JP2002112465A - Charging apparatus for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging apparatus for vehicle which enables to increase an output current without enlarging a step-down DC/DC converter. SOLUTION: A charger 1 has switching elements 10A and 10B which intermittent an input current supplied power from a high voltage battery 3 in vehicle with Pulse Width Modulation, has a step-down DC/DC converter which switches a voltage of an input current intermittent and directly supplies power to a low voltage load 2 without a low voltage battery. This converter is controlled by a controller 5. The controller 5 controls the step-down DC/DC converter that an input power is saturated in the prescribed maximum value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vehicle charging device.

[0002]

2. Description of the Related Art In recent years, vehicles powered by internal combustion engines, hybrid vehicles, and electric vehicles (including a pure battery type and a fuel cell type) are capable of supplying power to a large electric load with low loss and light weight. In order to realize such a circuit system, it has been proposed to employ a dual-power-supply type vehicle circuit system that drives a general-purpose low-voltage load at a low voltage and drives a special large electric load at a high voltage.

In a conventional dual-powered vehicle circuit system, a high-voltage battery that supplies power to a high-voltage circuit, a low-voltage battery that supplies power to a low-voltage circuit meter, and a step-down DC-DC converter that converts a voltage from the high-voltage battery and supplies power to the low-voltage battery Has been proposed.

If a low-voltage battery is omitted in this dual-power-supply type vehicle circuit system and a system in which a step-down DC-DC converter directly supplies power to a low-voltage load is employed, there are advantages in cost and reduction in size and weight of the vehicle.

However, in a vehicle charging device, it is necessary to provide overload protection in order to prevent a short circuit accident on the low voltage load side and a failure of a semiconductor element constituting the step-down DC-DC converter. In this type of power supply circuit, the output current is limited so as not to exceed a predetermined value.

However, in the above-described output current saturation control, it is necessary to employ a high-output step-down DC-DC converter in order to secure power supply to a large electric load.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a vehicle charging device capable of increasing output current without increasing the size of a step-down DC-DC converter.

[0008]

According to a first aspect of the present invention, there is provided a vehicle charging apparatus having a switching element for intermittently inputting a current supplied from a high-voltage battery mounted on a vehicle in a PWM (pulse width modulation) system. A step-down DC-DC converter for converting the input current into a voltage and directly supplying power to a low-voltage load without passing through a low-voltage battery, and a control unit for controlling the step-down DC-DC converter, wherein the control unit includes: Detecting means for obtaining input power supplied from the high-voltage battery to the step-down DC-DC converter, and by controlling the duty ratio of the switching element even after the input power reaches a predetermined maximum value, Control means for permitting an increase in the output current within a range where the input power does not exceed the maximum value.

As a result, the output current that can be supplied to the low-voltage load can be increased while ensuring safety.

According to a second aspect of the present invention, in the vehicle charging apparatus according to the first aspect, the control means further controls the output voltage of the step-down DC-DC converter within a range where the input power does not exceed the maximum value. It is characterized in that it is controlled to the rated value.

As a result, the output voltage stability can be improved without complicating the circuit configuration.

According to a third aspect of the present invention, there is provided a vehicle charging apparatus having a switching element for intermittently inputting a current supplied from a high-voltage battery mounted on a vehicle in a PWM (pulse width modulation) system, and converting the intermittent input current into a voltage. A step-down DC-DC converter that directly supplies power to a low-voltage load without passing through a low-voltage battery, and a control unit that controls the step-down DC-DC converter, wherein the control unit includes the step-down DC-DC converter. Detecting means for determining the output power output from the DC converter, and controlling the duty ratio of the switching element after the output power reaches a predetermined maximum value, so that the output power does not exceed the maximum value. And an output current control means for permitting an increase in the output current.

Thus, the output current that can be supplied to the low-voltage load can be increased while ensuring safety.

According to a fourth aspect of the present invention, in the vehicle charging apparatus according to the third aspect, the control means further controls the output voltage of the step-down DC-DC converter within a range where the output power does not exceed the maximum value. It is characterized in that it is controlled to the rated value.

As a result, the output voltage stability can be improved with almost no complicated circuit configuration.

According to a fifth aspect of the present invention, there is provided a vehicle charging apparatus having a switching element for intermittently inputting an electric current supplied from a high-voltage battery mounted on a vehicle in a PWM (pulse width modulation) system, and converting the intermittent input current into a voltage. A step-down DC-DC converter that directly supplies power to a low-voltage load without passing through a low-voltage battery, and a control circuit that controls the step-down DC-DC converter, wherein the control unit includes the step-down DC-DC converter. Detecting means for determining the power loss of the DC converter, input voltage detecting means, and controlling the duty ratio of the switching element after the power loss reaches a predetermined maximum value, whereby the power loss reduces the maximum value. Output current control means for permitting an increase in output current within a range not exceeding.

As a result, the output current that can supply power to the low-voltage load can be increased while ensuring safety.

According to a sixth aspect of the present invention, in the vehicle charging apparatus according to the fifth aspect, the control means further controls the output voltage of the step-down DC-DC converter within a range where the power loss does not exceed the maximum value. It is characterized in that it is controlled to the rated value.

As a result, the output voltage stability can be improved without complicating the circuit configuration.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a vehicle charging apparatus according to the present invention will be described below with reference to the drawings.

[0021]

Embodiment 1 FIG. 1 shows a block diagram of a vehicle charging apparatus according to Embodiment 1.

(Circuit configuration) 1 is a charger, 2 is a low voltage load,
Reference numeral 3 denotes a high-voltage battery, 4 denotes a current sensor, and 5 denotes a controller (control means in the present invention).

As shown in FIG. 2, the charger 1 is a so-called step-down DC-DC converter, and includes an inverter 10, a transformer 11, and a rectifier 12. Although a choke coil and a capacitor for current smoothing are provided in necessary portions of the charger 1, the circuit is not shown.

The inverter 10 includes a pair of inverters 10A, each of which is modularized or integrated on one chip.
The high-voltage DC power applied from the high-voltage battery 3 is converted to AC power. The transformer 11 steps down the AC power, and the rectifier circuit 12 rectifies the AC power and feeds it to the low-voltage load 2. The inverter 10 may be changed to a circuit configuration capable of bidirectional power transmission.
Further, the charger 1 may be changed to a circuit configuration in which the current of the choke coil is intermittently switched at a constant cycle by a single switching transistor, and the generated high voltage is output through a diode.

The controller 5 (control means) includes an inverter (switching element) 10
A and 10B (not shown) are controlled at a predetermined PWM cycle. Since this type of step-down DC-DC converter is well known, a detailed description is omitted. Thereby, the charger 1
The high-voltage DC power of the high-voltage battery 3 is stepped down and supplied to the low-voltage load 2. Therefore, in this embodiment, the charger 1
It does not charge the low voltage battery.

The current sensor 4 detects the input current of the charger 1 input to the charger 1 and sends a signal to the controller 5. Similarly, a voltage detection circuit (not shown) detects the input voltage of the charger 1, that is, the high voltage battery 3. To the controller 5 and the output voltage of the charger 1, that is, the applied voltage signal of the low-voltage load 2.

(Description of Operation) The control operation of the controller 5 will be described below with reference to the flowchart shown in FIG.

First, the input voltage and the input current of the charger 1 are read, and these are integrated to obtain the input power (S10).
0).

Next, it is checked whether or not the calculated input power is less than a predetermined maximum value (S102). If the input power is less than the maximum value, a difference ΔV between the output voltage of the charger 1 and a predetermined rated value stored in advance is calculated. Then, in accordance with the difference ΔV, the duty ratio of the inverters 10A and 10B is increased or decreased to maintain the output voltage of the charger 1, that is, the step-down DC-DC converter at a predetermined rated value (S106).

In S102, if the calculated input power is equal to or more than the predetermined maximum value, a difference ΔP between the calculated input power and the maximum value is calculated (S108), and according to the difference ΔP, the CMOS inverters 10A and 10B , The input power of the charger 1, that is, the step-down DC-DC converter is maintained at the maximum value (S110).

(Effect of Embodiment) According to the power supply control of the vehicle charging apparatus of this embodiment configured as described above, the normal overcurrent control for controlling the output current or the input current so as not to exceed a predetermined maximum value. The output current can be increased under the condition that the input power is constant, and the low voltage load 2 can be supplied with power. Therefore, even when the required output current increases due to connection of many low-voltage loads 2, the voltage applied to the low-voltage load 2 decreases, but the required output current increases accordingly.
The parallel operation of the low-voltage load 2 can be maintained.

Usually, many low-voltage loads 2 are designed to operate normally even when the applied voltage is slightly reduced (for example, about 20%). As a result, assuming that the input current is proportional to the output current, The output current can be increased by about 10%.

In this embodiment, the rated output voltage can be output to the low-voltage load 2 using the same circuit configuration until the input power reaches a predetermined maximum value. That is, in the present invention, in a low-voltage battery-less vehicle charging device that controls to output a rated output voltage, overload protection of a circuit is performed while maintaining a constant power consumption condition between the charger 1 and the low-voltage load 2. At the same time, the output current can be further increased as compared to the control in which the input current or the output current is simply reduced to a certain value or less.

[0034]

Second Embodiment A vehicle charging device according to a second embodiment will be described below with reference to FIG.

In this embodiment, in FIG. 1, the current sensor 4 detects the low-voltage current in the line connecting the rectifier 12 and the low-voltage load 2, and S100, S02 and S06 in the flowchart of FIG. 2 are changed. It was done.

That is, in this embodiment, the output voltage and the output current of the charger 1 are read, and the output is integrated to obtain the output power (S100).

Next, it is checked whether the calculated output power is less than a predetermined maximum value (S102), and if it is less, a difference ΔV between the output voltage of the charger 1 and a predetermined rated value stored in advance is calculated. (S104), and in accordance with the difference ΔV, the CM
By increasing or decreasing the duty ratio of the OS inverters 10A and 10B, the output voltage of the charger 1, that is, the step-down DC-DC converter is maintained at a predetermined rated value (S106).

In S102, if the calculated output power is equal to or more than the predetermined maximum value, a difference ΔP between the calculated output power and the maximum value is calculated (S108), and according to the difference ΔP, the CMOS inverters 10A, 10B , The output power of the charger 1, that is, the step-down DC-DC converter is maintained at the maximum value (S110).

(Effect of Embodiment) According to the power supply control of the vehicle charging apparatus of this embodiment configured as described above, the normal overcurrent control for controlling the output current or the input current so as not to exceed a predetermined maximum value. As compared with the above, the output current can be increased under the condition that the output power is constant, and the low voltage load 2 can be fed. Therefore, even when the required output current increases due to connection of many low-voltage loads 2, the voltage applied to the low-voltage load 2 decreases, but the required output current increases accordingly.
Parallel operation of the low-voltage load 2 can be maintained.

Normally, many low-voltage loads 2 are designed to operate normally even when the applied voltage is slightly reduced (for example, about 20%). As a result, the output current can be increased by about 10%. .

In this embodiment, the rated output voltage can be output to the low-voltage load 2 using the same circuit configuration until the output power reaches the predetermined maximum value. That is, the present invention provides a low-voltage battery-less vehicular charging device that performs control to output a rated output voltage, while maintaining a constant power consumption condition of the low-voltage load 2 to protect the circuit from overload, and to further simplify input and output. The output current can be increased as compared with the control in which the current or the output current is equal to or less than a fixed value.

[0042]

Third Embodiment A vehicle charging device according to a third embodiment will be described below with reference to FIG.

In this embodiment, in FIG.
Two current sensors 4 are used so as to detect both the input current and the output current. Further, S in the flowchart of FIG.
100, S02 and S06 are modified.

That is, in this embodiment, the pair of the input current and the input voltage of the charger 1 and the pair of the output voltage and the output current are read, and the two powers are integrated, respectively. Is calculated, and the difference between the calculated input power and output power is calculated, and this difference is set as the power loss Q of the charger 1 (S100).

Next, it is checked whether or not the calculated power loss Q is less than a predetermined maximum value (S102). If it is less, the difference ΔV between the output voltage of the charger 1 and a predetermined rating value stored in advance is determined. The duty ratio of the inverters 10A and 10B is increased or decreased according to the difference ΔV to maintain the output voltage of the charger 1, that is, the step-down DC-DC converter at a predetermined rated value (S106).

If the calculated power loss Q is equal to or greater than the predetermined maximum value in S102, a difference ΔP between the calculated power loss Q and the maximum value is calculated (S108), and according to the difference ΔP, the inverter 10A, The power loss Q of the charger 1, that is, the step-down DC-DC converter is maintained at the maximum value by increasing or decreasing the duty ratio of 10B (S110).

(Effect of Embodiment) According to the power supply control of the vehicle charging apparatus of this embodiment configured as described above, the normal overcurrent control for controlling the output current or the input current not to exceed a predetermined maximum value. The output current can be increased and the low-voltage load 2 can be fed under the condition that the power loss of the charger 1 is constant. Therefore, even when the required output current increases due to the connection of many low-voltage loads 2 and the like, the voltage applied to the low-voltage load 2 decreases, but the required output current increases and the low-voltage load 2 Parallel operation can be maintained.

Usually, many low-voltage loads 2 are designed to operate normally even when the applied voltage is slightly reduced (for example, about 20%), and as a result, the output current can be increased by about 10%. .

In this embodiment, the rated output voltage can be output to the low-voltage load 2 using the same circuit configuration until the power loss of the charger 1 reaches a predetermined maximum value. That is, the present invention provides a low-voltage battery-less vehicle charging device that controls to output a rated output voltage, while maintaining a constant power consumption condition of the charger 1 to protect the circuit from overload, and furthermore, by simply inputting power. The output current can be increased as compared with the control in which the current or the output current is equal to or less than a fixed value.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of a vehicle charging device according to a first embodiment.

FIG. 2 is a flowchart showing an operation of the charger shown in FIG.

[Explanation of symbols]

 1: Charger 2: Low voltage load 3: High voltage battery 4: Current sensor (detection means) 5: Controller (detection means, control means)

Claims (6)

[Claims] An input current supplied from an on-vehicle high-voltage battery is switched on and off by a PWM (pulse width modulation) method, and the on-off input current is converted to a low voltage without passing through a low-voltage battery. A step-down DC-DC converter that directly supplies power to a load; and a control unit that controls the step-down DC-DC converter. A vehicle charging apparatus, wherein the control unit supplies power from the high-voltage battery to the step-down DC-DC converter. Detecting means for determining the input power to be supplied, and controlling the duty ratio of the switching element even after the input power reaches a predetermined maximum value, so that the output current does not exceed the maximum value. Control means for permitting an increase in the vehicle charge. 2. The vehicle charging apparatus according to claim 1, wherein the control means controls the output voltage of the step-down DC-DC converter to a predetermined rated value within a range where the input power does not exceed the maximum value. A charging device for a vehicle, comprising: 3. A switching element for intermittently inputting a current supplied from a high-voltage battery mounted on a vehicle by a PWM (pulse width modulation) method, and converting the intermittent input current to a low voltage without passing through a low-voltage battery. A step-down DC-DC converter that directly supplies power to a load; and a control unit that controls the step-down DC-DC converter. A vehicle charging apparatus, wherein the control unit includes: an output power output from the step-down DC-DC converter. And a duty ratio of the switching element after the output power reaches a predetermined maximum value, thereby permitting the output current to increase within a range where the output power does not exceed the maximum value. And an output current control means. 4. The vehicle charging apparatus according to claim 3, wherein the control means controls the output voltage of the step-down DC-DC converter to a predetermined rated value within a range where the output power does not exceed the maximum value. A charging device for a vehicle, comprising: 5. A switching device for intermittently inputting a current supplied from a high-voltage battery mounted on a vehicle by a PWM (pulse width modulation) method, and converting the intermittent input current to a low voltage without passing through a low-voltage battery. A step-down DC-DC converter that directly supplies power to a load, and a control unit that controls the step-down DC-DC converter.A vehicle charging apparatus, wherein the control unit detects a power loss of the step-down DC-DC converter. Means, an input voltage detecting means, and increasing the output current within a range where the power loss does not exceed the maximum value by controlling a duty ratio of the switching element after the power loss reaches a predetermined maximum value. And an output current control means for permitting the charging. 6. The vehicle charging apparatus according to claim 5, wherein the control means controls the output voltage of the step-down DC-DC converter to a predetermined rated value within a range where the power loss does not exceed the maximum value. A charging device for a vehicle, comprising: