JP6733512B2 - Charger - Google Patents

Description

The present invention relates to a charger.

There is a charger that performs constant current/constant voltage control without using a charging current command value transmitted from a battery pack when charging a secondary battery. In such a charger, for example, a control IC (Integrated Circuit) executes constant current control so that a voltage corresponding to an output current from a DC/DC (Direct Current/Direct Current) converter unit matches a predetermined reference voltage. To do. Then, when the output voltage from the charger reaches the full-charge voltage, the control IC executes constant voltage control so that the output voltage from the DC/DC converter unit matches a predetermined reference voltage.

Note that as related techniques, the techniques described in Patent Documents 1 and 2 are known.

JP, 10-136578, A Japanese Patent No. 3213401

However, when the voltage compared with the reference voltage is not input to the control IC from the DC/DC converter unit at the moment when the constant current charging is switched to the constant voltage charging, the control of the control IC becomes unstable. As a result, the duty ratio of the PWM (Pulse Width Modulation) signal output from the control IC to the DC/DC converter unit increases, and there is a risk that an overvoltage may be output from the charger to the battery pack.

An object of one aspect of the present invention is to provide a charger that prevents an overvoltage from being output from the charger to the battery pack when switching from constant current charging to constant voltage charging in the charger.

A charger, which is one mode of the present invention, includes a control circuit, a DC/DC converter unit, a current detection unit, a feedback resistor, a switcher, and a charging control unit. The control circuit generates the PWM signal according to the difference between the reference voltage and the feedback voltage. The DC/DC converter unit outputs a predetermined output voltage according to the PWM signal. The current detection unit outputs the first voltage corresponding to the output current from the DC/DC converter unit. The feedback resistor divides the output voltage from the DC/DC converter unit. The switcher switches the feedback voltage input to the control circuit to the first voltage or the second voltage divided by the feedback resistor. The charge control unit controls the reference voltage and the feedback voltage.

The charging control unit controls the reference voltage to a first reference voltage that matches the output current from the DC/DC converter unit with a predetermined constant current when performing the constant current charging, and uses the first voltage as the feedback voltage. Controls the switch to input to the control circuit. Further, the charging control unit lowers the reference voltage to an operation stop voltage or less at which the operation of the control circuit stops when the output voltage reaches a predetermined constant voltage, and the second voltage is input to the control circuit as a feedback voltage. Control the switch. Further, the charge control unit gradually raises the reference voltage from the operation stop voltage to the second reference voltage that matches the output voltage with the constant voltage, and then performs the constant voltage charging.

According to the charger according to the embodiment, it is possible to prevent the charger from outputting an overvoltage to the battery pack when switching from constant current charging to constant voltage charging.

It is a figure which shows the schematic structural example of the whole charger according to embodiment. It is a figure which shows the detailed structural example of some chargers according to embodiment. FIG. 7 is an exemplary flow diagram of charging control performed by a charger according to an embodiment.

Embodiments will be described below in detail with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration example of the entire charger according to the embodiment. In the configuration example illustrated in FIG. 1, the charger 1, which is an example of the charger according to the embodiment, includes four power supply units 11 and a charger control unit 12.

Each power supply unit 11 converts AC power (for example, three-phase AC power) input from the power supply 2 into predetermined DC power, and outputs the DC power to the secondary battery 31 of the battery pack 3. The secondary battery 31 is composed of, for example, one or more lithium ion batteries, nickel hydrogen batteries, or electric double layer capacitors. Note that, in the configuration example shown in FIG. 1, the four power supply units 11 are included in the charger 1, but the charger according to the embodiment may include any number of power supply units.

Each power supply unit 11 includes three DC conversion units 111, a power supply unit control unit 112, and an AC/DC (Alternating Current/Direct Current) converter 113.
The three DC converters 111 respectively convert corresponding one-phase AC power of the three-phase AC power input from the power supply 2 to the power supply unit 11 into predetermined DC power. Note that the configuration example shown in FIG. 1 includes three DC converters 111, but the charger according to the embodiment includes an arbitrary number of DC converters according to the power transmission format of the power supply 2, and the like. You can

Each DC converter 111 includes a PFC (Power Factor Correction) circuit 1111, a DC/DC converter 1112, and a reference voltage output circuit 1113.
The PFC circuit 1111 removes a harmonic component of the input AC current and converts the input AC voltage into a DC voltage. The DC/DC converter 1112 generates a DC voltage matching the reference voltage input from the reference voltage output circuit 1113 from the DC voltage input from the PFC circuit 1111 and outputs the DC voltage. The reference voltage input to the DC/DC converter 1112 is controlled by the power supply unit controller 112 via the reference voltage output circuit 1113.

The power supply unit controller 112 is an example of a charging controller according to the embodiment. The power supply unit controller 112 is configured by, for example, a CPU (Central Processing Unit), a multi-core CPU, or a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), or the like). The power supply unit control unit 112 controls the operation of each unit included in the power supply unit 11. For example, the power supply unit control unit 112 communicates with the charger control unit 12 and controls the output from the DC/DC converter 1112 by constant current and constant voltage.

The power supply unit controller 112 operates by the DC power supplied from the AC/DC converter 113. The AC/DC converter 113 converts AC power input from the power supply 2 into DC power and outputs the DC power to the power supply unit controller 112.

The charger control unit 12 includes an AC/DC converter 121 and a charger control unit 122.
The charger control unit 122 is composed of, for example, a CPU, a multi-core CPU, or a programmable device (FPGA, PLD, or the like). The charger control unit 122 communicates with the power supply unit control unit 112 and the battery control unit 32 of the battery pack 3 to control the operation of each unit included in the charger 1.

The charger control unit 122 operates with the DC power supplied from the AC/DC converter 121. The AC/DC converter 121 converts the AC power input from the power source 2 into DC power and outputs the DC power to the charger control unit 122.

A specific example of the charging control executed by the charger according to the embodiment will be further described with reference to FIGS. 2 and 3.
FIG. 2 is a diagram showing a detailed configuration example of a part of the charger according to the embodiment. FIG. 2 shows only some of the components included in the charger 1 shown in FIG. For example, FIG. 2 shows the components of any one DC converter 111 included in any one power supply unit 11 and the power supply unit controller 112. Also, the charger controller 122 is shown. In the configuration example shown in FIG. 2, each DC converter 111 includes a PFC circuit 1111, a DC/DC converter 1112, and a reference voltage output circuit 1113.

The DC/DC converter 1112 includes a first switching element S1, a control circuit Ccv, a DC/DC converter unit CONV, a current detection unit SNSR, a first feedback resistor Rf1, a second feedback resistor Rf2, a fuse F, and a diode D. including. In addition, the DC/DC converter unit CONV includes a second switching element S2, a third switching element S3, an inductor L, and a first capacitor C1.

The first switching element S1 is an example of a switch according to the embodiment. The first switching element S1 is composed of, for example, a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an electromagnetic relay.

The reference voltage and the feedback voltage are input to the control circuit Ccv. The control circuit Ccv generates a PWM signal output to the DC/DC converter unit CONV according to the difference between the reference voltage and the feedback voltage so that the feedback voltage matches the reference voltage.

The reference voltage input to the control circuit Ccv is generated by the reference voltage output circuit 1113 under the control of the power supply unit controller 112. For example, during constant current charging, the reference voltage is controlled to the first reference voltage that matches the output current from the DC/DC converter unit CONV with a predetermined constant current. Further, during constant voltage charging, the reference voltage is controlled to the second reference voltage that matches the output voltage from the DC/DC converter unit CONV with a predetermined constant voltage.

The feedback voltage input to the control circuit Ccv is switched to the first voltage or the second voltage by the first switching element S1 according to the control of the power supply unit controller 112. The first voltage is a voltage corresponding to the output current from the DC/DC converter unit CONV, and is detected and output by the current detection unit SNSR. The current detection unit SNSR is composed of, for example, a Hall element or a shunt resistor. The second voltage is a voltage obtained by dividing the output voltage from the DC/DC converter unit CONV by the first feedback resistor Rf1 and the second Rf2. As shown in FIG. 2, the first voltage and the second voltage are also output to the power supply unit controller 112.

The second switching element S2 and the third switching element S3 are composed of, for example, semiconductor switches such as MOSFETs. In the DC/DC converter unit CONV, the second switching element S2 and the third switching element S3 are respectively turned on or off according to the PWM signal input from the control circuit Ccv, and the DC voltage input from the PFC circuit 1111 is time-divided. .. The inductor L and the first capacitor C1 smooth the time-divided DC voltage and output a desired DC voltage/current to the secondary battery 31 in the battery pack 3. The fuse F is provided to prevent an overcurrent from being output from the DC/DC converter 1112, and is blown when the output current via the inductor L and the first capacitor C1 becomes an overcurrent. The diode D prevents a failure of the DC/DC converter unit due to backflow from the battery 31 to the DC/DC converter 1112.

The reference voltage output circuit 1113 includes a reference voltage generation circuit Cvr, a second capacitor C2, a resistor R, and a fourth switching element S4.
The reference voltage generation circuit Cvr generates a reference voltage from a predetermined voltage source Vs. The fourth switching element S4 is turned on or off according to the pulse signal output from the power supply unit controller 112. The predetermined resistor R is connected in series with the fourth switching element S4, and the second capacitor C2 is connected in parallel with the fourth switching element S4 and the resistor R. The second capacitor C2 charges and discharges the reference voltage output from the reference voltage generation circuit Cvr according to whether the fourth switching element S4 is on or off. As a result, the reference voltage output from the reference voltage generation circuit Cvr is controlled to the predetermined reference voltage by the power supply unit controller 112, and the predetermined reference voltage is output to the control circuit Ccv.

FIG. 3 is an exemplary flow diagram of charging control performed by a charger according to an embodiment.
After the battery pack 3 is connected to the charger 1, the charger control unit 122 receives the current voltage of the secondary battery 31 and the full charge voltage of the secondary battery 31 from the battery control unit 32 (step S101). .. The charger control unit 122 compares the current voltage of the secondary battery 31 with the full charge voltage. When the current voltage of the secondary battery 31 is the full charge voltage (“NO” in step S102), the series of processes proceeds to step S110. When the current voltage of the secondary battery 31 is less than the full charge voltage (“YES” in step S102), the series of processes proceeds to step S103.

In step S103, the charger control unit 122 instructs the power supply unit control unit 112 to perform constant current charging. The power supply unit controller 112 controls the DC/DC converter 1112 with a constant current. Specifically, the power supply unit controller 112 controls the first switching element S1 so that the first voltage as the feedback voltage is input to the control circuit Ccv. In addition, the power supply unit control unit 112 controls the duty ratio of the pulse signal output to the fourth switching element S4 to set the reference voltage input from the reference voltage output circuit 1113 to the control circuit Ccv to the first reference voltage. Control.

During execution of the constant current charging, the power supply unit controller 112 outputs the output current value from the DC/DC converter 1112 calculated from the first voltage and the output current from the DC/DC converter 1112 calculated from the second voltage. The voltage value is output to the charger control unit 122. The charger control unit 122 calculates the output power from each DC/DC converter 1112 by multiplying the output current value and the output voltage value input from each power supply unit control unit 112. The charger control unit 122 calculates the current output power of the charger 1 by summing the calculated output power values.

If the current output power of charger 1 is less than the rated power of charger 1 (“NO” in step S104), the series of processes proceeds to step S106. When the current output power of the charger 1 reaches the rated power of the charger 1 (“YES” in step S104), the series of processes proceeds to step S105.

In step S105, the charger control unit 122 instructs the power supply unit control unit 112 to perform constant power charging. The power supply unit controller 112 controls the DC/DC converter 1112 at a constant power. Specifically, the power supply unit control unit 112 controls the duty ratio of the pulse signal output to the fourth switching element S4, so that the first reference value increases in accordance with the increase in the output voltage from the DC/DC converter 1112. Lower the voltage. As described above, by performing the constant power charging during the constant current charging, the output voltage from the charger 1 can be increased to a predetermined voltage (for example, the full charging voltage), and the secondary battery 31 can be charged to the full charging voltage. Can be charged.

The charger control unit 122 calculates the current output voltage of the charger 1 by summing the output voltage values input from the power supply unit control units 112. When the current output voltage of the charger 1 is less than the full charge voltage (“NO” in step S106), the series of processes returns to step S103.

When the current output voltage of the charger 1 reaches the full charge voltage (“YES” in step S106), the power supply unit control unit 112 instructs the power supply unit control unit 112 to switch from constant current charging to constant voltage charging. To do. The power supply unit control unit 112 controls the duty ratio of the pulse signal output to the fourth switching element S4 to lower the reference voltage below a predetermined operation stop voltage at which the operation of the control circuit Ccv stops (step S107). ). As a result, the operation of the control circuit Ccv stops.

The power supply unit controller 112 controls the first switching element S1 so that the second voltage as the feedback voltage is input to the control circuit Ccv (step S108). Then, the power supply unit control unit 112 gradually increases the reference voltage from the operation stop voltage to the second reference voltage by controlling the duty ratio of the pulse signal output to the fourth switching element S4 (step S109).

After the processing in step S109 is executed, the power supply unit control unit 112 controls the DC/DC converter 1112 at a constant voltage while the output current from the charger 1 is equal to or higher than a predetermined current (“NO” in step S111). (Step S110). When the output current from the charger 1 becomes less than the predetermined current (“YES” in step S111), the series of processes ends.

In this way, after the operation of the control circuit Ccv is stopped (step S107), the feedback voltage input to the control circuit Ccv is switched (step S108). Therefore, when the constant current charging is switched to the constant voltage charging, the feedback voltage compared with the reference voltage is not input from the DC/DC converter unit CONV to the control circuit Ccv, and the control of the control circuit Ccv becomes unstable. There is no such thing. Therefore, according to the charger according to the embodiment, it is possible to prevent the overvoltage from being applied from the charger to the secondary battery at the moment when the constant current charging is switched to the constant voltage charging.

After the feedback voltage input to the control circuit Ccv is switched (step S108), the reference voltage is soft-started from the operation stop voltage to the second reference voltage (step S109). Therefore, when the constant current charging is switched to the constant voltage charging, the output voltage from the charger 1 gradually increases in accordance with the soft-started reference voltage. Therefore, according to the charger according to the embodiment, it is possible to prevent the overvoltage from being applied from the charger to the secondary battery at the moment when the constant current charging is switched to the constant voltage charging.

The present invention is not limited to the above embodiments, and various improvements and changes can be made without departing from the gist of the present invention.
For example, when the current output power of the charger 1 reaches the rated power of the charger 1 during the switching from the constant current charging to the constant voltage charging (during the soft start of the reference voltage in step S109), the power supply unit controller 112 may be configured to perform constant power control. The switching from the constant current charging to the constant voltage charging means that the power supply unit controller 112 gradually increases the reference voltage from the operation stop voltage to the second reference voltage. According to such a configuration, after switching from the constant current charging to the constant voltage charging, the output current from the charger 1 is returned to the predetermined constant current at the constant current charging, and the output voltage from the charger 1 is charged after the constant current charging. Can be returned to a predetermined constant voltage (for example, full charge voltage). Therefore, the secondary battery after being charged with the constant current can be appropriately charged with the constant voltage.

1 Charger 2 Power Supply 3 Battery Pack 11 Power Supply Unit 12 Charger Control Unit 31 Secondary Battery 32 Battery Control Unit 111 DC Converter 112 Power Supply Unit Controller 113 AC/DC Converter 121 AC/DC Converter 122 Charger Controller 1111 PFC Circuit 1112 DC/DC converter 1113 Reference voltage output circuit C1 First capacitor C2 Second capacitor Ccv Control circuit CONV DC/DC converter unit Cvr Reference voltage generation circuit D Diode F Fuse L Inductor R Resistance Rf1 First feedback resistance Rf2 Second feedback resistor S1 First switching element S2 Second switching element S3 Third switching element S4 Fourth switching element SNSR Current detector Vs Voltage source

Claims (3)

A control circuit for generating a PWM (Pulse Width Modulation) signal according to the difference between the reference voltage and the feedback voltage;
A DC/DC (Direct Current/Direct Current) converter unit that outputs a predetermined output voltage according to the PWM signal;
A current detector that outputs a first voltage corresponding to the output current from the DC/DC converter,
A feedback resistor for dividing the output voltage from the DC/DC converter unit;
A switch for switching the feedback voltage input to the control circuit to the first voltage or a second voltage divided by the feedback resistor;
Including a charge control unit for controlling the reference voltage and the feedback voltage,
The charging control unit,
When performing constant current charging, the reference voltage is controlled to a first reference voltage that matches the output current with a predetermined constant current, and the first voltage is input to the control circuit as the feedback voltage. To control the switch,
When the output voltage reaches a predetermined constant voltage, the reference voltage is lowered below an operation stop voltage at which the operation of the control circuit stops, and the second voltage is input to the control circuit as the feedback voltage. Control the switch,
A charger that performs constant voltage charging after gradually increasing the reference voltage from the operation stop voltage to a second reference voltage that matches the output voltage with the constant voltage. The charger according to claim 1, wherein
The charger is configured to perform constant power control when the output power of the charger calculated from the output current and the output voltage reaches a predetermined power during the constant current charging. The charger according to claim 1 or 2, wherein
The charging control unit gradually increases the reference voltage from the operation stop voltage to the second reference voltage, and the output power of the charger calculated from the output current and the output voltage reaches a predetermined power. Then a charger that executes constant power control.

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