JP2010022077A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device wherein a back flow of current can be prevented even when the current is low. <P>SOLUTION: The power supply device includes: a synchronous rectification step-up DC-DC converter 13; a main power supply 18 electrically connected to the input terminal 17 of the DC-DC converter 13 through a switch 15; a diode 19 whose cathode is electrically connected to the input terminal 17 and whose anode is electrically connected to the main power supply 18; and a control circuit 35 electrically connected to the DC-DC converter 13 and the switch 15. The control circuit 35 starts the DC-DC converter 13 by synchronous rectification with the switch 15 off. When back flow current does not flow from the output terminal 29 to the input terminal 17 of the DC-DC converter 13 anymore, the control circuit turns on the switch 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device using a DC / DC converter that converts a voltage.

  Conventionally, for example, Patent Document 1 proposes a DC / DC voltage converter that boosts and outputs a DC voltage as a power supply device for converting a power supply voltage into a voltage required by the device. FIG. 7 is a block circuit diagram of such a DC / DC voltage converter.

  In FIG. 7, the DC / DC voltage converter 101 has the following configuration. The power supply line 103 to which the power supply voltage Vdd is applied is connected to the booster circuit 105 of the DC / DC voltage converter 101. The booster circuit 105 is constituted by a series circuit of a coil 107 and an FET transistor 109, and this series circuit is connected between the power supply line 103 and the ground 111. The power supply line 103 is connected to the coil 107. A diode 113 is connected in parallel with the FET transistor 109.

  A gate circuit 117 is connected to the node 107 of the coil 107 and the FET transistor 109. The gate circuit 117 includes an FET transistor 119 and a diode 121 connected in parallel thereto. The output of the gate circuit 117 is connected to the output terminal 125 through the smoothing circuit 123.

  A control circuit for turning on and off the FET transistors 109 and 119 has the following configuration. The output of the sawtooth wave generation circuit 127 that is the basis for the on / off control is input to the soft start circuit 129 and the pulse width control circuit 131. Here, the soft start circuit 129 controls the pulse width to gradually increase in order to perform a stable initial operation. On the other hand, the pulse width control circuit 131 changes the output waveform of the sawtooth wave generation circuit 127 according to the voltage Vo of the output terminal 125. The outputs of the soft start circuit 129 and the pulse width control circuit 131 are input to an AND circuit 133, and the output is input to the gate of the FET transistor 109. As a result, the FET transistor 109 performs an on / off operation. Further, the output of the AND circuit 133 is input to the gate of the FET transistor 119 via the inverting circuit 135 and the step-up circuit 137. Here, the step-up circuit 137 is also connected to the soft start circuit 129, and performs an operation of turning off the FET transistor 119 during the soft start period for stabilizing the initial operation.

  Next, the initial operation of the DC / DC voltage converter 101 will be described with reference to FIG. 8A is a time-dependent change diagram in the output current Io of the gate circuit 117, FIG. 8B is a timing chart of the FET transistor 109, and FIG. 8C is a timing chart of the FET transistor 119. FIG. 8D shows a timing chart of the DC / DC voltage converter 101, respectively.

  First, from time t30 to t31, as shown in FIG. 8D, the operation of the DC / DC voltage converter 101 is off. Therefore, as shown in FIG. 8A, the output current Io is zero.

  Next, it is assumed that the operation of the DC / DC voltage converter 101 is turned on at time t31 as shown in FIG. Thereby, as shown in FIG. 8B, the FET transistor 109 starts an on / off operation. At this time, in order to perform a stable initial operation as described above, the soft start circuit 129 controls the pulse width to gradually increase. On the other hand, as shown in FIG. 8C, the FET transistor 119 is kept off by the step-up circuit 137. As a result, in the gate circuit 117, the diode 121 performs an on / off operation that is the reverse of the on / off operation of the FET transistor 109, and diode rectification is performed. If the current flowing from the power supply line 103 toward the output terminal 125 is defined as positive by such an operation, only the positive current flows through the output current Io as shown in FIG. Therefore, it is possible to realize the DC / DC voltage converter 101 in which the backflow of the output current Io does not occur. 8A represents the average value of the output current Io and corresponds to the output of the smoothing circuit 123.

  Next, when the initial operation period (soft start period) ends at time t32, the average value of the output current Io is stabilized as shown in FIG. Thereafter, as shown in FIG. 8C, the step-up circuit 137 starts on / off control of the FET transistor 119 at time t33 and performs synchronous rectification. At this time, as shown in FIG. 8A, the average value of the output current Io is already stable, so that the stable output current Io can be obtained even when switching from diode rectification to synchronous rectification. it can.

By using the DC / DC voltage converter 101 having such a configuration and operation, it is possible to prevent a backflow of current during the initial operation period.
Japanese Patent No. 3175227

  According to the DC / DC voltage converter described above, it is possible to surely prevent the backflow of the current during the initial operation period. However, if the average value of the output current Io is small, the diode after the end of the initial operation period. There was a problem that current may flow backward when switching from rectification to synchronous rectification. Details will be described with reference to FIG. 9A to 9D are the same as those in FIGS. 8A to 8D, respectively.

  First, from time t40 to t41, as shown in FIG. 9D, the operation of the DC / DC voltage converter 101 is off. Thereafter, it is assumed that the operation of the DC / DC voltage converter 101 is turned on at time t41. Thereby, as shown in FIG. 9B, the FET transistor 109 starts an on / off operation. Since the time t41 to t42 is an initial operation period, the pulse width is gradually increased by the soft start circuit 129. At this time, as shown in FIG. 9C, since the FET transistor 119 remains off, diode rectification is performed.

  Next, when the initial operation period ends at time t42, the average value (broken line) of the output current Io stabilizes as shown in FIG. 9A, but when the average value is small, the waveform of the output current Io (Solid line) is a state in which a negative current is cut by diode rectification.

  Thereafter, as shown in FIG. 9 (c), on / off control of the FET transistor 119 is started at time t43, and switched to synchronous rectification. As a result, as shown in FIG. 9A, since the negative current that has been cut until time t43 flows, the output current Io flows largely to the negative side. As a result, current reverse flow occurs when switching to synchronous rectification. Thereafter, as shown in FIGS. 9B and 9C, the output current Io is stabilized by changing the pulse width of the FET transistors 109 and 119 to the average value of the original output current Io. Turn into. Such behavior of the output current Io occurs because the pulse width cannot be changed immediately due to the limit of the responsiveness of the DC / DC voltage converter 101 when switching from diode rectification to synchronous rectification.

  With the above operation, in the conventional DC / DC voltage converter 101 (hereinafter referred to as DC / DC converter), when the average value of the output current Io is low and the current is switched from diode rectification to synchronous rectification, There was a problem that there was a possibility of backflow.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a power supply device that can suppress a backflow of current even at a low current.

  In order to solve the conventional problems, a power supply device of the present invention includes a synchronous rectification step-up DC / DC converter and a main unit electrically connected to an input side terminal of the DC / DC converter via a switch. A control circuit electrically connected to the power supply, a diode electrically connected to the input terminal and a cathode electrically connected to the main power supply, and an anode electrically connected to the DC / DC converter and the switch; The circuit starts the DC / DC converter by synchronous rectification with the switch turned off, and the reverse current does not flow from the output side terminal of the DC / DC converter to the input side terminal. The switch is turned on.

  According to the power supply device of the present invention, since the DC / DC converter is started by synchronous rectification from the beginning with the switch turned off, switching from diode rectification to synchronous rectification is unnecessary, and in parallel with the switch. The connected diode suppresses the reverse current flow at startup, and the switch is turned on when the reverse current does not flow from the output side terminal of the DC / DC converter to the input side terminal. Rectification is performed, and an effect that a power supply device capable of stable output even with a low current can be realized.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Here, an example will be described in which a power supply device is applied to a regenerative system for a vehicle in which regenerative power is charged in a power storage unit in a vehicle and discharged during non-regeneration.

(Embodiment 1)
FIG. 1 is a block circuit diagram of a power supply device according to Embodiment 1 of the present invention. 2A and 2B are current aging diagrams of the power supply device according to the first embodiment of the present invention, in which FIG. 2A is a chronological change diagram of the inductor current I, FIG. 2B is a timing chart of the first switching element, ) Shows a timing chart of the second switching element, (d) shows a timing chart of the switch, and (e) shows a timing chart of the DC / DC converter. In FIG. 1, thick lines indicate power system wiring, and thin lines indicate signal system wiring.

  In FIG. 1, the power supply device 11 includes a DC / DC converter 13 and a switch 15. The DC / DC converter 13 is electrically connected to a main power source 18 through the switch 15 at an input side terminal 17 thereof. Here, the main power source 18 is a vehicle battery.

  The switch 15 has a diode 19 in which a cathode is electrically connected to the input terminal 17 and an anode is electrically connected in parallel to the main power supply 18. In the first embodiment, the switch 15 is composed of a field effect transistor (hereinafter referred to as FET). Here, since a parasitic diode is formed between the source and the drain in the FET, the parasitic diode is used as the diode 19. This simplifies the circuit configuration.

  The DC / DC converter 13 has the following configuration. One end of an inductor 21 is connected to the input side terminal 17. A smoothing capacitor 23 is also connected between the ground. Here, since the maximum voltage when the voltage is converted by the DC / DC converter 13 is applied to the smoothing capacitor 23, a capacitor having a withstand voltage larger than the maximum voltage is used.

  One end of a first switching element 25 and a second switching element 27 is connected to the other end of the inductor 21. The other end of the first switching element 25 is connected to the ground, and the other end of the second switching element 27 is connected to the output side terminal 29. The FET is used for both the first switching element 25 and the second switching element 27. Accordingly, the parasitic diode 31 is formed in the direction shown in FIG. The ground is connected to the ground of the vehicle via a ground terminal 33. With such a circuit configuration, the DC / DC converter 13 has a synchronous rectification step-up type configuration in which the voltage at the input side terminal 17 can be boosted and output from the output side terminal 29.

  The switch 15, the first switching element 25, and the second switching element 27 are connected to the control circuit 35 by signal system wiring. The control circuit 35 includes a microcomputer and peripheral circuits, and outputs on / off signals PSW, SW1, and SW2 to the switch 15, the first switching element 25, and the second switching element 27, respectively. Perform on / off control. Further, it is also connected to a vehicle side control circuit (not shown), and various information is transmitted and received by a data signal data. In the first embodiment, the configuration in which the control circuit 35 is built in the DC / DC converter 13 as shown in FIG. 1 is shown, but this may be provided separately.

  In such a power supply device 11, the main power supply 18, the load 39, and the generator 41 are connected to the anode of the diode 19 in the switch 15 in order to charge the regenerative power of the vehicle and discharge it during non-regeneration. ing. Here, the load 39 is an electrical component mounted on the vehicle. The generator 41 generates electric power by rotation of the engine, and generates the regenerative electric power when the vehicle is braked.

  On the other hand, a power storage unit 43 for charging the regenerative power is connected to the output side terminal 29. The power storage unit 43 uses an electric double layer capacitor having excellent rapid charge / discharge characteristics in order to efficiently charge the regenerative power generated sharply.

  With the above configuration, when the regenerative power is generated by the generator 41, the power supply device 11 boosts the voltage to charge the power storage unit 43, and when the non-regeneration time is reached, the regenerative power stored by the power storage unit 43 And the main power supply 18 and the load 39 are discharged. As a result, the regenerative power can be used effectively, and the vehicle can be made highly efficient and fuel efficient.

  Next, the characteristic operation of the power supply device 11 will be described with reference to FIG. In FIG. 2A, the solid line represents the inductor current I flowing through the inductor 21, and the broken line represents the average value thereof.

  First, from time t0 to t1, as shown in FIG. 2 (e), it is assumed that the DC / DC converter 13 is off, that is, not operating. Therefore, as shown in FIGS. 2B and 2C, both the first switching element 25 and the second switching element 27 are off. Further, as shown in FIG. 2D, the control circuit 35 also turns off the switch 15. Thus, by turning off the switch 15 while the DC / DC converter 13 is stopped, the connection between the main power source 18 side and the power storage unit 43 side can be more reliably disconnected. The possibility of an unexpected current flowing between the two can be reduced, and high reliability can be obtained. By these operations, as shown in FIG. 2A, the inductor current I does not flow from time t0 to t1.

  Next, it is assumed that the generator 41 generates the regenerative power at time t1. This information is input from the vehicle side control circuit to the control circuit 35 as the data signal data. In response to this, the control circuit 35 turns on and activates the DC / DC converter 13 as shown in FIG. 2 (e) in order to charge the regenerative power to the power storage unit 43. At this time, as shown in FIGS. 2B and 2C, both the first switching element 25 and the second switching element 27 are on / off controlled to perform synchronous rectification from the start-up. Further, the control circuit 35 keeps the switch 15 off at time t1, as shown in FIG. 2 (d).

  In this way, the DC / DC converter 13 is activated, and the first switching element 25 and the second switching element 27 are on / off controlled so that the pulse width gradually changes. Specifically, after time t1, as shown in FIG. 2B, control is performed so that the ON period of the first switching element 25 in one cycle of the pulse increases with time. Further, since the operation of the second switching element 27 is an inversion operation of the first switching element 25, as shown in FIG. 2C, the on-period of the second switching element 27 is reduced with time. To control.

  By such an operation, the inductor current I reciprocates between positive and negative values as shown in FIG. 2A, but the average value maintains 0 as shown by the broken line. Even if the inductor current I becomes negative, since the switch 15 is off, the diode 19 suppresses the backflow of current from the power storage unit 43 side to the main power source 18 side.

  Note that immediately after the start of the DC / DC converter 13, that is, immediately after the time t1, the waveform of the inductor current I is greatly broken as shown in FIG. This is because when the second switching element 27 is turned on, a closed circuit is formed by the power storage unit 43, the inductor 21, and the smoothing capacitor 23, and a voltage difference between the power storage unit 43 and the main power supply 18. This is because is suddenly applied to the closed circuit. That is, the power storage unit 43 is equivalent to a DC voltage source in the short term, and the closed circuit is obtained from the internal resistance R of the entire closed circuit, the inductance L of the inductor 21, and the capacitance C of the smoothing capacitor 23. This corresponds to an LCR series circuit having the DC voltage source. Therefore, when the voltage difference is suddenly applied here, a sine wave having a frequency determined by the LCR series circuit and a triangular wave generated by the on / off operation of the first switching element 25 and the second switching element 27 are combined. Will be. Therefore, immediately after the time t1 when the second switching element 27 has a long on period, the waveform of the inductor current I collapses. Thereafter, as the ON period of the second switching element 27 becomes shorter, the influence of the sine wave becomes smaller, and the waveform of the inductor current I shifts to the triangular wave.

  When the triangular wave is stabilized in this way, the average value gradually increases as shown by the broken line in FIG. Then, when reaching the time t2 when the initial operation period (soft start period) ends, the average value of the inductor current I becomes stable. Thereby, the output current of the DC / DC converter 13 is also stabilized.

  Next, after time t2 when the initial operation period ends, at time t3 in which a margin for reliably stabilizing the average value of the inductor current I is added, the control circuit 35 is as shown in FIG. Then, the switch 15 is turned on. At this time, since the DC / DC converter 13 is already operating stably by synchronous rectification, as shown in FIG. 2A, even if the average current to the power storage unit 43 is low, the current flows backward. It will continue to output a stable low current without having to. Therefore, the control circuit 35 is in a state where no backflow current flows from the output side terminal 29 of the DC / DC converter 13 to the input side terminal 17, that is, after the output current of the DC / DC converter 13 is stabilized ( The switch 15 is controlled to be turned on at time t3 within a predetermined period from time t2). As a result, it is possible to output a stable low current while preventing reverse current flow when the DC / DC converter 13 is started.

  When the switch 15 is turned on at time t3, the voltage drop Vf due to the diode 19 disappears, so the input terminal voltage Vt increases by the voltage drop Vf. Along with this, the average value of the inductor current I shown in FIG. 2 (a) also rises. However, since the magnitude of the voltage drop Vf is smaller than the input terminal voltage Vt, the average value rises slightly. It is. The DC / DC converter 13 operates to stabilize the average value as the average value increases. However, since the increase width is small as described above, the average value is stabilized immediately. For these reasons, the change in the average value is not shown in FIG.

  With the above configuration and operation, it is possible to obtain the power supply device 11 in which switching from diode rectification to synchronous rectification is unnecessary and current does not flow backward.

  Although the switch 15 is turned on at time t3 in FIG. 2D, the loss due to the diode 19 can be reduced. Therefore, the switch 15 is turned on within a predetermined period (for example, time t3) after the start-up of the DC / DC converter 13 (time t2).

  In addition, the regenerative power stored in the power storage unit 43 is discharged to the main power supply 18 and the load 39 during non-regeneration, and is specifically controlled as follows.

  If the control circuit 35 determines that the vehicle is currently not regenerating based on the data signal data from the vehicle-side control circuit, the control circuit 35 determines whether or not sufficient power is stored in the power storage unit 43. This is determined by the voltage of the power storage unit 43 obtained from a power storage unit voltage detection circuit (not shown).

  If the power storage unit 43 is not storing sufficient power, the DC / DC converter 13 is kept off and waits until the next regenerative power is charged.

  On the other hand, if the power storage unit 43 stores sufficient power, the control circuit 35 turns on the switch 15 in order to discharge the power of the power storage unit 43 to the main power source 18 or the load 39. The first switching element 25 and the second switching element 27 are turned on / off to operate the DC / DC converter 13. Thereby, the power of the power storage unit 43 is stepped down by the DC / DC converter 13 and supplied to the main power supply 18 and the load 39.

  Thereafter, when the voltage of the power storage unit 43 decreases until it becomes substantially equal to the voltage of the main power supply 18, the control circuit 35 stops the operation of the DC / DC converter 13 and turns off the switch 15.

  By such an operation, the regenerative power can be supplied to the main power supply 18 and the load 39 at the time of non-regeneration, so that the regenerative power can be used effectively and the power generation of the generator 41 during that time becomes unnecessary. This can reduce the burden on the vehicle and improve fuel efficiency.

  In the first embodiment, as described above, the operation of the DC / DC converter 13 is stopped and the switch 15 is turned off. This is because the power supply device 11 is in use. The switch 15 may be controlled to remain on without stopping the DC / DC converter 13. In this case, although power consumption due to the continuous operation of the DC / DC converter 13 occurs, a period for restarting the DC / DC converter 13 is not necessary, and the power storage unit 43 can be charged / discharged immediately.

(Embodiment 2)
FIG. 3 is a block circuit diagram of the power supply apparatus according to Embodiment 2 of the present invention. FIG. 4 is a time-dependent change diagram of the voltage / current of the power supply device according to the second embodiment of the present invention. FIG. 4A is a time-dependent change diagram of the input-side terminal voltage Vt, and FIG. , (C) is a timing chart of the first switching element, (d) is a timing chart of the second switching element, (e) is a timing chart of the switch, (f) is a timing chart of the DC / DC converter, Each is shown. In FIG. 3, thick lines indicate power system wiring, and thin lines indicate signal system wiring.

  In the configuration of the power supply device shown in FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, detailed description thereof will be omitted, and only different points will be described. That is, the features in FIG. 3 are as follows.

  1) In the switch 15, a main power supply side voltage detection circuit 51 is electrically connected to a terminal connected to the main power supply 18.

  2) The input side terminal voltage detection circuit 53 is electrically connected to the input side terminal 17.

  3) The main power supply side voltage detection circuit 51 and the input side terminal voltage detection circuit 53 are electrically connected to the control circuit 35. Therefore, the voltage detected by the main power supply side voltage detection circuit 51 is read into the control circuit 35 as the main power supply side voltage Vb. The voltage detected by the input side terminal voltage detection circuit 53 is read into the control circuit 35 as the input side terminal voltage Vt.

  Other configurations are the same as those in FIG.

  Next, the characteristic operation of the power supply device 11 will be described with reference to FIG. FIG. 4A shows a change with time in the average value of the input terminal voltage Vt. In FIG. 4B, the solid line indicates the inductor current I flowing through the inductor 21, and the broken line indicates the average value thereof. Further, after the DC / DC converter 13 is activated, the control circuit 35 always performs an operation of reading the main power supply side voltage Vb and the input side terminal voltage Vt. Further, since the input side terminal voltage Vt fluctuates due to the on / off operation of the first switching element 25 and the second switching element 27, the control circuit 35 obtains an average value of the input side terminal voltage Vt. Is also going.

  First, from time t10 to t11, as shown in FIG. 4 (f), the DC / DC converter 13 is off, that is, in a non-operating state, so as shown in FIGS. 4 (c) and 4 (d). The first switching element 25 and the second switching element 27 are both off. Furthermore, for the same reason as in the first embodiment, as shown in FIG. 4E, the control circuit 35 also turns off the switch 15. With these operations, as shown in FIG. 4B, the inductor current I does not flow from time t10 to t11. Accordingly, as shown in FIG. 4A, the input terminal voltage Vt is equal to a value (= Vb−Vf) obtained by subtracting the voltage drop Vf of the diode 19 from the main power supply voltage Vb.

  Next, when generation of the regenerative power by the generator 41 occurs at time t11, the control circuit 35 charges the regenerative power to the power storage unit 43, as shown in FIG. The DC converter 13 is turned on to start up. At this time, as shown in FIGS. 4C and 4D, both the first switching element 25 and the second switching element 27 are on / off controlled to perform synchronous rectification from the start-up. Further, the control circuit 35 keeps the switch 15 off at time t11 as shown in FIG. 4 (e).

  After the time t11 when the DC / DC converter 13 is started in this way, as in the first embodiment, as shown in FIG. 4C, the ON period of the first switching element 25 increases with time. As shown in FIG. 4D, the ON period of the second switching element 27 decreases with time.

  As a result, the inductor current I reciprocates between positive and negative values as shown in FIG. 4B, but the average value maintains 0 as shown by the broken line. Even if the inductor current I becomes negative, since the switch 15 is off, the diode 19 suppresses the backflow of current from the power storage unit 43 side to the main power source 18 side. Note that the reason why the waveform of the inductor current I largely collapses as shown in FIG. 4B immediately after time t11 is as described in the first embodiment.

  However, in the conventional DC / DC converter, a reverse flow is generated at the start-up, that is, the voltage of the power storage unit 43 (hereinafter referred to as the output side terminal voltage Vc) is higher than the main power supply side voltage Vb. When the second switching element 27 is turned on, the instantaneous value of the input side terminal voltage Vt rapidly rises to the output side terminal voltage Vc after time t11, and when the second switching element 27 is turned off, the instantaneous value before time t11 is obtained. It suddenly drops to a voltage (= Vb−Vf). Therefore, as shown in FIG. 4A, the average value of the input terminal voltage Vt rapidly increases after time t11, and then decreases as the ON period of the second switching element 27 decreases with time. .

  Thereafter, when time t12 is reached, the triangular wave of the inductor current I indicated by the solid line in FIG. 4B is stabilized, and the average value of the input terminal voltage Vt is as shown in FIG. It reaches the value (= Vb−Vf) at time t10). As described above, since the control circuit 35 always reads the main power supply side voltage Vb and the input side terminal voltage Vt after the DC / DC converter 13 is started, the average value of the input side terminal voltage Vt is read. It can be determined whether or not has reached the value at the time of activation (= Vb−Vf). The voltage drop Vf is known as an electrical characteristic value of the diode 19.

  When the control circuit 35 determines that the average value of the input-side terminal voltage Vt reaches the value at the time of activation (= Vb−Vf) at time t12, as shown in FIG. turn on. The criterion for determining that the average value of the input side terminal voltage Vt has reached the value at the time of starting is an error in the detection error of the main power supply side voltage Vb or the input side terminal voltage Vt, the average value calculation error, or the like. Within the range, the average value of the input-side terminal voltage Vt was substantially equal to the value at the start-up. In this case, since the voltage across the switch 15 is substantially equal, even if the switch 15 is turned on, the output side terminal 29 of the DC / DC converter 13 is connected to the input side terminal 17. A reverse current does not flow.

  In order to more accurately compare the average value of the input side terminal voltage Vt and the value at the start-up, the smoothing capacitor 23 is electrically connected to the input side terminal 17 as shown in FIG. It is necessary to keep. This is because if the smoothing capacitor 23 is not provided, the instantaneous fluctuation of the input side terminal voltage Vt becomes extremely large, and the error becomes large in comparison with the value at the time of start-up.

  When the switch 15 is turned on at time t12, as described in the first embodiment, the voltage drop Vf disappears, and accordingly, the average value of the input terminal voltage Vt increases, and the inductor current I Although the average value also increases, since these changes are slight, they are not shown in FIGS. 4 (a) and 4 (b).

  Thereafter, as indicated by a broken line in FIG. 4B, the average value of the inductor current I gradually increases after time t12, and when the soft start period ends, the average value of the inductor current I is reached. Is stable.

  When such an operation is compared with the operation of FIG. 2, it can be seen that the timing for turning on the switch 15 is different. That is, in the operation of FIG. 2, the switch 15 is turned on within the predetermined period after the soft start period ends. In the operation of FIG. 4, the voltage of the diode 19 is changed from the main power supply side voltage Vb. If the value obtained by subtracting the drop Vf is substantially equal to the input terminal voltage Vt, the switch 15 is turned on. Therefore, the configuration of the second embodiment can turn on the switch 15 earlier than the configuration of the first embodiment. This is because, as described above, if the input side terminal voltage Vt is substantially equal to the value at the time of start-up (= Vb−Vf), no reverse current flows even if the switch 15 is turned on. . By such an operation, it is necessary to detect the main power supply side voltage Vb and the input side terminal voltage Vt as compared with the first embodiment. Therefore, although the circuit configuration is slightly complicated, the loss due to the diode 19 is minimized. Can be suppressed.

  In the operation of the second embodiment, the average value of the input-side terminal voltage Vt and the value at the time of starting (= Vb−Vf) are compared when the DC / DC converter 13 is started. As apparent from (a), immediately after the DC / DC converter 13 is started, the input side terminal voltage Vt and the value at the time of startup (= Vb−Vf) are equal, and immediately thereafter the input side terminal The behavior in which the average value of the voltage Vt increases is shown. Therefore, the control circuit 35 may determine that the input-side terminal voltage Vt is equal to the value at the time of activation (= Vb−Vf) immediately after the activation, and may turn on the switch 15. Therefore, in order to avoid such a malfunction, the control circuit 35 starts up the DC / DC converter 13 for a predetermined time (for example, several millimeters when the average value of the input side terminal voltage Vt is surely increased). Seconds), the main power supply voltage Vb and the input terminal voltage Vt are detected from the main power supply voltage detection circuit 51 and the input terminal voltage detection circuit 53, respectively.

  With the above configuration and operation, it is possible to obtain the power supply device 11 in which switching from diode rectification to synchronous rectification is unnecessary and current does not flow backward.

  In the second embodiment, the switch 15 is turned on when the input terminal voltage Vt is substantially equal to the value at the time of activation (= Vb−Vf). 19 is connected in series with the current detection circuit, and the control circuit 35 detects that the current has flowed from the anode side to the cathode side of the diode 19 after the start of the DC / DC converter 13. If so, the switch 15 may be turned on. That is, in the second embodiment, as shown in FIG. 4A, the time t12 at which the input terminal voltage Vt and the startup value (= Vb−Vf) are substantially equal is indicated by the switch 15. At this time, the average value of the inductor current I also flows in the positive direction (from the input side terminal 17 to the output side terminal 29) as shown by the broken line in FIG. 4B. . This is because, after time t12, the value obtained by subtracting the voltage drop Vf of the diode 19 from the main power supply side voltage Vb becomes larger than the input side terminal voltage Vt, and the diode 19 is turned on. Therefore, if it is detected that a current has flowed through the diode 19, the reverse current does not flow through the DC / DC converter 13 any more, and therefore the switch 15 may be turned on at that time (time t 12). .

  In such a configuration, the output of the current detection circuit is connected to the control circuit 35, and the main power supply side voltage detection circuit 51 and the input side terminal voltage detection circuit 53 are not required. Therefore, the circuit configuration is simplified when the current detection circuit is provided.

  Further, since the switch 15 is composed of an FET, the diode 19 becomes a parasitic diode. Therefore, the current detection circuit may be connected in series with the switch 15. Even in this case, since the switch 15 is off immediately after the DC / DC converter 13 is started up, the parasitic diode and the current detection circuit are electrically connected in series. The timing chart in such a configuration is the same as that shown in FIGS.

(Embodiment 3)
FIG. 5 is a block circuit diagram of a power supply device according to Embodiment 3 of the present invention. 6A and 6B are current aging diagrams of the power supply device according to the third embodiment of the present invention, in which FIG. 6A is a time variation diagram of the inductor current I, FIG. 6B is a timing chart of the first switching element, and FIG. ) Shows a timing chart of the second switching element, (d) shows a timing chart of the switch, and (e) shows a timing chart of the DC / DC converter. In FIG. 5, thick lines indicate power system wirings, and thin lines indicate signal system wirings.

  In the configuration of the power supply device shown in FIG. 5, the same components as those in FIG. 3 are denoted by the same reference numerals, detailed description thereof will be omitted, and only different points will be described. That is, the features in FIG. 5 are as follows.

  1) Instead of the input side terminal voltage detection circuit 53, an output side terminal voltage detection circuit 55 is electrically connected to the output side terminal 29 of the DC / DC converter 13.

  2) The output side terminal voltage detection circuit 55 is electrically connected to the control circuit 35. Therefore, the voltage detected by the output side terminal voltage detection circuit 55 is read into the control circuit 35 as the high voltage terminal side voltage Vc.

  Other configurations are the same as those in FIG.

  Next, the characteristic operation of the power supply device 11 will be described with reference to FIG. In FIG. 6A, the solid line indicates the inductor current I flowing through the inductor 21, and the broken line indicates the average value thereof.

  First, from time t20 to t21, as shown in FIG. 6 (e), since the DC / DC converter 13 is off, that is, not operating, as shown in FIGS. 6 (b) and 6 (c). The first switching element 25 and the second switching element 27 are both off. Furthermore, for the same reason as in the first embodiment, as shown in FIG. 6 (d), the control circuit 35 also turns off the switch 15. By these operations, as shown in FIG. 6A, the inductor current I does not flow from time t20 to t21.

  Next, when the regenerative power is generated by the generator 41 at time t21, the control circuit 35 first detects the main power supply side detection circuit 51 and the output side before starting the DC / DC converter 13. The terminal voltage detection circuit 55 detects the main power supply side voltage Vb and the output side terminal voltage Vc, respectively. Therefore, the control circuit 35 obtains the voltages of the main power supply 18 and the power storage unit 43, respectively.

  Next, the control circuit 35 obtains a predetermined time ratio Ds from the main power supply side voltage Vb and the output side terminal voltage Vc. Specifically, in the case of the time ratio with respect to the second switching element 27 (the ratio of the ON period of the second switching element 27 in one pulse period, hereinafter referred to as the time ratio D), the default time ratio Ds is Ds = It is determined by Vb / Vc. As described above, since the first switching element 25 performs the inversion operation of the second switching element 27, the duty ratio D1 with respect to the first switching element 25 has a relationship of D1 = 1−D. Therefore, the default ratio Ds1 in this case is Ds1 = 1−Ds = 1−Vb / Vc.

  In the following description, the case of the time ratio D with respect to the second switching element 27 and the default time ratio Ds will be described.

  After determining the predetermined time ratio Ds, the control circuit 35 turns on the DC / DC converter 13 and starts it up as shown in FIG. To do. At this time, as shown in FIGS. 6B and 6C, both the first switching element 25 and the second switching element 27 are on / off controlled to perform synchronous rectification from the start-up. Further, the control circuit 35 keeps the switch 15 off at time t21 as shown in FIG. 6 (d).

  After starting the DC / DC converter 13 in this manner, as in the first embodiment, after the time t21, the control circuit 35, as shown in FIG. 6B, the first switching element 25. The ON period of the second switching element 27 is controlled so as to decrease with time, as shown in FIG. 6C. When these are described by the time ratios D and D1, the time ratio D1 of the first switching element 25 increases with time, and the time ratio D of the second switching element 27 decreases with time.

  By such an operation, the inductor current I reciprocates between positive and negative values as shown in FIG. 6A, but the average value is maintained at 0 as shown by a broken line. Even if the inductor current I becomes negative, since the switch 15 is off, the diode 19 suppresses the backflow of current from the power storage unit 43 side to the main power source 18 side. Note that the reason why the waveform of the inductor current I largely collapses as shown in FIG. 6A immediately after time t21 is as described in the first embodiment.

  Thereafter, when time t22 is reached, the triangular wave of the inductor current I indicated by the solid line in FIG. Thereafter, as indicated by a broken line, the average value of the inductor current I increases, but at the time t22 immediately before the increase, the time ratio D controlled by the control circuit 35 is the predetermined time. The ratio Ds is substantially equal within the error range. In this state, the DC / DC converter 13 is in a state where no current flows between the input side terminal 17 and the output side terminal 29. It does not flow.

  Therefore, after the DC / DC converter 13 is started, the control circuit 35 compares the current time ratio D with the predetermined time ratio Ds, and at time t22 when both become substantially equal, the control circuit 35 in FIG. As shown, the switch 15 is turned on. At this time, since the DC / DC converter 13 is in a state where no current flows as described above, even if the switch 15 is turned on, the current hardly flows back.

  When the switch 15 is turned on at time t22, the voltage drop Vf of the diode 19 disappears as described in the first embodiment, and the average value of the inductor current I also changes due to the influence. Since it is very small, it is not shown in FIG.

  Thereafter, as indicated by a broken line in FIG. 6A, the average value of the inductor current I gradually increases after time t22, and when the soft start period ends, the average value of the inductor current I is reached. Is stable.

  When such an operation is compared with the operation of FIG. 4, it can be seen that the timing for turning on the switch 15 is the same. Therefore, the configuration of the third embodiment can turn on the switch 15 earlier than the configuration of the first embodiment, and the main power supply side voltage Vb and the output side terminal voltage Vc compared to the first embodiment. However, although the circuit configuration is slightly complicated, the loss due to the diode 19 can be minimized.

  Further, in the second embodiment, the main power supply side voltage Vb and the input side terminal voltage Vt must always be detected after startup. In the third embodiment, after the startup, the current time ratio D ( It is not necessary to detect the voltage only by comparing the predetermined ratio Ds), which can be known inside the control circuit 35). Therefore, control is easier in the third embodiment.

  In the second embodiment, control for avoiding malfunction of the switch 15 immediately after startup is necessary. However, in the third embodiment, voltage detection after startup is unnecessary, and thus the malfunction avoidance control described above is performed. It becomes unnecessary.

  With the above configuration and operation, it is possible to obtain the power supply device 11 in which switching from diode rectification to synchronous rectification is unnecessary and current does not flow backward.

  In the third embodiment, the switch 15 is turned on by comparing the time ratio D and the predetermined time ratio Ds in the second switching element 27. The time ratio D1 and the predetermined time ratio Ds1 may be compared. In this case, it is determined whether or not the time ratio D1 is substantially equal to the predetermined time ratio Ds1, but as described above, there is a relationship of D1 = 1−D and Ds1 = 1−Ds. When D1 = Ds1 is established, substituting D1 = 1-D and Ds1 = 1-Ds results in 1-D = 1-Ds, and thus D = Ds. Therefore, the comparison of the time ratio D1 and the predetermined time ratio Ds1 in the first switching element 25 is equivalent to the comparison of the time ratio D and the predetermined time ratio Ds in the second switching element 27. Therefore, the switch 15 may be turned on using the time ratio and the predetermined time ratio in any switching element.

  In the first to third embodiments, since the FET is used for the switch 15, the diode 19 is used as the parasitic diode of the FET. However, depending on the magnitude of the current flowing through the power supply device 11, the diode 19 may be It is good also as a structure connected separately. The switch 15 may be a switch that can be controlled on and off by the control circuit 35, for example, a relay. However, in this case, diodes 19 must be connected in parallel at both ends of the relay.

  In the first to third embodiments, when the polarity of the main power supply 18 is reversed, the control circuit 35 may add control for turning off the switch 15. As a result, the circuit elements of the DC / DC converter 13 can be protected from unexpected voltages, currents, and the like due to reverse connection of the main power supply 18, and high reliability can be obtained. The reverse connection of the main power supply 18 may be detected by the control circuit 35 monitoring the output of the main power supply side voltage detection circuit 51, or recognized by the data signal data from the vehicle control circuit. May be.

  In the first to third embodiments, an electric double layer capacitor is used for the power storage unit 43, but this may be another capacitor such as an electrochemical capacitor.

  In the first to third embodiments, the example in which the power supply device 11 is applied to the regenerative system for a vehicle has been described. However, the present invention is not limited to this example. It can be applied to all power supply devices that output.

  Since the power supply device according to the present invention can suppress the backflow of current even at a low current, it is useful as a power supply device using a DC / DC converter for converting voltage.

1 is a block circuit diagram of a power supply device according to Embodiment 1 of the present invention. FIG. 3 is a current time-dependent change diagram of the power supply device according to the first embodiment of the present invention, where (a) is a time-dependent change diagram of the inductor current I, (b) is a timing chart of the first switching element, and (c) is a second switching element. (D) is a switch timing chart, (e) is a DC / DC converter timing chart. Block circuit diagram of a power supply apparatus according to Embodiment 2 of the present invention FIG. 4 is a time-dependent change diagram of voltage current of the power supply device according to the second embodiment of the present invention, (a) is a time-dependent change diagram of the input terminal voltage Vt, (b) is a time-dependent change diagram of the inductor current I, and (c) is a first time change diagram. 1 is a timing chart of a switching element, (d) is a timing chart of a second switching element, (e) is a timing chart of a switch, and (f) is a timing chart of a DC / DC converter. Block circuit diagram of a power supply device according to Embodiment 3 of the present invention FIG. 4 is a current time-dependent change diagram of a power supply device according to Embodiment 3 of the present invention, where (a) is a time-dependent change diagram of inductor current I, (b) is a timing chart of a first switching element, and (c) is a second switching element. (D) is a switch timing chart, (e) is a DC / DC converter timing chart. Block circuit diagram of a conventional DC / DC voltage converter FIG. 7 is a current time-dependent change diagram of a conventional DC / DC voltage converter, where (a) is a time-dependent change diagram in the output current Io of the gate circuit, (b) is a timing chart of the FET transistor 109, and (c) is an FET transistor 119 Timing chart, (d) is a timing chart of the DC / DC voltage converter. FIG. 6 is a current time-dependent change diagram at a low current of the conventional DC / DC voltage converter, (a) is a time-dependent change diagram in the output current Io of the gate circuit, (b) is a timing chart of the FET transistor 109, and (c) is a time chart. Timing chart of FET transistor 119, (d) is a timing chart of the DC / DC voltage converter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Power supply device 13 DC / DC converter 15 Switch 17 Input side terminal 19 Diode 35 Control circuit 51 Main power supply side voltage detection circuit 53 Input side terminal voltage detection circuit 55 Output side terminal voltage detection circuit

Claims (9)

A synchronous rectification step-up DC / DC converter;
A main power source electrically connected to an input side terminal of the DC / DC converter via a switch;
A diode in which a cathode is electrically connected to the input side terminal and an anode is electrically connected to the main power source; and
A control circuit electrically connected to the DC / DC converter and the switch;
The control circuit starts the DC / DC converter by synchronous rectification with the switch turned off,
A power supply apparatus in which the switch is turned on when a backflow current from the output side terminal of the DC / DC converter does not flow to the input side terminal. The power supply device according to claim 1, wherein the control circuit turns on the switch within a predetermined period after the output current of the DC / DC converter is stabilized. The power supply device according to claim 1, wherein the switch is configured by a field effect transistor, and the diode is configured by a parasitic diode between a source and a drain of the field effect transistor. The power supply device according to claim 1, wherein the switch is configured by a relay in which the diodes are connected in parallel. The power supply apparatus according to claim 1, wherein the control circuit turns off the switch while the DC / DC converter is stopped. A main power supply side voltage detection circuit electrically connected to the main power supply;
An input side terminal voltage detection circuit electrically connected to the input side terminal, and a smoothing capacitor;
The main power supply side voltage detection circuit and the input side terminal voltage detection circuit have a configuration electrically connected to the control circuit,
After the DC / DC converter is activated and a predetermined time has elapsed, the control circuit receives a main power supply side voltage (Vb) and an input side terminal voltage (Vb) from the main power supply side voltage detection circuit and the input side terminal voltage detection circuit, respectively. Vt)
The switch is turned on when a value obtained by subtracting a voltage drop (Vf) of the diode from the main power supply side voltage (Vb) is substantially equal to the input side terminal voltage (Vt). The power supply device according to 1. A current detection circuit connected in series to the diode;
The current detection circuit has a configuration electrically connected to the control circuit,
The control circuit is configured to turn on the switch when the current detection circuit detects that a current flows from the anode side to the cathode side of the diode after the DC / DC converter is started. The power supply device according to 1. A main power supply side voltage detection circuit electrically connected to the main power supply;
An output side terminal voltage detection circuit electrically connected to the output side terminal; and
The input side terminal voltage detection circuit and the output side terminal voltage detection circuit are configured to be electrically connected to the control circuit,
The control circuit detects an input side voltage (Vb) and an output side terminal voltage (Vc) from the input side terminal voltage detection circuit and the output side terminal voltage detection circuit, respectively, before starting the DC / DC converter. ,
A predetermined ratio (Ds) is obtained from the input side voltage (Vb) and the output side terminal voltage (Vc),
2. The power supply device according to claim 1, wherein the switch is turned on when a duty ratio (D) after the DC / DC converter is started is substantially equal to the predetermined duty ratio (Ds). 3. The power supply apparatus according to claim 1, wherein the control circuit protects the DC / DC converter by turning off the switch when the main power supply is reversely connected.

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