JP2018207585A - Dc/dc converter - Google Patents

Abstract

To avoid enlargement or increase of weight of an entire apparatus caused by adding a sulfation removal device.SOLUTION: In a get-on state of an electric vehicle, a DC/DC converter is operated in a normal mode, and a ripple voltage that is generated in a transformed AC current flowing at a secondary side by turning on/turning off primary-side semiconductor elements Q1 and Q2 is smoothed by a smoothing capacitor Co and supplied to a low-voltage battery 3. In a non-getting-on state of the electric vehicle, the DC/DC converter is operated in a sulfation removal mode. In a case where sulfation occurs in an electrode of the low-voltage battery 3, the secondary-side ripple voltage is not smoothed by the smoothing capacitor Co but is supplied to the low-voltage battery 3 as it is, and a pulsed voltage for removing the sulfation in the electrode is applied to the electrode of the low-voltage battery 3. Therefore, in a case where sulfation occurs in the low-voltage battery 3, a pulsed DC voltage to be applied to the electrode for removing the sulfation can be generated in an existent DC/DC converter 1 even without using a dedicated device.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a DCDC converter that supplies electric power after voltage conversion to a lead battery.

  Known as an uninterruptible power supply that backs up the power supply in the event of a power failure when the power supply from the AC power supply ceases with the addition of a sulfation removal device that removes sulfation when the occurrence of sulfation in the battery is detected (For example, Patent Document 1).

JP 2007-236149 A

  In the above-mentioned uninterruptible power supply, since an additional sulfation removal device is provided, the overall device cannot be increased in size and weight, and is not suitable for use in environments where installation space and weight are limited. .

  The present invention has been made in view of the above circumstances, and an object of the present invention is to avoid the increase in size and weight of the entire device due to the addition of the sulfation removal device, and to remove sulfation generated in the lead battery. is there.

  By the way, in an electric vehicle such as an electric vehicle (EV) or a hybrid vehicle (HEV), for example, a lead battery that converts the power supply voltage of the propulsion motor to a low voltage by a DCDC converter and becomes a power supply for an auxiliary machine or the like by the converted electric power. Is charging. The present inventors pay attention to the existence of a DCDC converter that converts a power supply voltage to a low voltage and supplies it to a battery, such as a DCDC converter of an electric vehicle, and uses a configuration of an existing DCDC converter as a lead battery. As a result of examining removal of the generated sulfation, the present invention has been achieved.

And in order to achieve the said objective, the DCDC converter by one aspect | mode of this invention is the following.
A normal mode in which a power supply voltage of a propulsion motor of an electric vehicle is converted to a low voltage of a lead battery lower than the power supply voltage and output to the lead battery, and a pulse generated in the process of converting the power supply voltage to the low voltage Driving is performed in any one mode selected from the sulfation removal mode in which the waveform voltage is output to the lead battery instead of the low voltage.

  According to the present invention, the sulfation removal mode is selected, and the pulse waveform voltage generated in the process of converting the power supply voltage to the low voltage of the lead battery is output to the lead battery. The sulfation generated in the lead battery can be removed while avoiding the increase in weight and weight.

It is explanatory drawing which shows the principal part of the connection relation of the low voltage battery of an electric vehicle and the low voltage supply object in which the DCDC converter which concerns on one Embodiment of this invention is used. It is a circuit diagram which shows an example of the DCDC converter of FIG. The general waveform of the pulse voltage for removing the sulfation which generate | occur | produced with the lead battery is shown, (a) is explanatory drawing which shows the waveform of the pulse voltage applied to a lead battery, (b) is (a) It is explanatory drawing which shows the waveform of the voltage change which appears in the electrode of a lead battery by application of a pulse voltage. FIG. 1 shows waveforms of voltages appearing at various parts when the DCDC converter of FIG. 1 operates in a normal mode, (a) is an explanatory diagram showing waveforms of voltages appearing between both electrode terminals of two switch elements on the primary side; (B) is explanatory drawing which shows the waveform of the voltage after the conversion output from a secondary side. FIG. 1 shows waveforms of voltages appearing at various parts when the DCDC converter of FIG. 1 operates in the sulfation removal mode, and (a) is an explanatory diagram showing waveforms of voltages appearing between both electrode terminals of two switch elements on the primary side. (B) is explanatory drawing which shows the waveform of the voltage after conversion output from a secondary side. It is a flowchart which shows an example of the procedure of the sulfation detection sequence performed by the controller of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram illustrating a main part of a connection relationship between a low-voltage battery and a low-voltage supply target of an electric vehicle in which a DCDC converter according to an embodiment of the present invention is used.

  The DCDC converter 1 of the present embodiment shown in FIG. 1 uses a transformer T to convert a DC voltage of a high voltage (corresponding to the power supply voltage in the claims, 400 V in the present embodiment) supplied from the high voltage battery Vin by a transformer T. In the embodiment, the voltage is converted into DC power of 12 V) and supplied to the low voltage battery 3 (corresponding to the lead battery in the claims). The low-voltage battery 3 supplies low-voltage DC power to a low-voltage load 5 (corresponding to an auxiliary machine in the claims) via an auxiliary machine power line 7.

  Here, the DCDC converter 1 of this embodiment is an insulation type DCDC converter using an asymmetrical half bridge type LLC converter as shown in the circuit diagram of FIG. In the DCDC converter 1, the controller 9 (including the drive circuit) alternately turns on and off the semiconductor elements Q1 and Q2 (corresponding to the switching circuit in the claims) such as MOSFETs provided on the primary side of the transformer T.

  The controller 9 alternately turns on and off the semiconductor elements Q1 and Q2 at a period of the self-resonant frequency (for example, 1.8 to 2.0 MHz) of the LLC circuit of the DCDC converter 1. The self-resonant frequency of the LLC circuit is a resonant frequency between the parasitic inductance (excitation inductance and leakage inductance) on the primary side of the transformer T and the capacitor Cr.

  When the controller 9 turns on the semiconductor elements Q1 and Q2, a ripple voltage of about 15 to 25 V is generated on the secondary side of the transformer T as shown in the explanatory diagram of FIG. For this reason, the DCDC converter 1 shown in FIG. 2 smoothes the ripple voltage by the output-side smoothing capacitor Co provided on the secondary side of the transformer T and supplies the smoothed voltage to the low-voltage battery 3 of FIG.

  By the way, the low voltage battery 3 of this embodiment is a lead battery using a PbO2 electrode rod as a positive electrode and a Pb electrode rod as a negative electrode.

When discharging a lead battery, the chemical formula
Positive electrode: PbO2 + H2SO4 → PbSO4 + H2O
Negative electrode: Pb + H2SO4 → PbSO4 + H2O
The chemical reaction shown in

  When sulfation occurs in which PbSO4 deposited on the electrode of the lead battery is crystallized and the effective area of the electrode is reduced, the charge / discharge characteristics of the lead battery are deteriorated. This sulfation can be removed by applying a pulse voltage of about 5 V to the electrodes as shown in the explanatory diagram of FIG. The frequency of the pulse voltage is lower than the self-resonance frequency of the LLC circuit of the DCDC converter 1, and is preferably 0.1 to 0.5 MHz.

  By the way, when the ripple voltage (about 15 to 25 V) of FIG. 3A is supplied to the low voltage battery 3 of FIG. 1, the low voltage battery 3 is charged by a reduction reaction that occurs in the electrolyte in which the electrodes are immersed. The remaining voltage minus the charge is applied to the electrode of the low voltage battery 3. The voltage applied to the electrode at this time is about 5 V, which is suitable for removing the electrode sulfation.

  Therefore, in the present embodiment, as shown in FIG. 2, an output side capacitor switch 11 connected in series with the output side smoothing capacitor Co is provided on the secondary side of the transformer T of the DCDC converter 1 and is turned on and off by the controller 9. I try to let them. When the controller 9 turns off the output side capacitor switch 11, the DC power converted into a low voltage by the transformer T is output to the low voltage battery 3 without smoothing the ripple voltage by the smoothing capacitor Co.

  When the DC power converted into the low voltage is output to the low voltage battery 3 without smoothing the ripple voltage, the low voltage load 5 connected to the low voltage battery 3 via the auxiliary power line 7 is also supplied to the low voltage battery 3. The ripple voltage is applied, and there is a possibility that the operation of the low voltage load 5 is hindered.

  Therefore, in this embodiment, the auxiliary line switch 13 is provided in the DCDC converter 1 and connected in series to the auxiliary power line 7 and is turned on and off by the controller 9. When the controller 9 turns off the auxiliary machine line switch 13, the low voltage load 5 is disconnected from the DCDC converter 1 and the low voltage battery 3.

  By the way, the low voltage load 5 disconnected from the DCDC converter 1 and the low voltage battery 3 cannot be operated because the power supply is completely cut off. For this reason, it is necessary for the controller 9 to turn off the auxiliary machine line switch 13 when the electric vehicle is in a non-riding state (for example, a door lock state, a seat non-sitting state, etc.). Therefore, the controller 9 recognizes the state transition from the boarding state (for example, the door unlocked state, the seat seating state, etc.) of the electric vehicle to the non-boarding state and vice versa.

  Here, the keyless unit 15 that performs door lock and door unlock operations in response to a remote control (not shown) operation or a fingerprint authentication operation of a door knob (not shown) is always in the non-riding state of the electric vehicle. It is necessary to supply power so that it can operate. Therefore, the keyless unit 15 is disconnected from the low voltage load 5 and directly connected to the low voltage battery 3 without going through the auxiliary power line 7.

  Further, in order to recognize the switching between the riding state and the non-riding state of the electric vehicle, it is necessary to always supply power to the controller 9. Therefore, power is directly supplied to the controller 9 from the high voltage battery side.

  Controller 9 operates DCDC converter 1 in the normal mode when the electric vehicle is in a boarding state. In the normal mode, the controller 9 turns on the output side capacitor switch 11 and the auxiliary line switch 13 to connect the low voltage load 5 to the DCDC converter 1 and the low voltage battery 3.

  In the normal mode, the controller 9 alternately turns on and off the semiconductor elements Q1 and Q2 of the DCDC converter 1 at a period of the self-resonant frequency (for example, 1.8 to 2.0 MHz) of the LLC circuit.

  Therefore, in the normal mode, as shown in the explanatory diagram of FIG. 4A, the voltage Vp due to the on / off of the semiconductor element Q1 and the voltage Vn due to the on / off of the semiconductor element Q2 are the primary of the transformer T across the dead time. Alternately applied to the sides. As a result, an alternating current having a self-resonant frequency flows on the primary side of the transformer T.

  Then, the AC current after transformation flowing through the secondary side of the transformer T is rectified, and the ripple voltage generated by turning on and off the semiconductor elements Q1 and Q2 is smoothed by the smoothing capacitor Co. FIG. 4B is an explanatory diagram. As shown in FIG. 5, for example, a low voltage DC power of 12 V is output to the low voltage battery 3.

  On the other hand, the controller 9 in FIG. 2 operates the DCDC converter 1 in the sulfation removal mode when the electric vehicle is not in the riding state. In the sulfation removal mode, the controller 9 turns off the output side capacitor switch 11 and the auxiliary machine line switch 13 to disconnect the low voltage load 5 from the DCDC converter 1 and the low voltage battery 3.

  In addition, the controller 9 is configured to cycle the semiconductor elements Q1 and Q2 of the DCDC converter 1 at a frequency (for example, 0.1 to 0.5 MHz) that is lower than the self-resonant frequency of the LLC circuit and is suitable for a pulsed voltage for removing sulfation. Turn on and off alternately with.

  Therefore, in the sulfation removal mode, as shown in the explanatory diagram of FIG. 5A, the voltage Vp due to the on / off of the semiconductor element Q1 and the voltage Vn due to the on / off of the semiconductor element Q2 are separated from each other with the dead time interposed therebetween. Applied alternately to the primary side. Thereby, an alternating current having a frequency (preferably 0.1 to 0.5 MHz) lower than the self-resonant frequency flows on the primary side of the transformer T.

  Then, after the transformed AC current flowing through the secondary side of the transformer T is rectified, the ripple voltage generated by turning on and off the semiconductor elements Q1 and Q2 is not smoothed by the smoothing capacitor Co, but is pulsed in the range of 15 to 25V. A DC voltage, for example, sawtooth wave-like low voltage DC power having a peak at about 20 V as shown in the explanatory diagram of FIG. 5B is output to the low voltage battery 3.

  Next, an example of a sulfation detection sequence executed by the controller 9 according to a program stored in a ROM (not shown) will be described with reference to the flowchart of FIG.

  Assuming that the DCDC converter 1 is operating in the normal mode, first, the controller 9 detects that the keyless unit 15 detects both the OFF of the ignition switch (not shown) and the door lock state (both in steps S1 and S3). YES), both the auxiliary machine line switch 13 and the output side capacitor switch 11 are turned off (steps S5 and S7).

  Then, the controller 9 charges and discharges the low voltage battery 3 in a predetermined pattern, and performs deterioration diagnosis of charge / discharge characteristics for determining whether or not sulfation has occurred in the low voltage battery 3 (step S9). ). As a result, if sulfation has not occurred in the low-voltage battery 3 (NO in step S11), the operation of the DCDC converter 1 in the normal mode is stopped (step S13), and the series of processes is terminated.

  On the other hand, when sulfation has occurred in the low voltage battery 3 (YES in step S11), the controller 9 shifts from the normal mode to the sulfation removal mode (step S15). Since the auxiliary machine line switch 13 and the output side capacitor switch 11 are already turned off in steps S5 and S7, the controller 9 changes the on duty of the semiconductor elements Q1 and Q2 to change the semiconductor elements Q1 and Q2 Is changed to a frequency (for example, 0.1 to 0.5 MHz) lower than the self-resonant frequency of the LLC circuit of the DCDC converter 1.

  The controller 9 repeats the deterioration diagnosis of the charge / discharge characteristics of the low-voltage battery 3 until the door unlocked (unlocked) state is detected (NO in step S17), and the result is low. If the result remains that the sulfation has occurred in the voltage battery 3 (YES in step S11), the operation in the sulfation removal mode is continued (step S15).

  Further, the result of the deterioration diagnosis (step S9) of the charge / discharge characteristics of the low-voltage battery 3 in which the operation in the sulfation removal mode is continuously repeated until the door unlocked (unlocked) state is detected (NO in step S17) However, if the result is changed to the result that sulfation has not occurred (YES in step S11), after the operation of the DCDC converter 1 in the normal mode is stopped (step S13), the sulfation detection sequence is terminated and another sequence is performed. Migrate to

  Further, when the controller 9 is in a state where sulfation is occurring in the low voltage battery 3 (YES in step S11) and detects a door unlocked (unlocked) state (YES in step S17), the controller 9 switches from the sulfation removal mode. After shifting to the normal mode (step S19), a series of processing is terminated, and the procedure of the sulfation detection sequence after step S1 is repeated and executed.

  With the transition from the sulfation removal mode to the normal mode, the controller 9 changes the on-duty of the semiconductor elements Q1 and Q2 to change the on-off period of the semiconductor elements Q1 and Q2 to the self-resonant frequency of the LLC circuit of the DCDC converter 1. (For example, 1.8 to 2.0 MHz), and both the auxiliary machine line switch 13 and the output side capacitor switch 11 are turned on.

  As described above, according to the DCDC converter 1 of the present embodiment, the electric vehicle is operated in the normal mode in the boarded state, and after the transformation that flows through the secondary side by turning on and off the primary-side semiconductor elements Q1, Q2. The ripple voltage generated in the alternating current is smoothed by the smoothing capacitor Co and supplied to the low voltage battery 3.

  Further, when the electric vehicle is in a non-riding state and operates in the sulfation removal mode and sulfation is generated at the electrode of the low voltage battery 3, the secondary side ripple voltage is not smoothed by the smoothing capacitor Co and is kept low. The voltage is supplied to the voltage battery 3 and a pulse voltage for removing electrode sulfation is applied to the electrode of the low voltage battery 3.

  For this reason, when sulfation occurs in the low voltage battery 3, the pulsed DC voltage generated in the process of voltage conversion in the existing DCDC converter 1 can be removed for sulfation without using a dedicated device. It can be applied to the electrode. Therefore, it is possible to remove the sulfation generated in the low-voltage battery 3 by using the existing configuration and avoiding the increase in size and weight of the power supply system of the electric vehicle.

  Note that the configuration for preventing the output of the DCDC converter 1 whose ripple voltage is not smoothed from being supplied to the low voltage load 5 during the operation in the sulfation removal mode is not necessarily provided in the auxiliary power supply line 7 of the present embodiment. The auxiliary machine line switch 13 may not be provided, and the auxiliary machine line switch 13 may be omitted.

  The present invention is widely applicable to DCDC converters that supply electric power after voltage conversion to a lead battery.

  The present invention can be used in a DCDC converter that supplies electric power after voltage conversion to a lead battery.

1 DCDC converter 3 Low voltage battery 5 Low voltage load (auxiliary machine)
7 Auxiliary power supply line 9 Controller 11 Output side capacitor switch 13 Auxiliary machine line switch 15 Keyless unit Co Smoothing capacitor Cr Capacitor Q1, Q2 Semiconductor element (switching circuit)
T transformer Vin High voltage battery Vn voltage Vp voltage

Claims (7)

A normal mode in which the power supply voltage of the electric vehicle is converted to a low voltage of the lead battery (3) lower than the power supply voltage and output to the lead battery (3);
A sulfation removal mode for outputting a pulse waveform voltage generated in the process of converting the power supply voltage to the low voltage to the lead battery (3) instead of the low voltage;
DCDC converter (1) driven in any one selected mode.   An output-side capacitor switch (11) connected in series to a smoothing capacitor (Co) between output terminals to which the lead battery (3) is connected, and the output-side capacitor switch (11) is in the sulfation removal mode; The DCDC converter (1) according to claim 1, which is turned off.   The DCDC converter (1) according to claim 2, wherein the output-side capacitor switch (11) is turned on in the normal mode.   The DCDC converter (1) is an isolated DCDC converter using an LLC circuit as a primary circuit, and the switching circuit (Q1, Q2) of the primary circuit is 0.1 to 0.5 MHz in the sulfation removal mode. The DCDC converter (1) according to claim 1, 2 or 3, which is switched with a period of   Auxiliary line switch connected in series to an auxiliary power line (7) connecting an auxiliary machine (5) operating at a low voltage of the lead battery (3) to an output terminal to which the lead battery (3) is connected. The DCDC converter (1) according to claim 1, 2, 3 or 4, wherein the auxiliary line switch (13) is turned off in the sulfation removal mode.   The DCDC converter (1) according to claim 5, wherein the auxiliary line switch (13) is turned on in the normal mode.   The sulfation removal mode is selected after switching from the normal mode after detection of getting off of the driver of the electric vehicle, and deselected so as to switch to the normal mode when the boarding of the driver is detected during the selection. 6. The DCDC converter (1) according to 6.

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