JP5445192B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device suitable for use in a vehicle to which an idle stop system is applied.

In recent years, an increasing number of vehicles have applied an idle stop system that is expected to save fuel and reduce exhaust gas by stopping the engine.
In such an idle stop system, as the load on the electrical equipment connected to the in-vehicle battery increases, the potential of the output voltage of the in-vehicle battery greatly decreases when the engine is restarted. That is, the amount of decrease in the cranking potential is increased.
Further, the amount of decrease in the cranking potential when the engine is restarted tends to increase due to the aging of the in-vehicle battery.
When the cranking potential at the time of restarting the engine is lower than the reset potential of the electrical equipment of the vehicle, the electrical equipment is in a reset state.
In order to avoid such a reset state of the electrical equipment accompanying an increase in the amount of decrease in the cranking potential at the time of restarting the engine, a DC / DC converter is used as a power supply auxiliary device.
This DC / DC converter feeds back and monitors its own output, changes the amount of energy stored in the capacitor according to the magnitude of the load, controls the booster so that the output is always constant, The output is corrected.
The correction capability is required to be able to correct the largest drop amount of the cranking potential generated during cranking.
As a power supply device using such a DC / DC converter, a device as shown in Patent Document 1 has been proposed.
That is, this power supply device performs control including the following steps.
The stage of judging the current operation mode at the next key-off input.
When the current operation mode is the fuel cell mode, a step of switching the low voltage DC / DC converter connected to the auxiliary battery to the boost mode.
The voltage supplied from the auxiliary battery and boosted by the low voltage DC / DC converter is supplied to the single high voltage product, and the driving state of the single high voltage product is maintained.
Powering off the fuel cell stack by turning off the stack PDU;
A step of transmitting a stop command for ending the operation of the fuel cell to the fuel cell control device to turn off the single high-voltage product and simultaneously end the operation of the fuel cell.
Turning off the low voltage DC / DC converter;

JP 2008-148541 A

Therefore, in the conventional power supply device, a larger output is required as the load increases.
In-vehicle batteries are also deteriorated due to aging and become a fluctuation factor of voltage drop at the time of cranking.
For this reason, the DC / DC converter used in the power supply apparatus is required to have a larger output and performance in order to cope with the increase in load and the deterioration due to the aging of the in-vehicle battery.
Regarding the increase in the output of the DC / DC converter, due to the characteristics of the circuit of the DC / DC converter, especially in the case of a step-up DC / DC converter using a choke coil, a large coil and capacitor are required, and the size is increased. There was a problem that it would end up.
In addition, the improvement of the performance of the DC / DC converter is also required to have a problem such as generation of noise and heat generation because the switching speed is required to be increased.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power supply device that can suppress generation of noise, heat generation, and the like and can be reduced in size.

The invention according to claim 1 is a power supply device that is interposed between a battery and a load and corrects a variation in an output voltage applied to the load, wherein a target value of the output voltage applied to the load is A set target value setting means, a current value detecting means for detecting the output voltage applied to the load as a current value, and calculating a deviation amount between the set target value and the detected current value A deviation amount determining means for determining whether the deviation amount calculated by the calculation means is within a predetermined range, and the deviation amount is determined by the deviation amount determination means. When it is determined that the output value exceeds the predetermined range, the output voltage target value set in the target value setting means is reset so that the deviation amount falls within the predetermined range. low in the range of not less than the potential A target value control means for changing such that, on the basis of the deviation amount calculated from the arithmetic unit, wherein as a difference between the target value of the output voltage and the output voltage applied to the load is reduced Output voltage control means for controlling the output voltage.

According to the present invention, it is possible to reduce the target value of the output voltage applied to the load, so that generation of noise and heat generation of the power supply device itself can be suppressed and the size can be reduced.
Therefore, there is an effect that it is possible to provide a power supply device that can alleviate mechanical restrictions such as a space that must be secured as a mounting place, and mounting restrictions that prevent noise and heat generation from adversely affecting other electrical devices. .

It is a circuit diagram which shows the structure of the power supply device which is embodiment of this invention. It is a block diagram which shows the structure of the DC / DC converter used for the power supply device of embodiment of this invention. It is a flowchart which shows operation | movement of the DC / DC converter used for the power supply device of embodiment of this invention. It is explanatory drawing which shows the voltage drop amount of cranking potential when the power supply device of embodiment of this invention is used for the vehicle to which an idle stop system is applied, and electric potential Vout of the output terminal of a DC / DC converter.

Embodiments of the present invention will be described below. FIG. 1 is a circuit diagram showing the configuration of the power supply device of this embodiment.
In this embodiment, the case of restarting the engine in which the amount of voltage drop of the cranking potential increases when this power supply apparatus is used in a vehicle to which an idle stop system is applied will be described as an example.
The power supply device includes a DC / DC converter 1 and a battery 2, and supplies direct current power output from the battery 2 to the load 10 via the DC / DC converter 1.
The DC / DC converter 1 includes a choke coil 3, a diode 4, an N-channel MOS transistor 5, an output capacitor 6, a control circuit 7, an input terminal 8 and an output terminal 9.
The positive terminal of the battery 2 is connected to the input terminal 8 of the DC / DC converter 1.
An input terminal 8 of the DC / DC converter 1 is connected to one end of the choke coil 3.
The other end of the choke coil 3 is connected to the anode terminal of the diode 4 and the drain terminal of the N-channel MOS transistor 5.
The source terminal of the N channel MOS transistor 5 is grounded, and the gate terminal is connected to the control signal output terminal of the control circuit 7.
The cathode terminal of the diode 4 is connected to the positive terminal of the output capacitor 6 and to the output terminal 9 of the DC / DC converter 1.
The output terminal 9 of the DC / DC converter 1 is connected to the power supply line of the load 10.
The control circuit 7 is configured by, for example, an A / D converter, an analog circuit including a D / A converter, a logic circuit, a microcomputer, a DSP (Digital Signal Processor), or the like.
The output terminal 9 of the DC / DC converter 1 is connected to the feedback input terminal of the control circuit 7, and the potential of the output terminal 9 of the DC / DC converter 1 is fed back to the control circuit 7. .

FIG. 2 is a block diagram showing the configuration of the DC / DC converter 1 used in the power supply device of this embodiment.
The DC / DC converter 1 includes a target value setting unit 21, a calculation unit 22, a deviation amount determination unit 23, an operation amount calculation unit 24, an operation amount output unit 25, a boosting unit 26, a DC / DC converter output unit 27, and a current value detection. Means 28 and target value control means 29 are provided.
Each functional block of the target value setting means 21, the calculation unit 22, the deviation amount determination means 23, the operation amount calculation means 24, the operation amount output means 25, the current value detection means 28 and the target value control means 29 is configured by the control circuit 7. ing.

Booster 26 corresponds to choke coil 3 and N-channel MOS transistor 5 of DC / DC converter 1 shown in FIG.
The DC / DC converter output means 27 corresponds to the diode 4 and the output capacitor 6 of the DC / DC converter 1 shown in FIG.

The DC / DC converter 1 is configured so that the potential of the target output terminal 9 can be varied. The target potential of the output terminal 9 is set in the target value setting means 21 as a target value.
The DC / DC converter 1 feeds back the potential of the output terminal 9 to control the boosting element of the boosting unit 26 and the choke coil 3. That is, the deviation between the current potential of the output terminal 9 and the target value, which is the target potential of the output terminal 9, is always monitored so that the deviation between the current potential of the output terminal 9 and the target value is eliminated. The choke coil 3 is controlled.
In this embodiment, the DC / DC converter 1 has a large influence of the load 10 including the electrical equipment when the engine restarts when the voltage drop amount of the cranking potential increases, the control of the choke coil 3 is not in time, and the output terminal When the voltage drop of 9 becomes large and the deviation from the target value exceeds a certain range, the target value is lowered within a range where the load 10 including the electrical equipment is not reset, and the potential of the current output terminal 9 is reduced. And the choke coil 3 are controlled so that there is no deviation from the target value.

  In the target value setting means 21, the target potential of the output terminal 9 of the DC / DC converter 1 is set as the target value. This target value can be set, for example, as digital data in a predetermined register, or as a divided voltage value of a resistance circuit.

  The calculation unit 22 calculates a deviation between the target value set in the target value setting means 21 and the current potential of the output terminal 9 detected and fed back as the current value by the current value detection means 28.

  The deviation amount determination means 23 is a predetermined amount in which a deviation between the target value calculated by the calculation unit 22 and the fed back potential of the current output terminal 9 as the current value is defined by an upper limit value and a lower limit value. It is determined whether it is within the specified range.

  When the deviation between the target value and the fed back potential of the current output terminal 9 is within a predetermined range defined by the upper limit value and the lower limit value, the operation amount calculation means 24 An operation amount for making the potential of the terminal 9 coincide with the target value is calculated.

The manipulated variable output means 25 outputs the manipulated variable calculated by the manipulated variable calculating means 24 to the N-channel MOS transistor 5 of the booster.
This manipulated variable is defined as the duty ratio of the control signal output from the control signal output terminal of the control circuit 7 to the gate terminal of the N-channel MOS transistor 5, and changes the switching frequency of the N-channel MOS transistor 5.

In the booster 26, the N-channel MOS transistor 5 is turned on / off at the switching frequency.
Then, energy is accumulated in the choke coil 3 by the current flowing through the choke coil 3 while the N-channel MOS transistor 5 is on, and the accumulated energy is released when the N-channel MOS transistor 5 is off.
This released energy is added to the DC voltage Vin input from the battery 2 to the input terminal 8 and charged to the output capacitor 6 via the diode 4.

  The DC / DC converter output means 27 supplies the energy charged to the output capacitor 6 via the diode 4 from the output terminal 9 to the load 10 as the DC / DC converter output.

  The current value detection means 28 detects the current DC / DC converter output voltage output to the output terminal 9 as a current value, and feeds it back to the calculation unit 22 of the control circuit 7.

  The target value control means 29 calculates the difference between the target value and the current value detected by the current value detection means 28 in the deviation amount determination means 23, that is, the current DC / DC converter output voltage output to the output terminal 9. When it is determined that the deviation amount exceeds a predetermined range defined by the upper limit value and the lower limit value, the deviation value is determined as the target value set in the target value setting means 21. In order to fall within the specified range, the load 10 including the electrical equipment is lowered stepwise with a predetermined level width within a range where reset of the load 10 does not occur. Then, the choke coil 3 of the boosting unit 26 is controlled so that the deviation between the current DC / DC converter output voltage output to the output terminal 9 and the target value lowered by the predetermined level width becomes small.

FIG. 3 is a flowchart showing the operation of the DC / DC converter 1 used in the power supply device of this embodiment.
FIG. 4 shows the voltage drop amount of the cranking potential at the time of engine restart and the potential Vout of the output terminal 9 of the DC / DC converter 1 when the power supply device of this embodiment is used for a vehicle to which the idle stop system is applied. It is explanatory drawing shown.
The operation of the power supply device according to this embodiment will be described below with reference to the flowchart of FIG.

First, the vehicle to which the power supply device is applied is in a state where the engine is stopped by the idle stop system. For this reason, the battery is in a state of supplying power to the load 10 including the electrical equipment.
At this time, if sufficient power supply capability is maintained for the battery 2, the voltage drop of the potential Vout of the output terminal 9 of the DC / DC converter 1 is small, and the current potential Vout of the output terminal 9 and the target value Vo The deviation amount Vd1 maintains a state within a predetermined range defined by an upper limit value and a lower limit value.
Further, the control circuit 7 is in a state where the target value Vo is set in the target value setting means 21. This target value Vo is an initial value set to the target value setting means 21 by the control circuit 7 as the potential of the output terminal 9 of the DC / DC converter 1.

In this state, the idle stop system is released and the engine is started.
The control circuit 7 detects the current potential Vout of the output terminal 9 by the current value detecting means 28 and calculates the deviation amount Vd1 between the detected potential Vout of the current output terminal 9 and the target value Vo by the calculation unit 22. (Step S1).
Further, the deviation amount determining means 23 determines whether or not the deviation amount Vd1 is within a predetermined range defined by the upper limit value and the lower limit value (step S2).
When the idle stop system is released and the engine is started, the battery is in a state of supplying power to a starter unit (not shown) and a load 10 including electrical equipment.
If sufficient power supply capability is maintained for the battery 2 at this time, the voltage drop amount of the potential Vout of the output terminal 9 is due to the capability of the DC / DC converter 1 that controls the potential of the output terminal 9 with the target value Vo. The deviation amount Vd1 between the current potential Vout of the output terminal 9 detected by the current value detection means 28 and the target value Vo is small and falls within a predetermined range defined by the upper limit value and the lower limit value. The cranking potential waveform at this time is shown by (1) in FIG.
When the deviation amount determination means 23 determines that the deviation amount Vd1 is within the range defined in advance by the upper limit value and the lower limit value, the operation amount calculation means 24 of the control circuit 7 operates so as to make the deviation amount Vd1 zero. The amount is calculated (step S3).
Then, the calculated operation amount is output to the gate terminal of the N-channel MOS transistor 5 of the boosting unit 26 as, for example, a PWM signal (step S4).
The N-channel MOS transistor 5 is turned on / off according to the operation amount, compensates for the voltage drop amount of the potential Vout of the output terminal 9 of the DC / DC converter 1, and sets the deviation amount Vd1 to zero (step S5). .

On the other hand, the DC / DC converter that controls the potential of the output terminal 9 with the target value Vo when sufficient power supply capability is not maintained for the battery 2 in step S2 or the load of the electrical equipment is increased. 1 ability is not enough. As a result, the voltage drop amount of the potential Vout of the output terminal 9 increases, and the deviation amount Vd2 between the current potential Vout of the output terminal 9 detected by the current value detection means 28 and the target value Vo is the upper limit value and the lower limit value. It exceeds the range specified in advance. A cranking potential waveform that is a voltage drop amount of the potential Vout of the output terminal 9 of the DC / DC converter 1 at this time is shown by (2) in FIG.
When the deviation amount determining means 23 determines that the deviation amount Vd2 between the current potential Vout of the output terminal 9 and the target value Vo exceeds the range defined in advance by the upper limit value and the lower limit value, the target value control means. 29 lowers the target value of the target value to the level of the electric load 10 is lowered target value to a minimum level V _R of a range not reset, or electrical load 10 reset not range at a constant level width v, i.e. Vo-v (Step S6).

Then, to calculate the deviation Vd2 between the potential Vout and the target value Vo-v of deviation Vd2 or output terminal 9 of the electric potential Vout and the target value _{V R} of the output terminal 9 in the arithmetic unit 22 (step S7).
The operation amount calculation means 24 of the control circuit 7 calculates the operation amount so that the deviation amount Vd2 becomes zero (step S8), and the calculated operation amount is used as the PWM signal, for example, of the N-channel MOS transistor 5 of the boosting unit 26. Output to the gate terminal (step S4).
The N-channel MOS transistor 5 is turned on / off according to the operation amount, and compensates for the voltage drop amount of the potential Vout of the output terminal 9 so that the deviation amount Vd2 becomes small (step S5).

  Although the electrical load is large and the target value is lowered to the level of Vo-v in step S6, the deviation amount Vd2 between the potential Vout of the output terminal 9 and the target value Vo-v is the above-mentioned in step S2 of the next cycle If the upper limit value and the lower limit value exceed the predetermined range, the target value is further lowered to a certain width v, that is, Vo-2v level within a range where the electrical load 10 does not reset the target value (step S6). .

As described above, according to this embodiment, deviation Vd2 or the potential of the output terminal 9, the potential Vout and the target value V _R of the output terminal 9 when the DC / DC converter 1 operates It is determined whether or not the deviation amount Vd2 between Vout and the target value Vo−v exceeds a range defined in advance by the upper limit value and the lower limit value. If the deviation amount Vd2 does not exceed the range, the target value is changed. Configured not to.
Also, if the deviation Vd2 exceeds a predefined range between the upper limit value and the lower limit value, decrease the target value to a minimum level V _R range to the target value electrical load 10 is not reset, or electrical load 10 resets In this range, the target value is decreased for each constant level width v.
The relationship between the output Vout and the output Iout of the DC / DC converter 1 that can vary the potential Vout of the output terminal 9 is inversely proportional to each other. In other words, since Iout = C / Vout, the target value of the DC / DC converter 1 is lowered and the output Vout is set to a low output V′out within the variable range. To increase. Therefore, the target value is lowered within the range where the electrical load 10 is not reset, and the output Vout of the DC / DC converter 1 is set to the low output V′out within the variable range, thereby increasing the maximum value of the output Iout accordingly. In addition, the compensation capability of the DC / DC converter with respect to load fluctuations can be improved.
Further, from the viewpoint of making the DC / DC converter itself compact, the choke coil 3 and the output capacitor 6 are required to be small. For this reason, when the fluctuation range of the electrical load 10 is small, the target value is lowered within a range where the electrical load 10 is not reset, and the output Vout of the DC / DC converter 1 is set to the low output V′out within the variable range. Since the Vout is set to the low output V′out, the DC / DC converter 1 having a small output can be used. As a result, the inductance value of the choke coil 3 and the capacitance value of the output capacitor 6 can be reduced, and the DC / DC converter itself can be reduced in size.

In the embodiment described above, the deviation amount between the target value and the current DC / DC converter output voltage output to the output terminal 9 detected by the current value detection unit 28 in the deviation amount determination unit 23 is the upper limit. If it is determined that a predetermined range defined by the value and the lower limit value is exceeded, the target value set in the target value setting means 21 is set so that the deviation amount falls within the predetermined range. The load 10 including the electrical equipment is configured to be lowered step by step with a predetermined level width within a range where the reset of the load 10 does not occur. Then, the choke coil 3 of the booster 26 is controlled so that the deviation between the current DC / DC converter output voltage output to the output terminal 9 and the target value lowered by the predetermined level width is reduced. I made it.
On the other hand, the rate of change of the voltage drop amount of the potential Vout of the output terminal 9 of the DC / DC converter 1 when the engine is restarted is detected, and the detected rate of change is a range defined in advance by an upper limit value and a lower limit value. If it is within the range, the target value is not changed, and if the detected rate of change exceeds the range, the target value is decreased by a certain amount to the minimum value in the range where the electrical load 10 is not reset, or the detected rate of change is It is also possible to read out a target value according to the above from a data table defined in advance and set it as the target value of the DC / DC converter.
Even in such a configuration, the target value is lowered within a range in which the electrical load 10 is not reset, and the output Vout of the DC / DC converter 1 is set to a low output V′out within the variable range. The maximum value of the output Iout can be increased, and the compensation capability of the DC / DC converter against load fluctuation can be improved.
Also, the output Vout is set to the low output V′out by setting the output value Vout of the DC / DC converter 1 to the low output V′out within the variable range by reducing the target value within the range where the electrical load 10 does not reset. Accordingly, the DC / DC converter 1 having a small output can be used. As a result, the inductance value of the choke coil 3 and the capacitance value of the output capacitor 6 can be reduced, and the DC / DC converter itself can be reduced in size.

  DESCRIPTION OF SYMBOLS 1 ... DC / DC converter, 2 ... Battery, 7 ... Control circuit, 10 ... Load, 21 ... Target value setting means, 22 ... Calculation means, 23 ... Deviation amount determination means, 24 ... Operation Amount calculation means (output voltage control means), 25... Manipulated variable output means (output voltage control means), 26... Booster (output voltage control means), 27... DC / DC converter output means (output voltage control means) ) 28... Current value detection means 29... Target value control means.

Claims (3)

A power supply device that intervenes between a battery and a load and corrects fluctuations in an output voltage applied to the load,
Target value setting means for setting a target value of the output voltage applied to the load;
Current value detection means for detecting an output voltage applied to the load as a current value;
A calculating means for calculating a deviation amount between the set target value and the detected current value;
Deviation amount determination means for determining whether or not the deviation amount calculated by the calculation means is within a predetermined range;
If it is determined by the deviation amount determination means that the deviation amount exceeds the predetermined range, the deviation amount is set in the target value setting means so that the deviation amount falls within the predetermined range. A target value control means for changing the target value of the output voltage so as to be low within a range not lower than the reset potential of the load;
Output voltage control means for controlling the output voltage so that the difference between the output voltage applied to the load and the target value of the output voltage is reduced based on the deviation calculated by the calculation means;
A power supply device comprising:   The change of the target value of the output voltage by the target value control means is performed by lowering the target value of the output voltage set in the target value setting means stepwise at a predetermined voltage level. The power supply device according to claim 1.   The output voltage control means includes a choke coil and a switching element for controlling a current flowing through the choke coil so that a difference between an output voltage applied to the load and a target value of the output voltage is reduced. The power supply apparatus according to claim 1, wherein the output voltage is controlled by turning on / off the switching element.

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