in the current value of the LED current is (450-90) (mA) / (95-75) (%) = 18 mA /%.

  In the case of FIG. 12B, when the duty ratio of the charging switch Q1 changes from 65% to 95% where the current value of the LED current starts to decrease, the duty ratio of the charging switch Q1 is 1. The degree of decrease in the current value of the LED current when% is increased is (500-50) (mA) / (95-65) (%) = 15 mA /%.

  Further, in the case of FIG. 13A, when the duty ratio of the charging switch Q1 changes from 60% to 90% when the current value of the LED current starts to decrease, the duty ratio of the charging switch Q1 is 1. The degree of decrease in the current value of the LED current when% increases is (480−120) (mA) / (90-60) (%) = 12 mA /%.

  Further, in the case of FIG. 13B, when the duty ratio of the charging switch Q1 changes from 55% to 90% when the current value of the LED current starts to decrease, the duty ratio of the charging switch Q1 is 1. The degree of decrease in the current value of the LED current when% increases is (430-75) (mA) / (90-55) (%) ≈10 mA /%.

  Comparing these results with the case of one capacitor as shown in FIG. 11, when there are a plurality of capacitors, the charging switch has a large time ratio, that is, the discharging switch has a small time ratio. In the region, it can be seen that the slope of the current value of the LED 2 with respect to the change in the duty ratio is gentle, and the current of the LED 2 can be controlled to a sufficiently small value.

  This tendency becomes more prominent as the number of capacitors increases. As a result, the larger the number of capacitors, the wider the control range of the time ratio at which the current value of the LED 2 can be controlled, and thus the control becomes easier.

  Here, the inductor L is disposed in common with the capacitor charging circuit and discharging circuit. If the inductance L of the inductor L and the capacitance C of each capacitor are set so as to satisfy the series resonance condition with respect to the driving frequency of the charging switch and the discharging switch, the charging current and the discharging current are changed to a resonance waveform. As a result, the switching loss of the charging switch and the discharging switch can be reduced.

  That is, due to resonance, the charging and discharging currents vibrate in a sine wave shape, and the charging switch is turned off at the timing when the charging current is reduced to the zero level, and at the timing when the discharging current is reduced to the zero level. When is turned off, switching loss in the charging switch and discharging switch is avoided (zero current switching condition).

  The results shown in FIGS. 12A and 12B and FIGS. 13A and 13B show that the capacitance of each capacitor is 7 nF, the inductance of the inductor L is 800 nH, the charging switch and the discharging switch are driven. The frequency is measured as 1 MHz.

  Here, the duty ratio of the charging switch is controlled within a range of 100 / (1 + n) (%) or more and less than 100%, while the duty ratio of the discharging switch exceeds 0% and is 100 n / (1 + n) ( %) When controlled within the following range, zero current switching can be realized under the condition that the current value flowing through the LED 2 is the largest.

  The reason why the above range is acquired will be described below. First, the charging period T1 and the discharging period T2 when the charging or discharging current vibrates in a sinusoidal shape due to resonance can be expressed as in the equations (1) and (2).

  Here, L represents the inductance of the inductor L, n represents the number of capacitors, and C represents the capacitance of each capacitor.

  And since the discharge period T2 starts when the charge period T1 ends, the charge switch and the discharge switch satisfy the zero current switching condition by turning on the charge switch when the charge period T1 starts, Since the charging switch is turned off when the charging period T1 ends and the discharging period T2 starts, and the charging switch is kept off until the discharging period T2 ends, the time ratio of the charging switch Q1 is When the expression (3) is satisfied.

Ratio of charging switch Q1 = 100 × T1 / (T1 + T2) = 100 / (1 + n) (%) (3)
On the other hand, the duty ratio of the discharge switch Q2 when the duty ratio of the charge switch Q1 satisfies the formula (3) is 100-100 / (1 + n) (%) from the duty ratio of the 100-charge switch Q1.・ (4)

  Thus, while the duty ratio of the charging switch is controlled within a range of 100 / (1 + n) (%) or more and less than 100%, the duty ratio of the discharging switch exceeds 0% and exceeds 100 n / (1 + n) ( %) When controlled within the following range, zero current switching can be realized under the condition that the current value flowing through the LED 2 is the largest.

  As a result, when the charging switch and the discharging switch are controlled within the above range of the time ratio, the value of the current flowing through the LED 2 can be kept large while suppressing the switching loss in the charging switch and the discharging switch.

  FIG. 14 shows a switched capacitor device D4 having four capacitors as shown in FIG. 5A, in which the driving frequency of the charging switch and the discharging switch is changed under different conditions of the voltage value of the DC power source E. It is the figure which showed an example of the output characteristic in a case.

  According to FIG. 14, when the voltage value of the DC power source E is 160V, the correlation between the driving frequency of the charging switch and the discharging switch and the LED current is indicated by a circle. Further, when the voltage value of the DC power source E is 150 V, the correlation between the driving frequency of the charging switch and the discharging switch and the LED current is represented by a triangle.

  Furthermore, the correlation between the driving frequency of the charging switch and the discharging switch and the LED current when the voltage value of the DC power source E is 140 V is represented by rhombuses. Furthermore, when the voltage value of the DC power source E is 130 V, the correlation between the drive frequency of the charging switch and the discharging switch and the LED current is represented by x.

  From FIG. 14, it can be seen that the value of the LED current increases as the voltage value of the DC power from the DC power source E increases regardless of the driving frequency of the charging switch and the discharging switch. It can be seen that the value of the LED current decreases as the driving frequency of the charging switch and discharging switch decreases, regardless of the DC power voltage value. Note that the result of FIG. 14 shows the result when the duty ratio of the charging switch and the discharging switch is 50%.

  From the result of FIG. 14, it can be seen that when the voltage value of the DC power from the DC power source E changes, the LED current value can be kept constant by changing the drive frequency of the charging switch and the discharging switch.

  For example, when the control unit 1 controls the current value flowing through the LED 2 to be maintained at 600 mA, when the voltage value of the DC power source E is 160 V, the control unit 1 sets the charging switch and the discharging switch at a driving frequency of about 380 kHz. Drive.

  Then, it is assumed that the voltage value of the DC power source E has changed from 160V to 130V. When the voltage value of the DC power source E is 130 V, the driving frequency of the charging switch and the discharging switch necessary for maintaining the current value of the LED 2 at 600 mA is approximately 730 KhZ as can be seen from FIG. It is.

  Therefore, when the voltage value of the DC power source E fluctuates from 160 V to 130 V when the current value flowing through the LED 2 is maintained at 600 mA, the control unit 1 changes the drive frequency of the charging switch and the discharging switch by Δf. In other words, the charging switch and the discharging switch are driven at the driving frequency after the change from about 380 kHz to about 730 kHz.

  Thereby, it is possible to control the value of the current flowing through the LED 2 without using the current control means for controlling the separate LED 2 as shown in FIGS.

(Second Embodiment)
Next, a switched capacitor device according to a second embodiment of the present invention will be described with reference to FIGS. 6 and 15 to 19. Note that the switched capacitor device according to the second embodiment is that the control unit 1 performs control to turn on a part of the discharge switches while the charging switch is on. Different from the device.

  Since other configurations are the same as those of the switched capacitor device according to the first embodiment, the description and illustration thereof are omitted. Hereinafter, characteristic points of the present embodiment will be described.

  Here, as already described with reference to FIG. 6, there are a number of LEDs 2 that can suitably emit light depending on the voltage value Vin of the DC power source E and the number of capacitors. In FIG. The maximum number of series is shown. The switched capacitor device according to the second embodiment focuses on this point.

  FIG. 15 is a diagram illustrating an example of a circuit configuration of the switched capacitor device according to the second embodiment. FIG. 16 is a diagram illustrating another example of the circuit configuration of the switched capacitor device according to the second embodiment. FIG. 17 is a diagram illustrating a waveform of a pulse signal output from the control unit 1 in the second embodiment.

  A switched capacitor device D6 shown in FIG. 15 further includes a circuit including a capacitor C5, a charging diode D15, a discharging diode D25, and a discharging switch Q25 in the switched capacitor device D4 (see FIG. 5A). It is a thing.

  A switched capacitor device D7 shown in FIG. 16 includes a circuit composed of a capacitor C5, a charging diode D15, a discharging diode D25, and a discharging switch Q25 in the switched capacitor device D5 (see FIG. 5B). In addition.

  In the switched capacitor devices D6 and D7 shown in FIGS. 15 and 16, the control unit 1 outputs a pulse signal having a waveform shown in FIG. 17 to the charging switch Q1 and the discharging switches Q21 to Q25.

  In principle, the control unit 1 outputs a pulse signal having an on / off cycle T so that pulses alternately arrive at the charging switch Q1 and the discharging switches Q21 to Q25 (period A).

  However, when the current value of the current flowing through the LED 2 fluctuates, the control unit 1 outputs a pulse signal shown in one of the periods B to D in order to return the current value to the current value before the fluctuation. In the period B, the control unit 1 causes the charging switch Q1 and the discharging switch to output a pulse to the discharging switch Q25 at a rate of once every two times the pulse is output to the charging switch Q1. A pulse signal is output to switches Q21 to Q25.

  In the period B, the capacitor C5 of the discharging circuit in which the discharging switch Q25 is arranged is short-circuited at a rate of once every two times when the pulse is output to the charging switch Q1. For this reason, the number of capacitors that can be charged is reduced by one at a rate of two times that each capacitor is charged.

  Thereby, the voltage between the terminals of the chargeable capacitor can be increased at a rate of once every two times when each capacitor is charged. As a result, the amount of electric energy transmitted to the LED 2 can be increased by increasing the current value of the current flowing through the LED 2 by discharging each capacitor.

  In the period C, the control unit 1 controls the charging switch Q1 and the discharging switch so that the pulse is output to the discharging switch Q25 at a rate of four times every five times the pulse is output to the charging switch Q1. A pulse signal is output to switches Q21 to Q25.

  In the period C, the terminal voltage of the chargeable capacitor can be increased at a rate of 4 times in 5 times each capacitor is charged. As a result, since the current value of the current flowing through the LED 2 can be increased more than the increase in the period B due to the discharge of each capacitor, the amount of electrical energy transmitted to the LED 2 is increased more than the increase in the period B. be able to.

  In the period D, the control unit 1 outputs a pulse signal to the discharging switch Q25 so that a pulse is continuously output to the discharging switch Q25, and outputs a pulse to the charging switch Q1. Pulse signals are output to the charging switch Q1 and the discharging switches Q21 to Q24 so that a pulse is output to the discharging switch Q24 at a rate of once every two times.

  In the period D, while the pulse is output to the charging switch Q1, not only the discharging switch Q25 but also the discharging switch Q24 outputs a pulse. Therefore, charging can be performed by the amount of the discharging switch Q24. The number of capacitors is further reduced.

  As a result, the voltage across the terminals of the chargeable capacitor is further greater than that of period C. As a result, since the current value of the current flowing through the LED 2 can be increased more than the increase in the period C due to the discharge of each capacitor, the amount of electrical energy transmitted to the LED 2 is increased more than the increase in the period C. be able to.

  FIG. 18 is a diagram illustrating an example of a configuration of the control unit 1 in the second embodiment. The control unit 1 shown in FIG. 18 amplifies the signals from the current value detection unit 4 and the voltage detection unit 5 by the error amplifier Amp, converts the signal into a digital signal form by the A / D converter 11, and then the microcomputer. 12 is output.

  The microcomputer 12 is driven based on the clock signal generated by the oscillator OSC, and is output from each of the charging switch Q1 and the discharging switches Q21 to Q25 according to the signal input from the A / D converter 11. A pulse signal to be generated is generated.

  When the microcomputer 12 generates each pulse signal, the microcomputer 12 outputs the generated pulse signal to the charging switch Q1 and the discharging switches Q21 to Q25 through the buffer IC 13.

  FIG. 19 is a diagram illustrating another example of the configuration of the control unit 1 in the second embodiment. The control unit 1 shown in FIG. 19 converts a control signal output in the form of an AC signal from a dimmer or the like into a DC signal form using the AC / DC converter 15 and converts it into a digital signal form using the A / D converter 11. After conversion, the data is output to the microcomputer 12.

  The microcomputer 12 is driven based on the clock signal generated by the oscillator OSC, and is output from each of the charging switch Q1 and the discharging switches Q21 to Q25 according to the signal input from the A / D converter 11. A pulse signal to be generated is generated.

  When the microcomputer 12 generates each pulse signal, the microcomputer 12 outputs the generated pulse signal to the charging switch Q1 and the discharging switches Q21 to Q25 through the buffer IC 13.

  In the second embodiment, the time ratio of the pulse signals output to the charging switch Q1 and the discharging switch Q2 may be controlled as in the first embodiment. In this way, the current value flowing through the LED 2 can be controlled more appropriately.

D, D1 to D7 Switched capacitor device 1 Control unit 2 LED
E DC power source C, C1, C2, C3, C4, C5 Capacitors D1, D11, D12, D13, D14, D15 Charging diode D2, D21, D22, D23, D24, D25 Discharging diode Q1 Charging switch Q2, Q21, Q22, Q23, Q24, Q25 Discharge switch

Claims (10)

A switched capacitor device for driving a load,
A DC power source that outputs DC power;
A capacitor for receiving and charging and discharging the DC power;
A charging switch for controlling the charging of the capacitor by an on / off operation;
A discharge switch for controlling the discharge in the capacitor by an on / off operation;
Charging control for turning on the charging switch and turning off the discharging switch to charge the capacitor; and discharging control for turning off the charging switch and turning on the discharging switch to discharge the capacitor. A control unit that executes alternately;
With
Between the positive electrode and the negative electrode of the DC power source, the charging switch, the capacitor, and the load are connected in series to form a charging circuit for charging the capacitor,
A discharge circuit for discharging the capacitor is formed between the one end and the other end of the capacitor by connecting the discharge switch and the load in series.
The controller is
The switched capacitor device, wherein a current ratio of a current flowing through the load is controlled by discharging the capacitor by controlling a time ratio between the charging switch and the discharging switch. A plurality of the discharge switches are disposed;
Between the positive electrode and the negative electrode of the DC power source, a plurality of the capacitors are further connected in series,
The discharge circuit and the load are connected in series between one end and the other end of each capacitor to form a plurality of the discharge circuits. Switched capacitor device. A plurality of charging diodes arranged in series adjacent to the load side in each capacitor and connected so that the charging current of each capacitor is in the forward direction are arranged,
Each discharge switch is connected in parallel with each capacitor and a charging diode adjacent to the load side of each capacitor,
Between the terminal of the load opposite to the charging diode and a connection point between the capacitors and the charging diodes, there is a discharging diode oriented in the forward direction in the discharging direction of the capacitors. Each connected,
When the discharge control is executed, each capacitor discharges through a plurality of discharge circuits including one or more of the plurality of discharge switches, the load, and the discharge diodes. The switched capacitor device according to claim 1. A plurality of charging diodes arranged in series adjacent to the load side in each capacitor and connected so that the charging current of each capacitor is in the forward direction are arranged,
When the number of combinations of the capacitors and the charging diodes adjacent to the load side of the capacitors is n (where n is a positive integer), the most load-side combination and the most load-side combination Each of the discharge switches is connected in parallel to each of n-1 combinations from the combination to the i-th (where i is an integer of 2 to n) combination,
Between the terminal of the load opposite to the charging diode and the connection point between the capacitors and the charging diodes, the discharging diode is oriented in the forward direction in the discharging direction of the capacitors. Are connected to each other,
2. The capacitor according to claim 1, wherein when the discharge control is executed, the capacitors discharge through a plurality of discharge circuits including the discharge switches, the load, and the discharge diodes. Switched capacitor device. An inductor disposed in common with the charging circuit and the discharging circuit;
The controller is
While the duty ratio of the charging switch is controlled within a range of 100 / (1 + n) (%) or more and less than 100%, the duty ratio of the discharging switch is more than 0% and 100 n / (1 + n) (% The switched capacitor device according to claim 3, wherein the switched capacitor device is controlled within the following range. A switched capacitor device for driving a load,
A DC power source that outputs DC power;
A plurality of capacitors that receive and charge and discharge the DC power;
A charging switch for controlling on-off operation and charging in each capacitor;
A plurality of discharge switches for on-off operation to control discharge in each capacitor;
The charging control for turning on the charging switch and turning off the discharging switch to charge the capacitors, and turning off the charging switch and turning on the discharging switches to discharge the capacitors. A control unit that alternately performs discharge control;
With
Between the positive electrode and the negative electrode of the DC power source, the charging switch, the capacitors, and the load are connected in series, thereby forming a charging circuit for charging the capacitor.
For each capacitor, a discharge circuit for discharging the capacitor is formed by connecting each discharge switch and the load in series between one end and the other end of the capacitor,
An inductor is arranged in common for the charging circuit and each discharging circuit,
The controller is
The switched capacitor device, wherein a driving frequency of the charging switch and each discharging switch is controlled to control a current value of a current flowing through the load by discharging the capacitor. In the control unit, when the voltage value of the DC power by the DC power source changes, the voltage value is each of a plurality of voltage values obtained in the process of changing the voltage value, When changing the drive frequency of the charging switch and each discharging switch, the current value of the current flowing through the load at the time of discharging each capacitor is preset,
The controller is
When the voltage value of the DC power of the DC power source changes, and the current value of the current flowing through the load changes when the capacitors are discharged, the voltage value of the DC power changes after the change. A driving frequency of the charging switch and each discharging switch that obtains a current value before change as a current value of a current flowing through the load under a condition of a voltage value is obtained, and the charging switch at the driving frequency The switched capacitor device according to claim 6, wherein the discharge switches are driven. A switched capacitor device for driving a load,
A DC power source that outputs DC power;
A plurality of capacitors that receive and charge and discharge the DC power;
A charging switch for controlling the charging of the capacitor by an on / off operation;
A plurality of discharge switches for on-off operation to control discharge in the capacitor;
The charging control for turning on the charging switch and turning off the discharging switch to charge the capacitors, and turning off the charging switch and turning on the discharging switches to discharge the capacitors. A control unit that alternately performs discharge control;
With
A first series circuit in which the capacitors are connected in series with the charging switch and the load is connected between a positive electrode and a negative electrode of the DC power source as a charging circuit for charging the capacitors. ,
A plurality of discharge circuits for discharging each capacitor is formed between one end and the other end of each capacitor so that a series circuit of each discharge switch and the load is connected to each other. ,
In each discharge circuit, each discharge switch is connected in parallel to one end and the other end of each capacitor,
The controller is
While the charging switch is turned on, one or a plurality of discharging switches among the discharging switches are turned on to control the current value of the current flowing through the load by discharging the capacitor. A switched capacitor device. The controller is
9. The switched capacitor device according to claim 8, further controlling a time ratio between the charging switch and each discharging switch to control a current value of a current flowing through the load by discharging each capacitor. .   The switched capacitor device according to any one of claims 1 to 9, wherein the load is a solid-state light emitting element.