JP2016092958A - Power supply circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit device capable of securing a charge amount needed for backup while achieving reduction in mounting area and cost reduction.SOLUTION: A power supply circuit device comprises: a first boosting circuit which converts an input voltage from a battery into a predetermined output voltage; a constant voltage circuit which intervenes between the battery and a backup capacitor; a switch which is interposed between the first boosting circuit and backup capacitor, and connects and disconnects them to and from each other; and a voltage detection part which detects the input voltage. The constant voltage circuit is so configured to convert the input voltage from the battery into the constant voltage lower than the withstand voltage of the backup capacitor and to apply the constant voltage to the backup capacitor. The voltage detection part stops the constant voltage circuit from operating, and also turns on the switch to supply electric charges accumulated in the backup capacitor to the first boosting circuit when the voltage across the battery drops to or below a predetermined threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply circuit device for generating an output voltage required for an input voltage from a battery.

  In recent years, demand for idling stop vehicles has been increasing. Along with this, there is a fail-safe request for battery voltage drop (cranking) and instantaneous interruption.

  For example, a power supply circuit device mounted on a vehicle operates to step down an output voltage to 5V with respect to an input voltage of 12V by a battery, and keeps the output voltage constant by boosting against cranking or instantaneous interruption. There is something that works to do. The power supply device described in Patent Document 1 has a step-up / step-down chopper circuit that steps down and outputs a voltage supplied from a high voltage battery, and boosts a voltage supplied from an auxiliary battery when the output voltage decreases. Output.

  Further, the booster circuit described in Patent Document 2 is used as a power source for an airbag for protecting an occupant. This booster circuit has a backup capacitor, and when the supply of power from the battery to the DC-DC converter is interrupted, power is supplied from the backup capacitor to the ignition device.

  In recent years, in a power supply circuit that steps down a voltage input from a battery via a step-up / step-down DC-DC converter, a power supply circuit is known in which a backup capacitor is provided on the input side of the step-up / step-down DC-DC converter. The backup capacitor supplies a voltage to the step-up / step-down DC-DC converter with charges accumulated in advance during cranking or instantaneous interruption. Thereby, the power supply circuit can maintain the supply of electric power to the load even during cranking or instantaneous interruption.

JP 2010-119257 A JP 2005-229713 A

  The backup capacitor is better as the amount of accumulated electric charge is larger in order to cope with the backup when the duration of the battery cranking or instantaneous interruption becomes longer.

  On the other hand, a surge such as a load dump pulse may occur in the input voltage from the battery, and the backup capacitor must have a withstand voltage margin corresponding to the surge.

  As described above, it is preferable that the backup capacitor has a large stored charge amount and can withstand a surge voltage.

  By the way, as described above, the maximum value of the breakdown voltage of the backup capacitor is set so as to correspond to a large voltage such as a load dump pulse. For this reason, the standard value of the input voltage is almost sufficiently smaller than the maximum value of the withstand voltage. In other words, from the viewpoint of charge accumulation, the performance of the backup capacitor cannot be fully utilized. In the conventional configuration, it is necessary to increase the number of backup capacitors in accordance with the required charge amount, which may increase the mounting area and cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power supply circuit device that can secure a charge amount necessary for backup while realizing a reduction in mounting area and cost reduction. And

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate a corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the invention. Not what you want.

  In order to achieve the above object, the present invention is a power supply circuit device that is provided between a battery (20) and a load and supplies a constant voltage to the load, and an input voltage (Vin) from the battery is set to a predetermined value. A first step-up / step-down circuit (11) that converts and stabilizes the output voltage (Vout) and a battery are connected in parallel to the first step-up / step-down circuit and mediate the battery and the backup capacitors (C1, C2). A constant voltage circuit (12) that is connected to the battery in parallel with the first step-up / step-down circuit, and is interposed between the input terminal of the first step-up / down circuit and the backup capacitor to turn on / off the mutual connection (13) and a voltage detector (14) for detecting the input voltage, and the constant voltage circuit converts the input voltage from the battery into a constant voltage less than the withstand voltage (Vw) of the backup capacitor and The voltage detection unit is configured to be applied to the up capacitor, and when the battery voltage falls below a predetermined threshold, the voltage detection unit disconnects the connection between the constant voltage circuit and the backup capacitor and turns on the switch to turn it into the backup capacitor. The accumulated charge is supplied to the input terminal of the first step-up / down circuit.

  According to this, the constant voltage circuit applies a constant voltage to the backup capacitor even when the voltage of the battery fluctuates. For this reason, by setting the output voltage of the constant voltage circuit to be substantially the same as the breakdown voltage (Vw) of the backup capacitor, the performance of the backup capacitor can be sufficiently exhibited.

  According to the present invention, when the battery voltage drops below a predetermined threshold value, for example, when the battery voltage drops to such an extent that even if the voltage is boosted by the first buck-boost circuit, the specified output voltage is not reached, the first The charge supply source to the step-up / step-down circuit is switched from the battery to the backup capacitor.

  For example, if the output voltage of the constant voltage circuit is set to be larger than the standard value of the output voltage of the battery, more charges can be stored compared to the conventional configuration. In other words, the number of backup capacitors can be reduced as compared with the conventional configuration.

  On the other hand, the output voltage of the constant voltage circuit may be set smaller than the standard value of the output voltage of the battery. Since the voltage applied to the backup capacitor is controlled to be constant by the constant voltage circuit, it is not necessary to cope with the load dump pulse. That is, the breakdown voltage of the backup capacitor can be made smaller than that of the conventional configuration. Therefore, a small capacitor can be used as the backup capacitor.

  As described above, when the present invention is adopted, the number of backup capacitors can be reduced or the size of the backup capacitor can be reduced, so that the amount of charge required for backup can be reduced while realizing a reduction in mounting area and cost reduction. Can be secured.

1 is a circuit diagram showing a schematic configuration of a power supply circuit device according to a first embodiment. It is a circuit diagram which shows the specific structure of a buck-boost circuit. It is a timing chart which shows operation | movement of a power supply circuit device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are given to the same or equivalent parts.

(First embodiment)
Initially, with reference to FIG. 1 and FIG. 2, schematic structure of the power supply circuit device which concerns on this embodiment is demonstrated.

  This power supply circuit device is applied to a power supply circuit of a body control ECU mounted on a vehicle, for example. As shown in FIG. 1, the power supply circuit device 10 includes a first step-up / step-down circuit 11, a second step-up / step-down circuit 12, a switch 13, and a voltage detection unit 14.

  The first step-up / step-down circuit 11 is a DC-DC converter that receives an input voltage Vin from the battery 20 via a rectifying diode Di and outputs an output voltage Vout. The first step-up / step-down circuit 11 is a generally known step-up / step-down DC-DC converter. For example, a four-switch type step-up / step-down DC-DC converter as shown in FIG. 2 can be adopted.

  The four-switch type step-up / step-down DC-DC converter has four switches SW1 to SW4, two capacitors C3 and C4, and one inductor L, as shown in FIG. 1 and 2 do not illustrate a control unit that controls the switches SW1 to SW4.

  The switch SW1, the inductor L, and the switch SW4 are connected in series from the input terminal to the output terminal in this order. The capacitor C3 is provided between a contact point between the input terminal and the switch SW1 and a reference potential (ground potential). The switch SW2 is provided between the contact point between the switch SW1 and the inductor L and the reference potential. The switch SW3 is provided between the contact point between the inductor L and the switch SW4 and the reference potential. The capacitor C4 is provided between the contact between the switch SW4 and the output terminal and the reference potential.

  In the step-down mode in which the output voltage is lower than the input voltage, the switch SW3 is turned off and the switch SW4 is turned on. Then, the switch SW1 and the switch SW2 are alternately turned on and off to perform the PWM operation. In this case, the capacitors C3 and C4 act as capacitance components of a well-known step-down regulator, and the inductor L acts as an inductance component.

  On the other hand, in the boost mode in which the output voltage is higher than the input voltage, the switch SW2 is turned off and the switch SW1 is turned on. Then, the switch SW3 and the switch SW4 are alternately turned on and off to perform the PWM operation. In this case, the capacitors C3 and C4 act as capacitance components of a well-known boosting regulator, and the inductor L acts as an inductance component.

  For example, when Vin> Vout, the first step-up / step-down circuit 11 operates in a step-down mode in which the input voltage Vin is stepped down to a specified output voltage Vout during normal driving when the battery 20 is not cranked or instantaneously interrupted. On the other hand, when the input voltage Vin decreases due to cranking, the operation is performed in the boost mode in which the input voltage Vin is boosted to the output voltage Vout.

  The second step-up / down circuit 12 corresponds to a constant voltage circuit in the claims, and is connected to the first step-up / down circuit 11 in parallel to the battery 20. The second step-up / step-down circuit 12 is also a generally known step-up / step-down DC-DC converter. For example, a four-switch type step-up / step-down DC-DC converter can be adopted as in the case of the first step-up / step-down circuit 11. . However, the capacitances of the capacitors C3 and C4 and the inductance of the inductor L are appropriately changed, and are not necessarily the same as those of the first step-up / step-down circuit 11.

  The second step-up / down circuit 12 has a battery 20 connected to its input terminal. Backup capacitors C1 and C2 are connected in parallel to the output terminal. The second step-up / down circuit 12 boosts or steps down the input voltage Vin from the battery 20 and applies it to the backup capacitors C1 and C2. In FIG. 1, two backup capacitors, one corresponding to the reference C1 and one corresponding to the reference C2, are illustrated as an example, but the number is not limited to two. Since the backup capacitors C1 and C2 are power supplies used for backup when the battery 20 is cranked or momentarily interrupted, it is possible to store electric charge that does not cause a significant decrease in the output voltage Vout during the expected duration of the instantaneous interruption. The number is determined.

  Hereinafter, the standard value of the voltage Vbat output from the battery 20 is referred to as Vtyp, and the maximum value including the load dump pulse voltage is referred to as Vmax. Also, it is referred to as the withstand voltage Vw of the backup capacitors C1 and C2. When there is no noise or other abnormality in the circuit or the like, the input voltage Vin to the first step-up / step-down circuit 11 is approximately equal to the standard value Vtyp of the voltage of the battery 20, and Vin≈Vtyp. On the other hand, when a load dump pulse or the like occurs, Vin≈Vmax, and when cranking or instantaneous interruption occurs, Vin≈0.

  Since the backup capacitors C1 and C2 are emergency power supplies when the battery 20 is cranked or momentarily interrupted, the voltage Vc generated by the charge accumulation in the backup capacitors C1 and C2 is the output voltage of the first step-up / down circuit 11. It is set to Vout or higher. Note that the voltage Vc in the present embodiment is set to be equal to or higher than the standard value Vtyp of the voltage of the battery 20. That is, it is selected so as to satisfy the relationship of Vtyp ≦ Vc <Vw. The second step-up / step-down circuit 12 acts as a constant voltage circuit that converts the input voltage Vin into a constant voltage Vc. Specifically, during normal driving in which there is no noise or other abnormality in the circuit or the like, the input voltage Vin (≈Vtyp) is boosted to the voltage Vc. On the other hand, when a load dump occurs, Vin (≈Vmax) is lowered to the voltage Vc.

  The switch 13 is connected to the battery 20 in parallel with the first step-up / step-down circuit 11, and is interposed between the input terminal of the first step-up / down circuit 11 and the backup capacitors C 1, C 2. The switch 13 is turned on and off based on a signal from a voltage detector 14 described later. Although the switch 13 is off during normal driving, it is turned on when the voltage of the battery 20 drops below a predetermined threshold value, and the charge accumulated in the backup capacitors C1 and C2 is supplied to the first step-up / down circuit 11. It has become so.

  The voltage detector 14 detects that the input voltage Vin input from the battery 20 to the first step-up / step-down circuit 11 has dropped below a predetermined threshold value, and controls the second step-up / step-down circuit 12 and the switch 13. The voltage detection unit 14 in the present embodiment includes a comparator 14a and a reference power source 14b. A voltage obtained by dividing the input voltage Vin by resistors R1 and R2 is input to the comparator 14a, and the voltage is compared with the potential of the reference power supply 14b. The voltage detector 14 stops the operation of the second step-up / step-down circuit 12 and disconnects the backup capacitors C1 and C2 from the battery 20 when the resistance-divided voltage is equal to or lower than the potential of the reference power supply 14b. Further, the voltage detection unit 14 turns on the switch 13. The predetermined threshold value in the claims is defined by the potential of the reference power supply 14b in the present embodiment.

  As shown in FIG. 1, it is preferable to provide a smoothing capacitor C <b> 5 in parallel with the power supply circuit device 10 with respect to the battery 20. Thereby, the input voltage Vin to the power supply circuit device 10, and consequently the first step-up / step-down circuit 11 and the second step-up / step-down circuit 12, can be smoothed.

  Next, the operation of the power supply circuit device 10 according to the present embodiment will be described in time series with reference to FIG. In FIG. 3, the voltage of the battery 20 is denoted as Vbat, and the voltage immediately before being input to the first step-up / down circuit 11 is denoted as the input voltage Vin. In addition, the charge amount of the backup capacitors C1 and C2 is expressed as an inter-terminal potential between the positive electrode and the negative electrode.

  As an example, assume that the voltage output from the battery 20 is Vtyp≈12V and Vmax = 35V. Further, the voltage for driving the load is Vout = 5V. Further, the backup capacitors C1 and C2 have a withstand voltage Vw = 35V and a voltage applied during normal driving is Vc = 30V.

  As shown in FIG. 3, it is assumed that the power supply circuit device 10 is connected to the battery 20 at time t0. The input voltage Vin rises from 0V and reaches 12V. At this time, the switch 13 is turned off. After Vin reaches 12V, 12V of Vin is input to the second step-up / down circuit 12, and 30V defined as Vc is output. As a result, charges are accumulated in the backup capacitors C1 and C2 with a predetermined time constant, and the voltage between the terminals reaches Vc, that is, 30V. The output voltage Vout increases as Vin increases and reaches 5 V defined by the first step-up / step-down circuit 11.

  It is assumed that an instantaneous interruption has occurred in the battery 20 at time t1. The output from the battery 20 drops to 0V. Along with this, Vin starts to decrease. Vout is maintained at 5 V by the action of the first step-up / step-down circuit 11. At the stage of time t1, the switch 13 is off and the second step-up / step-down circuit 12 continues to operate.

  When the input voltage Vbat becomes equal to or lower than the threshold value at time t2, the voltage detection unit 14 stops the operation of the second step-up / down circuit 12 and disconnects the connection between the battery 20 and the backup capacitors C1 and C2. Then, the voltage detection unit 14 causes the switch 13 to transition from off to on. As a result, the charges accumulated in the backup capacitors C1 and C2 in the period before time t2 are supplied to the first step-up / down circuit 11. The input voltage Vin input to the first step-up / step-down circuit 11 behaves so as to gradually decrease due to the influence of discharge after rising to 30V. The output voltage Vout is maintained at 5 V by receiving the supply of charges from the backup capacitors C1 and C2.

  Assume that the instantaneous interruption of the battery 20 is completed at time t3. As described above, Vin gradually decreases from time t2 to time t3. On the other hand, since the switch 13 is in the ON state, the first buck-boost circuit 11 is supplied with electric charges from the backup capacitors C1 and C2, and Vout is maintained at about 5V. At time t3, the power supply circuit device 10 is connected to the battery 20 again, and Vbat starts to rise.

  When Vbat exceeds the threshold value at time t4, the voltage detection unit 14 causes the switch 13 to transition from ON to OFF, and further restarts the operation of the second step-up / down circuit 12. Thereby, Vout is maintained at 5 V by the action of the first step-up / step-down circuit 11 while receiving the charge supply from the battery 20. Further, since the backup capacitors C1, C2 are connected to the battery 20 via the second step-up / step-down circuit 12, charging of the backup capacitors C1, C2 is resumed.

  As described above, the instantaneous interruption of the battery 20 has been described as an example. However, the power supply circuit device 10 in the present embodiment performs the same operation even during cranking.

  Next, the effect of the power supply circuit device 10 according to the present embodiment will be described.

  By the way, in the backup capacitor in the conventional configuration, charges are accumulated by applying the standard value Vtyp of the voltage output from the battery 20 without passing through the second step-up / down circuit 12 in the present embodiment. Note that the withstand voltage Vw of the backup capacitor must correspond to the load dump pulse, so it is necessary to satisfy Vw≈Vmax. In the above example, the withstand voltage Vw of the backup capacitor is 35V, but the voltage Vc applied to the backup capacitor for charge accumulation is Vc = Vtyp = 12V.

  On the other hand, in the power supply circuit device 10 according to the present embodiment, the voltage supplied from the battery 20 to the backup capacitors C1 and C2 is boosted by the second step-up / down circuit 12. In the above example, Vc = 30V. For this reason, if the capacitance of the backup capacitor is the same between the conventional configuration and the present embodiment, the amount of charge accumulated in the backup capacitor is approximately doubled (more precisely, 30 / 12≈2.5 times). can do. In other words, the number of elements of the backup capacitor required to make the amount of electric charge accumulated as the entire backup capacitor equal to that of the conventional configuration can be reduced to approximately ½.

  As described above, when the power supply circuit device 10 according to the present embodiment is employed, it is possible to secure a charge amount necessary for backup while realizing a reduction in mounting area and cost reduction.

(Other embodiments)
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the above-described embodiment, the example in which the second step-up / step-down circuit 12 capable of both boosting and stepping down the output voltage with respect to the input voltage is used as the constant voltage circuit. However, if the withstand voltage Vw (= 35V) is equal to or higher than the maximum value Vmax (= 35V) of the voltage of the battery 20 as in the above-described embodiment, Vmax is applied to the backup capacitors C1 and C2. Even in this case, the backup capacitors C1 and C2 are unlikely to fail. Under such conditions, a step-up circuit that does not have a step-down mode can be adopted as the constant voltage circuit. However, since a capacitor having a large withstand voltage Vw may be disadvantageous in terms of cost, it is preferable to use a capacitor having a small withstand voltage Vw while satisfying Vtyp ≦ Vc <Vw.

  In the embodiment described above, the voltage Vc applied to the backup capacitors C1 and C2 is set to be larger than the standard value Vtyp of the voltage of the battery 20, but Vc is set to a voltage higher than the required Vout. It only has to be done. That is, it is not always necessary to satisfy Vtyp ≦ Vc. In the example shown in the first embodiment, Vc ≧ 5V may be set. For example, Vc = 6V may be set. In such an example, even if a load dump pulse is generated in the battery 20, the voltage is stepped down to Vc = 6V by the second step-up / down circuit 12. For this reason, the withstand voltage Vw of the backup capacitors C1 and C2 to be employed does not have to assume Vmax (= 35V), and can be suppressed to about Vc (= 6V). Thus, the withstand voltage Vw of the backup capacitors C1 and C2 is 35V in the conventional configuration, but if the above example is adopted, it can be suppressed to 6V. Therefore, the element size of the backup capacitors C1 and C2 As compared with the conventional case, a smaller one can be adopted.

  In addition, the switch 13 and the switches SW1 to SW4 included in the illustrated four-switch type step-up / step-down DC-DC converter preferably use semiconductor switching elements such as MOSFETs from the viewpoint of power consumption. Etc. can also be adopted.

  In the above-described embodiment, the voltage detection unit 14 has been described with respect to the configuration in which the input voltage Vin is compared with the threshold using the comparator 14a. However, the configuration is not limited thereto. The voltage detection unit 14 can detect the input voltage Vin, and when Vin becomes a predetermined threshold value or less, the operation of the constant voltage circuit (corresponding to the second step-up / down circuit 12 in the first embodiment) is stopped, It suffices if the switch 13 can be controlled to transition from OFF to ON.

  Further, the power supply circuit device 10 may be configured such that the first step-up / step-down circuit 11, the constant voltage circuit, the switch 13, and the voltage detection unit 14 each mount a separate element on an insulating substrate or the like. However, it is also possible to package the entire elements constituting them as one element. When the power supply circuit device 10 is packaged as a single element, the mounting can be facilitated as compared with the case where the power supply circuit device 10 is packaged separately.

DESCRIPTION OF SYMBOLS 10 ... Power supply circuit apparatus, 11 ... 1st buck-boost circuit, 12 ... Constant voltage circuit (2nd buck-boost circuit), 13 ... Switch, 14 ... Voltage detection part, 20 ...・ Battery, C1 ... Backup capacitor, C2 ... Backup capacitor

Claims (4)

A power supply circuit device provided between a battery (20) and a load for supplying a constant voltage to the load,
A first step-up / step-down circuit (11) for converting and stabilizing an input voltage (Vin) from the battery into a predetermined output voltage (Vout);
A constant voltage circuit (12) connected in parallel to the first step-up / step-down circuit for the battery and mediating the battery and a backup capacitor (C1, C2);
A switch (13) connected in parallel to the first step-up / step-down circuit with respect to the battery, and interposed between the input terminal of the first step-up / down circuit and the backup capacitor;
A voltage detector (14) for detecting the input voltage,
The constant voltage circuit is configured to convert an input voltage from the battery into a constant voltage lower than a withstand voltage (Vw) of the backup capacitor and apply the converted voltage to the backup capacitor,
The voltage detection unit disconnects the constant voltage circuit and the backup capacitor when the voltage of the battery drops below a predetermined threshold, and turns on the switch to store the charge accumulated in the backup capacitor. Is supplied to the input terminal of the first step-up / step-down circuit.   2. The power supply circuit device according to claim 1, wherein the constant voltage circuit converts an input voltage from the battery into a constant voltage equal to or higher than a standard value (Vtyp) of a voltage output from the battery.   The power supply circuit device according to claim 1, wherein the constant voltage circuit is a second step-up / step-down circuit capable of both step-up and step-down.   4. The device according to claim 1, wherein at least the first step-up / step-down circuit, the constant voltage circuit, the switch, and the voltage detection unit are packaged as one element. 5. Power supply circuit device.

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