Switch control device, switching power supply device, in-vehicle equipment, and vehicle

Abstract

This switch control device comprises: a sample and hold circuit configured to sample and hold information about a current flowing in a first switch as a high-side switch when the first switch is on, in n cycles within m cycles which are the most recent switching cycles in the past (here, n is a natural number equal to or less than m); and a control circuit configured to control the first switch and a second switch as a low-side switch, on the basis of the information sampled and held by the sample and hold circuit, in the most recent switching cycle.

Description

Switch control device, switching power supply device, in-vehicle device, and vehicle

[0001] The invention disclosed in this specification relates to a switch control device, a switching power supply device, an in-vehicle device, and a vehicle.

[0002] The switching power supply device disclosed in Patent Document 1 is capable of current feedback both when the ratio of the output voltage to the input voltage is small and when the ratio of the output voltage to the input voltage is large.

[0003] JP 2016-67113 A

[0004] [Summary] However, the switching power supply device disclosed in Patent Document 1 is configured to require two current detection circuits, and is configured to switch the current feedback path depending on whether the ratio of the output voltage to the input voltage is small or large.

[0005] The switch control device disclosed in this specification is configured to control on / off of a first switch, the first terminal of which is configured to be connectable to an input voltage application terminal and the second terminal of which is configured to be connectable to a first terminal of an inductor, and on / off of a second switch, the second terminal of which is configured to be connectable to the first terminal of the inductor and the second terminal of the first switch, and the second terminal of which is connectable to an application terminal of a low voltage lower than the input voltage. The switch control device includes: a sample-and-hold circuit configured to sample and hold information about a current flowing through the first switch when the first switch is on in n cycles (where n is a natural number equal to or less than m) out of m most recent switching cycles in the past; and a control circuit configured to control the first switch and the second switch based on the information sampled and held by the sample-and-hold circuit in the most recent switching cycle.

[0006] The switching power supply device disclosed in this specification includes the switch control device configured as described above, the first switch, the second switch, and the inductor.

[0007] The in-vehicle equipment disclosed in this specification includes a switch control device having the above-described configuration or a switching power supply device having the above-described configuration.

[0008] The vehicle disclosed in this specification has the on-board equipment configured as described above.

[0009] Fig. 1 is a diagram showing the configuration of a switching power supply device according to an embodiment. Fig. 2 is a diagram showing an example configuration of a switch control device. Fig. 3 is a timing chart showing the sample-and-hold timing of a sample-and-hold circuit. Fig. 4 is a diagram showing a range in which current feedback is possible. Fig. 5 is an external view showing an example configuration of a vehicle.

[0010] [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.

[0011] 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.

[0012] <Switching power supply device according to an embodiment> Figure 1 is a diagram showing the configuration of a switching power supply device according to an embodiment. Switching power supply device 1 is a switching power supply device that steps down an input voltage VIN to an output voltage VOUT. Switching power supply device 1 has a switch control device 2, a first switch SW1, a second switch SW2, an inductor L1, an output capacitor C1, and a feedback section FB1. Switching power supply device 1 may be configured to operate in a continuous current mode under light load, or may be configured to have a backflow prevention function and operate in a discontinuous current mode under light load.

[0013] The switch control device 2 controls the on / off of the first switch SW1 and the second switch SW2. More specifically, the switch control device 2 controls the on / off of the first switch SW1 and the second switch SW2 based on the output of the feedback unit FB1 and a voltage VSNS that corresponds to the current that flows through the first switch SW1 when the first switch SW1 is on.

[0014] The switch control device 2 is, for example, a semiconductor integrated circuit device including a silicon chip. When the switch control device 2 is a semiconductor integrated circuit device including a silicon chip, the cost of the switch control device 2 can be reduced.

[0015] The first switch SW1 has a first terminal connectable to the application terminal of the input voltage VIN and a second terminal connectable to the first terminal of the inductor L1. The first switch SW1 conducts / cuts off a current path from the application terminal of the input voltage VIN to the inductor L1. For example, a P-channel MOS transistor, an N-channel MOS transistor, or the like can be used as the first switch SW1. For example, if an N-channel MOS transistor is used as the first switch SW1, a bootstrap circuit or the like can be provided in the switching power supply device 1 to generate a voltage higher than the input voltage VIN.

[0016] The second switch SW2 has a first end connectable to the first end of the inductor L1 and the second end of the first switch SW1, and a second end connectable to a terminal to which a ground potential is applied. The second switch SW2 conducts / cuts off a current path from the terminal to which the ground potential is applied to the inductor L1. For example, an N-channel MOS transistor or the like can be used as the second switch SW2. Note that, as a modification of this embodiment, the second end of the second switch SW2 may be configured to be connectable to a terminal to which a low voltage other than the ground potential is applied that is lower than the input voltage VIN.

[0017] The second switch SW2 may be a diode. When the second switch SW2 is a diode, the switch control device 2 controls the bias voltage applied to the second switch SW2 (diode) by controlling the on / off of the first switch SW1. Because the on / off of the second switch SW2 (diode) is determined by the bias voltage applied to the second switch SW2 (diode), the switch control device 2 indirectly controls the on / off of the second switch SW2 (diode).

[0018] For example, at least one of the first switch SW1 and the second switch SW2 is a GaN semiconductor element. When at least one of the first switch SW1 and the second switch SW2 is a GaN semiconductor element, the capacitance of the GaN semiconductor element itself is light, so that when the first switch SW1 is turned on and off, the period of ringing that occurs in the current flowing through the inductor L1 (inductor current IL) becomes shorter, and the time required for the ringing to converge becomes shorter. Therefore, when at least one of the first switch SW1 and the second switch SW2 is a GaN semiconductor element, current feedback is possible even if the ratio of the output voltage to the input voltage is small.

[0019] By switching the first switch SW1 and the second switch SW2, a pulsed switch voltage VSW is generated at the connection node between the first switch SW1 and the second switch SW2. The inductor L1 and the output capacitor COUT smooth the pulsed switch voltage VSW to generate an output voltage VOUT, which is supplied to an application terminal for the output voltage VOUT. A load LD1 is connected to the application terminal for the output voltage VOUT, and the output voltage VOUT is supplied to the load LD1.

[0020] The feedback unit FB1 generates and outputs a feedback voltage VFB corresponding to the output voltage VOUT. The feedback unit FB1 may be, for example, a resistor voltage divider circuit that divides the output voltage VOUT using resistors to generate the feedback voltage VFB. Alternatively, for example, the feedback unit FB1 may be configured to acquire the output voltage VOUT and output the output voltage VOUT itself as the feedback voltage VFB.

[0021] Fig. 2 is a diagram showing an example of the configuration of the switch control device 2. The switch control device 2 of the example configuration shown in Fig. 2 includes a sample-and-hold circuit 21, a slope circuit 22, an adder circuit 23, a reference voltage source 24, an error amplifier 25, a comparator 26, an oscillator 27, and a driver 28.

[0022] The sample-and-hold circuit 21 samples and holds information about the current flowing through the first switch SW1 when the first switch SW1 is on for n cycles (where n is a natural number equal to or less than m) out of m cycles that are the most recent past switching cycles. For example, when m = n = 1, the sample-and-hold circuit 21 samples and holds information about the current flowing through the first switch SW1 when the first switch SW1 is on in the switching cycle one cycle before. The information about the current flowing through the first switch SW1 when the first switch SW1 is on is a voltage VSNS that corresponds to the current flowing through the first switch SW1 when the first switch SW1 is on.

[0023] 3 is a timing chart showing the sample-and-hold timing SHT of the sample-and-hold circuit 21. The sample-and-hold timing SHT of the sample-and-hold circuit 21 occurs after a predetermined time T1 has elapsed since the first switch SW1 was turned on. By setting the predetermined time T1 to be longer than the ringing period of the inductor current IL when the first switch SW1 was turned on, appropriate current feedback is achieved.

[0024] When n is a single number, the sample and hold circuit 21 outputs the sampled and held voltage VSNS as the sample and hold voltage VSH. On the other hand, when n is a multiple number, the sample and hold circuit 21 outputs a voltage corresponding to the sum or average of the n sampled and held voltages VSNS as the sample and hold voltage VSH.

[0025] The method for generating the voltage VSNS is not particularly limited. For example, a current detection resistor may be provided between the application terminal of the input voltage VIN and the first terminal of the first switch SW1, and the potential difference across the current detection resistor may be used as the voltage VSNS. Alternatively, for example, the potential difference across the first switch SW1 may be used as the voltage VSNS. Alternatively, for example, a current detection resistor may be provided between the connection node of the first switch SW1 and the second switch SW2 and the first terminal of the inductor L1, and the potential difference across the current detection resistor may be used as the voltage VSNS.

[0026] The slope circuit 22 generates and outputs a slope voltage VSLP0. The slope voltage VSLP0 is synchronized with a set signal SET and a reset signal RESET, which will be described later. The slope voltage VSLP0 starts to increase proportionally at the falling edge of the set signal SET, ends the proportional increase at the rising edge of the reset signal RESET, and returns to its initial value, where it remains at the initial value until the next falling edge of the set signal SET.

[0027] The adder circuit 23 adds the sample and hold voltage VSH and the slope voltage VSLP0 to generate a slope voltage VSLP1, and supplies the slope voltage VSLP1 to the non-inverting input terminal of the comparator 26.

[0028] The reference voltage source 24 generates a reference voltage VREF and supplies the reference voltage VREF to the non-inverting input terminal of the error amplifier 25 .

[0029] A feedback voltage VFB is supplied to the inverting input terminal of the error amplifier 25. The error amplifier 25 generates an error voltage VERR according to the difference between the feedback voltage VFB and the reference voltage VREF, and supplies the error voltage VERR to the inverting input terminal of the comparator 26.

[0030] The comparator 26 compares the slope voltage VSLP1 with the error voltage VERR to generate a reset signal RESET, which is a comparison signal.

[0031] The oscillator 27 generates a set signal SET, which is a clock signal with a predetermined frequency.

[0032] The driver 28 complementarily turns on / off the first switch SW1 and the second switch SW2 based on a set signal SET and a reset signal RESET. The driver 28 turns on the first switch SW1 and turns off the second switch SW2 at the falling edge of the set signal SET. The driver 28 also turns off the first switch SW1 and turns on the second switch SW2 at the rising edge of the reset signal RESET. When the first switch SW1 and the second switch SW2 are switched on / off, it is preferable to provide a dead time during which both the first switch SW1 and the second switch SW2 are off.

[0033] The reset signal RESET is a signal based on the sample and hold voltage VSH. Therefore, the control circuit controls the first switch SW1 and the second switch SW2 in the latest switching period based on the sample and hold voltage VSH output from the sample and hold circuit 21. The control circuit includes a slope circuit 22, an adder circuit 23, a reference voltage source 24, an error amplifier 25, a comparator 26, an oscillator 27, and a driver 28.

[0034] FIG. 4 is a diagram showing the range in which current feedback is possible when the switching frequency is 2 MHz.

[0035] "Conventional current feedback (high side)" in FIG. 4 shows a case where a current flowing through a high-side switch (a switch corresponding to the first switch SW1 in the embodiment) is fed back in the switching power supply device disclosed in Patent Document 1.

[0036] In the "conventional current feedback (high side)" design, the ringing period of the inductor current is long, so the minimum on-time of the high-side switch capable of current feedback is about 100 nS. On the other hand, in the "conventional current feedback (high side)" design, the maximum on-time of the high-side switch capable of current feedback is limited by the time required for the slope voltage to be initialized, and is about 420 nS.

[0037] "Conventional current feedback (low side)" in FIG. 4 shows a case where a current flowing through a low-side switch (a switch corresponding to the second switch SW2 in the embodiment) is fed back in the switching power supply device disclosed in Patent Document 1.

[0038] In the "conventional current feedback (low side)" design, the minimum on-time of the high-side switch capable of current feedback is determined by the time required for the slope voltage to be initialized, which is approximately 20 nS. On the other hand, in the "conventional current feedback (low side)" design, the ringing period of the inductor current is long, so the maximum on-time of the high-side switch capable of current feedback is approximately 350 nS.

[0039] The "current feedback of the embodiment" in FIG. 4 employs the first switch SW1 and the second switch SW2 that can shorten the ringing period of the inductor current IL, thereby shortening the minimum on-time of the first switch SW1 that allows current feedback to approximately 30 nS.

[0040] In the "current feedback of the embodiment" in FIG. 4, the maximum on-time of the high-side switch capable of current feedback is determined by the time required for the slope voltage VSLP to be initialized, and is about 420 nS.

[0041] That is, the switch control device 2 used in the embodiment has a simple configuration that does not require two current detection circuits, and is capable of current feedback over a wide range of ratios of output voltage to input voltage.

[0042] <Applications> Next, an application example of the switching power supply device 1 described above will be described. Fig. 5 is an external view showing an example configuration of a vehicle equipped with on-board devices. 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, 48V.

[0043] The in-vehicle device X11 is an engine control unit that performs engine-related controls (injection control, electronic throttle control, idling control, oxygen sensor heater control, auto-cruise control, etc.).

[0044] 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).

[0045] The in-vehicle device X13 is a transmission control unit that performs control related to the transmission.

[0046] 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.).

[0047] The in-vehicle device X15 is a security control unit that controls the driving of door locks, anti-burglary alarms, and the like.

[0048] 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.

[0049] 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).

[0050] The switching power supply unit 1 described above can be incorporated into any of the on-board devices X11 to X17. Furthermore, the application of the switching power supply unit 1 described above is not limited to a power supply mounted on the vehicle X, but may also be a power supply mounted on industrial equipment, for example. When mounted on industrial equipment, the standard value of the input voltage VIN is, for example, 600 V.

[0051] <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.

[0052] The switch control device (2) described above is a switch control device configured to control the on / off of a first switch (SW1), the first end of which is configured to be connectable to an application terminal of an input voltage and the second end of which is configured to be connectable to a first end of an inductor (L1), and the on / off of a second switch (SW2), the first end of which is configured to be connectable to a first end of the inductor and a second end of the first switch, and the second end of which is connectable to an application terminal of a low voltage lower than the input voltage, and has a configuration (first configuration) including: a sample-and-hold circuit (21) configured to sample and hold information about a current flowing through the first switch when the first switch is on in n cycles (where n is a natural number equal to or less than m) out of m cycles that are the most recent past switching cycles; and control circuits (22 to 28) configured to control the first switch and the second switch based on the information sampled and held by the sample-and-hold circuit in the most recent switching cycle.

[0053] The switch control device having the first configuration is used together with a first switch and a second switch that can shorten the ringing period of the inductor current, thereby enabling current feedback over a wide range of ratios of output voltage to input voltage with a simple configuration.

[0054] In the switch control device having the first configuration, the sample-and-hold timing of the sample-and-hold circuit may be a configuration (second configuration) in which the sample-and-hold timing is a predetermined time after the first switch is turned on.

[0055] The switch control device having the second configuration can achieve appropriate current feedback by setting the predetermined time to be longer than the ringing period of the inductor current when the first switch is turned on.

[0056] The switching power supply device (1) described above has a configuration (third configuration) including the switch control device having the first or second configuration, the first switch, the second switch, and the inductor.

[0057] The switching power supply device having the third configuration described above uses a first switch and a second switch that can shorten the ringing period of the inductor current, and thereby enables current feedback over a wide range of ratios of output voltage to input voltage with a switch control device having a simple configuration.

[0058] In the switching power supply device having the third configuration, at least one of the first switch and the second switch may be a GaN semiconductor element (fourth configuration).

[0059] The switching power supply device having the fourth configuration can shorten the ringing period of the inductor current.

[0060] In the switching power supply device having the third or fourth configuration, the switch control device may be configured as a semiconductor integrated circuit device including a silicon chip (fifth configuration).

[0061] The switching power supply device having the fifth configuration can reduce the cost of the switch control device.

[0062] The above-described in-vehicle devices (X11 to X17) have a configuration (sixth configuration) that includes a switching power supply device having any one of the third to fifth configurations.

[0063] In the in-vehicle device having the sixth configuration described above, the first switch and the second switch are used, which can shorten the ringing period of the inductor current, and thus a switch control device with a simple configuration can provide current feedback over a wide range of ratios of output voltage to input voltage.

[0064] The vehicle (X) described above has a configuration (seventh configuration) including the on-board equipment of the sixth configuration.

[0065] In the vehicle having the seventh configuration, the first switch and the second switch are used, which can shorten the ringing period of the inductor current, and thus a switch control device with a simple configuration can provide current feedback over a wide range of ratios of output voltage to input voltage.

[0066] REFERENCE SIGNS LIST 1 Switching power supply device 2 Switch control device 21 Sample and hold circuit 22 Slope circuit 23 Adder circuit 24 Reference voltage source 25 Error amplifier 26 Comparator 27 Oscillator 28 Driver COUT Output capacitor FB1 Feedback section L1 Inductor LD1 Load SW1 First switch SW2 Second switch X Vehicle X11 to X17 In-vehicle equipment

Claims

1. A switch control device configured to control on / off of a first switch, the first terminal of which is configured to be connectable to an application terminal of an input voltage and the second terminal of which is configured to be connectable to a first terminal of an inductor, and on / off of a second switch, the first terminal of which is configured to be connectable to the first terminal of the inductor and a second terminal of the first switch, and the second terminal of which is configured to be connectable to an application terminal of a low voltage lower than the input voltage, a sample-and-hold circuit configured to sample and hold information about a current flowing through the first switch when the first switch is on in n periods (where n is a natural number equal to or less than m) out of m switching periods that are the most recent past switching periods; a control circuit configured to control the first switch and the second switch based on the information sampled and held by the sample-and-hold circuit in the latest switching period; A switch control device having a

2. 2. The switch control device according to claim 1, wherein the sample-and-hold timing of the sample-and-hold circuit is a predetermined time after the first switch is turned on.

3. A switch control device according to claim 1 ; The first switch; The second switch; A switching power supply device comprising the inductor.

4. 4. The switching power supply device according to claim 3, wherein at least one of the first switch and the second switch is a GaN semiconductor element.

5. 5. The switching power supply device according to claim 4, wherein the switch control device is a semiconductor integrated circuit device including a silicon chip.

6. An in-vehicle device comprising the switching power supply device according to any one of claims 3 to 5.

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