JP2017169417A - Diode rectification switching power supply device, on-vehicle device, and ringing suppression method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a "diode rectification switching power supply device" capable of suppressing occurrence of ringing under low load.SOLUTION: A diode rectification switching power supply device including a DC/DC conversion circuit (30) formed by electrically connecting a switching element SW, a diode D, an inductor Land a capacitor C, and outputting the power supplied from a power supply while performing DC/DC conversion is further provided with a switching control section (32) including a load detector (30, 35, 37) for detecting a low load state where the load current goes below a set threshold, and a switching signal generator (36) for generating a switching signal, where the switching frequency is set higher than that when the threshold is exceeded, upon detection of the load state, and inputting the switching signal to the switching element.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a diode rectification type switching power supply device that DC / DC converts and outputs electric power supplied from a power supply, and an in-vehicle device that employs the diode rectification type switching power supply device as a power supply device that supplies electric power to various vehicle equipment Further, the present invention relates to a ringing suppression method for a diode rectification switching power supply device.

  A switching power supply device is known as a power supply device that outputs DC / DC converted power (see, for example, Patent Document 1 and Patent Document 2). There are a synchronous type and an asynchronous type switching power supply, and there is a diode rectification type switching power supply as an asynchronous switching power supply. The diode rectification type switching power supply device converts DC power supplied from the power source into AC power by the periodic ON-OFF operation of the switching element, and further rectifies and smoothes the DC power by using diode, inductor, and capacitor elements. Convert and output. The diode rectification type switching power supply device has advantages in that the circuit configuration and control are simple and inexpensive compared with the synchronous type.

JP 2002-125362 A JP 2004-328834 A

  In the switching power supply device, when the load decreases, a section where the ripple current of the switch section falls below 0 (zero) mA appears periodically. However, in the diode rectification type, unlike the synchronous type, current flows only in the forward direction of the diode. Therefore, in a section where the ripple current is less than 0 (zero) mA, as shown schematically in FIG. Current does not flow. Therefore, as schematically shown in the figure, ringing is likely to occur in a switching signal (a so-called short rectangular switching waveform) input to the switching element. When ringing occurs, an unintended frequency different from the switching frequency is generated, causing a malfunction such as beat noise.

  For example, an in-vehicle device having a navigation function or the like is designed to be connectable to an external device such as a smartphone or a USB memory via a power line and a data line. Some smartphones require about 2A of current, and while switching power supply devices are designed with high specifications that can handle this, USB memory requires only about 100mA of current. There are also things. Due to such large load fluctuations, the problem of ringing is likely to become obvious.

  As measures for suppressing the occurrence of ringing, it is conceivable to replace the inductor with an inductor having a large inductance value, or to add a resistance element to increase current consumption at low load. However, this increases the performance of the device or increases the number of devices, and in any case, increases the cost of the product. Furthermore, since the power consumption at low loads varies depending on the type and number of devices connected to the power supply, the hardware specifications of the DC / DC conversion circuit are reviewed each time, and the product specifications are standardized (standardization). I can't plan.

  Further, Patent Literature 1 and Patent Literature 2 disclose control at the time of low load of the switching power supply, but no solution to the ringing problem for the diode rectification switching power supply has been studied.

  The present invention has been made in view of such circumstances, and the diode rectification switching power supply device capable of suppressing the occurrence of ringing at a low load, and the diode rectification to a power supply device for supplying power to various vehicle equipment. The present invention provides an in-vehicle device that employs a type switching power supply device and a ringing suppression method for a diode rectification type switching power supply device.

  Furthermore, as another object, a diode rectification type switching power supply device that can suppress the occurrence of ringing without changing the hardware configuration of the DC / DC conversion circuit for variations in the types and number of connected power consuming devices, The present invention provides an in-vehicle device that employs the diode rectification switching power supply device as a power supply device that supplies electric power to various types of vehicle equipment, and a ringing suppression method for the diode rectification switching power supply device.

  A diode rectification type switching power supply device according to the present invention includes a DC / DC conversion circuit formed by electrically connecting a switching element, a diode, an inductor and a capacitor, and DC / DC converts the power supplied from the power supply. In a diode rectification type switching power supply device that outputs a load, a load detector that detects a low load state in which the load current is less than or equal to a set threshold value, and switching when the low load state is detected is greater than in a load state that exceeds the threshold value. A switching control unit including a switching signal generator that generates a switching signal with a frequency set to a high frequency and inputs the switching signal to the switching element may be provided.

  With such a configuration, the load current lower limit value at which ringing does not occur is temporarily lowered, and the width of the vertical amplitude of the ripple current of the switch unit is reduced. Thereby, even in a low load state where the load current is small, it is possible to suppress the ripple current of the switch portion from appearing at a period lower than 0 (zero) mA, and the occurrence of ringing at the time of low load can be suppressed. As the load current, an average load current can be preferably used.

  As described above, the occurrence of ringing is suppressed by controlling the switching frequency according to the load fluctuation without changing or adding an element for suppressing the occurrence of ringing. Accordingly, it is possible to suppress the occurrence of ringing without changing the hardware configuration of the DC / DC conversion circuit even for variations in the type and number of connected power consuming devices.

  In addition, the switching control unit includes information on setting values of at least two stages of switching frequencies and information on the threshold values set between load current lower limit values corresponding to the switching frequencies, and the load current is the threshold value. It is good also as a structure which performs control which raises to the setting value on the high frequency side when it becomes below, and reduces to the setting value on the low frequency side when exceeding the said threshold value.

  By adopting such a configuration, occurrence of ringing at low load can be suppressed, and efficient output with reduced switching loss can be performed at times other than low load (normal load or high load). . Although the switching loss increases as the switching frequency becomes high, the effect on efficiency is small because the load is low. In addition, by setting a threshold value between the lower limit values of the load current corresponding to each of the two stages of frequencies, it is possible to prevent the threshold current from being straddled by the vertical movement of the load current caused by switching the ON and OFF of the switching element. It is possible to prevent erroneous detection of the load state.

  Moreover, it can be set as the structure which sets a switching frequency so that following Numerical formula 3 may be satisfy | filled. Preferably, the duty ratio before the frequency change is maintained, and the switching frequency satisfying the following formula is set.

  With such a configuration, it is possible to lower the load current lower limit value at which ringing does not occur without changing the output voltage. As an example, when the switching frequency is increased five times, the load current lower limit value at which ringing does not occur is 1/5. As a result, it is possible to suppress the load current from falling below a load current lower limit value at which ringing does not occur.

  The load detector includes a current detector that detects a load current value, and compares the load current value detected by the current detector with the threshold value to determine a load state and detect a low load state. The switching signal generator may be configured to execute control for changing a switching frequency.

  With such a configuration, it is possible to execute feedback control based on the monitored actual current value, and it is possible to accurately detect whether or not the load is low and change the switching frequency. As a result, the control of changing the switching waveform to a high frequency when the load is low can be stably performed.

  In addition, the load detector has information on the types of devices that can be connected to the switching power supply and the current consumption values thereof, and calculates the total current consumption values based on the ON-OFF state or connection state of the devices. Then, the load state is determined by comparing the total current consumption value and the threshold value, and when the low load state is detected, the switching signal generator executes control to change the switching frequency.

  With such a configuration, the switching frequency can be changed by feedforward control, and the follow-up time from when the load is actually lowered to when the switching frequency is changed can be shortened. Furthermore, the occurrence of ringing during the transition period when the load is shifted to a low load can be suppressed.

  Furthermore, an in-vehicle device according to the present invention includes a plurality of vehicle devices and / or externally connected devices that operate with electric power, and DC / DC power from a battery to the plurality of vehicle devices and / or externally connected devices. The above-described switching power supply device that is supplied after conversion may be provided.

  By adopting such a configuration, even when the load current decreases due to the ON-OFF state or connection state of the vehicle equipment or external connection equipment, the ripple current of the switch unit is 0 (zero) for the above-described reason. ) It is possible to suppress lower than mA and to prevent ringing from occurring. As a result, it is possible to suppress the occurrence of malfunction events such as beat noise.

  Furthermore, the ringing suppression method for a diode rectification switching power supply according to the present invention includes a DC rectification switching power supply including a DC / DC conversion circuit formed by electrically connecting a switching element, a diode, an inductor, and a capacitor. In this ringing suppression method, a switching signal set to a switching frequency satisfying Equation 4 below can be input to the switching element.

  With such a configuration, occurrence of ringing at a low load can be suppressed. Furthermore, if the maximum frequency value satisfying the mathematical expression is set, switching loss can be minimized.

  According to the present invention, a diode rectification type switching power supply device capable of suppressing the occurrence of ringing at the time of low load, and an in-vehicle device adopting the diode rectification type switching power supply device for a power supply device for supplying power to various vehicle equipment. And a ringing suppression method for a diode rectification switching power supply device.

  Furthermore, for variations in the types and number of connected power consumption devices, diode rectification switching power supply devices that can suppress the occurrence of ringing without changing the hardware configuration of the DC / DC conversion circuit, and various vehicle equipment An in-vehicle device that employs the diode rectification switching power supply device as a power supply device that supplies power and a ringing suppression method for the diode rectification switching power supply device can be implemented.

It is a block diagram which shows the whole structure of the vehicle-mounted apparatus which concerns on embodiment of this invention. It is a circuit diagram of the switching power supply device which supplies electric power to the said vehicle equipment. It is a figure explaining the switching conditions of the load fluctuation | variation and switching frequency of the said switching power supply device. It is process drawing explaining operation | movement of the said switching power supply device. It is a figure explaining the state of a switching waveform and a ripple current when the load of the said switching power supply device will be in a low load state. It is the modification of the circuit diagram of the said switching power supply device It is a figure explaining the state of a switching waveform and a ripple current when ringing generate | occur | produces in the switching power supply device.

  Embodiments of the present invention will be described with reference to the drawings.

  An in-vehicle device provided with a diode rectification type switching power supply according to an embodiment of the present invention is configured as shown in FIG.

  As shown in FIG. 1, the in-vehicle device 1 includes a computer unit (including a CPU) and a processing unit 10 that executes various processes according to a program. The processing unit 10 includes an AV unit group 11 (including a CD / DVD drive, a digital TV, a digital radio, etc.) that outputs digital contents such as video and music, and a navigation unit 12 that performs navigation processing such as vehicle route guidance. It is connected. The processing unit 10 is connected to a speaker 13 that outputs voice, music, and the like. Under the control of the processing unit 10, audio signals and the like from the AV unit group 11 and the navigation unit 12 are output from the speaker 13. Is done. The processing unit 10 further includes a storage unit 14 (for example, a hard disk drive) that stores digital content reproduced by the AV unit group 11 and various information such as map information used for processing in the navigation unit. It is connected.

  The in-vehicle device 1 is configured by an LCD panel, and is configured by a display unit 15 provided on an instrument panel or the like on the front seat side of the vehicle, and a touch panel or the like provided integrally with the display unit 15 (LCD panel). And an operation unit 16. The processing unit 10 executes various processes based on input information in accordance with operations on the operation unit 16 and causes the display unit 15 to display information such as images and images obtained by the various processes.

  Further, a battery 2 as a power source is electrically connected to the in-vehicle device 1 via a switching power source device 3. The switching power supply device 3 is a diode rectification switching power supply device (hereinafter simply referred to as “switching power supply device”). The switching power supply device 3 includes a switching power supply circuit 31 including a DC / DC conversion circuit and a switching controller 32 that controls the switching power supply circuit 31. Although a detailed circuit configuration will be described later, the switching power supply device 3 performs DC / DC conversion of power from the battery 2 by the switching power supply circuit 31 and the switching controller 32 and supplies the converted power to the in-vehicle device 1. Various vehicle equipment such as the AV unit group 11 and the navigation unit 12 are electrically connected to the power supply line 4 from the switching power supply device 3 and are operated by the supplied power. For convenience of explanation, FIG. 1 shows the in-vehicle device 1 and the switching power supply device 3 as separate devices, but they can be configured as an integrated device.

  Furthermore, the in-vehicle device 1 is provided with an interface unit 17 to which the external connection device 5 is detachably connected. The interface unit 17 is provided with a connection end of the data line 41 from the processing unit 10 and the power supply line 4 from the switching power supply 3. The external connection device 5 includes a smartphone, a USB memory, a digital video camera, and the like, and is detachably connected to the interface unit 17 via a cable having a data line 41 and a power line 4. When the external connection device 5 is connected to the interface unit 17, the power from the switching power supply device 3 is energized to the external connection device 5 through the power supply line 4, and processing with the external connection device 5 through the data line 41 is performed. Data transmission with the unit 10 is possible. Note that the battery may be connected for the purpose of charging a battery built in the external connection device 5.

Next, the switching power supply device 3 will be described in detail with reference to FIG. FIG. 2 shows a circuit configuration of the switching power supply device 3. As shown in FIG. 2, the switching power supply device 3 includes a switching power supply circuit 31 that outputs power after DC / DC conversion and a switching controller 32 as a switching control unit. The switching power supply circuit 31 includes a diode rectification type DC / DC conversion circuit formed by electrically connecting a switching element SW ₁ , a diode D ₁ , an inductor L ₁ and a capacitor C ₁ as shown in the figure, and a battery. The power from 2 (V _IN ) is DC / DC converted and output (V _OUT , I _OUT ). The switching element SW ₁ is preferably a transistor, but other elements and switches may be employed. The DC / DC conversion includes a step-down method, a step-up method, a step-up / step-down method, and the following description will be made by taking the step-down method as an example.

The switching controller 32 generates a switching signal (so-called short rectangular switching waveform) for switching the switch ON and OFF so that a predetermined output voltage (V _OUT ) is obtained, and inputs the switching signal to the switching element SW ₁ . Control. The switching controller 32 can be configured by a microcontroller provided with an IC (Integrated Circuit) 33. The switching controller 32 further includes a voltage detector 34 that detects an output voltage value (V _OUT ) of the switching power supply circuit 31, a current detector 35 that detects an output current value (I _OUT ) corresponding to a load current value, and switching As a preferred example of the signal generator, a PWM signal generator 36 (PWM; Pulse Width Modulation) is provided.

An error amplifier can be used as the voltage detector 34, and the difference between the output voltage (V _OUT ) and the reference voltage is detected. A PWM comparator can be used as the PWM signal generator 36. Then, the PWM comparator performs control for generating a switching signal having a pulse width determined by comparing the differential voltage detected by the error amplifier and the triangular wave as voltage stabilization control. Instead of the triangular wave, it may be compared with the ripple current of the switch unit or may be compared with the inductor current.

Furthermore, a current detection circuit, a current sensor, or the like can be used as the current detector 35, and an output current value (I _OUT ) is detected as a load current value used for determining a load state. The switching controller 32 stores information on a threshold (I ₀ ) for distinguishing between a low load state and a normal load state, and information on setting values of each switching frequency at a low load and a normal load, as a memory 37. Have. In addition to the above voltage stabilization control, the switching controller 32 determines the load state by comparing the detected output current value (I _OUT ) with the threshold value (I ₀ ), and determines the switching frequency corresponding to the load state. Controls switching to the set value. That is, in this embodiment, the load detector is comprised by the current detector 35, the memory 37, and IC33.

  On the other hand, a device n (n is 1 or more) for supplying power is electrically connected to the output terminal of the switching power supply circuit 31. In the in-vehicle device 1 in FIG. 1, the device n is various vehicle devices such as the AV unit group 11 and the navigation unit 12 and / or a detachable external connection device 5 (including a smartphone, a USB memory, etc.). The type and number of devices n to be connected can be arbitrarily set.

Furthermore, in the in-vehicle device 1 illustrated in FIG. 1, for example, the current consumption during normal load is 300 mA, the power consumption during low load is 30 mA, and the power consumption during high load (when connected to a smartphone) is 2 A. The components such as elements are selected so that the switching frequency can be set within a range of several tens of kHz to 2 MHz. In this design specification, the “load current lower limit value that does not cause ringing” calculated by the following formula 5 when the switching frequency is 400 kHz at normal load is 140 mA, and the switching frequency is 2 MHz at low load. The “lower limit of load current at which ringing does not occur” calculated by the following mathematical formula 5 was 28 mA. Therefore, as shown in FIG. 3, a threshold value (I ₀ ) is set between load current lower limit values (28 mA to 140 mA) corresponding to each switching frequency (as an example, 85 mA). Note that the setting of the threshold value (I ₀ ) is not limited to one, and the load state is further subdivided, the setting value of the switching frequency is assigned to each load state, and the threshold value (I ₀ ) is set between the load states. You may do it.

Next, the operation of the switching power supply device 3 will be described with reference to FIG. First, when the power source of the in-vehicle device 1 is turned on, as shown in step S1, the switching controller 32 samples the output current value (I _OUT ) detected by the current detector 35 as a load current value, and shows it in step S2. Thus, the output current value (I _OUT ) is compared with the threshold value (I ₀ ). If the output current value (I _OUT ) exceeds the threshold value (I ₀ ), as shown in step S3, it is determined that the current is in the normal load state, and the switching frequency is set to the normal load state (400 kHz in this example). Set to. Then, as shown in step S5, the PWM comparator as the PWM signal generator 36 compares the differential voltage detected by the error amplifier as the voltage detector 34 with the triangular wave (or ripple current or inductor current). A switching signal having the determined pulse width is generated.

On the other hand, if the output current value (I _OUT ) is equal to or less than the threshold value (I ₀ ) as a result of the comparison in step S2, it is determined that the load is low as shown in step S4, and the switching frequency is set to the low load state. To the set value (2 MHz in this example). Then, as shown in step S5, the PWM comparator as the PWM signal generator 36 compares the differential voltage detected by the error amplifier as the voltage detector 34 with the triangular wave (or ripple current or inductor current). A switching signal having the determined pulse width is generated.

  Furthermore, as shown in step S6, if the power source of the vehicle-mounted device 1 is ON, the process returns to the comparison in step S1, and a series of control from step S1 to step S5 is repeated. As a result, a change in load state due to the ON-OFF state of various vehicle devices such as the AV unit group 11 and the navigation unit 12 and the connection state of the external connection device 5 is detected quickly, and switching corresponding to the load state is performed. Change the frequency setting.

By performing the above-described control, the switching frequency at the normal load (400 kHz in this example) is set when both the device 1 and the device 2 are operating, as schematically shown in the circuit configuration diagram of FIG. Switching is controlled by the switching signal. When the device 2 is stopped or the like and the load current is lowered to a threshold value (I ₀ ) or less, switching is controlled by a switching signal set to a switching frequency at low load (2 MHz in this example). When the switching frequency is increased, the “load current lower limit value at which ringing does not occur” temporarily decreases, and the width of the vertical amplitude of the ripple current of the switch portion decreases. According to Equation 5 above, when the switching frequency is increased five times, the “load current lower limit value at which ringing does not occur” becomes 1/5. As a result, it is possible to suppress the occurrence of a period of less than 0 (zero) mA in the ripple current of the switch unit, and it is possible to suppress the occurrence of ringing at a low load.

When the stopped device 2 is activated again and the load current exceeds the threshold value (I ₀ ), switching is controlled by the switching signal returned to the switching frequency at normal load (400 kHz in this example). As a result, an efficient output with reduced switching loss can be performed during normal load. Although the switching loss increases as the switching frequency becomes high, the effect on efficiency is small because the load is low.

  Therefore, according to the in-vehicle device 1 provided with the diode rectifying switching power supply device 3 of the present embodiment, it is possible to suppress the occurrence of ringing at the time of low load. Furthermore, the occurrence of ringing can be suppressed without changing the hardware configuration for variations in the type and number of devices to be connected.

Next, a modification of the switching power supply device 3 will be described with reference to FIG. Instead of using the output current value (I _OUT ) detected by the current detector 35 as the load current, the switching power supply device 3 according to this modification uses the load current calculated by the switching controller 32 by calculation. Since the other configuration is the same as that of the switching power supply device 3 shown in FIG. 2, the detailed description is omitted by giving the same reference numerals.

As shown in FIG. 6, the switching power supply device 3 according to the modification has information on the types of devices n that can be connected and the current consumption values in a memory 38 as a storage unit. Then, the switching controller 32 detects which device n is in the ON state or the connected state, or information on the device n in the ON state or the connected device n from the processing unit 10 of the in-vehicle device 1. Is received, information on the corresponding current consumption value is read from the memory, and the total current consumption value is calculated by calculation. The total consumption current value is used as a load current, and a control for determining a load state by comparing with a threshold value (I _O ) is performed.

In the example of FIG. 6, when both the device 1 and the device 2 are operating, the total current consumption value is calculated to be 300 mA by calculation and exceeds the threshold value (I ₀ ). judge. On the other hand, when only the device 1 is operating, the total current consumption value is calculated to be 30 mA by calculation, and is determined to be in the low load state because it is equal to or less than the threshold value (I ₀ ). Even if it is such a structure, the effect similar to the above-mentioned embodiment can be acquired. Furthermore, this modified example also has an advantage that it is possible to employ feedforward control with respect to load fluctuations as a control method.

  As described above, the diode rectification switching power supply device according to the present invention, the in-vehicle device adopting the diode rectification switching power supply device as a power supply device for supplying electric power to various vehicle equipment, and the ringing suppression method of the diode rectification switching power supply device have been described. Since the occurrence of ringing at a low load can be suppressed, it is useful as an apparatus and method that can supply stable power.

DESCRIPTION OF SYMBOLS 1 In-vehicle apparatus 2 Battery 3 Switching power supply device 31 Switching power supply circuit 32 Switching controller 34 Voltage detector 35 PWM signal generator 36 Current detector 4 Power supply line 5 External connection apparatus

Claims (7)

In a diode rectification type switching power supply device that includes a DC / DC conversion circuit formed by electrically connecting a switching element, a diode, an inductor, and a capacitor, and that DC / DC converts and outputs power supplied from a power supply.
A load detector that detects a low load state in which the load current is less than or equal to a set threshold value, and when a low load state is detected, generates a switching signal in which the switching frequency is set to a higher frequency than in a load state that exceeds the threshold value. A diode rectification switching power supply comprising a switching control unit including a switching signal generator for inputting to the switching element.   The switching control unit includes information on setting values of at least two stages of switching frequencies and information on the threshold value set between load current lower limit values corresponding to the switching frequencies, and the load current is less than or equal to the threshold value. 2. The diode rectification switching power supply device according to claim 1, wherein control is performed to increase to a set value on a high frequency side, and to decrease to a set value on a low frequency side when the threshold value is exceeded. 3. The diode rectifying switching power supply device according to claim 1, wherein the switching frequency is set so as to satisfy the following formula 1.

  The load detector includes a current detector that detects a load current value, compares the load current value detected by the current detector with the threshold value, determines a load state, and detects a low load state, the switching The diode rectifier type switching power supply device according to any one of claims 1 to 3, wherein the signal generator executes control to change a switching frequency.   The load detector has information on the type of device that can be connected to the switching power supply and the current consumption value, and calculates the total current consumption value based on the ON-OFF state or connection state of the device, 4. The load state is determined by comparing a total current consumption value and the threshold value, and when the low load state is detected, the switching signal generator executes control to change a switching frequency. The diode rectification type switching power supply device according to claim 1.   A plurality of vehicle devices and / or externally connected devices that operate with electric power, and the power from the battery is supplied to the plurality of vehicle devices and / or externally connected devices by DC / DC conversion. An in-vehicle device comprising: the switching power supply device according to any one of 5 above. A method for suppressing ringing of a diode rectification switching power supply device including a DC / DC conversion circuit formed by electrically connecting a switching element, a diode, an inductor, and a capacitor,
A ringing suppression method for a diode rectification switching power supply, wherein a switching signal set to a switching frequency satisfying the following formula 2 is input to the switching element.

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