JP5375730B2 - Power circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-loss and high-efficient power circuit with high reliability that is capable of attaining structural miniaturization and cost reduction. <P>SOLUTION: The power circuit includes a control circuit 210 that outputs a voltage of a battery 100 or a voltage obtained by boosting the voltage of the battery 100, by controlling drive circuits 206, 207 and driving MOSFETs 204, 205. The control circuit 210, when a detection circuit 209 detects some failure in the drive circuit 207, controls the drive circuits 206, 208 and drives the MOSFETs 204, 205 to output a voltage of the battery 100 or a voltage obtained by boosting the voltage of the battery 100. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a power supply circuit that maintains supply of a necessary voltage to an electrical component even when the voltage of a battery temporarily decreases.

  In recent years, idle stop vehicles have been put into practical use for the purpose of reducing fuel consumption and reducing exhaust gas. The idle stop vehicle is a vehicle that automatically stops the engine when it detects a stop of the vehicle, such as waiting for a signal, and then automatically restarts the engine when it detects a start operation of the vehicle.

  In such a vehicle, when the engine is restarted, a large current flows through the starter motor for starting the engine, so that the battery voltage temporarily decreases. Along with this, the voltage supplied to the electrical components in the vehicle also temporarily decreases. For this reason, depending on the electrical component, the supplied voltage may be out of the operating range and may not temporarily operate normally. For example, a driver's unintended operation such as resetting may be performed in car navigation or audio, or sound skipping may occur in audio. Therefore, the idle stop vehicle is provided with an auxiliary power supply circuit so that the supply of a necessary voltage to the electrical component can be maintained even when the voltage of the battery temporarily decreases.

Examples of the auxiliary power circuit provided in the idle stop vehicle include the following.
1. A capacitor is provided, and the voltage is maintained by the electric charge accumulated in it.
2. By providing a relay and turning it on and off, a voltage supply by normal bypass (short circuit) and a voltage supply by a booster circuit at the time of engine restart are switched (for example, see Patent Document 1).
3. A booster circuit is provided, and an output voltage is controlled by controlling a switching element in the booster circuit (see, for example, Patent Document 2).

JP-A-2005-112250 JP 2005-237149 A

However, the above auxiliary power circuit has the following problems.
Above 1. In the case of this circuit, a large capacitor is required depending on the power consumption of the electric load, which causes an increase in cost. In addition, since the time for maintaining the voltage is determined by the capacity of the capacitor used, the time cannot be controlled.

  2. In the case of this circuit, since a relay is required, it becomes a factor of increase in size and cost. Considering the number of engine restarts in actual use, the life of the relay becomes a problem.

  3. above. In the case of this circuit, when a current always flows through a rectifying diode provided in the booster circuit, a decrease in efficiency due to loss in the diode and heat dissipation of the diode become problems.

  In view of the above circumstances, an object of the present invention is to provide a low-loss and high-efficiency power supply circuit that can be reduced in size and cost and has high reliability.

  A power supply circuit according to a first aspect of the present invention includes a DC power supply, a first switching element, an inductor provided between the DC power supply and the first switching element, and the inductor and an electrical load. A second switching element provided in between; a diode connected in parallel to the second switching element; first to third driving means; a detecting means for detecting an abnormality of the second driving means; Controlling the first and second driving means to drive the first and second switching elements to output a voltage of the DC power supply or a voltage obtained by boosting the voltage of the DC power supply; And the control means controls the first and third driving means to control the first and second switching elements when an abnormality of the second driving means is detected by the detecting means. By driving, the voltage of the DC power source or the voltage obtained by boosting the voltage of the DC power source is output. Such a configuration eliminates the need for large capacitors and relays, so that it is possible to provide a power supply circuit that can be reduced in size and cost. Further, the current does not always flow through the diode, and when the abnormality of the second driving unit is detected, the first and third switching units are controlled to operate the first and second switching elements. Thus, a highly reliable power supply circuit with low loss and high efficiency can be provided.

  The power supply circuit according to a second aspect of the present invention is the power supply circuit according to the first aspect, wherein the control means controls the first driving means to turn on the first switching element. Controlling the driving means to turn off the second switching element, and controlling the first driving means to turn off the first switching element controls the second driving means to control the second switching element. By turning on the switching element, the voltage of the DC power supply is boosted, and when the detection means detects an abnormality of the second drive means, the first drive means is controlled to control the first drive means. When the first switching element is turned on, the third driving means is controlled to turn off the second switching element, and the first driving means is controlled to turn off the first switching element. The third The voltage of the DC power supply is boosted by controlling the driving means to turn on the second switching element. As a result, when an abnormality of the second drive means is detected, the voltage of the DC power supply can be boosted using the third drive means instead of the second drive means.

  In the power supply circuit according to a third aspect of the present invention, in the first or second aspect, the detection means detects an abnormality of the second drive means based on an output of the second drive means. . Thereby, abnormality of the 2nd drive means can be detected based on the output of the 2nd drive means.

  In the power supply circuit according to a fourth aspect of the present invention, in the first or second aspect, the detection means detects an abnormality of the second drive means based on the temperature around the second switching element. To do. As a result, the abnormality of the second driving means can be detected based on the ambient temperature of the second switching element.

  According to the present invention, a physique can be reduced in size and cost, and a highly reliable power supply circuit with low loss and high efficiency can be realized.

It is a figure which shows the structure of the power supply circuit which concerns on one embodiment. It is a figure which shows the structure of the power supply circuit which concerns on a modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A power supply circuit according to an embodiment of the present invention is a power supply circuit for idle stop mounted on an idle stop vehicle.

FIG. 1 is a diagram illustrating a configuration of a power supply circuit according to the present embodiment.
As shown in the figure, the power supply circuit according to the present embodiment includes a battery 100 and a synchronous rectification type booster circuit 200. The voltage of the battery 100 or a voltage obtained by boosting the voltage by the booster circuit 200 is electrically Output to the load 300. Here, the battery 100 is an example of a DC power source.

  Boost circuit 200 includes capacitors 201 and 202, inductor 203, MOSFETs 204 and 205, drive circuits 206, 207 and 208, detection circuit 209, and control circuit 210. Here, the MOSFET 204 is an example of a first switching element, and the MOSFET 205 is an example of a second switching element in which diodes are connected in parallel. The drive circuits 206, 207, and 208 are examples of first to third driving units. The detection circuit 209 is an example of detection means, and the control circuit 210 is an example of control means.

  The capacitor 201 is connected in parallel to the battery 100, and one terminal of the capacitor 201 is connected to one terminal of the inductor 203. The other terminal of the capacitor 201 is connected to the source terminal of the MOSFET 204 and one terminal of the capacitor 202. The other terminal of the inductor 203 is connected to the drain terminal of the MOSFET 204 and the source terminal of the MOSFET 205. The drain terminal of the MOSFET 205 is connected to the other terminal of the capacitor 202.

  The drive circuit 206 outputs a drive voltage for turning on or off the MOSFET 204 to the gate terminal of the MOSFET 204 in accordance with a control signal from the control circuit 210. The drive circuits 207 and 208 are drive circuits configured in a dual system for fail-safe, each of which is a drive voltage for turning on or off the MOSFET 205 in accordance with a control signal from the control circuit 210. Is output to the gate terminal of the MOSFET 205.

  The detection circuit 209 detects an abnormality of the drive circuit 207 based on the output of the drive circuit 207, and outputs an abnormality detection signal when the abnormality is detected. For example, the detection circuit 209 detects an abnormality in the drive circuit 207 when the drive voltage output from the drive circuit 207 is different from the drive voltage output from the drive circuit 207 in a normal state.

  The control circuit 210 controls the drive circuits 206, 207 and 208 based on the output signal of the detection circuit 209. Specifically, when the detection circuit 209 does not output an abnormality detection signal, the control circuit 210 outputs a control signal to each of the drive circuits 206 and 207 to turn each of the MOSFETs 204 and 205 on or off. However, at this time, a control signal for stopping the operation is output to the drive circuit 208. On the other hand, when the detection circuit 209 outputs an abnormality detection signal, a control signal is output to each of the drive circuits 206 and 208 to turn on or off each of the MOSFETs 204 and 205. However, at this time, a control signal for stopping the operation is output to the drive circuit 207. Such an operation of the control circuit 210 can be realized by software or hardware. When realized by software, the control circuit 210 includes a CPU and a memory, and is realized by the CPU reading and executing a control program stored in the memory.

  The electrical load 300 is a general term for electrical components for which it is desired that the supply voltage does not deviate from the operating range even when the voltage of the battery 100 is temporarily reduced. For example, car navigation, audio, etc. In this way, electrical components are included that cause the driver to feel remarkably discomfort when the normal operation temporarily stops as the supply voltage temporarily decreases.

  Next, as the operation of the power supply circuit according to the present embodiment, the normal operation in which the voltage of the battery 100 does not temporarily decrease and the engine start (including the engine restart) in which the voltage of the battery 100 temporarily decreases are included. ) Will be described.

  The engine start operation is output from a host ECU (not shown) that controls the entire system of the idle stop vehicle when an engine start operation (including engine restart operation) by the driver is detected during normal operation. The control circuit 210 receives the control signal for starting the operation at the time of starting the engine. Further, the operation at the time of starting the engine is ended when the control circuit 210 receives a control signal output from a host ECU (not shown) for detecting the start of the engine to shift to the normal operation. It is.

First, the normal operation will be described.
In this operation, the control circuit 210 controls the drive circuit 206 to turn off the MOSFET 204 and controls the drive circuit 207 to turn on the MOSFET 205. The drive circuit 208 is controlled to stop its operation. As a result, the voltage of the battery 100 is output to the electric load 300 as it is without being boosted by the booster circuit 200 during normal operation.

  In the normal state, even if the MOSFET 205 is turned off, it can be energized through the body diode 205a. However, when the MOSFET 205 is turned on, the voltage drop in the MOSFET 205 becomes smaller and the loss becomes smaller. Therefore, the MOSFET 205 is turned on.

  On the other hand, when the detection circuit 209 outputs an abnormality detection signal during the normal operation described above, the control circuit 210 controls the drive circuit 206 to turn off the MOSFET 204 and controls the drive circuit 208 to control the MOSFET 205. Turn it on. The drive circuit 207 is controlled to stop its operation.

  As a result, when the drive circuit 207 is damaged during the normal operation, for example, when the operation becomes abnormal, the MOSFET 205 is turned on by the drive circuit 208 instead of the drive circuit 207.

Next, the operation when starting the engine will be described.
In this operation, the control circuit 210 controls the drive circuit 206 to turn on the MOSFET 204 to control the drive circuit 207 to turn off the MOSFET 205, and controls the drive circuit 206 to turn off the MOSFET 204. The operation of controlling 207 to turn on the MOSFET 205 is repeated alternately. However, at this time, a dead time during which both MOSFETs 204 and 205 are both turned off is provided so that both MOSFETs are not turned on at the same time. The drive circuit 208 is controlled to stop its operation. Thereby, when the engine is started, the voltage of the battery 100 is boosted by the booster circuit 200, and the boosted voltage is output to the electric load 300.

  On the other hand, when the detection circuit 209 outputs an abnormality detection signal during the operation at the time of starting the engine, the operation at the time of starting the engine is the same as the operation at the time of starting the engine. Thus, even when the drive circuit 207 is abnormal and, for example, the MOSFET 205 cannot be turned on, it can operate through the body diode 205a and thus operates as a booster circuit. However, if this is left, the voltage drop in the MOSFET 205 becomes large and the loss increases, and the MOSFET 205 may be damaged in some cases. Therefore, this is prevented by performing the following operation as the operation when starting the engine after the next time.

  The control circuit 210 controls the drive circuit 206 when the MOSFET 204 is turned on to control the drive circuit 208 to turn off the MOSFET 205 and controls the drive circuit 206 to control the drive circuit 208 when the MOSFET 204 is turned off. The operation of turning on the MOSFET 205 is repeated alternately. However, also at this time, a dead time is provided in which both MOSFETs 204 and 205 are turned off so that both MOSFETs 204 and 205 are not turned on at the same time. The drive circuit 207 is controlled to stop its operation.

  As a result, when the drive circuit 207 is damaged during operation at the time of starting the engine, for example, when the operation becomes abnormal, the MOSFET 205 is replaced by the drive circuit 208 instead of the drive circuit 207 at the next engine start. It will be turned on or off.

  As described above, according to the power supply circuit according to the present embodiment, the low-loss and high-efficiency power supply circuit can be realized by including the synchronous rectification booster circuit 200. Further, by using a dual drive circuit for the MOSFET 205, a highly reliable power supply circuit can be realized. Furthermore, since a large capacitor or relay is not required, a power supply circuit that can be reduced in size and cost can be realized.

The power supply circuit according to this embodiment can be modified as follows.
For example, the detection circuit 209 can be configured to detect an abnormality of the drive circuit 207 based on the ambient temperature of the MOSFET 205 instead of detecting an abnormality of the drive circuit 207 based on the output of the drive circuit 207. .

FIG. 2 is a diagram showing the configuration of the power supply circuit configured as described above.
As shown in the figure, in this power supply circuit, a thermistor 211 is provided around the MOSFET 205, and the detection circuit 209 detects an abnormality of the drive circuit 207 based on the output of the thermistor 211 instead of the output of the drive circuit 207. This is different from the power supply circuit shown in FIG. In this power supply circuit, when the MOSFET 205 cannot be turned on due to an abnormality in the drive circuit 207, a current always flows through the body diode 205a of the MOSFET 205, and the temperature of the MOSFET 205 rises. When a signal corresponding to the ambient temperature of the MOSFET 205 at this time is output by the thermistor 211, the detection circuit 209 detects an abnormality of the drive circuit 207 and outputs an abnormality detection signal. Other configurations and operations are the same as those of the power supply circuit shown in FIG. Even with the power supply circuit having such a configuration, the same effect as that of the power supply circuit shown in FIG. 1 can be obtained.

  In this embodiment, an example in which the present invention is applied to an idle stop power supply circuit has been described. However, the present invention can also be applied to other power supply circuits including a synchronous rectification booster circuit.

  Further, in this embodiment, when the detection circuit 209 outputs an abnormality detection signal during the operation at the time of engine start, the boost operation is continued using the drive circuit 207 as the operation at the time of engine start, In the operation at the time of starting the engine after the next time, the boosting operation is performed using the drive circuit 208 instead of the drive circuit 207. For example, the detection circuit 209 outputs an abnormality detection signal during the operation at the time of engine start. In this case, the drive circuit 208 can be used instead of the drive circuit 207 to immediately perform a boost operation.

  Further, in this embodiment, when the detection circuit 209 outputs an abnormality detection signal during the operation at the time of engine start, the boost operation is continued using the drive circuit 207 as the operation at the time of engine start, In the subsequent normal operation, the drive circuit 208 can be used instead of the drive circuit 207 so that the MOSFET 205 is driven.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the scope of the present invention.

100 Battery 200 Booster circuit 201, 202 Capacitor 203, Inductor 204, 205 MOSFET
206, 207, 208 Drive circuit 209 Detection circuit 210 Control circuit 211 Thermistor 300 Electric load

Claims (4)

DC power supply,
A first switching element;
An inductor provided between the DC power supply and the first switching element;
A second switching element provided between the inductor and an electrical load;
A diode connected in parallel to the second switching element;
First to third driving means;
Detecting means for detecting an abnormality of the second driving means;
Control means for outputting the voltage of the DC power supply or the voltage obtained by boosting the voltage of the DC power supply by controlling the first and second driving means to drive the first and second switching elements;
With
The control means controls the first and third drive means to drive the first and second switching elements when the detection means detects an abnormality of the second drive means. The voltage of the DC power supply or the voltage obtained by boosting the voltage of the DC power supply is output.
A power supply circuit characterized by that. The control means includes
When the first switching unit is controlled to turn on the first switching element, the second driving unit is controlled to turn off the second switching element, thereby controlling the first driving unit. When the first switching element is turned off, the second driving means is controlled to turn on the second switching element, thereby boosting the voltage of the DC power supply,
When an abnormality of the second driving unit is detected by the detecting unit, the third driving unit is controlled when the first switching unit is turned on by controlling the first driving unit. When the second switching element is turned off and the first driving means is controlled to turn off the first switching element, the third driving means is controlled to turn on the second switching element. By boosting the voltage of the DC power supply,
The power supply circuit according to claim 1. The detecting means detects an abnormality of the second driving means based on an output of the second driving means;
The power supply circuit according to claim 1 or 2, The detecting means detects an abnormality of the second driving means based on an ambient temperature of the second switching element;
The power supply circuit according to claim 1 or 2,

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