Switching regulator, on-vehicle device, and vehicle

Abstract

This switching regulator complementarily turns on / off a first switch and a second switch in accordance with an output voltage, and, in a step-up / down mode, sets an on-duty of a third switch as a function based on input and output voltages and complementarily turns on / off the third switch and a fourth switch.

Description

Switching regulator, in-vehicle device, and vehicle

[0001] The invention disclosed in this specification relates to a step-up / step-down switching regulator, and an in-vehicle device and a vehicle having the same.

[0002] In idle-stop vehicles, where the engine is restarted multiple times, battery power continues to be consumed by onboard equipment such as AV equipment and air conditioning during the period when the engine is temporarily stopped, resulting in a more severe drop in battery voltage during cranking (engine start) than before.By using a buck-boost switching regulator that maintains output voltage when the input voltage (battery voltage) drops, onboard equipment can operate normally even if the battery voltage drops significantly during cranking.

[0003] For this reason, there is an increasing demand for step-up / step-down switching regulators in the automotive equipment market.

[0004] The buck-boost switching regulator disclosed in Patent Document 1 can prevent the appearance of the right-half-plane-zero characteristic and exhibits response characteristics similar to those of a buck characteristic, allowing the capacitance of the output capacitor to be reduced.

[0005] Japanese Patent Application Laid-Open No. 2016-226257

[0006] [Summary] In the buck-boost switching regulator disclosed in Patent Document 1, the on-duty of the third switch that is responsible for the boost operation is fixed, so when the input voltage value and the output voltage value are close to each other, the step-down ratio in the step-down operation needs to be increased, which results in increased heat generation.

[0007] The switching regulator disclosed in this specification is a switching regulator configured to generate an output voltage from an input voltage, and includes a first switch configured to have a first terminal connectable to a first application terminal to which the input voltage is applied, a second switch configured to have a first terminal connectable to a second terminal of the first switch and a second terminal connectable to a second application terminal to which a predetermined voltage lower than the input voltage is applied, an inductor configured to have a first terminal connectable to a connection node between the first switch and the second switch, and a first terminal configured to be connectable to a second terminal of the inductor and a second terminal configured to be connectable to the second application terminal. a third switch connected to a connection node between the inductor and the third switch, a fourth switch having a first end connectable to a connection node between the inductor and the third switch and a second end connectable to a third application end to which the output voltage is applied, a first control circuit configured to generate a step-down control signal for turning on / off the first switch and the second switch in a complementarily manner in accordance with the output voltage, and a second control circuit configured to set an on-duty of the third switch as a function in accordance with the input voltage and the output voltage in a step-up / step-down mode and generate a step-up control signal for turning on / off the third switch and the fourth switch in a complementarily manner.

[0008] The in-vehicle device disclosed in this specification includes a switching regulator having the above configuration.

[0009] The vehicle disclosed in this specification has the on-board equipment configured as described above.

[0010] FIG. 1 is a diagram showing an example of the overall configuration of a switching regulator according to an embodiment. FIG. 2 is a diagram showing an example of the configuration of a step-down control circuit. FIG. 3 is a diagram showing a schematic waveform of a battery voltage. FIG. 4 is a diagram showing a schematic waveform of each switch voltage in step-down mode. FIG. 5 is a diagram showing a schematic waveform of each switch voltage in step-up / step-down mode. FIG. 6 is a diagram showing the on-duty of MOS transistors Q1 and Q3. FIG. 7 is a Bode plot for step-down mode. FIG. 8 is a Bode plot for step-up / step-down mode. FIG. 9 is an external perspective view of a vehicle.

[0011] [Detailed Description] In this specification, a MOS transistor refers to a transistor whose gate structure is composed of at least three layers: a layer made of a conductor or a semiconductor such as polysilicon with a low resistance, an insulating layer, and a P-type, N-type, or intrinsic semiconductor layer. In other words, the gate structure of a MOS transistor is not limited to a three-layer structure of a metal, an oxide, and a semiconductor.

[0012] In this specification, the reference voltage means a voltage that is constant under ideal conditions, but in reality it is a voltage that may fluctuate slightly due to temperature changes and the like.

[0013] 1 is a diagram showing an example of the overall configuration of a switching regulator according to an embodiment. The switching regulator 100 of this configuration example is a buck-boost switching regulator and includes a step-down control circuit 1, MOS transistors Q1 to Q4, an inductor L1, an output capacitor C1, an output resistor R0, voltage-dividing resistors R1 to R4, a comparator 2, a reference voltage source 3, an AND gate 4, a pulse signal generation circuit 5, and a NOT gate 6.

[0014] The MOS transistor Q1 is an N-channel MOS transistor, and is connected to the input voltage, the battery voltage V BAT The drain of the MOS transistor Q1 is connected to the input voltage application terminal to which the battery voltage V is applied. BAT The MOS transistor Q1 is connected to an input voltage application terminal to which an input voltage is applied. The source of the MOS transistor Q1 is connected to one end of the inductor L1 and the drain of the MOS transistor Q2. The MOS transistor Q1 may be a P-channel MOS transistor instead of an N-channel MOS transistor. By using a P-channel MOS transistor as the MOS transistor Q1, the bootstrap circuit that is required when the MOS transistor Q1 is an N-channel MOS transistor becomes unnecessary.

[0015] The MOS transistor Q2 is an N-channel MOS transistor and is an example of a switch that connects / disconnects the current path from the ground terminal to one end of the inductor L1. As described above, the drain of the MOS transistor Q2 is connected to one end of the inductor L1 and the source of the MOS transistor Q1. The source of the MOS transistor Q2 is connected to the ground terminal. Note that a diode may be used instead of the MOS transistor Q2.

[0016] The MOS transistor Q3 is an N-channel MOS transistor and is an example of a switch that connects / disconnects a current path from the other end of the inductor L1 to the ground. The drain of the MOS transistor Q3 is connected to the other end of the inductor L1. The source of the MOS transistor Q3 is connected to the ground.

[0017] The MOS transistor Q4 is an N-channel MOS transistor, and outputs an output voltage V OUT The drain of the MOS transistor Q4 is connected to the other end of the inductor L1 and the drain of the MOS transistor Q3. The source of the MOS transistor Q4 is connected to one end of the output capacitor C1 and the output voltage V OUT The other end of the output capacitor C1 is grounded. Note that a diode may be used in place of the MOS transistor Q4.

[0018] The output capacitor C1 is the output voltage V OUT It is a smoothing capacitor to reduce the ripple of the output voltage V OUT is phase compensated by a phase compensation circuit formed by an output capacitor C1 and an output resistor R0.

[0019] The voltage dividing resistors R1 and R2 divide the output voltage V OUT is divided to produce a feedback voltage V FB and generates a feedback voltage V FB is supplied to the step-down control circuit 1.

[0020] The step-down control circuit 1 controls the feedback voltage V FBA gate signal G1 for the MOS transistor Q1 and a gate signal G2 for the MOS transistor Q2 are generated in response to the on / off switching of the MOS transistors Q1 and Q2 in a complementary manner, and the gate signals G1 and G2 are supplied to the gates of the MOS transistors Q1 and Q2. When the MOS transistors Q1 and Q2 are switched on / off, it is preferable to provide a dead time during which both the MOS transistors Q1 and Q2 are turned off.

[0021] Comparator 2 detects the battery voltage V generated by voltage dividing resistors R3 and R4. BAT and the first reference voltage V output from the reference voltage source 3. REF1 The comparator 2 compares the battery voltage V BAT The divided voltage is the first reference voltage V REF1 If the battery voltage V BAT The divided voltage is the first reference voltage V REF1 If the battery voltage V is greater than the threshold voltage V, the output signal S1 is set to a low level. BAT The divided voltage is the first reference voltage V REF1 A hysteresis characteristic may be imparted to the determination as to whether or not the voltage is equal to or lower than the reference voltage. The output signal S1 of the comparator 2 is a mode designation signal that designates the buck mode when at a low level and the buck-boost mode when at a high level. Note that the switching regulator 100 may be configured without the comparator 2 and the voltage-dividing resistors R3 and R4, and may instead receive the mode designation signal from an external device.

[0022] The AND gate 4 outputs a signal S3 which is the logical product of the output signal S1 of the comparator 2 and the pulse signal S2 output from the pulse signal generating circuit 5. The on-duty of the pulse signal S2 output from the pulse signal generating circuit 5 is BAT and output voltage V OUT is a function depending on

[0023] In the step-down mode, the switching regulator 100 controls the on-duty of the MOS transistor Q3 to the battery voltage VBAT and output voltage V OUT Since it is a function according to the battery voltage V BAT and the output voltage V OUT When the values ​​of are close to each other, the step-down ratio in the step-down operation can be prevented from increasing, and as a result, heat generation can be suppressed.

[0024] An output signal S3 of the AND gate 4 is supplied to the gate of the MOS transistor Q3, and is also supplied to the gate of the MOS transistor Q4 after being logically inverted by the NOT gate 6. It is preferable to use a dead time generation circuit instead of the NOT gate 6, and to provide a dead time during which both the MOS transistor Q3 and the MOS transistor Q4 are turned off when the MOS transistors Q3 and Q4 are switched on and off.

[0025] The voltage-dividing resistors R3 and R4, comparator 2, reference voltage source 3, AND gate 4, pulse signal generating circuit 5, and NOT gate 6 described above constitute a control circuit that generates a boost control signal for turning on / off MOS transistors Q3 and Q4 in a complementary manner. The control circuit that generates the boost control signal for turning on / off MOS transistors Q3 and Q4 in a complementary manner is a separate system from error amplifier 11, which will be described later. The control circuit that generates the boost control signal for turning on / off MOS transistors Q3 and Q4 in a complementary manner does not share error amplifier 11 with the control circuit that generates the step-down control signal for turning on / off MOS transistors Q1 and Q2 in a complementary manner. This configuration enables switching regulator 100 to reliably prevent the occurrence of right-half-plane-zero characteristics.

[0026] 2 is a diagram showing an example of the configuration of the step-down control circuit 1. In the example shown in Fig. 2, the step-down control circuit 1 is made up of an error amplifier 11, a reference voltage source 12, a resistor R5, a capacitor C2, a slope circuit 13, a comparator 14, an oscillator 15, and a timing control circuit 16.

[0027] The error amplifier 11 outputs a feedback voltage V FBand the second reference voltage V output from the reference voltage source 12. REF2 The phase of the error signal is compensated by a phase compensation circuit formed by a resistor R5 and a capacitor C2.

[0028] The slope circuit 13 is controlled based on a clock signal of a predetermined frequency output from the oscillator 15, has current information about the inductor L1, and generates and outputs a slope voltage that reflects the current information about the inductor L1. This makes the switching regulator 100 a so-called current-mode control switching regulator. The current information about the inductor L1 can be obtained, for example, by providing a current detection unit (not shown) that detects the current flowing through the MOS transistor Q1, or by providing a current detection unit (not shown) that detects the current flowing through the MOS transistor Q2.

[0029] The comparator 14 generates a reset signal, which is a comparison signal, by comparing the phase-compensated error signal with the output voltage of the slope circuit 13. Since the slope voltage generated by the slope circuit 13 has a fixed period, the reset signal is a PWM signal.

[0030] As described above, the oscillator 15 outputs a clock signal of a predetermined frequency to the slope circuit 13 and also outputs a clock signal of a predetermined frequency to the timing control circuit 16 .

[0031] The timing control circuit 16 switches the gate signal G1 from low level to high level when the set signal switches from high level to low level, and switches the gate signal G1 from high level to low level when the reset signal switches from low level to high level.

[0032] <Operation mode> Battery voltage V BAT The divided voltage is the first reference voltage V REF1 If it is greater than the battery voltage V BAT is greater than a predetermined value A, the switching regulator 100 operates in the step-down mode (see FIG. 3). In the step-down mode, the step-down control circuit 1 controls the feedback voltage V FBSince the output signal S1 of the comparator 2 is at a low level, the MOS transistor Q3 is held in an off state and the MOS transistor Q4 is held in an on state. As a result, the first switch voltage V SW1 and a second switch voltage V, which is the connection node voltage of the MOS transistors Q3 and Q4. SW2 This is shown in FIG.

[0033] The transfer characteristic of the entire switching regulator 100 in the step-down mode is expressed by the following equation (1).

[0034] On the other hand, the battery voltage V BAT The divided voltage is the first reference voltage V REF1 If the battery voltage is V BAT is equal to or less than a predetermined value A, the switching regulator 100 operates in the step-up / step-down mode (see FIG. 3). In the step-up / step-down mode, the step-down control circuit 1 controls the feedback voltage V FB Since the output signal S1 of the comparator 2 is at a high level, the MOS transistors Q3 and Q4 are turned on and off complementarily in a state where the on-duty of the MOS transistor Q3 is fixed to the on-duty of the pulse signal S2 output from the pulse signal generating circuit 5. As a result, the first switch voltage V SW1 and a second switch voltage V, which is the connection node voltage of the MOS transistors Q3 and Q4. SW2 This is shown in FIG.

[0035] In the step-up / step-down mode, the on-duty of the MOS transistor Q3, i.e., the on-duty of the pulse signal S2, is set to the battery voltage V BAT and output voltage V OUT By roughly switching the on-duty of the MOS transistor Q3 as a function according to the above, the on-duty of the MOS transistor Q3 can be regarded as a fixed value. Therefore, the transfer characteristic of the entire switching regulator 100 in the buck-boost mode is expressed by the following equation (2).

[0036] The above-described step-down operation in the step-down mode and the step-up / step-down operation in the step-up / step-down mode result in an output voltage V OUT When the on-duty D of the MOS transistor Q1 is constant, Q1 and the on-duty D of the MOS transistor Q3 Q3 is as shown in FIG.

[0037] In the setting shown in FIG. 6, the battery voltage V BAT and output voltage V OUT When the first relationship is satisfied, that is, when the battery voltage V BAT is in the first range RNG1, the battery voltage V BAT and output voltage V OUT When the second relationship is satisfied, that is, when the battery voltage V BAT The on-duty of the MOS transistor Q3 is smaller than when the battery voltage V is in the second range RNG2. BAT and output voltage V OUT In the case where the second relationship is satisfied, the battery voltage V BAT and output voltage V OUT The battery voltage V BAT and the output voltage V OUT The values ​​of and are close to each other.

[0038] By adopting the settings shown in FIG. 6, the switching regulator 100 controls the battery voltage V BAT and the output voltage V OUT When the values ​​of are close to each other, the step-down ratio in the step-down operation can be reliably prevented from becoming large.

[0039] In the setting shown in FIG. 6, the on-duty of the pulse signal S2 output from the pulse signal generating circuit 5 is set to the battery voltage V BAT and output voltage V OUT6, the step function in the step-down mode has only one step, but the step function in the step-down mode may have multiple steps.

[0040] From the above equations (1) and (2), the overall transfer characteristic of the switching regulator 100 in the buck-boost mode is equal to the product of (1-D') and the overall transfer characteristic of the switching regulator 100 in the buck mode. As a result, the response characteristic of the switching regulator 100 in the buck-boost mode is the same as the response characteristic of the switching regulator 100 in the buck mode. Therefore, the transfer function of the switching regulator 100 in the buck-boost mode does not have a right-half-plane-zero characteristic. This eliminates the need to increase the capacitance of the output capacitor C1, thereby reducing the cost of the output capacitor.

[0041] Furthermore, switching regulator 100 does not require separate reactors for the step-up switching regulator section and the step-down switching regulator section, so the cost of the reactors can be reduced.

[0042] Simulation results for the Bode diagram of the switching regulator 100 are shown in Figures 7 and 8. BAT is set to 12 [V], and the output voltage V OUT 8 is a Bode diagram for the case where the battery voltage V BAT is set to 4 [V], and the output voltage V OUT This is a Bode diagram for the buck-boost mode when the voltage is set to 5 V. The control system is stable in both the buck mode and the buck-boost mode.

[0043] <Applications> Next, an application example of the switching regulator 100 described above will be described. FIG. 9 is an external view showing an example configuration of a vehicle equipped with on-board devices. The vehicle X in this configuration example is equipped with on-board devices X11 to X17 and a battery (not shown) that supplies power to these on-board devices X11 to X17. The standard value of the voltage output from the battery is, for example, 48 V.

[0044] The in-vehicle device X11 is an engine control unit that performs engine-related controls (such as injection control, electronic throttle control, idling control, oxygen sensor heater control, and auto-cruise control).

[0045] The in-vehicle device X12 is a lamp control unit that controls the turning on and off of HID (high intensity discharge lamp) and DRL (daytime running lamp).

[0046] The in-vehicle device X13 is a transmission control unit that performs control related to the transmission.

[0047] The in-vehicle device X14 is a body control unit that performs control related to the movement of the vehicle X (ABS (anti-lock brake system) control, EPS (electric power steering) control, electronic suspension control, etc.).

[0048] The in-vehicle device X15 is a security control unit that controls the driving of door locks, anti-burglary alarms, and the like.

[0049] The in-vehicle devices X16 are electronic devices that are installed in the vehicle X at the time of shipping from the factory as standard equipment or manufacturer options, such as wipers, power door mirrors, power windows, a power sunroof, power seats, and an air conditioner.

[0050] The in-vehicle device X17 is an electronic device that is installed in the vehicle X at the user's discretion, such as an in-vehicle A / V (audio / visual) device, a car navigation system, and an ETC (Electronic Toll Collection System).

[0051] The switching regulator 100 described above can be incorporated into any of the in-vehicle devices X11 to X17.

[0052] <Others> In addition to the above-described embodiments, various modifications can be made to the configuration of the present invention without departing from the spirit of the invention. The above-described embodiments are illustrative in all respects and should be considered not to be limiting. The technical scope of the present invention is defined by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope of the claims.

[0053] The switching regulator (100) described above is a switching regulator configured to generate an output voltage from an input voltage, and includes: a first switch (Q1) configured to have a first terminal connectable to a first application terminal to which the input voltage is applied; a second switch (Q2) configured to have a first terminal connectable to a second terminal of the first switch and a second terminal connectable to a second application terminal to which a predetermined voltage lower than the input voltage is applied; an inductor configured to have a first terminal connectable to a connection node between the first switch and the second switch; and a third switch (Q3) configured to have a first terminal connectable to the second terminal of the inductor and a second terminal connectable to the second application terminal. The first configuration has: a fourth switch (Q4) having a first end configured to be connectable to a connection node between the inductor and the third switch and a second end configured to be connectable to a third application end to which the output voltage is applied; a first control circuit (1) configured to generate a step-down control signal for turning on / off the first switch and the second switch complementarily in accordance with the output voltage; and a second control circuit (R3, R4, 2 to 6) configured to set the on-duty of the third switch as a function in accordance with the input voltage and the output voltage in a step-up / step-down mode and generate a step-up control signal for turning on / off the third switch and the fourth switch complementarily.

[0054] In the switching regulator having the first configuration, the on-duty of the third switch is set as a function corresponding to the input voltage and the output voltage, and the on-duty of the third switch is roughly switched so that the on-duty of the third switch can be considered to be a fixed value, thereby preventing the appearance of the right-half-plane-zero characteristic.Furthermore, in the switching regulator having the first configuration, the on-duty of the third switch is set as a function corresponding to the input voltage and the output voltage in the buck-boost mode, so that the step-down ratio in the step-down operation can be prevented from becoming large when the input voltage value and the output voltage value are close to each other, and as a result, heat generation can be suppressed.

[0055] In the switching regulator having the first configuration, the first control circuit may include an error amplifier (11) configured to amplify and output an error between a feedback voltage based on the output voltage and a reference voltage, and the second control circuit may be configured (second configuration) to be a system separate from the error amplifier.

[0056] In the switching regulator having the second configuration, the second control circuit is a separate system from the error amplifier, i.e., the second control circuit does not share the error amplifier in the first control circuit with the first control circuit, so it is possible to reliably prevent the right-half-plane-zero characteristic from appearing.

[0057] In the switching regulator having the first or second configuration, the second control circuit may be configured (third configuration) such that when the input voltage and the output voltage have a first relationship in the step-up / step-down mode, the second control circuit reduces the on-duty of the third switch compared to when the input voltage and the output voltage have a second relationship in the step-up / step-down mode, and when the input voltage and the output voltage have the second relationship, the value of the input voltage and the value of the output voltage are closer to each other in the second relationship than in the first relationship.

[0058] The switching regulator having the third configuration can reliably prevent the step-down ratio in the step-down operation from becoming too large when the input voltage value and the output voltage value are close to each other.

[0059] In the switching regulator having any of the first to third configurations, the function according to the input voltage and the output voltage may be a step function according to the input voltage and the output voltage (fourth configuration).

[0060] The switching regulator having the fourth configuration can reliably and roughly switch the on-duty of the third switch, and therefore can reliably prevent the appearance of the right-half-plane-zero characteristic.

[0061] The above-described in-vehicle devices (X11 to X17) have a configuration (fifth configuration) including a switching regulator having any one of the first to fourth configurations.

[0062] In the in-vehicle device having the fifth configuration, it is possible to prevent the right-half-plane-zero characteristic from appearing in the switching regulator, and also to suppress heat generation in the switching regulator.

[0063] The vehicle (X) described above has a configuration (sixth configuration) including the on-board equipment of the fifth configuration.

[0064] In the vehicle having the sixth configuration, it is possible to prevent the right-half-plane-zero characteristic from appearing in the switching regulator, and it is also possible to suppress heat generation in the switching regulator.

[0065] 1 Step-down control circuit 2, 14 Comparator 3, 12 Reference voltage source 4 AND gate 5 Pulse signal generating circuit 6 NOT gate 11 Error amplifier 13 Slope circuit 15 Oscillator 16 Timing control circuit 100 Switching regulator C1 Output capacitor C2 Capacitor L1 Inductor Q1 to Q4 MOS transistor R0 Output resistor R1 to R4 Voltage dividing resistor R5 Resistor X Vehicle X11 to X17 In-vehicle equipment

Claims

1. 1. A switching regulator configured to generate an output voltage from an input voltage, comprising: A first switch having a first terminal connectable to a first application terminal to which the input voltage is applied; a second switch having a first terminal connectable to a second terminal of the first switch and a second terminal connectable to a second application terminal to which a predetermined voltage lower than the input voltage is applied; an inductor having a first end connectable to a connection node between the first switch and the second switch; a third switch having a first end connected to the second end of the inductor and a second end connected to the second application end; a fourth switch having a first terminal connectable to a connection node between the inductor and the third switch and a second terminal connectable to a third application terminal to which the output voltage is applied; a first control circuit configured to generate a step-down control signal for turning on / off the first switch and the second switch in a complementarily manner in response to the output voltage; a second control circuit configured to generate a boost control signal for setting an on-duty of the third switch as a function according to the input voltage and the output voltage in a boost / buck mode and for turning on / off the third switch and the fourth switch complementarily; A switching regulator having a

2. the first control circuit includes an error amplifier configured to amplify and output an error between a feedback voltage based on the output voltage and a reference voltage; The switching regulator according to claim 1 , wherein the second control circuit is a separate system from the error amplifier.

3. the second control circuit, when in the step-up / step-down mode and the input voltage and the output voltage have a first relationship, reduces an on-duty of the third switch compared to when in the step-up / step-down mode and the input voltage and the output voltage have a second relationship; 2 . The switching regulator according to claim 1 , wherein the second relationship makes the input voltage and the output voltage closer to each other in value than the first relationship.

4. The switching regulator of claim 1 , wherein the function dependent on the input voltage and the output voltage is a step function dependent on the input voltage and the output voltage.

5. An in-vehicle device comprising the switching regulator according to any one of claims 1 to 4.

6. A vehicle comprising the on-board device according to claim 5.