DCDC Converter

Abstract

The DCDC converter (8) comprises: a switching element (11) connected to an input terminal (9); a coupling capacitor (12) connected to the switching element via a first connection point (J1); a first inductor (13) connected to the coupling capacitor via a second connection point (J2) and connected to an output terminal (10) via a third connection point (J3); a control circuit (14) controlling the switching element; a second inductor (15) connected to the first connection point and ground; a first diode (16) connected to the second connection point and ground; a smoothing capacitor (17) connected to the third connection point and ground; a comparator (18) providing a driving voltage, comparing the voltage at the output terminal with a reference voltage and outputting the comparison result to the control circuit; a second diode (19) connected to the second connection point and the comparator, providing a driving voltage for driving the comparator; and an output capacitor (20) connected to the second diode and ground. The operation of the DCDC converter is stable.

Description

Technical Field

[0001] The present invention relates to a DCDC converter used in various electronic devices. Background Art

[0002] Figure 6 1 is a circuit block diagram of a conventional DCDC converter 1. The DCDC converter 1 includes a converter unit 2, a comparator 3, an input terminal 4, and an output terminal 5. A DC power supply 6 is connected to the input terminal 4, and a load 7 is connected to the output terminal 5. The voltage at the output terminal 5 is compared with a reference voltage VB by the comparator 3, and the converter unit 2 is controlled according to the comparison result, so that the DCDC converter 1 realizes stabilization of the voltage supplied to the load 7 through the output terminal 5.

[0003] A conventional DCDC converter similar to the DCDC converter 1 is disclosed in Patent Document 1, for example.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-20641 Summary of the invention

[0007] The DCDC converter includes: a switching element connected to an input terminal; a coupling capacitor connected to the switching element via a first connection point; a first inductor connected to the coupling capacitor via a second connection point and connected to an output terminal via a third connection point; a control circuit that controls the switching element; a second inductor connected to the first connection point and to ground; a first diode connected to the second connection point and to ground; a smoothing capacitor connected to the third connection point and to ground; a comparator that supplies a driving voltage, compares a voltage at an output terminal with a reference voltage, and outputs a comparison result to the control circuit; a second diode connected to the second connection point and the comparator and supplies a driving voltage for driving the comparator; and an output capacitor connected to the second diode and to ground.

[0008] The operation of this DCDC converter is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 1 is a circuit block diagram of a DCDC converter in an embodiment.

[0010] Figure 2 : is a circuit block diagram showing the operation state of the DCDC converter in the embodiment.

[0011] Figure 3 : is a circuit block diagram showing the operation state of the DCDC converter in the embodiment.

[0012] Figure 41 is a diagram showing the operation timing of the DCDC converter in the embodiment.

[0013] Figure 5 1 is a diagram showing the operation timing of the DCDC converter in the embodiment.

[0014] Figure 6 This is a circuit block diagram of a conventional DCDC converter. DETAILED DESCRIPTION

[0015] Figure 1 1 is a circuit block diagram of a DCDC converter in an embodiment. The DCDC converter 8 includes an input terminal 9, an output terminal 10, a switching element 11, a coupling capacitor 12, an inductor 13, a control circuit 14, an inductor 15, a diode 16, a smoothing capacitor 17, a comparator 18, a diode 19, and an output capacitor 20. The switching element 11, the coupling capacitor 12, and the inductor 13 are connected in series from the input terminal 9 to the output terminal 10. The inductor 15 connects the connection point J1 to the ground GND, which is a connection point connecting the switching element 11 and the coupling capacitor 12. The diode 16 connects the connection point J2 to the ground GND, which is a connection point connecting the coupling capacitor 12 and the inductor 13. The cathode of the diode 16 is connected to the connection point J2, and the anode is connected to the ground GND. The smoothing capacitor 17 connects the connection point J3 to the ground GND, which is a connection point connecting the inductor 13 and the output terminal 10.

[0016] The comparator 18 performs a comparison operation on the reference voltage VB and the output voltage VOUT of the output terminal 10, and outputs the operation result to the control circuit 14. The control circuit 14 controls the operation of the switch element 11 based on the operation result in the comparator 18. The diode 19 is provided in the supply path 21 connecting the connection point J2 connecting the coupling capacitor 12 and the inductor 13 and the comparator 18. The anode 19B of the diode 19 is connected to the connection point J2, and the cathode 19A is connected to the comparator 18. The supply path 21 supplies the driving voltage VCC for driving the comparator 18. In addition, the output capacitor 20 is connected to the cathode 19A of the diode 19 and the ground GND. The switch element 11 has one end 11A connected to the input terminal 9 and the other end 11B. The coupling capacitor 12 has one end 12A and the other end 12B connected to the other end 11B of the switch element 11 through the connection point J1. The inductor 13 has one end 13A connected to the other end 12B of the coupling capacitor 12 through the connection point J2, and the other end 13B connected to the output end 10 through the connection point J3. The control circuit 14 controls the switch element 11. The inductor 15 has one end 15A connected to the connection point J1, and the other end 15B connected to the ground GND. The diode 16 has a cathode 16A connected to the connection point J2, and an anode 16B connected to the ground GND. The smoothing capacitor 17 has one end 17A connected to the connection point J3, and the other end 17B connected to the ground GND. The comparator 18 is configured to be driven by the drive voltage VCC, compare the voltage of the output end 10 with the reference voltage VB, and output the comparison result to the control circuit 14. The diode 19 has an anode 19B connected to the connection point J2 and a cathode 19A connected to the comparator 18, and is configured to supply the drive voltage VCC for driving the comparator 18 from the cathode 19A. The output capacitor 20 has one end 20A connected to the cathode 19A of the diode 19 and the other end 20B connected to the ground GND. The sensor 24 detects the output current IC output from the output terminal 10.

[0017] The DC power supply 23 is connected to the input terminal 9. In the embodiment, the power storage device 22 is connected to the output terminal 10. The comparator 18 has a non-inverting input terminal 18A to which the output voltage VOUT is input, an inverting input terminal 18B to which the reference voltage VB is input, and an output terminal 18C connected to the control circuit 14. The control circuit 14 outputs a control signal SC to the switch element 11. The switch element 11 connects the terminal 11A to the terminal 11B to turn on, or disconnects the terminal 11A from the terminal 11B to turn off, according to the control signal SC.

[0018] When in operation, the DCDC converter 8 boosts the voltage VIN at the input terminal 9 to an output voltage VOUT and applies the voltage to the output terminal 10 .

[0019] exist Figure 6In the conventional DCDC converter 1 shown, the comparator 3 is driven by the drive voltage VCC supplied from the converter unit 2 or the DC power supply 6. In order for the comparator 3 to operate accurately, the drive voltage VCC needs to have a voltage value sufficiently higher than the reference voltage VB, the detection voltage VD, or the input voltage VA to the comparator 3.

[0020] However, in the DCDC converter 1, the converter unit 2 operates so that the output voltage from the converter unit 2 is equal to or higher than the voltage of the DC power supply 6. When the comparator 3 directly receives the drive voltage VCC from the DC power supply 6, the drive voltage VCC has a value close to the reference voltage VB or the input voltage VA, or the drive voltage VCC has a value lower than the reference voltage VB or the input voltage VA. As a result, the comparator 3 may not operate, and the output voltage of the converter unit 2 may become unstable.

[0021] In contrast, in the DCDC converter 8 of the embodiment, a voltage higher than the output voltage VOUT of the output terminal 10 always exists at the cathode 19A of the diode 19 corresponding to the high potential end of the output capacitor 20 in the supply path 21, regardless of the output voltage VOUT of the output terminal 10. Therefore, a voltage higher than the reference voltage VB set to a value close to the voltage VIN of the input terminal 9 and the output voltage VOUT of the output terminal 10 is supplied from the supply path 21 to the comparator 18 as the drive voltage VCC. As a result, the comparator 18 can obtain a stable voltage from a part of the DCDC converter 8, and the operation of the DCDC converter 8 is stabilized.

[0022] Hereinafter, the configuration and operation of the DCDC converter 8 will be described in detail. Figure 2 and Figure 3 3 is a circuit block diagram showing the operation state of the DCDC converter 8 .

[0023] Figure 2 The schematic diagram of the circuit of the DCDC converter 8 when the switching element 11 is turned on is shown. Figure 3 The schematic diagram of the circuit of the DCDC converter 8 when the switching element 11 is turned off is shown. The power storage device 22 is connected to the output terminal 10. In the embodiment, the power storage device 22 is an electric double layer capacitor. The DCDC converter 8 operates as a charging circuit, that is, the voltage VIN at the input terminal 9 output from the DC power supply 23 is boosted to generate an output voltage VOUT, and the output voltage VOUT is applied from the output terminal 10 to the power storage device 22 to charge the power storage device 22.

[0024] Figure 41 is an operation timing diagram of the DCDC converter 8. First, at time T0, the power supply device equipped with the DCDC converter 8 is started. Or a signal for starting the DCDC converter 8 is sent to the control circuit 14 of the DCDC converter 8. When the DCDC converter 8 is started, the control circuit 14 supplies a PWM signal (pulse width modulation signal) to the switching element 11 to control the switching element 11 so that the switching element 11 is turned on and off, so that the output current IC for charging the power storage device 22 is output from the output terminal 10.

[0025] like Figure 2 As shown, when the switch element 11 is turned on, a current flows in the direction of the dotted line, a voltage VIN having a polarity determined by an arrow is generated in the inductor 15, and a voltage VC1 having a polarity indicated by an arrow is generated in the coupling capacitor 12 having a positive terminal 12A connected to the connection point J2. As a result, a voltage (VIN+VC1) which is the sum of the voltages VIN and VC1 is generated at the connection point J2. In addition, the voltage (VIN+VC1) is equal to the sum of the output voltage VOUT corresponding to the charging voltage to the power storage device 22 and the voltage VL1 having a polarity indicated by an arrow generated in the inductor 13, that is, the voltage (VOUT+VL1). Here, the voltage (VIN+VC1) at the connection point J2, that is, the voltage (VOUT+VL1), is smoothed by the output capacitor 20 through the diode 19 and the supply path 21. The smoothed voltage is supplied to the comparator 18 as the drive voltage VCC. At this time, the control circuit 14 controls the switching element 11 according to the output current IC detected by the sensor 24 so that the output current IC of the constant current IK is supplied to the storage device 22, and the output voltage VOUT equivalent to the charging voltage of the storage device 22 increases with the passage of time according to the charging voltage of the storage device 22.

[0026] The DCDC converter 8 may also replace the sensor 24 for detecting the output current IC, and include a sensor for detecting the current flowing through the coupling capacitor 12 or the inductor 13. These sensors for detecting the current include, for example, a detection resistor connected in series with the path through which the current flows. In this case, the control circuit 14 detects the potential difference between the two ends of the detection resistor, and based on the potential difference, the control circuit 14 calculates the potential difference to detect the output current IC. Alternatively, these sensors may replace the detection resistor with a current sensor capable of non-contact detection, and the control circuit 14 may detect the output current IC through the current sensor.

[0027] Even if the detection resistor is inserted in series with the current path, the driving voltage VCC is maintained to be higher than the output voltage VOUT, and the operation of the DCDC converter 8 is stable. In addition, the output current IC can be detected with a simple configuration that only inserts a DC resistor.

[0028] After a long stop period, at the time T0 when the DCDC converter 8 is started, the voltage between the terminals 20A and 20B of the output capacitor 20 is almost 0V, so the value of the driving voltage VCC driving the comparator 18 is roughly consistent with the voltage VIN of the input terminal 9. The value of the voltage VIN of the DC power supply 23 connected to the input terminal 9 is set to a value that can drive the comparator 18, so at the time T0, the comparator 18 can operate. In addition, from the time T0, the output voltage VOUT and the driving voltage VCC gradually increase with the same slope. This means that the charge accumulated in the coupling capacitor 12, the smoothing capacitor 17, and the power storage device 22 gradually increases with time, and the driving voltage VCC is equivalent to the sum of the output voltage VOUT and the voltage VIN of the input terminal 9. In the embodiment, from the time T0 to the time T2, based on the detected output current IC, the control circuit 14 repeatedly turns on and off the switch element 11 through PWM control to control the switch element 11 so that the output current IC maintains a constant current IK. Thus, the output voltage VOUT and the drive voltage VCC gradually increase linearly with the same slope. At time T1 between time T0 and time T2, the control circuit 14 turns on the switch element 11 to form Figure 2 The circuit shown in FIG. 1 may be formed by disconnecting the switch element 11. Figure 3 The circuit shown.

[0029] In the embodiment, the reference voltage VB is made consistent with the full charge voltage VF of the power storage device 22. At time T2, if the power storage device 22 is in a fully charged state, the output voltage VOUT reaches the reference voltage VB, i.e., the full charge voltage VF, then the value of the output voltage VOUT and the drive voltage VCC are constant, so that the difference between the value of the output voltage VOUT and the value of the drive voltage VCC maintains a specified potential difference. In other words, the DCDC converter 8 switches from a state of constant current output operation during the period from time T0 to time T2 to a state of constant voltage output operation after time T2 until time T3 when the DCDC converter 8 stops. At this time, the drive voltage VCC is a constant voltage VCCM having a value of the output voltage VOUT plus the voltage VL1. Here, the capacitance of the coupling capacitor 12 and the smoothing capacitor 17 may be substantially the same, or may be different. In addition, the inductance values ​​of the inductor 13 and the inductor 15 may be substantially the same, or may be different.

[0030] exist Figure 2 In FIG. 1 , although the diode 16 exists as a circuit element, it is illustrated by a dotted line because it is the same as the state where it does not exist as a circuit behavior.

[0031] like Figure 3As shown in FIG. 1 , when the switch element 11 is turned off, a current flows in the direction of the dotted line, and as the energy stored in the inductor 15 is released, a voltage VC1 having a polarity indicated by an arrow is generated between the ends 15A and 15B of the inductor 15. The diode 16 is turned on to form a closed circuit based on the inductor 15 and the coupling capacitor 12, and the voltage VC1 between the ends 15A and 15B of the inductor 15 is generated to cancel the voltage VC1 of the coupling capacitor 12 being charged. Therefore, the voltage at the connection point J2 becomes 0 because the voltage VC1 between the ends 12A and 12B of the coupling capacitor 12 is canceled by the voltage VC1 between the ends 15A and 15B of the inductor 15. Similarly, as the energy stored in the inductor 13 is released, an output voltage VOUT having a polarity indicated by an arrow is generated between the ends 13A and 13B of the inductor 13. Since the diode 16 is turned on to form a closed circuit based on the inductor 13 and the smoothing capacitor 17, the output voltage VOUT between the ends 13A and 13B of the inductor 13 is generated to cancel the output voltage VOUT between the ends 17A and 17B of the smoothing capacitor 17 to be charged. Therefore, the voltage at the connection point J2 is the same as the previous case, and the voltage VOUT between the ends 17A and 17B of the smoothing capacitor 17 is canceled by the voltage VOUT between the ends 13A and 13B of the inductor 13 and becomes 0.

[0032] At this time, the voltage at the connection point J2 is 0, and the voltage applied to the anode 19B of the diode 19 is also 0. However, the switching of the switch element 11 is repeated alternately at short time intervals before and after the time T1, so when the voltage at the connection point J2 is 0, the voltage supplied when the switch element 11 is in the on state is also smoothed by the output capacitor 20, and the drive voltage VCC is continuously supplied to the comparator 18. In addition, at this time, the control circuit 14 controls the switch element 11 so that the output current IC of the constant current IK is supplied to the power storage device 22, and the output voltage VOUT equivalent to the charging voltage of the power storage device 22 increases with the passage of time in conjunction with the charging voltage of the power storage device 22.

[0033] As described above, the output voltage VOUT compared with the reference voltage VB by the comparator 18 is always lower than the driving voltage VCC of the comparator 18 by a value of the voltage VIN supplied by the DC power supply 23. In other words, the driving voltage VCC always has a value higher than the output voltage VOUT corresponding to the reference voltage VB or the charging voltage. As a result, the comparator 18 can obtain a stable voltage from the supply path 21 of the DCDC converter 8, and the operation of the DCDC converter 8 is stable.

[0034] Here, the DCDC converter 8 performs a boost operation so that the output voltage VOUT of the output terminal 10 becomes higher than the voltage VIN of the DC power supply 23, and the output current IC as the constant current IK is supplied to the storage device 22. Then, in order to detect the charging state of the storage device 22, the boosted voltage, that is, the output voltage VOUT of the output terminal 10 indicating the charging state of the storage device 22 is input to the comparator 18. Then, the driving voltage VCC which needs to be higher than the compared voltage VOUT is supplied from the connection point J2 inside the DCDC converter 8 which outputs the voltage linked to the output voltage VOUT. Therefore, there is no need to set an independent power supply for maintaining the driving voltage VCC of the comparator 18, a complex voltage divider circuit, etc. As a result, the miniaturization of the DCDC converter 8 can also be achieved.

[0035] The power supplied to the comparator 18 through the supply path 21 is much smaller than the power supplied from the output terminal 10 to the power storage device 22. Therefore, the power supply from the connection point J2 does not substantially hinder the charging operation of the DCDC converter 8 on the power storage device 22.

[0036] As described above, at time T2, the output voltage VOUT of the DCDC converter 8, which is equivalent to the charging voltage of the power storage device 22, reaches the full charging voltage VF. Furthermore, if the control circuit 14 detects through the comparator 18 that the output voltage VOUT reaches the full charging voltage VF, the DCDC converter 8 stops the charging operation. In other words, the output current IC of the constant current IK is not supplied. Furthermore, the control circuit 14 controls the switching element 11 so that the output voltage VOUT applied to the power storage device 22 is maintained constant. Thus, the output voltage VOUT from the DCDC converter 8 is a constant voltage full charging voltage VF. The reference voltage VB is not necessarily the full charging voltage VF, but is a voltage value required by the power storage device 22.

[0037] In the embodiment, the reference voltage VB is set to the same value as the full charge voltage VF. When the voltage VOUT of the storage unit 22 is lower than the full charge voltage VF (reference voltage VB), the comparator 18 does not send a signal to the control circuit 14. At this time, the control circuit 14 controls the switch element 11 so that the charging current Ic is supplied to the output unit 10. And, if the voltage VOUT of the storage unit 22 is higher than the full charge voltage VF (reference voltage VB), the comparator 18 sends a signal to the control circuit 14, and the control circuit 14 controls the switch element 11 so that the charging current Ic is not supplied to the output unit 10.

[0038] In DCDC converter 8, coupling capacitor 12 connected to connection points J1 and J2 electrically insulates input terminal 9 from output terminal 10 when power is not supplied from input terminal 9 to output terminal 10. Therefore, power of DC power source 23 is not consumed by DCDC converter 8.

[0039] For example, even if a short-circuit failure occurs in the comparator 18 and the drive voltage VCC is forced to become 0, the coupling capacitor 12 cuts off the power from the DC power supply 23. Therefore, even if a protection device such as a fuse is provided in series with the DC power supply 23, a short-circuit current that affects the protection device is not generated, and the problem can be solved by simply repairing the DCDC converter 8. In this way, a short-circuit current is not generated in the DC power supply 23, so safety can be improved.

[0040] At time T3, the DCDC converter 8 stops. Even if the DCDC converter 8 stops, the driving voltage VCC is maintained to be a higher voltage than the output voltage VOUT, and both the driving voltage VCC and the output voltage VOUT gradually decrease. In other words, by using a double-layer capacitor for the power storage device 22, the natural discharge in the output capacitor 20 and the power storage device 22 proceeds at substantially the same level.

[0041] At time T4, the DCDC converter 8 is restarted. From time T3, during the period when the DCDC converter 8 is stopped, the natural discharge in the output capacitor 20 and the power storage device 22 is performed at substantially the same degree, so that at time T4, when the DCDC converter 8 is restarted, the above-mentioned relationship between the drive voltage VCC and the output voltage VOUT can also be maintained. Therefore, the DCDC converter 8, especially the comparator 18, can operate stably. And at time T5, if the output voltage VOUT reaches the reference voltage VB, that is, the full charge voltage VF, then the supply of the output current IC is stopped in the same manner as the operation at time T2, and the DCDC converter 8 switches to a constant voltage output operation. In the constant voltage output operation, the DCDC converter 8 maintains the voltage of the power storage device 22 as described above. Therefore, the power supply from the DCDC converter 8 to the power storage device 22 is intermittent, so the amount of power supply is small.

[0042] In addition, the driving voltage VCC is limitedly supplied when the DCDC converter 8 is operating, and is not supplied when the DCDC converter 8 is not operating. In other words, when the vehicle equipped with the DCDC converter 8 is not started, the period during which the DCDC converter 8 operates is a very short period, such as just before the vehicle is started, just after the vehicle is switched from the start state to the stop state, etc., even if it exists. Therefore, the power consumed by the comparator 18 during the stop period of the vehicle, in other words, the dark current used for the comparator 18 to operate is not generated. As a result, the deterioration of the DC power supply 23 can also be suppressed.

[0043] In the embodiment, when the DCDC converter 8 is activated, in order for the comparator 18 to operate normally, the control circuit 14 may soft-start the switching element 11 while the drive voltage VCC is a predetermined value sufficient for the comparator 18 to operate normally. Figure 5 1 is an operation timing diagram of the soft start of the DCDC converter 8. Specifically, if the DCDC converter 8 is restarted in a state where the voltage remaining in the power storage device 22 when the DCDC converter 8 is stopped, that is, the output voltage VOUT of the output terminal 10 is high, the drive voltage VCC is not sufficiently high relative to the higher output voltage VOUT at the output terminal 10 corresponding to the voltage remaining in the power storage device 22, and therefore, the comparator 18 may not operate normally and the output current IC may not be properly controlled.

[0044] exist Figure 5 In the operation shown, when the DCDC converter 8 is started at time T0, the control circuit 14 detects the output voltage VOUT of the output terminal 10 and the drive voltage VCC before driving the switch element 11. When the output voltage VOUT is higher than the specified voltage value VN and the drive voltage VCC is lower than the specified voltage value VCD, the control circuit 14 suppresses the output current IC to a current value IL smaller than the constant current IK to soft-start the DCDC converter 8, thereby protecting the DCDC converter 8 and the power storage device 22. When the output current IC of the current value IL is applied to the power storage device 22 at time T0, the output voltage VOUT rises, and the drive voltage VCC reaches the specified voltage value VCD at time T11, then from time T11, the control circuit 14 controls the switch element 11 so that the output current IC is the constant current IK. In other words, the period of using the soft start can be a short period from the start of the DCDC converter 8 to the charging of the output capacitor 20. The specified voltage value VN at the output terminal 10 can be determined to be the same as the placement voltage value or a value higher than the placement voltage value by an added voltage value, for example, when a double-layer capacitor is used for the power storage device 22, based on the placement voltage value maintained at a low value when the DCDC converter 8 is stopped, especially in the placement state, in order to suppress the deterioration of the characteristics of the double-layer capacitor. The added voltage value can be a constant voltage value of several volts, or a value obtained by adding a constant rate of several tens of percent to the voltage value maintained when the double-layer capacitor is in the placement state.

[0045] After stopping at time T3 and restarting at time T4, the DCDC converter 8 has a higher output voltage VOUT than the specified voltage value VCD but a higher drive voltage VCC than the specified voltage value VN. Therefore, the control circuit 14 controls the switch element 11 so that the output current IC is not the current value IL but a constant current IK, and no soft start is performed.

[0046] That is, when the DCDC converter 8 is started, when the drive voltage VCC is higher than the prescribed voltage value VN, the control circuit 14 controls the switch element 11 so that the output current IC is a constant current IK regardless of the output voltage VOUT. When the DCDC converter 8 is started, when the output voltage VOUT is higher than the prescribed voltage value VN and the drive voltage VCC is lower than the prescribed voltage value VCD, the control circuit 14 controls the switch element 11 so that the output current IC becomes a current value IL smaller than the constant current IK. Then, when the drive voltage VCC reaches the prescribed voltage value VCD, the control circuit 14 controls the switch element 11 so that the output current IC is a constant current IK.

[0047] Alternatively, the soft start may be always applied when the control circuit 14 starts driving the switching element 11 regardless of the output voltage VOUT.

[0048] In the above description, the operation of the DCDC converter 8 is described as charging the power storage device 22 based on the constant current output and maintaining the charging voltage of the power storage device 22 based on the boosted voltage after reaching the full charge voltage or the target charge voltage. However, the DCDC converter 8 may also operate as a step-down converter whose output voltage VOUT is lower than the voltage VIN of the input terminal 9 as needed.

[0049] -Explanation of symbols-

[0050] 8 DCDC Converter

[0051] 9 Input

[0052] 10 Output

[0053] 11 Switching elements

[0054] 12 Coupling capacitor

[0055] 13 Inductor (1st inductor)

[0056] 14 Control Circuit

[0057] 15 Inductor (second inductor)

[0058] 16 Diode (1st diode)

[0059] 17 Smoothing capacitor

[0060] 18 Comparator

[0061] 19 Diode (2nd diode)

[0062] 20 Output capacitor

[0063] 21 Supply Path

[0064] 22 Power storage device

[0065] 23 DC power supply

[0066] J1 connection point (1st connection point)

[0067] J2 connection point (second connection point)

[0068] J3 connection point (3rd connection point).

Claims

1. A DCDC converter having: Input terminal; Output terminal; a switch element having one end connected to the input end and another end; a coupling capacitor having one end connected to the other end of the switching element via a first connection point, and another end; a first inductor having one end connected to the other end of the coupling capacitor via a second connection point and the other end connected to the output end via a third connection point; A control circuit for controlling the switch element; a second inductor having one end connected to the first connection point and the other end connected to the ground; a first diode having a cathode connected to the second connection point and an anode connected to the ground; a smoothing capacitor having one end connected to the third connection point and the other end connected to the ground; a comparator configured to be driven by a driving voltage, compare the voltage of the output terminal with a reference voltage and output a comparison result to the control circuit; a second diode having an anode directly connected to the second connection point and a cathode directly connected to the comparator, the drive voltage being supplied from the cathode to the comparator, the voltage of the cathode being higher than the voltage of the output terminal; and The output capacitor has one end connected to the cathode of the second diode and the other end connected to the ground.

2. The DCDC converter according to claim 1, wherein: The control circuit is configured to control the switching element so that a constant current is output from the output terminal.

3. The DCDC converter according to claim 1, wherein: The control circuit is composed of: detecting the voltage at the output terminal before driving the switching element, When the voltage of the output terminal detected before driving the switching element is higher than a predetermined voltage value, the switching element is controlled so that the DCDC converter is started by soft start.

4. The DCDC converter according to claim 3, wherein: The DCDC converter is configured to connect a power storage device to the output end. The predetermined voltage value is determined based on a storage voltage value of the power storage device.

5. The DCDC converter according to claim 1, wherein: When the DCDC converter is started, the control circuit is configured as follows: When the driving voltage is equal to or greater than a first predetermined voltage value, the control circuit controls the switch element so that an output current output from the output terminal is a constant current; When the voltage at the output end is higher than the second specified voltage value and the driving voltage is lower than the first specified voltage value, the switching element is controlled so that the output current is a current value smaller than the constant current. Thereafter, if the driving voltage reaches the first specified voltage value, the switching element is controlled so that the output current is the constant current.

6. The DCDC converter according to claim 5, wherein: When the DCDC converter is activated and the driving voltage is equal to or higher than the first predetermined voltage value, the control circuit is configured to control the switching element so that the output current becomes the constant current regardless of the voltage at the output end.

7. The DCDC converter according to claim 5 or 6, wherein: The DCDC converter is configured to connect a power storage device to the output end. The second predetermined voltage value is determined based on an unused voltage value of the power storage device.

8. The DCDC converter according to claim 7, wherein: The DCDC converter boosts the voltage at the input end and applies the voltage to the output end.

9. The DCDC converter according to any one of claims 1 to 6, wherein: The DCDC converter boosts the voltage at the input end and applies the voltage to the output end.

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