JP2014161160A - Charging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging device in which a battery can be charged up to high voltage by connecting a plurality of power supplies in series and a battery having low charging voltage can be charged while suppressing reduction in power supply efficiency.SOLUTION: With mutual outputs being connected in series, a power supply PS and a DCDC converter CNV are connected to a storage battery unit 50. When a constant current value at voltage dropping in an overcurrent protection characteristics of the DCDC converter CNV is specified to be lower than a constant current value at voltage dropping in an overcurrent protection characteristics of the power supply PS, and a voltage value of a DC voltage Vdc1 of the power supply PS reach a threshold value specified to be near a maximum output voltage value with respect to the DC voltage Vdc1, the DCDC converter CNV moves to an operating state and supplies charging current Idc to the storage battery unit 50 at the constant current value.

Description

  The present invention relates to a charging device configured by connecting a DCDC converter in series to a power supply device that outputs a DC voltage.

  As a charging device configured by connecting a plurality of power supply devices in series, a charging device disclosed in Patent Document 1 below is known. This charging device is equipped with a plurality of DC power supply devices of the same specification, and by connecting the outputs of as many DC power supply devices as necessary in series, the DC voltage output from each DC power supply device is added and required. It is configured to obtain a high voltage. In this charging device, the DC power supply devices start operating simultaneously, and charge the assembled battery composed of a plurality of secondary batteries. Further, in this charging apparatus, constant current charging is performed on the assembled battery while detecting the charging current flowing in the assembled battery and the charging voltage of the assembled battery, and the detected charging voltage reaches a preset charging end voltage. At that point, the charging operation is terminated. Therefore, according to this charging device, it is possible to pursue the mass production effect of the DC power supply device, thereby making it possible to configure the device at low cost.

  In addition, according to this charging device, a DC voltage is not generated from the DC power supply device over the entire voltage range that can be generated (for example, 0 to 90 volts), but a low voltage range in which a reduction in power supply efficiency is greatly increased. By generating a DC voltage within a relatively narrow range (for example, 60 to 90 volts) while avoiding it, it is possible to increase the power efficiency of each DC power supply device.

JP 2000-166114 A (page 2-7, FIG. 1-2)

  However, the above charging apparatus has the following problems to be improved. That is, in order to increase the power supply efficiency in the above charging device, a configuration is adopted in which the voltage range of the DC voltage generated in each DC power supply device is limited to the above narrow range. However, there is a problem that a battery having a low charging voltage cannot be charged.

  The present invention has been made in order to solve such a problem, and allows a battery to be charged to a high voltage by connecting a plurality of power supply devices in series, and a battery having a low charging voltage while reducing a decrease in power supply efficiency. It is a main object to provide a charging device that can be charged.

  In order to achieve the above object, a charging device according to the present invention has a constant current voltage drooping type overcurrent protection characteristic and outputs a DC voltage between a positive output terminal and a negative output terminal; An input terminal is connected to the positive output terminal of the power supply apparatus and a negative input terminal is connected to the negative output terminal of the power supply apparatus to operate the DC voltage from the power supply apparatus as an operating voltage, and to output a positive output. A DCDC converter that outputs a DC voltage between the terminal and the negative output terminal and has a constant current voltage drooping type overcurrent protection characteristic, and the power supply device and the DCDC converter include the positive output terminal of the power supply device. And the negative output terminal of the DCDC converter are connected in series with each other, and the positive output terminal of the DCDC converter and the negative output of the power supply device The DCDC converter has a constant current value at the time of voltage droop in the overcurrent protection characteristic of the DCDC converter, a constant current at the time of voltage droop in the overcurrent protection characteristic of the power supply device. The voltage value of the DC voltage of the power supply device is specified in advance as either the maximum output voltage value for the DC voltage of the power supply device or a voltage value in the vicinity of the maximum output voltage value. When the threshold voltage is reached, the operation state is shifted to, and the charging current is supplied to the charging target at the constant current value of the DCDC converter.

  According to the charging device of the present invention, for a low voltage charge target whose DC voltage of the power supply device is less than the threshold voltage, only the power supply device is used until the DC voltage of the power supply device (charge voltage of the charge target) reaches the threshold voltage. After the battery is efficiently charged and the DC voltage of the power supply device reaches the threshold voltage (when the charging voltage is in a state that is somewhat high), the power supply device and the DCDC converter are charged with a higher charge voltage (maximum output voltage value of the power supply device). And the total output voltage value of the DCDC converter). Therefore, according to this charging device, it is possible to charge a charging target having a low charging voltage and a charging target having a high charging voltage while maintaining the power supply efficiency of the entire charging device sufficiently high.

It is a block diagram of charging device CH provided with power supply device PS and DCDC converter CNV. FIG. 4 is an output characteristic diagram A1 showing characteristics of the direct current voltage Vdc1 with respect to the direct current Idc1 of the power supply device PS, and an output characteristic diagram A2 showing characteristics of the direct current voltage Vdc2 with respect to the direct current Idc2 of the DCDC converter CNV. It is an output characteristic figure which shows the characteristic of the charging voltage Vb with respect to the charging current Idc of charging device CH.

  Hereinafter, embodiments of the charging device CH will be described with reference to the drawings.

  First, the configuration of the charging device CH in FIG. 1 will be described. The charging device CH includes one power supply device PS, one DCDC converter CNV which is an example of another power supply device, a backflow preventing rectifier element D1 and a bypass rectifier element D2, and is a storage battery as a battery to be charged. A DC voltage (DC voltage Vdc1 described later or DC voltage (Vdc1 + Vdc2)) is output to the unit 50 and charged to a predetermined charging voltage value (total voltage value of reference voltage values Vref1 and Vref2 described later). The storage battery unit 50 is configured by connecting a plurality of storage batteries in series as an example.

  As an example, the power supply device PS includes a positive input terminal 2, a negative input terminal 3, a rectifying and smoothing circuit 4, a switching circuit 5, a transformer 6, a rectifying circuit 7, a smoothing circuit 8, a control circuit 9, a positive output terminal 10, and a negative output terminal. 11 for converting an external input voltage input between the positive input terminal 2 and the negative input terminal 3 (in this example, an AC voltage Vac, but may be a DC voltage) into a DC voltage Vdc1 for output. It is configured as a type converter (insulated ACDC converter in this example).

  In addition, as shown in the output characteristic diagram A1 shown in FIG. 2, the power supply device PS has a voltage value of the output DC voltage Vdc1 (in this example, this voltage value is also expressed as “voltage value Vdc1”). Is limited by the reference voltage value Vref1, and the current value of the DC current Idc1 to be output (in this example, this current value is also expressed as “current value Idc1”) is limited by the reference current value Iref1. It has a constant current voltage drooping type overcurrent protection characteristic. As long as the power supply device PS is an insulating converter, the power supply device PS can be configured by various insulating converters such as a forward method, a flyback method, a bridge method, and a push-pull method.

  The rectifying / smoothing circuit 4 rectifies and smoothes the AC voltage Vac to convert it into a DC voltage and output it. When a DC voltage is input as an external input voltage instead of the AC voltage Vac, a configuration using a smoothing circuit instead of the rectifying / smoothing circuit 4 can be adopted, and a ripple of the input DC voltage can be used. In the case where the number of the rectifying and smoothing circuits 4 is small, a configuration in which the rectifying and smoothing circuit 4 is omitted may be employed.

  The switching circuit 5 has a switch element (transistor, etc.) (not shown), and this switch element is controlled by the control circuit 9 to repeatedly turn on and off, thereby switching the DC voltage output from the rectifying and smoothing circuit 4. And intermittently applied to the transformer 6. As an example, the transformer 6 includes a primary winding 6a and a secondary winding 6b that are electrically insulated from each other. Further, the transformer 6 induces an AC voltage in the secondary winding 6 b due to intermittent application of the DC voltage to the primary winding 6 a by the switching circuit 5.

  The rectifier circuit 7 rectifies the alternating voltage induced in the secondary winding 6b, thereby converting it into a pulsating voltage and outputting it. The smoothing circuit 8 constitutes a rectifying / smoothing circuit in combination with the rectifying circuit 7, converts the pulsating voltage output from the rectifying circuit 7 into a DC voltage Vdc1, and converts it into a positive output unit 8a and a negative output. Output from between the unit 8b. The smoothing circuit 8 includes a voltage detection unit and a current detection unit (not shown). For example, the voltage detection unit is configured by a voltage dividing resistor circuit, detects the DC voltage Vdc1, and generates a voltage detection signal Sv whose voltage value changes in accordance with the voltage value of the DC voltage Vdc1 to the control circuit 9. Output. Further, the current detection unit is configured by a detection resistor having a minute resistance value of, for example, less than 1Ω, detects the DC current Idc1 output from the positive output unit 8a and the negative output unit 8b, and the current value Idc1 of the DC current Idc1. A current detection signal Si whose voltage value changes in response to the signal is generated and output to the control circuit 9.

  The control circuit 9 executes switching control for the switch elements of the switching circuit 5. In this switching control, the control circuit 9 calculates the current voltage value of the direct current voltage Vdc1 based on the voltage detection signal Sv, and calculates the current value Idc1 of the current direct current Idc1 based on the current detection signal Si. Further, the control circuit 9 determines that the DC voltage Vdc1 and the DC current Idc1 satisfy the output characteristic diagram A1 shown in FIG. 2 based on the calculated voltage value Vdc1 of the current DC voltage Vdc1 and the current value Idc1 of the current DC current Idc1. Thus, the switch element of the switching circuit 5 is controlled.

  Specifically, the control circuit 9 performs duty ratio control (or frequency control) on the switch element of the switching circuit 5, so that the current value Idc1 of the output DC current Idc1 is the reference current value (maximum output current value). ) When it is less than Iref1, a constant voltage control operation is performed in which the voltage value of the DC voltage Vdc1 is controlled to a constant reference voltage value (maximum output voltage value) Vref1, and the current value Idc1 of the DC current Idc1 is the reference current value. In the state of reaching Iref1, a constant current control operation for changing the voltage value Vdc1 of the DC voltage Vdc1 is executed while maintaining (limiting) the current value Idc1 of the DC current Idc1 at a constant reference current value Iref1.

  For example, the DCDC converter CNV includes a positive input terminal 22, a negative input terminal 23, an input voltage detection circuit 24, a switching circuit 25, a transformer 26, a rectifier circuit 27, a smoothing circuit 28, a control circuit 29, a positive output terminal 30, and a negative output. A positive input terminal 22 connected to the positive output terminal 10 of the power supply device PS via a connection line and a negative input terminal 23 connected to the negative output terminal 11 of the power supply device PS via a connection line. An external DC input voltage (in this example, a DC voltage Vdc1 output from the power supply device PS) operates as an operating voltage, and is configured as an isolated DCDC converter that converts the DC voltage Vdc1 into a DC voltage Vdc2 and outputs it. Has been.

  Further, as shown in the output characteristic diagram A2 shown in FIG. 2, the DCDC converter CNV has a voltage value of the output DC voltage Vdc2 (in this example, this voltage value is also expressed as “voltage value Vdc2”). ) Is limited by the reference voltage value Vref2, and the current value of the DC current Idc2 to be output (in this example, this current value is also referred to as “current value Idc2”) is the reference current value Iref2 (<Iref1) It has a constant current voltage drooping type overcurrent protection characteristic limited by As long as the DCDC converter CNV is an isolated converter, the DCDC converter CNV can be composed of various isolated converters such as a forward method, a flyback method, a bridge method, and a push-pull method.

  In this case, the reference current value Iref2 is defined to be lower than the reference current value Iref1, but the reference voltage value Vref2 is specified to be a voltage value lower than the reference voltage value Vref1 as shown in FIG. Alternatively, unlike the state of FIG. 2, the voltage value may be specified to be equal to or higher than the reference voltage value Vref1.

  However, in this charging device CH, the power supply device PS supplies all of the power when charging the storage battery unit 50, including the power supplied to the DCDC converter CNV. For this reason, the maximum value (maximum power value) of the power that the charging device CH supplies to the storage battery unit 50 when charging the storage battery unit 50 is smaller than the maximum value (maximum power value) of the power that can be output by the power supply device PS. Become.

  In this case, the maximum power value for the charging device CH is DCDC when the power supply device PS maintains the voltage value Vdc1 of the DC voltage Vdc1 at the reference voltage value Vref1 as described later (constant voltage operation state). The converter CNV regulates the voltage value Vdc2 of the DC voltage Vdc2 to the reference voltage value Vref2 from the state where the storage battery unit 50 is charged (constant current operation state) by regulating the current value Idc2 of the DC current Idc2 to the reference current value Iref2. Thus, the power value ((Vref1 + Vref2) × Iref2) at the time when the storage battery unit 50 is shifted to the state of charging (constant voltage operation state) is obtained. Therefore, in this charging device CH, the reference voltage value Vref2 and the reference current value Iref2 are defined in advance such that the power value ((Vref1 + Vref2) × Iref2) is less than the maximum power value (Vref1 × Iref1) of the power supply device PS. ing.

  The input voltage detection circuit 24 includes, for example, a voltage dividing resistor circuit (not shown), a reference power supply, and a comparator, and the voltage dividing resistor circuit is input to the external input between the positive input terminal 22 and the negative input terminal 23. The voltage (DC voltage Vdc1 in this example) is divided, and the comparator compares the divided voltage with a reference voltage output from a reference power supply (for example, a Zener diode), whereby a voltage value Vdc1 of the DC voltage Vdc1 is obtained. The operation signal S1 is output when the voltage is equal to or higher than a predetermined threshold voltage Vth.

  In this case, the threshold voltage Vth is the maximum output voltage value (in this example, the reference voltage value Vref1) for the DC voltage Vdc1 of the power supply apparatus PS and a voltage value substantially equal to the maximum output voltage value (for example, less than the reference voltage value Vref1). And an arbitrary voltage value of 90% or more of the reference voltage value Vref1 (in other words, a voltage value slightly lower than the maximum output voltage value). In this example, as an example, the threshold voltage Vth is regulated to a voltage value substantially equal to the reference voltage value Vref1, as shown in FIG.

  The switching circuit 25 has a switch element (transistor or the like) (not shown), and is input between the positive input terminal 22 and the negative input terminal 23 when the switch element is controlled by the control circuit 29 and repeatedly turned on and off. The external input voltage (DC voltage Vdc1 in this example) is switched and applied to the transformer 26 intermittently. As an example, the transformer 26 includes a primary winding 26a and a secondary winding 26b that are electrically insulated from each other. Further, the transformer 26 induces an AC voltage in the secondary winding 26 b due to intermittent application of the DC voltage to the primary winding 26 a by the switching circuit 25.

  The rectifier circuit 27 rectifies the AC voltage induced in the secondary winding 26b, thereby converting it into a pulsating voltage and outputting it. The smoothing circuit 28 forms a rectifying / smoothing circuit in combination with the rectifying circuit 27, and smoothes the pulsating voltage output from the rectifying circuit 27 to convert it into a DC voltage Vdc2, thereby producing a positive output unit 28a and a negative output. Output from between the unit 28b. The smoothing circuit 28 includes a voltage detection unit and a current detection unit (not shown). For example, the voltage detection unit is configured by a voltage dividing resistor circuit, detects the DC voltage Vdc2, and generates a voltage detection signal Scv whose voltage value changes according to the voltage value of the DC voltage Vdc2 to the control circuit 29. Output. In addition, the current detection unit is configured by a detection resistor having a minute resistance value of, for example, less than 1Ω, detects the direct current Idc2 output from the positive output unit 28a and the negative output unit 28b, and the current value Idc2 of the direct current Idc2. A current detection signal Sci whose voltage value changes according to the signal is generated and output to the control circuit 29.

  The control circuit 29 executes switching control for the switch element of the switching circuit 25 when the operation signal S1 is output from the input voltage detection circuit 24, and performs switching control for the switch element when the operation signal S1 is not output. Stop running. In this switching control, the control circuit 29 calculates the current voltage value Vdc2 of the current DC voltage Vdc2 based on the voltage detection signal Scv, and calculates the current value Idc2 of the current DC current Idc2 based on the current detection signal Sci. . Further, based on the calculated voltage value Vdc2 of the current DC voltage Vdc2 and current value Idc2 of the current DC current Idc2, the control circuit 29 satisfies the output characteristic diagram A2 shown in FIG. 2 based on the DC voltage Vdc2 and the DC current Idc2. Thus, the switch element of the switching circuit 25 is controlled.

  Specifically, the control circuit 29 performs duty ratio control (or frequency control) on the switch element of the switching circuit 25, whereby the current value Idc2 of the output DC current Idc2 is the reference current value (maximum output current value). ) When it is less than Iref2, a constant voltage control operation is performed in which the voltage value of the DC voltage Vdc2 is controlled to the reference voltage value (maximum output voltage value) Vref2, and the current value Idc2 of the DC current Idc2 becomes the reference current value Iref2. In the reached state, the constant current control operation for changing the voltage value Vdc2 of the DC voltage Vdc2 is executed while maintaining (limiting) the current value Idc2 of the DC current Idc2 to the reference current value Iref2.

  The backflow preventing rectifying element D1 is formed of a diode as an example, and, as shown in FIG. 1, between the positive output portion 28a of the smoothing circuit 28 and the positive electrode of the storage battery unit 50 described later, the positive electrode of the storage battery unit 50. The direction toward is the forward direction. In this example, as an example, the rectifying element D1 is externally connected to the DCDC converter CNV, so the rectifying element D1 is connected between the positive output terminal 30 of the DCDC converter CNV and the positive electrode of the storage battery unit 50 via a connection line. However, in the configuration in which the DCDC converter CNV includes the rectifying element D1, the rectifying element D1 is connected between the positive output unit 28a of the smoothing circuit 28 and the positive output terminal 30 of the DCDC converter CNV. In the case where the smoothing circuit 28 has a function of blocking the inflow of current from the positive output portion 28a, the rectifying element D1 can be omitted.

  The bypass rectifying element D2 is constituted by a diode as an example, and as shown in FIG. 1, the negative output terminal 31 of the DCDC converter CNV and the positive electrode of the storage battery unit 50 (the positive electrode and the cathode of the diode constituting the rectifying element D1). And a direction toward the positive electrode of the storage battery unit 50 as a forward direction. As described above, in the configuration in which the rectifying element D1 for preventing backflow is built in the DCDC converter CNV, the rectifying element D2 for bypassing is also provided between the positive output terminal 30 and the negative output terminal 31 of the DCDC converter CNV. A configuration in which the DCDC converter CNV is built in a state in which the direction toward the positive output terminal 30 is connected as the forward direction may be employed.

  In the charging device CH configured as described above, the positive output terminal 10 of the power supply device PS and the positive input terminal 22 of the DCDC converter CNV, and the negative output terminal 11 of the power supply device PS and the negative input terminal 23 of the DCDC converter CNV are provided. Are connected by connection lines. Further, the positive output terminal 10 of the power supply device PS and the negative output terminal 31 of the DCDC converter CNV are connected by a connection line, so that the power supply device PS and the DCDC converter CNV are connected in series (the power supply device PS and the DCDC converter CNV Are connected in series with each other).

  Further, the positive output terminal 10 of the power supply device PS and the negative output terminal 31 of the DCDC converter CNV are connected to the anode terminal of the diode constituting the rectifying element D2, and the anode terminal of the diode constituting the rectifying element D1 is The positive output terminal 30 of the DCDC converter CNV is connected. Further, the connection point of each rectifying element D1, D2 (the cathode terminal of each diode constituting each rectifying element D1, D2) is connected to the positive electrode of the battery to be charged (storage battery unit 50) via a connection line, By connecting the negative output terminal 11 of the power supply device PS and the negative electrode of the storage battery unit 50 with a connection line, the storage battery unit 50 is connected between the positive output terminal 30 of the DCDC converter CNV and the negative output terminal 11 of the power supply device PS. It is connected.

  Therefore, in the charging device CH, the DC voltages Vdc1 and Vdc2 of the power supply device PS and the DCDC converter CNV are added and output to the storage battery unit 50. The storage battery unit 50 is connected to the DC current Idc (hereinafter referred to as the DC current Idc) (Also referred to as “charging current Idc”), the battery is charged to the total voltage value of the reference voltage values Vref1 and Vref2.

  Next, the operation of the charging device CH will be described. In the following, in order to facilitate understanding of the invention, it is assumed that each rectifying element D1, D2 is an ideal rectifying element and has a voltage drop of zero volts.

  In charging device CH, first, power supply device PS starts outputting DC voltage Vdc1. Specifically, when the charging voltage Vb of the storage battery unit 50 at the beginning of charging is lower than the reference voltage value Vref1 (more specifically, lower than the threshold voltage Vth), in the power supply device PS, the control circuit 9 Initially, control is performed to increase the duty ratio of the switching element in the switching circuit 5 so that the voltage value Vdc1 of the DC voltage Vdc1 is defined as the reference voltage value Vref1, but the voltage value Vdc1 of the DC voltage Vdc1 is It is defined by the charging voltage Vb.

  In this case, in the DCDC converter CNV, the input voltage detection circuit 24 stops the output of the operation signal S1 because the voltage value Vdc1 of the detected DC voltage Vdc1 is lower than the threshold voltage Vth. Thereby, since the control circuit 29 does not execute the on / off control for the switching elements of the switching circuit 25, the DCDC converter CNV is maintained in a stopped state (a state where the output of the DC voltage Vdc2 is stopped). Therefore, in charging device CH, only power supply device PS operates and outputs DC current Idc1 at DC voltage Vdc1. At this time, the direct current Idc1 output from the power supply device PS is output to the storage battery unit 50 via the bypass rectifying element D2.

  At this time, the direct current Idc1 is supplied to the storage battery unit 50 as the charging current Idc. Further, until the voltage value of the charging voltage Vb of the storage battery unit 50 reaches a predetermined charging voltage value (total voltage value of each reference voltage value Vref1, Vref2), the charging current Idc flows into the storage battery unit 50 with a large current value. . For this reason, in the power supply device PS, the control circuit 9 controls the duty ratio with respect to the switch element of the switching circuit 5 and uses this current value Idc1 (in this case, the current value of the charging current Idc) as the reference current value. The operation of maintaining the current at Iref1 is executed (the constant current voltage drooping type overcurrent protection function is activated).

  As a result, the charging device CH (in this case, the power supply device PS), as shown in FIG. 3, the charging of the storage battery unit 50 proceeds and the charging voltage Vb (in this case, the DC voltage Vdc1) becomes the reference voltage value Vref1. Until the current value of the charging current Idc is maintained at the reference current value Iref1, the constant current charging that is output to the storage battery unit 50 is executed.

  Thereafter, when charging of the storage battery unit 50 proceeds and the charging voltage Vb (in this case, the DC voltage Vdc1) reaches the threshold voltage Vth, in the DCDC converter CNV, the input voltage detection circuit 24 starts outputting the operation signal S1. . As a result, in the DCDC converter CNV, the control circuit 29 starts execution of the on / off control for the switch elements of the switching circuit 25, and thus the DCDC converter CNV starts outputting the DC voltage Vdc2.

  Therefore, in this state, the storage battery unit 50 is supplied with the DC voltage Vdc2 output from the DCDC converter CNV added to the DC voltage Vdc1 output from the power supply device PS. In this case, the added voltage value (total voltage value) of the DC voltages Vdc1 and Vdc2 is defined by the charging voltage Vb of the storage battery unit 50 and increases as the charging voltage Vb increases.

  For this reason, at the beginning of the output of the DC voltage Vdc2 by the DCDC converter CNV, the voltage value of the DC voltage Vdc2 is less than the reference voltage value Vref2, so that the control circuit 29 of the DCDC converter CNV has a voltage value Vdc2 of the DC voltage Vdc2. Is controlled so as to increase the duty ratio of the switching element in the switching circuit 25 so as to be defined as the reference voltage value Vref2. However, as described above, the added voltage value of the DC voltages Vdc1 and Vdc2 is defined as the charging voltage Vb of the storage battery unit 50, and the DC voltage Vdc1 is equal to the threshold voltage Vth (voltage value close to the reference voltage value Vref1). It is a voltage. For this reason, the voltage value Vdc2 of the direct-current voltage Vdc2 is suppressed to a low voltage value, and then rises as the charging voltage Vb rises.

  In this state, even after the DCDC converter CNV starts outputting the DC voltage Vdc2, the voltage value of the charging voltage Vb of the storage battery unit 50 becomes a predetermined charging voltage value (total voltage value of each reference voltage value Vref1, Vref2). Until it reaches, the charging current Idc tends to flow into the storage battery unit 50 with a large current value. However, in the charging device CH, the DCDC converter CNV that has started to output the DC voltage Vdc2 activates the constant current voltage drooping type overcurrent protection function, thereby limiting the current value of the charging current Idc. That is, the control circuit 29 of the DCDC converter CNV controls the duty ratio with respect to the switch element of the switching circuit 25, whereby the current value Idc2 of the direct current Idc2, that is, the current value of the charging current Idc is changed to the reference current value Iref2 (<reference current The operation of maintaining the value Iref1) is performed.

  As a result, the charging device CH (in this case, the power supply device PS and the DCDC converter CNV) is charged with the storage battery unit 50 and the voltage value of the charging voltage Vb becomes the reference voltage values Vref1, Vref2 as shown in FIG. Until the total voltage value is reached, constant current charging is performed in which the current value of the charging current Idc is defined as the reference current value Iref2 and output to the storage battery unit 50.

  In this state, a part of the direct current Idc1 output from the power supply device PS is output (supplied) to the storage battery unit 50 as the direct current Idc, and the rest is output (supplied) to the DCDC converter CNV. .

Here, in order to facilitate understanding of the invention, when the efficiency of the DCDC converter CNV is assumed to be 100%, when the current value Idc2 of the direct current Idc2 output from the DCDC converter CNV is the reference current value Iref2, The current value of the direct current Idc3 supplied from the power supply device PS to the DCDC converter CNV (in this example, this current value is also expressed as “current value Idc3”) is expressed by the following equation.
Current value Idc3 = Vdc2 × Iref2 / Vdc1

Further, the current value Idc1 of the direct current Idc1 output from the power supply device PS is a total value of the respective current values Idc2 (= Iref2) and Idc3. For this reason, the current value Idc1 is expressed by the following equation.
Current value Idc1 = Iref2 + Vdc2 × Iref2 / Vdc1
= Iref2 (1 + Vdc2 / Vdc1)

  Further, when the threshold voltage Vth is defined to be the same as the reference voltage value Vref1 or a voltage value slightly lower than the reference voltage value Vref1 as in this example, the voltage of the DC voltage Vdc1 output from the power supply device PS. The value Vdc1 rises to the reference voltage value Vref1 in a short time after reaching the threshold voltage Vth. In addition, after the voltage value Vdc1 of the DC voltage Vdc1 reaches the reference voltage value Vref1 in this way, in the power supply device PS, the control circuit 9 controls the duty ratio for the switch element of the switching circuit 5, Constant voltage control is performed to maintain the voltage value Vdc1 of the DC voltage Vdc1 at the reference voltage value Vref1.

  As a result, after the voltage value Vdc1 of the DC voltage Vdc1 reaches the reference voltage value Vref1, the voltage value Vdc1 among the parameters of the equation of the current value Idc1 is constant at the reference voltage value Vref1, and thus the current The voltage value Vdc2 among the parameters of the expression of the value Idc1 gradually increases from a value sufficiently lower than the voltage value Vdc1 as the charging voltage Vb of the storage battery unit 50 increases. Therefore, the current value Idc1 of the direct current Idc1 gradually increases from a current value substantially equal to the reference current value Iref2.

  In this charging device CH, as described above, the maximum value ((Vref1 + Vref2) × Iref2) of the power that the charging device CH supplies to the storage battery unit 50 when charging the storage battery unit 50 is the power that the power supply device PS can output. The reference voltage value Vref2 and the reference current value Iref2 are defined so as to be less than the maximum value (Vref1 × Iref1). That is, the power Wa (= (Iref1-Iref2) × Vref1) shown in FIG. 3 is defined to be larger than the power Wb (= Vref2 × Iref2) shown in FIG. In other words, the surplus power of the power supply device PS when the DCDC converter CNV starts operation (that is, when constant current charging at the reference current value Iref2 by the charging device CH is started) becomes larger than the power Wb. It is prescribed.

  Therefore, the power supply apparatus PS supplies the DC current Idc3 having a sufficient current value Idc3 to the DCDC converter CNV that has started operation, and the DC current Idc2 having the reference current value Iref2 to the storage battery unit 50 together with the DCDC converter CNV. Continue to supply.

  Thereby, the charging voltage Vb of the storage battery unit 50 gradually increases and then reaches the total voltage value (Vref1 + Vref2) of the reference voltage values Vref1 and Vref2. After reaching this state, in the DCDC converter CNV, the control circuit 29 is controlled to maintain the voltage value Vdc2 of the DC voltage Vdc2 at the reference voltage value Vref2 while controlling the duty ratio for the switching elements of the switching circuit 25. Execute voltage control. Therefore, the charging device CH shifts the charging operation from constant current charging at the reference current value Iref2 to constant voltage charging at a constant voltage value (Vref1 + Vref2).

  Thus, in this charging device CH, when the charging voltage Vb of the storage battery unit 50 is lower than the threshold voltage Vth (when it is a low voltage), only the power supply device PS first shifts to the operating state, and the storage battery unit 50, after that, when the charging voltage Vb reaches the threshold voltage Vth, the DCDC converter CNV shifts to the operating state, and performs the charging for the storage battery unit 50 together with the power supply device PS, and so on. Power supply device PS and DCDC converter CNV, whose outputs are connected in series, sequentially shift to the operating state in this order, and charge storage battery unit 50.

  Accordingly, the charging device CH can charge the storage battery unit 50 having a low charging voltage Vb. Further, the charging device CH charges the storage battery unit 50 only by the power supply device PS when the charging voltage Vb at which the power supply efficiency decreases is low, and when the charging voltage Vb reaches the threshold voltage Vth (the charging voltage Vb is When the voltage becomes higher to some extent), the remaining DCDC converter CNV is shifted to the operating state, and the storage battery unit 50 is charged to a higher charging voltage Vb by the power supply device PS and the DCDC converter CNV. For this reason, in this charging device CH, the power supply device PS and the DCDC converter CNV operate simultaneously in a state where the power supply efficiency is low (for example, the power supply device PS outputs the DC voltage Vdc1 in a state of less than 20% of the reference voltage value Vref1). And the occurrence of a situation in which the DCDC converter CNV outputs the DC voltage Vdc2 in a state of less than 20% of the reference voltage value Vref2 is avoided. Has been.

  When the charging device CH starts the charging operation for the storage battery unit 50, if the charging voltage Vb of the storage battery unit 50 is higher than the threshold voltage Vth, the power supply device PS starts operating and starts outputting the DC voltage Vdc1. Immediately after, the voltage value Vdc1 of the DC voltage Vdc1 exceeds the threshold voltage Vth. For this reason, the DCDC converter CNV also immediately starts to operate. Therefore, as described above, charging device CH executes constant current control in which the current value of charging current Idc is defined as reference current value Iref2 and is output to storage battery unit 50, and charging of storage battery unit 50 is started. However, even at this time, the power supply device PS and the DCDC converter CNV do not operate in a state where the voltage values Vdc1 and Vdc2 of the respective DC voltages Vdc1 and Vdc2 are low. A reduction in efficiency is avoided.

  In this way, when constant voltage charging at a constant voltage value (Vref1 + Vref2) by the charging device CH is continuously executed, the current value of the charging current Idc supplied to the storage battery unit 50 is gradually increased from the reference current value Iref2. To decrease. Therefore, the control circuit 9 of the power supply device PS controls the switch element of the switching circuit 5 to the OFF state when the current value of the charging current Idc reaches the lower limit current value Imin (<reference current value Iref2). The generation operation of the DC voltage Vdc1 is stopped (the DC voltage Vdc becomes zero volts). As a result, the DCDC converter CNV also stops operating, and charging of the storage battery unit 50 by the charging device CH is completed.

  Thus, in this charging device CH, the output of the power supply device PS that first shifts to the operating state and starts outputting the DC voltage Vdc1 is output to the DCDC converter CNV that shifts to the operating state using the DC voltage Vdc1 as the operating voltage. The output is connected in series, and the DCDC converter CNV has a threshold voltage defined in advance as one of the maximum output voltage value (reference voltage value Vref1) for the DC voltage Vdc1 and a voltage value in the vicinity of the maximum output voltage value. When Vth is reached, the operation state is entered, and the charging current Idc is supplied to the storage battery unit 50 at a constant reference current value Iref2.

  Therefore, according to this charging device CH, the low-voltage storage battery unit 50 whose charging voltage Vb is lower than the threshold voltage Vth is efficiently charged only by the power supply device PS until the charging voltage Vb reaches the threshold voltage Vth. After the voltage Vb reaches the threshold voltage Vth (when the charging voltage Vb is high to some extent), the storage battery unit 50 is set to a higher charging voltage Vb (total of the reference voltage values Vref1, Vref2) by the power supply device PS and the DCDC converter CNV. Voltage value). Therefore, according to the charging device CH, the power supply efficiency of the charging device CH as a whole is maintained sufficiently high, and the storage battery unit 50 having a low charging voltage Vb and the storage battery unit 50 having a high charging voltage Vb are charged. be able to.

  In the above example, the input voltage detection circuit 24 of the DCDC converter CNV detects the voltage value Vdc1 of the DC voltage Vdc1 output from the power supply device PS and compares it with the threshold voltage Vth. The voltage value of the charging voltage Vb of the storage battery unit 50 is lower than the voltage value Vdc1 of the DC voltage Vdc1 by the forward voltage of the rectifying element D2 before the operation of the DCDC converter CNV, but the DC voltage Vdc1 It can be said that the voltage value is substantially equal to the voltage value Vdc1. Therefore, it is possible to adopt a configuration in which the input voltage detection circuit 24 of the DCDC converter CNV detects the charging voltage Vb of the storage battery unit 50 and compares it with the threshold voltage Vth.

10, 30 Positive output terminal 11, 31 Negative output terminal 22 Positive input terminal 23 Negative input terminal 50 Storage battery unit CNV DCDC converter Iref1, Iref2 Reference current value PS Power supply device Vb Charging voltage Vdc, Vdc1, Vdc2 DC voltage Vref1, Vref2 Reference voltage Value (maximum output voltage value)
Vth threshold voltage

Claims (1)

A power supply device having a constant current voltage drooping type overcurrent protection characteristic and outputting a DC voltage between a positive output terminal and a negative output terminal;
A positive input terminal is connected to the positive output terminal of the power supply device and a negative input terminal is connected to the negative output terminal of the power supply device to operate the DC voltage from the power supply device as an operating voltage. A DCDC converter that outputs a DC voltage between the output terminal and the negative output terminal and has a constant current voltage drooping type overcurrent protection characteristic;
The power supply apparatus and the DCDC converter are connected in series by connecting the positive output terminal of the power supply apparatus and the negative output terminal of the DCDC converter, and the positive output terminal of the DCDC converter. A charging target is connected between the negative output terminal of the power supply device,
In the DCDC converter, a constant current value at the time of voltage droop in the overcurrent protection characteristic of the DCDC converter is defined to be lower than a constant current value at the time of voltage droop in the overcurrent protection characteristic of the power supply device, and the power supply The operating state when the voltage value of the DC voltage of the device reaches a threshold voltage defined in advance as one of the maximum output voltage value for the DC voltage of the power supply device and a voltage value in the vicinity of the maximum output voltage value And a charging device for supplying a charging current to the charging target at the constant current value of the DCDC converter.

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