WO2021117574A1

WO2021117574A1 - Power supply circuit and control method

Info

Publication number: WO2021117574A1
Application number: PCT/JP2020/044852
Authority: WO
Inventors: 池田　智; 俊也中林
Original assignee: ソニーグループ株式会社
Priority date: 2019-12-12
Filing date: 2020-12-02
Publication date: 2021-06-17

Abstract

This power supply circuit is provided with: a high-side switch and a low-side switch; and a controller for setting a dead time that is a time period during which the high-side switch and the low-side switch are off. The controller sets the dead time corresponding to a mode that is switched in accordance with a load current.

Description

Power supply circuit and control method

This disclosure relates to a power supply circuit and a control method.

In order to reduce the penetration loss of the power supply circuit, specifically the synchronous rectifier circuit, when switching the on / off of the two switching elements, the period during which both switching elements are turned off (hereinafter, appropriately referred to as dead time). The technology to set the circuit has been proposed. (See, for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2009-290812

In such fields, it is desired to reduce the loss in the power supply circuit more efficiently.

One of the purposes of the present disclosure is to provide a power supply circuit and a control method capable of reducing loss more efficiently.

The present disclosure is, for example,
High-side switch and low-side switch,
Equipped with a controller that sets the dead time, which is the period during which the high-side switch and low-side switch are turned off.
The controller is a power supply circuit that sets a dead time corresponding to a mode that switches according to the load current.

The present disclosure is, for example,
The controller sets the dead time, which is the period during which the high-side and low-side switches are off.
A controller is a control method in a power supply circuit that sets a dead time corresponding to a mode that switches according to a load current.

FIG. 1 is a diagram for explaining a configuration example of a power supply circuit according to an embodiment. FIG. 2 is a diagram referred to when a plurality of examples of operation modes of the power supply circuit according to the embodiment are described. 3A and 3B are diagrams that are referred to when a dead time setting example according to the first embodiment is described. FIG. 4 is a diagram referred to when a dead time setting example according to the first embodiment is described. FIG. 5 is a diagram referred to when the first example of the method of detecting the switching between the heavy load mode and the light load mode is described. FIG. 6 is a diagram referred to when a second example of a method of detecting a switch between a heavy load mode and a light load mode is given. FIG. 7 is a diagram referred to when a third example of a method of detecting switching between a heavy load mode and a light load mode is given. FIG. 8 is a diagram referred to when a fourth example of a method of detecting a switch between a heavy load mode and a light load mode is given. FIG. 9 is a diagram referred to when a fifth example of a method of detecting switching between a heavy load mode and a light load mode is given. FIG. 10 is a diagram referred to when a sixth example of a method of detecting switching between a heavy load mode and a light load mode is made. FIG. 11 is a diagram referred to when a seventh example of a method of detecting switching between a heavy load mode and a light load mode is made. FIG. 12 is a diagram that is referred to when the outline of the second embodiment is explained. FIG. 13 is a diagram that is referred to when the outline of the second embodiment is explained. FIG. 14 is a diagram that is referred to when the method of detecting the input voltage in the second embodiment is explained. 15A and 15B are diagrams that will be referred to when the outline of the third embodiment is explained. FIG. 16 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 17 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 18 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 19 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 20 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 21 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described. FIG. 22 is a diagram referred to when the operation of the power supply circuit according to the third embodiment is described.

Hereinafter, embodiments and the like of the present disclosure will be described with reference to the drawings. The explanation will be given in the following order.
<Issues to be considered in this disclosure>
<First Embodiment>
<Second embodiment>
<Third embodiment>
<Modification example>
The embodiments and the like described below are suitable specific examples of the present disclosure, and the contents of the present disclosure are not limited to these embodiments and the like.

<Issues to be considered in this disclosure>
First, in order to facilitate the understanding of the present disclosure, the issues to be considered in the present disclosure will be explained.

As described above, in the field of power supply circuits called DC (Direct Current) -DC converters, synchronous rectifier circuits, etc., it is desired to reduce the loss more efficiently. That is, it is desired to efficiently reduce the loss without adding a new configuration or function to the configuration and function of a general power supply circuit. In the synchronous rectifier circuit described in Patent Document 1 described above, in order to detect the edge of the switching waveform and adjust the dead time continuously in real time, an additional circuit for detecting the edge is required.

Also, in battery-powered products such as cameras, the input voltage to the synchronous rectifier circuit decreases with the use of the camera. It is desirable that the optimum dead time is set as the input voltage decreases.

In the future, as the development of low withstand voltage of next-generation FETs (Field Effect Transistors) such as GaN (gallium nitride) and GaAs (gallium arsenide) progresses mainly for consumer devices, the entire FET will become smaller. As the FET becomes smaller, the parasitic capacitance Coss (the sum of the capacitance between the gate and the source and the capacitance between the drain and the source) increases. On the other hand, in the switching power supply, the parasitic capacitance of the high-side FET and the parasitic capacitance of the low-side FET are constantly repeatedly charged and discharged, and the loss due to this (hereinafter, appropriately referred to as Coss loss) is reduced. It increases as the withstand voltage of the FET decreases and cannot be ignored. Such a Cass loss can be a factor that hinders the improvement of the power conversion efficiency of the power supply circuit using the next-generation FET. The embodiments of the present disclosure made in view of the above viewpoint will be described in detail below.

<First Embodiment>
[Power supply circuit]
(Circuit configuration example)
FIG. 1 is a diagram for explaining a configuration example of a power supply circuit (power supply circuit 1) according to the present embodiment. As the power supply circuit 1 according to the present embodiment, a general power supply circuit configuration and function can be applied.

An input voltage V _in (DC voltage) is supplied to the power supply circuit 1. The input voltage V _in is supplied from a battery, a rectifier circuit that rectifies an AC voltage, or the like. From the positive side of the input voltage V _in is the line L1 is derived, the line from the negative side of the input voltage V _in L2 (ground line) is derived.

The power supply circuit 1 has a high-side switch 11A and a low-side switch 11B connected between the line L1 and the line L2. The high-side switch 11A and the low-side switch 11B are composed of, for example, an N-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Specifically, the drain of the high side switch 11A is connected to the line L1, and the source of the low side switch 11B is connected to the line L2. The high-side switch 11A and the low-side switch 11B are controlled to be complementary, that is, to be alternately turned on at a predetermined frequency so that the upper and lower switching elements are not turned on at the same time. A dead time for a predetermined period is set so that the high side switch 11A and the low side switch 11B are not turned on at the same time.

An inductor and a capacitor are connected to the connection midpoint PA between the high side switch 11A and the low side switch 11B. Specifically, one end of the inductor (L) 12 is connected to the connection midpoint PA, and the capacitor 13 is connected between the other end of the inductor 12 and the line L2. The output of the circuit including the inductor 12 and the capacitor 13 is supplied to the load 2.

Further, the power supply circuit 1 has a controller 101, a driver 102, an input voltage detection circuit 103, a zero cross detection circuit 104, and a feedback circuit 105. The controller 101 controls the power supply circuit 1 in an integrated manner. For example, the controller 101 sets a dead time corresponding to the mode of switching according to the load current, and controls on / off of the high side switch 11A and the low side switch 11B based on the set dead time.

The driver 102 turns on / off the high-side switch 11A and the low-side switch 11B based on the control of the controller 101. The input voltage detection circuit 103 is a circuit that detects a voltage having _{an input voltage of V in.} The zero-cross detection circuit 104 is a circuit that detects zero-cross of a switching current and a switching voltage.

In the feedback circuit 105, the error amplifier 105A in which the negative terminal is connected to the resistor 14, the resistor 15, the connection midpoint PB between the resistor 14 and the resistor 15, and the output of the error amplifier 105A are connected to the negative terminal. It has a comparator 105B. The feedback circuit 105 is a circuit for maintaining the set voltage value constant.

In the feedback circuit 105, the resistor 14 and the resistor 15, dividing the output voltage V _o of the power supply circuit 1. The error amplifier 105A compares the voltage divided by the

resistors

14 and 15 with the reference voltage V _REF, and outputs the difference voltage. The comparator 105B determines the pulse width of PWM (Pulse Width Modulation) control by comparing the differential voltage supplied from the error amplifier 105A with the triangular wave. The determined pulse width is fed back to the controller 101, and the output voltage is controlled by controlling the controller 101 based on the fed-back pulse width.

The configuration of the power supply circuit 1 can be appropriately changed according to the operation mode and the feedback control method described later. For example, in the above description, the voltage mode is used as an example as the feedback control method for stabilizing the output, but the current mode may be applied. In this case, the inductor current (current flowing through the inductor 12) is input to the positive terminal of the comparator 105B instead of the triangular wave.

(action mode)
A plurality of examples of the operation modes of the power supply circuit 1 will be described with reference to FIG. As shown in FIG. 2, as an operation mode for controlling the output voltage, PWM (Pulse Width Modulation) control and PFM (Pulse Frequency Modulation) can be mentioned. PWM is a method in which the switching cycle (frequency) is constant and stabilization is performed by adjusting the duty ratio. Further, the PFM is a method in which the on / off time of the switching element is constant and the frequency is changed. PWM control can be further divided into CCM (Continuous Conduction Mode) and DCM (Discontinuous Conductance Mode). In CCM in the PWM control, it is allowed that the inductor current I _L becomes negative. In DCM in the PWM control, so as to improve efficiency at light loads by preventing the inductor current I _L becomes negative.

In Figure 2, in each operation mode, the switch terminal voltage V _SW is the voltage at the connection point PA, the relationship between the inductor current I _L is shown a current flowing through the inductor 12.

In PWM control, when the load is light, that is, when the load current is small, the inductor current _IL is effective up to the level of zero crossing, so that the frequency of zero crossing increases. In PFM control prevents the inductor current I _L becomes negative, efficiency is improved by skipping clear the pulse both of the FET (high-side switch 11A and the low-side switch 11B) at light loads. Therefore, when the load current becomes small, the pulse is skipped, so that the frequency of occurrence of zero cross is reduced.

A power supply circuit whose operation mode is PFM control generally has a circuit for detecting a switching frequency and a circuit for counting the number of pulses.

The above-mentioned operation mode can be applied as the operation mode of the power supply circuit 1. The general power supply circuit also operates in a mode corresponding to the load current. For example, the power supply circuit has a circuit for detecting switching between a light load mode having a small load current and a heavy load mode having a large load current, and operates according to each mode. Of course, the mode according to the load current is limited to two modes, and may be three or more modes. As shown in FIG. 2, since the zero cross occurrence frequency and the switching frequency change according to the load current, the mode of switching according to the load current can be determined by detecting the zero cross occurrence frequency and the like.

[About dead time setting]
(Overview)
Subsequently, an example of setting the dead time in the first embodiment will be described. The processing shown below is performed by, for example, the controller 101. First, an overview will be given with reference to FIGS. 3A, 3B and 4.

FIG. 3A is a diagram schematically showing the loss when the load is heavy (at the time of heavy load). Further, FIG. 3B is a diagram schematically showing the loss when the load is light (when the load is light). The thickness of the arrow schematically indicates the magnitude of loss or the like.

Input power P _in the output power P _out, through loss P _short, is consumed in the dead time losses P _deadtime. Loss in this case is the sum of the penetration loss P _short and dead time losses P _deadtime. The penetration loss P _short becomes smaller as the dead time t _{dead becomes longer.} Deadtime losses P _deadtime for the duration of the dead time t _dead, since the low-side switch 11B is generated by turning on the reverse direction, the dead time t _dead is longer increases. When the low-side switch 11B is made of GaN, the current flowing when the switch is turned on in the opposite direction is accumulated in the drain-source capacitance.

Generally, the dead time loss P _deadtime is expressed by the following equation 1.
[Equation 1]
P _deadtime = 2 * V _TH * I _o * t _dead * f _sw (W)
However,
V _TH : Reverse ON threshold voltage of low side switch I _o : Load current f _sw : Operating frequency.

At the time of heavy load shown in FIG. 3A, the load current I _o becomes large and the path flowing out to the penetration path, that is, the penetration loss P _short becomes small, while the load current I _o becomes large. _{The dead time} becomes large.

On the other hand, at the time of light load shown in FIG. 3B, the load current I _o becomes small and the path flowing out to the penetration path, that is, the penetration loss P _short becomes large, while the load current I _o is small. The loss P _{dead time} becomes smaller.

That is, through the loss P _short and dead time losses P _deadtime, since the characteristics of the increase or decrease due to the magnitude of the dead time t _dead different, dead time t _dead the sum of the through loss P _short and a dead time losses P _deadtime is minimized Will exist.

Subsequently, with reference to the graph shown in FIG. 4, _{the point that the optimum dead time t dead} changes according to the load current will be described. The horizontal axis of the graph of FIG. 4 _{shows the dead time t dead} , and the vertical axis shows the total loss P _loss (P _deadtime + P _short ).

Line LA in Fig. 4 shows a dead time losses P _deadtime at heavy loads, the line LA 'indicates the dead time losses P _deadtime at light loads. As described above, the dead time losses P _deadtime becomes larger as the dead time t _dead is greater, and the dead time losses P _deadtime at heavy load is greater than the dead time losses P _deadtime at light loads.

The line LB in FIG. 4 _{indicates the penetration loss P short} under heavy load, and the line LB'indicates the penetration loss P _short under light load. As described above, the penetration loss P _short becomes smaller as the dead time t _dead becomes larger, and the penetration loss P _{short under} heavy load is smaller than the penetration loss P _{short at light load.}

The line LC in FIG. 4 shows the _{total loss P loss under heavy load.} The line LC shown by the curve is a combination of the line LA and the line LB. The dead time t _dead corresponding to the minimum point of the line LC, that is, the point where the loss P _loss is the smallest is the optimum dead time under heavy load (dead time t _{dead_best} A in FIG. 4).

Further, the line LC'in FIG. 4 shows the _{total loss P loss at the time of light load.} The line LC'shown by the curve is a combination of the line LA'and the line LB'. The dead time t _dead corresponding to the minimum point of the line LC', that is, the _{place where the loss P loss} is the smallest is the optimum dead time when the load is light (in FIG. 4, the dead time t _{dead_best} B larger than the dead time t _{dead_best} A). ).

In the power supply circuit 1 having a general configuration, for example, it is possible to switch between a heavy load mode corresponding to a heavy load and a light load mode corresponding to a light load. Therefore, in the present embodiment, the dead time corresponding to each mode is set according to the switching of such modes. As a result, the optimum dead time can be set without adding a circuit or the like to the power supply circuit 1 having a general configuration, and the loss in the power supply circuit 1 can be reduced.

[Example of how to detect mode switching]
Subsequently, an example of a method for detecting the switching between the heavy load mode and the light load mode will be described. Switching between the heavy load mode and the light load mode can be detected without adding a new circuit by the configuration of the power supply circuit 1 shown in FIG. 1, in other words, the configuration of the general power supply circuit 1. Can be done.

"First example"
FIG. 5 shows a first example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 5 shows only the configuration related to the first example. In the first example, the zero cross of the switching current (inductor current _IL ) is detected by the zero cross detection circuit 104, and the result is supplied to the controller 101. The controller 101 discriminates between the heavy load mode and the light load mode according to the detection result of the zero cross detection circuit 104, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. Specifically, the controller 101 determines that the heavy load mode is used when the number of zero crosses detected is less than a predetermined value, sets a dead time corresponding to the heavy load mode, and sets a dead time corresponding to the heavy load mode. Determine the light load mode and set the dead time corresponding to the light load mode.

"Second example"
FIG. 6 shows a second example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 6 shows only the configuration related to the second example. In the second example, _{the zero cross of the switching voltage V sw} is detected by the zero cross detection circuit 104, and the result is supplied to the controller 101. The controller 101 discriminates between the heavy load mode and the light load mode according to the detection result of the zero cross detection circuit 104, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. Specifically, the controller 101 determines that the heavy load mode is used when the number of zero crosses detected is less than a predetermined value, sets a dead time corresponding to the heavy load mode, and sets a dead time corresponding to the heavy load mode. Determine the light load mode and set the dead time corresponding to the light load mode.

"Third example"
FIG. 7 shows a third example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 7 shows only the configuration related to the third example. The third example is an example assuming a case where the operation mode of the power supply circuit 1 is PFM control. When the operation mode is PFM control, as shown in FIG. 7, the power supply circuit 1 generally has a switching frequency detection circuit 110, and the switching frequency is detected by the switching frequency detection circuit 110. The switching frequency detected by the switching frequency detection circuit 110 is supplied to the controller 101. The controller 101 discriminates between the heavy load mode and the light load mode according to the supplied switching frequency, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. Specifically, the controller 101 determines that the heavy load mode is used when the switching frequency is equal to or higher than a predetermined value, sets a dead time corresponding to the heavy load mode, and sets the dead time corresponding to the heavy load mode when the switching frequency is less than the predetermined value. Determine and set the dead time corresponding to the light load mode.

"Fourth example"
FIG. 8 shows a fourth example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 8 shows only the configuration related to the fourth example. The fourth example is an example assuming a case where the operation mode of the power supply circuit 1 is PFM control. When the operation mode is PFM control, as shown in FIG. 8, the power supply circuit 1 generally has a pulse count circuit 111, and the pulse count circuit 111 detects the number of pulses. The number of pulses detected by the pulse count circuit 111 is supplied to the controller 101. The controller 101 discriminates between the heavy load mode and the light load mode according to the number of supplied pulses, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. Specifically, when the number of pulses is more than a predetermined value, the controller 101 determines that it is a heavy load mode and sets a dead time corresponding to the heavy load mode, and when the number of pulses is less than a predetermined value, it is regarded as a light load mode. Determine and set the dead time corresponding to the light load mode.

"Fifth example"
FIG. 9 shows a fifth example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 9 shows only the configuration related to the fifth example. In a large-scale system, a system configuration corresponding to multiple outputs can be considered by using a plurality of power supply circuits 1 on the premise that the electric powers of the respective supply destinations of the plurality of power supply circuits are correlated with each other. FIG. 9 is an example assuming such a system. In the fifth example, as shown in FIG. 9, information indicating the mode switched according to the load current (mode after switching) is supplied to the controller 101 of the power supply circuit 1 from the other power supply circuit 1A. To. The controller 101 discriminates between the heavy load mode and the light load mode based on the information indicating the supplied mode, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. The power supply circuit 1 may be connected in multiple stages.

"Sixth example"
FIG. 10 shows a sixth example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 10 shows only the configuration related to the sixth example. The sixth example is an example in which the load 2 is a camera. The load current changes according to the shooting mode of the camera. For example, if the shooting mode of the camera is the still image shooting mode, the load current is relatively small, and if the shooting mode is the operation shooting mode or the continuous shooting mode, the load current is large. Therefore, in this example, as shown in FIG. 10, the controller 101 receives the shooting mode of the camera from the camera control circuit 150. Then, the controller 101 discriminates between the heavy load mode and the light load mode based on the shooting mode of the camera, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time.

"7th example"
FIG. 11 shows a seventh example of a method of detecting a switch between a heavy load mode and a light load mode. Note that FIG. 11 shows only the configuration related to the seventh example. The load current changes according to the operation mode of the secondary device as the load 2. For example, when the operation mode of the secondary side device is the standby state where the power consumption is low, the load current is relatively small, and when the operation mode of the secondary side device is the normal operation mode where the power consumption is large, the load current is large. Become. Therefore, in this example, as shown in FIG. 11, the controller 101 receives the operation mode of the secondary side device from the secondary side device. Then, the controller 101 discriminates between the heavy load mode and the light load mode based on the operation mode of the secondary device, and sets the dead time corresponding to the discriminated mode. Switching control is performed based on the set dead time. The controller 101 may read the operation mode of the secondary device.

According to the first embodiment described above, the dead time corresponding to the mode of switching according to the load current is set. As a result, the optimum dead time is set, so that the loss in the power supply circuit can be suppressed as much as possible.
Further, since the power supply circuit having a general configuration can be used in the present disclosure, when high-speed control, addition of a large-scale circuit, and power are not required, and the Coss loss due to the low withstand voltage of the FET in the future cannot be ignored. Also, the loss can be minimized.
Further, since control that does not depend on the semiconductor process is possible, it is possible to minimize the loss not only in GaN but also in devices made of any material such as GaAs.

<Second embodiment>
Subsequently, the second embodiment will be described. The matters described in the first embodiment, such as the configuration of the power supply circuit 1, can be applied to the second embodiment unless otherwise specified. In the second embodiment, a process of setting a dead time according to the input voltage is performed by utilizing the input voltage detection function of a general power supply circuit.

For example, when the input voltage V _in is supplied from the battery, the input voltage V _in fluctuates according to the remaining capacity of the battery. The second embodiment is an embodiment in which a dead time is set according to the magnitude of the _{input voltage V in.}

As shown in FIG. 12, as the input voltage V _in increases, the rising time tr (falling time tf) of the switching waveform becomes long. Therefore, it is necessary to secure a _{dead time t dead} in order to reduce the penetration loss P _short. In other words, when the input voltage V _in is small, it _{is not necessary to reduce the penetration loss P short} , so that the dead time t _dead can be shortened.

In the graph shown in FIG. 13, similarly to FIG. 4, the horizontal axis _{shows the dead time t dead} , and the vertical axis shows the total loss P _loss (P _deadtime + P _short ).

Line LD in FIG. 13 shows the dead time losses P _deadtime. The line LE in FIG. 13 shows _{the penetration loss P short} _{when the input voltage V in} is larger than a predetermined value. The line LE'in FIG. 13 indicates _{the penetration loss P short} _{when the input voltage V in} is less than a predetermined value.

The line LF shown by the curve in FIG. 13 shows the total loss P _loss _{when the input voltage V in} is large. The line LF is a combination of the line LD and the line LE. The dead time t _dead corresponding to the minimum point of the line LF, that is, the point where the loss P _loss is the smallest is the optimum dead time when the input voltage V _in _{is large (dead time t dead_best} C in FIG. 13). ..

Further, the line LF'shown by the curve in FIG. 13 shows the total loss P _loss _{when the input voltage V in} is large. Further, the line LF'is a combination of the line LD and the line LE'. The dead time t _dead corresponding to the minimum point of the line LF', that is, the point where the loss P _loss is the smallest is the optimum dead time when the input voltage V _in _{is small (dead time t dead_best} D in FIG. 13). is there.

As described above, the optimum dead time for minimizing the loss P _loss differs depending on the input voltage V _in. Specifically, the _{smaller the input voltage V in} , the smaller the dead time t _dead . Therefore, in this embodiment, by using the input voltage detection function common power circuit has, the dead time t _dead in response to the detected input voltage V _in is adapted to be set.

FIG. 14 shows an example of a method of detecting the _{input voltage V in.} Note that FIG. 14 shows only the configuration related to this example. The input voltage detection circuit 103 included in the power supply circuit 1 detects the input voltage V _in . _{The input voltage V in} detected by the input voltage detection circuit 103 is supplied to the controller 101. The controller 101 sets a dead time corresponding to the input voltage V _in. Switching control is performed based on the set dead time.

The input voltage V _in may be classified into two patterns, large and small, and the dead time corresponding to each pattern may be set, or the input voltage V _in may be classified into three or more patterns, and the dead time corresponding to each pattern may be set. It may be set.

<Third embodiment>
Subsequently, the third embodiment will be described. The matters described in the first and second embodiments, such as the configuration of the power supply circuit 1, can be applied to the third embodiment unless otherwise specified.

The third embodiment is roughly an embodiment in which the first embodiment and the second embodiment are combined. Specifically, this is an example in which a mode for switching according to the load current and a dead time corresponding to the input voltage are set.

As shown in FIG. 15A, the horizontal axis defines the _{load current I o} and the vertical axis _{defines the input voltage V in.} _{Then, the dead time t dead1} to the dead time t _dead4 are defined according to each of the four patterns of _{the magnitude of the load current I o} corresponding to the heavy load mode and the light load mode and the magnitude of the input voltage V _in.

As described in the first embodiment, the _{larger the load current I o, the} smaller the dead time (see FIG. 4). _Therefore , t dead4> t _dead1 and t _dead3 > t _dead2 hold. Further, since the _{dead time becomes smaller as the input voltage V in} becomes smaller (see FIG. 13), t _dead3 > t _dead4 and t _dead2 > t _dead1 hold.

Therefore, as shown in FIG. 15B, a threshold value I _{th is set} for the load current Io and a threshold value V _th is set for the input voltage V _in , respectively, according to four patterns classified by the _{threshold value I th} and the threshold value V _th. Dead time is set. The controller 101 determines the mode according to the load current, and also refers to the input voltage to select and set the optimum dead time. In the above description, an example of dividing into 4 patterns (4 quadrants) is shown, but it goes without saying that it can be divided into any number of patterns (number of quadrants). Hereinafter, a specific example thereof will be described.

FIG. 16 shows an example in which the first example and the second embodiment described in the first embodiment are combined. Note that FIG. 16 shows only the configuration related to this example. The zero cross of the switching current (inductor current _IL ) is detected by the zero cross detection circuit 104, and the result is supplied to the controller 101. The controller 101 determines either the heavy load mode or the light load mode according to the detection result of the zero cross detection circuit 104. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the number of zero _{crosses and the input voltage V in.} Switching control is performed based on the set dead time.

FIG. 17 shows an example in which the second example described in the first embodiment and the second embodiment are combined. Note that FIG. 17 shows only the configuration related to this example. The zero cross of the switching voltage V _sw is detected by the zero cross detection circuit 104, and the result is supplied to the controller 101. The controller 101 determines either the heavy load mode or the light load mode according to the detection result of the zero cross detection circuit 104. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the number of zero _{crosses and the input voltage V in.} Switching control is performed based on the set dead time.

FIG. 18 shows an example in which the third example and the second embodiment described in the first embodiment are combined. Note that FIG. 18 shows only the configuration related to this example. The switching frequency detected by the switching frequency detection circuit 110 is supplied to the controller 101. The controller 101 determines either the heavy load mode or the light load mode according to the supplied switching frequency. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the switching frequency and the input voltage V _in. Switching control is performed based on the set dead time.

FIG. 19 shows an example in which the fourth example and the second embodiment described in the first embodiment are combined. Note that FIG. 19 shows only the configuration related to this example. The number of pulses is detected by the pulse count circuit 111. The number of pulses detected by the pulse count circuit 111 is supplied to the controller 101. The controller 101 determines either the heavy load mode or the light load mode according to the number of supplied pulses. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the number of pulses and the input voltage V _in. Switching control is performed based on the set dead time.

FIG. 20 shows an example in which the fifth example described in the first embodiment and the second embodiment are combined. Note that FIG. 20 shows only the configuration related to this example. The controller 101 determines either the heavy load mode or the light load mode according to the information indicating the mode supplied from the power supply circuit 1A. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the information indicating the mode and the input voltage V _in. Switching control is performed based on the set dead time.

FIG. 21 shows an example in which the sixth example described in the first embodiment and the second embodiment are combined. Note that FIG. 21 shows only the configuration related to this example. The controller 101 receives the shooting mode of the camera from the camera control circuit 150. Then, the controller 101 determines either the heavy load mode or the light load mode based on the shooting mode of the camera. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the shooting mode of the camera and the input voltage V _in. Switching control is performed based on the set dead time.

FIG. 22 shows an example in which the seventh example described in the first embodiment and the second embodiment are combined. Note that FIG. 22 shows only the configuration related to this example. The controller 101 receives the operation mode of the secondary device from the secondary device. Then, the controller 101 determines either the heavy load mode or the light load mode based on the operation mode of the secondary device. Further, the input voltage detection circuit 103 detects the input voltage V _in and supplies the detection result to the controller 101. The controller 101 sets a dead time of any of dead time t _dead1 to dead time t _dead4 based on the mode determined based on the operation mode of the secondary device and the input voltage V _in. Switching control is performed based on the set dead time. The controller 101 may read the operation mode of the secondary device.

In this embodiment, since the optimum dead time is set in consideration of not only the load current but also the input voltage, the loss can be further reduced. Further, since the loss can be reduced, when the input voltage is supplied from the battery, the continuous operation time of the battery can be lengthened.

<Modification example>
Although the plurality of embodiments of the present disclosure have been specifically described above, the contents of the present disclosure are not limited to the above-described embodiments, and various modifications based on the technical idea of the present disclosure are possible.

The circuit configuration of the power supply circuit, the elements in the circuit, etc. can be changed as appropriate without departing from the gist of the present disclosure. Further, the load of the power supply circuit is not limited to the camera described in the embodiment. Examples of the load include electronic devices such as television receivers and printers. Further, the power supply circuit may be built in the adapter or the like. In addition, a plurality of examples relating to the mode determination method described in the first embodiment may be combined as appropriate.

The configurations, methods, processes, shapes, materials, numerical values, etc. given in the above-described embodiments and modifications are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. Alternatively, it may be replaced with a known one. In addition, the configurations, methods, processes, shapes, materials, numerical values, and the like in the embodiments and modifications can be combined with each other as long as there is no technical contradiction.

It should be noted that the content of the present disclosure is not construed as being limited by the effects exemplified in this specification.

The present disclosure may also adopt the following configuration.
(1)
High-side switch and low-side switch,
A controller for setting a dead time, which is a period during which the high-side switch and the low-side switch are turned off, is provided.
The controller is a power supply circuit that sets the dead time corresponding to a mode in which the controller switches according to a load current.
(2)
The controller sets a first dead time corresponding to the heavy load mode when the mode is the heavy load mode, and corresponds to the light load mode when the mode is the light load mode. The power supply circuit according to (1), wherein a second dead time longer than the first dead time is set.
(3)
The power supply circuit according to (1) or (2), wherein the controller sets the dead time corresponding to the mode determined by detecting the zero cross of the switching current.
(4)
The power supply circuit according to any one of (1) to (3), wherein the controller sets the dead time corresponding to the mode determined by detecting the zero cross of the switching voltage.
(5)
The power supply circuit according to any one of (1) to (4), wherein the controller sets the dead time corresponding to the mode determined by detecting the switching frequency.
(6)
The power supply circuit according to any one of (1) to (5), wherein the controller sets the dead time corresponding to the mode determined by detecting the number of pulses.
(7)
The power supply circuit according to any one of (1) to (6), wherein the controller sets the dead time corresponding to the mode determined based on the information indicating the mode supplied from another power supply circuit. ..
(8)
The power supply circuit according to any one of (1) to (7), wherein the controller sets the dead time corresponding to the mode determined based on the operation mode of the load to which the load current is supplied.
(9)
The power supply circuit according to (8), wherein the operation mode is either a normal operation mode or a standby mode.
(10)
The load to which the load current is supplied is the camera.
The power supply circuit according to any one of (1) to (7), wherein the controller sets the dead time corresponding to the mode determined based on the shooting mode of the camera.
(11)
The power supply circuit according to (1), wherein the controller sets a mode in which the controller switches according to a load current and a dead time corresponding to an input voltage.
(12)
The power supply circuit according to (11), wherein the controller sets a dead time selected from a plurality of dead times defined according to the magnitude relation of the load current and the magnitude relation of the input voltage.
(13)
The controller sets the dead time, which is the period during which the high-side and low-side switches are off.
The controller is a control method in a power supply circuit that sets the dead time corresponding to a mode in which the controller switches according to a load current.

1 ... Power supply circuit 2 ... Load 11A ... High side switch 11B ... Low side switch 101 ... Controller 103 ... Input voltage detection circuit 104 ... Zero cross detection circuit 105 ... Feedback circuit

Claims

High-side switch and low-side switch,
A controller for setting a dead time, which is a period during which the high-side switch and the low-side switch are turned off, is provided.
The controller is a power supply circuit that sets the dead time corresponding to a mode in which the controller switches according to a load current.
The controller sets a first dead time corresponding to the heavy load mode when the mode is the heavy load mode, and corresponds to the light load mode when the mode is the light load mode. The power supply circuit according to claim 1, wherein a second dead time longer than the first dead time is set.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined by detecting the zero cross of the switching current.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined by detecting the zero cross of the switching voltage.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined by detecting the switching frequency.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined by detecting the number of pulses.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined based on the information indicating the mode supplied from another power supply circuit.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined based on the operation mode of the load to which the load current is supplied.
The power supply circuit according to claim 8, wherein the operation mode is either a normal operation mode or a standby mode.
The load to which the load current is supplied is the camera.
The power supply circuit according to claim 1, wherein the controller sets the dead time corresponding to the mode determined based on the shooting mode of the camera.
The power supply circuit according to claim 1, wherein the controller sets a mode in which the controller switches according to a load current and a dead time corresponding to an input voltage.
The power supply circuit according to claim 11, wherein the controller sets a dead time selected from a plurality of dead times defined according to the magnitude relation of the load current and the magnitude relation of the input voltage.
The controller sets the dead time, which is the period during which the high-side and low-side switches are off.
The controller is a control method in a power supply circuit that sets the dead time corresponding to a mode in which the controller switches according to a load current.